# Melos Maestro modification log (updated Oct 05, 2008) - LARGE PHOTOS!



## FallenAngel

Hey guys,

 I've got a story to tell. Once upon a time, about a week ago, a certain FallenAngel saw a for-sale ad for a Melos SHA-Gold and snatched it for an incredibly low price. What arrived in the mail was actually the Melos Maestro and it damn rocked with the Grado RS-1.

 Of course, I couldn't help but to rip it open and see what I can do with it. So here comes the my modification log as a work-in-progress which will likely take a few weeks to complete.

 Modding Day 1:
 1) Remove "Pho-tentiometer" with cheap volume and balance controls
 2) Remove monitor switch and "Tape In" inputs, there are enough as is
 3) Install stepped attenuator

 Modding Day 2:
 1) Replace low-voltage bridge rectifier with FREDs 
 2) Reroute left channel using wire instead of PCB trace
 3) Replace IEC inlet with higher quality IEC with integrated line filter and install proper ground-loop breaker.
 4) Replace power switch and reroute "standby" to use the "Monitor" switch
 5) Install two quality 1/4" headphone jacks (the other in place of "Balance") 











 Modding Day 3: 
 1) Replace input caps with 1.0uF Vitamin Q
 2) Wire input caps to exactly where they need to go on the board instead of very long PCB trace for left channel (complete left channel mod)






 Modding Day 4:

 1) Low voltage PSU caps : Nichicon UHE / Panasonic FM
 2) High voltage PSU caps : Panasonic TS-HA
 3) High voltage 100uF/200V : AEON (Solen) 100uF! 
	

	
	
		
		

		
		
	


	



 4) Replaced High Voltage rectifier bridge with HEXFREDs
 5) Re-routed Headphone jack wiring






 Modding Day 5:

 1) BIG UPDATE, likely the FINAL for a while.

 Taking _nikongod_'s advice about moving the cap huge film cap, I have rearranged the caps a bit.

 1000uF TSHA is now 100uF Solen
 470uF TSHA is now 1000uF TSHA
 100uF Solen is now 470uf TSHA

 I figured that would increase capacitance by quite a bit, but no 10x in one place.

 Since I got the Sonicap 1uF, they were also installed. 4x for inter-stage coupling and 2x for Grid to Ground (opposite side of signal).

 Well, I if I might say so myself, it sounds absolutely incredible! The bass is through the roof with the RS-1 and the detail is incredible. By far the best I've ever heard the RS-1 sound. I prefer this to the Beta22, screw neutrality, RS-1 is mean to be FUN! 
	

	
	
		
		

		
		
	


	









 Next up, I don't even know yet. 
	

	
	
		
		

		
		
	


	




 Probably will swap out some RCA to nicer ones and perhaps rewire the amp. I like this amp so much as a headphone amp, I'm seriously considering removing the source selector and rewiring it as single-input, skip the source-selector and optimize the wiring. That's for another day though, this amp is getting closed for another day, it's been through enough that I will just enjoy it.

 Modding Day 6:

 Well, this thing didn't stay closed for too long. 
	

	
	
		
		

		
		
	


	




 I noticed some background hum, like a ground-loop and since I really didn't like the ground scheme of this amp anyway, I got to work. I isolated the headphone output, RCA input and PCB from the case and routed a ground-loop breaker from the "center" ground on the PCB to the case. The case is now earth-grounded. There is no more hum.

 I also removed ALL of the RCA inputs/outputs of the amp and made it into a single-input headphone amp. No selector switch, no extra wiring, and no pre-amp outputs (at least not yet, I can add them later if I decide to use it as such). The RCA input is a copper Vampire RCA and input wiring has been replaced with solid-core Cardas. The rest of the wiring is high quality mil-spec SPC. I also took the time to hot-glue the unused knobs back on, just for show. 
	

	
	
		
		

		
		
	


	









 ----

 Previous posts I've read and found most helpful:
http://www.head-fi.org/forums/f5/mel...thread-197603/
http://www.head-fi.org/forums/f5/mae...art-3-a-44134/

 Schematic for SHA-Gold
RapidShare: 1-CLICK Web hosting - Easy Filehosting


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## Pars

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_<snip>
 2) Low voltage PSU caps : Elna Silmic II / Nichicon KZ (perhaps other low-ESR), open to suggestions, will not consider blindly using BlackGate, must be a reason for choice.
 3) High voltage PSU caps : Open to suggestions
 <more snip>_

 

Panasonic TSHA are very good and go up to 450Vdc. They are snap-in; you didn't indicate form factor and looking at the picture those appear to be snap-in.


