# stepped attenuator rotary switch mechanisms



## morsel

I would like to hear comparisons of stepped attenuator rotary switch mechanisms, specifically with regards to the feel, how easily and quietly they rotate, whether they generate any electrical noise, mechanical noise, are they make before break, etc. These are the rotary switch mechanism and stepped attenuator makers I know of:

Elma used by Elma, DACT, Goldpoint, HeadRoom 



 


 


 


 

Grayhill used by Octave, DIYzone








TKD











fake alps






 The fake Alps is dreadful. Ridiculously high rotational force is required. It is both mechanically and electrically noisy with break before make contacts.


Shallco 







Electroswitch

 (too many styles to show)


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## timoteus

I am using a Seiden make before break switch on my current project. The "feel" of this switch is nothing short of amazing. When you add a very heavy stainless steel Dact knob the feel becomes even better. I wish I had this switch on every piece of equipment I own.











 John Chapman of Bent Audio carries this Japanese switch for US $150 but is going to discontinue it because the exchange rate is going to drive the price to $200. He will carry the Shallco instead which he considers to be of equal quality. He has said that the detents on the Shallco have an industrial feel to them which he is working on modifying.

 The only two switches I have compared directly are the Seiden and Dact. The Seiden has a silky smooth soft detent with just the right amount of resistance. The Dact has a hard edge click to it and feels a little sloppy in comparison. This of course has nothing to do with the quality or sonics of the switch. I'm just commenting on their tactile qualities. Hope this helps a little.

 Edit: You can read more about the Seiden switches here.
http://bentaudio.com/parts/diy.html


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## ITZBITZ

I used the Elma switch.

 The action is very smooth and voodoo who's finished his says there is no contact bounce. It's a make-break switch, so it seems it should be quiet. Also, the ladder switch is pretty easy to solder up, although I'm only have done with mine (after 3 hours of cutting, forming and soldering). 

 The turning force is smooth, but has solid thunks between steps. I laid out a custom taper to make sure I had enough divisions in the area of volume I listen to the most. I think I posted that spreadsheet in the thread about the elma 5 wafer switch.


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## Voodoochile

I like the Elma a lot. It's not only the make-before-break, but it is also fitted with different contacts designed specifically for zero bounce, even if turned quickly. Very resonable turning torque, and it's a rugged assembly.

 I also have a pair of the fake alps attens, and they do suck indeed! I had one in a plastic box with pigtail leads for bench testing boards (because it sucked too much to be part of an amp), and it's too noisy and frustrating to use for that, even. 
 If it was free, it would still be overpriced.

 I don't own, but have tried the Shallco 45-position switch-based series attenuator, and it is very nice. But the thing is pretty big, and they don't seem to readily have a switch with enough decks to easily make a ladder. You could do it, but the diameter would be *huge*. But the switch is wonderful. The torque required is a bit greater than the Elma, as you might expect, but still reasonable. A chassis big enough to hold the Shallco would easily allow the use of a 1.75" or larger knob without looking goofy. That makes a good difference in the feel.

 A pic of the Elma 5-deck ladder switch, built with Holcos:


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## morsel

Can anyone comment on Grayhill .vs. Elma?

 In another thread I used Babelfish to translate a German pot site. There is some fascinating detail on a TKD CP2500 pot describing the laser trimmed multisegment resistive element. They suggest it is so good they no longer use Elma stepped attenuators. Note the separate parallel trimming elements that tie in to the main element at each logarithmic junction. This is a pot constructed like a stepped attenuator. Has anyone tried these?


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## hadron

Haven't tried the TKD pot, but the 2P-65CSxx 40 step attenuator is very nice. Just the right amount of torque needed and a good detent feel, though a bit loud since it uses a spring-loaded ball and a notched disk.


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## JohnFerrier

Hmm.


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## fyleow

Morsel what about the Alps Black Beauty? It's still available from some places I think, I used one and got it from Percy when I built my Gilmore. It did not have the same problems as the fake blue alps you mentioned, but when I checked it with my Fluke I was not impressed by the resistance matching of the two channels.


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## morsel

I should know better than to derail my own threads. 
	

