Another idea for volume control on the FP III+

J

jrebman

New member
As I generally don't like dual volume controls (and believe me, this comes from a whole lot of experience with all kinds, including stepped) I've been looking through the posts here and have not really seen anything other than a custom dual attenuator based on the original 15k pot -- which seems fine, though the variable loading of the source seems to be a concern (although only a theoretical one at the moment and may not be anything at all to be worried about.)

However, I wonder about a stepped system that uses two 6-position rotary switches for a total of 36 steps -- one coarse and one fine) and wonder if anybody has done this and what type of attenuator you built -- series, ladder, or hybrid?

This seems like it could be a somewhat more economical way to a high quality attenuator for the FP III.

Thoughts?

-- Jim
 
Jim,
I'm in the midst of defining a path for  improving the volume controls in my EFP3. I'm curious why you find dual mono controls a detriment? I'm currently using a Goldpoint selector with sweetest whispers shunt attenuators. The padding resistors are  Audio Note and Shinkoh Tantalum's. I'm trying to explore the audible effects of several different types of resistors. I've not begun testing yet as my speakers remain unfinished. If you please, I would like to know more about resistors you have used and your evaluation of their sonic effect. Would you agree that any, high quality passive volume control is essentially 90% due to the resistors used? I also would like to build an economical high quality volume control as I think this is an area where real sonic improvements can be achieved. I will continue reading with interest.
Thanks,
John
 
Funny you mention that. PB just bought the parts to build a coarse/fine stereo attenuator as a test for the 300B preamp.
 
Wow, that is exactly what I was wondering about! The idea came from the days when I owned a tuner that has fine and coarse tuning. This would be the same idea. Like I have said before, there is an EXACT volume that I am trying to reach in some recordings.
 
How about something like this,

http://glass-ware.stores.yahoo.net/netcjstat.html

I have one in one of my projects, works pretty well...John
 
John R. -- really just me and my preferences -- far easier to turn one knob than it is to count clicks on two stepped attenuators, and two linear pots always ends up with me going back and forth to the listening chair typically several times before I get it right, then when the mix strays to one side I feel as if I should get up and tweak it -- none of these is really conducive to deep listening IMO.  I'd much rather set it and forget it.

Yes, the resistor, and even the solder play a significant role in the sonics.  I've not tried all the ones out there certainly, and as well none of the real boutique ones in a stepped attenuaator, but inddividually the vishay rn-55 is a good all-around metal film resistor, the CMF-55 a step up, and then the Texas components (nude vishay's) but you can also use the super expensive tantalums, nudes, and others in more critical places -- such as shunt and padding resistors in the foreplay and probably take the whole thing up a notch.  Night and day difference?  Doubt it, but noticeable for sure and worth it is strictly up to the individual.  My main complaint with the smd resistors is that typically the resistive element is nichrome and I just don't think nickel or chromium sounds very good in an electrical circuit.

Dan, great -- perhaps PJ will tell us more when he gets back.

John, I'll have to look again, but I recall the tubecad attenuator being a bit too large for the BH chassis, and at least for me with my new rack, widening the BH chassis is not an option.  But yes, that's the idea that got me thinking about a similar approach for the FP III.

-- Jim
 
John, that ad really knock me over! Soooo, it's not just me. Now, if I could just verify the quality of this product. This is EXACTLY what I would want,  in theory. Thanks for the post.
 
Greg,

the TCJ hardware is of top quality -- very substantial pcboards and he only uses the swiss made, hard gold contact, Elma rotary switches, plus you always have the option of buying your own resistors if you don't like his options.

-- Jim
 
I finally found the reference to using "boutique" resistors in the most used positions, VoltSecond!  

So build and find which positions are used most.  Then, after listening for a while, you have determined where you listen most often.  At that point you can put a $17 Nude Vishay in the series position and a $6 boutique in the shunt to ground positions.  

This appeals to the cheapskate in me.
 
Hey Grainger,
There's some cheapskate in all DIY, right? Besides we are value conscience....  Of course I usually don't get it right the first several times but that's another story!
John
 
Jim R. said:
Greg,

the TCJ hardware is of top quality -- very substantial pcboards and he only uses the swiss made, hard gold contact, Elma rotary switches, plus you always have the option of buying your own resistors if you don't like his options.

-- Jim
Click to expand...
The ELMA switchs at parts conneXion are $60 each, and the TCJ kit with three switches is $30. I think I'm missing something!
 
Oops, does indeed look like he has changed switches:

"The kit includes instructions and three high-quality, open-frame, rotary switches... "

Those are definitely not the sealed, hard gold Elmas he used to sell with the kit -- which also used to be something like $170. Ah, looks like he still offers that kit too, but at $160:

http://glass-ware.stores.yahoo.net/tcj-stepped-attenuator.html

Also, the A5 kit (possibly subbing elma 6 position switches) looks like it may be just the ticket for the FP III -- and it will fit, but probably not in the stock top plate.  Might even work as-is as far as the configuration too:

http://glass-ware.stores.yahoo.net/a5stat.html



-- Jim
 
Now, I did dig a little further to find he offered another kit for $160,  probably the one you remember. It was obviously 'hi-fi' as the bodies of the switches looked exactly like the Elna(I'm sure that they were because they were out of stock, waiting for more switch bodies from Switzerland:). Anyway, you know where this is headed, with me talking all about the exact volume,etc.  Time to start deigning a switchbox with a volume control(passive preamp?)
 
I just found that Khozmo makes a shunt-type attenuator -- would this work suitably well in the FP III+ and would the recommendation be for 25 or 50 k and would you still put the 33k resistor under it?  Or, would it be better to get a custom 15k or 20k version from them and wire as described in the manual?

I'm not worried about the fit as I'm machining new top plates for my fp III, eros, and SR-45s out of copper plates.

Thanks,

Jim
 
To try all this stuff out for 'comfort', a Quckie kit has been ordered with the optional upgrade. Along with that thinking, I believe that I will try the cheaper ($30) volume control first. If this all works as I think it should, who knows what will happen next? (Not even my entire team of psychiatrists are willing to bet on that one)
 
Greg,

Just for yucks try the 100k Alps Stereo Volume control from Radio Shack first.  It costs over $3 now, damn near $4, it used to be $2. 

http://www.radioshack.com/product/index.jsp?productId=2062359

Many say that the low level tracking is off but I have used them for over 20 years with no problems.

I mean, if you are going to do a survey of this stuff, start at the bottom.
 
I still have one of those Alps pots on a half kit I built.  I bought a Blue Velvet to replace it but never got around to it.   Mine actually tracks fairly well but listening level on that amp is usually 11 O'clock or higher.   Actually I think those little S5 kits had/have a version of the same control.   I have one of the older/original S5 kits with the 11BM8 tubes that sounds better than any amp under 100 bucks has any right to.  A pair of full rangers with Fostex drivers crank on that little amp.  That little kit with it's cheap transformers, run of the mill PCB and cheap passives along with an old Scott 299B is what started me back with tube audio gear a dozen years ago.  Those cheap wirewound Alps pots sound fine to my ears but with 2 disclaimers.  First, I havent compared them to anything else in those amps.  And second, MY EARS being the operative words.  They probably arent quite tin but they are closer to tin than gold   ;D
 
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