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## Killercrush

I found this page to be really helpful :

 Carlo's old page :

http://www.melosmods.netfirms.com/


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## nikongod

The gold and the maestro had the same PCB. The difference is that the gold ALWAYS came with the photentiometer and remote control, where the maestro did not.

 fwiw, the 2 potentiometers are not in the signal path AT ALL on the photentiometer. it is a photo-cell based attenuator, and was the upgrade to replace the cheap alps RK-40. I still prefer a stepped attenuator to the photentiometer or RK-40, although mostly because the photentiometer can *only* provide about 50db of attenuation as configured which is not enough for this amp (IMHO) and my RK-40 is not balanced chan-chan at the levels where I like to listen.

 It IS worth your effort to replace both of the rectifiers with ones made from fast switching & low-noise diodes (fred, hexfred, etc). The HV regulator used on the maestro/gold is AWESOME, but mosfets have trouble dealing with the HF "hash" from clicky diodes: in my amps this reduced a LOT of the background hiss without touching any of the HV power supply caps. I would do this BEFORE replacing any of the electrolytic caps. You will probably need to build a little daughter-board for these. 

 The SIZE of the coupling caps between the tubes (physical location on the board) is important, DO NOT go less than about 1.5uf, maybe 1uf. the input caps CAN NOT be removed from the circuit, but should be upgraded too. 

 do the left-channel mod.

 For the LV caps, I have heard that the "lone cap" off to the back right of the board (very close to a relay) has a big effect on the sound. I have not tried this, and it makes no sense according to the schematics I have, but I have received this info from a source I trust (he dosnt post here much) and it will only cost like $2 more to swap that cap too if your not using black-gates. Im not a fan of bypassing electrolytic caps with film, so I have removed most of the film bypass caps from my melos's. I am not 100% convinced that black gates are the end-all-be all choice for these caps, but whatever you get should be of very good quality.

 A choke in the HV supply (replace the 100 to 200 ohm resistor - depends when the board was populated) and a film cap to replace the last (largest) electrolytic round out the mods if you want to go totally ridiculous. I used a 100uf solen here, and it sounds like sex.


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## FallenAngel

Very cool, thanks for the info guys.

_nikongod_: A little help on 2 fronts.
 1) I'm a little lost on the FREDs here, I've still got some UF4004 left from the SOHA2 build, would these work or is there something better?

 2) Left channel mod? I've read it routes the signal away from the PSU, but I haven't checked under my PCB yet so I'm really not sure what this is going to look like at the end.

 Thanks for the link _Killercrush_ and thanks for the cap tip _Pars_, I've always been a huge fan of Panasonic FM caps, I'll look at how the TSHA look on paper.


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## FallenAngel

A little update. Both questions above still standing, I wasn't able to get a clear answer in my search yet.

 1) I was looking around and saw there are a pair of input caps on this amp. I am thinking that these will definitely be thrown out!

 2) After much searching I found the "left channel" mod. Just wanted to clarify: essentially, the 2K resistor above the inter-stage caps needs to be re-soldered to the underside of the board and the trace replaced with a direct wire.


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## dsavitsk

Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_the input caps CAN NOT be removed from the circuit, but should be upgraded too._

 

 Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_1) I was looking around and saw there are a pair of input caps on this amp. I am thinking that these will definitely be thrown out!_

 

.


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## nikongod

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Very cool, thanks for the info guys.

nikongod: A little help on 2 fronts.
 1) I'm a little lost on the FREDs here, I've still got some UF4004 left from the SOHA2 build, would these work or is there something better?_

 

they are pretty nice, but you can get MUCH lower recovery times than they have. This helps QUITE a bit.
  Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_A little update. Both questions above still standing, I wasn't able to get a clear answer in my search yet.

 1) I was looking around and saw there are a pair of input caps on this amp. I am thinking that these will definitely be thrown out!_

 

The stock caps are pretty much junk, but you MUST HAVE caps in these spots. Replace=OK, remove=no! I tried to run the melos without these caps, and nothing good came of it.

 If anyone cares (it has been asked before, and I didnt know the answer) the melos uses a combination of 2 things to bias the tube and split the phase for the balanced output. 

 The input stage is a long-tail pair BUT with a transistor configured as a constant current sink. The grid of the tube is tied to the bottom of a resistor but BETWEEN the resistor and the transistor. The grid of the tube is actually a few volts above ground, which dosnt matter because it is less than the cathode voltage. The fact that the grid of the tube is NOT at ground is what makes the caps mandatory.

 this photo illustrates it, although it shows a pentode where the melos uses a transistor, and the voltages are allllllll different. It does not show that the voltage on the cathodes of the signal tube is about 102V in this photo.




full site, good reading
  Quote:


 2) After much searching I found the "left channel" mod. Just wanted to clarify: essentially, the 2K resistor above the inter-stage caps needs to be re-soldered to the underside of the board and the trace replaced with a direct wire. 
 

