# Cavalli Compact Tube Hybrid (CTH) Tube & Tweak thread.



## cfcubed

OK, I've been trying to pawn off the starting of this thread but one can't always pass the buck
	

	
	
		
		

		
			





 And since I've the first working proto PCB CTH (by a few days?) guess it should be me.

 Surely much of what may be posted here will be based on opinion, listening tastes, headphone synergies, source attributes, etc. But some observations could/should carry across these. I'll get this rolling (ha ha) with a few bits that come to mind & that I think transcends the variables above.

*Tubes*
Amperex 6dj8 white label Holland - Lower end & upper ends a bit enhanced, perhaps at some expense of mids. Bugle Boy variant perhaps a bit "better" presentation of these characteristics. Is/was a personal favorite (w/BoM, Sonicap Gen II or Wima coupling caps & D2000s)
Siemens "chrome plate" ECC82/12AU7 (1963) - Bit more refined/balanced presentation, vocals/mids performer. As many tubes do, lends an interesting personality to music... Hard to pin down but enjoyable. Not particularly a bass or top end champ - but this can be a good thing.
Mullard Mullard 6922/E88CC Gold Pin, Sylvania 12BH7A, RCA 12au7a "clear top", Raytheon 5814a - All fine candidates that I need to come back to. My enjoyment of the above 2 or 3 has kept me from rolling these back in. BUT see below WRT coupling caps - I WILL be giving these another shot. 
 You certainly don't need expensive tubes in this amp for it to sound good. Tube trading amongst those w/CTHs would be a fun & inexpensive way to go.
*Coupling Caps*
General - Thinking this design, like some other Cavalli designs, do not need boutique parts to sound good/great. The BoM couplers (@ 75 cents USD?) & minor Wima upgrade caps are fine in this design. *Some builders prefer these to alternatives below, perhaps most will.*
Sonicap Gen IIs - These, which fit reasonably well tombstoned on PCB, I found slighly "sweeter" in the amp. But not enough to go to great lengths to acquire or install them (e.g. only as part of mini GB or other larger order).
Mundorf Supreme Silver/Oil - These huge & expensive caps (Sonic Craft - 20% off) require larger-than-target enclosure. Have only had these in for a couple days but can say most noticeable is the bass enhancement & softening of the highs. Shift is enough that my DT-880s become a better match than the Denon D2000s I primarily use & I'll have to cycle through my tubes to ID a more "balanced" one than those Amperex 6dj8s. 
 If $$ is no object, you've the room, want more bass/softening of highs & want to play around you could try this. Doubt anyone could want more bass out of a tube hybrid than this design w/S+O & those Amperexs... My bet is they would want less. _Edit: Take away shouldn't be that I'm disappointed w/the S+Os.. They do more to the sound than enhance bass & soften treble. They lend a different character to the amp though that I'm interpreting as less crisp/darker than before. Perhaps more like some would like from an amp w/a tube in it _




 O.K. I've started this. There's a huge world of tubes for this amp... My last search of the bay yielded 600+ listings AFAIR. My gut says this design lets tubes "come into their own" by running them closer to spec, using better/lighter loading, etc. than some other designs.


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## SACD-Man

Man, looks awesome!


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## rds

I remember something about stability issues when using the Sonicaps tombstoned. Has that issue been solved?


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## sachu

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I remember something about stability issues when using the Sonicaps tombstoned. Has that issue been solved?_

 

yes it has..certain BOM changes have been made for that.


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## rds

I see, so other component values have been adjusted to maintain stability with the tombstoned Sonicaps?
 I'm probably being really lazy, but could you tell me which parts were adjusted?


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## sachu

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I see, so other component values have been adjusted to maintain stability with the tombstoned Sonicaps?
 I'm probably being really lazy, but could you tell me which parts were adjusted?_

 

Looks like Chris managed to tweak the E12 R4E resistor to work with the boutique capacitors..But I will let the guys who are using such capacitors to chime in. My amp uses BOM components and is not in my hands at the moment. SO I haven't been able to try such tweaks..


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## cfcubed

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I see, so other component values have been adjusted to maintain stability with the tombstoned Sonicaps?
 I'm probably being really lazy, but could you tell me which parts were adjusted?_

 

Yes, in my build (w/100k R14s + R15s, 1.8k R13s) raising R4E to SOHA II's 2k value addressed things. And if this proved not to, raising R1E+R2E toward SOHA II values would in all likelihood do the trick.

 BUT wiatrob & runeight are on the leading edge of this AND think maybe core CTH value adjustments should go in "A Very.." thread. 
 BTW See wiatrob recent post there for pics of the gorgeous black kit build up - I feel offerings are great service to this project & DIY community.

 Want to try to keep this thread to things changing sound, stuff like tubes + caps + perhaps output resistors.

 Will be rolling tubes over the next few days to find better mate for S/Os... But they sure make the amp sound much "heavier" than it is


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## TimJo

Just as a point of reference, my prototype build uses VitQ's as the interstage coupling caps mounted underneath the board, and it has worked w/o changes to other components... 

 I have no doubt things would continue to work making the latest change, but I'm sticking to Alex's sage advice - "Don't mess with anything that is working." 
	

	
	
		
		

		
		
	


	




 I can say that the VitQ's sound really good - although I have nothing to compare them against, in order to say how they affect the sound. If I build a second CTH, I'd go ahead and use WIMA's just to be able to do a comparison using the same tube, and see what I think...

 ~ _One thing to note though for those not familiar with the build yet - VitQ's under the board mean you are not using the 'standard' configuration in the small Hammond case._ ~ 

 I decided to try a different approach with all of the taller components under the board, and the tube fully exposed outside of the case. This raised the difficulty of the build a bit, but I'm quite happy with the results.

 Anyway, I'll be posting a list of tubes I've rolled so far, with some impressions of how they sound with my DT880's. As I go through them again, I'll make sure to plug in my AKG 701's as well...


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## keyid

some brief tube impressions.

 Setup:
 Sony DVP-S7000 -> Tributaries Silver Coax ->
 Zapfiltered Zhoulo 2.5C -> Wired Direct w/ Neotech UPCCC -> CTH Amp w/ stepped pot / wima mk4.

 Tubes (all 12au7 variants)

 Siemens E82CC - very balanced, neutral, good sound stage, alittle sweet with touch of sprinkled highs. Im finding this to be my favorite again. Feeling like the music is much more alive with this tube. Going to get the triple mica version either the ECC802S or the 5814A.

 Amperex 7316 - delicate yet precise. Has really great separation between notes and can almost visual where the instrument are coming from.

 Telefunken smooth plates - very involving, works great with the amp.

 GE 6680 - notes hit with clarity and has upfront vocal sound but background sounds are distinct. The highs still simmer and twinkle. Has my toes tapping.

 GE 5814A Triple mica 1960's - hint of sweet mids, highs have abit of grain but may go away after more use, has a more enveloping sound stage, like notes have reverb and good decay. Great tube with k501 & classical.

 Brimmar 13D5 - very warm, abit muddy compared to above tubes. Every note seems to have emphasis on the lower end. The bass has depth but lost some punch. May clear up with more hours. Vocals are lovely with this tube very intimate.

 RCA 5814 Gray plates - lots of air, decent transparency. Missing the full bodied sound as the tubes above. This used to be pretty good on soha.

 Mullard 4003 - great separation between notes, layered and each has its own place. Good mids but highs seem to be grainy though it may clear up as I havent used this tube in a while.

 RCA 12au7a clear plates - detailed but not sharp. Bass hits hard but quick. Notes seems to be all on a similar level. 

 CBS 12au7 black plates - notes ring with good decay, sounds spacious. Mids are little thick but getting sweeter. Bass reaches down but seems to stay there. 

 Mullard (12au7? writings gone) - has alot and sounds lively more energy then CBS or RCA clear plates, sounds like it has higher gain. 

 tubes I hated with my soha sounds so much better on this amp. 

 Caps:
 default polyester - hard, fast, good space, and detailed (want more smoothness)
 Wima mk10 - too soft lost alot of some pace/detail from above
 Wima mk4 - soft/smooth but more detailed then above, good middle ground.
 Sonicap Gen IIs - initially sounds too slow, then it got more exquisite and also sweeter. But still darker/slower then caps above.
 PIO caps (russian/vitaminq)- too slow and dark, didnt burn them in yet.
 To come: russian teflon ft3 and sprague orange drops.


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## rds

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_BTW See wiatrob recent post there for pics of the gorgeous black kit build up - I feel offerings are great service to this project & DIY community._

 

Absolutely, it is a great service and convinced me that I can't pass on building a CTH. It really looks amazing in that little case with the perforated top.

 Thanks for the info on the caps. I'll back out of this discussion and leave it to people who actually have experience with the amp to comment on tweaks.


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## cfcubed

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_some brief tube impressions._

 

Holy cow! You've been busy there keyid. Thanks!
 Reads like pretty much everything you've rolled tube-wise sounds good
	

	
	
		
		

		
		
	


	




 Obvious I think, but will say it anyway, presentation differences likely/mostly persist across headphone choice but synergies/favorite pairings may emerge on an individual level. E.g. I'll try to stick to one set of cans for comparisons across tubes & coupling caps.

 BTW I _was_ somewhat of a skeptic of boutique cap use but am no longer, at least for those in direct signal path. $30 caps may have advantages over $0.30 ones
	

	
	
		
		

		
		
	


	




 BUT think w/this amp one can be extremely happy w/o having to go there. At the same time tho, some could find fancy pants couplers may propel this amp to an even higher level. 
*But please, recommendation is to get your CTHs built & confirmed working w/BoM/kit parts before rolling things other than tubes
	

	
	
		
		

		
		
	


	


*


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## olblueyez

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_Mullard (12au7? writings gone) - has alot and sounds lively more energy then CBS or RCA clear plates, sounds like it has higher gain._

 

What Mullard? Short Plate. Long plate?

 Longplate Mullards - Boxes on the anode (plates) are taller than they are wide.





 Shortplate Mullards - Boxes on the anode (Plates) are wider than they are tall.


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## keyid

I believe short plate with o getter, had yellow writing, and I should have few more mullards long and short in same condition.


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## olblueyez

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_I believe short plate with o getter, had yellow writing, and I should have few more mullards long and short in same condition._

 

Short plates are nice, they are IMO the very definition of "Tubey" sounding. Thick bass and beautiful mids and slightly rolled off highs. The Long plates will be more like a 7316 with lots of color, not so rolled off at the top and not so heavy at the bottom as compared to the short version.


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## olblueyez

I would recommend someone snap these up. This is good stuff and cheap.

2 X SYLVANIA GOLD BRAND 5814A (=12AU7 ECC82) TUBE! - eBay (item 350176478259 end time Apr-09-09 08:13:41 PDT)


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## tacitapproval

I think we have different definitions of cheap when it comes to tubes.


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## cfcubed

Ha, ha... Yes. It's funny though, I may spend hrs trying to snag a good deal on something on the bay (e.g. saving $10) before going out to a "cheap" $50 dinner w/the family. One I could probably make for $20 at home
	

	
	
		
		

		
		
	


	




 The only "expensive" tubes I think I own are Siemens chrome, BB & a PQ. Paid between $10 & $25 for them. And I'm listening to a $3 6BZ7 in my CTH w/S+Os & loving it


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## zkool448

At times like these, it's not about being cheap... just "frugal"


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## olblueyez

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_I think we have different definitions of cheap when it comes to tubes.
	

	
	
		
		

		
		
	


	


_

 

Thats why you could split it up with someone else.


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## MrSlim

Dammit CF, you keep finding those cheap and nice tubes and then it makes me want to get one just to try it out.

 I can't justify a $20 tube, but a $5 one.. well thats another story..


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## cfcubed

Quote:


  Originally Posted by *MrSlim* /img/forum/go_quote.gif 
_Dammit CF, you keep finding those cheap and nice tubes and then it makes me want to get one just to try it out.
 I can't justify a $20 tube, but a $5 one.. well thats another story.._

 

Hey, I've extras.. Maybe some tube trading can go on in another thread or PM or something.
 Between the tube, headphone & cap variables will take a while to figure out which ones I like. Right now liking most all of them
	

	
	
		
		

		
		
	


	




 Very OT, but I'm going out of town for a week or so & wanted to wish those that celebrate Easter a happy one. Here's something that might cheer you up:



 Every year I look forward to that house setting up the decorations... I just make sure I head over after a nice windy spell


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## keyid

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_I would recommend someone snap these up. This is good stuff and cheap.

2 X SYLVANIA GOLD BRAND 5814A (=12AU7 ECC82) TUBE! - eBay (item 350176478259 end time Apr-09-09 08:13:41 PDT)_

 

sylvania gold pins sound different than non? 
 I have one non-gold 5814a. These usually go for $10.


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## sachu

I have a bunch of 5814As to try out on the amp once I get it back...not to mention a couple more 12BH7s, a 6189, a pair of 6N1P-EVs...

 I really need to get myself an Amperex 6DJ8


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## olblueyez

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_sylvania gold pins sound different than non? 
 I have one non-gold 5814a. These usually go for $10._

 

Cadillac and Chevrolet, the GB's (and they must have the gold pins, some dont and they are different) were made for high end audio applications. If someone buys them I am in for one of them.


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## TimJo

Quote:


  Originally Posted by *MrSlim* /img/forum/go_quote.gif 
_Dammit CF, you keep finding those cheap and nice tubes and then it makes me want to get one just to try it out.

 I can't justify a $20 tube, but a $5 one.. well thats another story.._

 

After spending some time with this amp, I have an easier time justifying a $20 tube than a $20 boutique cap. But that's just me...

 My favorite tube so far cost me $35 and it's worth every penny in my book.


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## olblueyez

I just wanted to say something to the people who are trying to roll tubes on the cheap. I started that way and now I have cheap tubes and expensive tubes, (lots of Tubes). Start with the nice ones. As far as I'm concerned, all the good tubes come from *Germany, England, and Holland*, that is for the 12AU7 variants. Some exceptions are the occasional RCA and the Sylvania GB (Gold Brand) with the gold pins, and yes they must have gold pins. GB's with steel or nickel pins are standard Sylvania's with the Gold Printing (They started passing the cheap ones off as GB when they stopped making the real GB's). So I'm told. 
	

	
	
		
		

		
		
	


	




 Moral to the story, Its better to have a few pricey tubes than a bunch of cheapo's. With the range of different sounds available with the 12AU7 I think its not unreasonable to say the Tube is 100 percent of the quality and the signature you get out of your amp.

 I understand other components affect the sound but when your done building and have started to roll.


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## olblueyez

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_After spending some time with this amp, I have an easier time justifying a $20 tube than a $20 boutique cap. But that's just me...

 My favorite tube so far cost me $35 and it's worth every penny in my book. 
	

	
	
		
		

		
		
	


	


_

 

The difference between a 10 dollar tube and a 50 dollar tube is your amp sounding like a 200 dollar amp or a 600 dollar amp. I like to keep my buys less than 40 bucks and some of those are pairs. In that range you should be able to find some really beautiful tubes.

 I got one in the mail today that is Fing amazing. Its a Philips branded Siemens made in Germany, 6189/E82CC/12AU7. E82CC not ECC82. Search for "E82CC" on Ebay. It has Clairity like an RCA cleartop but its smooth and refined. Bass is nice, good combo of weight and impact.

 Picked it up for 11.50 plus shipping. Just remember, EUROPE.






 I like it so much I'm headed to eBay to put some more on my watch list so I can get another for a spare.


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## olblueyez

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Hey, I've extras.. *Maybe some tube trading can go on in another thread or PM or something.*_

 

Maybe a 12AU7 & Variant Thread for people to post tubes with monetary values so we can PM each other and do some horse trading?


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## sachu

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_I got one in the mail today that is Fing amazing. Its a Philips branded Siemens made in Germany, 6189/E82CC/12AU7. E82CC not ECC82. Search for "E82CC" on Ebay. It has Clairity like an RCA cleartop but its smooth and refined. Bass is nice, good combo of weight and impact.

 Picked it up for 11.50 plus shipping. Just remember, EUROPE.




_

 

hehe..I was bidding on those myself..the exact same ones..
	

	
	
		
		

		
		
	


	




 Looks like prices of thsese are going to rocket with bidding wars on ebay soon


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## olblueyez

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_hehe..I was bidding on those myself..the exact same ones..
	

	
	
		
		

		
		
	


	




*Looks like prices of these are going to rocket with bidding wars on ebay soon*_

 

I never thought of that, you guys should really stick with the cheap'o American tubes!!!!!!! No need wasting money!!!!!


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## sachu

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_I never thought of that, you guys should really stick with the cheap'o American tubes!!!!!!! No need wasting money!!!!! 
	

	
	
		
		

		
			



_

 

Heh..got way too many of those and my tax return just came in..

 AM gunning for a coupleof those 12AU7s hard now !


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## Coreyk78

I'm just waiting for my CTH kit to come in from spruce canyon and I'll start building my amp.

 I found out that a guy I work with is into ham radio stuff and he said he had a whole bunch of old tubes at his house. Well yesterday I was finally able to get over to his place and sort through one of his boxes and found a bunch of goodies for tube rolling. 

 13 - 6CG7
 17 - 12AT7
 5 - 12BH7
 7 - 12AU7
 6 - 12AX7

 The gems of the bunch were 2 mullard 12AU7 and 1 Mullard 12AX7.
 They were mostly unboxed of unknown condition, but the price was right, free!
 I may need to invest in a tube tester one of these days.
 I don't know if the CTH can use a 12AT7, if not they are still useful to me since my SE speaker amp uses a 12AT7 for the input tube. Can the CTH use the 12AX7? the pinout is the same as the 12AU7. 

 Also one of the 12BH7A has gold pins, the brand logo is pretty worn but it looks like a Realistic Lifetime made in Gt Britain.


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## smeggy

holy crap, nice score!!

 let's hope most of them are still in good working order, youll have enough tubes to keep you busy for a very long time


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## sachu

Wow..taht is one nice haul...you are gonna be good to roll for a while now


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## olblueyez

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_I'm just waiting for my CTH kit to come in from spruce canyon and I'll start building my amp.

 I found out that a guy I work with is into ham radio stuff and he said he had a whole bunch of old tubes at his house. Well yesterday I was finally able to get over to his place and sort through one of his boxes and found a bunch of goodies for tube rolling. 

 13 - 6CG7
 17 - 12AT7
 5 - 12BH7
 7 - 12AU7
 6 - 12AX7

 The gems of the bunch were 2 mullard 12AU7 and 1 Mullard 12AX7.
 They were mostly unboxed of unknown condition, but the price was right, free!
 I may need to invest in a tube tester one of these days.
 I don't know if the CTH can use a 12AT7, if not they are still useful to me since my SE speaker amp uses a 12AT7 for the input tube. Can the CTH use the 12AX7? the pinout is the same as the 12AU7. 

 Also one of the 12BH7A has gold pins, the brand logo is pretty worn but it looks like a Realistic Lifetime made in Gt Britain.








_

 

Hopefully one of those mullards is a long plate. That gold pin 12BH7A sounds interesting. Make sure the wife bakes this guy a cake or something.


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## TimJo

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_I may need to invest in a tube tester one of these days._

 

Well if your CTH kit is on the way, you just invested in a pretty good one in my book. 
	

	
	
		
		

		
		
	


	




 Plug it in. If it sounds good - it's a good tube.


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## Forte

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_I'm just waiting for my CTH kit to come in from spruce canyon and I'll start building my amp.

 I found out that a guy I work with is into ham radio stuff and he said he had a whole bunch of old tubes at his house. Well yesterday I was finally able to get over to his place and sort through one of his boxes and found a bunch of goodies for tube rolling. 

 13 - 6CG7
 17 - 12AT7
 5 - 12BH7
 7 - 12AU7
 6 - 12AX7


 I don't know if the CTH can use a 12AT7, if not they are still useful to me since my SE speaker amp uses a 12AT7 for the input tube. Can the CTH use the 12AX7? the pinout is the same as the 12AU7. 

_

 

Nice find.
	

	
	
		
		

		
		
	


	




 Re the 12AT7 & 12AX7, no they will not work in the CTH, several prototypers tried them with no luck. Even if you could get them to work the gain would be far to high anyway.


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## TimJo

I'm listening to _David Crosby - If Only I Could Remember My Name ~ Tamilpais High (At About 3)_ on a 12" 45 through this NOS 6189 from '58 and it sounds pretty fing amazing... Triple mica with black plates and a bit of dust.


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## endless402

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_Cadillac and Chevrolet, the GB's (and they must have the gold pins, some dont and they are different) were made for high end audio applications. If someone buys them I am in for one of them._

 

maybe i'll get it if i end up getting this amp


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## zkool448

Just wanted to say sachu, really appreciate you gathering the russian tubes for us (61NPs) ...a beer awaits if ever you're in Toronto 
	

	
	
		
		

		
		
	


	




 Btw, interested to hear any impressions on these tubes.

 zk


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## tacitapproval

Listening to 6p1n-ev right now. I have four (rocket logos) and have had some stability issues with a couple of them and the e12 circuit, although fine at the moment. They sound quite good. Really nice bass extension. Thick, warmish--maybe a little loss of top treble. I have also noticed that the four seem to have different amounts of gain, if that's possible--although my memory may be suspect on this.


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## adamus

wow, complete opposite to the effect of the 6n1ps in the bijou.


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## tacitapproval

I should add that this is through HD650s, so my results may skew in that direction.


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## keyid

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_I never thought of that, you guys should really stick with the cheap'o American tubes!!!!!!! No need wasting money!!!!! 
	

	
	
		
		

		
		
	


	


_

 

yes pls, and no more talk about e82cc 
	

	
	
		
		

		
		
	


	




. Im trying to get another one as mine has an annoying hum.


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## olblueyez

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_yes pls, and no more talk about e82cc 
	

	
	
		
		

		
		
	


	




. Im trying to get another one as mine has an annoying hum._

 

I will trade you for a pair of RCA black plate 5687's. Telefunken ECC82 Ribbed plate is just as nice if not nicer, easier to find too.


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## keyid

interesting offer can the hum be fixed? yea always wanted to hear the Tele ribbed plates I read its like the smooth plates but with more bite. I took your suggestion tried my Mullard long plates and indeed they are really good. On my soha they sounds ordinary but on the CTH its got a nice sparkle and good details.


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## olblueyez

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_interesting offer can the hum be fixed? yea always wanted to hear the Tele ribbed plates I read its like the smooth plates but with more bite. I took your suggestion tried my Mullard long plates and indeed they are really good. On my soha they sounds ordinary but on the CTH its got a nice sparkle and good details._

 

You could try some rubber tube rings but that will alter the sound of the tube, I would just recommend getting another, if you bought it from eBay,, explain to the seller and see what happens. I have only been burned once like that on eBay. The Tele Ribbed is less 3 dimentional and hits a bit harder and a slight bit softer in the highs.

 I was looking at the equipment in your profile, what is your favorite tube so far and favorite headphone and with that combo what would you want to change about the sound?


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## tacitapproval

One tube I have tried that I haven't seen mentioned anywhere (so I am mentioning it here) is the 6211. I have two labeled IBM but made by GE. They are somewhat microphonic, so maybe not the best examples of these. The sound is interesting, with an emphasized middle and very large soundstage. Not my favorites, but worth checking out.

 I find that I am gravitating back to the 5963, which is what I like best in the SOHA II thus far as well.


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## keyid

I guess my favorite in the current setup is between the siemens e82cc and amprex 7316 (it does changes from music and phones), with hd580/600 and CTH amp. I wire direct from my dac so I tend to use one primary amp at a time.

 What I would like is something that sounds like HE90/HEV 
	

	
	
		
		

		
			





 but realistically more liquid mids, transparent highs, detailed separation, and more soul / prat. A budget stax rig may get me close to HE60/90 but right now im trying to get some RS-1 to get some of the above characteristics and try to bare with the discomfort (had 225's). I may have to change my source but thats probably going to be too costly to bump up from the current setup. Also trying to get some RTF tubes as people say they have some of the above characteristics.


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## Coreyk78

oldblueyz - I checked my mullards against the photos you posted and both of mine are the long plates.


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## olblueyez

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_oldblueyz - I checked my mullards against the photos you posted and both of mine are the long plates._

 

The long plates are kinda like having your cake and eating it too. Telefunken ECC802S (Huge bucks) and the Mullard CV491 (longplate) both have the ability to bridge the gap between having a nice warm (colored) bass and lots of detail without being rolled off at the top. I have not heard the ECC802S Tele but I can tell it is the "Mullard long plate" for Telefunken and they probably sound better based on the prices. Anyway, the long plate mullard has lots of bass and doesnt sacrifice any detail but it also does one more thing. It will give you mids that are amazing, especially for jazz, country, anything where mids are important or anything with vocals. Its kinda like taking the best qualities from 2 or three tubes and blending them properly. Fortunately the LP mullards are easier to come by as singles but im waiting for the day when someone has a ECC802S and goes to sell it not knowing what it is.


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## olblueyez

FYI, nice to have in one place when looking.
 5963=12AU7 Dual Triode
 (5963=computer rated 12AU7)

 6189=12AU7WA Dual Triode
 (ruggedized and inexpensive sub for 12AU7)

 5814 / 5814A / 5814WA (12AU7 Substitute)
 (the 5814A is equivalent to a 12AU7WA, it is ruggedized and redesigned; the filament current
 raised to 175ma per section versus 150ma per section for a 12AU7. 5814A is computer rated, 5814WA is ruggedized)


----------



## Coreyk78

I already have an NOS GE 5963 in my rapidly growing tube inventory, and I just won a pair of Philips JAN 6189W on ebay last night, hehe. I don't have any 5814s yet.


----------



## olblueyez

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_I already have an NOS GE 5963 in my rapidly growing tube inventory, and I just won a pair of Philips JAN 6189W on ebay last night, hehe. I don't have any 5814s yet._

 

Buying tubes is like crack cocaine.


----------



## Trapper32

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_Buying tubes is like crack cocaine._

 

I'd agree but cocaine is less addictive and cheaper..


----------



## rds

I think someone needs to build olblueyez a CTH


----------



## olblueyez

I was just thinking, I have a longplate mullard with the "O" getter and I tried it out for the first time today. Its a little hissy, and I have another that isnt. Would anyone be interestered in having it? You cant hear the hiss at regular listening levels. You guys could even pass it around to see if you may want to persue a good one.

 Funny, I just got 6 5867 RCA black plates tonight, I have the bronze and they are the best driver tubes I have had yet. Once I get these black plates then I will be selling off some of my 12AU7/ECC82 tubes and I thought I would just let you guys have first dibs. I have so many tubes now that I gave up trying to find the best combo, I just swap them out when I want a change.


----------



## olblueyez

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I think someone needs to build olblueyez a CTH_

 

If anyone has one near Wash DC then let me know and we can pop a bunch of tubes in and grade the tubes for eveyone.

 eBay has some RCA 5814 and 5963's up for sale now. My hand is shaking.


----------



## sachu

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_If anyone has one near Wash DC then let me know and we can pop a bunch of tubes in and grade the tubes for eveyone.

 eBay has some RCA 5814 and 5963's up for sale now. My hand is shaking._

 

I can send my second one for you to try out when it is ready next week.


----------



## olblueyez

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I can send my second one for you to try out when it is ready next week._

 

That would be cool but all I can grade it with is my 650's. That amp does well with 650's? or no?


----------



## sachu

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_That would be cool but all I can grade it with is my 650's. That amp does well with 650's? or no?_

 

I should think it will..a few members of the prototyping team have HD580s..so am going to say yes.


----------



## olblueyez

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I should think it will..a few members of the prototyping team have HD580s..so am going to say yes._

 

Kewl


----------



## tacitapproval

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_That would be cool but all I can grade it with is my 650's. That amp does well with 650's? or no?_

 

Absolutely!


----------



## keyid

im near D.C., up in rockville


----------



## keyid

finally got my russian Teflons ft3; these are quite good. They are a bargain on ebay, music seemed to open up more (more space and details), vocals are great very smooth and natural. They are almost the size of the board 
	

	
	
		
		

		
		
	


	




 They sound little slow but I think they need some burn in as others say with these Teflons.


----------



## sachu

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_finally got my russian Teflons ft3; these are quite good. They are a bargain on ebay, music seemed to open up more (more space and details), vocals are great very smooth and natural. They are almost the size of the board 
	

	
	
		
		

		
		
	


	




 They sound little slow but I think they need some burn in as others say with these Teflons._

 

Do you have a couple extra ? I want to try it out...going to install the Dayton's tomorrow.


----------



## Coreyk78

Which teflons did you get? I'm using some .22uF 600V in my Tubelab Simple SE amp and they are quite huge, hehe. They sound fantastic though, the bulk is worth dealing with.


----------



## olblueyez

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_im near D.C., up in rockville_

 

We should hook up and try some different tubes.


----------



## keyid

Sachu - wish I had another pair sorry. Want a pair russian PIO's?

 Coreyk - They are FT3. How long did yours take to burn in? They sound alot better now +4 hours burn in.

 oldblueyez - yes, would like to take a gander at your tube collection. Ill make sure to sew in some hidden pockets 
	

	
	
		
		

		
		
	


	




 Going to have to case this amp soon, already had piece of wire short my regs. With these gigantic caps going have to experiment. Im thinking of having them attached on the sides like a rocket offset with plastic holders. The caps body doesnt like to touch ground (SG).


----------



## olblueyez

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_Sachu - wish I had another pair sorry. Want a pair russian PIO's?

 Coreyk - They are FT3. How long did yours take to burn in? They sound alot better now +4 hours burn in.

 oldblueyez - yes, would like to take a gander at your tube collection. Ill make sure to sew in some hidden pockets 
	

	
	
		
		

		
		
	


	




 Going to have to case this amp soon, already had piece of wire short my regs. With these gigantic caps going have to experiment. Im thinking of having them attached on the sides like a rocket offset with plastic holders. The caps body doesnt like to touch ground (SG)._

 

That is funny and I think you should do it. Maybe you could get a pseudo nose cone by having a pointed volume knob. You can call it "CTH Stage One".


----------



## Coreyk78

I left my amp turned on for about 20 hours straight after I built it and they seemed to really wake up and smooth out, of course thats with ~470v running through them so it might happen a little faster, I can't say I have noticed any other significant changes since that initial burn in time. 

 That amp is easily my favorite speaker amp, I don't know if its really because of the FT-3s in the signal path, or if a single ended tube amp really just sounds that damn good, and I never knew that 10 watts could really get as loud as it does. I did learn that if I leave that amp on for that long it could almost pull double duty as a space heater though, haha, those 6L6GCs really put out some heat.


----------



## olblueyez

Im glad no one took me up on the free Mullard long plate, turns out it just needed some time to burn up some air after 50 years of sitting around, works perfect now.


----------



## uberburger101

This amp looks extremely customizable, though I would probably end up spending more on trying tubes than the amp itself. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_I would recommend someone snap these up. This is good stuff and cheap.

2 X SYLVANIA GOLD BRAND 5814A (=12AU7 ECC82) TUBE! - eBay (item 350176478259 end time Apr-09-09 08:13:41 PDT)_

 

I'm assuming this is the normal price those Sylvania Gold Brand 5814 go for?


----------



## olblueyez

Quote:


  Originally Posted by *uberburger101* /img/forum/go_quote.gif 
_This amp looks extremely customizable, though I would probably end up spending more on trying tubes than the amp itself. 
	

	
	
		
		

		
		
	


	






 I'm assuming this is the normal price those Sylvania Gold Brand 5814 go for?_

 

That is cheap for any GB series Sylvania tubes, especially the units with the gold pins.

 God another one for you guys today: "RCA 5814A" Command, sounds great, closed in compared to the Siemens but they hit hard and voices are sweet as honey and the added weight did not come at the expense of speed like some of the other warm tube out there.


----------



## Forte

Quote:


  Originally Posted by *uberburger101* /img/forum/go_quote.gif 
_This amp looks extremely customizable, though I would probably end up spending more on trying tubes than the amp itself._

 

Yep, Already done that. 
	

	
	
		
		

		
		
	


	




 A new tube is cheaper than buying a new amp though, and each time you get a new tube to try it is like you have a new amp again.


----------



## keyid

I also got some RCA 5814a recently, one is from 1964 other 65. They have Black plate round getter extra mica supports, they adds alot of weight to each note very full bodied. Tube matches well with the teflon caps, as they smoothed alot of the meat behind my previous tubes in exchange for space and details. This tubes brings the weight back.

 Do those GB sylvania's from ebay link triple mica?


----------



## Forte

Often see people referring to plate colour and getter shape, do these have any impact on sound, or are they just different methods of manufacture?


----------



## keyid

my knowledge on them is limited but I assume older the better, D getter is found on older tubes, black plates I find sounds better then gray,


----------



## olblueyez

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_Yep, Already done that. 
	

	
	
		
		

		
			





 A new tube is cheaper than buying a new amp though, and *each time you get a new tube to try it is like you have a new amp again*._

 

I vote this post for quote of the year. People just dont understand how important tube rolling is.


----------



## olblueyez

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_I also got some RCA 5814a recently, one is from 1964 other 65. They have Black plate round getter extra mica supports, they adds alot of weight to each note very full bodied. Tube matches well with the teflon caps, as they smoothed alot of the meat behind my previous tubes in exchange for space and details. This tubes brings the weight back.

 Do those GB sylvania's from ebay link triple mica?_

 

2 mica


----------



## olblueyez

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_my knowledge on them is limited but I assume older the better, D getter is found on older tubes, black plates I find sounds better then gray,_

 

I never concern myself with color or getter style. As long as you have the correct tube and it was made in the proper factory then I would not worry about it.


----------



## uberburger101

Well, I initially asked that question because I accidentally bid on 2 tubes of which I can only use 1. I thought they were a pair of GB Sylvania 5751 but instead it was one Sylvania GB 3 Mica gray plate 5751 and one Sylvania GB 5814A. 
	

	
	
		
		

		
		
	


	




 Should be up for sale here once I get those 2 tubes.


----------



## olblueyez

Quote:


  Originally Posted by *uberburger101* /img/forum/go_quote.gif 
_Well, I initially asked that question because I accidentally bid on 2 tubes of which I can only use 1. I thought they were a pair of GB Sylvania 5751 but instead it was one Sylvania GB 3 Mica gray plate 5751 and one Sylvania GB 5814A. 
	

	
	
		
		

		
		
	


	




 Should be up for sale here once I get those 2 tubes._

 

Dont worry about it, put the other 1 back on eBay if you dont sell it, BUT, the Sylvania you bought is a sweet tube, it walks the fine line between too warm and not. Its got plenty of weight but its not so rolled off in the highs like a lot of the warmer tubes are. You will have fun with that.


----------



## olblueyez

Quote:


  Originally Posted by *uberburger101* /img/forum/go_quote.gif 
_Well, I initially asked that question because I accidentally bid on 2 tubes of which I can only use 1.* I thought they were a pair of GB Sylvania 5751* but instead it was one Sylvania GB 3 Mica gray plate 5751 and one Sylvania GB 5814A. 
	

	
	
		
		

		
		
	


	




 Should be up for sale here once I get those 2 tubes._

 

What will you do with the 5751's? For the CTH you want the 5814A.

5751 is a 12AX7 Variant. *What you want is a 12AU7 or Variant!!!* *12AU7 / 12AU7A / ECC82 / CV4003 / B749 / 5814A / 5693 / E82CC / 7316 / ECC802S*


----------



## uberburger101

I'm getting the MAD Ear+ HD, so I'll need the 5751, not the 5814A. That's what I meant, sorry for the confusion. I'll have to sell the Sylvania GB 5814A. Somehow.


----------



## olblueyez

Quote:


  Originally Posted by *uberburger101* /img/forum/go_quote.gif 
_I'm getting the MAD Ear+ HD, so I'll need the 5751, not the 5814A. That's what I meant, sorry for the confusion. I'll have to sell the Sylvania GB 5814A. Somehow._

 

I get it.


----------



## olblueyez

*12AU7 and 12AU7 Variant Tubes For Sale!!!*

http://www.head-fi.org/forums/f44/tu...8/#post5614946


----------



## cfcubed

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_A new tube is cheaper than buying a new amp though, and each time you get a new tube to try it is like you have a new amp again._

 

YES & for this amp there are a load of them. Perhaps I'll amend the 1st post down the road & try to accumulate tubes + impressions in this amp. Again, there are other factors at play but I *think* a given tube's core influence on music in this amp *may* be able to be identified.

 BTW, as I posted way back, very variable coupling caps do this too... Perhaps to a lesser extent & are way more trouble to fit/change. 
 BTW, I'm pulling the Mundorf S+Os for now as they are too lush/dark/bass-heavy w/all but a couple of my "brightest" tubes for my tastes (w/my fav D2000s, better w/DT-880s tho). Trying Sonicap Gen Is next. But in the end BoM or Wimas or Sonicap Gen IIs may be it.

*olblueyez - Hey, what tubes will you have for those 3 CTH kits* you said you would take
	

	
	
		
		

		
		
	


	




 Don't worry I know it wasn't a firm commitment


----------



## uberburger101

I have NEVER DIYed anything before, would you say this amp is easy to start with? It looks really packed.


----------



## cfcubed

Quote:


  Originally Posted by *uberburger101* /img/forum/go_quote.gif 
_I have NEVER DIYed anything before, would you say this amp is easy to start with? It looks really packed._

 

Would not say easy to start with. Nux(?) seems to have succeeded tho, guess it depends. Here are a couple of my thoughts on this.
 Could be better to get at least one more simple build (cmoy?) under your belt... But you only live once & don't know your risk tolerance (waffle, wiggle, waggle


----------



## lgn

w00t, just picked up a used Sylvania GB 5814A on ebay for $10.


----------



## nux

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Would not say easy to start with. Nux(?) seems to have succeeded tho, guess it depends._

 

Well, it was my first amplifier build, but I do a lot of electronics work, including SMD. I would think this amp is intermediate, you should be pretty decent with a soldering iron before attempting it.


----------



## mypasswordis

I bought a lot of 20 12AU7/A variants awhile back, and I think every single one has a different label. I've got tubes from so many different companies... RCA, Sylvania, Amperex, Matsu****a, GE, etc. Do any of you know any good sites that have good clear pics and descriptions so I can identify exactly what I have?


----------



## keyid

There is this one site but I have forgotten the name at the moment, however if the tube does not have any label it will be hard to discern. There are so many tubes variations between each label, it will be hard to look at pictures to figure what they are. If they have labels brand and tube type you can do a search and they may come up. Buying lots is a good way to find some good tubes. I just got one set with with a raytheon black glass with d getter.


----------



## lgn

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_Short plates are nice, they are IMO the very definition of "Tubey" sounding. Thick bass and beautiful mids and slightly rolled off highs. The Long plates will be more like a 7316 with lots of color, not so rolled off at the top and not so heavy at the bottom as compared to the short version._

 

Thanks for the images! I can't believe i didn't notice them before


----------



## nux

olblueyez, great recommendation with the E82CC Siemens. I just got one in a bunch of a dozen 12AU7/ECC82 tubes on eBay for a bargain, <AU$4 each =D

 It just sounds right.