	
	
		
		

		
		
	


	



 I'm still hoping for feedback on the Grayhill mechanism.
 Great pix, everyone, thanks for posting!


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## fiddler

I wonder which one out of these has the best price/performance ratio? When I get the funds, I'm planning to build a PPA... probably first with an Alps Blue but I'm leaving it off the board for an easy upgrade to a nice stepper. Or I'll just build the stepper from the start if it's affordable enough.


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## Voodoochile

Quote:


 _Originally posted by fyleow _
*Morsel what about the Alps Black Beauty? It's still available from some places I think, I used one and got it from Percy when I built my Gilmore. It did not have the same problems as the fake blue alps you mentioned, but when I checked it with my Fluke I was not impressed by the resistance matching of the two channels. * 
 

I believe those are detented volume pots. I have one from Mike and that is exactly what it is. It's a nice pot than the Blue, but not by much. Just has that clicky feel to it, which I find odd. You get the disadvantage of steps, but not the advantage of a cleaner signal path.
	

	
	
		
		

		
		
	


	




 I think Mike says that some are detented and some are not. Can't have a stepped attenuator without detents.


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## Pars

Quote:


 _Originally posted by morsel _
*Can anyone comment on Grayhill .vs. Elma?

 In another thread I used Babelfish to translate a German pot site. There is some fascinating detail on a TKD CP2500 pot describing the laser trimmed multisegment resistive element. They suggest it is so good they no longer use Elma stepped attenuators. Note the separate parallel trimming elements that tie in to the main element at each logarithmic junction. This is a pot constructed like a stepped attenuator. Has anyone tried these?




* 
 

Morsel,

 I have one of these CP2511s in my Counterpoint preamp, and it is very nice, response and action-wise. Mike Elliot (of Counterpoint, now Alta Vista Audio) uses these in his Counterpoint rebuilds (www.altavistaaudio.com). Note that TKD also makes an actual stepped attenuator... Michael Percy carries it.

 Chris


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## 00940

Quote:


 _Originally posted by morsel _
*I'm still hoping for feedback on the Grayhill mechanism.
* 
 

iirc,, Antness has been using it in his last amps. Recent customers could inform you.

 btw, it's also used in the pathos amps : http://www.pathosacoustics.com/indexeng.htm


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## morsel

Grayhill comments, anyone?


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## doobooloo

Where can I get these Grayhill rotary switches, not as a complete/kit stepped attenuator but just the switch alone?

 Also, usually - how is the resistor matching in preassembled/kit stepped attenuators? Even in worst case, is it anything to worry about?


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## doobooloo

Nobody knows where to get the Grayhill rotaries?

 I just emailed the eBay seller kyc111 who has been making these DIYZONE-type attenuators and selling them for a reasonable price (http://cgi6.ebay.com/ws/eBayISAPI.dl...sort=3&rows=50) to see if he was willing to sell the switches only.

 I am wondering if it's possible to buy directly through the link mentioned in the DIYZONE article (http://www.my3c.net/product/detail.a...=&Sort=&Price=)... Does the site (My3C.net) ship internationally? The kit includes a very nice, heavy-looking sand-blasted knob and if the price is in NTW it is an awesome price, if it is in RMB then it's comparable to the eBay seller...

 At any rate, I'll update this thread as soon as I hear from this guy. Maybe we can arrange a group buy? (I'm looking to get at least two myself)

 -doosik


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## morsel

Try Octave Electronics, it is where I posted the pictures from.


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## doobooloo

I just got a reply back from the seller, and he is selling them at $11 per switch - much lower than what I initially expected!

 But my question is - are the ones that he's using genuine Grayhills? It seems to have a different shaft length (longer) than the one pictured at Octave.


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## was ist los?

Hrm... the ebay one does not appear to have the Grayhill logo on the back. 
 Doo - when you asked, were you referring to stereo or mono switches?


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## doobooloo

Well from the pictures on Octave we can't tell whether their blue switch has a grayhill logo on the back or not. Can someone with a genuine Grayhill switch confirm this?

 Also, I am almost 100% sure that they're stereo switches, since all his auctions are for stereo ladder type attenuators. I will ask him though, just to be sure.