For my left-channel mod, I broke the trace under the board (it makes a big s-shaped sweeping path around all of the power lines, which is how it picks up noise) near both the resistor and the mosfet. Then I soldered a wire on the TOP of the board, away from all of the power-lines.


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## FallenAngel

Thanks guys,

 I went with 8x MUR1520PBF for the diodes.
 EDIT: Oh ****! These are only 200V, guess I'll be buying something else for the HV bridge. But than again, the caps after the bridge are 200V, so I don't see any reason why these diodes won't work. Any hints?

 I'm bidding on 6x 1.0uF Vitamin Q caps on eBay (which are REALLY hard to find in 1.0uF values for some reason), hopefully to replace the 2 input caps and 4 inter-stage coupling caps. If I don't win those, I'll just go with Sonicap Gen 1 as I've had good results with them in the past and they're a great bargain.

 Thanks again for the hint on wiring the left-channel mod, I'll look at it tonight.


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## FallenAngel

Little update. I replaced the IEC socket with a nicer one that has a built-in line filter and implemented a proper ground-loop breaker from earth ground to the case.

 I also replaced the LV bridge with 4x MUR1520 diodes.

 Since I had a little trouble with the other set of diodes, I will be ordering another set of FREDs.


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## Blutarsky

I've had my Melos SHA Gold for about a week and already love it. 

 I plan to upgrade it to full maestrobator status at some point and have been looking through the old threads. Better to have an active discussion among other knowledgeable headfiers who are loving this very versatile piece of gear!

 Thanks for posting this discussion and the fantastic hands-on info you're sharing.


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## FallenAngel

Any thoughts on how to get rid of the "Mute" function? The switch wiring looks very funky and I can't understand what the little white wires are for.


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## FallenAngel

Ok, another update.

 1) I have replaced the power switch with a nicer one which also means I removed the weird wiring associated with it.

 2) Now there is a switch (placed where the "monitor" switch used to be) that selects whether pre-output is enabled or not (before it was done by whether headphones are plugged in).

 3) Since I don't use the balance control, I added another 1/4" headphone output.

 4) You can also see the little green jumper wire of the "Left Channel mod" wired on top as per _nikongod_ recommendation.

 Latest photo:


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## HiFi FOR METAL

You may want to consider intsalling a nuetrik powercon to replace the IEC, It helps with power phase and factor a great deal and also is non current limiting.


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## FallenAngel

Quote:


  Originally Posted by *HiFi FOR METAL* /img/forum/go_quote.gif 
_You may want to consider intsalling a nuetrik powercon to replace the IEC, It helps with power phase and factor a great deal and also is non current limiting._

 

Uhm... come again? How does it help "power phase and factor"? I just installed a nicer IEC socket with integrated line filter just because I wanted an easy way to have a line-filter installed.

 I think replacing this would be a distant concern whereas the signal stuff should come somewhat before. Still, I would definitely like to know why you think PowerCon is the way to go.


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## HiFi FOR METAL

PowerCon Does a few things that most connections cannot offer. 

 1. It has a twist and lock design that makes it impossible to jar loose, this means it has a more positive connection than IEC. 

 2. From what many manufacturers who design power products have told me it actually maintains power phase better than other products. Since power comes in +/-/ground it's phase can be corrupted. What that means it the 60Hz sine wave that power comes in is more in phase with itself. It is kind of like when you are using an antenna to get TV and the signal has ghosting effects. Obviously power phase need to be stable. 

 3. Its current bandwidth is far more stable and wider than IEC. You can get a 32 amp powerCon or a 20 amp. The benefit is that you won't be current limiting which is a good thing when it comes to audio products.

 4. It also offers better +/-/gound isolation in it's design which helps to minimize noise. and interference. It also has silver plated connectors. 

 5. PowerCon also uses a low capacitance connection which improves signal speed and flow. 

 Here is some more info from the neutrik site.

Neutrik - Industrial - PowerCon® 32 Amp 
Neutrik - Frequently Asked Questions


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## FallenAngel

Thanks, I have read up on it, but you do have to realize a few things.

 1) I don't have problems with jarring loose power cables 
	

	
	
		
		

		
			




 2) Power lines are actually not +/- to ground, they are AC(hot) to AC(neutral) and switches 60 times per second. The ground is earth ground and not actually used for anything other than safety. A balanced power supply will reference ground, normal AC lines do not.