----------



## olblueyez

Quote:


  Originally Posted by *nux* /img/forum/go_quote.gif 
_olblueyez, great recommendation with the E82CC Siemens. I just got one in a bunch of a dozen 12AU7/ECC82 tubes on eBay for a bargain, <AU$4 each =D

 It just sounds right._

 

I am glad it worked out. Cryoset.com has some Triple Mica 5814A Siemens tubes branded Siemens E82CC for 50 bucks ea. I got a couple of those in addition to the regular E82CC and so I figure Im set for life.


----------



## TimJo

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_I am glad it worked out. Cryoset.com has some Triple Mica 5814A Siemens tubes branded Siemens E82CC for 50 bucks ea. I got a couple of those in addition to the regular E82CC and so I figure Im set for life. 
	

	
	
		
		

		
		
	


	


_

 

So have listened to the one from cyroset yet?


----------



## keyid

my rs-1 fund is getting smaller and smaller...
 When are you getting the 5814a, olblueyez?


----------



## Coreyk78

Too bad I missed out on this deal, I even had it on my watched list, but I was away from ebay determined not to spend money for a little while. Somebody got a great deal though.

GL 5814 12AU7 by General Electric - eBay (item 270372013211 end time Apr-14-09 15:28:46 PDT)


----------



## olblueyez

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Too bad I missed out on this deal, I even had it on my watched list, but I was away from ebay determined not to spend money for a little while. Somebody got a great deal though.

GL 5814 12AU7 by General Electric - eBay (item 270372013211 end time Apr-14-09 15:28:46 PDT)_

 

Those are not the best in the world but at 10 bucks a pop it would have been a great bargain for seller and buyer. I never have tried a 5 star GE. Hummmmmm.


----------



## olblueyez

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_So have listened to the one from cyroset yet?_

 

Yes, they are very nice but I cannot say they sound that much better than the standard run of the mill E82CC so it is probably not worth 100 bucks I spent, HOWEVER, it is a ruggedized tube and will last forever and cryoset matches them for you so if you had a B-52 or some other amp that uses them in pairs then that would be IMO the best buy available unless you wanna try a 350 dollar set of Telefunken ECC802S. I could be totally wrong but it would seem that since both are from Germany maybe they came from the same factory, but I dont know, that is just a guess. Anyway, for you CTH guys, if your not lookin spend 50 per tube just stick with the E82CC, if there is a difference I cant hear it and im usually good at picking that stuff out.


----------



## adamus

just put in an old mullard ecc88...

 very very promising so far!

 great slam, huge bass and the mids are something else..... it appears to have dethroned my old fave the 8416


----------



## smeggy

Mine has developed a wonderful bottom end with plenty of power and depth. Waiting on a Siemens tube to arrive which will hopefully be even better.


----------



## keyid

get E82CC for siemens, i have both E82CC and ECC82 and the E82CC is much better. I hope to get those rebadged Siemens triple mica tomorrow.


----------



## sachu

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_get E82CC for siemens, i have both E82CC and ECC82 and the E82CC is much better. I hope to get those rebadged Siemens triple mica tomorrow._

 

Yep..the E82CC are the ones myself and Smeggy are getting. Cost us about 27$ a pop shipped. Better be worth it.


----------



## smeggy

I'm expecting great awesomeness!


----------



## dBel84

did I forget to make a note of me coming over? really need to update from paper diary to isomething 
	

	
	
		
		

		
		
	


	




..dB


----------



## cfcubed

In case a CTH owner/builder missed this, **if** you are experiencing a bit of hum/noise between tracks, and this annoys you enough, we've found a solution WRT heater-circuit-contributed hum/noise: C3H revision.

 WRT CTH's C4 coupling caps, I've pulled the honking, expensive Mundorf 0.22uf S/Os in favor of Sonicap Gen Is. If anyone wants the pair of S/Os for $36 USD shipped CONUS let me know.... That's about 1/2 of what they cost new to your door. 
*Edit: keyid snatched these up.* He's getting a good deal but I've faaarrrr to much $$ tied up in headamp, projects & parts
	

	
	
		
		

		
		
	


	




 Of course saying this while accumulating materials for a β22 build this fall. Not the only crazy around here tho.

 Although I _may_ find Sonicap Gen Is my overall favorites in this amp, think that std BoM, or WIMA or Sonicap Gen II upgrades may end up best for most.

 Tube-wise, Amperex (Holland) 6DJ8s & Siemens 12au7 chrome plates are still at the top of my heap. They each have *very* different presentation (6DJ8s - punchy/great bass, 12au7 - honest/flatter).

 But I've not heard a tube in the CTH that I don't enjoy, except for perhaps my (inherently?) noisy 6BZ7s.


----------



## adamus

6n6p is really nice.


----------



## keyid

Those caps are mine!

 btw, how did the GenI's change the sound?

  Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_In case a CTH owner/builder missed this, **if** you are experiencing a bit of hum/noise between tracks, and this annoys you enough, we've found a solution WRT heater-circuit-contributed hum/noise: C3H revision.

 WRT CTH's C4 coupling caps, I've pulled the honking, expensive Mundorf 0.22uf S/Os in favor of Sonicap Gen Is. If anyone wants the pair of S/Os for $36 USD shipped CONUS let me know.... That's about 1/2 of what they cost new to your door.

 Although I may find Sonicap Gen Is my overall favorites in this amp, think that std BoM, or WIMA or Sonicap Gen II upgrades may end up best for most.

 Tube-wise, Amperex (Holland) 6DJ8s & Siemens 12au7 chrome plates are still at the top of my heap. They each have *very* different presentation (6DJ8s - punchy/great bass, 12au7 - honest/flatter).

 But I've not heard a tube in the CTH that I don't enjoy, except for perhaps my (inherently?) noisy 6BZ7s._


----------



## cfcubed

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_Those caps are mine!

 btw, how did the GenI's change the sound?_

 

YGPM.

 I've found CTH C4 couplers (all 0.22uF) I've tried to exhibit these attributes to my (tin) ears:
std BoM caps - Good lower-cost, small part. Does not excell on bottom end or detail like others do.
WIMAs - A step up from std BoM parts. Nice all-around performer esp. for the cost & size.
Sonicap Gen IIs - Perhaps the sweet spot in terms of size, cost, detail, range & bottom-end. "Honest" presentation.
Sonicap Gen Is - Will need to listen more to detect "improvement" over Sonicap Gen IIs. Too large for BoM case I believe.
Mundorf S+O - See my posts here. The king of lushness & bottom-end while remaining "true". The lushness / bass performance may give the impression of less detail if used with tubes that do not excel in detail OR w/cans that do not excel in detail. Not preferable for me w/Amperex (holland) 6DJ8s + D2000s which are already bass-heavy IMO. But nice w/less punchy tubes & my secondary DT-880s.
Just a couple months ago I was poo-pooing caps > a USD or two. While I may still not have the greatest "pallet" when it comes to accessing SQ, trying these caps in the CTH has opened my eyes.

 As opinioned around here, (most?) Cavalli designs do not require fancy-pants caps to sound very good. But they do not hurt either


----------



## holland

I'm partial to 6CG7.


----------



## keyid

I got cfc's Mcap Silver / Oil yesterday and im really loving them. They blow away all the caps I have tried on the CTH amp, among them the Teflon FT3, genII, PIO and wimas. With siemens 5814a, the bass has become solid and the highs have a pleasant simmering lasting quality. The sound has many trackable layers with good separation reminding of the Eddie Current EC/SS. These caps have marvelous decay and sound very detailed yet relaxed. My other 12au7 tubes sound different with these caps and enjoying rolling them in again. 

 Talking with cfc's I suggested he switch source from his ipod to a cdp. I think a higher end cdp source will improve the sound with the CTH and perhaps help hear more differences with caps. I found even switching to a better transport help on the CTH.

 going to have to thank cfc again for awesome price!


----------



## adamus

A few listening impressions

*amperex PQ, white label shiled logo. *
 On the warm side, big sound, lovely fluid mids and very clear highs. Bass is a slightly lacking definition. 8/10

*6n6p*
 this tube is so tight. Everything is where it should be. Deep bass, but so well controlled, highs extend, mids are there in spades. It just seems..... right. Maybe for some it doesnt sound 'tubey' enough. That slight bass bloat, that slight midrange bloom isnt there, it just seem transparant. 8/10 

 only trouble is with it is, the 800ma heater draw. 

*Mullard Ecc88*
 TUBEY, lush mid bloom, liquid slightly rolled off highs, slightly floppy bass. Very endearing tube for jazz and female vocals. Noise floor is higher, i gues i just have a slightly noisey tube. 7/10 

*6n1p- EV*
 I like this tube, its as cheap as chips and its lively. sparkling highs, perhaps too much for a bright setup (not for my hd650's though!). Again, the bass isnt quite right when compared to the 6n6p. 8/10.


 Does this mean i stick with 6n6p all the time? no. If i want to listen to feist, or ray lamontagne, maybe even norah jones then the mullard ecc88 sounds superb. R and B, maybe dance, then the 6n1p or 6n6p sound great. 

 what i want to listen to mix of genres? the 8416 is the best of the lot for me. It gives that valve colouration that i get on with but is tight enough to get on with bassy music, and 'tubey enough to give vocals that extra magic. Its my best all rounder. 


 I also have an RCA 5814a on the way (i paid a massive 99p for it on ebay!)


----------



## holland

adamus, wondering if you've tried the 6N6P-i and if you hear any differences with the 6N6P.


----------



## keyid

thinking the same with the 6n6p & i, I think wiatrob has some.


----------



## adamus

6n6p is very good, and again, so so cheap it would be rude not to try one. 

 I havent tried the i version, but most reports say they dont sound much different.


----------



## holland

Thanks. I have both 6n6p and 6n6p-i, but I haven't done the due diligence of comparison. 6n6p-i can't run on CTH without mods, it's a 900mA heater and the stock config can only handle up to 800mA (according to part specs)...(wink wink, try it, it may still work, but don't blame me if something fries particularly the big coil).

 I fully intend to give it a go around with my Bijou though as it can handle the heater loads without any problems. The Bijou is really starting to form and is sounding quite nicely now with 6N1P and 6N6P-i.


----------



## smeggy

Ok, I'm gonna buy a 6n6p to try, what is the recommended cap upgrade and where does it go. Sachu made mine so I'm not overly familiar with the circuit but I'm happy to swap it out. I'm not using the standard case so cap size isn't a consideration. I want it to be as good as it can get within my limited capabilities.


----------



## holland

looking at the board, top down. DC to the right. knob to the right. Look at the right edge of the board, towards the upper side. Find the regulator, only other TO-220 device there other than the 24V reg. The 24V reg will be heatsinked. The switcher usually isn't. Next to the switcher is a big tombstoned diode. Next to that is a 47uF/50V cap. It sits between the diode and the switcher, in a right angle formation.

 Replace it with this.

UPW1H331MPD

 If you've got room (and it looks like you do), replace it with this.

UPW1H331MPD6

 or 

http://search.digikey.com/scripts/Dk...name=P12399-ND

 Note the cap dimensions.

 Edit:

http://www.head-fi.org/forums/f6/ver...ml#post5683303


----------



## Ynis Avalach

Don't you have to change the coils aswell? Or are these still ok for the 6n6p's current draw? Planning on doing the same thing
 Ava


----------



## cfcubed

Quote:


  Originally Posted by *Ynis Avalach* /img/forum/go_quote.gif 
_Don't you have to change the coils as well? Or are these still ok for the 6n6p's current draw? Planning on doing the same thing
 Ava_

 

holland had this to say. 

 I'm conflicted about pushing higher heater loads in the CTH. We've achieved quite a lot in a 3"x5" space. Perhaps as much as feasible in that space for an amp w/its features given single PCB, through-hole, etc. OTOH why not find its limits
	

	
	
		
		

		
			





 With tweaks like holland & others are trying to get heater -> 1A, although perhaps not audible in CTH, I _think_ switchers get a bit "ugly" at or near their rated limits. The LM2595 (1A) does have a 3A cousin - the LM2596. Didn't check pinout & likely requires different values for surrounding components, but something major tweakers (like those that add NOS to their cars
	

	
	
		
		

		
		
	


	




) might want to consider.


----------



## Forte

Quote:


  Originally Posted by *Ynis Avalach* /img/forum/go_quote.gif 
_Don't you have to change the coils aswell? Or are these still ok for the 6n6p's current draw? Planning on doing the same thing
 Ava_

 

I have been using a 6N6P in my CTH regularly with standard coils without any problems.


----------



## Ynis Avalach

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_I have been using a 6N6P in my CTH regularly with standard coils without any problems._

 

Well if there is no need for this,perfect! Thank you! Ava


----------



## Ynis Avalach

Anyway, would a 1.25A toroid be sufficiant for this 1A upgrade? Ava


----------



## MrSlim

So, I get the bad feeling that all these cheap and cheerful tubes are going to go up in price if the CTH catches on, better get them while they are a steal.. 

 Like O'l Blue Eyes said: Tubes are the Crack Cocaine of the HeadFi world..


----------



## olblueyez

I have so much Crack Cocaine that it makes me wanna keep my amp even when I see something id like to try, thus my interest in the CTH. I think I have spend about 600 on tubes so far and all I can use is about 70 dollars worth at one time.


----------



## holland

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_I think switchers get a bit "ugly" at or near their rated limits. The LM2595 (1A) does have a 3A cousin - the LM2596. Didn't check pinout & likely requires different values for surrounding components, but something major tweakers (like those that add NOS to their cars
	

	
	
		
		

		
		
	


	




) might want to consider._

 

Indeed. I will try to find out for sure. The sucker runs hot with the 6N6P-i, for sure. I will likely not use it, due to heat and fall back to 600mA tubes....though wiatrob at one point said his 6H30-DR is his favorite in the CTH. I haven't had the luxury to try that yet.

 speaking of the NOS analogy. SOHA II...my current mod for it (in planning with parts ordered) is a 240V B+. Woo, big step up from the 100V B+ in terms of voltage. Will it sound better? I haven't a clue, but it's fun to get there.

 I can't let all these "stacker" guys have the fun with HV hybrids. 
	

	
	
		
		

		
		
	


	




 Edit: forgot to comment on the LM2596. It should work with the stock values, if drawing the same current loads as stock. @ 3A, I'm sure some caps will pop from the heat on the CTH. 6N6P-i runs hot on my build, just from proximity to the tube.


----------



## dBel84

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_ speaking of the NOS analogy. SOHA II...my current mod for it (in planning with parts ordered) is a 240V B+. Woo, big step up from the 100V B+ in terms of voltage. Will it sound better? I haven't a clue, but it's fun to get there._

 

I run the original preprototypethatfailedtobeprototyped soha ii at 200V, not necessary but i could so i did , not convinced it sounds any better than it did at 90V. Do let us know if you feel it makes a difference. 

  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I can't let all these "stacker" guys have the fun with HV hybrids. 
	

	
	
		
		

		
		
	


	


_

 

 tut tut 
	

	
	
		
		

		
		
	


	




 i guess i am threadjacking again - need to build a CTH and get in on the fun 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## cfcubed

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_speaking of the NOS analogy. SOHA II...my current mod for it (in planning with parts ordered) is a 240V B+. Woo, big step up from the 100V B+ in terms of voltage. Will it sound better? I haven't a clue, but it's fun to get there._

 

Know what you mean... I didn't use 250v rated caps in the HV CTH PTP proto:



 for nothing
	

	
	
		
		

		
		
	


	




 SRPP came up for a day or so way back when lots of possibilities were flowing. Thinking it needs at least 200v B+. I've not forgotten that


----------



## zkool448

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_I have so much Crack Cocaine that it makes me wanna keep my amp even when I see something id like to try, thus my interest in the CTH. I think I have spend about 600 on tubes so far and all I can use is about 70 dollars worth at one time._

 

I wrote to an eBay seller and found out he lives less than 2 miles away from where I live (a _really bad sign_ for my wallet). We spoke shortly on the phone and gave an impression that he has a large variety of NOS stashed in his basement. In fact, if I needed a specific tube I would have to help go through his bunch, although he has them categorized in size, no. pins, p/n, etc.

 Since I’m not familiar with tube brands/models and their variants (let alone their sound quality), I wonder if I can get some help in spotting a few decent (better than average) tubes just by looking at his short listing. He mentions if the tubes I needed do not appear in his store list doesn’t mean he doesn’t have it. 

 I already plan to hunt down for some 8416 gold pins to start a small tube collection. cheers. 

Scotts Vintage (eBay)


----------



## TimJo

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_I wrote to an eBay seller and found out he lives less than 2 miles away from where I live (a really bad sign for my wallet). We spoke shortly on the phone and gave an impression that he has a large variety of NOS stashed in his basement. In fact, if I needed a specific tube I would have to help go through his bunch, although he has them categorized in size, no. pins, p/n, etc.

 Since I’m not familiar with tube brands/models and their variants (let alone their sound quality), I wonder if I can get some help in spotting a few decent (better than average) tubes just by looking at his short listing. He mentions if the tubes I needed do not appear in his store list doesn’t mean he doesn’t have it. 

 I already plan to hunt down for some 8416 gold pins to start a small tube collection. cheers. 

Scotts Vintage (eBay)

_

 

You should certainly pick up the 12BH7A's...


----------



## keyid

yea, I would try those 12bh7 dont know much the other tubes. His ebay page has a horrible background cant read the words.


----------



## olblueyez

Forget all those other tubes - http://www.head-fi.org/forums/f5/rap...6/#post5713263


----------



## keyid

would bite but soldout atm, will keep an eye out on the bay. oh they got 6n-DR tubes but also sold out.


----------



## olblueyez

I just bought a pair on fleabay so I have some spares, they are out there.


----------



## zkool448

Ok thanks guys. Will raid his stash anyway to see if I can spot anything similar based on what I've seen here so far. cheers.


----------



## smeggy

Ok, looks like I'll need to split a pair of these Tunsrams with someone. I can see I'm gonna end up with a little set of bottles to play with.


----------



## keyid

Hey smeggy, I would be interested getting one. Send you pm


----------



## smeggy

I'll get back to you on it when I have news


----------



## wiatrob

holland;5703883 said:
			
		

> ....though wiatrob at one point said his 6H30-DR is his favorite in the CTH... /QUOTE]
> 
> Until I got a grab bag of cool 12AU7s: 5814WA, 6189WA, JTL-12AU7A
> 
> ...


----------



## wiatrob

All,

 I haven't been paying attention to this thread like I should've - lots of good info here!


----------



## zkool448

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_Forget all those other tubes - http://www.head-fi.org/forums/f5/rap...6/#post5713263_

 

Thanks olblueyez, just ordered a pair. 

 Although they're decribed as matched ($20+$7 shipping), only one of them is tungsram, the other is tesla. I only needed one for the CTH anyway


----------



## olblueyez

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Thanks olblueyez, just ordered a pair. 

 Although they're decribed as matched ($20+$7 shipping), only one of them is tungsram, the other is tesla. I only needed one for the CTH anyway 
	

	
	
		
		

		
		
	


	


_

 

I saw that auction, let us know how the Tesla compares. I wonder if the Tesla is a rebranded Tungsram?


----------



## cfcubed

BTW I've a "real" Tesla (non-JJ) that I tried for a bit... It sounded good, as pretty much all my tubes do in the CTH, but was *very* microphonic.

 I must have 10->12 tubes I can use in the CTH & have tried several but this week's fav is that Siemens "chrome plate" ECC82/12AU7 (1963) again. 

 What we need is a CTH mod with a tube carousel
	

	
	
		
		

		
		
	


	




 Hmmm, I'll have to think on this...


----------



## olblueyez

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_BTW I've a "real" Tesla (non-JJ) that I tried for a bit... It sounded good, as pretty much all my tubes do in the CTH, but was *very* microphonic.

 I must have 10->12 tubes I can use in the CTH & have tried several but this week's fav is that Siemens "chrome plate" ECC82/12AU7 (1963) again. 

 What we need is a CTH mod with a tube carousel
	

	
	
		
		

		
		
	


	




 Hmmm, I'll have to think on this..._

 

An external box with 6 or 12 tube sockets and a rotary switch or switches?


----------



## cfcubed

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_An external box with 6 or 12 tube sockets and a rotary switch or switches?_

 

I was _kinda_ joking about such a thing but who knows... Stranger things have been built around these parts
	

	
	
		
		

		
		
	


	




 Not sure how external it could be since we'd want to keep all the wires as short as possible. And it would sorta negate the key attribute of transportability. But perhaps an external box to fit on top of a CTH w/tube saver or somesuch underneath to plug into the CTH's socket.... Hmm, I better stop now.


----------



## MrSlim

Ok, I'll bite.. You'll need a computer controlled robotic arm.. made out of lego.. 

 I wonder if anyone ever invented a zif (zero insertion force) socket for tubes..


----------



## smeggy

Quote:


  Originally Posted by *MrSlim* /img/forum/go_quote.gif 
_Ok, I'll bite.. You'll need a computer controlled robotic arm.. made out of lego.. 

 I wonder if anyone ever invented a zif (zero insertion force) socket for tubes.._

 

dunno, but the old socket saver I bought is pretty close, nice easy smooth insertion and extraction, much less force needed for quick tube swapping.

 I should be getting my upgrade cap in the mail today so I can switch it out in preparation for the 6n6p tubes that should be here soon along with other parts to do my all-in-one tube case.


----------



## zkool448

Quote:


  Originally Posted by *olblueyez* /img/forum/go_quote.gif 
_I wonder if the Tesla is a rebranded Tungsram?_

 

I'd be floored if the tesla is just that, but I highly doubt it is a rebadged looking at the pic below. According to my research, it looks like rebrands exist having steel pins and 3 holes in the plate, then it's Tungsram.

 Based on your impressions though it sounds like a real winner to me as it has the qualities I want sq wise. If it meets my needs I'm definitely chasing down an extra pair and see how well they perform also with the SOHA II.


----------



## Ynis Avalach

I was wondering if someone could answer me the following questions:

 1. Since someone pointed out that the LM2595 is running near it's limited 1A when using 6n1pi's, I ordered an additional 2596 but this one.
 Now after ordering I looked at it a little closer and it's 12V chip. Is this working anyway or can't I use it?

 2. Concerning the higher heater current upgrade I also ordered an additional L2H, this one. It's not a toroid, couldn't find one at Farnell.
 Do I have to be careful with non-toroid chokes, or is the magnetic leakage with a iron core irrelavent?

 Thanx for any help!!
 Ava


----------



## cfcubed

Quote:


  Originally Posted by *Ynis Avalach* /img/forum/go_quote.gif 
_ I ordered an additional 2596 but this one.
 Now after ordering I looked at it a little closer and it's 12V chip. Is this working anyway or can't I use it?_

 

Not really, can't be used here as its a fixed voltage regulator (puts out 12v period). It should have that ADJ bit at the end.
 Don't feel bad, I _somehow_ ordered two 5V fixed voltage LMs by mistake & they are of no use (now anyway).

  Quote:


  Originally Posted by *Ynis Avalach* /img/forum/go_quote.gif 
_ Do I have to be careful with non-toroid chokes, or is the magnetic leakage with a iron core irrelevant?_

 

I don't _think_ I'd worry about magnetic leakage.. But things are very tight in the CTH. Recommend using your ears as the judge (compare your CTH in stock/BoM form (IOW, make sure you've a CTH working in stock form 1st) to it after you make these upgrades).


----------



## Ynis Avalach

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Not really, can't be used here as its a fixed voltage regulator (puts out 12v period). It should have that ADJ bit at the end.
 Don't feel bad, I somehow ordered two 5V fixed voltage LMs by mistake & they are of no use (now anyway).


 I don't think I'd worry about magnetic leakage.. But things are very tight in the CTH. Recommend using your ears as the judge (compare your CTH in stock/BoM form (IOW, make sure you've a CTH working in stock form 1st) to it after you make these upgrades)._

 

I will do this. Thank you. The 6n1pi isn't here yet anyway.


----------



## smeggy

YAY! just got a package of 6n6p tubes from Lithuania, can't wait to give them a shot tonight


----------



## smeggy

Switched it down to 6v, plugged in the 6n6p and off it flew... nice bass increase over the Siemens and the rest sounds damn nice too. I'm very happy with it especially considering how cheap these tubes are. I like how this sounds a lot 
	

	
	
		
		

		
		
	


	




 Big tube too, twice the size of the little E82CC and no heat or stability problems so far.


----------



## nux

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Switched it down to 6v, plugged in the 6n6p and off it flew... nice bass increase over the Siemens and the rest sounds damn nice too. I'm very happy with it especially considering how cheap these tubes are. I like how this sounds a lot 
	

	
	
		
		

		
		
	


	




 Big tube too, twice the size of the little E82CC and no heat or stability problems so far._

 

Did you upgrade the heater circuitry for this?


----------



## smeggy

Nope, just did the cap mod. The rest seems fine, if a problem does happen I'll upgrade that but it seems happy so far. I may put a bigger heatsink on it though as I'll have room if I lay it sideways.


----------



## zkool448

smeggy, are you talking about the C3H fix or another cap mod? I must've missed it..


----------



## smeggy

Yep, that's it


----------



## zkool448

Cool. Atleast yours shipped from Lithuania quickly. 

 Ordered my Tungsram last week (comes from Bulgaria), and they've not even left their warehouse yet


----------



## smeggy

Yeah, not bad and they sound great. The Siemens is smooth and nice all over but this has balls and bite which suits my prefs very well.


----------



## cfcubed

Just an FYI that seems to me the 800ma draw of 6n6p is right at the spec limits of the devices in the std CTH (w/revised C3H of course). 
 If it was mine I'd put some sort of heatsink, or part of a heatsink, on ICH for that case.


----------



## smeggy

yeah, I picked some up at ratshack to do that. and mebbe a 220 on the ICP as it's very hot. Making them fit is gonna be fun 
	

	
	
		
		

		
		
	


	




 I'm sure I can dremmel the sinks to fit which will do fine.

 If it comes to it I'll add a small transfo and put a small silent fan under it


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_yeah, I picked some up at ratshack to do that. and mebbe a 220 on the ICP as it's very hot. Making them fit is gonna be fun 
	

	
	
		
		

		
		
	


	




 I'm sure I can dremmel the sinks to fit which will do fine._

 

Yes, a heatsink is always required on ICP (24V reg) & the smallish one the BoM _may_ need bitty modding (break off lowest fins, bend it a bit) esp. if you've not mounted parts near the RS low enough (or not soldered ICP high enough). 
 That & ventilation holes or perf top & you are GTG if using the std case. Larger cases can get by with less:


----------



## smeggy

Mine is going in a big ally case and I have room for a TO220 if I bend ICP over a bit, say 45deg of so, ICH will need more fiddling to fit a sink as it's buried between a bunch of other stuff so I'll do some sink mods to the BoM ICP sink to fit. 

 I'm sure it'll appreciate whatever it can get, that tube runs it all very hot but it's soo good. This is the sound I wanted.


----------



## keyid

yea the 6n6p sounds good, but im finding myself going back to the Siemens Triple Mica 5814A.


----------



## smeggy

Yeah, the Siemens E82CC I have is really nice but I wanted more slam and the feeling of raw power the 6n6p gives. I like the more aggressive presentation for my metal prefs


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Yeah, the Siemens E82CC I have is really nice but I wanted more slam and the feeling of raw power the 6n6p gives. I like the more aggressive presentation for my metal prefs_

 

One of the key beauties of this amp... Preference voicing. I've been going back-n-forth between my Siemens (sweet, accurate) & Amperex 6DJ8 (more slam) every couple/few weeks. Now I may pick up a 6n6p someday


----------



## keyid

the Siemens Triple Mica 5814A does deliver slam but not as much as the 6n6p but definitely more refined, my siemens E82CC does not.


----------



## smeggy

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_One of the key beauties of this amp... Preference voicing. I've been going back-n-forth between my Siemens (sweet, accurate) & Amperex 6DJ8 (more slam) every couple/few weeks. Now I may pick up a 6n6p someday
	

	
	
		
		

		
		
	


	


_

 

PM your addy and I'll pop one in the mail to you.


----------



## arteom

oops, posted in the wrong thread. Btw, listening with Siemens ECC88, sound nice .


----------



## cfcubed

nevermind.


----------



## smeggy

Here's mine with the latest additions, new cap and upgraded sinks. Original heatsink and new heatsink in their new positions to help with cooling down the new tube draw on it's test platform until it's ready for transplant.


----------



## sachu

^^ awesome !!


----------



## zkool448

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Here's mine with the latest additions, new cap and upgraded sinks. Original heatsink and new heatsink in their new positions to help with cooling down the new tube draw on it's test platform until it's ready for transplant._

 

smeggy, I was gonna comment on your puny C3H upgrade cap since mine is roughly the same height as C3P, but it looks like you left the original connected on the pcb just hooked a larger cap in parallel (placed just behind ICH?).


----------



## wiatrob

And I see our old friend the Murata L2H springing mushroom-like from the pads!

 I have the 1A version of the BOM L2H (vertical Toroid), but have yet to test it (although it should work fine and fits the board better than the Murata)


----------



## smeggy

Yes the cap is paralleled with the original, seemed simpler than trying to replace it. The wee mushroom is quite cute actually, sitting there all a kilter 
	

	
	
		
		

		
		
	


	




 With the new cap poking out the back and honking big heatsink I think I'll call it SCTH (semi-compact tube hybrid)


----------



## TimJo

It's looking great smeggy. What enclosure is it going to find itself in?

 These mods are making me want to build another at some point. I have some ideas brewing...

 For the moment, I'm going to try to focus on the EHHA - and the Bijou (as my SOHAII board gathers dust).


----------



## TimJo

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Tube-wise, Amperex (Holland) 6DJ8s & Siemens 12au7 chrome plates are still at the top of my heap. They each have *very* different presentation (6DJ8s - punchy/great bass, 12au7 - honest/flatter)._

 

Just picked up a pair of Amprex ECC88's (6dj8's) and they do sound fantastic. The bass is killer, but I'd say it's not as detailed as my CBS/Hytron 7730 (still my overall favorite in the CTH). But I'm really enjoying the bass on the Amprex tubes. Listening to Pavement right now, and the bass extension is amazing. Going to spin _Real Emotional Trash_ next and see what Joanna Bolme's bass sounds like. Can't wait to try these out in the Bijou.


----------



## arteom

Hope it's not against to rules to post this here, is anyone here interested in trading some tubes for the CTH? I have some pairs of 6922/6DJ8 tubes for my X-Can v8 that I don't use (settled on a pair of Sylvanias). So looking to trade one and keep one for the CTH, have JAN Phillips (marked in green print), Westinghouse, Siemens (currently using one of thse and its really nice). If anyone is interested please shoot me a PM, looking to taste some different brands. Might be interested for trading a few for one nice tube or just one for one.


----------



## cfcubed

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Just picked up a pair of Amprex ECC88's (6dj8's) and they do sound fantastic. The bass is killer, but I'd say it's not as detailed as my CBS/Hytron 7730 (still my overall favorite in the CTH). But I'm really enjoying the bass on the Amprex tubes. Listening to Pavement right now, and the bass extension is amazing. Going to spin Real Emotional Trash next and see what Joanna Bolme's bass sounds like. Can't wait to try these out in the Bijou._

 

I think your observations are spot-on WRT 6dj8, so I guess add a CBS/Hytron 7730 to my search list... You've mentioned that tube quite a bit as a fav in the CTH.


----------



## wiatrob

6GU7 anyone? Just showed up at my desk, more soon...


----------



## dBel84

imho, one of the best tubes i have dropped into the "other" amp ..dB


----------



## wiatrob

I am liking it very much, clear, excellent staging, generous but not bloomy bass (hey, tubegeek terms!) and _cheep (_relatively_)_...

 Perhaps we might form a tier system for tubes - Tier 1 beginner/cheep Tier 2 intermediate/ affordable(?) Tier 3 Spendy/the best!

 Oh, drat, individual taste might spoil that...nevermind


----------



## smeggy

heh, my fave tube cost all of about $2


----------



## adamus

my tube of choice only cost $15. 

 Amperex PQ 8416, best all rounder IMHO.


----------



## TimJo

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_6GU7 anyone? Just showed up at my desk, more soon..._

 

I'll add that to my list...

  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_heh, my fave tube cost all of about $2_

 

And are you going to let us know what it is? 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_my tube of choice only cost $15. 

 Amperex PQ 8416, best all rounder IMHO._

 

I really enjoy that one as well...


----------



## Forte

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_6GU7 anyone? Just showed up at my desk, more soon..._

 

 Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I am liking it very much, clear, excellent staging, generous but not bloomy bass and cheap (relatively)..._

 


 Sounds good, just ordered a couple to try, couldn't resist. 
	

	
	
		
		

		
		
	


	




 I think I have now spent more on ordering tubes than on building the amp!


----------



## smeggy

The tube I was talking about is the 6n6p. Millions of them on ebay for cheap. I got mine from Lithuania and they usually come in batches of 4-10 tubes per order. I got 6 for about $14


----------



## keyid

yea 6n6p sound great, Im wondering if the 6h30-dr would be more of an improvement on the 6n6p.


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_The tube I was talking about is the 6n6p. Millions of them on ebay for cheap._

 

Yes & merci beaucoup smeggy... Listening to the 6n6p now & can say it does sound good. Need to let it warm up & listen & compare more, but it WILL be a keeper for sure. 
 And thanks to comments here I've a Amperex PQ 8416 on the way too. _Someday_ I need to pare down these tubes tho
	

	
	
		
		

		
		
	


	




 BTW we are working a bit in the background trying to come up with a (somewhat) complete list of tubes compatible (& good sounding) in this amp. I hinted about this elsewhere but we may find more tubes coming into the fold then then originally considered.


----------



## rds

Has anyone tried Auricaps in the CTH? 

 ...It looks like the 0.22uF could be tombstoned in the small bom case, though the ridiculous 18awg wire would be annoying as always.

 EDIT: Now someone has 
	

	
	
		
		

		
		
	


	














 Initial impressions are very positive, but I am listening to Live-Evil which always sounds awesome. I will have to take some time to compare this with my otherwise identical CTH with Sonicap Gen II coupling caps.


----------



## cfcubed

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Has anyone tried Auricaps in the CTH? 
 EDIT: Now someone has 
	

	
	
		
		

		
		
	


	



 I will have to take some time to compare this with my otherwise identical CTH with Sonicap Gen II coupling caps._

 

Nice! Would like to hear what you think. And they look to fit in BoM case too
	

	
	
		
		

		
		
	


	



  Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_my tube of choice only cost $15. Amperex PQ 8416, best all rounder IMHO._

 

Listening to an NOS one of these now & they are quite nice. Good bass slam/attack while preserving good detail & ever so slightly rolled top-end - all good things & all IMHO of course. Now the only ones on my "someday" search list are Siemens CCa & CBS 7730 but no rush on those for sure... 
_Edit: But of my tubes, Siemens E82CC/12AU7 is still my "detail king" revealing things in the music I've not noticed before. Mine happens to be the fancy-pants "chrome plate" ver. Might have to snag that Siemens Triple Mica 5814A tho. _

 Tube rolling is really something for sure & as mentioned elsewhere we _may_ have even more options for this amp, for the tweakers anyway.

 So _someday_ I need to thin my tube herd & put some in FS forum _<<< Edit: Well not really thinning since I still buying them
	

	
	
		
		

		
		
	


	


_


----------



## Ynis Avalach

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Listening to an NOS one of these now & they are quite nice. Good bass slam/attack while preserving good detail & ever so slightly rolled top-end - all good things & all IMHO of course. Now the only ones on my "someday" search list are Siemens CCa & CBS 7730 but no rush on those for sure... 
Edit: But of my tubes, Siemens E82CC/12AU7 is still my "detail king" revealing things in the music I've not noticed before. Mine happens to be the fancy-pants "chrome plate" ver. Might have to snag that Siemens Triple Mica 5814A tho. _

 

 Oh yeah those Siemens CCa, or Telefunken CCa. Or maybe them E288CC, they don't have this good reputation, but still a maybe.
 Currently installing Mundorf Silver/Gold, because of a stupid mistake I made I got stuck with them, wanted the Silver/Oil ones! Stupid me.
 Ava


----------



## smeggy

Are those Auricaps replacing the little yellow block ones?


----------



## zkool448

That's right smeggy (C4L, C4R).


----------



## smeggy

Hmm, does it actually make any difference I wonder.


----------



## DoYouRight

This is going to be my bedside rig's Tubey I think. Thanks for all the great tweaking info and Ill post what I develop over my course


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Hmm, does it actually make any difference I wonder._

 

That question has launched a Thousand Cap Purchases my friend - if you can hear the differences in sound between tubes, chances are you can hear Cap differences as well...
	

	
	
		
		

		
		
	


	




 BTW - I have the 6n6 back in my work rig, (but with the Grados.) Very peppy...


----------



## Ynis Avalach

Might I ask which your favorite tubes are when listening with the RS-1s?

 I've definitly not decided yet, because I'm stuck with an imbalance in the soundstage, trying using matched transistors. 

 Ava


----------



## smeggy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_That question has launched a Thousand Cap Purchases my friend - if you can hear the differences in sound between tubes, chances are you can hear Cap differences as well...
	

	
	
		
		

		
		
	


	




 BTW - I have the 6n6 back in my work rig, (but with the Grados.) Very peppy..._

 

I did wonder as I know going undersize on output caps can quench bass a bit, but I have no idea what these ones do or are for. I might try something though, just because..


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I did wonder as I know going undersize on output caps can quench bass a bit, but I have no idea what these ones do or are for. I might try something though, just because.. 
	

	
	
		
		

		
		
	


	


_

 

For these interstage coupling caps I think we are all sticking w/design value 0.22uf & rated 100v or better. So we aren't talking size WRT the cap's value like you might for amps w/large output capacitors on their outputs (to block DC).

 I think we can agree, maybe, that the effects of various coupling caps is more subtle than that of various tubes. And you must watch "wearing out" coupling cap pads / traces when rolling them. I _think_ the WIMA upgrade caps are easiest to deal with.


----------



## smeggy

I could do what I did on the other cap and just parallel though that may defeat the purpose of the better caps. The one at the back was same make/type but bigger so no biggie there.

 I'm just looking to get the very best from this little treasure. I really like this amp.


----------



## wiatrob

Smeggy,

 Probably not the best idea to parallel caps in the audio path (especially disparate types.) If you want to hear the difference a cap makes, my loaner amp has socketed coupling caps. I'll swap you your K1000s for a month and you can cap roll to your heart's content 
	

	
	
		
		

		
		
	


	




 cfCubed is right about the caps - probably more subtle sound diffs. And you can get a whole bunch of tubes for the price of some esoteric audio caps.

 Two resources sited a bit about caps:

Humble Homemade Hifi

http://www.head-fi.org/forums/f21/or...thread-284863/


----------



## rds

Maybe not the best segway into my post...

 I've been won over by the Auricaps. I was very skeptical; I expected to be hard pressed to nail down any real difference between these two. I mean both are very well respected caps.

 Listening to 'inamorata and narration by conrad roberts' the trumpet had a richer and more full sound with the Auricaps that really brought it to life. The drums too felt more real, with a sharper attack and very nice timbre. I equate this to some midrange emphasis happening with the Auricaps. But, wow, does it sound great.

 Strangely, not only was the midrange nicer but the top end was more extended and detailed (like very obviously so). Listening to such a complex track the superior instrument separation of the Auricaps was also clearly apparent. 

 Like I said, I'm won over, and I'll be ordering a pair of Auricaps for my own CTH tomorrow.

 I should mention I was using a 6DJ8 for most of this comparison, and swapped the same tube back and forth between the amps.