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## meat01

Don't know if these are the same ones you guys are interested in, but but Digikey sells a Grayhill Stepped attenuator. It is part number GH7104.


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## was ist los?

I would be interested in buying a few of these switches. Maybe we could convince him to put the switches themselves for auction since i would feel more comfortable if it is official ebay.
 Your right about the logo on both, we can't assume there is a logo on the Octave one. The do both have the little plastic nub on the front.


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## doobooloo

Quote:


 _Originally posted by meat01 _
*Don't know if these are the same ones you guys are interested in, but but Digikey sells a Grayhill Stepped attenuator. It is part number GH7104. * 
 

That's not the Grayhill we're interested in. I don't think any of the major vendors stock this part or the higher end part mentioned in Octave's website.

 I just emailed the seller again requesting an official eBay posting of the item and perhaps a lower price on group buys. I'll keep you guys updated. I don't know how much of a price benefit we can get from a group buy though, I mean, at $11 a piece...


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## morsel

For $11 why not just buy one and check it out?


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## hubcaps

There's a thread on this attenuator on diyaudio.com. It's not a grayhill, and it's suppose to be kinda noisy. Check it out here:

http://www.diyaudio.com/forums/showt...5&pagenumber=1


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## doobooloo

Well someone on that forum seems to like the feel and torque even more than the Elmas! 
	

	
	
		
		

		
		
	


	




 For $11, I am definately trying at least one out, very soon.

 [edit]

 Also, the seller kyc seems to be a member of diyaudio...


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## morsel

What a confusing mess in that intriguing thread at DIYaudio. There seem to be many contradictiing statements and more than one model of similar appearance.


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## hubcaps

Peter Daniels was the one who did a through examination of these. He's experimented with a lot of attenuators, so I think he's the only person worth looking at. In other threads, he's said they sound really good. It's just that it's noisy when you turn it. Good bargain if you don't constantly change the volume. I think most people don't, it's just that the sound is unpleasent and annoying.


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## s.c

PPL in Diyaudio.com said the ebay one is break b4 contact/make before break ( I don't really know) type, so it just literially break every time when you turn the volume, and it create a gun poot noise when you turn your knob.
	

	
	
		
		

		
		
	


	




 I think HeadFier don't want that happen when the headphone is much closer to ears.


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## 00940

i tried them.

 There's indeed a clicking noise if you turn them quickly. When turning very slowly, there's no real problem, just a small pop. Peter Daniel is probably right, it looks like a bouncing problem.


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## doobooloo

Hmm...

 The ebay seller asked for my eBay name and when I emailed it to him he hasn't replied yet...

 In the meanwhile, BrianGT of diyAudio is organizing a group buy on the Series R Elma ladder attenuator - and he says the entire attenuator will cost less than $90 with resistors! 
	

	
	
		
		

		
			





 What a deal! Here are two images he posted:











 I have signed up for one of these units... 
	

	
	
		
		

		
		
	


	




 [edit]

 Link to thread: http://www.diyaudio.com/forums/showt...5&pagenumber=1


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## morsel

A word of warning about that design: It appears heinous to assemble, with no room for error, as one would be hard pressed to get it apart again once soldered. While they are slightly less cool looking and more bulky, ladder attenuators without captive resistors are more readily serviceable.

 I like the concept of ladder attenuators, but the Elma or HeadRoom series attenuators with SMD resistors have a short signal path, are less complex, and replacing a resistor or two is not so bad.


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## doobooloo

But, the question is, how often would I need to replace resistors once assembled successfully?

 I guess there is a risk of putting a wrong resistor in during assembly and realizing only after I've soldered everything in, but I think the chances of that are rather low...


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## morsel

You may find you want to rescale the dB steps someday. And anyone can make the mistake of putting in the wrong resistor. It happens to the best of us.

 Moderators, there is a bug in the web forum software that is mangling the URL for the Elma series attenuator in my previous post by inserting a <BR> in the middle of it.