 3) IEC is 10A or 15A; the Melos draws NOWHERE close to the limit

 4) No argument there, the design is likely better

 5) Uhm... yeah, sorry, that's bull. Neither connector will have absolutely any effect on the capacitance of the connection, there just isn't enough wire in close proximity to create that effect.


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## HiFi FOR METAL

I understand that you don't have a problem jarring power cables loose, but getting a positive connection does improve sound and IEC really has less of a positive connection, and less conductivity than powerCon. I also understand that the Melos doesn't run at 2OA, but having a wider current bandwidth including a 20A circuit does help with power, Sound staging is wider and dynamics are clearer. This is true even if the electronics receiving it are 15A. Since Current and voltage fluctuate and are reactive loads, things like resistance and capacitance effect how AC devices react. Having larger and more stable current above the demand of your components is a benefit. PowerCon does help with this as well. This is actually why products that operate on DC sound better because they aren't effected by current bandwidth limitations. All I ask is that you try it. Many manufacturers of equipment are starting to use this as their power supply connection simply because it does sound better. I mean it is only a 10$ solution, what would it hurt to try?


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## dsavitsk

Quote:


  Originally Posted by *HiFi FOR METAL* /img/forum/go_quote.gif 
_powerCon_

 

The beauty of the name is that it has Con right in it.


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## Uncle Erik

Why not replace the resistors? A lot of people overlook them for caps, but I change them out in my restorations. Granted, most of the stuff I restore has ancient carbon comp resistors, but good precision resistors help things.


 With one radio, I replaced the filters and recapped it, then powered it up every time after I replaced a resistor. A lot of radio guys stop after recapping, so I wanted to see if they made a difference. Each one made the sound clearer and more focused. I replace every resistor now.

 The cost is marginal, but it ups the labor. Still, if you want to wring maximum performance, look into a set of 1%, 105 degree resistors with twice the power rating of the stock ones. YMMV, of course, but I've had good enough results to keep doing this.


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## FallenAngel

_HiFi FOR METAL_ and _dsavitsk_: I really don't mean to get into a debate about this connector, it will be quite a ways down on my list of things to replace in this Melos as I have implemented a nice quality IEC socket with integrated line filter (which does have a measurable effect on quality of AC power). I might look into these types of Neutrik connectors for my balanced Beta22 build to send multi-channel DC from the PSU to the amp, but not likely for this build. Thanks for the recommendation though, I did read up on them.

_Uncle Erik_: I will very much consider replacing the resistors a little later, for now I want to "minimize the damage" of how the amp is designed and which parts are used currently.


 Next up is the High Voltage regulators and high voltage caps.
 Low voltage caps - so far I'm looking at Elna Silmic II or Panasonic FM.


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## HiFi FOR METAL

yeah, Most of the gear I have heard with the higher quality Vishay brand name resistors sound the best. In fact stepped ladder resister networks used for attenuation and volume control sound amazing on tube pre-amps. I also think Teflon caps are great as well, especially Auricap T. Solen caps are also good. Also you could replace the transformer with one from plitron it would probably be better than the one that is in there. Really there are a multitude of things you can upgrade. Personally I think it is about how it is executed. The execution is more art than science, but at the same time you have to account for all of the technical effects and measurements as well, not an easy task. One cannot just replace a resistor with brand name X and a capacitor with brand name Y and expect the heavens to open up, one really has to know how each thing will effect other things. It is sort of a balancing act.


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## HiFi FOR METAL

You could also try these. Hovland Company: Products: MusiCap Capacitors


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## FallenAngel

Well, I just got 6 Vitamin Q 1.0uF caps and they're unfortunately way too big to use for inter-stage without VERY creative mounting. Being the "can" type with no negative lead but just a solder spot on the end of the cap will also make it hard to isolate. I'll try to play with these, but if no possible, I'll just use a pair as input caps.


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## FallenAngel

Ok, two discoveries were made today

 1) 1.0uF / 200V Vitamin Q caps are HUGE!
 2) The Melos layout is STUPID! The input cap is on the other side of the input connection and runs right under the High Voltage regulators and around the board. I guess that's what the "Left Channel Mod" really is, not just the short jumper, but the input wiring which has a MUCH higher effect on lowering noise.

 So, updated to update the build log. Today I replaced the input caps with 1.0uF Sprague Vitamin Q and routed the input wires straight to the position where they are used, not through an extra few sets of connections (lower pins of #28 and #70 on PCB). The background noise has dropped considerably to the point that I cannot really hear it even when I try (although I will experiment with other headphones later). These input caps really sounds wonderful compared to the crap they had before.