----------



## smeggy

heh, I'm not into exotic or esoteric. I'm skeptical at best on such things 
	

	
	
		
		

		
		
	


	




 As to the K1k, you can borrow them after sachu has finished with them 
	

	
	
		
		

		
		
	


	




 RDS,
 how much are those Auricap things, dare I ask?


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_As to the K1k, you can borrow them after sachu has finished with them 
	

	
	
		
		

		
		
	


	


_

 

yeah..that's going to be a problem..i like them sooo much


----------



## rds

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_RDS,
 how much are those Auricap things, dare I ask?_

 

about $12 each


----------



## smeggy

Oh, not too bad, I recalled mundorfs being about $30 each!

 Bad sachu, bad!!


----------



## wiatrob

I've tried Wimas, Obbligato Gold (just as a looong lead/e12 value test, no critical listening)

 and I have some russian teflons and pios, and now some Soniccaps to try 'someday...'

 Smeegy - thanks for the offer! Doubt Sachu will ever get 'done' with them.


----------



## smeggy

heh, 
 well I have plenty to keep me busy and I won't miss the k1k for a while so no problems. I guess I could order some Auricaps or similar next payday and see. I'm wondering those terminal blocks fit the cap holes? That way I could screw tight any cap I wanted. If not, where do you find sockets for such things?


----------



## olblueyez

Could you butcher an op-amp socket?


----------



## cfcubed

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Maybe not the best segway into my post...
 I've been won over by the Auricaps. <snip>
 Like I said, I'm won over, and I'll be ordering a pair of Auricaps for my own CTH tomorrow._

 

It's great to get this info out there... I think the small point Bill & I are trying to make is that rolling coupling caps, w/o using SIP socket or something _* (Edit: like these * but their holes aren't really big enough)_, is tough on the PCB. And more difficult in CTH than some amps due to the tight PCB tolerances & quarters.

 Its great to ID C4 options, esp those that fit in the BoM case.


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_heh, 
 well I have plenty to keep me busy and I won't miss the k1k for a while so no problems. I guess I could order some Auricaps or similar next payday and see. I'm wondering those terminal blocks fit the cap holes? That way I could screw tight any cap I wanted. If not, where do you find sockets for such things?_

 

Well, since you are generously offering, I accept (now I can bug Sachu too!)

 I'll send you a 'cap rolling' starter kit with Sonicaps, Wimas, and PIOs, and some sip sockets. PM me your address, plz...

 I had considered including a strip of SIP sockets in the kits at one point. I may do that in the future (or offer a 'tweaker's kit')


----------



## smeggy

Ooh thanks 
	

	
	
		
		

		
		
	


	




 Actually, looking closer at the board last night it does have those mounting pins already but the caps are soldered in. I had a small issue with the caps being a bit loose so I fixed it with solder 
	

	
	
		
		

		
		
	


	




 oops.

 Anyway, at least the caps are not soldered directly to the board so replacing them will be less dangerous.

 Thanks for the offer, PM coming your way.


----------



## rds

Does anyone have experience with these tubes? They look brand new, and have gold pins 
	

	
	
		
		

		
		
	


	



 olblueyes?










 EDIT nevermind, could have used the search function 
	

	
	
		
		

		
		
	


	




 But now you have some nice pictures


----------



## olblueyez

I dont know if my amp would support that tube. It looks like a very interesting tube though.

 Only thing is, it was made in America and not Holland, its not a real Amperex. Unless I am misunderstanding the box.


----------



## cfcubed

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Does anyone have experience with these tubes? They look brand new, and have gold pins 
	

	
	
		
		

		
		
	


	



 EDIT nevermind, could have used the search function 
	

	
	
		
		

		
		
	


	




 But now you have some nice pictures_

 

Yep, we just discussed these 8416s few pages ago(?) 12.6v heater 6922s is what I think runeight refered to them as. 
 Think its a fav of adamus... So I picked one up & have been listening to it a couple days. I like the sound. Like the Amperex 6dj8s I "raved" about a while back but with more detail.


----------



## holland

i think they are very nice tubes. one of my favs, used in my soha 2 for quite a while.


----------



## adamus

its my tube of choice at the moment, and had been in my cth fro the last 3 weeks.


----------



## TimJo

Agreed. It's one of my favorites as well...


----------



## cfcubed

So, after seeing a couple tubes were tried in CTH that had other than 6.3v & 12.6v heater and found to work & sound good, knew there was nothing keeping the design from *directly supporting more heater voltages*.

 Nothing but a few more resistors & a way to switch among them.

 Calculated (ideal) R3H values for various heater voltages:
*Votage / R3H (ideal)
 4.2v / 3.3k
 5.6v / 5.8k
 6.3v / 7.4k
 7v / 9.3k
 8.4v / 15.1k
 9.4v / 23.3k
 12.6v / <none>*

 Wiatrob was willing to test & confirm things & has done so using *4BQ7A, 5BQ7A, 7AU7 and 9AU7 *tubes. *This tweak further extends tube options in the CTH beyond 6.3v & 12.6v heated tubes.* So users of a CTH with this tweak have an even larger selection of tubes to choose from, probably finding some very good deals for tubes running at non-std heater voltages. 
_Edit: So beyond the 6.3/12.6 tube list, this tweak should add those above, 7DJ8 and 8FQ7 and there are likely more overlooked (e.g. 6AU7, 6BQ7)_

 The challenge is choosing which heater voltages you want & finding a SP#T switch to switch among them. We found a nice 1/2 inch dia one that can be configured for 2 -> 12 positions:





 Wiatrob can chime in w/more info, but I _think_ it remains to be seen if this tweak can be squeezed into the BoM case.


----------



## wiatrob

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Wiatrob can chime in w/more info, but I think it remains to be seen if this tweak can be squeezed into the BoM case._

 

Thanks for coming up with the idea and R values!

 I'll post some more pictures later this evening. I think it is possible to fit this in the BOM case if you sacrifice the space above the AC jack and keep your resistor leads very short (mine are a wee bit longer than needed). The rotary switch and resistors end up living right in the space above the heater resistor switch leads. I'll test this as soon as time allows.

 BTW - this test build supports all the heater voltages mentioned in Chris' post. I left the rotary configured as a 12 position and alternated soldering resistors, so it's not the most compact implementation.

 BTW - 7Au7 and 9AU7 RCA Cleartops sound quite good - I know they don't have the biggest following among this group, but at $2.00 a piece...


----------



## cfcubed

Just to clarify what this is... It's the possibility to extend CTH's heater values from 2 (6.3, 12.6) to more. This would be done by NOT populating the R3H spot on the PCB and instead running wires to those pads & using a single-pole switch with more than two "throws".

 In the JPG below, one R3H pad lead would go to the wiper "A" and each of the desired heater resistors would go on #1 -> #whatever switch terminals. All the "loose" ends of those resistors would be soldered together & shrink-tubed to a wire leading to the other R3H pad. There still would be only *one* R3H value seen by the PCB at a time.


----------



## rds

I just looked at my back panel drawing at it seems that switch can be put where the fuse currently is on my build, with a little modification (while keeping the power switch). However, the depth may be an issue. It looks like we have about 20mm available.

 Wiatrob what do you think the minimum achievable depth is?


----------



## wiatrob

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Wiatrob what do you think the minimum achievable depth is?_

 

I need to measure with the BOM case panel on. I'll try to get a measurement soon.


----------



## wiatrob

A few more pics.

 I bent each resistor lead around and soldered it to the next resistor, making a 'ring' of leads. I left the last resistor lead in place, and sleeved it in teflon.

 This lead and the wire are soldered into the R3H location. I jumpered the heater switch positions. Not that you can still see my old switch in the case, but it's since been removed.

 I did a little more hack woodwork - the switch is mounted 1/4" into my pane so I _do_ have more clearance in this build than a BOM case.

 I will do some comparisons with the stock power switch and RDS suggested panel template this week..


----------



## smeggy

Very cool, nice work guys.


----------



## Forte

Oh Great, more tubes to buy! 
	

	
	
		
		

		
			





 Nice work guys and neatly done.


----------



## rds

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_A few more pics.

 I bent each resistor lead around and soldered it to the next resistor, making a 'ring' of leads. I left the last resistor lead in place, and sleeved it in teflon.

 This lead and the wire are soldered into the R3H location. I jumpered the heater switch positions. Not that you can still see my old switch in the case, but it's since been removed.

 I did a little more hack woodwork - the switch is mounted 1/4" into my pane so I do have more clearance in this build than a BOM case.

 I will do some comparisons with the stock power switch and RDS suggested panel template this week.._

 

You'd have to play a bit with the positioning in my template. If you have autocad I can send you the template.


----------



## wiatrob

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_You'd have to play a bit with the positioning in my template. If you have autocad I can send you the template._

 

No Autocad here 
	

	
	
		
		

		
		
	


	




 However, i do have the template printed out. I will be building up a 'stick' unit this week for a door prize for the next Colorado meet (see sig) -I'll take a look at your template and see how what kind of fit we can get.


----------



## cfcubed

Few things:
Did not want rds auricap option & impressions to be lost in this heater switch biz. Sounds like a nice option.
cheaper R3Hs on the switch, like Xicon 1/8W metal films @ 3.5mm long, are smaller than VDs & could buy a few MMs in depth.
Forte - know you were kidding but instead of more tubes to buy, thinking less expensive ones to buy. Could bring a bunch more $2 tubes to the plate.
Someday we should finish compiling a list of tubes that work in CTH. Although perhaps not optimized for them, the full list w/this 7 heater tweak could be twice as large as the original one.


----------



## TimJo

Nice work guys. 
	

	
	
		
		

		
		
	


	




 Since I really am happy with my current 'compact' model for it's portability, I can see a second version in my future with all of the heater mods in place - more of a desktop version in a custom enclosure, with a box full of tubes sitting next to it.


----------



## TimJo

So yesterday, I did a mini shootout between two of my favorite 12AU7 variants. Both tubes were made by CBS/Hytron ~ the 7730 & the 7318.

 The 7318 has short plates and steel pins, whereas the 7730 has long plates and gold pins, both with halo getters. 

 Here's a little description of the 7730 off the interweb:


> _This is a premium version of the 12AU7 made only by CBS/Hytron. This tube has very low noise characteristics and heavily plated gold pins. These were intended for critical test instrument applications, but due to their superior low noise performance, these make excellent choices for audio applications._


There is a lot of similarity between the two tubes. Both produce an enormous amount of detail, with the 7730 winning out a bit, especially with harmonics produced with stringed instruments. It's the only tube I've listened to where you can really hear a lifelike reproduction of the harmonics that are produced from a steel fingerpick breaking contact with a well tuned steel string. It also is able to reproduce the sound of harmonics that are created between the fret and the string with more realism than I have heard elsewhere. That being said, the 7318 does a really good job as well, but not like the 7730 (at least through DT880's).

 But, after listening to to several albums with both tubes, my overall favorite ends up being the 7318 because of what my ears perceive to be a flatter response across the entire frequency spectrum. It seems like the 7730 dips a bit somewhere in the lower mids, and doesn't have as much bass extension when compared to the 7318.

 Both tubes are amazing though...


----------



## Trapper32

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_So yesterday, I did a mini shootout between two of my favorite 12AU7 variants. Both tubes were made by CBS/Hytron ~ the 7730 & the 7318.

 The 7318 has short plates and steel pins, whereas the 7730 has long plates and gold pins, both with halo getters. 

 Here's a little description of the 7730 off the interweb:



This is a premium version of the 12AU7 made only by CBS/Hytron. This tube has very low noise characteristics and heavily plated gold pins. These were intended for critical test instrument applications, but due to their superior low noise performance, these make excellent choices for audio applications.

Click to expand...

There is a lot of similarity between the two tubes. Both produce an enormous amount of detail, with the 7730 winning out a bit, especially with harmonics produced with stringed instruments. It's the only tube I've listened to where you can really hear a lifelike reproduction of the harmonics that are produced from a steel fingerpick breaking contact with a well tuned steel string. It also is able to reproduce the sound of harmonics that are created between the fret and the string with more realism than I have heard elsewhere. That being said, the 7318 does a really good job as well, but not like the 7730 (at least through DT880's).

 But, after listening to to several albums with both tubes, my overall favorite ends up being the 7318 because of what my ears perceive to be a flatter response across the entire frequency spectrum. It seems like the 7730 dips a bit somewhere in the lower mids, and doesn't have as much bass extension when compared to the 7318.

 Both tubes are amazing though..._

 

Great write up TimJo Being a guitarist myself I really listen for those harmonics you described. Have u listened to the Bugle Boy 6dj8 and if you have i wonder how they compare to the 7318 or 7730.


----------



## TimJo

^^ The only 6DJ8 I have (so far 
	

	
	
		
		

		
		
	


	




) is an Amperex made in Holland. It is a great tube with the best low end presence out of all the tubes I have heard so far. If I want to listen to a recording, and focus on the bass player, that's my tube of choice. But in terms of detail, both of the CBS/Hytron tubes win out.

 I'm on the look out for some Bugle Boy's though - they get great reviews across the board, and it would be interesting to compare them to the Amperex 6DJ8's.


----------



## cfcubed

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_ < snip >
 I'm on the look out for some Bugle Boy's though - they get great reviews across the board, and it would be interesting to compare them to the Amperex 6DJ8's._

 

I've 6.3v-heated Amperex (Holland - white label) & Bugle Boy (both 6DJ8 AFAIR) and IIRC the BB may add a bit of detail that the non-BB lacks while retaining it strong bass. Perhaps its my specific tubes but I'd not say the presentation differs greatly IMO.

 Those 7NNN CBS/Hytrons are not very common, but from what I'm reading I _think_  a couple types of Siemens tubes might be worth trying, e.g. for midrange detail. Seems keyid feels other Siemens tubes may offer even better _detail & slam_...


----------



## smeggy

I swapped the caps over to Sonicaps thanks to waitrob and it's going great.

 I currently have the CTH and Beta/EHHA wired to the Pico DAC so I can play the same thing through all three amps simultaneously and the CTH can hold it's head high in this company. It really does perform well above it's diminutive size and is extremely good in in t's own right. 

 It's a great all-rounder and does nothing wrong. The Beta has the most solid sound of the three, with thunderous bass and tight as a drum and very smooth. The EHHA isn't as solid or thundering in the lower regions but has a delightful sense of air and separation with nice atmosphere and the CTH is the more aggressive of them with the 6n6p tube and upgraded caps (tuned that way on purpose). 

 It's a sparkling amp with great bite and clarity and very appealing all round sound. It's hard for me to say one is better than the other because they each have distinct strengths and there's no way I'd say the CTH was outclassed, just a different flavor depending on what I'm listening to. 

 Remarkable little amp. After a week of nothing but beta and ehha I thought it might be a bit of a let down going back to the CTH, nope, not a bit of it. Every bit as good as I remembered and it's happily blasting my ears off with some spikey metal and it's a perfect match.


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Remarkable little amp. After a week of nothing but beta and ehha I thought it might be a bit of a let down going back to the CTH, nope, not a bit of it. Every bit as good as I remembered and it's happily blasting my ears off with some spikey metal and it's a perfect match.



_

 

Thanks smeggy for the little overview of these amps. Good to hear this as the CTH is the one I'm sticking with for quite a while.

 Having heard a Beta22 @ a meet plan to build one this winter but w/what people are saying about EHHA & Bijou who knows where things will end


----------



## wiatrob

RCA 6CG7 cleartop, Soncicaps, Smeggy's K1K. Amzing kick - the K1Ks take up the slack i had with my output resistor choice, I can make it to about half way!

 Haven't had a chance to try any other combos with this setup yet, but I have the Siemens chrome plate here later this afternoon. 

 I am really digging the SonicCap GENIIs, think this will be my go to...

 I mounted them horizontally with the leads bent under in a 't' shape, no noise issues...


----------



## smeggy

heh, the amp looks so teeny. Since adding the bigger caps to mine the e12 keeps tripping every few minutes. Any cures for this?


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_heh, the amp looks so teeny. Since adding the bigger caps to mine the e12 keeps tripping every few minutes. Any cures for this?_

 

I _think_ we've considered e12 tripping issues solved quite a while back (some resistor value tweaks AFAIR)... Since then many are running non-BoM caps & some have monster big caps (S/Os, Gen Is, etc.) w/o problems.

 Maybe a decent pic of your C4 area would help...


----------



## sachu

I don't remember what values i used for the E12 resistor values on Smeggy's CTH build. But am thinking it was the current BOM values.


----------



## cfcubed

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I don't remember what values i used for the E12 resistor values on Smeggy's CTH build. But am thinking it was the current BOM values._

 

I think the values tweaked for e12, a long time ago, were R13s (1.5k now) & R14/R15 (100k now) and maybe R7E/R9E (2k now)... So you should let us know your values for these. Think some builds may working fine with variances in these tho (.5k for the 1k->2ks).


----------



## wiatrob

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_I think the values tweaked for e12, a long time ago, were R13s (1.5k now) & R14/R15 (100k now) and maybe R7E/R9E (2k now)... So you should let us know your values for these. Think some builds may working fine with variances in these tho (.5k for the 1k->2ks)._

 

Correct - the most germane would be checking R4E (originally 1.5K now 2K) and R7E/R9E (changed to 2K before the first BoM release). 

 As mentioned a pic would help, showing how the sonicaps are mounted (I haven't tombstoned, preferring to leave my leads the same length.

 I suspect R4E (which may be 1.5k - fine with Bom caps and Wimas, but more sensitive to longer/uneven cap leg lengths) to 2K may solve the e12 trips...


----------



## smeggy

I'll have a look later and check them, I think I have all the values needed if they need changing and I'll shorten/even length the cap wires.


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Switched it down to 6v, plugged in the 6n6p and off it flew... nice bass increase over the Siemens and the rest sounds damn nice too. I'm very happy with it especially considering how cheap these tubes are. I like how this sounds a lot 
	

	
	
		
		

		
			



_

 

 Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I swapped the caps over to Sonicaps thanks to waitrob and it's going great. < snip >
 It's a great all-rounder and does nothing wrong. The Beta has the most solid sound of the three, with thunderous bass and tight as a drum and very smooth. The EHHA isn't as solid or thundering in the lower regions but has a delightful sense of air and separation with nice atmosphere and the CTH is the more aggressive of them with the 6n6p tube and upgraded caps (tuned that way on purpose). 
 It's a sparkling amp with great bite and clarity and very appealing all round sound. It's hard for me to say one is better than the other because they each have distinct strengths and there's no way I'd say the CTH was outclassed, just a different flavor depending on what I'm listening to. < snip >_

 

Smeggy, I didn't catch which cans you are using... We know there are tube / cans synergies as well as the ever-present sound & music taste influences.

 Having just rec'd a pair of broken-in K701s I find those cans do not mate well w/my Siemens 12au7 equiv (a great D2000s match)... IMO that Siemens emphasizes the areas my K701s already do well - BB 6dj8 is a much better match (& probably 6n6p, de-emphasized mids/punchier bass). 

 Obvious, but reiterating its a good idea for people to search through the CTH threads for tube/cans combos & may need to experiment a bit to get the sound they want.


----------



## smeggy

My cans are custom made orthodynamics (Fostex T50RP) and they show the flavor of each amp very nicely. I don't have any ;standard' cans aside from the K1000. All the others are non standard/heavily modded so not much use as a reference point for anyone else.


----------



## wiatrob

Well, 'cept for my modded YH-3s


----------



## Forte

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Having just rec'd a pair of broken-in K701s I find those cans do not mate well w/my Siemens 12au7 equiv (a great D2000s match)... IMO that Siemens emphasizes the areas my K701s already do well - BB 6dj8 is a much better match (& probably 6n6p, de-emphasized mids/punchier bass). _

 


 Can confirm the K701 and 6n6p combo works a treat, by far my favorite tube for these cans, really brings out there best.


----------



## smeggy

Cool, it's a great tube for the CTH!


----------



## wiatrob

I'll give the 6N6 another shot this week - since I seem to have misplaced my 6C7 and Siemens Chrome _grumble grumble too many tubes to roll_...


----------



## cfcubed

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_So yesterday, I did a mini shootout between two of my favorite 12AU7 variants. Both tubes were made by CBS/Hytron ~ the 7730 & the 7318. <snip >

 There is a lot of similarity between the two tubes. Both produce an enormous amount of detail, with the 7730 winning out a bit, especially with harmonics produced with stringed instruments. It's the only tube I've listened to where you can really hear a lifelike reproduction of the harmonics that are produced from a steel fingerpick breaking contact with a well tuned steel string. It also is able to reproduce the sound of harmonics that are created between the fret and the string with more realism than I have heard elsewhere. That being said, the 7318 does a really good job as well, but not like the 7730 (at least through DT880's).

 But, after listening to to several albums with both tubes, my overall favorite ends up being the 7318 because of what my ears perceive to be a flatter response across the entire frequency spectrum. It seems like the 7730 dips a bit somewhere in the lower mids, and doesn't have as much bass extension when compared to the 7318.

 Both tubes are amazing though..._

 

Although I've a boatload of CTH tubes, I've been on the look out for these 7730s or 7318s... Unless I'm missing something they seem quite rare.

 Anyway, there's a pair on fleabay now & though I'm loath to spend another $10+ per tube I may not be able to help myself
	

	
	
		
		

		
		
	


	




 From what TimJo says it could be worthwhile. 

 As I only need one of the pair, if they don't go for too much wondering if anyone would want to 50/50 them (with one of us bouncing out the extra tube to the other). If so let's do the PM thing.


----------



## wiatrob

Boomy gave me a 6H1N-EB (6N1p-EV) at the meet...anybody tried 'em? I plopped it in and fired it up...Cool looking filament...sounds nice


----------



## sachu

yep..they are nice but noisier than most other tubes i have tried on the CTH.

 Favourite so far has been the 6H30-DR, Siemens E82CC and the 6CG7.

 The 6CG7 is just totally amazing. The CTH is a detail junkie yet with that lush midrange and a tight bottom end with that tube in it.


----------



## smeggy

nice, there seems to be an endless supply of cool tubes to try. My collection is quite small compared to many here.


----------



## wiatrob

The one I have is quiet (at work...) Will listen again at home...


----------



## keyid

listening to some zeppelin with 6GU7 - loads of details and seems mix well with HF2.


----------



## wiatrob

I CAN'T FIND MY 6CG7! Argh, the tube gremlins have made off with it and my Siemens chrome plate... I KNOW none of my co-workers took 'em...

 too many tubes, I need a bigger Pelican case...

 <rant off>


----------



## barleyguy

Hi. I'm a newbie to the CTH (via Wiatrob), and to tubes in general. Just wanted to mention what I've got so far, and what I've ordered...

 The three tubes I've got so far:

 GE 5814: The word for this one would be "analytical". It does great with high bitrate (or lossless) acoustic tracks. Would be a good tube for classical listeners. Would also be good for mixing or analysis. With distortion or anything 192K or lower, it is a bit dry, IMO. (Possibly just being "accurate" in those cases)

 Mullard 12AU7: Decent, quiet, middle of the range. Good at all genres, but not particularly thick or punchy.

 TungSol 12AU7: My favorite of the 3. Detailed, punchy, warm, thick. Can be slightly sibilant if it is given sibilant tracks, such as vocalists burning their S's. But overall a wonderful tube.

 The two I've ordered from ebay:

 RCA Cleartop 6FQ7 

 Amperex Bugle Boy 6DJ8/ECC88 (Medium white logo, 1961)

 I'll let you know what I think of those as well. Any suggestions on other ones to try? Or alternate opinions on these?


----------



## wiatrob

Barleyguy -

 I hate to tell you what you already know, but take a gander through tis thread there are quite a few tube reviews, I'm sure you can come up with a few more additions...


----------



## cfcubed

Quote:


  Originally Posted by *barleyguy* /img/forum/go_quote.gif 
_I'll let you know what I think of those as well. Any suggestions on other ones to try? Or alternate opinions on these?_

 

Although as Bill said its best/most thorough to go though this thread & the "A Very..." thread (post-proto), I'll summarize my thoughts based on my cans & listening preferences FWIW. 

 You're discovering/entering an area the CTH supports uniquely well - Tailoring its sound to its surrounding equipment & your listening tastes at the moment. Tube rolling across a broad range of tubes without adjusting pots/using a DMM are key advantages.

 Think you've got a good selection going there already esp. if elements of your usage are constant (cans, music genre). My CTH tubes seem to fall into 3 categories emphasizing differing things:
Punchy tubes w/lots of bass - 6dj8, 6922 Amperexes do this for me (BB, PQs). Great for rock esp w/DT880s (using 6922 PQ now).
Tubes that "excite" midrange, better exposing details you may not have noticed - Siemens ECC82 "chrome plate" for me, 5814a triple mica for keyid (I think). Great for hearing new things in my collection w/any cans & music.
Neutral sounding that do not do the above, giving "honest" rendition of music as it was intended but w/great detail. - Amperex 8416
_*Edit: Oops.. holland is correct,* I was thinking about the cleartop... I too find 8416 much like 6922, 6dj8 w/perhaps better detail? Neutral/flat sounding tubes do not stay long in my CTH, I easily forget their names
	

	
	
		
		

		
			



_

 There are certainly less expensive alternatives to the above like RCA Cleartop, generic non-BB/non-PQ Amperex, etc. as you can read in this thread (and like you already own


----------



## holland

^ that's interesting. 8416 seems almost identical the the 6dj8 a-frames I have. But then again, it's so hard to compare details without side by side identical configurations.

 My favorites by far are the 6CG7, 6FQ7, 6GU7 tubes. I'm using the 6GU7 now. Clear, detailed, and good extension on both ends.

 Some like the Tungsram ECC82, but I find the highs very colored.


----------



## barleyguy

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_^ that's interesting. 8416 seems almost identical the the 6dj8 a-frames I have. But then again, it's so hard to compare details without side by side identical configurations.

 My favorites by far are the 6CG7, 6FQ7, 6GU7 tubes. I'm using the 6GU7 now. Clear, detailed, and good extension on both ends.

 Some like the Tungsram ECC82, but I find the highs very colored._

 

Any particular brand of 6GU7 that's better? Those seem to be very inexpensive, just a couple dollars apiece. Seems like it should be worth getting.

 I've decided the TungSol is a bit fatiguing. It's still my funnest tube, but my ears get tired after a couple of hours listening to it. The Mullard isn't as exciting, but it's totally non-fatiguing. So what I'd love to find is a tube that's got the impact of the TungSol, but is non-fatiguing like the Mullard. I'm not sure if that's inherently impossible, but there should be one with a nice balance. I'm hoping the ebay tubes will be here in the next couple of days, and I'll take it from there. 
	

	
	
		
		

		
		
	


	




 Random question: Someone earlier in this thread mentioned the CTH being their favorite speaker amp. Is it possible to just split off the connector and hook it to a pair of speakers, without any impedance problems? I'm not sure if I'd risk doing that, but curious.

 (BTW, thanks for the help tweaking this great little amp.)


----------



## wiatrob

I like the Raytheon 6GU7, also have tried RCA...


----------



## holland

I don't know. I bought a bunch off fleabay. It's in various boxes, but I can't make out all the tube markings. The one I currently use says 6GU7 USA on the top of the tube. It looks like it might be an RCA.


----------



## barleyguy

I got the Amperex BB 6DJ8 and the RCA Cleartop 6FQ7 today.

 The Amperex, as people have noted already, is very good. Great detail, good low end, and very balanced. Just sounds "right". A tiny bit noisy, but not terrible. The noise isn't really noticeable once the music is playing. Caught myself tapping my foot while testing this one. It will get lots more use.

 The Cleartop (after straightening the pins to fix a buzz problem) is working great too. It seems to have great detail and a lot of punch, even at low volume levels. Beautiful soundstage also. This tube seems to be a keeper as well.

 I also ordered a 6GU7. 
	

	
	
		
		

		
		
	


	




 (I feel a little late to the party, but am having fun with rolling tubes. Pardon the newbie enthusiasm.)


----------



## smeggy

Well bum, now I'm back home again I swapped out the sonicaps for the small block wimas and stuck a ecc88 BB in it and it's still tripping 
	

	
	
		
		

		
		
	


	




 I'll see if I can get a hi-res pic of the area. I can't tell what resistors are in there as they are the colored ring types.

 The Bugle boy is also very nice!


----------



## smeggy

Ok, had enough. How do I bypass or disable the e12?

 Hah, so while messing with it I decided to try the original EHHA 6GM8/ECC86 tubes and they sound very nice too, bitingly nice with good bass.


----------



## sachu

Umm Smeggy..Don't think you should be using the 6GM8 tubes with the CTH.

 The 6GM8s are only rated at 30 volts on the plates. The CTH is designed at 80 volts on teh plates.


----------



## wiatrob

Smeggy,

 Something is up if you are having e12 trips with the latest BoM e12 resistors - did they start when you put the Sonicaps in? Perhaps post the pic to the main CTH thread and we'll troubleshoot there...


----------



## smeggy

yes, it was stable until the sonicaps but they're out now


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_yes, it was stable until the sonicaps but they're out now_

 

Did you tombstone them? I have built two builds with Sonicaps without issue (I don't tombstone but with the latest e12 resistors even long leaded boutique caps should be stable...)

 Barleyguy's is one...


----------



## smeggy

Ok, well not sure what's going on but it's working properly now 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Umm Smeggy..Don't think you should be using the 6GM8 tubes with the CTH.

 The 6GM8s are only rated at 30 volts on the plates. The CTH is designed at 80 volts on teh plates._

 

Ya know what? It's worth burning the tubes out prematurely for this, it sounds almost as good as the EHHA with this tube. Wonder if it'll sound even better with a 6h30..


----------



## wiatrob

How much current does your wall wart supply? You could get a way for a little listen with a 6H30 if it's >1 amp.


----------



## sachu

Yeah he is using the Power supply I use..which is a 1.67A one. 

 Go ahead and try it in the CTH smeggy. I am quite sure you will like it.


----------



## smeggy

I'm really enjoying the 6GM8 tube, it has the best top of any amp I've heard (for my tastes etc.) it's extremely airy and detailed with outstanding separation.I won't be able to try the 6h30 until tomorrow at work. However, the 6h30 doesn't match the 6GM8s top end in the EHHA for me so it'll be interesting how it fares in the CTH. The overall sonic balance is also spot on and the whole thing sounds more open and spacious.

 It does easily beat the 6n6p which was my previous fave!
 I went through all the tubes here last night and the 6GM8 is the easy winner.


----------



## smeggy

heh, this is nice. The 6h30 works but runs damn hot. I'm glad I upgraded the sinks 
	

	
	
		
		

		
		
	


	




 it has even better bass than the others, the 6GM8 still has best detail and air but this sounds great too.


----------



## smeggy

ok, continuing my dumb quest for tubey goodness, if I use an octal/noval adapter is there any reason not to try the 6F8G? Spec-wise it looks fine to my untrained eye but thought I'd ask here. I can get the tube cheap so wanna try it if I can.


----------



## Forte

Finally managed to find a 1.5amp power supply to replace the 1amp supply I have been using, now plan to upgrade so I can try 6h30 and others.

 Apart from upgrading L1H, L2H and putting a heatsink on the ICH are there any other changes recommended? A quick search didn't find anything but I thought a few P/S cap changes were mentioned somewhere?


----------



## cfcubed

Forte - You've mentioned all the load carrying/safety bits, anything more would be for noise/sound reasons. I'll run National's Simple tool later and edit this if need be, but we know its not the best for those concerns (your ears are). 

 So you could give it a go w/the changes you've mentioned & see what you hear. If you notice any new noise/hum running 1A+ heater tubes, raising C3H to 470uf+ and possibly C1H/C2H to 180uf would quell that.


----------



## Forte

Thanks for that.

 Just found some posts in the main CTH thread where this was discussed previously, several different values were suggested for C1/2H, will have a re-read of that thread in the morning. Already have C3H @470uf.


----------



## wiatrob

Forte,

 Holland and I have higher value C1H/C2H (although I have run with the stock BoM values in the loaner build and didn't notice any difference in noise...)


----------



## runeight

Gents, I am listening to a CTH for the first time. Wiatrob leant me one of his while I'm here in Denver. I am fortunate to be able to use the AD2000s that were gifted to me by many of you.

 Right now I'm listening to Bass Test by Chemical Brothers. This amp is startlingly good at delivering the bass on this track. I'm very impressed with it, although I probably can't say that too many times.

 It handles classical, rock, techno, everything pretty darn well. This using Bill's Tungsram ECC82.

 Nice work cfcubed. 
	

	
	
		
		

		
		
	


	




 This amp, as small as it is for a tube rolling hybrid, should be in more hands than it currently is. Objectively speaking.


----------



## Forte

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Forte,

 Holland and I have higher value C1H/C2H (although I have run with the stock BoM values in the loaner build and didn't notice any difference in noise...)_

 

Have been reading your posts in the main thread, which parts do you recommend for upgrading L1H/L2H and did you stick to the 3.3uh/220uh values?



  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I am listening to a CTH for the first time. _

 







 Welcome to the party!


----------



## wiatrob

I have upgraded L1H, but only to a 1 Amp version, same value: 

Digi-Key - 732-1429-ND (Wurth Electronics Inc - 7447020)


----------



## smeggy

heh, well it won't be quite so small with one of these on it 
	

	
	
		
		

		
		
	


	









 Mwahahaha!!


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_heh, well it won't be quite so small with one of these on it 
	

	
	
		
		

		
		
	


	









 Mwahahaha!!_

 


 I honestly can't wait to try that monster on my itty bitty CTH


----------



## cfcubed

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_ <snip> This amp is startlingly good at delivering the bass on this track. I'm very impressed with it, although I probably can't say that too many times._

 

It's nice reading the good things said by everyone about the amp, even better that you could hear one for yourself to see what all the fuss is about
	

	
	
		
		

		
		
	


	




 We all really accomplished a lot with this design. I enjoy mine at least 3 hrs each workday & am finding myself so satisfied w/it I'm not really compelled to build bigger/"better" like an EHHA or β22. Least not for a while anyway. But we all know us DIYers can't stop building for too long
	

	
	
		
		

		
		
	


	




 smeggy & sachu - Some will stop at nothing to test the limits. Nice though that we've not reached them yet


----------



## smeggy

The CTH is good enough to easily hold it's own in such grand company. As to testing limits, I just thought it would be fun to step outside the normal tubesets for these and see how the bigger old tubes compare, especially as the 6F8G has such a good rep for sound.


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I just thought it would be fun to step outside the normal tubesets for these and see how the bigger old tubes compare_

 

Good thought. Would be cool to see & hear about one of those beasts in a CTH. IIRC runeight lightheartedly mentioned octals when Bill & I were proofing non-6.3/12.6 heater support. 
 BTW, here's the work-in-progress tube sheet (green = proven to work, light-green = very likely to work, tubes w/mu/gain > 40 omitted as they don't work well):





 The design itself was/is really about testing limits... How many features & how much performance can be squeezed into a 3" x 5" space. 
 That its a clear standout in its class & competes well against the big boys is a plus too


----------



## smeggy

my mission is to find how big a tube I can strap to it before it topples over


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Switched it down to 6v, plugged in the 6n6p and off it flew... nice bass increase over the Siemens and the rest sounds damn nice too. I'm very happy with it especially considering how cheap these tubes are. I like how this sounds a lot 
	

	
	
		
		

		
		
	


	



 Big tube too, twice the size of the little E82CC and no heat or stability problems so far._

 

Smeggy - Speaking of big tubes, going back aways but been listening to the 6n6p you fired over & its growing on me
	

	
	
		
		

		
		
	


	




 Find it does what you say. Esp. good for cans that do not need "exciting" of mids/highs (e.g. DT880s & K701s when I had them).

 Seems to impart a bit more "tubey" character to the amp w/o giving anything up. IOW if people want their combo a bit less bright w/more punchy bass 6n6p deserves a listen. Heater current is within spec'd part limits (<= 800ma) if not the conservative/recommended limit (<= 600ma). Been running it a while w/stock parts - just a little *(edit: part/half of?)* heatsink added to LM2595. Nice.


----------



## barleyguy

Just a quick question for anybody that may have tried it...

 I got tired of having IEM's in my ears 5 hours a day, so yesterday I stopped by Listen Up and bought some Grado SR225i headphones. I haven't found the perfect tube for them yet. The Amperex Bugle Boy 6DJ8 is perfect with my X10 IEM's, like pure synergy. But it's a little bit bright and edgy with the Grados. The Mullard 12AU7 has perfect frequency balance with the Grados, but it's rolled off on the highs and lows. I think the TungSol 12AU7 is the closest I've found, but it has less bass than the Bugle Boy.

 I'll keep experimenting. If anyone here has tried the CTH with Grados, what tube is your favorite?

 Thanks.


----------



## wiatrob

Hmm, I mostly only listen with Grados. 

 Let's see:

 I have been liking the 6n6P a lot lately (I've been stuck on 6.3 volter's lately)

 6CG7 Clear Top has seen a lot of use, as has the Raytheon 6GU7.

 I just put my Amperex 8416 in to see how it fares with the RS-1s...


----------



## barleyguy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Hmm, I mostly only listen with Grados. 

 Let's see:

 I have been liking the 6n6P a lot lately (I've been stuck on 6.3 volter's lately)

 6CG7 Clear Top has seen a lot of use, as has the Raytheon 6GU7.

 I just put my Amperex 8416 in to see how it fares with the RS-1s..._

 

Thanks. I've got a 6GU7 in the mail, so I'll try that. I requested a Raytheon, but it was one of those "$4.00, brands may vary" things, so I'll see what shows up.

 Is it safe to try a 6n6P? (Wiatrob, you know my exact build.)

 (Also cfcubed, the tubes.jpg above doesn't have the 6n6p listed. might want to add that in a future revision, unless you left it off intentionally because of draw.)


----------



## smeggy

Another tube which has nice bass and a smoother, less bright overall sound is the 6h30. Some bits will need upgrading for this tube, like a cap and heatsinking along with a greater than 1A supply but it's a really nice relaxed and full bodied sound I think would work very well for the Grados given their spiky response.

 It does run the amp hotter than all other tubes I've tried though it seems very stable given adequate ventilation.

 I think some of these tubes were left off because it wouldn't be a totally good idea to run them on a standard bom build. We're running some of these out of ideal spec for the CTH. My 6gm8 tube is way over voltage for example and the 6h30 needs a buload of current and bigger sinks. The 6n6p is apparently running close to it's lower limit.

 I try all these things because for the most part I don't know any better and only find out I'm doing bad things after I do them 
	

	
	
		
		

		
		
	


	




 Anyway, the big 6F8G beasty is on it's way and though it needs an adapter to fit the CTH it'll be interesting to see how it compares to it's miniature brethren.


----------



## barleyguy

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Another tube which has nice bass and a smoother, less bright overall sound is the 6h30. Some bits will need upgrading for this tube, like a cap and heatsinking along with a greater than 1A supply but it's a really nice relaxed and full bodied sound I think would work very well for the Grados given their spiky response.

 It does run the amp hotter than all other tubes I've tried though it seems very stable given adequate ventilation.

 I think some of these tubes were left off because it wouldn't be a totally good idea to run them on a standard bom build. We're running some of these out of ideal spec for the CTH. My 6gm8 tube is way over voltage for example and the 6h30 needs a buload of current and bigger sinks. The 6n6p is apparently running close to it's lower limit.