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## JohnFerrier

Agree: tedious amount of soldering. Not for everyone. Make sure they go in the right order. *Check twice, solder once.* "Voodoochile" spent 7 hours assembling his. I think he bettered my time by a few hours. I assembled mine yesterday...finished 2:00am this morning.
 Voodoo's thread: http://www4.head-fi.org/forums/showt...threadid=60553

 Disagree: short signal path. Sounded good when I read that several months ago, but thinking about it now, not sure what the benefit is. These are resistors. Inductance of any extra lead length is on the order of micro-henrys and lead capacitance will be lower than 1pF. As far as resistance, the most important aspect is that they match left and right...so if the leads are the same... Not sure why someone would need to replace SMT resistors...not a wide selection with similiar form...

 Holco resistors are nice, though probably hard to find all values with old stock values (OS supposively equals non-ferrous end caps). Old stock parts have thicker leads. New stock parts seem to be more accurate. I imagine Roederstein parts would be very good too.

 Grayhills: no news.


 JF


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## morsel

Quote:


 Not sure why someone would need to replace a SMT resistor... 
 

As I said, you may want to rescale the dB steps someday. I was not suggesting "boutique" SMT resistors. See you in 3 weeks, I'm going out of town and will not have much Internet access.


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## JohnFerrier

Agree: there probably are cases that the scaling is not perfect. Guess a person should try to get the db scale right the first time. However, it not easy to know in advance what all the requirements are...

 Enjoy time away.


 JF


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## doobooloo

The difference between the Elma switch Voodoochile used and the one pictured above is that the PCB board on the one above is specifically designed to be for a ladder audio attenuator, so I assume it's really just plug-and-solder sort of a deal... Should be a little easier to put together.


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## Voodoochile

The switch I used was purpose-built for a ladder attenuator by Elma. Even the shorting contacts are a different bounceless design than their normal shorting contact, to avoid any bounce-induced clicking while turning. Also, there is an extra wiperless deck that serves as the common ground between the two channels, between the in and out decks for both channels.

 From left to right, the decks are like this:
 Left in, left out, left & right signal ground, right out, right in. In the picture linked above, you can see four decks with wipers and one in the center without. That extra deck actually made assembly easier, I thought, keeping you limited to one layer of resistors. I see the common ground ring on your PCB deck, which is cool, but the thought of threading those resistors into that narrow space in two layers makes me a little buggy. My hands and fingers are just too big I guess!

 As for assembly time, I mainly depends on how fastidious you are with parts matching, sorting, getting organized, lead forming as needed... the actual soldering is maybe a couple hours. I would select the part, make sure it was the proper value, confirm the location, the reconfirm everything 
	

	
	
		
		

		
		
	


	




.
 I wanted to be darn sure I was not desoldering and swapping any of these Holcos after assembly.


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## doobooloo

Ah - I apologize! I didn't know that yours was specifically designed to be an audio attenuator. 
	

	
	
		
		

		
		
	


	




 Anyhow, how easy is it to take the decks apart? The thing is, I'm wondering how I can get the resistors in place on the PCB design if I can't somehow take the thing apart...


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## Voodoochile

I don't know if it is easily disassembled or if it assembled with the idea that it will not be taken apart again. I would probably make a big difference in assembly time. Then again, pre-inserting all the resistors, then trying to get them all to align with the holes in the next deck might be trouble, too.

 Perhaps sliding the end (the end away from the knob) further into the rear deck to clear the front lead end, then swinging the resistor into place and sliding it back towards the knob end to insert the forward lead into the forward deck would work. Careful pre-trimming of the leads needed, but ought to go pretty well. Certainly the outer layer would go well.


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## Super-Gonzo

Quote:


 _Originally posted by doobooloo _
*In the meanwhile, BrianGT of diyAudio is organizing a group buy on the Series R Elma ladder attenuator - and he says the entire attenuator will cost less than $90 with resistors!... * 
 

I signed up for one of these switches as well. Too bad the resistor kit he's making isn't 50k... it would be nice to not have to go to the trouble of ordering the resistors myself.


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## JohnFerrier

FWIW: Elma switches are not make before break (as someone previously indicated) and can make a slight clicking sound between positions. Make before break would be kind of odd anyway as the impedance would be changing up and down. Regardless, nothing annoying with the Elma switches.


 JF


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