 There is no room to use these as inter-stage coupling no matter what I do so I'll use something else for that position.

 Updated Photo:


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## dsavitsk

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_The Melos layout is STUPID!_

 

Do be careful as you do this. I replaced all the caps in mine (an original SHA-1), and something started oscillating. I've never tracked it down, and it sits on the shelf in the closet -- though to be fair, that's where it sat for years before I swapped the caps. I don't have any use for it other than I wanted one so badly when the came out that I won't get rid of it now, even if it doesn't get any use ... or even actually work. Someday I'll look at it again.


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## FallenAngel

Thanks for the warning Doug; this being the first time I'm tinkering with a tube design, I've been acting about as cautious as a person doing their driving test for the first time with a cop in the car.

 I have ordered parts to replace the high voltage regulators with HexFreds and all of the electrolytic caps with Nichicon UHE/Panasonic FM for low-voltage and Panasonic TS-HA for the high voltage. Values are taken from the SHA-Gold schematic (a little larger size than on my Maestro).


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## FallenAngel

Ok, I'm taking the next step in ordering caps to replace the 4 inter-stage 1.0uF caps (which are actually in parallel so they act as 2uF combined). My top choice for bang/buck is the Sonicap Gen 1 1.0uF/200V but I saw another pair of caps that caught my attention. There are two other caps that work inline with the theoretical negative input to the signal and run from Ground (signal ground, PSU ground, case ground, all same in this amp) - and connects to the *Grid* of one side of the tube just as the signal connects to the other Grid. Somehow this cap seems a little important and I'm wondering whether it should be replaced or not. Comments greatly appreciated as I'm completely lost in tube theory.

 I'm also looking at changing the pre-amp output caps and really don't see why they would be rated at 250V. Looking at the schematic there is a 10uF cap bypassed by 0.1uF. I'm thinking Sonicap for both - Gen1 10.0uF/200V bypassed by Gen2 0.1uF/200V - as long as 200V is enough. Taking a measurement across that cap is impossible - I don't see any voltage! 0V!

 Thanks


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## nikongod

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Ok, I'm taking the next step in ordering caps to replace the 4 inter-stage 1.0uF caps (which are actually in parallel so they act as 2uF combined). My top choice for bang/buck is the Sonicap Gen 1 1.0uF/200V but I saw another pair of caps that caught my attention. There are two other caps that work inline with the theoretical negative input to the signal and run from Ground (signal ground, PSU ground, case ground, all same in this amp) - and connects to the *Grid* of one side of the tube just as the signal connects to the other Grid. Somehow this cap seems a little important and I'm wondering whether it should be replaced or not. Comments greatly appreciated as I'm completely lost in tube theory._

 

The cap which goes from the grid of the tube to ground (the other one should connect to signal input) is of questionable importance (quality wise). It is necessary as part of the phase-splitter, but is not DIRECTLY in the signal path. In my amp, I left this as the solen that was in there when I got the amp. I have not tried to replace this cap but SERIOUSLY doubt that it has much effect on SQ.

 Replacing the actual signal input cap and interstage cap made a HUGE difference in sound. I upgraded from the solens, and was very pleased. With the craps (hehe) in your amp you should be absolutely amazed.
  Quote:


 I'm also looking at changing the pre-amp output caps and really don't see why they would be rated at 250V. Looking at the schematic there is a 10uF cap bypassed by 0.1uF. I'm thinking Sonicap for both - Gen1 10.0uF/200V bypassed by Gen2 0.1uF/200V - as long as 200V is enough. Taking a measurement across that cap is impossible - I don't see any voltage! 0V! 
 

They DEFINITELY have voltage across them. They are between the emitters of the preamp mosfets and the outputs of the amp: It is probably 75-85V - it is the same as the voltage across any the BIG blue resistors on the bottom (towards the front of the case) between the 4 mosfets.

 You can use 200V rated parts anywhere in the amp.


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## fzman

paralleling two identical caps in the signal path may not work out quite how you want it to -- it may cause a subtle blur that using dissimilar values in parallel may not create -- if you have the resources, try it both ways before you spring for the $$$ caps.

 just my 2 cents worth....


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## nikongod

Quote:


  Originally Posted by *fzman* /img/forum/go_quote.gif 
_paralleling two identical caps in the signal path may not work out quite how you want it to -- it may cause a subtle blur that using dissimilar values in parallel may not create -- if you have the resources, try it both ways before you spring for the $$$ caps.

 just my 2 cents worth...._

 

From my experience that is backwards.