 I try all these things because for the most part I don't know any better and only find out I'm doing bad things after I do them 
	

	
	
		
		

		
		
	


	




 Anyway, the big 6F8G beasty is on it's way and though it needs an adapter to fit the CTH it'll be interesting to see how it compares to it's miniature brethren._

 

My CTH is Sonicap Gen 2 (200V), the heatsink coupled to a metal case with a perforated top, and a 1.6 amp (40VA) power supply. I'm guessing it should be solid for larger tubes. Is that enough for the 6n6p and the 6h30? I probably should be more careful than some of you because I didn't build this. Wiatrob, I'm sure you'd love to hear from me if I melted it. 
	

	
	
		
		

		
		
	


	




 I got the 6GU7 last night. It's an RCA. I quite like it. The soundstage isn't as surreal as the Bugle Boy, but in all other aspects it sounds just as good, and it's less sibilant on the Grados. So that's a keeper. Also, it's brand new old stock, and it was only $4. I'm thinking about ordering a couple more as spares.

 I'm very curious to read how the beastie tube will sound in the CTH.


----------



## Ynis Avalach

Isn't the 12BH7A run as a 12V tube in the CTH? (heater in series isn't it?)
 Greetz Ava


----------



## keyid

yea I also like the 6GU7 with grados, I read somewhere they are 6v version of 12BH7. I got some assorted 6dj8's and 1960's black plate raytheon 6CG7 on order.


----------



## wiatrob

Quote:


  Originally Posted by *barleyguy* /img/forum/go_quote.gif 
_My CTH is Sonicap Gen 2 (200V), the heatsink coupled to a metal case with a perforated top, and a 1.6 amp (40VA) power supply. I'm guessing it should be solid for larger tubes. Is that enough for the 6n6p and the 6h30? I probably should be more careful than some of you because I didn't build this. Wiatrob, I'm sure you'd love to hear from me if I melted it. 
	

	
	
		
		

		
			




_

 

The one upgrade i'd make for safety is a small heatsink on the switching reg. I can pop one on for you if you'd like...

 -bill


----------



## wiatrob

Quote:


  Originally Posted by *Ynis Avalach* /img/forum/go_quote.gif 
_Isn't the 12BH7A run as a 12V tube in the CTH? (heater in series isn't it?)
 Greetz Ava_

 

Yes, it's not so stable with 6.3V


----------



## barleyguy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_The one upgrade i'd make for safety is a small heatsink on the switching reg. I can pop one on for you if you'd like...

 -bill_

 

Thanks. 
	

	
	
		
		

		
		
	


	




 That would be way cool. Whenever you have time is good; I have no practical reason to be in a hurry. I do figure I'll be tweaking with this a lot more though. I've been meaning to PM you about any extra tubes too.


----------



## cfcubed

Yep, CTH has no center-tap heater connection - so it powers the "series" heater spec. So tubes that say 6.3v parallel / 12.6v series are run in series in it. This is good because the 12.6v series heater spec for such tubes is usu half the current draw of running them w/6.3v parallel heater.

 WRT > 600ma heater draws & std BoM CTH, the heater reg itself is rated up to 1A continuous & if run > 600ma continuous should have some form of heatsink. AFAIR, the rate-limiting factor in std BoM CTH heater supply are the 800ma-rated chokes. Not sure about their longevity when run continuously @ or close to their max rating, would need to do some research there. I'm comfortable doing so because I know what/how to fix if trouble was to happen in the long-term.


----------



## wiatrob

Barleyguy,

 Your CTH has 1A chokes... PM me to arrange for an upgrade at your convenience...


----------



## Ynis Avalach

Well you could always try to install the LM2596, which max rating is at 3A, if you have larger chokes, but two of the 2596's pins are switched. I think no. 1 and 2 if I remember correctly.
 Ava


----------



## wiatrob

The switcher is good for an amp, no problem - you'd need a big sink on the 2596 and switching pins would not be fun or practical...


----------



## TzeYang

btw guys, I'm not sure if this has been answered before but wouldn't the CTH be fit for a three channel operation by using VG as a ground reference for the servos and input and the buffer output for the OG?


----------



## keyid

found my new fav tube, the 6CG7 Raytheon Black plate D getter. It mixes characteristics of many tubes I like, its punchy like 6n6p, carries alot of weight like mullard 4003, also sweet mids like siemens E82CC / rca jan 5814a, quite detailed like 6GU7 but doesn't sound airy like siemens 5418a. Love this tube with hf-2.


----------



## smeggy

Dunno what make/type sachu sent over but yes, the 6CG7 does mix the best aspects of many other tubes and is doing very nicely in the CTH at work.


----------



## cfcubed

Quote:


  Originally Posted by *barleyguy* /img/forum/go_quote.gif 
_Also cfcubed, the tubes.jpg above doesn't have the 6n6p listed. might want to add that in a future revision, unless you left it off intentionally because of draw._

 

Yes, heater draw was one of the criteria as was pin-out, mu(gain) < 40 and, to some extent, operating points. The white rows are ones that wiatrob & I haven't screened yet.

 After looking deeper into the current rating WRT our heater chokes, going to stick w/the <= 600ma draw recommendation when using std BoM parts. It comes down to heat/ventilation. Although I believe we are "good" through the current max spec'd for the parts, because they stay < 105 C (< 35 C rise over ambient in-case temps, their typical max rating), we like to see some headroom.

 So unless one was able to fix/repair an issue, however unlikely, from running 800ma parts @ 800ma, would recommend going with the higher-rated parts (& small heatsink) Bill talks about here if driving tubes w/> 600ma heater.

 BTW The nice perforated lids Bill supplies w/the kits support good ventilation.


----------



## smeggy

Is there a good tube with about 50-100% more gain than standard that can run happily with the CTH? I have some phones that need a butload of extra gain to overcome their extreme inefficiency. 

 Wharfedale Isodynamic rated at 10wpc for instance. We seem to have sufficient power, not enough gain.


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Is there a good tube with about 50-100% more gain than standard that can run happily with the CTH?_

 

Someone around here (Bill?) tried the common 12AT7 (gain:54) & wasn't happy w/it *but* it may have been because it had too much gain for his cans.


----------



## smeggy

12ay7 mu40?


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_12ay7 mu40?_

 

Sure, it should work & be louder. And 40x is not _that _much more than some of the 6-volters we've been using (e.g. 6922 = 33x), so I'd think CTH would be fine w/it for your purposes.

 BTW much of the data in that tubes jpg I posted was from here


----------



## holland

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_ After looking deeper into the current rating WRT our heater chokes, going to stick w/the <= 600ma draw recommendation when using std BoM parts. It comes down to heat/ventilation. Although I believe we are "good" through the current max spec'd for the parts, because they stay < 105 C (< 35 C rise over ambient in-case temps, their typical max rating), we like to see some headroom._

 

I modded mine to support greater current, but only used it a bit. The heat was just too much for my case even with holes vented and the reg case mounted. The case got very warm running 6N6P. Even though the internals weren't too warm, over time the casing will increase the internal ambient. So, I'm back to 6CG7 and 6GU7s. It does what I need and I don't have an itch to scratch at the moment.


----------



## smeggy

that's why I run mine out of a case, nice and cool. 

 One ugly thing has raised it's head again, random e12 trips. No idea why it's doing it but it is. Pain in the ass.


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_One ugly thing has raised it's head again, random e12 trips. No idea why it's doing it but it is. Pain in the ass._

 

I assume you've reviewed the component values Bill & I mentioned in our posts when you 1st raised this issue (if not, please do compare them to current BoM).... Note: The CTH ε12 differs from the reference design (mostly in component values).

 Since you are using your CTH as a tube testbed of sorts you could consider reducing the sensitivity / reducing the speed of its ε12 even further - from CTH site:

_Notice that R1E and R2E are changed from 10kΩ to (33kΩ) and that R4E is changed from 1kΩ to (2kΩ). The purpose of these changes is to make the CTH ε12 less sensitive and a bit slower._

 Guessing 50k R1E & R2E and 3k R4E? This is akin to raising the deductible on your insurance policy, which is much better than going w/o one. 
_Seems _like the cans you like to drive could tolerate more DC flux than the default CTH ε12 implementation allows.


----------



## wiatrob

I actually had my SOHA II ε12values fairly far up there (the CTH shares the simplified circuit with the 'II) t-Think I even might have gone to 4K R4E briefly. You can always (and maybe _should_) check the dc offset values at the output if you change the values past the current reccomendation.


----------



## smeggy

Thanks. I'll look into it further. I think it has the current correct set of parts but it's hard to verify as the resistors don't have printed values on them. Just the code bands which I don't know how to read.

 I do have some 2k and 51k resistors here so I can swap those out to make it less annoying once I slap the meter on it to check. Most of my phones are less sensitive and very robust designs so I won't worry too much and I think I'll end up with a number of odd tubes to try. 

 It's actually fun having it as an open testbed.


----------



## barleyguy

Quick question - Would a CEI German 7119 E182CC work (with the heatsink and 1A chokes etc)? It is listed as compatible with the 6n6p. I was thinking a German tube may sound better than a Russian Sovtek, and there's one available locally (Denver). If it'll work, I'm going to get one and try it out.


----------



## cfcubed

@ barleyguy - The E182CC looks to have the wrong / incompatible pin-out. 

 @ wiatrob - Yes, good point metering offset to see _why_ e12 is tripping.

 @ smeggy - Here is a cute resistor calc app.


----------



## smeggy

Thanks, that's a cool little app


----------



## wiatrob

I'm too lazy to learn, I use the Ohmmeter


----------



## smeggy

I was looking over Alexs' site and didn't see anything about changing gain, is there something I missed as it's usually in the parts list options. Would a 10k pot help or anything else you can think of aside from tubes? I'll be using hi gain tubes for dumb phones but my fave tubes are lower gain and I still want a bit more headroom.


----------



## holland

Pot won't make a difference.

 Changing gain would be adding negative feedback. I don't recall the circuit at this point, and am too lazy to look.  You can put a resistor divider on the input and/or utilize a pot shunt with larger values. That doesn't change gain though, only weakens the input signal more so the gain would bring it up to more tolerable ranges.

 For CTH, gain is directly related to the tube. If I recall the circuit properly, and you bump the input resistor up to around 10K, you should be able to feed back the output to the input via a 100K resistor (or larger). The output from the tube should be inverting and the buffer is non-inverting.

 Give it a try or yell at me for even broaching this.


----------



## wiatrob

Or you could attenuate the signal by upping the value of the output resistor...


----------



## cfcubed

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Or you could attenuate the signal by upping the value of the output resistor..._

 

Think smeggy is going for more gain, so shorting the output resistors (R18) positions would help. 

 As holland says "for CTH, gain is directly related to the tube." and we introduced the output resistors to simulate reduced gain for more pot range w/sensitive cans, higher mu tubes, etc.


----------



## smeggy

Yup, more gain needed. Anyway, checked the e12 values and they are what they should be. Oddly enough with a 6h30 it didn't trip at all, nor with a bugle boy 6gm8? EHHA tube. It was tripping with the 6n6p, 6cg7 another 6gm8, ecc82 and ecc86.

 Very odd so not sure what's going n there. Anyway, the BB 6gm8 is a little louder than the others and not quite so bad even though it's the wrong tube type.

 Wonder that it'll make of the 6f8g or 12sn7.. 
	

	
	
		
		

		
		
	


	




 ok, spoke too soon, e12 just tripped. I wonder if it's my office supply.

 BTW, which ones are the output resistors I should remove/bridge?


----------



## tacitapproval

R18


----------



## smeggy

thanks 
	

	
	
		
		

		
			





 Just bridged one of them, yup, that'll do necely


----------



## keyid

might want to put sockets on them, in case you use different phones.


----------



## smeggy

My phones range from inefficient to extremely inefficient, but yes, sockets will be useful


----------



## wiatrob

The design of the CTH (those pricey CRDs) should isolate you from trips caused by power supply voltage fluctuations...


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Just bridged one of them, yup, that'll do necely 
	

	
	
		
		

		
		
	


	


_

 

Yes, with what I've heard you've driven/are driving with this little power-house, you don't need no stinkin' output resistors
	

	
	
		
		

		
		
	


	



 As suggested, you _could_ SIP-socket the R18s if you had SIPs. If not, if you find pot range too limited down the road w/some cans you'll know where to poke around.

 BTW, be careful anytime you perform surgery on these. It's quite tight & shorts can cause bad things to happen.

 From the CTH site:


----------



## smeggy

heh, yeah I noticed that. 18L is easy to get to , 18R on the other hand is a bit of a squeeze like the e12 pair in there.

 Sachu now has a set of the same original wharfedale isodynamics as me, even he had no idea how inefficient they really were. People think we exaggerate with these, nope, they really are that bad. 
	

	
	
		
		

		
		
	


	




 Tried the wharfeys, decent levels when bridged at 3 o'clock, 5 is max so I may actually be able to use them


----------



## smeggy

Surgery over and the patient is now in stable condition, recuperating with some soothing music 
	

	
	
		
		

		
		
	


	




 Thanks guys.

 I'm almost afraid to say this, but it seems to sound better without the output resistors as well as go a lot louder. Next I'll be believing in cables and cryo


----------



## TzeYang

nobody has any ideas of a 3 channel operation? (using TLE2426 output as GND reference for servo and input ground and the output of the ground buffer for output ground)

 It gives the CTH a pseudo differential drive.


----------



## wiatrob

TzeYang - answer form me is, 'I don't know...' Alex could comment, I know he's been busy again lately.

 My gut feeling is probably not, or it would already have been designed to do so, but that''s not the technical response.


----------



## wiatrob

Smeggy, any update on your e12 behavior?


----------



## smeggy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Smeggy, any update on your e12 behavior?_

 

Not really, it's baffling the crap out of me as sometimes it'll literally run all day with zero problems, other days it'll be tripping all day. I really don't know and can't nail down any particular situation that makes it unhappy except it's more vulnerable at work.


----------



## holland

Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_





 nobody has any ideas of a 3 channel operation? (using TLE2426 output as GND reference for servo and input ground and the output of the ground buffer for output ground)

 It gives the CTH a pseudo differential drive._

 

I don't think it'll work very well. The input stage needs to change, IMO. The operating point of the tube in particular if you move ground up, you lose 12V and you can't maintain the circuit as is. Floating the input ground, moves the input DC to 12V above real ground. To do it easily, you would put a cap on the input, but there are other ways to handle that without a cap and would need more B+.

 I'm not sure I understand the difference between your proposal and the current implementation. The current implementation has input ground to transformer ground (may be earth depending on transformer). Output ground driving the headphones is the buffered VG. The tube references real ground and since there needs to be an interstage cap anyway, the output buffer for L and R is shifted by VG allowing split rail operation of the diamond buffer and the servo shifting the output DC at the expense of output current (I think, not entirely sure right now).

 The only difference is really where the input ties to. In effect, it is already 3-channel as the headphone ground is actively driven and buffered from input ground, not passively tied together. The topology is not the same as the PPA, but it is an active ground.


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Not really, it's baffling the crap out of me as sometimes it'll literally run all day with zero problems, other days it'll be tripping all day. I really don't know and can't nail down any particular situation that makes it unhappy except it's more vulnerable at work._

 


 Odd. It shouldn't be tripping so much, anywhere. I have the ****tiest power at work, and don't get trips. Does this behavior happen with the same tube in the amp in both locations?

 If you're game, you might meter your power at work ( I made a plug to test lead adapter and plugged it in to see if there was a correlation between power fluctuations and e12 trips. It's a bit of work, but it seems that yours is the only one experiencing nuisance trips.

 PLease, anyone else experiencing these, please speak up!


----------



## barleyguy

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Not really, it's baffling the crap out of me as sometimes it'll literally run all day with zero problems, other days it'll be tripping all day. I really don't know and can't nail down any particular situation that makes it unhappy except it's more vulnerable at work._

 

Have you tried a different power supply / wall wart? I'm just a newbie, but it seems that with the discussion about dirty power, component values, etc., it would be worth trying a different power supply.


----------



## smeggy

I'll have to look around, it seems so random. I do love the wee thing though so I will persist.


----------



## barleyguy

I've been spending some quality time with the Russian 6n6p, after a small heatsink upgrade this weekend. The word for this one would be "impact". It has a tight low end, and listening to it is like having a kick drum in my head. And it's really really fast. The transients are crazy fast. It does have a little bit of high end roll off, probably starting at 12K or so. But it still has plenty of high end detail, just recessed a bit. For trance and rock (listened to REM, DJX2, Muse, and A Perfect Circle), it has an amazing amount of impact. Caught myself giggling while listening.

 Note: (for anyone who's not a regular to this thread) Running the 6n6p needs a 1 amp capable CTH. (1 amp chokes, 200V coupling caps, a 40 VA wall wart, and sufficient heat dissipation.)


----------



## smeggy

yep, the 6n6p is really good in the CTH as is the 6cg7 and 6h30. I think these are the best tubes for my tastes, I just got another 6h30 in the mail and it looks like a new tube (not NOS) and unfortunately it seems to be the most microphonic tube I've come across. I really need to get some dampers.


----------



## barleyguy

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_yep, the 6n6p is really good in the CTH as is the 6cg7 and 6h30. I think these are the best tubes for my tastes, I just got another 6h30 in the mail and it looks like a new tube (not NOS) and unfortunately it seems to be the most microphonic tube I've come across. I really need to get some dampers._

 

You could go for a 6h30-DR (the "Supertube"). It shouldn't need dampers because it has support bars up and down the length of the entire grid. The sound has the best low end detail of anything I've heard. That was my favorite of Wiatrob's tubes. Unfortunately, they are expensive.


----------



## smeggy

yeah, I have a set of 6h30pi Golds which are nice and quiet, but this one is really bad even though it's a Pi supertube.


----------



## barleyguy

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_yeah, I have a set of 6h30pi Golds which are nice and quiet, but this one is really bad even though it's a Pi supertube._

 

Strange. I thought the design of that one would prevent microphonics. I wonder if it had a rough trip from Russia or something.

 Oh, how did the beasty tube experiment work out?


----------



## smeggy

still waiting for the tube to arrive
 should be fun


----------



## wiatrob

Tube structure cannot prevent microphonics, but can help minimize it -I just flicked the 6H30 (heresy?!?!) on my CTH and it rattles - but it never makes noise when subjected to normal desktop vibration, plugging in cables, etc...


----------



## smeggy

this does. plug things in... zzzzzinggggg! touch anything on or near it...zzzzzzinggggg... it's a marvel of sensitivity 
	

	
	
		
		

		
		
	


	




 I'd say at least 5x worse than any other tube I have here.

 Anyway, in the great spirit of DIY I headed off to the local craft shop and bought a 2-part easymold silicon putty mix to make my own tube dampers with. 20 min set time after mixing and good for 400 deg F. Supposedly strong and flexible


----------



## wiatrob

I hope they don't _SQUEEEEEZE _the life out of your tubes! Please post pics in the DIY build thread!


----------



## smeggy

Pah!

 the silicon putty makes nice dampers but that 6h30 is beyond fixing. even totally damped it's insides still ring like a bugger. I put it on the 6n6p and when flicked, it went from ting to tonk.

 I molded the stuff around a Starving student tube 19j8?!? whatever, nice sung fit on the bigger tubes


----------



## Forte

I have had limited success with tube dampers and microphonic tubes, they seem to lessen the ringing but not take it away. Have tried the thick silicone o'ring type as well as a couple of different types of Herbies tube dampers, Herbies do work better than the o'rings but only marginally.

 They do look cool though.


----------



## smeggy

Yeah, I never expected miracles seeing as most of what causes the ringing is internal where the damper can't reach. The best you can really expect is secondary damping. 

 A bit like damping a bell that's full of wind chimes


----------



## bada bing

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_So, after seeing a couple tubes were tried in CTH that had other than 6.3v & 12.6v heater and found to work & sound good, knew there was nothing keeping the design from *directly supporting more heater voltages*.

 Nothing but a few more resistors & a way to switch among them.

 Calculated (ideal) R3H values for various heater voltages:
*Votage / R3H (ideal)
 4.2v / 3.3k
 5.6v / 5.8k
 6.3v / 7.4k
 7v / 9.3k
 8.4v / 15.1k
 9.4v / 23.3k
 12.6v / <none>*

 Wiatrob was willing to test & confirm things & has done so using *4BQ7A, 5BQ7A, 7AU7 and 9AU7 *tubes. *This tweak further extends tube options in the CTH beyond 6.3v & 12.6v heated tubes.* So users of a CTH with this tweak have an even larger selection of tubes to choose from, probably finding some very good deals for tubes running at non-std heater voltages. 
Edit: So beyond the 6.3/12.6 tube list, this tweak should add those above, 7DJ8 and 8FQ7 and there are likely more overlooked (e.g. 6AU7, 6BQ7)

 The challenge is choosing which heater voltages you want & finding a SP#T switch to switch among them. We found a nice 1/2 inch dia one that can be configured for 2 -> 12 positions:





 Wiatrob can chime in w/more info, but I think it remains to be seen if this tweak can be squeezed into the BoM case._

 

Hey all
 My first post in the CTH threads.
 I finally got around to stuffing my CTH board and I went through this tweak thread to get the latest & greatest BOM updates before wiring it up. My C3h and R18's are updated. I'm considering doing the multiple heater voltage tweak with a twist. I "upgraded" to a chinese stepped attenuator for my volume, so I have my kit's 50k alps RK097 left over. Any good reason to not parallel the stereo sides together (25K impedance) and tie one side to the wiper (creating a variable 25k log taper resistor) and then use it as a continuously variable heater control ? Looking at the chart it appears the voltage response to resistance is close to logarithmic so the heater voltage response should be close to linear? I thought I'd measure the heater voltage over the pot's range and mark the knob's position on the faceplate for various tube families. I'm thinking of putting a ~7k resistor in series with the pot (in R3H position) to limit the minimum heater voltage to ~6 volts. It seems it will still need a switch to break the R3H leg for 12.6 volts ~ or is there a combination of R1H + R3H (with the variable resistance in series with R3H) that would make a switch unnecessary? Like increasing R1H a bit (say 10.5K) to allow the adjustment range to exceed 12.6volts by a bit with no switch.






 The potential advantages I'm wondering about -besides using tubes with oddball heater voltage requirements - would be the ability to tweak the heater voltage up or down on the fly and listen to the sound differences. It would be another step in making the CTH a truly universal test bed for tubes. It would be easy to add on a heater voltage display that would allow auditioning tubes with a range of heater voltages. It might add another interesting dimension to tube rolling. If the circuit can be made to behave quietly and be upgraded to greater current capacity, it could be an interesting addition to other tube amps. I'd love to see a ultra quiet, Bijou capable version of the circuit. 

 There is the risk of being overly aggressive with this heater knob and smoking heater filaments. Besides this risk, is anything horribly wrong with the plan, will it overstress or destabilize the heater switcher somehow? I don't understand the finer points of the switching regulator circuit, so there could easily be something stupid with the idea. If it will fly, can someone familiar with the details of the circuit do the calq's for R1h, R2h, R3h & 25K log variable resistor that will give a smooth, fairly linear adjustment from say 5.5 to 13.5 volts ?

 ???


----------



## cfcubed

I may be able to take a look at your continuously variable heater voltage values in the next couple days. BUT if you want info sooner you can go download National's SIMPLE app for the heater part & play around (or use algorithm in datasheet?).

 I also thought it might be interesting to try running some tubes @ slightly higher than rated heater voltages. IIRC some opinions around here seem positive for that.


----------



## Forte

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_So, after seeing a couple tubes were tried in CTH that had other than 6.3v & 12.6v heater and found to work & sound good, knew there was nothing keeping the design from *directly supporting more heater voltages*.

 Nothing but a few more resistors & a way to switch among them.

 Calculated (ideal) R3H values for various heater voltages:
*Votage / R3H (ideal)
 4.2v / 3.3k
 5.6v / 5.8k
 6.3v / 7.4k
 7v / 9.3k
 8.4v / 15.1k
 9.4v / 23.3k
 12.6v / <none>*

 So users of a CTH with this tweak have an even larger selection of tubes to choose from, probably finding some very good deals for tubes running at non-std heater voltages. _

 


 Since I will be placing a Mouser order soon for another project I am going to get the parts to do this mod. What is the minimum rating for the resistors, can I use 1/8w?
 Trying to keep the switch assembly as small as possible.


----------



## cfcubed

The heater setting resistors carry virtually no load so you can use 1/10s. Cheap metal films (much smaller than VD-RN55s) and Mouser 633-MRK112A rotary (w/633-AT433 knob) makes it the smallest we could come up with.


----------



## rds

CTH with Auricap coupling caps and 100 ohm Riken output resistors (can see one in the front right corner).


----------



## smeggy

I gotta fix mine, reading this makes me want to listen to it again.


----------



## forsakenrider

I've been listening to My CTH for a long time with the 8416 and I just went back to a 6dj8 Bugle Boy. I generally listen with Sextetts and I'm wondering what tube you guys have found to give the most bass. I find the 8416 to have quite a fast punch but after always listening to my k81's on my portable rig I'm missing a little bass at home.


----------



## keyid

does the 8416 and 6dj8 sound similar? I have couple 6dj8 but noisy and getting a 8416 next week. The bass on 6cg7 is pretty good but highs are lacking. The siemens 5814a bass goes deepest among my tubes.


----------



## smeggy

the strongest bass I'v gotten from the CTH is with the 6H30, the best sound overall was with a 6F8G.


----------



## adamus

for me, the 8416 is the most natural tube, good highs, clear mids and tight bass. 

 The bugle boys (6dj8) sound lovely, slightly looser bass, euphonic midrange and fluid highs. 

 The bugles to my ears sounds 'bassier', but i think its just down to less control.


----------



## cfcubed

I've many of the tubes talked about & find the Amperex 6922 PQ USA the best for strongest bass & great overall range. IOW not giving up anything whilst delivering strong tight bass.

 It's made DT880s my fav cans again & the bass is so good made me confirm that iPod's EQ is off a few times.

 I won't pay > $25 or so for a tube so it took a while to snag a nice NOS one off the bay.

 But thanks to TimJo & keyid I'm on the lookout for (CBS,Hytron) (7730,7318) & Siemens 5814a triple mica someday


----------



## cfcubed

Curious if anyone here has given a good Amperex 6922 PQ USA I mentioned a shot.... 

 I ask because I'm still loving it w/DT880s in the CTH (w/Sonicap Gen II couplers). So much so that I've not swapped the tube out since I posted.
 And enough that all my 2-ch Beta22 parts are still collecting dust on the bench (not much longer tho as winter's on its way).


----------



## rds

Yes, that was pretty much the only tube I used for the first 3 months owning my CTH (despite trying a bunch of other tubes I have on hand). I've recently started listening with a GE 8416a which I also think sounds fantastic.
 Both of these tubes have extremely low noise floor (for me), great extension, detail, and impact.


----------



## smeggy

Still haven't had time to get my CTH working again and I'm not entirely sure whats wrong with it either. Tonight I'll post what it's doing and see if we can nail down what's going on so I can get parts and get it going so we'll need plenty of thinking caps on tonight


----------



## wiatrob

Did we ever come up with a definitive tweak for lowering tube noise with very low impedance 'cans (iems). Increasing the output resistor value was a proposed solution, correct?


----------



## tacitapproval

That and raising C3H to 330uF. This mitigates tube noise with iems to low levels, but does not completely eliminate it, at least in my case.


----------



## barleyguy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Did we ever come up with a definitive tweak for lowering tube noise with very low impedance 'cans (iems). Increasing the output resistor value was a proposed solution, correct?_

 

Isn't there a trade off on noise versus power with the output resistor? That's why I haven't wanted to go that direction. I'd hate to underpower the orthos in order to make the IEM's quiet.

 Would the C3H change help the noise without changing the power output?

 (Congrats on your 1000th post BTW.)


----------



## aphexii

Just out of curiosity, what has the average build been running people? $100-120 range?


----------



## bada bing

The kit prices are on the Spuce Canyon page:
Options

 I'd plan on about $200ish total for a build with transformer, perf'd top, a couple cheaper tubes to roll and maybe a cap upgrade. I built mine with the longer hammond 1602 case, perf'd top and cheap Ebay stepped attenuator. I'd recommend the 1602 case and perf'd top option for sure. A beefier transformer than the Spruce Canyon offering is nice if you intend on trying power hungry tubes. If you start rolling expensive tubes, the sky$ the limit. I've settled on a 6DJ8 Bugle Boy and a Siemens E88cc as my two "go to" tubes lately, which are currently about $20ish apiece. I like either of them better than spendy telefunkens, "PQ" 6922's and RCA variants. 

 It's a very nice amp project that ought to be more popular than it is. I probably have 500 listening hours on mine with 20 or 30 tube swaps and not a moments grief.


----------



## cfcubed

Quote:


  Originally Posted by *bada bing* /img/forum/go_quote.gif 
_ < snip > 
 It's a very nice amp project that ought to be more popular than it is. 
 I probably have 500 listening hours on mine with 20 or 30 tube swaps and not a moments grief._

 

Great to hear feedback like this.

  Quote:


  Originally Posted by *barleyguy* /img/forum/go_quote.gif 
_Isn't there a trade off on noise versus power with the output resistor? That's why I haven't wanted to go that direction.
 I'd hate to underpower the orthos in order to make the IEM's quiet.

 Would the C3H change help the noise without changing the power output?_

 

Going beyond the recommended 330uF for C3H did not yield improvement in my testing (330uf C3H equaled use of battery heater using my most sensitive cans - D2000s). Someone w/more sensitive phones could confirm my findings by moving to 470uf & above and seeing if it makes any difference. Note fitment would become tough.
 Most of the related posts are in the "A Very.." thread. 

 Yes, the ideal R18s are jumpers, but its a good place for resistance to cope w/higher gain tubes WRT volume pot range. R18s also mask any very low level hiss or hum that may be heard between tracks w/very sensitive earphones. I'm not sure every last minuscule trace of hum possibly heard between tracks using very sensitive cans can be eliminated. We do have A/C & other things in close proximity to input stages on the 3" x 5" PCB.


----------



## cfcubed

Just a heads-up that CTHs w/Amperex PQ 8416, Siemens "Chrome Plate" ECC82(12au7) & RCA clear-top were well received @ last weekend's last weekend's Fall NY meet (see mostly around pg 6 or so).

 Now we know CTHs don't need $30->$40 PQs & chrome plates to sound very good, any early 60's ones will do. OTOH we know the design is great @ extracting each tube's inherent characteristics so don't think the nuance such tubes have to offer is lost either. Same may go for coupling caps, resistors, etc as well.


----------



## TimJo

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Just a heads-up..._

 

Thanks for the link. I'm sure Erik will love his new amp, especially starting out with an 8416. 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Now we know CTHs don't need $30->$40 PQs & chrome plates to sound very good, any early 60's ones will do. OTOH we know the design is great @ extracting each tube's inherent characteristics so don't think the nuance such tubes have to offer is lost either._

 

I agree with this based on my own experiments. The circuit does seem to be pretty transparent with respect to the tube. It's just as fun trying out a $3 tube as it is a $25 tube. Whatever the tube is capable of doing, you'll hear it. I have a new batch of tubes coming, with some complete unknowns to me, so it will be interesting to see if there are any surprises to be had. This time I picked up some 7 and 8 volt tubes as well, just to see.


----------



## erikzen

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Thanks for the link. I'm sure Erik will love his new amp, especially starting out with an 8416. 
	

	
	
		
		

		
		
	


	




 I agree with this based on my own experiments. The circuit does seem to be pretty transparent with respect to the tube. It's just as fun trying out a $3 tube as it is a $25 tube. Whatever the tube is capable of doing, you'll hear it. I have a new batch of tubes coming, with some complete unknowns to me, so it will be interesting to see if there are any surprises to be had. This time I picked up some 7 and 8 volt tubes as well, just to see. 
	

	
	
		
		

		
		
	


	


_

 

I am greatly enjoying my new amp, indeed! The Amperex PQ tube sounds fantastic even with the Denons. I'm finding the bass isn't too much on all but the most low end heavy recordings. With classical, jazz and acoustic music everything sounds full and dynamic. Even though I'm sure the "cleartop" is no slouch, I'm not sure I'm going to be able to pull that Amperex out.

 Well, that's not really the case. I subscribed to this thread for more tube rolling ideas and I hope to be able to contribute to the community's experience with tubes for this amp.

 There is a small group of us in the New York area that wants to start having regular DIY mini-meets, primarily SiBurning. We had one meet in the spring with SiBurning, Kerry and one of SiBurnings friends from outside of Head-Fi. I have very little DIY experience myself but I'm trying to learn. I was thinking the CTH could be a good group project for us.


----------



## cfcubed

Quote:


  Originally Posted by *erikzen* /img/forum/go_quote.gif 
_I am greatly enjoying my new amp, indeed! The Amperex PQ tube sounds fantastic even with the Denons. <snip >
 I subscribed to this thread for more tube rolling ideas and I hope to be able to contribute to the community's experience with tubes for this amp._

 

Great to hear. There are a lot of 8416 fans in this thread. Even with its bass presence think it does very well w/the rest of the range too.
 Its been expressed that other Amperexs exhibit similar traits (e.g. 6922, their 6dj8 Bugle Boys).

 Think most around here have a Seimens around they like (bada bings post above). Seems my tube tastes run like keyid, adamus, timjo AFAIR.
  Quote:


  Originally Posted by *erikzen* /img/forum/go_quote.gif 
_There is a small group of us in the New York area that wants to start having regular DIY mini-meets, primarily SiBurning. We had one meet in the spring with SiBurning, Kerry and one of SiBurnings friends from outside of Head-Fi. I have very little DIY experience myself but I'm trying to learn. I was thinking the CTH could be a good group project for us._

 

I'm bringing this part over to the original CTH thread "A Very...".


----------



## erikzen

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Think most around here have a Seimens around they like_

 

I'd like to get my hands on one of those chrome plates you had at the meet. I found some Seimans at Tube Depot but the prices are ridiculous. 

https://www.tubeworld.com/index_high.htm


----------



## cfcubed

Got my New-Old-Stock (NOS) one for $35 or so shipped off the bay (like the NOS PQ 8416 you now have). There's one for $48 shipped... Its tests look good (we look for reasonably matched triodes, e.g. within 5%), but that's pricey. This thing is there too.
 I just set a search & waited. It took weeks to get those deals AFAIR.

 Again, don't really need PQs & chrome plates but those things do indicate the makers' premium tubes. If you can snag NOS for little more I would.

Some more reading for you


----------



## erikzen

Thanks Chris!


----------



## smeggy

It works very nicely with my Tung sol 6f8g tubes, my fave ever for the CTH.


----------



## dhw4488

Smeggy, does the CTH need any modification to use the 6f8g (if I am not mistaken its 6.3v) or could you just buy one of those adapters to 12au7 on ebay?


----------



## smeggy

mine was upgraded (*caugh) in various ways, but yes, the 6f8g works fine with an adapter from ebay


----------



## dhw4488

Sweet! Looks like there is another tube to get and try.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_mine was upgraded (*caugh) in various ways, but yes, the 6f8g works fine with an adapter from ebay 
	

	
	
		
		

		
		
	


	


_

 

ahem..i believe just one (*cough ) doesn't describe the upgrades fully


----------



## cfcubed

Yes, smeggy's build has been mucho modded (_some_ might say abused
	

	
	
		
		

		
			





 over time. I think the only thing not tossed in yet is the multi-heater V mod (offering more than 6.3v & 12.6v), and I'm not sure that's not in his build now.

 It's been said many times & many ways, unless some non-BoM changes are made, we recommend 600ma max heater draw. This covers the vast majority of tubes including (just) that huge, intimidating 6f8g
	

	
	
		
		

		
		
	


	




 Most spec sheets available from here.


----------



## smeggy




----------



## sachu

heh..i've got to try and resurrect this monster of Smeg's 

 Looks like Smeggy's power supply section on the board might be dead..only reading 7 volts on the input to the regulator..I am going to hate taking the PSU section apart.

 Heater supply section is a-OK..so am guessing either the BJT Q1P died, cause this was a very early build without the BC337 fix, or one or more of the diodes are gone. Caps look fine as there doesn't seem to be any crappy leakage.


----------



## smeggy

Personally I think it just died from it's own sheer awesomeness. It is simply moar awesome than it could take.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Personally I think it just died from it's own sheer awesomeness. It is simply moar awesome than it could take._

 

hehe..it is quite awesome indeed..surprised it hasn't burned your house down 
	

	
	
		
		

		
		
	


	




 naah am just kildding, I like the mods you have done..though it seems like there is some thready substance all over the amp..no clue what it is..looks like cotton or some such stuff...very fine.

 But never fear..we'll resurrect this guy..


----------



## sachu

yep..took more measurements..it is definitely the Q1P failure.
 Reading 35.xx volts on D1P and D3P.
 B+ voltages are spot on as well..
 So we'll see if this guy fires back to life after swapping those two transistors out.


----------



## smeggy

I think that fine fibrous threaddy stuff is cat fur where they like to sleep on everything


----------



## sachu

Yay!!..smegter..the monstrosity lives once again..listening to it right now..sweet indeed 
	

	
	
		
		

		
		
	


	




 Will pack it and send it out today.


----------



## smeggy

Ah, that is indeed sweet music to my ears. 
 Thanks sachu, you're a gentleman and a scholar







 was it just those two thingybobs?


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Ah, that is indeed sweet music to my ears. 
 Thanks sachu, you're a gentleman and a scholar







 was it just those two thingybobs?_

 

hahaha..thank you for the kind words Smeggy.goes double for you mind you 
	

	
	
		
		

		
		
	


	




.
 Yes it was just the two transistors..Alex put up a notice about the susceptibility of those transistors failing..swiitched them with higher power transistors..things should be better now.


----------



## Kabeer

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_naah am just kildding, I like the mods you have done..though it seems like there is some thready substance all over the amp..no clue what it is..looks like cotton or some such stuff...very fine._

 

He is called 'smeggy' for a reason


----------



## dpmiller

Stock Spruce Canyon kit build with 40's/early 50's RCA 6F8G; I like it. This amp is fun.


----------



## sachu

^^ very nice build..kudos! 
	

	
	
		
		

		
		
	


	




 Now i really want to try the 6F8G in this amp..


----------



## smeggy

is cool. I approve of this madness


----------



## cfcubed

Quote:


  Originally Posted by *dpmiller* /img/forum/go_quote.gif 
_Stock Spruce Canyon kit build with 40's/early 50's RCA 6F8G; I like it. This amp is fun._

 

You guys do have big ones. I particularly like the way the 9-pin mini is just tossed aside the amp in the pic
	

	
	
		
		

		
		
	


	




 I may have to try one of those monsters in my CTH someday.


----------



## Forte

Quote:


  Originally Posted by *dpmiller* /img/forum/go_quote.gif 
_Stock Spruce Canyon kit build with 40's/early 50's RCA 6F8G; I like it. This amp is fun._

 

That just looks insane, the tube looks as big as the amp!

 Does the adaptor fit the standard size tube hole in the top cover?


----------



## dpmiller

Octals are cool. Smeggy's my role model. 

 The bushing doesn't quite clear the ebay 6CG7-6F8G adapter so it rides a little high on the perf top.


