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Jeffrey D. Medwin

Autoformer Volume Control

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P1010040  EDITED INPUT 1B.jpg

 

Regarding your bottom note, ONE STRAND of that wire would (should) be way more than sufficient for the task at hand!  Even then, the silver wash on the copper will undoubtedly not comprise enough of the signal skin depth at audio frequencies to appreciably use the better conductance of silver vs. copper to allow for nearer-to-light-speed flow (5%?) of the electrons.

 

Mostly I'm jealous of your ability to use "retired time" for this sort of shenanigans.  I've not devoted enough effort to provide for such - I'll have to work 'til the day I die.

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Silver plated contact switches will SOUND better than gold plated at line level signal levels? Not after a year of corrosion. Silver plating is used in POWER swicthes for better (higher) current capacities. The arcing at power off tends to keep the silver surfaces clean.

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1 hour ago, glens said:

P1010040  EDITED INPUT 1B.jpg

 

Regarding your bottom note, ONE STRAND of that wire would (should) be way more than sufficient for the task at hand!  Even then, the silver wash on the copper will undoubtedly not comprise enough of the signal skin depth at audio frequencies to appreciably use the better conductance of silver vs. copper to allow for nearer-to-light-speed flow (5%?) of the electrons.

 

Mostly I'm jealous of your ability to use "retired time" for this sort of shenanigans.  I've not devoted enough effort to provide for such - I'll have to work 'til the day I die.

 

 

Please tell us, how do YOU know how much wire is necessary , to play back audio information and be faithful to the music, and be able to comment on it, and tell us what is needed as you do??  

 

With this Mil Spec wire,  over the last five years, 16 AWG has been a decent compromise, between retaining the highs, doing the lows AND having the  dynamic expression on music play back. 14 AWG is not bad either.

 

" Retired time ", not quite.  Today is just my day off.   I am 75, need to work, and intend to  ( hope to ) do so for another seven more years.  I take time with audio because its important - to me.

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2 minutes ago, babadono said:

Silver plated contact switches will SOUND better than gold plated at line level signal levels? Not after a year of corrosion. Silver plating is used in POWER swicthes for better (higher) current capacities. The arcing at power off tends to keep the silver surfaces clean.

 

 

You are correct .................in as far as you went.   

 

I am not merely suggesting plated switches sir. 

 

The plating occurs in the less costly  71 Series switches, plated with nickle, silver and gold, as per their datasheet.  

 

These 44 Series switches are all silver switches, described in the datasheets, not as plated,  but rather as a silver alloy. 

 

Additionally, I get supporting confirmation, ' have two very experienced and trust-worthy high-end audio Manufacturers who vouch for these the Shallco and Grayhill 44 Series silver switches.  

 

Thanks for posting !

 

Jeff

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1 hour ago, Jeffrey D. Medwin said:

Please tell us, how do YOU know how much wire is necessary , to play back audio information and be faithful to the music, and be able to comment on it, and tell us what is needed as you do??  

 

How do I know?  How do YOU know?  You habitually declare things which have no basis whatsoever on scientifically-provable phenomena.

 

I contend that so long as the conductor does not become warmer than ambient temperature, it is sufficient for carrying the current, yes, even with signals within the full audible spectrum.  It will not become confused as to what to do with nor how to handle low-bass or high-treble signals, or anything in-between, simultaneously and in any mixture.

 

You continually report finding solutions to problems which don't exist on this planet at this time.  It's mildly entertaining, to a point. 

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On 1/6/2020 at 6:30 PM, glens said:

 

How do I know?  How do YOU know?  You habitually declare things which have no basis whatsoever on scientifically-provable phenomena.

 

I contend that so long as the conductor does not become warmer than ambient temperature, it is sufficient for carrying the current, yes, even with signals within the full audible spectrum.  It will not become confused as to what to do with nor how to handle low-bass or high-treble signals, or anything in-between, simultaneously and in any mixture.

 

You continually report finding solutions to problems which don't exist on this planet at this time.  It's mildly entertaining, to a point. 

 

 

Respectfully, I find your comment above quite amusing. 

 

I don't care much about the science, or need any proof, just the result.  Whats important to judge : temperature rise OR............. how does it sound?   " Don't tell me about the pregnancy, just show me the baby ".

 

Thanks for posting Glens, have fun with my posts if amusing, and -  its very nice to meet you.

 

Jeff 

 

PS :

 

Remember my first Audio Mentor's commentary   " Scientists don't pursue the truth, it pursues them. "  ............1978 .......................R.W. Fulton

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  This is the Greyhill rotary switch I started using. Eleven decks and 12 positions. Paralleled five decks for each channel and grounded every other position to reduce crosstalk from capacitive coupling. 

  Got a couple installed and wired. Will look for one. Do not know contact metallurgy. or other details. But with five contacts connected in parallel it may not matter. 

  Ace Electronics had a pile of these at 20.00 a pop 10 or so years ago.

40FC3F73-3F80-4264-BAAE-05B87CC261CE.jpeg

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Greyhill 81073, to make a 3 position, stereo source selector utilizing all 132 contacts.

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Why would you just use a resistor ladder attenuator...

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13 hours ago, Schu said:

Why would you just use a resistor ladder attenuator...

 

They use a switch to select each tap off the autoformers. The autoformer does the attenuation, the switch selects the taps.

 

Unless you mean just using a stepped attenuator over an autoformer.

 

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On 1/6/2020 at 10:16 PM, Panelhead said:

Greyhill 81073, to make a 3 position, stereo source selector utilizing all 132 contacts.