 Paralleling caps of dis-similar values causes the blur.


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## dsavitsk

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_My top choice for bang/buck is the Sonicap Gen 1 1.0uF/200V_

 

This is what I used, too.

  Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_I'm also looking at changing the pre-amp output caps and really don't see why they would be rated at 250V. Looking at the schematic there is a 10uF cap bypassed by 0.1uF. I'm thinking Sonicap for both - Gen1 10.0uF/200V bypassed by Gen2 0.1uF/200V - as long as 200V is enough._

 

I think you ar right that there is no voltage on them as the pre outs (at least on my SHA-1) are right after the phone outs. The reason there are caps is that the amp can have a small amount of offset. This is not problem for headphones, but since the next stage could amplify it, it is standard to put coupling caps to prevent that possibility. They probably are rated high voltage because nobody makes low voltage film caps.

 The real question is why you would want 10uF, or a bypass. If you won't use this as a preamp, skip these. If you will, figure out what the next stage Zin is, and replace them appropriatly.

  Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_The cap which goes from the grid of the tube to ground (the other one should connect to signal input) is of questionable importance (quality wise). It is necessary as part of the phase-splitter, but is not DIRECTLY in the signal path._

 

To the contrary, they are directly in the signal path and matter as much as any others.


  Quote:


 Paralleling caps of dis-similar values causes the blur. 
 

I agree with this. Indeed, paralleling same values sometimes can improve things and is why Multicaps work. I have tried paralleling Vitamin Q's, for instance, with very good luck.


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## nikongod

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I think you ar right that there is no voltage on them as the pre outs (at least on my SHA-1) are right after the phone outs. The reason there are caps is that the amp can have a small amount of offset. This is not problem for headphones, but since the next stage could amplify it, it is standard to put coupling caps to prevent that possibility. They probably are rated high voltage because nobody makes low voltage film caps._

 

The preamp outs on the SHA-gold are set up differently than on the SHA-1.

 The gold runs the mosfets for the preamp from the high voltage supply, they are totally separate from the headphone amp. The caps should be blocking some wicked DC offset here.
 The SHA-1 uses the headphone driver for its preamp out. There should be virtually no offset.
  Quote:


 To the contrary, they are directly in the signal path and matter as much as any others. 
 

They are just there to hook the non-input side of the long-tail-pair to actual signal ground. Does the signal "reflect" through the grid of the "non-driven' side?


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## dsavitsk

Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_The preamp outs on the SHA-gold are set up differently than on the SHA-1._

 

Interesting

  Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_They are just there to hook the non-input side of the long-tail-pair to actual signal ground. Does the signal "reflect" through the grid of the "non-driven' side?_

 

Signal travels in a loop, not a line, so you need to account for the return signal. A cap connection allows AC and blocks DC, or indeed any DC reference. The only reason to cap couple something is because you want signal to go through it. Try disconnecting it and see what happens. Or, try connecting it with a 10pF cap and see where the frequency response goes.


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## FallenAngel

Great discussion here guys - to be safe, I'll order another 1uF/200V Sonicap Gen1 (I really love the price for this size, $5.80 is a steal!) for that position, getting very excited now.


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## nikongod

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Signal travels in a loop, not a line, so you need to account for the return signal. A cap connection allows AC and blocks DC, or indeed any DC reference. The only reason to cap couple something is because you want signal to go through it. Try disconnecting it and see what happens. Or, try connecting it with a 10pF cap and see where the frequency response goes._

 

So I tried this, and at the very least agree that the caps cant be removed from the circuit (even without jumpering, just leaving them out).

 I disconnected one of the "non-driven side" caps from ground, and let her rip. I was expecting at worst a few db drop on that channel, but got no music, and a decent bit of static which did not change with volume knob position. I did not try to replace the cap with a small ceramic.

 It is clearly the case that the caps are necessary even in this position, and probably passing the signal, but I dont understand why. The caps are obviously blocking DC between the grid and ground, but the grids have leak resistors. Why dont the leak resistors provide enough reference for the tube to run properly? 

 I suppose I will cede defeat in this debate (although I have gained knowledge to improve my gear: I win!) but would GREATLY appreciate any information on why this works the way it does.

 on the note of the preamp caps, and stuff:
 I measured my preamp outs, the caps are holding back about 80VDC.
 I would say that the 10uF caps are necessary as a GENERAL design item: a single ended amp with a 10k-ohm input impedance needs them to keep all effects of the low-frequency roll off out of the audible range. They are overkill for the balanced outputs, but since they should both be the same... you can use less if you dont want to drive an amp with a 10k-ohm input impedance.