----------



## erikzen

Quote:


  Originally Posted by *dpmiller* /img/forum/go_quote.gif 
_Stock Spruce Canyon kit build with 40's/early 50's RCA 6F8G; I like it. This amp is fun._

 

Looks very "mad scientist". Do I understand correctly that you need an adapter to run this tube? Like this:

one 6F8G 6C8G to 12AU7 12AX7 tubes adapter - eBay (item 260498927394 end time Nov-28-09 18:21:31 PST)

 And what's that wire that's coming off of both dpmiller's tube and the adapter on ebay? What do you do with that?


----------



## smeggy

The 6f8g has a top contact and the wire clips onto it. Odd shape, size and wiring are some of the reasons the 6sn7 took over. It is a little unwieldy.


----------



## stringgz301

CTH has been up and running two weeks now. Here are some tube impressions from a tube newbie. 

 CBS 7730: great for guitars, but vocals can be grainy. May have to go back and try this again later

 Amperex 6DJ8 Bugle Boy: fun! Good bass, nice soundstage, a touch of warmth. Listening to I Can See For Miles from The Who Sell Out the bass gives a strong sense of menace and the entire song sounds like it's on the edge of chaos

 Telefunken ECC82 Ribbed Plate (1963): splurged on a pair of these and they arrived yesterday. These are all about clarity and control. Crystal clear high end and tight bass. First tube that I tried that does piano well. Female vocals are very pleasant. Norah Jones Come Away With Me is getting rediscovered. Nickel Creek's first album sounds just like hearing them in concert.

 Still have to spend some time with Siemens RCA label 6922 GP. Just hard dragging myself away from the Bugle Boy and Tele. Would really like to try a 6CG7 Raytheon and a Tunsgram ECC82. Anyone want to start a tube loaner program?


----------



## cfcubed

Great to hear you are liking the amp. BTW,TimJo did a mini review of 7730, but his findings might be a bit different due to cans and/or his VitQ coupling caps (don't know what you've used).

 No surprise as reports on the more exotic/non-box caps often indicate they smooth things out a bit, tube feedback can vary based on that. But, as mentioned in these threads, it's probably not advisable to go cap rolling unless you are ready for the consequences and/or have another CTH to use during the surgery
	

	
	
		
		

		
			





 As you are seeing most can get the sound they want in this amp through tube rolling.


----------



## stringgz301

I went with the Sonicaps. Not sure what the burn in time is for them. To be honest, I listened to the 7730 when the amp was only 1-2 days old. I'll give them another try soon.


----------



## MrSlim

Quote:


  Originally Posted by *dpmiller* /img/forum/go_quote.gif 
_Stock Spruce Canyon kit build with 40's/early 50's RCA 6F8G; I like it. This amp is fun._

 

Man, you guys and your big tubes.. 

 Makes me wonder if there is some "compensating" going on..


----------



## Trapper32

Quote:


  Originally Posted by *MrSlim* /img/forum/go_quote.gif 
_Man, you guys and your big tubes.. 

 Makes me wonder if there is some "compensating" going on.. 
	

	
	
		
		

		
		
	


	


_

 

I WAS thinking of trying one of those "big" tubes


----------



## MrSlim

Quote:


  Originally Posted by *Trapper32* /img/forum/go_quote.gif 
_I WAS thinking of trying one of those "big" tubes 
	

	
	
		
		

		
		
	


	


_

 

An old Scottish saying: Its not the size of the weapon, its the fury of the attack..


----------



## Trapper32

Tried quite a number of different tubes but definitely prefer one head and shoulders over the rest ... 6gu7 Raytheon ...the Japanese version... The sound is detailed yet eurphoric, wide soundstage...very addictive. Prefer it to the second place RCA 6cg7 clear top


----------



## cfcubed

Quote:


  Originally Posted by *Trapper32* /img/forum/go_quote.gif 
_Tried quite a number of different tubes but definitely prefer one head and shoulders over the rest ... 6gu7 Raytheon ...the Japanese version.._

 

Are you saying you like that 6gu7 Raytheon over all the other tubes you've tried in CTH? 
 If so, have you tried the usual suspects around here as well (e.g. Siemens, Amperex)? 
 IIRC you did have quite a few tubes that work in CTH...

 I have quite a few myself now but have been hesitant to drop the $60 or so on the adapter & big tube bit.


----------



## Trapper32

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Are you saying you like that 6gu7 Raytheon over all the other tubes you've tried in CTH? 
 If so, have you tried the usual suspects around here as well (e.g. Siemens, Amperex)? 
 IIRC you did have quite a few tubes that work in CTH...

 I have quite a few myself now but have been hesitant to drop the $60 or so on the adapter & big tube bit._

 

Yes the 6gu7 Raytheon beats all the tubes i've tried so far...including the bugle boy 6dj8, tungsrams, siemens, ge 5 stars , and too many to remember tonite( i've been away from home for the past month and only took the 6gu7's and 6cg7's with me). 6dj8's 12bh7's 12au7's and most of the variants.. I haven't tried the 7730 or 7316's or the amperex 8416 tho.... Apparently the 6gu7 is just a 6cg7 with lower gain. They come up on eBay every few weeks and are usually 5 to 10 dollars a tube.

 This is thru a Valab dac and using the senn 580 listening to mostly modern blues with emphasis on guitar. The 2009 remastered Beatles tunes are simply stunning with this setup .


----------



## barleyguy

Quote:


  Originally Posted by *Trapper32* /img/forum/go_quote.gif 
_Yes the 6gu7 Raytheon beats all the tubes i've tried so far...including the bugle boy 6dj8, tungsrams, siemens, ge 5 stars , and too many to remember tonite( i've been away from home for the past month and only took the 6gu7's and 6cg7's with me). 6dj8's 12bh7's 12au7's and most of the variants.. I haven't tried the 7730 or 7316's or the amperex 8416 tho.... Apparently the 6gu7 is just a 6cg7 with lower gain. They come up on eBay every few weeks and are usually 5 to 10 dollars a tube.

 This is thru a Valab dac and using the senn 580 listening to mostly modern blues with emphasis on guitar. The 2009 remastered Beatles tunes are simply stunning with this setup ._

 

I'm also using a 6gu7 Raytheon as my default/favorite tube. Wiatrob had one in his CTH at RMAF as well. IMO, that tube has the right mix of high detail and excellent frequency balance.


----------



## regal

I see people using 6n6p's and 6h30's, these tubes require alot of plate to cathode current, I thought the CTH was only a 1 mA HV powersupply? I'm not talking heater current.


----------



## sachu

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_I see people using 6n6p's and 6h30's, these tubes require alot of plate to cathode current, I thought the CTH was only a 1 mA HV powersupply? I'm not talking heater current._

 

The plates are at 2mA at 80 volts.


----------



## regal

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_The plates are at 2mA at 80 volts._

 

Amazing that the 6n6p and 6h30 are even listenable at this current.


----------



## cfcubed

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Amazing that the 6n6p and 6h30 are even listenable at this current._

 

Guess it's just an amazing little amp
	

	
	
		
		

		
			





Think smeggy _might _have been 1st to use 6n6ps but others e.g.barleyguy and I have as well.

 Maybe tubes unexpected to sound well do so because of their light loading / high impedance typical of Alex's designs. And decent plate voltage.

 You have one of these around yet? 

 Funny story - During my 1st PCB build my bench must have been too messy because I had to take a few moments to find the partially populated PCB on my bench... I'd actually "lost" it due to its size


----------



## TimJo

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Amazing that the 6n6p and 6h30 are even listenable at this current._

 

 Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Guess it's just an amazing little amp
	

	
	
		
		

		
		
	


	




 Maybe tubes unexpected to sound well do so because of their light loading / high impedance typical of Alex's designs. And decent plate voltage.

 You have one of these around yet? _

 

Regal you should really build one of these if you haven't already.

 I haven't built that many amps being new to the DIY thing, but I can say this truly is an amazing amp. I haven't come across any amp that reveals a tube's characteristics as well as this one. This is a tube rollers dream come true.

 Thanks Alex.


----------



## wiatrob

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Regal you should really build one of these if you haven't already.

 I haven't built that many amps being new to the DIY thing, but I can say this truly is an amazing amp. I haven't come across any amp that reveals a tube's characteristics as well as this one. This is a tube rollers dream come true.

 Thanks Alex._

 

 Actually spent some time with RCA 6AU7 and 7AU7 Clear Tops last night 
	

	
	
		
		

		
		
	


	




 Listened to all my dynamic cans to see which were going on the block - the CTH has become my reference (er, would if I could stick to one tube, which would probably be the Raytheon 6GU7). Quite nice driving JH-13 pros, which is my new work rig.


 I agree it's an amazing amp, perhaps the hidden jewel amongst all of Alex (and Chris'!) MANY contributions to the DIY community.


----------



## Trapper32

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Actually spent some time with RCA 6AU7 and 7AU7 Clear Tops last night 
	

	
	
		
		

		
		
	


	




 Listened to all my dynamic cans to see which were going on the block - the CTH has become my reference (er, would if I could stick to one tube, which would probably be the Raytheon 6GU7). Quite nice driving JH-13 pros, which is my new work rig.


 I agree it's an amazing amp, perhaps the hidden jewel amongst all of Alex (and Chris'!) MANY contributions to the DIY community._

 

I have the same problem,,,so many tubes and really relatively inexpensive too. Latest is the Russian 6n23p which are really clear, solid state like, but i also keep coming back to the Raytheon 6gu7 which just seems to do everything right.


----------



## cfcubed

Quote:


  Originally Posted by *dpmiller* /img/forum/go_quote.gif 
_Stock Spruce Canyon kit build with 40's/early 50's RCA 6F8G; I like it. This amp is fun._

 

Couldn't resist trying this and ordered one of those $25 6F8G -> 12AU7/mini adapters off the bay. *They are no good for the CTH. Edit: dpmiller found the 6F8G to 6CG7 one is the one to get.* 

 CTH uses pins 4 & 5 for (serial) heater supply. Center-tap pin #9 is unused in CTH and it looks like that adapter relies on is use... Note circled mini heater pins 4 & 5 are shorted in this adapter:





 Just before powering up a CTH of mine using this adapter I thought "Hey, I better check this thing out w/an ohmmeter." Glad I did. CTH's heater circuit would not have been happy.
 So a bit of re-wiring of the adapter & she'll be good to go.


----------



## stringgz301

Has anyone tried using different power supplies with their CTH? I'm using the one from Spruce Canyon (24 VAC - .83amp) and was curious if anyone has found that the supply made any difference in performance.


----------



## cfcubed

Think it depends on your tube's (series) heater draw... Most target tubes draw up to 350ma or so & IIRC the full draw of the amp with that was about 550ma (?). So going > 750ma WW should not yield a benefit then (.833ma being fine in most cases - it's what I use).

 If using tubes w/heater draw > 500ma or so you could move to a 1A wallwart, but doubt you'd hear a difference. Wallwart would just run cooler. We like to have at least 25% headroom in transformer/wallwart capacity so that they don't get too hot/stressed.


----------



## dpmiller

cfcubed -
 I'm glad you checked.

 My adapter says 6CG7 - 6F8G; checking pins 4 and 5, and they are not shorted on this one.


----------



## cfcubed

Quote:


  Originally Posted by *dpmiller* /img/forum/go_quote.gif 
_My adapter says 6CG7 - 6F8G; checking pins 4 and 5, and they are not shorted on this one._

 

Ack! Yes I should have picked up that one
	

	
	
		
		

		
		
	


	




 Thanks for clearing this up.

 BTW, quick re-wire (split 4/5 pins & moved pin #9 wire to then empty pin #5) and its working but I'm getting some hum w/the 6F8Gs - do you?.
 ANY other tubes in this CTH have dead silent/black background. 
 This is a new, bigger, better CTH build of mine BTW (more room, all runs > 3in are shielded, etc.).


----------



## cfcubed

My latest CTH is also my quietest. Perhaps because of the space, shielded runs, 24V reg clearance - who knows but I'm happy.





 And no hum issues anymore w/RCA 6F8G. These must have helped: 1) let tube warm up a bit, 2) made cap/grid wire a shielded one (pin #5 of CTH's mini = ground) & 3) moving CTH around or off of Rotel CDP top.





 I've tried a few tubes w/my new HF-2s (8416, 6922 PQ, etc) but none really hit me like this RCA 6F8G... 

 Smeggy & dpmiller know what they are talking about, these 6F8Gs are something special. Thanks for bringing them up


----------



## keyid

might have to try a 6f8G with hf-2, do they mate well with your other phones? Im concerned about noise, the only tubes I have issue with hum are my 6dj8's though I may have three bad ones.


----------



## Forte

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_My latest CTH is also my quietest. Perhaps because of the space, shielded runs, 24V reg clearance - who knows but I'm happy._

 

Very nice looking build 
	

	
	
		
		

		
		
	


	




 What case have you used? Have been considering a HB-360 case from eBay that looks just like it but have not seen one used before.


----------



## cfcubed

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_might have to try a 6f8G with hf-2, do they mate well with your other phones?_

 

Not crazy about either of my 6f8Gs w/DT880s & haven't tried w/my D2000s (or HD650s on their way to me from FallenAngel). Liking the RCA in the pic better than Sylvania. Have a NOS RAYTHEON 6F8G VT-99 on the way & they are supposed to be nice.
 Stayed up way too late listening to the setup in the pic... 1st time I've done that w/HF-2s. But it's likely other tubes in my stable mate well w/HF-2s - just have to crawl through them.

  Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_Im concerned about noise, the only tubes I have issue with hum are my 6dj8's though I may have three bad ones._

 

You might. Or perhaps something in your build, but I know you know what you are doing
	

	
	
		
		

		
		
	


	



 I'm a big fan of shielded runs. With vol @ 3/4s I could hear the very faintest, hard-to-detect hum w/my most efficient cans between tracks on my other builds. But can't hear *any* hum or hiss on this one with any of the other tubes I've tried across all my cans.
 A very, very tiny bit of hum is detectable in right channel between tracks w/my 6F8Gs that goes away when I grasp the cap/grid lead. Didn't notice it at all after tube was warmed up 1/2hr or so & moved amp away from CDP. Perhaps the nature of having a long grid line to top of tube around. But tube's fun value far outweighs any of this for me.

  Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_Very nice looking build 
	

	
	
		
		

		
		
	


	



 What case have you used? Have been considering a HB-360 case from eBay that looks just like it but have not seen one used before._

 

Thanks... Found CTH shines it's very best w/spread out/conventional build like this one. Have a few amps under my belt now & have heard several others @ meets & still come back to CTH goodness
	

	
	
		
		

		
		
	


	




 Re: HB-360 - Yep, that's the one. Can't beat the price esp if you combine orders from that guy.


----------



## cfcubed

Forgot to mention, before running out & getting 6F8G to 6CG7 adapter + 6F8Gs note that I had to revert from incorrect/non-BoM coupling caps (Sonicap 1uf gen I w/0.22uf gen II bypass) to WIMAs for reliable CTH/e12 latch w/6F8Gs.

 I've noticed a relationship between "massiveness" of coupling caps and time-to-1st-latch and, possibly, latch sensitivity. All tubes I've tried other than 68FGs, *and there've been a lot*, were rock-solid & fine w/numerous coupling cap combos in CTHs using 8/2009+ BoM. Just a heads-up that one may need to reduce sensitivity of CTH's e12 to achieve reliable latch w/6F8G depending.

_Note to marketers of designs lacking muting delay + offset protection: Please do not use this & other CTH/e12 discussions as promotional material. IOW, think its unwise to assume your customers see delay + offset protection as a downside of a design. Hated to have to say this, but as crazy as it seems there have been a few thinly-veiled jabs @ designs w/delay + offset protection in these forums. Yes, offset protection can sometimes be a nuisance as it does its job of protecting your cans... Much like paying any insurance bill
	

	
	
		
		

		
			



_


----------



## rds

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_ but as crazy as it seems there have been a few thinly-veiled jabs @ designs w/delay + offset protection in these forums. Yes, offset protection can sometimes be a nuisance as it does its job of protecting your cans... Much like paying any insurance bill
	

	
	
		
		

		
		
	


	


_[/i]

 

That does sound pretty crazy. Not only is it illogical, but practically why would a 20 - 30 second turn on delay be a problem with tubes? Tubes need to heat up before they can perform properly. I would think that most audiophiles would want to wait a least a few minutes before they start playing music.

 ...and I have to say again: I love this amp! I end up selling off a lot of equipment just because it seems unreasonable to have so many amps/dacs/headphones but this one is a keeper.


----------



## cfcubed

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_That does sound pretty crazy. Not only is it illogical, but practically why would a 20 - 30 second turn on delay be a problem with tubes? Tubes need to heat up before they can perform properly. I would think that most audiophiles would want to wait a least a few minutes before they start playing music._

 

The jabs I was referring to, and could try to find if they've not been edited out, had more to do w/offset protection AFAIR (don't think muting delay advantages can be debated). They mostly occurred in the first few months of CTH release when we were having issues w/a few CTH build's e12s staying latched. Although some of this was due to issues in the builds themselves, we tweaked CTH-e12 implementation resistors to better guard against this.

 I felt it had to be said since those involved w/CTH development want to maintain full & clear disclosure but there are risks involved in doing so. IOW, if there was danger of a proper build of this design damaging connected sources or cans we'd likely not have released it. And if it had already gotten out, or the risks were implicit in the design, you'd see big, bold warnings noting the dangers & instructions for avoiding them. Often & everywhere.

 Enough said there I think, my hope/bet is the request has been digested
	

	
	
		
		

		
		
	


	



 Let's try not to come back to this. Too much CTH good stuff to discuss
	

	
	
		
		

		
		
	


	



  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_...and I have to say again: I love this amp! I end up selling off a lot of equipment just because it seems unreasonable to have so many amps/dacs/headphones but this one is a keeper._

 

Thanks again for expressing this. If people around here knew the many amps you've built & heard, they'd know the real weight your statement carries


----------



## Forte

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_So, after seeing a couple tubes were tried in CTH that had other than 6.3v & 12.6v heater and found to work & sound good, knew there was nothing keeping the design from *directly supporting more heater voltages*.

 Nothing but a few more resistors & a way to switch among them.

 Calculated (ideal) R3H values for various heater voltages:
*Votage / R3H (ideal)
 4.2v / 3.3k
 5.6v / 5.8k
 6.3v / 7.4k
 7v / 9.3k
 8.4v / 15.1k
 9.4v / 23.3k
 12.6v / <none>*_

 

Finally got around to fitting this mod and have run into a problem.

 After fitting the voltage switch checked to make sure the heater voltages were all what they should be and they are all low.
 4.2v / 2.98v 
 5.6v / 4.35v
 6.3v / 5v
 7v / 5.63
 8.4v / 7.01v
 9.4v / 8.12v
 12.6v / 11.38v
 So anything between 1.22v & 1.39v low.

 Have the two wires from the switch connected were R3H was and have jumpered H1 & H2 which seems to be the correct way to hook this up. All other voltage measurements are correct and it is working. I don't know what my heater voltages were before as I have never checked them so not sure if this is a new problem or if they have always been low. 

 I did also change L2H to a 1.1amp version and increased the size of C1/2H could these changes have anything do do with it?

 It looks like I need to raise the voltages by about 1.3v to bring them all up to the level they should be. Looking at the schematic changing R1H should do this, but how do I calculate the value required?


----------



## cfcubed

It is possible that the changes/upgrades affected the final heater voltage(s).
 I bet we can get them within a few %s of targets by a change in the "reference" resistor - R1H. 
 It was correct to jumper H1/H2 & have the rotary substitute R3H values (or easier jumper R3H & wire R3H rotary to H1/H2).

 I'm curious what load you are using. I'd try a tester 6.3v tube for all Vs <= 7v and a 12.6v tube for >7v settings. Need a realistic load to tune the values.

 Think it would be good to get your 12.6v setting fixed first and that _may_ bring the others in line. So with your "R3H switch" set to open/infinite resistance, we'll be adjusting R1H's value.

 The standard R1H = 9.31k, start by checking its value. Then raise its value, by adding <= 1k or so in series, until you attain 12.6v heater (+/- 0.1 or so) for the tube. Pwring up/down between trials & double-checking R1H for each. If/when that is set recheck the other voltage settings. 

 Let us know how it goes. BTW, AFAIR only wiatrob has done this mod.

_Edit: It's important to have some resistance for the R1H/R3H combo - not let both go open/infinite. That could make the switcher output its max based on input V._


----------



## cfcubed

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_It looks like I need to raise the voltages by about 1.3v to bring them all up to the level they should be. Looking at the schematic changing R1H should do this, but how do I calculate the value required?_

 

So while having my coffee this AM I ran National's SIMPLE tool for this... Asking for 12.6 + 1.3v to be generated, *it suggested 10.2k - looks like adding a 1k to your 9.3k R1H will do the trick.*
 Not important, but curious what your 1k R2H measures since if its off that could cause the unexpected values.


----------



## regal

Are you guys typically using R18 ?


----------



## cfcubed

I always use 56R -> 100R there. Found 100R is generally best all-around as it compensates better for higher-Mu tubes & normal sensitivity cans. 
 If using w/very low efficiency cans, e.g. orthos, might want < 56R or even short. Anyone using such phones could chime in.

 We are really just looking for the lowest R18s that make the amp nicely usable (e.g. decent vol pot range).


----------



## erikzen

Two JHS 12AU7 Sylvania Vacuum Tubes NOS Black Plates - eBay (item 320471678191 end time Jan-13-10 19:14:11 PST)

 I just picked up these two tubes on ebay. I just happened to be window shopping (or is that monitor shopping) on ebay for tubes and saw this auction about to end. The final bid was at $13.50 so I said what the heck I'll throw $15 bucks up there. Sure enough, I ended up winning.

 Since there are two tubes, if someone wants to trade send me a PM.


----------



## keyid

using 100ohms, tried a bunch from 0 - 150 and 100 seems to be a good balance. 

  Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Are you guys typically using R18 ?_


----------



## barleyguy

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_using 100ohms, tried a bunch from 0 - 150 and 100 seems to be a good balance._

 

Mine also appears to be 100 ohm, based on the color bands (Wiatrob built it). My most sensitive 'phones are custom Klipsch X10's, and the least sensitive are modded YH3 orthos. It seems to be a good value for that wide range of cans.

 Regarding the Raytheon 6GU7 that many of us are using: It's still one of my favorite tubes, but I've been having synergy issues with it because it seems to excite the high frequencies quite a bit. It makes my custom X10's too bright. And if I'm using an internal sound card as a source it is too bright on all headphones. (I only do that if I'm at work and the battery is dead on my MP3 player. Like today.)

 So, I've been using a Mullard 12AU7 a lot lately. It has perfect frequency balance and great detail, but doesn't excite the high frequencies. Which seems to be perfect for sources or phones that don't need any additional treble. (I think I called it "boring" in an earlier post. "Mellow" might have been a better word. Mellow does not always mean boring.)


----------



## erikzen

I just got a couple of (unmatched) Sylvania 12au7s. I'm trying to find out a bit more about them. They both have black plates and a square getter.

 The printing on the tubes are slightly different. One tube has green printing. It says "JHS 12AU7, Made in USA, Sylvania" across the front. Written vertically to the right are the numbers "409". 12AU7 is also printed in smaller numbers near the top on the back.

 The other tube also says "JHS 12AU7, Made in USA, Sylvania" but the printing appears to be white (it's more faded so it's hard to tell). It has 406 printed vertically and also at the top is 12AU7 with the additional code below it J3T.

 Does anyone have any idea what JHS, 409, 406 or J3T stands for?


----------



## barleyguy

Quote:


  Originally Posted by *erikzen* /img/forum/go_quote.gif 
_I just got a couple of (unmatched) Sylvania 12au7s. I'm trying to find out a bit more about them. They both have black plates and a square getter.

 The printing on the tubes are slightly different. One tube has green printing. It says "JHS 12AU7, Made in USA, Sylvania" across the front. Written vertically to the right are the numbers "409". 12AU7 is also printed in smaller numbers near the top on the back.

 The other tube also says "JHS 12AU7, Made in USA, Sylvania" but the printing appears to be white (it's more faded so it's hard to tell). It has 406 printed vertically and also at the top is 12AU7 with the additional code below it J3T.

 Does anyone have any idea what JHS, 409, 406 or J3T stands for?_

 

JHS is a government agency indicator. It means they were manufactured for use by the US government. And the black plates in Sylvania tubes indicate they are probably from the 1950's. I'm guessing based on the info at Joe's Tube Lore:

AudioAsylum.com -- Joe's Tube Lore

 How do they sound?


----------



## erikzen

Quote:


  Originally Posted by *barleyguy* /img/forum/go_quote.gif 
_How do they sound?_

 

I had them delivered to my office. Heading home now. I'll post impressions later.


----------



## erikzen

Popped one of the Sylvanias into the amp tonight. With the Denon MD5000 DEs, I wasn't thrilled. The highs seemed a bit too rolled off, midrange was flat, and although there was a lot of good, deep bass, it did not compare to the the Amperex 8416 PQ. If I want lots of bass the Amperex brings it but it still has some slam and punch.

 Switched to the Grado HF-1s and this is a much better match. It fills out the bottom end nicely, with some punch and the highs sound good, if a bit grainy. This tube is a much better match for Grados.

 Edit: After a couple of hours, the tube sounds a bit more open. Bass is a little tighter. Highs are a bit more extended and the soundstage is much more tube-like.


----------



## cfcubed

Quote:


  Originally Posted by *erikzen* /img/forum/go_quote.gif 
_Switched to the Grado HF-1s and this is a much better match. It fills out the bottom end nicely, with some punch and the highs sound good, if a bit grainy. This tube is a much better match for Grados.
 Edit: After a couple of hours, the tube sounds a bit more open. Bass is a little tighter. Highs are a bit more extended and the soundstage is much more tube-like._

 

Yep, IMO need to give tubes 1/2 hr at least to come into their own... E.g. I don't make judgments about them in their 1st 1/2hr.

 Just a heads-up - really liking a pretty cheap miniwatt 7v tube @ 6.3v w/HF-2s. Very good match-up for me. 

_Note though that just got 2 of those 7dj8s yesterday & 1 has a bad right channel... Will be seeing about a replacement for it. 
 Update: Seller said he'd send a replacement right out to me free & to toss the bad one, looks good._


----------



## erikzen

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Yep, IMO need to give tubes 1/2 hr at least to come into their own... E.g. I don't make judgments about them in their 1st 1/2hr._

 

Seemed like it took more like 2 hours for the tube to "settle in". If this tube is really NOS it may need a few more hours to come into its own. I am assuming there must be at least a few hours of 'break in" time for a new tube.

 I still think the Amperex 8416 PQ is a superior tube with a similar sound but for $10 I think this tube is a good deal.


----------



## Ynis Avalach

Did anyone who's using a 6H30P replaced more than just L1H, L2H and the trafo, maybe heatsinking ICP and ICH? Is it necessary or advised to replace D1H-D4H, since they're 1A devices? C4 are higher voltage types already.
 Greetz and thanks for any help!


----------



## Forte

Quote:


  Originally Posted by *Ynis Avalach* /img/forum/go_quote.gif 
_Did anyone who's using a 6H30P replaced more than just L1H, L2H and the trafo, maybe heatsinking ICP and ICH? Is it necessary or advised to replace D1H-D4H, since they're 1A devices? C4 are higher voltage types already.
 Greetz and thanks for any help!_

 



 ICP is recommended to be heatsinked on all builds and ICH would probably benefit from a heatsink if changing L1H & L2H also, finding a heatsink that will fit the ICH may be difficult, there is not a lot of room back there.

 The only other changes I can remember were raising C3H to 470uf and C1H/C2H to 180/220uf but these were only if the changes to L1H/L2H introduced any noise into the amp, otherwise not needed, also hard to find parts in these ratings that will fit.


----------



## Ynis Avalach

Yeah I'll see how bigger tubes will handle. For now I exchanged L1H, L2H and ICP is heatsinked. C3H is 330µ for me atm, I'll see what happens when the 6H30 arrives.
 Thank you!


----------



## cfcubed

Quote:


  Originally Posted by *Trapper32* /img/forum/go_quote.gif 
_Tried quite a number of different tubes but definitely prefer one head and shoulders over the rest ... 6gu7 Raytheon ...the Japanese version... The sound is detailed yet eurphoric, wide soundstage...very addictive. Prefer it to the second place RCA 6cg7 clear top_

 

As a couple here have lauded Raytheon 6GU7s, little heads-up on a NOS one < $10 shipped. 
 I really need to stop buying tubes, right after buying that one


----------



## Ynis Avalach

Now that's the sound I was searching!
	

	
	
		
		

		
		
	


	



 Really nice tube, probably the best I bought so far, will have to listen more though. Even nicer and much more power over my HD595s. Really gets them jumpin'.
 Greetz Ava
 puuuh, but I just meassured, both ICH and the tube get up to almost 70°C, with an ambient of around 23°C. So I have to get a heatsink for ICH, quick.


----------



## Ynis Avalach

mmm...still rising, now at 78°C for the tube and 73°C for ICH, to what temperatures are you're 6H30 rising? Smeggy?


----------



## erikzen

Thanks to Chris I picked up a Siemens "chrome plate" ECC 82. I can see why people like this tube. It has a nice high end extension but it's very smooth. It also has a very wide soundstage.

 Any way to tell the date on these things?

 Was curious because it says "Made in Germany". After WWII and before the fall of the Berlin Wall, were things made in "West Germany" just labeled "Germany"? I think West Germany was just a name we used here to distinguish between East and West Germany.


----------



## mugdecoffee

So snagged the Raytheon 6GU7 that was linked to above and have honestly not been too impressed. It's pretty laid back and seems not too lively. There doesn't seem to be much "air" in the upper registers though it does have a pretty decent soundstage. I find the bass especially lacking. Overall just flat and uninteresting. It's a NOS tube and its only been running for a few hours so I'll give it some more time.

 The 6N1P I've been using though sounds excellent with my HF2s. Though at first it seemed a little sluggish, I've either grown into it or its improved. The bass is fantastic: plenty of it and all around. It's more forward sounding than the 6GU7 and with not as good soundstage or instrument separation but everything sounds much more alive. Definitely a fun tube and perfect for lower volume listening with the solid bass. I've had these for a while but I remember them being only a couple dollars each.


----------



## Trapper32

Quote:


  Originally Posted by *mugdecoffee* /img/forum/go_quote.gif 
_So snagged the Raytheon 6GU7 that was linked to above and have honestly not been too impressed. It's pretty laid back and seems not too lively. There doesn't seem to be much "air" in the upper registers though it does have a pretty decent soundstage. I find the bass especially lacking. Overall just flat and uninteresting. It's a NOS tube and its only been running for a few hours so I'll give it some more time.

 The 6N1P I've been using though sounds excellent with my HF2s. Though at first it seemed a little sluggish, I've either grown into it or its improved. The bass is fantastic: plenty of it and all around. It's more forward sounding than the 6GU7 and with not as good soundstage or instrument separation but everything sounds much more alive. Definitely a fun tube and perfect for lower volume listening with the solid bass. I've had these for a while but I remember them being only a couple dollars each._

 

That pic on eBay isn't that great but it doesn't look like the tubes I was referring to. Was it made in Japan or US if you know....The plates on mine are only half the height of the tube and are made in Japan. I snagged a 7730 on eBay and while its a nice tube, i think the 6GU7 is better.


----------



## mugdecoffee

Quote:


  Originally Posted by *Trapper32* /img/forum/go_quote.gif 
_That pic on eBay isn't that great but it doesn't look like the tubes I was referring to. Was it made in Japan or US if you know....The plates on mine are only half the height of the tube and are made in Japan. I snagged a 7730 on eBay and while its a nice tube, i think the 6GU7 is better._

 

The ebay picture is a bit misleading. The one I have was also made in Japan and its plates are as you described. Perhaps they just aren't a good match with grados or it could be personal taste. I'll try the tube again in a few days and see if it grows on me.


----------



## stringgz301

Some earlier posts in this thread had positive reviews of the Tungsram ECC82. I just picked one up from Skylab and I've got to say it sounds spectacular with my 325is's. I'd been using a CBS 7730 which sounded very good, especially for guitars, but as I A/B'ed the CTH+7730 against the Audiotailor Jade I just got from Skylab (and will be reviewing separately), I felt the CTH just didn't have the firm bass and overall sense of controlled power I was hearing in the Jade. Enter the Tungsram. The expression "fist in a velvet glove" comes to mind. Very musical yet powerful at the same time, without any harshness. All the instruments are very well-defined and clearly positioned. Everything from The Mountaingoats to Kings of Leon is getting a re-listen and I keep finding myself with my eyes closed and a smile on my face. This is a keeper.


----------



## TimJo

I love reading how folks keep finding good matches between a particular tube and a particular model of headphone. That's one of the great features about rolling tubes on the CTH, in that with patience, you can find really good combination's which compliment the audio signature of a given set of headphones. Based on my experience, you can even find tubes well suited for particular styles of music as well, be it rock, acoustic, jazz, etc... This is certainly one of the funnest amps to play around with.


----------



## mugdecoffee

I've been meaning to build a balanced amp and have been thinking about adding a second CTH board to my current one to balance everything but this really ruins a lot of the CTH magic, being the small size, low cost, and ability to roll a single tube. Espsecially balanced volume controls seem pricey. Instead, would it be possible to duplicated the diamond buffers but make them inverting to form the negative outputs? This would avoid most of the downsides to a full balanced amp while still getting the balanced output. The buffers look simple enough to knock out on protoboard if the could be inverting.


----------



## cfcubed

Only a few hrs w/same Raytheon 6GU7 mugdecoffee talked about & have to say my impression of it is pretty close to his. 
 But it's all good because like TimJo et al relate, the fun w/this amp comes from experimenting & finding tubes to use in it that match your tastes. Though if tube cost is a concern one can review these threads & grab a couple that elicit common impressions.

 > buffers look simple enough to knock out on protoboard
 Did that on initial protos of CTH & yes it is. Think you only loose benefit of ground plane which, depending on build particulars, _may_ not be much... I'd just not jam things up against the regs.


----------



## erikzen

I went a little crazy in the past couple of weeks buying some tubes. I should be set for a while now.

 RFT ECC82
ECC82 12AU7 NOS RFT OLD TWIN TRIODE ELECTRON VALVE TUBE - eBay (item 260539803610 end time Feb-17-10 04:02:43 PST)

 Sylvania GB 5814A
SYLVANIA GOLD BRAND 5814 5814A 12AU7 NOS PRE AMP TUBE - eBay (item 200433645539 end time Feb-05-10 04:28:04 PST)

 Amperex "Bugle Boy" 6DJ8
http://cgi.ebay.com/ws/eBayISAPI.dll...view=all&tid=0

 Siemens "Chrome Plate" ECC82
http://cgi.ebay.com/ws/eBayISAPI.dll...view=all&tid=0

 Sylvania "Black Plate" JHS 12AU7
http://cgi.ebay.com/ws/eBayISAPI.dll...view=all&tid=0

 Tung Sol 12AU7 (plus mystery tube 
	

	
	
		
		

		
			





)
http://cgi.ebay.com/ws/eBayISAPI.dll...view=all&tid=0

 I'm looking forward to posting my impressions of these.


----------



## rds

I really like the 5814A. I have a GE one, but I imagine Sylvania brand would be very similar if not the same.


----------



## erikzen

This afternoon I was home working and just received the Amperex Bugle Boy 6DJ8 tube yesterday so I figured I give it a spin. When I turned on the amp I noticed the tube was glowing very brightly and thought it was kind of unusual.

 I let the tube warm up and waited for the indicator light to turn green. Naturally, when it did I put on my headphones and pressed play. Even in a few seconds I could tell I liked the sound, but it was a bit too loud. As I turned down the volume the light turned back to yellow and the music stopped. I thought that was really unusual but didn't really put 2 and 2 together. I left the amp alone again for another minute and the light turned green again. This time however, I was getting suspicious. 

 I turned the volume knob again and the light turned yellow. I figured there was something wrong and turned off the amp. I was about to start searching for possible issues when it hit me. This is a 6DJ8, it is a 6.3V tube! You idiot!!! I changed the heater switched and viola, the tube had a more normal glow and the amp didn't shut down when I changed the volume. Phew! Everything is fine. My only question is did I damage the tube by having the amp set on the higher voltage?

 Now that I've had a chance to listen to the tube I really like it so hopefully I didn't compromise its life. The bass is very deep and full, very similar to the Amperex 8416 I have. However, the highs seemed to be more extended while at the same time the mids were a bit recessed. It sounds like a "v shaped" equalizer setting.

 I find that at lower volumes this is an excellent tube. It has lots of bass and good detail retrieval. At lower volumes the lows and highs don't seem to be so overpowering and the mids can shine through a bit more.

 Nice tube!


----------



## cfcubed

> When I turned on the amp I noticed the tube was glowing very brightly and thought it was kind of unusual.
 > This is a 6DJ8, it is a 6.3V tube! You idiot!!!

 Been there, done that (a couple times). But caught it quick (a few secs). Can't say much about the life issue, perhaps others can, but it wouldn't stress me much. 
 BTW, the opposite case fooled me for a minute or so... Too little gain for 12.6 run @ 6.3, and sometimes trouble latching (going "green").

 So you learn pretty quick what the "right" tube glow looks like & to double-check that heater switch


----------



## mugdecoffee

I got a few 6N6P tubes since they were getting good reviews here. I only used one for a couple days but they seemed pretty similar to the 6N1P but with a little better soundstage and some more detail in the highs. Soon after I recieved a 6DJ8 Bugle Boy and it's quite a bit better than any of the other tubes I have. The soundstage and seperation are excellent, details are excellent, and the sound is very full and lively. Highly recommended. As fun as tube rolling is, I don't feel like switching this one out.


----------



## cfcubed

Quote:


  Originally Posted by *mugdecoffee* /img/forum/go_quote.gif 
_ Soon after I recieved a 6DJ8 Bugle Boy and it's quite a bit better than any of the other tubes I have. The soundstage and seperation are excellent, details are excellent, and the sound is very full and lively. Highly recommended. As fun as tube rolling is, I don't feel like switching this one out._

 

Yepper, I'm a 6922 PQ fan (sort of a pricier ver of that BB). I've several Amperexes from that era and most do seem to share similar traits - like 'em w/my HF2s as well. BTW, if anyone wants to sample that sound there's a seemingly good looking 12au7 deal ATM.


----------



## erikzen

Seems like a great deal, Chris (if the price holds up). I like my BB 6DJ8 pretty well also. It hasn't left the amp in a few days. Will the 12AU7 sound much different than the 6DJ8? Hard to pass up a good deal but I'd rather go for something that's going to sound a bit different from what I already have.


----------



## particleman14

when is next round of pcbs coming through??


----------



## cfcubed

erikzen - I'd not expect these BBs to sound much different. 
 As for something that does, besides that Siemens, if you want something a bit rolled off/warm maybe a Mullard variant? I just poke for others' impressions, e.g. Joes Tube Lore , etc.. E.g. having read about Tungsram E80CCs I'm kinda interested in hearing them.

 particleman14 - Think runeight still has some of the current ver 1.1 PCBs, not sure if/when a new rev is needed. Think we'd look to provide larger C4 holes & a bit more space for them, a bit more C3H room & more mounting hole clearance at least.


----------



## keyid

are the 6922 the versions tested for noise etc..? Im currently looking for a tube to mate with RS1 and so far 6n6p is a good match; tubes I like with HF2 finding are not well suited with RS1, so the search begins. Going to try out a 12BH7A Tung-Sol Black Plate and the
 ECC82 Tungsram Hungary.