 

 

Thanks for posting !!  I personally would be hesitant to use that as it appears to be a 71 Series Grayhill.  I would only consider a Grayhill rotary with silver alloy contacts, for low level audio signal use, and also - only a shorting type of switch ( MBB or make-before-break ).  Their silver alloy models are Series 42, 43, 44 and 54 .  I've located some to do what you want, surplus priced.   P.M. me and I will be glad to refer you to them, under $30.00 with shipping as I recall.

 

Jeffrey Medwin

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On 1/7/2020 at 12:02 PM, mike stehr said:

 

They use a switch to select each tap off the autoformers. The autoformer does the attenuation, the switch selects the taps.

 

Unless you mean just using a stepped attenuator over an autoformer.

 

post-6643-13819690681798_thumb.jpg

 

 

Mike, 

 

I enjoyed seeing that photo / DIY execution.  I feel Dave's Autoformer, being in the front-end of the system, deserves to be housed and executed much much  better than that we are seeing in our posted photo.

 

Consider this, it resides at the beginning of the system, and ANY losses of fidelity,  that a DIY execution imparts, will be passed on the the rest of the system, and losses will never be made up at the speaker end !!  

 

Lets discuss a more ideal way to execute that autoformer, what I would want to do, if keeping it long term, for my own use  :

 

First of all, a single pair of RCA jacks in and out, as shown, is too limited, to only one source.  This autoformer ( or any good resistive-ladder passive attenuator ) can eliminate the use of a Line Stage, in most perfectionist systems.  So, a good passive Attenuator should do multiple Source - Switching as part of it's design.  I would think, to give an Attenuator a minimum of three sources, one phono and two line inputs.

 

The two best switches, sonically, I know of would be either the Shallco 10 A. silver switches from Michael Percy, or the Grayhill silver alloy contact switches,...... Grayhill Series 42, 43, 44 and 54 - shorting types only ( MBB , make before break ) .  Anything else would likely be second best, and a degrade.   This Attenuator will require more than one switch one switch to pick taps on Dave's autoformers, and another switch to select sources.

 

If I were building this for myself, long term use, I'd want the best RCA jacks.  I would use Vampire RCAs, their top -of-the line directly gold plated pairs.  CM2F/CB, also from Michael Percy, at $33.95 a pair.

 

I would likely not use the press-to-connect clips we see in the photo, on each Autoformer tap, bit rather,  ' would carefully solder directly to each of the 24 taps.

 

Realize, since source signal levels are among the lower signal levels in the audio chain, I would only use the very best hook-up wire available, to build this.   

 

In my thinking, there is only two hook up wire choices to employ, both are pure silver.   Cost is about $2.00 an inch.   One choice would be Kimber Kable's lovely  AGss.  An alternative, would be DH Lab's Silver Sonic 18 AWG pure silver hook up wire.  None of these individual hook-up wires should touch each other, and of course, twisting polarities is a No-No !!

 

All my suggestions are just my opinion.  Doing all of the above, no shortcuts, would be the best execution I am aware of, to get the most out of the basic Slagle Autoformer. Who in this world will proceed and do all of this first  ???

 

Jeffrey Medwin

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On 1/6/2020 at 11:15 PM, Panelhead said:

Paralleled five decks for each channel and grounded every other position to reduce crosstalk from capacitive coupling.

 

Ooh, better make sure your parallel wires are matched in length at the micron level or you could wind up with a degradation!  Hahaha! 

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2 hours ago, glens said:

 

Ooh, better make sure your parallel wires are matched in length at the micron level or you could wind up with a degradation!  Hahaha! 

 

 

Why not!  Micron level is not possible.  3.5 inches all, or  even 1.75 inches all, if they would reach and its do-able.

 

Jeff 

 

                  568402491_EinsteinQuote.JPG.f84eb94f8897da9c201cb89e2c1ce80c.JPG

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12 hours ago, Jeffrey D. Medwin said:

Doing all of the above, no shortcuts

 

The shortest cut would be to pick the favorite tap, and just use it. Who needs attenuation...

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On 1/9/2020 at 11:28 AM, mike stehr said:

 

The shortest cut would be to pick the favorite tap, and just use it. Who needs attenuation...

 

 

Personally, in my system, for L.P. playback,  I like having very precise control over volume levels, and balance. 

 

This precision control is only obtainable with a potentiometer, but its got to be done as a very very well thought-out implementation, using top-quality parts. 

 

That is my next DIY build effort, to rebuild my Resitive Attenuator, with better parts and a more flexible switching capability, and likely add phase-reversal of sources.   I hate to switch speaker leads at the amp, to hear out-of-absolute-phase recordings properly played back in my listening room.

 

My 1978 Fulton dual-mono Bravura preamp, in addition to a normal volume control,  also has a FIXED output of phono, with new RCA jacks installed.   FIXED out totally bypasses the Allen Bradley Mod Pot balance and volume controls taken from the output of this unit.  I want to hear that - next.  Take the phono signal,  " FIXED out " -  no internal-unit attenuation, into a rebuilt highest-quality external Resistive Attenuator.   

 

This Bravura phono unit used a nicely-designed P.C. board, with large ground areas, and wide traces.  One of the many things Mr. Fulton did back them, was to HEAVILY modify the board's traces, with real wire.  Can you see all the green - colored wire he added in parallel to the board's traces ??  Wonderful transfer efficiency, and this unit, using a directly coupled passive RIAA,  very nicely performs !!

 

 

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