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## FallenAngel

Very cool.

 6x Sonicap Gen1 on the way for coupling and the Grid-Ground position. Too bad I can't fit the Vitamin Q in there.

 The other 1uF caps look like they're for the PSU - any suggestions for those? I'm looking at some normal quality BC MKT but is it even worth it?


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## dsavitsk

Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_ but would GREATLY appreciate any information on why this works the way it does._

 

The short answer is that the second grid is AC coupled to signal ground. Otherwise, what would that side of the tube be doing? The only real difference between balanced and single ended signals is that in single ended one side of each is tied to ground, that is, they are referenced to the same thing. In balanced they are separate. So, since this is splitting the signal, you need the second side of the signal to come from somewhere. Look at the Schmidt splitter here.

 A better link: http://www.freewebs.com/valvewizard/acltp.html


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## FallenAngel

Well, I've been BUSY today! I finished a Dynalo and a custom PSU for it, just needs casing, then finished building a MiniMAX prototype which is also awaiting casing, then I destroyed the unbalanced outputs of my ESI Juli@ with a bad opamp replacement, hopefully the balanced still work (opamps also replaced with AD8022 in MSOP packages) and then I started on the Melos. Whew.

 So the replacement caps came in today. The values are from the Melos SHA-Gold schematic.

 Low-Voltage caps are Nichicon UHE and one Panasonic FM
 High-Voltage caps are Panasonic TS-HA except I took _nikongod_'s recommendation about the 100uF/160V cap and replaced that with a 100uF/250V AXON (Solen) cap. I don't know about it "sounding like sex", but the amp does sound pretty damn good. I'll wait for everything to burn in for a while before passing judgment but so far it's very nice and dead quiet in terms of background noise.

 One weird thing I noticed is that the old caps I took out are so much lighter than the new ones I'm putting in. They feel like paper compared to the new ones.

 Finally replaced high-voltage diode bridge to HEXFREDs.

 I also took the time to reroute the headphone jack wiring more "directly" instead of around the entire case.






 Ok, now it's almost 4am and I have to go to work tomorrow. 
	

	
	
		
		

		
		
	


	




 I'm going to sleep.


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## nikongod

very nice indeed 
	

	
	
		
		

		
		
	


	




 A capacitors capacitance is totally over-rated when dealing with tube power supplies. Quality>>quantity.

 Although its more work (hehe there is always more work) I would move the film cap.

 The cap near the "M" in melos is should probably be the film. The one where it is now is before the voltage regulator. The one near the M feeds the tubes. Swapping them should do amazing things for the sound.

 When I moved parts from my SHA-1 back to my Gold, I didnt put the film cap back. I miss it.


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## FallenAngel

Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_very nice indeed 
	

	
	
		
		

		
		
	


	




 A capacitors capacitance is totally over-rated when dealing with tube power supplies. Quality>>quantity.

 Although its more work (hehe there is always more work) I would move the film cap.

 The cap near the "M" in melos is should probably be the film. The one where it is now is before the voltage regulator. The one near the M feeds the tubes. Swapping them should do amazing things for the sound.

 When I moved parts from my SHA-1 back to my Gold, I didnt put the film cap back. I miss it._

 

Are you sure that 100uF is enough? Schematic shows 1000uF for that position and if I just swap them,Ii'll be swapping 1000uF and 100uF?! Sounds a little dangerous.


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## FallenAngel

With the completion of a couple of cable projects and a Dynalo, I finally got some time to work on the Melos.

 Taking _nikongod_'s advice about moving the cap huge film cap, I have rearranged the caps a bit.

 1000uF TSHA is now 100uF Solen
 470uF TSHA is now 1000uF TSHA
 100uF Solen is now 470uf TSHA

 I figured that would increase capacitance by quite a bit, but no 10x in one place.

 Since I got the Sonicap 1uF, they were also installed. 4x for inter-stage coupling and 2x for Grid to Ground (opposite side of signal).

 Well, I if I might say so myself, it sounds absolutely incredible! The bass is through the roof with the RS-1 and the detail is incredible. By far the best I've ever heard the RS-1 sound. I prefer this to the Beta22, screw neutrality, RS-1 is mean to be FUN! 
	

	
	
		
		

		
		
	


	









 Next up, I don't even know yet. 
	

	
	
		
		

		
		
	


	




 Probably will swap out some RCA to nicer ones and perhaps rewire the amp. I like this amp so much as a headphone amp, I'm seriously considering removing the source selector and rewiring it as single-input, skip the source-selector and optimize the wiring. That's for another day though, this amp is getting closed for another day, it's been through enough that I will just enjoy it.