----------



## barleyguy

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_erikzen - I'd not expect these BBs to sound much different. 
 As for something that does, besides that Siemens, if you want something a bit rolled off/warm maybe a Mullard variant? I just poke for others' impressions, e.g. Joes Tube Lore , etc.. E.g. having read about Tungsram E80CCs I'm kinda interested in hearing them.

 particleman14 - Think runeight still has some of the current ver 1.1 PCBs, not sure if/when a new rev is needed. Think we'd look to provide larger C4 holes & a bit more space for them, a bit more C3H room & more mounting hole clearance at least._

 

I have a Mullard 12AU7. Commented on it a few pages back. IMO, it has great frequency balance, good detail, and is an all around good tube. It doesn't hype either the highs or lows, so if you're looking for a hyped tube that's not it. But it's great with cans and sources that don't need any additional impact or sizzle.

 I also have a Tungsram ECC82. I haven't spent sufficient time with it to comment. I'll get back to you on that one.


----------



## erikzen

I finally got the RFT in the mail this week. It was shipped from Bulgaria so that's why it took a little while. I'm very impressed with this tube.

 I first thought I may have gotten a dud. When I first plugged it in it took a long time for the amp to latch and the tube gave off a little flare of light. It also burns a bit brighter than some of my other tubes. After a fairly long warm up time it finally latched, but I initially heard a lot of noise. However the noise was only audible with the music off and the volume all the way down. When I turned up the volume the noise seemed to go away. When I turned it back down it had dissipated but was still audible. Turning up the volume and back down a third time seemed to eliminate the noise completely. Either the tube needed a bit of warm up or there was some kind of static charge built up that I needed to get rid of.

 Upon listening I immediately noticed a very detailed sound. This may be the most detailed tube I have so far. The overall sound is neutral. Bass is not very impactful but it is articulate. The sound may be slightly tipped towards the treble but only slightly.

 From what I can find on the web I think this is a military spec tube as it has a small triangle on it, which I think is a military symbol. I also read that RFT was the E. German counterpart to Siemens and it does have a similar sound to my "chrome plate". It also has a "chrome" piece that the getter is mounted on. It looks pretty heavy duty. Here is the best photo I've found of it online:

RFT ECC82 / 12AU7

 Overall, I would say it has a pretty "solid state" kind of sound. Lots of detail and speed, fairly small soundstage, balanced sound throughout the frequency range. I paid $20 for the tube, shipped from Bulgaria. Recommended.


----------



## erikzen

Snow day today so working from home and listening some more. The more I hear the RFT the more I like it. I have found a few scattered impressions on Head-Fi of it and for the most part they are all positive. Many describe the tube as sounding "clinical". I would agree with that assesment but in a positive way. To me the sound is very detailed but still musical. Surprisingly, I prefer it with my Grado HF-1 as compared to my Denon MD5000DE, even though I would think the more analytical sound would be a boon to the Denons. However, with the Denons the sound is a bit recessed seemingly detracting from the overall clarity of the tube. The bass presentation with the Denon's is more impactful though.

 Unfortunately, the buzz I was hearing previously is definitely there. It seems like a ground hum. This surprises me since many of the impressions I've found of the tube state it is one of the quietest. Actually, this is the first time I've heard any type of hum from the CTH and it is almost non-existent with the Denons, but with the Grados it is noticeable although changes when I touch the amp or reposition it. I assume it is the tube that is causing this noise and is there anything I can do to prevent it?

 Honestly, I can't hear the hum with music playing so it's really kind of a non-issue, but knowing that it's there bothers me a bit.


----------



## Forte

Quote:


  Originally Posted by *erikzen* /img/forum/go_quote.gif 
_I finally got the RFT in the mail this week. 

 This may be the most detailed tube I have so far. The overall sound is neutral. Bass is not very impactful but it is articulate. The sound may be slightly tipped towards the treble but only slightly.

 and it does have a similar sound to my "chrome plate"._

 


 Thanks for these impressions. Have been trying to find a "Chrome Plate" since I built my CTH but have not yet found one in my price range. Will try for one of these instead.


----------



## regal

Quote:


  Originally Posted by *erikzen* /img/forum/go_quote.gif 
_Unfortunately, the buzz I was hearing previously is definitely there. It seems like a ground hum. This surprises me since many of the impressions I've found of the tube state it is one of the quietest. Actually, this is the first time I've heard any type of hum from the CTH and it is almost non-existent with the Denons, but with the Grados it is noticeable although changes when I touch the amp or reposition it. I assume it is the tube that is causing this noise and is there anything I can do to prevent it?

 ._

 


 Usually a hum that is affected by touching things in the amp is ground related. Make sure your inputs, output, and pot are isolated from the chassis. Also may want to look on AMB's site for a ground loop breaker schematic.


----------



## erikzen

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Usually a hum that is affected by touching things in the amp is ground related. Make sure your inputs, output, and pot are isolated from the chassis. Also may want to look on AMB's site for a ground loop breaker schematic._

 

A ground loop hum is what I would think it is too, but it does not happen with any other tube. Plus I am not a DIY guy. My amp was built by cfcubed so I am not going to touch the Master's work.

 I was just wondering if an otherwise good sounding tube coudl cause a ground loop and if so if there was anything that could be done to fix it, short of actually modifying the amp. It works perfectly with every other tube I've tried so if it ain't broke...

 I may just have a bum tube.


----------



## Forte

I can't see it being a Ground Loop since this amp runs of a Wallwart the amp is not connected to AC earth. 

 The fact that only one tube does this points to the tube being the culprit, I have a Russian 6h23n which does a similar thing. Put your hand anywhere near the amp and you get a faint hum, move your hand away and all is good.


----------



## barleyguy

Quote:


  Originally Posted by *Forte* /img/forum/go_quote.gif 
_I can't see it being a Ground Loop since this amp runs of a Wallwart the amp is not connected to AC earth. 

 The fact that only one tube does this points to the tube being the culprit, I have a Russian 6h23n which does a similar thing. Put your hand anywhere near the amp and you get a faint hum, move your hand away and all is good._

 

I have a 6n6p with the same symptoms. I think it's caused by one of the pins not making a good connection, either in the socket or at the base of the tube.


----------



## tacitapproval

If it is the socket making poor contact. You can tighten the contacts with needlenose pliers.


----------



## keyid

probably noisy/bad tube. Got a 12BH7A Tung-Sol Black Plates and ECC82 Tungsram Hungary. I like the 12bh7a (running it 6v is pretty and fuzzy though it doesnt get loud) more then 6n6p but found the tungsram too bright for rs1. After modding my dac abit (upgrade bypass caps, star ground, power supply) the amp responds very well.


----------



## erikzen

Listened to a couple of CDs this evening and the buzz seems to be gone. This is fast becoming my favorite tube.

 Now I'm listening to a Sylvania GB 5814A. What a difference! Very warm, with a large soundstage. Very tubey sounding.


----------



## stringgz301

I'ts been several months since I built my CTH from the Spruce Canyon kit. I went with the Sonicap Gen II cap upgrade for C4, and was very happy with the resulting sound. However, lately I've spent a lot of time A/B'ing the CTH against the Audiotailor Jade, and noticed that while I found the sound from the CTH more musical I also hear that the middle of the soundstage of the CTH was more congested. It seemed like instruments toward the center were a little mushed together as compared to the Jade, where every instrument and voice was distinct. I wondered if my choice of C4 was influencing this, hence the start of my cap upgrade search.

 The challenge, as anyone knows that has built a CTH in the BOM enclosure, is lack of space. The PCB is very dense and there is little room for high end caps. After a little measuring and reading a number of cap reviews I bought a pair of Relcap RT's (.22mF, 200V) from Michael Percy. When they arrived and I saw their size I gulped, but then took a deep breath and started the process of swapping them for the Sonicaps. As you can see from the attached picture they fit, but only barely. I had to cover the leads with shrinkwrap and slightly angle some of the other caps, but got the Relcaps installed and the CTH reassembled.

 After a night of burn-in with pink noise I'm very pleased to report that the soundstage congestion is gone and the sound coming from my CTH is very clear and musical. Overall, the reviews of the Relcaps vs. the Sonicap Gen II seem accurate: the Sonicaps have a slightly juicier midrange and the Relcaps are clearer and more neutral across the spectrum. The most pleasant surprise so far is that the high end, especially for female vocals, is a touch smoother.

 Overall, a successful experiment. I'll update my impressions after another week of burn-in.


----------



## keyid

I also tried various c4 caps and settled on Mundorf Supreme Silver/Oil, highly recommended. Im looking at the possibility on using jung or shunt regs for power for one or all 24v, 12.6 & 6.3v. I tube toroid with three secondaries can supply all the power and also replace the switching heater. Any thoughts?


----------



## stringgz301

What enclosure are you using?


----------



## keyid

not encased yet


----------



## cfcubed

@ stringgz301 - Good you were able to tweak CTH sound to you liking w/those Reliable Capacitors. IIRC, your feeling that std CTH sounded a bit congested in mids was expressed by a couple others. And I think they "solved" it in the same manner - upgrading C4 caps to something big (e.g. I think rds got happy w/auricaps).

 With compactness being an important goal in CTH design, fitting large C4s is a challenge. And a reason small Sonicap Gen IIs were a recommended upgrade, instead of something bigger like the Sonicap Gen I w/Gen II bypass I used in what ended up becoming erikzen's build.

 @keyid WRT PS replacements - My 1st thought is you'd not have a very Compact Tube Hybrid then
	

	
	
		
		

		
			





 But as I recall you were able to detect & appreciate subtleties in changes, so perhaps you would w/such PS upgrades. It is likely CTH's design potential, SQ wise, is held back a bit by its compactness goal. E.g. I did/do find improvement (quieter background) in my larger, more spread out builds (like erikzen's & "Fancy CTH" in sig). Guessing that using high-quality shielded cable everywhere & moving LV reg a bit away may have had something to do with it.


----------



## stringgz301

Thanks for the info Cfcubed.

 Question: if you were going to bypass the .22mF C4's what capacitance would you use?


----------



## cfcubed

> if you were going to bypass the .22mF C4's what capacitance would you use? 

 I _think_ convention is 1/10th or so of the cap you are bypassing, so like .02uF or there abouts. I'm not an authority on it though and, to my imperfect ears, not convinced of SQ gains. Did it in erikzen's build because I'd the space & thought I'd try it.


----------



## erikzen

Is there any technical reason (theoretically) why or why not the CTH amp would work well with the Tesla T1 from Beyerdynamic? I heard this headphone recently and liked it a lot. However, it's expensive and if I bought one it would preclude me from purchasing a new amp anytime in the near future. My first impression was that the bass was a little flabby, as compared to a more powerful amp. Maybe the choice of tube would be a factor here?


----------



## cfcubed

> Is there any technical reason (theoretically) why or why not the CTH amp would work well with the Tesla T1

 Not that I can see from its specs. AFAIR CTH has been used to good effect w/some of the most difficult to drive dynamic cans around. Yep, the T1 may be better w/different tubes - perhaps those w/"less" bass. And there are always can/amp synergies to consider.
 But if one is spending that much on cans they might be inclined to consider upper/high-end amps. Unless such amps have a way to "flavor" them (e.g. tube rolling) be sure you like what you hear before buying the combo.


----------



## erikzen

Yeah, are not that good for critical listening but they are good for getting a taste of things. I would tend to agree that the T1 deserves a pretty high end amp.

 I tried the T1 with a Woo Audio 5 and it sounded fantastic. I tried it with the WA6 and the results were not as impressive. The sound got a little sloppy in the bass. Then I tried it with the CTH and I basically got the same sound as out of the WA6. I would say the CTH may have sounded a bit better, although I'm prejudiced. Still, I don't think fooling around with tubes is going to give the CTH the sound of a WA5.


----------



## bada bing

There is a long thread over at "the other place" on the T1 being designed around a 120 ohm output impedance on the amp driving it. The idea was put forward that the T1 sound is less than optimum if the dampening factor is too high from amps with too low an output impedance. Sounds goofy to me but the idea had traction with people with more smartz than me, so who knows
	

	
	
		
		

		
			





. I don't have a T1 so the discussion was just a curiosity.

 I would guess the output impedance of the CTH is what, 1 or 2 ohms ?


----------



## Henmyr

Quote:


  Originally Posted by *bada bing* /img/forum/go_quote.gif 
_There is a long thread over at "the other place" on the T1 being designed around a 120 ohm output impedance on the amp driving it. The idea was put forward that the T1 sound is less than optimum if the dampening factor is too high from amps with too low an output impedance. Sounds goofy to me but the idea had traction with people with more smartz than me, so who knows
	

	
	
		
		

		
		
	


	




. I don't have a T1 so the discussion was just a curiosity.

 I would guess the output impedance of the CTH is what, 1 or 2 ohms ?_

 

I though the output impedance was dependant on R18 which is also used to adjust the gain, and can thus be rather high.

 Anyone know the correct answer to this?


----------



## runeight

Quote:


  Originally Posted by *Henmyr* /img/forum/go_quote.gif 
_I though the output impedance was dependant on R18 which is also used to adjust the gain, and can thus be rather high.

 Anyone know the correct answer to this?_

 

The raw Zo of the amp is about 4R. Any series resistance simply adds to this number. So R18 of 150R would make the Zo about 154R. Etc.

 Sorry for the delayed post.


----------



## devast

I got some Raytheon 6gu7s, and 6cg7s. Weird thing is, the 6gu7 is made in japan with grey plates, while the 6cg7 is made in usa with black plates.



 



 Also got some RCA cleartop 6cg7s. I can't really comment on their sound for now, since i don't have a good source here.


----------



## suicidal_orange

I'm still waiting on my 7824's but am looking into amps for some incoming AH-D5000's so 
  Quote:


  Originally Posted by *runelight* 
_The raw Zo of the amp is about 4R. Any series resistance simply adds to this number. So R18 of 150R would make the Zo about 154R. Etc._

 

seems very well timed. I read that Denon's like low output impedance, but I don't really know what would be defined as low? Or for that matter what value I got in the kit, though I guess the 150 default. Not with the amp atm... 

 My Grado's seem to have a problem (left side much quieter than right, but still measuring the right resistance and crackly at loud volume) so I'll probably only have the K340 and Denon's - any thoughts on what value R18's should be used for these cans?

 Glad to hear your CTH is up and running Devast, I'd have answered your question if I could. Those tube pics make me want to start rolling!


----------



## cfcubed

Quote:


  Originally Posted by *suicidal_orange* /img/forum/go_quote.gif 
_I'm still waiting on my 7824's but am looking into amps for some incoming AH-D5000's so 

 <snip> Or for that matter what value I got in the kit, though I guess the 150 default. Not with the amp atm... 

 <snip> so I'll probably only have the K340 and Denon's - any thoughts on what value R18's should be used for these cans?_

 

Default R18s = 100R & they were incorporated for reducing gain to give more useful range on volume control, not for the purpose of altering output impedance. It may be possible that the R18s could save your OB from errant Line-In/Line-out swaps as well (mines survived that a few times).

 @ work I use partial markl-modded D2000s w/Siemens tube & 100R R18s to good effect. Erikzen's CTH is set up similarly & he's used / enjoyed his modded D5000s w/this.


----------



## erikzen

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_@ work I use partial markl-modded D2000s w/Siemens tube & 100R R18s to good effect. Erikzen's CTH is set up similarly & he's used / enjoyed his modded D5000s w/this._

 


 I will vouch for that. The MD5000 DE is my main headphone and I have been using it almost exclusively with the CTH for the past 6 months with very few thoughts of upgrading.


----------



## suicidal_orange

Sounds promising, guess I don't need different resistors unless the K340's are too quiet 
	

	
	
		
		

		
		
	


	




 I now have the D5000's (which are sounding rather good out of the CKKIII, for now) and the 7824's, but still no joy with the CTH. I airwired pin 1 and 2 of the 7824 and measured the voltages, both pin 1 to SG and 3 to SG were 3.7V just like with the old one! Take it out and pin 1 returns to a healthy 37V. What am I missing


----------



## cfcubed

I forget the history of your build, so can just suggest:
 * dbl check orientation of 7824 against PCB silkscreen. Its 180 rotated from what one might expect (metal tab to inside).
 * w/7824 out check its output pin (#3) PCB location to ground (SG) resistance. I posted mine once, don't recall but it should more than a few ohms IIRC.
 * if those are OK, then I'd think something upstream is toast (e.g. Q1P, Q2P) & thus unable to support the load. You could pop new ones in and/or check current going to 7824 input pin (#1) under load & post what you find here.


----------



## suicidal_orange

Thanks cfcubed, the orientation is definitely correct and this was the second time powering it on with a new Q1P and Q2P (tried once with the old 7824). I hoped by not connecting pin 3 there would be no load, so it should have coped and read 24V indicating a problem further on (I don't really do electronics but this made sense in my mind 
	

	
	
		
		

		
		
	


	




) Am I right in thinking the 7824 must be fully attached to be under load to measure the current?

 I've just measured 515 (2000ohm scale) from pin 3 to SG, will look for your measurement tomorrow (or should that be later as it's midnight...) and see if that's healthy. At least it's not shorted but at least that would be something identifiable!


----------



## suicidal_orange

I've attached the 7824 to the pcb and it measures 368 at pin 1 (assumed to SG...) on the 2000uA scale, but searching this thread for current just yields lots of discussion on tubes and a bit about peaking at 34V unloaded, so a 50V cap being better.

 Can anyone confirm my reading is unhealthily low? This is with no tube in. If so any suggestions what could be wrong would be greatly appreciated


----------



## cfcubed

Tube in/out should not affect the LV circuit much if at all. 

 So think you replaced popped Q1P (& Q2P) & using new 7824 (after reversed C10P). Something caused your Q1P to blow & we are still unsure what.

 I was driving out finding out if A) 7824 is not getting the voltage/current it should be getting, or B) its load is over spec & its falling down trying to supply it.
 IOW clarifying if the problem is upstream of reg or downstream.
 7824's center pin goes to ground (SG).
 Can you tell me (again?) what the LV circuit is doing when everything is attached/soldered, e.g. input V (pin #1) & output V (pin #3) to SG?

 If bad, you could then measure 7824's current draw between pin #1 & its pad on PCB (by lifting it, measuring amp across) & let us know that (leaving center pin attached (SG) & pin #3 to load/PCB). 
 You could then re-attach pin #1, lift pin #3 & introduce an artificial load between it & ground/SG (e.g. 5W 100R -> 300R resistor, 24V lightbulb) and see if it can drive the load to 24V. 
 If your 7824 cannot drive something like a 220R resistor to 24V (getting it warm) then the problem is upstream/feeding or 7824 itself. 
 If it can drive such a load then your 24V supply is working (at least through to output of reg) & the problem is downstream in CTH.

 Please see if you can do all the measurements & tests above & post back results.


----------



## suicidal_orange

Thanks cfcubed, I'll try and answer most of these now. The only thing you got slightly wrong was the death of Q1P - it didn't pop, but burnt slowly over at least 20 seconds. Not sure if that makes any difference and it and Q2P have been replaced (twice) anyway.

 Without 7284
 Pin 1 to SG = 37V

 With 7824 fully attached
 Pin 1 to SG = 3.41V
 Pin 3 to SG = 0.1V

 Lift leg 1
 Pin 1 to leg 1 = 332uA

 Lift leg 3, reattach leg 1
 Pin 1 to SG = 3.71V
 Leg 3 to SG = 3.11V

 Even if I had an artificial 24V load to add I have a feeling it wouldn't do much on 3V! From reading above it's not getting enough current?


----------



## cfcubed

With 37VDC in & not getting 24VDC out, my guess would be (another?) bad 7824. Unusual, as I've had many (maybe close to a dozen) through my hands & never hit or had a bad one. 
 Assume you assured center pin is ground/SG & it sounds like the 7824 is only passing 3V of its incoming 37V. Which is bad.


----------



## aphexii

So I was going through the parts list and noticed a couple items were no longer in production and/or out of stock.

 If I list them here, would anyone be able to help me find suitable replacements? Still fairly new to DIY (this is my 3rd build), so I don't want to buy the wrong thing


----------



## cfcubed

> If I list them here, would anyone be able to help me find suitable replacements? 

 This thread was targeted towards tweaks to CTH, prospectively for SQ improvement, and tube rolling experiences. I think it best to bring _necessary_ parts substitution & debugging over to the "A Very..." thread. Unless its something in progress like s_o's debugging...

 WRT "simple" parts (resistors, caps) substitution, the builder could/should compare spec sheets of spec'd parts vs those they can source to ID a sub. Watching physical size limitation (esp. height limit on big caps like C10P) while reviewing pics of completed PCBs if they must go bigger. And sticking as close to spec'd value as possible & respecting ratings. After going through that process hopefully we'd be down to very few part subs needing assistance / review here.


----------



## suicidal_orange

> Assume you assured center pin is ground/SG

 eh... 
	

	
	
		
		

		
		
	


	




 I checked my legwork and ground wasn't connected. Sorted that, plugged it in and released smoke instantly from another Q1P. It was on for less than a second, so no damage elsewhere (hopefully)

 Having previously checked the caps and diodes where am I looking next? Disconnect pin 3 and see if I get 24V? I've only got one spare Q1P left so don't want to blow it up if it's inevitable...


----------



## Henmyr

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Default R18s = 100R & they were incorporated for reducing gain to give more useful range on volume control, not for the purpose of altering output impedance. It may be possible that the R18s could save your OB from errant Line-In/Line-out swaps as well (mines survived that a few times).

 @ work I use partial markl-modded D2000s w/Siemens tube & 100R R18s to good effect. Erikzen's CTH is set up similarly & he's used / enjoyed his modded D5000s w/this._

 

There's been a lot of talk about damping factor lately (A low output impedance from an amplifier seems to be desirable). Do a high R18 reduce the damping factor in a way that the sound would be better if one were to short the R18?

 I'm thinking about adding a switchable R18 of 0R and 100R, would that be a good idea or is there nothing to gain by this? The volume would have to be lowered from the source a bit instead.


----------



## cfcubed

Quote:


  Originally Posted by *suicidal_orange* /img/forum/go_quote.gif
_ I checked my legwork and ground wasn't connected. Sorted that, plugged it in and released smoke instantly from another Q1P.

 Having previously checked the caps and diodes where am I looking next? Disconnect pin 3 and see if I get 24V? I've only got one spare Q1P left so don't want to blow it up if it's inevitable..._

 

  > Disconnect pin 3 and see if I get 24V?

 Yes, after replacing the newly blown Q1P please only attach pins 1 & 2 of 7824 to PCB. Then measure V between it's 3rd pin (output) & gnd/SG. You should get 24VDC in this no-load test (just proving PS portion in attachment).
 If you do then I think you need to:
 1) find a way to simulate a decent load (between pin #3 & SG) to proof LV circuit through 7824,
 2) if you 7824 drives a decent load, then problem seems downstream of reg - something drawing way too much current.
 Sorry for the difficulties you are having.
   
  Note: if a big pic of some cable shows below its this forum software screwing up    *Because this post has NO attachments.*


----------



## suicidal_orange

I mess things up (if I'd done it right in the first place it would work) then be stupid (not checking my wiring) and you apologise, cfcubed? I know it's rude not to accept, but I can't. I'm just sorry for wasting your time and really greatful for the support 
	

	
	
		
		

		
		
	


	




 Anyway, in the absence of any false load I've just listened to a couple of minutes music through my Voyager amp being powered by the CTH, is that enough to call the 24V OK? I'd like to think so...


----------



## suicidal_orange

Can anyone help me with determining my current sucker? 

 I've nearly finished markl'ing my new cans and would like an alternat amp for them (much like the Grado's they've replaced the gain on the canamp is just too high!)


----------



## suicidal_orange

Final bump for assistance before I post a "FS/pay to fix" for this - I can't even find a full schematic of the amp to work out what's using this LV supply so no chance of fixing it


----------



## sachu

huh? schematics are up on the cavalliaudio website. See link in my signature.
   
  What exactly are you having problems with?


----------



## suicidal_orange

Thanks sachu, I've looked on the website and it has schematics for the four parts but not the whole thing showing how it fits together - unless I'm blind?  After all the stupidity I've displayed in this build it wouldn't surprise me, it's my third and final project (the second was also a failure - SMD isn't fun)
   
  I have 24v coming out of the 7824 powerful enough to run a portable amp at decent volume without clipping but if I connect it to the PCB Q1P burns, slowly.  Any idea what's sucking the 24v so hard that it dies?


----------



## sachu

you need check further up the chain. I would say replace all buffer and rail splitter transistors at one go and then try it out again


----------



## naamanf

Quote: 





suicidal_orange said:


> Thanks sachu, I've looked on the website and it has schematics for the four parts but not the whole thing showing how it fits together - unless I'm blind?  After all the stupidity I've displayed in this build it wouldn't surprise me, it's my third and final project (the second was also a failure - SMD isn't fun)
> 
> I have 24v coming out of the 7824 powerful enough to run a portable amp at decent volume without clipping but if I connect it to the PCB Q1P burns, slowly.  Any idea what's sucking the 24v so hard that it dies?


 
  Have you verified the value of R1P?


----------



## suicidal_orange

Quote: 





> I would say replace all buffer and rail splitter transistors at one go and then try it out again


 
  Damn.  No spare MPSA42's and not enough 337's, and farnell now have a £20 minimum order.  Has to be done though, when I get time.  Thanks for the help - you were banned first time round!
   
  Quote: 





> Have you verified the value of R1P?


 
  1003F, measures 100.2k on my multimeter - no quick fix for me


----------



## sachu

let me dig through my parts bin..i have some MPSA42s you can use..but the 337s..and 327s i will have to look.


----------



## mugdecoffee

Would it be possible to use a 6SN7 tube in this amp?  Besides the different pinout, the CTH could manage the heater requirements and all the 6SN7 specs look reasonably close to other working tubes.


----------



## sachu

Possible..just need to get a 6SN7 to 6CG7 adapter. or make one yourself.


----------



## mugdecoffee

Just replaced my Alps RK27 pot with a TKD 2CP-2508 and the improvement is astounding.  While it was expensive, I'd definitely recommend it for someone's upgraded the caps and has a nice tube in their build already.  The bass is much tighter and deeper though that might be because I went from a 50k to 100k pot and my DAC has a cap on its output.  The sound is also much smoother.  Whereas there used to some sounds that seemed too loud and harsh especially during female vocals, the TKD pot doesn't seem to bite on these frequencies like the Alps did.  Since the higher frequencies aren't as rough, I can make out a lot more detail.  One interesting effect is that the soundstage seems a little farther back which feels different especially with Grados.  And the knob turns so smoothly!
   
  While it wouldn't be the first thing I'd upgrade if I were to build a second CTH, I wouldn't be done upgrading without a better pot.


----------



## cfcubed

That's great to hear  I've been considering getting a couple of the RK40s that have been up on the bay lately @ $25 or so a pop + shipping.
  Even tho they are new old stock, perhaps quite old stock, they probably would still represent an improvement.


----------



## mugdecoffee

Is there a way to reduce the gain of this amp?  I'm already using a 100ohm output resistor and find myself using the bottom 15 degrees of my pot at most.  Even with a nice pot, the channel matching is poor at the very bottom end.  I'd also like to not use the output resistor since its probably not ideal with Grados.  Maybe some way to add some negative feedback?  I'm also using a  6JD8 tube.  Maybe there are nice tubes with significantly lower gain?
   
  EDIT This amp has way too much gain for every pair of headphones I've used with it, not just Grados.


----------



## sachu

As you note, the only way to reduce the gain on the CTH is by rolling the tubes.
   
  The gain of the amp is directly dependent on the tube you use.


----------



## stringgz301

This is one of the downsides of listening to Grado's: they are very easy to drive.  I'm in the same situation.
   
  Sticking to 12AU7 and variant tubes will give you lower gain.  You could also add a resistor (50-100K) on the left and right channel between the input jack and the volume pot to attenuate the input signal.  This will probably yield another 30 degrees of pot rotation.


----------



## rds

You could also put resistance in front of the pot.  In my opinion this is the best option, assuming you choose your pot and resistor values such that the input resistance is not too high.
  However, the output resistors have their own function which is to reduce "hiss" from the amp.


----------



## stringgz301

Quote: 





rds said:


> You could also put resistance in front of the pot.  In my opinion this is the best option, assuming you choose your pot and resistor values such that the input resistance is not too high.
> However, the output resistors have their own function which is to reduce "hiss" from the amp.


 

 Any rules of thumb for determining if input resistance is too high?


----------



## rds

Quote: 





stringgz301 said:


> Any rules of thumb for determining if input resistance is too high?


 

 Depending on who you ask 10k - 100k ohms is a good input input impedance.  So as an example you could put 10k resistors in front of a 10k pot for 20k input impedance, or 50k in front of a 50k pot for 100k input impedance.  I think either one would be perfectly fine.


----------



## cfcubed

(cross-link) There have been questions as of late, some of which in PMs, regarding tubes compatible w/CTH.
 The information seems scattered about this thread & the CTH "A Very Compact.." thread.  I tried to consolidate it here:

 : http://www.head-fi.org/forum/thread/398839/a-very-compact-hybrid-amp/2025#post_6785071


----------



## Br777

^thanks for that


----------



## mugdecoffee

So I'm determined to add some negative feedback to my CTH.  I just hate having to turn up the volume just to center the music and the idea of further attenuating the signal before amplifying it so much seems silly.  I spent forever working through the schematics with my very basic understanding of tubes and transistors and ended up deciding that the input stage is inverting which the output buffer is not.  And then a minute of google searching confirmed what took me what seemed like an hour:
  
  Quote: 





holland said:


> For CTH, gain is directly related to the tube. If I recall the circuit properly, and you bump the input resistor up to around 10K, you should be able to feed back the output to the input via a 100K resistor (or larger). The output from the tube should be inverting and the buffer is non-inverting.
> 
> Give it a try or yell at me for even broaching this.


 

 The problem is that the output is biased up 12V so there would need to be a cap in the feedback loop.  The cap would be pretty small though to as long as you don't add much feedback.  I'd like to add variable feedback a la the bijou.  Instead of this global feedback, local feedback just around the tube would be possible in basically the same way but this might present too large of a load to the tube.  At the same time, I feel like local feedback might be less influential on the overall sound signature than global feedback though I have no logic to back that up.
   
  Any suggestions?


----------



## cfcubed

If runeight does not see this & offer thoughts, maybe you could PM him referencing this thread/post.  Something like you describe could be beneficial to many CTH users.
   
  A less sophisticated way to go could be finding a low/lower-mu tube that you enjoy.  Or using something like a black beauty that works better across its range.  My next, and probably last, CTH will have one.  Think it'll be the 5th one for me & will be even fancier than my "fancy" one


----------



## runeight

I have been alerted!!
   
  It is very hard to add NFB to this amp or I probably would have done it in the original design. As mudgecoffee has pointed out the output is at 12VDC while the input is at ground. You will need a big capacitor in the feedback loop to get a good frequency response so I don't think this is practical.
   
  Also, because of the phase inversion the NFB can only go back into the grid of the input tube as the NFB in the Bijou. This technique has drawbacks and in particular it drops the Zi of the amp quite a bit.
   
  So, I don't think this is possible. If you want an amp that can still roll a lot of tubes and has the NFB to more or less equalize the gain among the tubes you might have to try the SOHA II.


----------



## cfcubed

Thanks runeight... Then I guess a low-mu tube / high-quality pot would help CTH's use w/more sensitive cans.
   
  OT - Famous last words, but after building out the 3 or 4 projects I've in progress, I _may_ be done for a good long while WRT amp & headphone combos (see sig).
  I did run across the first headphones that IMO did not pair well w/CTH - 600Ω DT880s.  They had something of a dark pale reminiscent of my "older" driver HD650s when used w/CTH, perhaps having to do with their excessively high impedance. 
  OTOH I'm finding the "new" driver HD600s to pair very, very well with my CTH.  All of this WRT my tastes & prefs of course.


----------



## cfcubed

Just an FYI / crosslink:  Voiced some more YMMV/IMO about CTH tubes, etc over there:
   
http://www.head-fi.org/forum/thread/500280/4-amp-showdown-hifiman-ef5-decware-zenhead-schiit-asgard-cavalli-cth/75#post_6795916
   
  That probably belonged here.


----------



## Duckman

Probably very old news now, but I tried my old T1 from my CTH and IMO the combination was not a good one.
  
  Quote: 





erikzen said:


> Is there any technical reason (theoretically) why or why not the CTH amp would work well with the Tesla T1 from Beyerdynamic? I heard this headphone recently and liked it a lot. However, it's expensive and if I bought one it would preclude me from purchasing a new amp anytime in the near future. My first impression was that the bass was a little flabby, as compared to a more powerful amp. Maybe the choice of tube would be a factor here?


----------



## mugdecoffee

Quote: 





duckman said:


> Probably very old news now, but I tried my old T1 from my CTH and IMO the combination was not a good one.


 

 What tube were you using?


----------



## cfcubed

Quote: 





> Originally Posted by *Duckman* /img/forum/go_quote.gif
> Probably very old news now, but I tried my old T1 from my CTH and IMO the combination was not a good one.


 
   
  Yes, far too little info to be useful...  E.g. what tube, what T1s, exactly what made the combo undesirable for you, etc.
   
  I've a lot of experience w/CTHs and w/most info/feedback posted here.  I'm only aware of 2 situations where current-BoM (e.g. those w/330uF C3H) CTHs _may_ be sub-optimal; 1) very efficient cans/IEMs where gain/hiss bits come up (& 150R R18s don't do the trick), and 2) _maybe_ very high-impedance cans like those 600R DT-880s I mention above.  And Beyer's new T1s also come in @ 600R.


----------



## Duckman

Sorry for the late reply. I just discovered the above questions.
   
  I was using the Ratheon 6GU7 at the time.
   
  To difficult to remember precisely what I did not like about the combination. It was probably congested and ill-defined. I only say this because I remember when I plugged in the SPL Auditor for the first time and it was night and day in relation to the separation of instruments and the clarity of the sound.
   
  Not necessarily recommending the Auditor either. It's obviously a good amp; but I've sold both T1 and Auditor since.


----------



## Br777

FYI - there's a good chance im selling my entire ortho rig including a CTH made by mrslim


----------



## MrSlim

Quote: 





br777 said:


> FYI - there's a good chance im selling my entire ortho rig including a CTH made by mrslim


 

 Aww, the Honeymoon is over already?


----------



## cfcubed

Going back a while for the quotes below, but whilst working toward trying to thin my heard of CTH tubes I gave the Russian 6N6P (aka "6H6N") another whirl:
   
http://lib.store.yahoo.net/lib/thetubestore/RU-6N6P.pdf
   
  and have to say its a sweet match for much of my music w/my "new" HD600s.  Had a bit too much bass slam w/my dampened D2000s.
  Wanted to give another belated thank-you to the guys suggesting it, like these two:
  Quote: 





smeggy said:


> Yeah, the Siemens E82CC I have is really nice but I wanted more slam and the feeling of raw power the 6n6p gives. I like the more aggressive presentation for my metal prefs


 
  Quote: 





adamus said:


> 6n6p is really nice.


----------



## aphexii

So out of all the tubes i have thus far, i keep ending up back on my RCA Cleartop 12AU7 w/ my ATH-ESW9's. The bass feels crisper with this one. 
   
  Tried out the following;
  GE 12BH7A
  Sylvania 12AU7A
  General Electric 5814-A (Five Star)
  RCA Cleartop 12AU7
   
  Been looking to find a cheap 6DJ8 on ebay but they are hard to come by, always get outbid 
	

	
	
		
		

		
		
	


	



   
  6N6P won't work on a CTH without some modification - correct?


----------



## sachu

should not be a problem so long as your power adapter is rated for atleast 1.4-1.6A
   
  6DJ8 sounds real nice in this amp and so does the 6CG7, 6GU7.


----------



## cfcubed

Quote: 





aphexii said:


> 6N6P won't work on a CTH without some modification - correct?


 
   
  Although you may need > 1 amp 24VAC adapter for 6N6P the real concern is the impact on your heater circuit parts for it 750ma+ draw.  That's just within default BoM L1H/L2H ratings & we'd like to see at around 20% headroom hence the recommended max 600ma heater draw.  Would also like to see some sort of heatsink on your ICH if using high-draw heater tubes.
  Our friend sachu seems to like to push any limits
	

	
	
		
		

		
		
	


	



   
  And its unnecessary to "stress" your little CTH, the large majority of tubes that work in it draw less than our rec max.  Some of my favs are Amperex 6922 PQ, Amperex 8416, Amperex/BB 6DJ8, Phillips JAN or Raytheon 5814, 12BH7A, Raytheon 6GU7, Siemens ECC82.


----------



## erikzen

Chris, sorry to threadjack but wanted to make sure you got my PM.  There is a meet in White Plains on Nov 20 if you can make it (or even if you can't make it, it will still go on).
   
  I've been using my Grados more with my CTH and have noticed some hum.  I can usually get it to go away if I move components around a little or move wires.  It seems the Grado cable picks up noise easier than other headphones.  Has anyone had similar experiences?  Any fixes?
   
  I also recently sold my Denons and am looking for another headphone.  How are the high impedence Beyerdynamic headphones with the CTH?  Good match?


----------



## cfcubed

Hi Erik,
  Sorry I didn't reply to your PM about the meet....  I wasn't sure I was going but you've given me one more reason to attend
	

	
	
		
		

		
		
	


	




   Please bring your gear & I'd like to see/hear what you are talking about w/your Grados - they are on the more sensitive side compared to other popular headphones.
  Haven't experienced the wire-arrangement-leads-to-hum bit, but I imagine keeping space between audio & A/C wires might help.
   
  I'll bring the "fancy" CTH from my sig & we'll see how that does in comparison w/your CTH.  If the fancy clears up your grado / hum issues we'll just trade 'em because my cans aren't so sensitive.
   
  RE: CTH w/600R Beyers - Mentioned elsewhere those were the first set of cans I did not like w/CTH.  Perhaps its best to stick w/cans < 400R ?


----------



## erikzen

Quote: 





cfcubed said:


> I'll bring the "fancy" CTH from my sig & we'll see how that does in comparison w/your CTH.  If the fancy clears up your grado / hum issues we'll just trade 'em because my cans aren't so sensitive.
> 
> RE: CTH w/600R Beyers - Mentioned elsewhere those were the first set of cans I did not like w/CTH.  Perhaps its best to stick w/cans < 400R ?


 


 You have 600 ohm Beyers in your sig with the CTH so I thought maybe it was a decent match after all, but maybe the "fancy" part is the kicker.  
	

	
	
		
		

		
		
	


	



   
  Looking forward to hearing the Fancy CTH.


----------



## sachu

I think its nearing that time where i need to build myself one of these fancy CTHs


----------



## cfcubed

Erik -  I guess I'll change my sig... Those Beyers work w/CTH & proper tube choice makes them sound OK, but I like my other combos better.  BTW, I bought my 600R DT880s when they made their splash here, and they are good cans, but I'm spending more time w/HD600s esp w/CTH.
   
  Sachu - a lot of work went into Erik's CTH & even more into my "fancy" one.  Think spreading things out & shielded cables help make things more quiet than a std build.
  BTW the pwr switch is a DPDT & breaks e12 relay pwr along w/24VAC in so there is no "click" @ pwr off.  Nice to hear the design @ its best but I really did it because of my closeness to the project.  
  Here's another shot:


----------



## Forte

Quote: 





cfcubed said:


> BTW the pwr switch is a DPDT & breaks e12 relay pwr along w/24VAC in so there is no "click" @ pwr off.


 

  
  Have you posted detail on how best to do this anywhere?
   
  And how do those Russian caps sound compared to the Sonicaps?


----------



## cfcubed

Re: relay interrupt:  IIRC, I just used a dremel w/small bit or X-acto knife & cut away one of the under side traces to the relay coil...  Probably the Q3E/D3E junction to coil negative trace.  Then used a 2-lead section pulled from an old floppy cable, one lead on the orphan relay solder joint, one lead to Q3E/D3E junction before the break.      Like using wire set pulls from old, thicker floppy cables for light loads (see LED feed in pic above).
   
  Re: caps - Wiatrob sent me those caps w/some CTH stuff I bought from him.  I like 'em & they are a good deal, but I can't say which is "better".  I think they soften the edge/treble a wee bit & that can be a good thing for the CTH.  But I really used them because I was out of Sonicaps, IOW not worth the trouble of swapping unless you want to play.
   
  Quote: 





forte said:


> Have you posted detail on how best to do this anywhere?
> 
> And how do those Russian caps sound compared to the Sonicaps?


----------



## erikzen

Quote: 





sachu said:


> I think its nearing that time where i need to build myself one of these fancy CTHs


 


 New variant: FCTH


----------



## royewest

I know this probably belongs on the for-sale forum, but it's been so long I thought I'd post here where folks might remember what this is (mod's willing) -- the Spruce Canyon web site is gone...
   
  I have a CTH kit from Spruce Canyon Labs I never built (got a new job just after it arrived and down the rabbit hole I went). Clearing up the office this afternoon I found it. Box has the 1.1 board, two tubes (Sovitek 6NP1 and RCA 12AU7A), the power supply, the replacement cap,black Hammond case (with tiny scratch on bottom), drilled perf and solid top with gaskets, knob, all the parts of course -- the works except for the custom front and back panels. The bag o' parts is unopened. Looking through old email I think this all came to something over $175.
   
  If folks are interested, send me a PM and I'll try to get back on line here by next weekend.
   
  Thanks,

 __Roy


----------



## cfcubed

Yeah, if you still have that kit you should list it in FS forum... Think someone would grab it up as sourcing CTH parts is a bit more difficult now & requires differing vendor shipments.
  
  Quote: 





royewest said:


> I know this probably belongs on the for-sale forum, <snip> I have a CTH kit from Spruce Canyon Labs I never built


----------



## arteom

I've been enjoying my CTH for some time now, ended up selling my x-can v8 after all and soon hopefully will start on a EHHA. But at the moment the cth is all I have. Just yesterday I received a pair of Audio Technica ATH-AD2000's, they sound great but with the CTH I get a very much audible hiss when the cans are plugged in, I get the hiss even with the volume all the way down, and it increases after about 1 o'clock on the pot. I don't turn the volume past 9 o'clock as it is plenty loud there. What can I do to make the CTH more suitable for these headphones? I have never taken the CTH past 1 o'clock, that was with my k501.


----------



## cfcubed

Try searching this thread & the "A Very..." thread for "hiss"...  Those AD2000's are pretty low impedance & high efficiency/sensitivity from what I can see:
http://www.audiocubes.com/product_info.php?products_id=1088
  Some amps, like the CK²III, can have their gain adjusted (e.g. like 4X instead of its default 9X).  The only way we can reduce the gain of the CTH is by choosing a lower-gain tube, so consider locating a lower-gain tube (I recently posted a supported tubes list).   Another option is to raise your R18s to 100R->150R.  And another is to sell/change-out the amp or the headphones
  Quote:  





> <snip>. Just yesterday I received a pair of Audio Technica ATH-AD2000's, they sound great but with the CTH I get a very much audible hiss when the cans are plugged in, I get the hiss even with the volume all the way down,  <snip>


----------



## arteom

*smacks self on head 
	

	
	
		
		

		
		
	


	



   
  I had tried a bunch of 6922 tubes, tried it on 12v setting for heater with a hytron 12AU7 and no hiss. Woohoo.


----------



## arteom

and the hiss is back again, hmm.


----------



## cfcubed

If it seems to come & go then maybe you are hearing _noise_ (e.g. due to a loose connection) not _hiss_ due to too high a gain.
   
  Quote:  





> and the hiss is back again, hmm.


----------



## erikzen

I have been hearing noise lately on my CTH.  I attribute it to switching to Grados for my listening.  With a Denon D5000 with Jenna Labs cable I heard no noise.  I've noticed that if the Grado cable comes too close to the power cord for the CTH PSU I get some ground hum.  This definitely comes and goes and is very dependent on component and wire proximity.


----------



## aphexii

oh HELL yea!
   
  Bugle Boy 6DJ8's that i won on eBay just arrived, absolutely fan-FREAKING-tastic pairing with my ESW9's


----------



## arteom

Yeah, I needed to switch out the ICH recently and maybe need to check the soldering on that. 
   
  Got a set of tubes myself just a few weeks back on ebay, got really lucky. Got one of each: Holland Amperex ecc88, Amperex PQ white label 7308 USA, Amperex PQ D Getter USA 6922, RCA West Germany 7308, and one mystery tube that perhaps outperforms all in resolution, though a little lacking in the bottom end. Have also a Siemens CCa I got a week before that. They really better the value of the CTH.


----------



## cfcubed

RE: ICH - Don't need to get into it, but ICH, even w/o any heatsink, should not fail if typical/recommended tubes are used & there is some ventilation holes in the case  (e.g. 12au7 series heater draw is about 300ma).  
  Nevertheless, because I'm a heatsink fan I usually fit a small one on ICH (e.g. even part of a small heatsink e.g. a "U" cut into an "L").  Do this also because I occasionally run tubes w/higher heater draw than recommended (600ma max series draw).
   
  RE: set of tubes -  That's one killer batch you mention there arteom.  IMO I hear a "house sound"  amongst Amperexes / BB 6DJ8s like those mentioned.  Glad you guys are enjoying this  I mentioned some of my favs w/my "new" HD600s here:
http://www.head-fi.org/forum/thread/417322/cavalli-compact-tube-hybrid-cth-tube-tweak-thread/540#post_7016862
  Quote: 





> Originally Posted by *arteom* /img/forum/go_quote.gif
> Yeah, I needed to switch out the ICH recently and maybe need to check the soldering on that.
> 
> Got a set of tubes myself just a few weeks back on ebay, got really lucky. Got one of each: Holland Amperex ecc88, Amperex PQ white label 7308 USA, Amperex PQ D Getter USA 6922, RCA West Germany 7308, and one mystery tube that perhaps outperforms all in resolution, though a little lacking in the bottom end. Have also a Siemens CCa I got a week before that. They really better the value of the CTH.


----------



## Mullet

I'm going to get this puppy going again because of the new CTH Rev A currently being built.
   
  Anyone in the past use either 12AY7 or 12AV7 tubes? They look like they're higher gain tubes of around 37-40 mu. The 4BQ7 tubes I'm currently using work fine and they have the same amount of gain. If no one has experience with them I might try and win a cheap one on the bay to give it a shot.
   
  Also, what about 5687 tubes? They seem to have the same amount of gain as a 12AU7; 20 mu, but have a higher running current of 450mA. This seems within spec.


----------



## cfcubed

Quote: 





mullet said:


> Anyone in the past use either 12AY7 or 12AV7 tubes? <snip<
> 
> Also, what about 5687 tubes? They seem to have the same amount of gain as a 12AU7; 20 mu, but have a higher running current of 450mA. This seems within spec.


 
  IIRC a higher-gain 12a?7 variant was tried here (12at7?) and it didn't work well.  If anything we are looking for gains equal to or lower than 6922 I think.  *Most of what we know about CTH tube compatibility is in my old tube compat post (now linked to in my sig). * There are usually hundreds of tubes on ebay from the known compat list.  There've been some others tried & work but IIRC they had higher-than-recommended heater draw.
   
  WRT 5687 you missed the most critical thing about 12au7/6922 compatibility, pin-out:
  12au7:http://www.scottbecker.net/tube/sheets/093/1/12AU7A.pdf
  5687:http://www.r-type.org/pdfs/5687.pdf


----------



## Forte

Both 12AT7 and 12AX7 were tried early on and neither could be made to work.  Have copied Alex's explanation below.
  I can vouch for the 6N1P and 12BH7A, both worth having(especially the 12BH7A).  6N23P-EV and 6N6P also work although IIRC the 6N6P is beyond what the Heater Supply was designed for and you need to change L1H & L2H to cope.  Heat sinking ICH was also recommended.
   
   
  Quote: 





runeight said:


> Quote:
> 
> 
> Originally Posted by *nux* /img/forum/go_quote.gif
> ...


----------



## Mullet

I was specifically asking about the 12AV7 & 12AY7, which are both in the 40 mu mid gain category. I realize that the other variants have too much gain. I suppose if they have the same pin outs they would be similar to using a 6922 or even 4BQ7/4BZ7. The other thing to keep in mind is having enough heater voltage I guess. Is 80v enough? I'm assuming that since no one has commented yet on these particular tubes then they probably don't work.


----------



## Mullet

I'm back. Searched the thread. I didn't find any info on whether 5670 or 2C51 works as a 6v drop in replacement. According to the tubes compatibility sheet that cfcubed posted, it appears that they are a possibility. The only caveat is that they haven't been tested. I just won an RCA 5670 for a buck, so I guess I'll be the first to find out and post my findings.


----------



## cfcubed

Quote: 





mullet said:


> I'm back. Searched the thread. I didn't find any info on whether 5670 or 2C51 works as a 6v drop in replacement. According to the tubes compatibility sheet that cfcubed posted, it appears that they are a possibility. The only caveat is that they haven't been tested. I just won an RCA 5670 for a buck, so I guess I'll be the first to find out and post my findings.


 
  If you look closely the 5670 row is white which means not evaluated.  Light green (hard to see diff w/white) means could possibly work but not tested.
  As said for 5687, most important thing to check is the pin-out & the 5670's incompatible w/CTH: http://www.sphere.bc.ca/test/tubes16/ge5670-2c51.pdf
  Would be careful straying from "core/main" CTH tube list, dark green rows or tubes reported to work.  It's conceivable that trying a sufficiently wrong tube could blow the unit.


----------



## Mullet

D'oh... looks like I'll be tossing this one back up on the bay or in the trash bin. Hate to do that to such a lovely tube. Guess I'll be sticking to the standard CTH tubes


----------



## civilmonkey

I seached this threat but it seems no one has posted about an English 1960's vintage 6DJ8 Brimar Tube.  I pickled up this tube on ebay for a reasonable price, and it's my current favorite.  My second favorite would be the Sylvania long grey plates I have.  I haven't heard Telefunken smooth plates or Bugle Boys.  The Brimar seems to do really nice with classical.


----------



## BK_856er

FYI the well-liked SoniCap GenII caps are no longer being produced.  The 200V version is out of stock from the manufacturer, but might be available elsewhere until inventory is depleted.  I got the somewhat larger 400V instead - looks like it will fit.  Several new versions will be released in the future according to Soniccraft.
   
  BK


----------



## Mullet

From what I've heard about Brimar their sound is similar to other British tube manufacturers in that the sound is very warm, rich, and tube-like. A friend of mine has the Brimar CV4003 running in an RSA Raptor. He loves the Brimar sound especially with female vocals. I reckon an American equivalent would be RCA. The black plate 5963 comes to mind. With my Senn HD650s I find it to be tad bit too meaty sounding. With my Beyer DT880s I find it just about right with rock and roll. I just picked up a used Mullard 12AU7 long plate on fleabay and while its a nice tube with the female vox, but it's no Siemens. More on that later. The Bugleboys are nice especially with the empahsized mids and decent highs. They have this punchyness to them. All Amperex do. 

I have both the tele smooth plates and ribbed plates and right now I'm favoring the ribbed plates. Perhaps, it's because I want clarity and detail over everything else. The smooth plates seem warmer but still have nice detail. The only Sylvania I've tried that I liked and stay with for a bit was the gold brand 5814A. 

 I'm going to have to with Siemens as my all around favorite brand for 12AU7/6DJ8 tubes. They are like the Mercedes Benz of tubes -- smooth, tight bass, well-defined, nice high end extension -- just really classy tubes. The thing about tubes is that one sounds awesome with one set of headphones and ok with another. I tend to go with 6v tubes for my AKGK701s because they have more gain than the 12AU7. I find the 6DJ8 tubes to be a bit too much with my Senns.


----------



## civilmonkey

Quote: 





mullet said:


> I'm going to have to with Siemens as my all around favorite brand for 12AU7/6DJ8 tubes. They are like the Mercedes Benz of tubes -- smooth, tight bass, well-defined, nice high end extension -- just really classy tubes. The thing about tubes is that one sounds awesome with one set of headphones and ok with another.


 


   
  Hi Mullet, All I know about the Siemens tube I have is that is says E82CC. It's made in Germany, has an 8 stamped into the bottom and you can make out D73 on the rear side of the tube. Do you happen to know what kind of Siemens it is?  I place it as a 3rd for my enjoyment, with the 6dj8 Brimar as 1, 12au7 RCA grey plates as 2 and this siemens 12au7 tube below as 3rd.  This is for my DT880's, so maybe the 6dj8 is a nice match for it.


----------



## Mullet

The E82CC the equivalent of a ECC802S, which is a premium grade version of the ECC82. It's considered a pretty rare tube. Yours looks to be the triple mica version, which is said to be better than the double mica version. It's said that yours has the best high end extension and clarity. If you're not into that tube then it's most likely the Siemens sound isn't for you. Perhaps, it's just not matching up with your particular set up and might be coming off as too lean. I would tend to think that Telefunken isn't going to work for you as well. Both German tube companies sound is described as lean and analytical in nature. I tend to like my Siemens better with my Senn HD650s above everything else ie AKG K701s and Beyer DT880 320ohms. These are the Siemens tubes I have and the order that I like them in... ECC82 chrome/silver plates, CCa, ECC802S, PCC88. If you don't want the tube I'll gladly take it off your hands.  
   
  Is your RCA the clear top version? I have the Conn branded clear top 12AU7 and love it. Reminds me a bit like the Siemens (detail), but with a tad bit mid warmth. I also have the RCA 6FQ7/6CG7 clear top and it's a peach as well. I'd recommend either/or and they are both on the less expensive end of things tube wise.


----------



## civilmonkey

Thanks for the detail Mullet.  I'm definitly not upto speed on which tubes are which, I basically read a bit, and if something seems like others have enjoyed it, look for a good deal on ebay.  The Siemens tude I have I paid 25 USD I think.  Let me listen to it a few more times before I give it up   Is there an online resource with details like you describe, or is it knowledge one collects over time reading various sources (would be my guess).
   
  Yes, the RCA Cleartop is a Conn branded 12AU7 (red text).  The RCA Long Grey Plates (I think!....) are Conn branded in green text, and those are my #2 fav for now.  The Cleartops and Grey Plate tubes are pretty similar for sure.
  Quote: 





			
				Mullet said:
			
		

> Is your RCA the clear top version? I have the Conn branded clear top 12AU7 and love it. Reminds me a bit like the Siemens (detail), but with a tad bit mid warmth. I also have the RCA 6FQ7/6CG7 clear top and it's a peach as well. I'd recommend either/or and they are both on the less expensive end of things tube wise.


----------



## cfcubed

Quote: 





civilmonkey said:


> Is there an online resource with details like you describe, or is it knowledge one collects over time reading various sources (would be my guess).


 
  I linked to a few in my "CTH tube info" link in my sig under "Lots of tube preference/synergy opinion here on head-fi and elsewhere like".
   
  My own likes run close to what I'm hearing here....  E.g. I prefer a bit warmer/bassy tube (like Amperex or rolled top-end ala Mullard) w/DT880/K701 and the Siemens ECC82 (or maybe clear-tops) w/my HD600s.


----------



## Mullet

From some reading around the internet I found some information that says that a 6BK7 tube can be used to replace a 6DJ8 tube. I checked out the spec sheet and it looks to have the same pin out. Anyone try one of these in the CTH? One particular post said that the 6BK7 falls somewhere in between the 6DJ8 and a 6BZ7, which both work on the CTH.
   
  With regards to the 12BH7s that I've been experimenting with lately... I bought an unknown 12BH7A, which was made in Great Britain. It appears to be a Brimar in its construction, but has some markings that indicate it's a Mullard. It has gold pins. It's seems nice and warm and laid back like your typical British tube. I also bought a Tung Sol 12BH7A with black oval plates and it's really nice. It has the same warmth as the British 12BH7A, but with more air and detail. I've heard great things with the RCA and Sylvania 12BH7As, but wanted to experience something different so I went with these two tubes. What are some experiences that you guys have had with regards to the 12BH7?
   
  Finally, I'm looking to maybe replace my C4 caps. I'm looking for a cap that might give a little more attack or a more precise feel to it. Like a tighter impact, but not too sharp. I originally had the Russian PIOs, but while installing them I broke 'em. So I went with the default Wima caps. They sound great, but I feel like they can be better. I've been hearing a lot about the Sonicap Gen IIs. Will these caps give me the sound I'm looking for?


----------



## schwallman

This past weekend I finally got ahold of a CTH. I love this thing. Im new to amps and tubes so I was curious about different branding of tubes. This amp came with a a few tubes but my favorite is the Siemens 6922 tube. The box is labeled Siemens RCA Label 6922. I want to pick up another one but the price range is strange to me. For $20-$200+. The writing on this tube differs from others branded as a siemens.
   
  Is there a real difference in a tube that is branded the same but different writing on the tubes? 
   
  ex:
http://thetubestore.com/siemense88cc.html
   
  and
   
http://tctubes.com/siemens-e88cc-6922-gold-pins.aspx
   
  and the one I have
   
http://www.audiogon.com/cgi-bin/cls.pl?accstube&1312480788
   
  all come up as a siemens but differ in price and look different.


----------



## cfcubed

Not getting into this much as there is a lot of info in this thread already, but there are so-called premium tubes that are sometimes tested to closer specs & sometimes have bling to distinguish them (e.g. gold pins, silver/chrome plates) & the command higher prices.  And there is sometimes a pedestrian version of the same tube that can sound "the same" but cost 1/3 or so the price.
   
  I've a couple links in my sig & again there is quite a bit of info in this thread.  Have fun & don't spend too much money.  A couple/few good tubes may be all you need (said the guy w/a dozen or more


----------



## schwallman

OK, I will check out your tube info from your sig. I think the collection of tubes that came with it have their positives and negatives but it was enough to get a feel for different brands. I really do like the warmth of the siemens 6922. I guess I can go up the ladder and see if there is any difference in cost/branding.
  
  Quote: 





cfcubed said:


> Not getting into this much as there is a lot of info in this thread already, but there are so-called premium tubes that are sometimes tested to closer specs & sometimes have bling to distinguish them (e.g. gold pins, silver/chrome plates) & the command higher prices.  And there is sometimes a pedestrian version of the same tube that can sound "the same" but cost 1/3 or so the price.
> 
> I've a couple links in my sig & again there is quite a bit of info in this thread.  Have fun & don't spend too much money.  A couple/few good tubes may be all you need (said the guy w/a dozen or more


----------



## Mullet

If you bide your time you can get some of the fantastic sought after tubes at around $40 tube. This means you *might* have to pick up two to four tubes to get in that ball park. Some of those 12AU7 type tubes are Siemens 5814A, CBS Hytron 5814A from the 50s, CBS or Raytheon 7730, Amperex 7316, Amperex 7318, Brimar 13D5, Telefunken ECC82 Smooth Plates, Siemens ECC82 Chrome Plates, Mullard ECC82 Long Plates from the 50s to 60s, Amperex ECC82 Bugle Boy, Telefunken ECC802S. There's also a whole list of 6DJ8 type tubes that I haven't listed. Two favorites are Telefunken E88CC and Siemens CCa (expect to pay about $70-$90 at a minimum for each). There are so many others that are great quality tubes that even cost way less. Read this whole thread for more info and favorites. I'm not going to lie... buying tubes is a serious addiction. I spent a little over $1k on tubes and now I've finally gotten myself to stop. I do have doubles and quads of a few of the super rare tubes though. So I'll never run out. The thing is... I've decided no matter what I'll never get rid of this amp -- I have one for home and one for work.


----------



## schwallman

mullet said:


> If you bide your time you can get some of the fantastic sought after tubes at around $40 tube. This means you *might* have to pick up two to four tubes to get in that ball park. Some of those 12AU7 type tubes are Siemens 5814A, CBS Hytron 5814A from the 50s, CBS or Raytheon 7730, Amperex 7316, Amperex 7318, Brimar 13D5, Telefunken ECC82 Smooth Plates, Siemens ECC82 Chrome Plates, Mullard ECC82 Long Plates from the 50s to 60s, Amperex ECC82 Bugle Boy, Telefunken ECC802S. There's also a whole list of 6DJ8 type tubes that I haven't listed. Two favorites are Telefunken E88CC and Siemens CCa (expect to pay about $70-$90 at a minimum for each). There are so many others that are great quality tubes that even cost way less. Read this whole thread for more info and favorites. I'm not going to lie... buying tubes is a serious addiction. I spent a little over $1k on tubes and now I've finally gotten myself to stop. I do have doubles and quads of a few of the super rare tubes though. So I'll never run out. The thing is... I've decided no matter what I'll never get rid of this amp -- I have one for home and one for work.



I can already tell this is going to get expensive. I already want another cth so I don't have to pack up shop to toto work with the one I have. I know I'm going to want the siemens you are selling but I will have to check with you at a later date on that.


----------



## Lil' Knight

Did anyone try the 6h30-DR with this amp? Does it run any hotter than other tubes? The 6h30-DR in my DAC run ridiculously hot and dissipate ton of heat.


----------



## cfcubed

If you search this thread for 6h30 you'll see experiences w/that tube.


----------



## Mullet

Quote: 





schwallman said:


> This past weekend I finally got ahold of a CTH. I love this thing. Im new to amps and tubes so I was curious about different branding of tubes. This amp came with a a few tubes but my favorite is the Siemens 6922 tube. The box is labeled Siemens RCA Label 6922. I want to pick up another one but the price range is strange to me. For $20-$200+. The writing on this tube differs from others branded as a siemens.
> 
> Is there a real difference in a tube that is branded the same but different writing on the tubes?
> 
> ...


 
   
  OK, so the deal is this... Back when these tubes were being manufactured tube manufacturers would sell their tubes to other manufacturers, which would in turn rebrand them e.g. Siemens would make a tube and Telefunken would print their name on them. Another example would be that Philips would make a tube and then RCA would re-brand the tube for sale in the USA. Thus, an E88CC tube in Holland would be labelled 6922 in the USA. All tube manufacturers did this. The different prices might reflect a used tube vs. NOS tube or a tube that had triodes that are matched vs. un-matched. Other factors are if the tube has a box, has good printing on the tube, or is from a specific year or time period.
  
   
       Quote:


schwallman said:


> I can already tell this is going to get expensive. I already want another cth so I don't have to pack up shop to toto work with the one I have. I know I'm going to want the siemens you are selling but I will have to check with you at a later date on that.


 
   
  Yeah I never thought I'd go on such a binge. Take this as a warning -- this amp might cause you to lose your crap! Just sold the Chrome Plates. But I might have a CBS 7730 that I'll be willing to let go. It's another really rare tube that was made by GE but branded as Raytheon or CBS. It's smooth and neutral like the Siemens, but has less impact or ummmph. The few tubes that I have to try are the CBS Hytron 5814A black plate from the mid 50s and the Amperex 7318, which is super rare.
  
  You could try the lesser expensive American variants first and then if they don't suit your needs try the European versions. One such tube that can be had for $10-$20 is the RCA 12AU7 clear top. Another is the Tung Sol 12AU7 black glass version. Also, people swear by the 12BH7(A) tube, which works just fine in the CTH. I have a Tung Sol 12BH7A and think it's quite swell.


----------



## schwallman

These came with the amp. I still go back to the siemens since dnb/dubstep sound nasty with it. Stringgz built this CTH awhile ago so I might look into the rev a if I could still get the board to build one. then I would have to worry about doing that whole learning how to build it thing.
   
  - a Tungsram ECC82 12v tube( Sounds pretty good but need more thump , to me it doesnt have it)
  - a Siemens 6922 6v tube labeled RCA Made in Germany (best so far)
  - a BugleBoy 6dj8 6v tube made in Holland ( second favorite)
  - a 7730 gold pin tube (probably CBS but not confirmed) - runs at 12v on the CTH
  - a 12au7 of unknown origin ( doesnt do it for me)
  - a 6h6n OTK - (This one runs hot as hell and I worry an take it out, it sounds ok.)
  Quote: 





mullet said:


> OK, so the deal is this... Back when these tubes were being manufactured tube manufacturers would sell their tubes to other manufacturers, which would in turn rebrand them e.g. Siemens would make a tube and Telefunken would print their name on them. Another example would be that Philips would make a tube and then RCA would re-brand the tube for sale in the USA. Thus, an E88CC tube in Holland would be labelled 6922 in the USA. All tube manufacturers did this. The different prices might reflect a used tube vs. NOS tube or a tube that had triodes that are matched vs. un-matched. Other factors are if the tube has a box, has good printing on the tube, or is from a specific year or time period.
> 
> 
> Quote:
> ...


----------



## Mullet

I'm a big fan of Amperex tubes. The 6DJ8 especially. It just has this really nice punchy 3 dimensional sound. I've heard that the Tungsgram 12au7 is good, but not great. Another really nice Siemens to look out for is the 5814A with triple mica. I have the Siemens ECC802S, which is the same thing, but with another label and the triodes are more tightly matched so there is less noise.
   
  You're not going to gain anything by going for a Rev A other than the option for two more heater voltages -- they are oddball voltages so the tube options are minimal and mediocre at best. The other improvements are larger area for the C4 caps, which makes it easier to fit in larger than BOM caps. I chose to go with Sonicap Gen 2s, which gives the amp a wider mid-range bloom. My other CTH has the Wima MKP4 series caps and I feel they have a snappier tighter feel to them. The rest of the changes are minor and don't effect sound quality at all.
   
  Unfortunately, there are no more boards left from the group buy I ran a few months back. The last I heard Runeight had no intentions on making another group buy possible. That could change in the future though. You never know.


----------



## schwallman

Ill have a look at the other tubes you mentioned. As for the boards, im always a day late and a dollar short. Ill keep an eye out in the FS forums for another CTH.
  
  Quote: 





mullet said:


> I'm a big fan of Amperex tubes. The 6DJ8 especially. It just has this really nice punchy 3 dimensional sound. I've heard that the Tungsgram 12au7 is good, but not great. Another really nice Siemens to look out for is the 5814A with triple mica. I have the Siemens ECC802S, which is the same thing, but with another label and the triodes are more tightly matched so there is less noise.
> 
> You're not going to gain anything by going for a Rev A other than the option for two more heater voltages -- they are oddball voltages so the tube options are minimal and mediocre at best. The other improvements are larger area for the C4 caps, which makes it easier to fit in larger than BOM caps. I chose to go with Sonicap Gen 2s, which gives the amp a wider mid-range bloom. My other CTH has the Wima MKP4 series caps and I feel they have a snappier tighter feel to them. The rest of the changes are minor and don't effect sound quality at all.
> 
> Unfortunately, there are no more boards left from the group buy I ran a few months back. The last I heard Runeight had no intentions on making another group buy possible. That could change in the future though. You never know.


----------



## Lil' Knight

Just picked up an RCA 6F8G for $10. Any idea on where to get the adapter? The only one I could find is on fleabay, for $65 shipped/pair


----------



## schwallman

I have a OTK 6h6n(6n6p) tube that came with my CTH. It runs extremelly hot. Should it?  None of the other tubes get that hot at all. This thing is almost untouchable after a few minutes.


----------



## cfcubed

Quote:  





> I have a OTK 6h6n(6n6p) tube that came with my CTH. It runs extremelly hot. Should it?  None of the other tubes get that hot at all. This thing is almost untouchable after a few minutes.


 
  Yes it should be hot as it's heater draws at least 750ma: http://www.tubes.ru/techinfo/HiFiAudio/6n6p.html 
  That's like 4X or 5X a 12au7's draw & much higher than the std CTH recommended max heater draw of 600ma.  IOW I'd not use it in a std CTH (e.g. one that wasn't made for high heater draws).
   
  Lil' Knight - IIRC I got a single adapter off ebay for $25 or so shipped... But I had to "fix" its heater mapping to the series one that CTH supports (only pins 4 & 5)  And I had varying success w/the couple 6F8Gs I used.


----------



## Mullet

Quote: 





schwallman said:


> I have a OTK 6h6n(6n6p) tube that came with my CTH. It runs extremelly hot. Should it?  None of the other tubes get that hot at all. This thing is almost untouchable after a few minutes.


 


  It's a 900mA heater so it's definitely going to run hot. Do you have the proper mods to be able to handle that kind of current? The amp is designed to take a maximum of 800mA heater current. I believe the parts L1H and L2H need to have higher values along with more amperage for the power supply to accommodate the 6N6P.


----------



## cfcubed

^^^^  And a heatsink on the LM2595   And good case ventilation.
   
  >   _The amp is designed to take a maximum of 800mA heater curren_t
   
  Nope. * Please see my post & the CTH site as we recommend a 600ma heater draw max for a std CTH....* Yes the parts are rated to at least 800ma but we'd like a little headroom esp. in the small boxes.  And a heatsink of some sort on LM2595 if running > 600ma.  
  This all said I've run the same 750ma draw tube talked about here for several hrs in a std CTH w/no problems.  I'd just not recommend it long-term on a CTH that's not had the mentioned high-current heater mods (unless you're a DIYer & can fix things if they break).


----------



## schwallman

Quote: 





mullet said:


> It's a 900mA heater so it's definitely going to run hot. Do you have the proper mods to be able to handle that kind of current? The amp is designed to take a maximum of 800mA heater current. I believe the parts L1H and L2H need to have higher values along with more amperage for the power supply to accommodate the 6N6P.


 


   


  Quote: 





cfcubed said:


> ^^^^  And a heatsink on the LM2595   And good case ventilation.


 


   I dont think the CTH has any current mods. It was built befoe the rev a I think. The fs post from the original seller didnt mention the tube. I think the guy I bought it from might have bought it. It was just in the box when I recieved it. I just figured it was ok to use.


----------



## DavidK35

Can anyone comment on the following re the 6CG7:
   
   
_"A 12AU7 is identical to a 6CG7 electrically and in the circuit it will function identically. However, there is a different heater pin out so if you are substituting, you need to make a change. In addition, the 6CG7 draws twice as much heater current so be sure that this will work in your circuit_"
   
  http://oldstockaudio.blogspot.com/2010/02/12au7-12bh7-6cg7-whats-best.html
   
  ps. so far I have found the 6211 (12AT7 type with the lowest mU of around 28) to be the best sounding, still experimenting.
   
  TIA.


----------



## Mullet

The 6CG7 works fine. I've used two in my CTHs -- the Mazda 6CG7, which is unique in that it comes in a short bottle instead of the typical long bottle and the RCA 6FQ7 cleartop, which is basically a 6CG7 without a shield. The RCA is pretty highly venerated among tube enthusiasts. The Mazda is fairly rare from what I understand.
   
  I haven't tried a 6211 yet, but have seen Amperex and Telefunken branded versions. I'm curious as to how good they are.


----------



## DavidK35

Thanks for the info Mullet.
  I'm doing a tube shoot out with this amp so the 6CG7 will be next on my list.
  The 6211 I am using is a RCA  black plate, triple mica.


----------



## Tribbs

Since there is another CTH PCB buy happening I thought I'd do a little tube recon.
   
  With anticipation I've gone ahead and ordered my first CTH tube: NOS RCA 5963 black plate (white lettering /1950's).
  According to one vendor, "audiophiles feel these outperform most of the other NOS 12AU7 tubes. Ranked on par with the European brands!"





   
  Was wondering if there is a consensus or a "top 5" list of favorite tubes for the CTH?
   
  There is at least one comment in this thread about using a low mu tube in the CTH to drive Grados.
  According to cfcubed post, that would limit tubes to the "low mu" 12BH7(A) types.
  If you plug Grados into your CTH I'd be especially interested in your favorite tube(s).
  Any low mu tube+Grado suggestions?


----------



## Mullet

That 5963 is a pretty good tube. It should be similar to a Brimar 13D5 or Mullard 12AU7. Warm and rich would be two adjectives that come to mind. 12BH7 definitely work fine with the CTH. I've a Tung Sol 12BH7 that at times does the trick for me. There are so many variants of the 12AU7 tube that work in this amp. Here is a pic that makes some general assertions with regard to tube rolling with the 12AU7 type tube... I have a ton of favorites in both 6DJ8 family and 12AU7 family along with 6CG7 and 12BH7 which are different tubes, but work just fine.


----------



## Tribbs

Thanks for that, Mullet.  My 5963 arrived today.  Now waiting for the PCB... 
	

	
	
		
		

		
		
	


	



   
  Whats the scoop on new "current production" Electro-Harmonix tubes?


----------



## cfcubed

I found the EHs to sound a bit accentuated in both the lows & highs...  Not my 1st choice in tubes but others might like it based on their prefs.
   
  Y'all know I'm updating the new Cables... forum IC PCB thread w/updates, the plan is for Mullet and/or myself to have working CTHs (based on the new BoM) today or tomorrow.
  Then we host the new XLS on CA's website, share the Mouser BoM & Digikey orders & I start the fun of getting payments & shipping.
   
*Edit: * Obvious but I'd caution our upcoming CTH builders against purchasing more than a couple (expensive?) tubes, e.g. one 12.6v-heated & one 6.3v-heated, until they've working CTHs.  And consider ordering a few extra of each the BC*s, for example, just in case. 
  Of the 100+(?) CTH PCBs/attempted builds we've had a few that builder's seem unable to have gotten working (bad/wrong part, faulty build, who knows?). 
  One (unnecessarily cautious?) thing I do is order extra & test/HFE all my BC*s, mostly to assure all work but also to weed out extreme outliers (rare but there's been a couple across my several builds).
  Note though the design absolutely does not require any transistor matching or elimination of outliers, it has adequate compensation for spec'd deviations of the devices.


----------



## tim_j_thomas

I posted this in the "the CTH (Compact Tube Hybrid) Rev A thread" but this looks to be a better place. . .
   
   I've got a CTH coming soon in the mail.  Scott (mullard) has send me a PM with some recommendations on tubes.  I'd appreciate any input others have as well.  I don't want to spend and arm and a leg (at least not at first) on tubes - need to sell my Meier Concerto first.
   
  So anything that can be had for $50 or less that works well with classical is much appreciated.
   
  Thanks,
   
  Tim


----------



## tim_j_thomas

So with my upcoming CTH, I have the following tubes coming as well:
   

 Sylvania 5963
 GE 12AU7A/ECC82
 Westinghouse Reliatron 4BG7A
 Siemens E88CC.
   
  Not sure of the age of these, but have been told the are good "starter" tubes.
   
  In addition I have an
   

 E88CC Tesla Gold Pin
 2AU7 vintage MULLARD tube labeled as Amperex-Long Grey Plates-"O"
   
  coming as well.  I don't know the ages of these either, but these should give me plenty of different tubes to listen to try out.
   
  If you've heard any of these, let me know.
   
  Edit: Corrected Sylvania 5763 -> 5963


----------



## Mullet

The Sylvania is a 5963 not 5763. It's a long life variant of the 12AU7. I found the tube to be warm and loose on the lower end. The GE 12AU7 is a nice all-arounder. It's not bad, but doesn't stand out as the best. The Mullard 12AU7 should be nice. Mullard is characterized as more warm and rich in its sound. The Siemens E88CC usually is described as open and detailed with a touch of warmth. I'd say the Tesla is somewhere in that realm as well being that it was modeled after the Siemens E88CC. I can attest to this. For the price these are a steal in comparison to what Siemens go for.


----------



## Pingfloid

Hi.
   
  I couln't find the LM2595 at Bang-Mohr in Bangkok (the Mecca-Market of Electronic Components) and I have finally ordered it from RS-Thailand, but they have to bring it from the UK and it’s taking ages 
	

	
	
		
		

		
		
	


	



   
  So I have decided to switch on the baby (without heater supply and tube) and take some measures.

 The main check-points look fine:
 - LED turns green
 - ICP Out = +24V
 - OG = 12V
 - OL/OR = +11.9V
 - TB = +118V.
 - I have connected a sound source to the input of C4, and the sound at the headphones output is OK. 
	

	
	
		
		

		
		
	


	



   
  The only thing that worries me is that *ICP gets very hot in just one minute* (very painful when touching it). _Is it normal?_ Could It be a side effect of running the circuit without the LM2595 and without tube? (higher voltage at ICP's input). I have mounted it with a double heat-sink.


----------



## cfcubed

Quote: 





pingfloid said:


> I couln't find the LM2595 at Bang-Mohr in Bangkok (the Mecca-Market of Electronic Components) and I have finally ordered it from RS-Thailand,
> 
> The only thing that worries me is that *ICP gets very hot in just one minute* (very painful when touching it). _Is it normal?_ Could It be a side effect of running the circuit without the LM2595 and without tube? (higher voltage at ICP's input). I have mounted it with a double heat-sink.


 
  WRT LM2595 -  Yep we've said that's one of the harder parts to source.  Note: although PCB wants "bent & staggered" leads I think an LM2595 w/straight leads can be made to fit.
   
  WRT 24V reg / ICP - That's the hottest part in a CTH.   I'd suggest getting finding the actual temp of its heatsink (e.g. cheap IR temp gun) & reporting it here.  A long while back I measured ICP heatsinks in a couple of my builds and IIRC single-heatsink ICP never exceeded about 70C & double-heatsinked about 60C.  These temps are OK for the devices, e.g. like to seem 'em < 80C, as long as there is good ventilation (e.g. perf top) so that temps do not build up nor affect nearby parts too greatly.
  BTW I've one of those $25(?) temp guns & its fun measuring temps around the house.  My dog's nose is 25C right now  The cheapos aren't super accurate but accurate enough these kinds of measurements.


----------



## dmcs414

Hello thread,
   
  I've been looking to expand my tube collection for use with my CTH and came across a tube that looked interesting but wasn't sure about it; a_ _*V**intage* RCA 6CG7 cleartop, for considerably less money than I'm seeing the newer ones go for.  Is there a huge difference between a vintage RCA 6CG7 and one of the newer versions from places like tubedepot which go for $50 a piece?  BTW, you can easily find the eBay listing I mentioned if you search for Vintage RCA 6CG7.  The auction ends in a few hours so I may just bite the bullet and buy the thing.
   
  On a side note, if anyone has any other tube recommendations they'd like to make that have particularly good synergy with TPs, I'd be grateful to hear them. Thx!


----------



## sachu

I'd say buy a RCA 6CG7 clear top from a reputable source like Upscale audio or tubedepot with matched triode sections and that has been tested for low noise and microphonics. I have seen a fair few 6CG7 clear tops with microphonics mainly and its rather frustrating.
   
  Since its a single tube, its worth spending the extra money.
   