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## mwofsi

Nice work FallenAngel, glad it's turned out so well. That Sonicap arrangement between the valves is great. Any chance of a pic or two of the whole thing?


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## FallenAngel

Thanks. I'll take a full pic later on, it's finally closed for the first time in over a month and I like it that way. To get a good impression of it though, just take a look at the last two photos and combine them .
	

	
	
		
		

		
		
	


	




 I also realized I might not last too long before going forward with another upgrade I've been thinking about, the PSU film caps. What would be a good option for these? I'm thinking the Wima MKP4 would be a good choice but I don't have any on hand (although that can change very quickly); I do have some BC components MKT and MKP caps that I can use. Any opinions?

 Thanks in advance.


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## FallenAngel

PSU film bypass recommendations anybody? 
	

	
	
		
		

		
		
	


	




 I'm going to place an order with Mouser very soon, will likely go with MKP10, same as the Millet Hybrid MAX design. Just have to make sure to measure size.


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## John E Woven

It looks like it sounds fantastic. But, I must ask; will you ever consider modifying my sha-1 to the same standards or so?


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## FallenAngel

Quote:


  Originally Posted by *John E Woven* /img/forum/go_quote.gif 
_It looks like it sounds fantastic. But, I must ask; will you ever consider modifying my sha-1 to the same standards or so? 
	

	
	
		
		

		
		
	


	


_

 

Thanks, it does sound very nice.

 Well, if you _must_ ask, I must answer, nope, never considered it.


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## rds

looks very sweet


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## FallenAngel

1) Rewired the ground scheme.
 2) Rewired amp into single-input with quality parts

 Full info and photo in first post


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## PrzemekDraheim

Hello, sorry to make a double post (I have posted this question in another thread as well) but time is important and I need to act fast as I have an offer to buy myself a Melos.

 I live in Poland with voltage of 230V and 50 Hz.

*The question is:* can I use Melos SHA-1 in Poland, with a simple voltage converter/transformer? Or should I expect hiss, hum, noises or booooom?

 Also, *if I can't use* Melos with voltage transformer is it possible to change the power unit in the amp for the European one without breaking it? Of course this would be done by people who are experienced in building DIY amps.

 Please, if you can help me, share your knowledge as I need to know the answer very fast.

 Thank you!


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## PrzemekDraheim

Guys, anyone?

 I really need to know if Melos SHA-1 can handle 50 Hz instead of 60 Hz.


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## Pars

I can't really give you an answer as I don't have a Melos. I did download a schematic and in that, the transformer is shown as a dual primary, which is typical for international (ie. both 110V and 220V operation). The schematic showed the primaries in parallel, as they would be for 110V use. 

 I cannot tell for sure from FallenAngel's pics and can't read the label on the xfrmr... you might PM him and see if he could tell you?


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## FallenAngel

On my unit the transformer has dual primaries, but one pair of primaries is connected to the PCB so I'm not sure that it'll work using them in any other way. Perhaps there are different transformers for the Melos.


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## Pars

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_On my unit the transformer has dual primaries, but one pair of primaries is connected to the PCB so I'm not sure that it'll work using them in any other way. Perhaps there are different transformers for the Melos._

 

That seems strange... is it an actual pair, or is it one lead of each pair? If the latter then that may be how they switch the primary wiring for 110 or 220? The schematic I grabbed was for an SHA1 Gold and doesn't show the other primary being used for anything but as a parallel primary for 110V use...

http://www.eserviceinfo.com/equipment_mfg/Melos_32.html


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## PrzemekDraheim

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_That seems strange... is it an actual pair, or is it one lead of each pair? If the latter then that may be how they switch the primary wiring for 110 or 220?_

 

That would be cool.


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## FallenAngel

Yes, the same schematic is posted in the first post of this tread, I'm simply saying what I have in my amp.


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## Pars

Ooops, missed that you had a link to the schematic when I was looking at the pics.

 PrzemekDraheim: please do not use anything I have speculated on in making a buying decision. You will need to do your own research as to whether the Melos you are looking at will support 220V 50Hz operation or not.


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## PrzemekDraheim

Thank you guys for all your input and the time you spent on research and posting. 

 I have pulled the trigger and bought that Melos. $349 seems to be a good price, I think. I have made many calls today and some companies that work with modding audio gear in Poland told me that all I need is a good voltage transformer with the right wattage, just like Fallen Angel told me. Also, I talked to some audiophiles in my area and they told me they want to buy that Melos from me. So if it doesn't work, I will sell it. Lets hope it will reach me in one working piece. I will let you know how things turn out.


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