  One other tube i really loved with the CTH and orthos including the TPs was the 6N6P. BUt the 6CG7 clear top was always my mainstay.


----------



## dmcs414

Quote: 





sachu said:


> I'd say buy a RCA 6CG7 clear top from a reputable source like Upscale audio or tubedepot with matched triode sections and that has been tested for low noise and microphonics. I have seen a fair few 6CG7 clear tops with microphonics mainly and its rather frustrating.
> 
> Since its a single tube, its worth spending the extra money.
> 
> One other tube i really loved with the CTH and orthos including the TPs was the 6N6P. BUt the 6CG7 clear top was always my mainstay.


 

 Thanks sachu.  I have a few 6N6Ps, older, Russian I believe.  They sound pretty nice to my ears and I plan to keep them.  Just trying to develop a wider selection.  Can you tell by the picture whether this one 6CG7 is legit or not?  It's eBay item # is [size=small]400268714739.[/size]


----------



## sachu

Yesh, its a legit tube alright. An older generation tube without the shield.


----------



## dmcs414

Quote: 





sachu said:


> Yesh, its a legit tube alright. An older generation tube without the shield.


 


  Sweet, I nabbed it.  Only 20 bucks too.  Thanks mate


----------



## dmcs414

Quote: 





dmcs414 said:


> Sweet, I nabbed it.  Only 20 bucks too.  Thanks mate


 

  
  Edit- Oops, this was meant to be an addition to my previous post, not a new post altogether.  My bad!  
   
  As long as we're on the topic of tube rolling and our beloved CTH, how many have you have done the necessary mods to allow the big fat tubes that I believe Smegs had rigged up in his CTH and is it worth the time/investment to use that tube or is there not much of a change between, say, the RCA 6CG7 we've been discussing?


----------



## sachu

Honestly guys, if you want a good mod for this amp, replace the LM7824 IC with a Belleson super regulator. (2A capable one). It should be a drop in replacement.


----------



## dmcs414

Quote: 





sachu said:


> Honestly guys, if you want a good mod for this amp, replace the LM7824 IC with a Belleson super regulator. (2A capable one). It should be a drop in replacement.


 


  I'll do some looking into that for sure. Thanks!  
   
  No thoughts on the mod I mentioned before that allows that bigger tube though?  I'm just basically curious as to what kind of difference it makes.


----------



## sachu

That was a 6f8g. He was using a national union tung sol round plate one. 

Youwill need a 6cg7 to 6f8g adapter that you can get from ebay.


----------



## dmcs414

Quote: 





sachu said:


> That was a 6f8g. He was using a national union tung sol round plate one.
> Youwill need a 6cg7 to 6f8g adapter that you can get from ebay.


 


  Thanks for all the help sachu, but what I'm asking is simpler than that.  Does it sound better, same, or worse in your opinion?  That is, of course assuming you've heard it with that mod and tube.  If not, don't sweat it.  I'm just trying to gauge the difference in sound were I to go that route.


----------



## Pingfloid

[size=medium]CTH down!




[/size]
   
  [size=medium]I have finally received the LM2595 and completed the assembly. It was working and all voltages correct.[/size]
   
  [size=medium]After a couple of minutes, the LED suddenly turned RED. I immediately verified the voltages and they were OK, but then R7S started smoking and the +24 and +12 voltages dropped to +20 and +9V approx. Heater and B+ were OK. Then I switched it off.[/size]
   
  [size=medium]Q3S and Q5S seem to be crossed. I am going to remove all the socketed IC’s and the 6 transistors from the Rail Splitter for verification. Then I will verify the +24V. If it’s ok, then I will replace the damaged parts from the rail splitter.[/size]
   
  [size=medium]I have combined the schematics into one A3 page to facilitate troubleshooting.[/size]
   
  [size=medium][size=small]http://dl.dropbox.com/u/46804116/CTHA%20Schematic.pdf[/size][/size]


----------



## Pingfloid

When removing IC1S, the output of the TLE2426 is +12V, so IC2S is still aive.
   
  When inserting IC1S, it's output is at +12V, and VG also +12V, but in one minute, R5S/R7S smoke and Q5S/Q3S burn. I am wondering where is the origin of this barbeque.


----------



## cfcubed

It can certainly be frustrating to try to uncover/correct build errors on this tiny PCB.  
  When I've tried I've done the "shot gun" approach, replacing many parts, but that's when I've known the cause of the smoke (e.g. a slip w/a test probe).
   
  I'm quite busy ATM & will try to look this over over the next several days, perhaps someone that knows better will chime in.


----------



## runeight

Remove one lead of R10E. Replace Q1S and Q2S. Replace Q3S, Q5S, R5S, R7S.
   
  Make sure that the Vg point is not actually grounded anywhere.
   
  Then try again. This may take a while.


----------



## Tribbs

Quote:


sachu said:


> Honestly guys, if you want a good mod for this amp, replace the LM7824 IC with a Belleson super regulator. (2A capable one). It should be a drop in replacement.


 

 I'm game, Sachu.  But I'm unfamiliar... Would someone be so kind as to provide the Belleson reg. part# or link, please? - TIA.


----------



## sachu

Quote: 





tribbs said:


> Quote:
> 
> I'm game, Sachu.  But I'm unfamiliar... Would someone be so kind as to provide the Belleson reg. part# or link, please? - TIA.


 
   
http://www.belleson.com/order.php
   
  Select High Current 2.0A.
   
  YOu want the SPJ78 in 24V configuration. 
   
  THis will be a far better thing to do than investing in a 6F8G or any exotic tube IMO.


----------



## Pingfloid

Quote:


runeight said:


> Remove one lead of R10E. Replace Q1S and Q2S. Replace Q3S, Q5S, R5S, R7S.
> 
> Make sure that the Vg point is not actually grounded anywhere.
> 
> Then try again. This may take a while.


 
   
  [size=medium]Thank you for your kind help.[/size]
   
  [size=medium]Yesterday I removed Q5S and Q3S (both were barbequed) and I measured the expected +12V at VG (without IC1 inserted). Nothing was heated up. R5S, R7S have survied, but I will repace them.[/size]
   
  [size=medium]But the measures are different for the R and L output buffers, so one of them must be wrong:[/size]
   

 [size=medium]L buffer: +24V at the base of Q8L, +23V at the base of Q9L, 22.3V at the base of Q4L-Q5L[/size]
 [size=medium]R buffer: 0V at the base of Q8R, +4.4V at the base of Q9R[size=small], 0V at the base of Q4L-Q5L[/size][/size]
   
  [size=medium]D2L, D2R, Q8L and Q8R are not damaged.[/size]
   
  [size=medium]- That was measured without IC1 inserted, and with the absence of Q3S, Q5S at the splitter. (I am afraid that they may be damaged again if I do not solve the problem at the buffers)[/size]
   
  [size=medium]It was too late at night for thinking clearly. I will continue this evening. [/size]
   
  [size=medium]Conclusion 1: I need glasses. This weekend I will go to the optician 
	

	
	
		
		

		
			



[/size]
  [size=medium]Conclusion 2: I miss my desoldering iron (the one with the pump attached into the head). Here in Thailand I can only find that sucker tube with a spring, and it is devastating for the small PCB of the CTH. Everytime that the spring is released, it spits mico-particles of soldering that are spread around the board. And it does not seem to work with double sided PCB's. I had to cut the transistor pins with cutting pliers (fortunately I let them very long) and then remove the pins one by one.[/size]
   
   
  [size=medium][/size]


----------



## Pingfloid

Update:  *Q4R* was completely shortcircuited between e-b-c in all directions (zero Ohms!) This is what made all voltages to drop at the Right Buffer.
   
  I am wondering what could cause Q4R to die like this. DC from B+ passing through C4R?
  Q5R, Q6R and Q7R seem to be OK. I have not removed them, but the diode-test readings are identical than at the Left Buffer.


----------



## cfcubed

WRT pulling parts:  I use the "solder blob" method -  Have PCB trace side up in your PCB vise w/pliers on the part to pull below (PCB overhanging bench, or at 90deg).  Make a wet ball of solder that covers the part's pins & pull.  Clean it up w/a solder sucker (clean out after every couple uses) then solder wick & 90%+ alcohol when all done w/the re-work.  The way you are doing it sounds more painful than it needs to be.


----------



## Tribbs

Quote: 





sachu said:


> http://www.belleson.com/order.php
> 
> Select High Current 2.0A.
> 
> ...


 
   
  Ouch - for nearly $70 shipped it should be very exotic indeed - 
	

	
	
		
		

		
		
	


	




 rich!


----------



## sachu

Well the other option is to build a Salas shunt regulator. But not a drop in replacement and the ampis no longer compact.


----------



## Mullet

@sachu So what is this tweak going to do for this amp? Less hum for 32ohm in ear phones?


----------



## Tribbs

What he said ^
   
  I noted the physical dimensions are 0.5" (12.7mm) Wide x 1.85" (38mm) Tall
   
  Is there enough headroom to fit it into the standard size Hammond case?
   
  Did you change any related capacitors?


----------



## runeight

Quote: 





pingfloid said:


> Update:  *Q4R* was completely shortcircuited between e-b-c in all directions (zero Ohms!) This is what made all voltages to drop at the Right Buffer.
> 
> I am wondering what could cause Q4R to die like this. DC from B+ passing through C4R?
> Q5R, Q6R and Q7R seem to be OK. I have not removed them, but the diode-test readings are identical than at the Left Buffer.


 

 Was Q4R the right transistor type?


----------



## BK_856er

Quote: 





tribbs said:


> What he said ^
> 
> I noted the physical dimensions are 0.5" (12.7mm) Wide x 1.85" (38mm) Tall
> 
> ...


 


 It's actually 1.25" (32mm) tall according to the pdf.  Looks like a potentially tricky installation with the Hammond case.
   
  ** edit: Using a toothpick into a vent hole I measure ~33mm between the top of the pcb and the top exterior of the Hammond case.  Subtract 1-2mm for lid thickness. **
   
  Has anyone tried one in a CTH yet?
   
  BK


----------



## Pingfloid

Quote: 





runeight said:


> Was Q4R the right transistor type?


 

  
  [size=10pt]Yes. But I am thinking of a possible cause of the meltdown: In order to test different caps, I have clips on C4L, C4R. I have been very careful to ensure that the leads have not touched each other while applying power, but when there is no tube inserted into the circuit, B+ remains around 50~58V for several minutes after power is switched off. Perhaps C4R was short-circuited when I put the CTH back into the drawer. The maximum collector-base voltage for the BC560 is 50V.[/size]
   
  [size=10pt]After replacing Q4R, the voltage below D2R still drops from +24V to 0V. There are no short-circuits; all the ohm/diode readings are almost identical in the main points at both L/R circuits; I have swapped D2L/D2R; but so far I have not been able to find other damaged component on the Right Channel Buffer. All that test are done without IC1 inserted into the circuit..[/size]
   
  [size=10pt]EDIT:[/size]
   
  [size=10pt]Runeight, you are my hero! The original Q4R was a 560, but I replaced it for a 550. I didn't noticed until I watched it with a big magnifying glass. The numbers are difficult to read and I still haven't gone to the optician... 
	

	
	
		
		

		
		
	


	


[/size]
   
  Now it's working!!!
   
  Thank You very much to all of you that have made this project possible.


----------



## runeight

pingfloid, does this mean that the amp is making music now?


----------



## Pingfloid

Quote: 





runeight said:


> pingfloid, does this mean that the amp is making music now?


 

 YEAH! Beautiful music in 3D 
	

	
	
		
		

		
		
	


	




  I have only played it for a little time, but as a first impression I have to say that I am surprised with the wide soundstage.
   
  Thank You very much for your kind assistance, and thanks to all the persons that have ben involved in the design and support of this great little amp.


----------



## runeight

Ah, good news then. Happy listening.


----------



## Pingfloid

This amp is literally *HOT*.
   

 Center of ICP: 83 degC
 Top of ICP heat-sink:  100 degC
 Most transistors: from 62 to 71 degC
   
  Even far away from ICP:

 Q1E, Q2E, Q3E: 71 degC
   
   
  One of the coolest part is the tube, with 63 degC.
   
  Measured with a Fluke 62 Mini IR Thermometer, after 40 minutes of work, in a air conditioned room at 24 degC. Hammond case with the cover removed.
  In my house, with the room above 30 degC, it is much hotter than that. I will measure it tonight.


----------



## cfcubed

You need not worry about components that are <= 75C.  Only your ICP reading is cause for concern. 
  BTW my bet is many CTH's ICPs are running up to 80C & have been doing so for years.
  Please let us know the input voltage to ICP (pins 1 & 2), perhaps your A/C adapter is supplying > 27 VAC under load.
  You can also search my posts about ICP's heatsinking, e.g. you don't want to snug it all the way down on the PCB.   You want ICP & its heatsink up off the PCB. 
  If you still have temp problems consider doubling up its heatsink, since its tab = ground you need not worry about its contact w/case or lid.


----------



## Pingfloid

Houston, I've listen to the radio on the CTH!
   
  I had the same problem with the 332C, and I reduced it with a gridstopper. The CTH already has a 300 Ohm R. Should I increase it to 1k?
   
  With the 332C there was radio with any position of the pot, but with the CTH there is no radio from 0% to 60% of the 50k pot.
   
  My other creatures, like the G3, XM6 or FF400 do not suffer from radio interferences.
   
   

  Note: the 6F8G grid cable increases the interference, but there is also interference with the 9 pin tubes.


----------



## Mullet

I would think it has to do with your power source. I've two CTHs and noticed a similar phenomenon when I'm using my work CTH and have the volume at 80 to 100%, which I would never do anyways. I swapped CTHs and noticed the same thing. When I took them home the interference went away. I work in a facility that has a rats nest of old video and audio cables all over the place and my nook is in the midst of all of it. In my situation I think the old cable is introducing RF interference. On the brighter side of things I'm currently ripping out all the old infrastructure and puttting in a brand new machine room with newer modern cable. It would be interesting to see if it goes away. In your case maybe a better power conditioner would solve the problem.


----------



## cfcubed

Very, very cool photo.  Man you are not wasting any time before going as far as you can with your CTH 
  I'd a 6F8G (forget brand) + adapter which I thought made my HD650s(?) sound their best w/CTH.   Looks nice & crazy too w/that giant tube + wire on top of the tiny CTH
  Traded 6F8G + adapter away because I still prefer HD600s & like "chrome" plate best w/them.
   
  Guess you drilled some holes in case, consider back & side ones as well + creative heatsinking when pushing the limits.
   
  BTW IIRC never had audible interference w/my CTHs, so can't help there.
  
  Quote: 





pingfloid said:


> Houston, I've listen to the radio on the CTH!
> <snip>
> Note: the 6F8G grid cable increases the interference, but there is also interference with the 9 pin tubes.


----------



## Pingfloid

That picture was purely accidental. I didn't notice that the exposure was on manual and I moved the camera before it was finished 
	

	
	
		
		

		
			




   
  The CTH do not receive interferences at my office, so it may come from a giant group of antennas that is about 500m from my apartment, and the absence of control over RFI regulations in Thailand.
   
  Like with the 332C, there are 2 simultaneous radio stations: one with news an other with music. And the intensity is higher at night.
   
  I have inserted ferrite beams in all the cables. Moving the supply cable makes no change, but moving the headphone or signal cable makes huge differences. Rising both the headphones and signal cables makes the sound from the radio louder than the music.
   
  I have already tried different signal cables and sources.


----------



## Pingfloid

Beside the Radio Interference at the CTH, the 6F8G cap cable creates a lot of microphony and some ground noise. Do you also have that problem?
  
 My adapter came with a very thin and quite flexible cable. Do you think that replacing this cable for a special one would reduce the microphony? I do not think that the microphony comes from the tube itself, because it only happens at the channel with the grid connection on the cap. Also, I have 3 different 6F8G's (1 Raytheon and 2 RCA) and they all show exactly the same result.
   
  The ground noise disappears when I touch the case. This is one disadvantage of using a wall transformer: there is no ground connection.
   
  It is a pity, because the 6F8G is the only tube that I have tried so far that gets closer to the warmth and fatigue-free of the Sense G3. Some of the other tubes that I’ve tried are 12AU7/6DJ8 Amperex BB, 12AU7 RCA, 12AU7 GE Long Plates, ECC88 Telefunken...  But I will keep on experimenting. I will also try rolling C4 cap. Otherwise the CTH will not be able to substitute the dead quiet and warmly sweetie Sense G3. (for my personal taste)


----------



## dmcs414

Could someone confirm for me real fast that these tubes would work OK in my CTH?  I searched for 5965 in the spreadsheet but didn't see it listed, and haven't done a lot of tube rolling so wanted to make sure before I pulled the trigger on them.  The eBay ad says the following.  Thanks in advance!!!
    *[size=small]Lot of 6 Assorted 5965/5965A/12AU7/ECC82 Vacuum Tubes Telefunken/Raytheon/GE"*[/size]   
 Telefunken 5965 (Made in Germany) Tubes w/grey ribbed plates (QTY 1)
* Raytheon 5965 Tube w/grey ribbed plates (QTY 1)[size=medium]
* Lewis& Kaufman 5965A Tube w/grey ribbed plates (QTY 1)[size=medium][/size]
* GE 5965 Tube w/grey ribbed plates (QTY 1)[size=medium][/size]
* GE 5965A(poor label)Tube w/grey ribbed plates and clear top (QTY 2)[/size]


----------



## Pingfloid

I think that the the 5965 is a 12AT7 type, with a mu factor of 60. We need the 12AU7 or 6DJ8 type, with a mu around 19~33
   
  Please, someone correct me if I am wrong.


----------



## cfcubed

PF - Are you saying you only get "ground noise" w/6F8G and it's grid wire? If so consider replacing that long cap wire with a shielded one, connecting the wire's shield to case/input ground (*which = tube pin #4*). IIRC this is exactly what I had to do to my 6F8G adapter - used a thin shielded cable for the grid/green/cap wire connecting the shield to (heater gnd) pin #4 internally in adapter case).

BTW never had ground noise that went away by touching the CTH or it's knob pot because I make sure both are connected to SG (which = IG).
Actually I feel the AC adapter supply is a unique advantage - keeps transformer far away from amp and reduces ground-loop problems.

And PF is correct about tube mu - AT is no good - again please see the CTH tube info link in my sig for CTH compatible tubes.


----------



## dmcs414

Thanks guys for the heads-up on those tubes



cfcubed said:


> PF - Are you saying you only get "ground noise" w/6F8G and it's grid wire? If so consider replacing that long cap wire with a shielded one, connecting the wire's shield to case/input ground (*which = tube pin #4*). IIRC this is exactly what I had to do to my 6F8G adapter - used a thin shielded cable for the grid/green/cap wire connecting the shield to (heater gnd) pin #4 internally in adapter case).
> BTW never had ground noise that went away by touching the CTH or it's knob pot because I make sure both are connected to SG (which = IG).
> Actually I feel the AC adapter supply is a unique advantage - keeps transformer far away from amp and reduces ground-loop problems.
> And PF is correct about tube mu - AT is no good - again please see the CTH tube info link in my sig for CTH compatible tubes.


----------



## Pingfloid

Quote: 





cfcubed said:


> PF - Are you saying you only get "ground noise" w/6F8G and it's grid wire? If so consider replacing that long cap wire with a shielded one, connecting the wire's shield to case/input ground (*which = tube pin #4*). IIRC this is exactly what I had to do to my 6F8G adapter - used a thin shielded cable for the grid/green/cap wire connecting the shield to (heater gnd) pin #4 internally in adapter case).


 
  Yes, the ground noise only comes from the 6F8G grid wire. I will replace it for a shielded one, connected to ground through pin 4, as you say.
   
  Don't you have microphonics with the 6F8G? I can listen a "bump" just by fingertapping at the table, far away from the CTH.


----------



## cfcubed

Googled and it seems 6F8Gs can be micro phonic, some say tube dampers can help, or very cushy feet under the CTH. I think any given tube can be micro phonic, perhaps try another?

BTW IIRC I used an old PC CD drive audio cable as it was thin and shielded and free. Guess a action of cheap RCA IC cable could work too.


----------



## dmcs414

That CTH pic is tha bomb.  
	

	
	
		
		

		
		
	


	



  
  Quote: 





>


----------



## dBel84

Dealing with radio interference can be a nightmare in tube amps - any trace can behave like an antenna. If I am reading correctly, it is worst with the 6F8G , so most likely a feature of the cable for the cap electrode. You could try screened / shielded wire but this will be a tough thing to address. 
   
  While on the subject of the 6F8G, I know a lot of people like this tube. Yes here comes the but... it is an early development of the 6SN7 and as such is less mechanically robust and is not as linear , thus there is probably a good deal of tube distortion ( harmonic ) that comes with this package. The noval equivalents of the 6SN7 are the 6CG7 or 6FQ7 tubes which are truly superb. Stax engineers used these tubes in their stat amps and having sampled a fair number of the various tubes, I can wholeheartedly encourage you to try these tubes. The 12AU7 is a 12v derivative of this tube and thus will have similar tonal characteristics , these you are all familiar with. 
   
  Please don't think I am saying that the 6F8G would be a poor tube choice, there is a reason people choose tube amps and in particular avoid "sterile" ss amps which have distortion measurements which are 5 decimal points below zero. 
   
  ..dB


----------



## Misterrogers

Working on another CTH using the same case that cfcubed did with his 'Fancy' CTH. I'm going to use Hovland SuperCaps, plus a Belleson Super Regulator to replace the 24V reg. I'm pretty excited to see what benefit I'll hear with this very clean, fast regulator. Does anyone have any experience with either of these two parts?


----------



## Mullet

I know Sachu has recommended the Belleson Super Regulator. I tried to get out of him what made the regulator so much better and never got an answer. I've also read that this regulator needs a larger case to fit. Don't know much about the Hovlands, but I do know that you really have to spend quite a bit on caps to really notice a huge difference with the CTH. I'm curious to hear about your impressions with both.


----------



## Misterrogers

+1. Did some reading on the Belleson, and the design/advantages make sense. I suspect that improving the power will improve sonics more than the cap up/side grade. I'll have to see about physical fit. If I need to, I'll cut an opening in the top and do a heatsink thing. With a little luck, I'll have it fired up before the end of the weekend.


----------



## sachu

Quote: 





mullet said:


> I know Sachu has recommended the Belleson Super Regulator. I tried to get out of him what made the regulator so much better and never got an answer. I've also read that this regulator needs a larger case to fit. Don't know much about the Hovlands, but I do know that you really have to spend quite a bit on caps to really notice a huge difference with the CTH. I'm curious to hear about your impressions with both.


 


  YOu get much better line and load regulation. Far lower ripple noise. All this translates to a cleaner supply to the output buffer section, better dynamics, extension on both ends of the spectrum and better detail retrieval due to the blacker background/low noise floor.
   
  I am expecting to receive some Salas shunt regulator boards shortly that i am planning on using to build a 24 volt regulator to use with the amp. However, with that it is no longer compact. The advantage of the Belleson is that its a direct drop in replacement, albeit might not fit in the standard case to to mechancial dimensions (mainly height in this case)


----------



## cfcubed

Quote: 





misterrogers said:


> Working on another CTH using the same case that cfcubed did with his 'Fancy' CTH. I'm going to use Hovland SuperCaps, plus a Belleson Super Regulator to replace the 24V reg. I'm pretty excited to see what benefit I'll hear with this very clean, fast regulator. Does anyone have any experience with either of these two parts?


 

 I'll also be interested in your work & findings WRT that Belleson Super Regulator.  Pricey, but not more than say 2 desirable tubes, performance comparison to our 24V reg is interesting 
  As you'll have 2 CTHs it'd be great if you could somehow keep everything the same in the two w/only 24V regs differing, for test/compare of just the regulator difference.  Maybe asking too much tho
   
  BTW I bought-back my "Fancy" CTH as the buyer wasn't able to get the "tubey"/rolled-off highs sound he was looking for & needed the $$$s for more important things.


----------



## Mullet

Thanks Sachu for the clarification. If I ever build a more substantial CTH in a larger case, I might consider this upgrade. Then again, it actually might not be hard to poke a larger hole in my perf metal where the regulator is located. Then again I'm quite happy with my CTH and might not feel the need to muck around with an already great thing.


----------



## sachu

Well the other option is to build it into a bigger case and use a Sigma11 or Salas Shunt regulator (or any such similar regulator).
   
   
  Again, this will significantly up the size of the amp.


----------



## dmcs414

Hey all,
   
  Happened to see this tube up for auction last night and it was just about to end with no bids, so I went ahead and bid .99 cents and won.  The ad said it was a Sylvania 6922. You can view the pic here- 
   
  The seller also said, "Tested on Sencore 154".  Anyone around here seen tubes that look like this?  Whether it ends up being the real deal and I just happened to win it cheap, great.  If it's bunk or fake, well figured it's worth the 7 bucks (includes shipping) to try and see; after all I could get lucky I suppose.  Be glad to hear you all's thoughts on this.  Thx!


----------



## Mullet

It is the real deal. I think other than Amperex, Sylvania was the only other company to make American made 6922s. The rest were rebranded Western European E88CCs. I don't think the Sylvania are the highest regarded of the 6922/E88CC variety of tubes, but they certainly aren't the worst. Heck $7 isn't a bad deal all around. Search this thread for favorites like the Amperex 7316 or 8416. Other favorites are the Siemens Chrome Plate ECC82. One of my personal favorites is the late 50's Amperex/Philips tall plate ECC82. Expect to pay $40-$50 minimum for a harder to find rare tube. Sometimes you can get great deals on a bunch of tubes and get a gem or two in the lot. Other things to look out for are rebranded tubes.


----------



## dmcs414

Ok one more time dear friends and mentors.  So,  I won an auction for these two tubes and just wanted to see if you guys have heard these and if you think I got a good deal.  I paid $52 for the pair, another 12 or so shipping.
   
  They were advertised as- _"*[size=small]PERFECT PAIR NOS AMPEREX ECC88 6DJ8 E88CC CCa BUGLE BOYS HOLLAND original 100% !"  WONDERFUL MATCHED PAIR of ECC88 / 6DJ8 / 6922 / Cca AMPEREX BUGLE BOY, made in Holland, early 1960! This is a FAMOUS Bugle Boy valve superlative for AUDIO performance, no microphonics, great sound imagine, stunning in voices and real open in mid-range. They’re in brilliant shape, admirable inner structure with LARGE ring getter. TOTAL FULL, BALANCED and MATCHED tests as follow: [/size]*_
_*T1= 17.3/18 and T2= 18.1/18.1 mA; 100% emission.*_

   
  What do you guys think?  If these turn out well, I think I'm done tube shopping for awhile.  I've got a Sylvania 6922 on the way, a replacement RCA C6G7 Clear Top for the one I bought which showed up minus a pin, and these two.  Any guesses as to which tube will sound the best with my Thunderpants?
   
  As always, this thread is indispensable.  Many thanks gents (and ladies, if you're there too)


----------



## Misterrogers

That's a fair price for a good tube. The large O BB's are a favorite of mine. Let's hope the perform as promised. 



dmcs414 said:


> Ok one more time dear friends and mentors.  So,  I won an auction for these two tubes and just wanted to see if you guys have heard these and if you think I got a good deal.  I paid $52 for the pair, another 12 or so shipping.
> 
> They were advertised as- _"*[size=small]PERFECT PAIR NOS AMPEREX ECC88 6DJ8 E88CC CCa BUGLE BOYS HOLLAND original 100% !"  WONDERFUL MATCHED PAIR of ECC88 / 6DJ8 / 6922 / Cca AMPEREX BUGLE BOY, made in Holland, early 1960! This is a FAMOUS Bugle Boy valve superlative for AUDIO performance, no microphonics, great sound imagine, stunning in voices and real open in mid-range. They’re in brilliant shape, admirable inner structure with LARGE ring getter. TOTAL FULL, BALANCED and MATCHED tests as follow: [/size]*_
> _*T1= 17.3/18 and T2= 18.1/18.1 mA; 100% emission.*_
> ...


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## Mullet

I like the Bugle Boys as well. They have a nice punch to them. I just won a BB for $10 on the bay. I'm sure it's not as nice as yours, but I didn't care if it had a nice label. My readings were around 13mA/13mA, so it's probably a used tube. I'm going to say the Bugle Boys sound best with Thunderpants. I find the higher gain 6dj8 type tubes perform better than the 12v 12au7s when using the Thunderpants. That RCA is a nice tube though, I just don't like it as much with the TP1s. My favorite tubes with Thunderpants are the Siemens ECC88, Siemens E88CC, Lorenz PCC88, Amperex BugleBoy ECC88, and Amperex 8416. I do have a rebranded late 50s Amperex 12AU7 long plate that is a top contender though.


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## Pingfloid

**** happens.
   

   
  [size=10pt]Fortunately I bought a pair for just 20$ 
	

	
	
		
		

		
			



[/size]
   
  [size=10pt]I find this cheap Westinghouse 6FQ7 to have similar sonic characteristics than the Raythenon or RCA 6F8G, and with the advantage of 9-pin base and no cap connector. This is great news, because I have not managed to get rid of the unbearable noise and microphonics from the 6F8G huge bottles.[/size]


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## dmcs414

Hey there CTH thread.  I've had a rather serious issue with my CTH and was hoping I could get some advice.  It started when my wife asked to take my CTH and headphones with her to Australia recently, with her firm assurances that she would be extremely careful in using & adapting for Australian power requirements, which are different than those here in the US.  I allowed her to do so.   This was, in retrospect, a grievous error on my part, but there it is.  
   
  When it came back to the US, my CTH would no longer power on, nor does it exhibit any response when the power button is pushed.  When I plug the wall-wart power supply into an outlet, the power light turns green and it appears to still be drawing power just fine.  My wife tells me she used an Australian coworker's power adapter in order to plug it in and was able to listen to my rig for a few moments, but reported that the sound was not right at all, and quickly turned it off.
   
  From this brief description, does it sound like my CTH may be fixable, or am I better off shopping for a new amp?   Could whatever happened to the CTH possibly also have damaged the tube (Amperex Bugle Boy Holland 6DJ8), or my headphones (Modded Fostex T50RP/Thunderpants)?  I tried my headphones through my FiiO E17 and they sounded OK, but that amp (At 6 Gain) doesn't really have the power the CTH does to make them shine.  Normally I use my FiiO E17 at 0 Gain and the CTH between itself and my headphones, primarily for the DAC and EQ functions the E17 has.   
   
  If the CTH might be fixable, what's typically involved in this type of endeavor and what might it cost me?  I should note, my CTH was built by MrSlim, who I messaged last week but hasn't gotten back with me as of yet.  
   
  If anyone's had experience with this sort of thing before, I'd greatly appreciate any advice you'd care to give.  Many thanks!


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## cfcubed

It sure reads like she used an adapter that simply mapped your CTH's 115V A/C adapter plug-pins to Australia's 230V wall plug, sending about 48VAC into the CTH that expects 24VAC.  
  That would be bad.  Would take a motivated DIYer some time to ID how much damage was done, working through its 3 PS legs (24VDC low voltage, 100V high voltage & 6.3V/12.6V heater circuits) & down-stream circuitry.  Then time, parts-pulling, testing, etc to possibly fix it (I'd think).
   
  BTW many/most newer *switching* *DC* power adapters accommodate 110VAC ~ 240VAC input & say so somewhere on the device.  CTH's adapter is an AC one, really just a transformer in a box.


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## sachu

am guessing she plugged in a DC power adapter and not the power adapter that you were supposed to use. Since you mention that she used an aussie cowroker's power adapter.
   
  Likely that it wasn't an AC adapter.


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## dmcs414

So the verdict is, as I feared, kaput.  Once I get a new amp, I'll see if anyone around here is interested in my CTH innards.  Poor little guy.


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## erikzen

Sorry for kicking a somewhat dead thread but I had a question and thought it might be better to ask here than start a new one.
   
  I have a small guitar practice amp that I'm very happy with except that it doesn't have a headphone jack for late night practicing.  It does however have a preamp out.  Can I run the preamp out of the guitar amp into the input of the CTH?  It would require the proper cable, e.g., 1/4" to RCA or 1/8" (I have both inputs on my amp).


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## cfcubed

If you start with the volume all the way down when you try I don't see that harm could happen. 
  When the volume is all the way down the CTH's input is swept to ground (it doesn't "see" any input).
  And the onboard e12 should trip if anything goes wrong. 
  IOW I'd give it a whirl, granted its lower risk for me because I'm a builder
   
  Edits:
  * If its a mono amp then the preamp out is likely mono too.  In which case your adapter(s) would need to link the preamp's single channel "+" to both the CTH's L & R "+"s (to hear sound in both earpieces).
  * With Joe Audio now offering CTH PCBs & kits ( http://joeaudiophile.com/shop/ ) the thread could see some posts. Tho most topics are already covered.


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## erikzen

Quote: 





cfcubed said:


> IOW I'd give it a whirl, granted its lower risk for me because I'm a builder


 
   
  And you're the builder of my amp also.  If the amp fails I'm going to track you down and try to get you to fix it.


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## mink70

I've been using the CTH with an Amperex Bugle Boy ECC82 to drive Audeze LCD-2s. The bugle boy has given me the most extended treble, from among Mullard, Telefunken and older Amperex tubes. Does anyone know of another tube that's even more extended in the treble, to balance out the LCd-2?
   
  Also, has anyone heard both the CTH and the Schiit Lyr and compared the sound quality?


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## Tribbs

cfcubed said:


> So, after seeing a couple tubes were tried in CTH that had other than 6.3v & 12.6v heater and found to work & sound good, knew there was nothing keeping the design from *directly supporting more heater voltages*.
> 
> 
> Nothing but a few more resistors & a way to switch among them.
> ...




Here's a dumb question!
How critical are these heater resistor values?

I could only source the following 1/8W values:

For *5.8k* > 5.828k? close enough ?
 " *7.4k* > 7.39k ? " " "
 " *9.3k* > 9.31k ? " " "
 " *15.1k* > 15k or 15.2k ? close enough ?
 " *23.3k* > 23.2k or 23.4k ? close enough ?

How close is close enough? Is it better to go up, down or simply the closest value?

I realize I can go 1/4W and/or add resistors but I don't want to piggy-back resistors to tweek the values as I'm trying to keep it Compact with the heater switch. Would like to stay with small 1/8W resistors.


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## cfcubed

tribbs said:


> Here's a dumb question!
> How critical are these heater resistor values?
> 
> I could only source the following 1/8W values:
> ...


 
  
 It is not a dumb question.   The values you've sourced may be the closest to the "calculated" values I came up with (& probably rounded to 0.1k). 
 IIRC the actual resistor values in CTH BOM did not exactly equal the calculated/ideal and had to be tweaked in-circuit. 
 Think it best to stick to a single resistor, use it & (carefully!) measure the heater voltage w/tube and see how close it is.  Found this quote "_The heater voltage of individual valves must be within ±7% of the rated value_" here:
http://www.vintage-radio.net/forum/showthread.php?s=8d6f8e40d2b17ab465c7eafdd2573736&t=59412
 Maybe order a couple/few resistors around the target values to be safe.


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## Tribbs

cfcubed said:


> It is not a dumb question.   The values you've sourced may be the closest to the "calculated" values I came up with (& probably rounded to 0.1k).
> IIRC the actual resistor values in CTH BOM did not exactly equal the calculated/ideal and had to be tweaked in-circuit.
> Think it best to stick to a single resistor, use it & (carefully!) measure the heater voltage w/tube and see how close it is.  Found this quote "_The heater voltage of individual valves must be within ±7% of the rated value_" here:
> http://www.vintage-radio.net/forum/showthread.php?s=8d6f8e40d2b17ab465c7eafdd2573736&t=59412
> Maybe order a couple/few resistors around the target values to be safe.




Thanks for the prompt reply CF3. I've been working on this amp in very intermittent spurts LOL.

Yes, I've ordered a few Rs. Your measuring tip is very useful - thanks 

BTW, I have printed out a full one page schematic I saved many years ago that indicates 7.15K for 6.3V instead of the above 7.4K (7.39K) next to the heater switch.
Do you know which is correct or...?

Edit: I just noticed BOM (3/20/2011) lists 7.15K, I have Xicon's on their way!

Many thanks for this and keeping up with the thread.


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## cfcubed

See you found it & edited your post about the CTH Rev A BoM:
http://cavalliaudio.com/diy/ctha/main.php?page=parts/excelbom
  
 Looking at BoM reminded me that "single resistor" in my post means single resistor in parallel with R1H:


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## Tribbs

If anyone has the time to help me debug a problem I posted in the other thread it would be greatly appreciated:
http://www.head-fi.org/t/398839/a-very-compact-hybrid-amp/2205#post_11416293


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## hpamdr

Thanks to  cfcubed giving me valuable information ! (see http://www.head-fi.org/t/542279/the-cth-compact-tube-hybrid-rev-a-thread/585#post_11661663)
  
  
 // i got some tubes and wanted to give a try as i remember the tubes being popular some years ago in cd/K7 output stage mods....
  
 I did a Star adapter for submini tube 6N16B-V  using noval socket saver and rigid copper cable.  I twisted the rigid coper to have the same order as the submini pin. if you want a better design, you could also use a Dip8 socket mounted/Soldiered on top of your noval socket saver and use other one to soldier your min-itube for easy rolling ! 
  
 I used the following Scheme :  

Noval PinSubMini pinDesc15A223G232K244H58H61A177G186K1
  
 As it is not easy to find pin order on the sub-mini this is how i do :
 1) you have to identify a *I* that point to pin 1 and 5 on the back side of the tuber.
 2) find which is which, pin 1 is in the same side as the tube printed label (on all the tube i got). But I also control if pin 4 and 8 are connected to the heater  (use a 6 V and see if red dot show-up )!
  
  
 Listening :
 No microphonic noise, no heating noise and do not need a very long heating time to give it best !
  
 This tube is for me a very good sounding tube which is fast and detailed. It haves:deep bass precise and well maintained,  the medium is very natural without emphasis, the treble is good but seems not so linear. 
 I did some test with my favorite music and cans and what i can say is that it is a very musical tube for the price  <5$ !
  
 For those who like 6SN7, 7N7, or 6cg7 you can find some similarities !
  
 I suspect it could be used as a very good driver in other amps than CTH


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## cfcubed

Thank you for the detailed info and impressions and its nice that it was worth the effort of doing.

A picture might be nice too but maybe its not too pretty Sometimes that keeps me from posting them.

I guess if one was so motivated they could make a really compact CTH going to SMD and supporting submini tubes. Would be lots of effort tho and you'd still need the A/C adapter.


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## hpamdr

You can get a picture on how it is uggly, for a VCTH as tube rolling will not be the most important feature, the design should probably be less compliated the power should be separated with a dual output one for the board and one for the heating  only 0.4A is needed and 6V is enough. you could cheat a bit with two boxes 
  
  
 I did called the adapter star, i should have said X'mass tree, the advantage of this is that is is very easy to test and soldier   Another point to highlight is that the gain is very good.  Tube life is somehow limited to 750h from spec but one of my firend have two tubes like this  on a modded nakamichi K7 player and never changed them during the last ten years....
  
33
  
 I also did a 7N7 Adapter and CTH is running very well with it but first try is very good  an CTH but need more time to better test it. If you have some interest i will post the adapter scheme Noval to 7N7 Loctal ( also some twist to do  )
44


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