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Jeffrey D. Medwin

Autoformer Volume Control

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Funny that he doesn't seem to "get it" in that thread.  The best graph shown he has a "yuck" noted about it.

 

BTW, 7.14 does not equal 7-1/16.

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13 hours ago, Jeffrey D. Medwin said:

 

Has anyone besides SET 12, years ago, done A-B comparisons?  His was VS: German Autoformers. 

Regards, 

 

Jeff Medwin

The crossovers in Set 12's fortes were parted out and sold on ebay

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11 hours ago, glens said:

Funny that he doesn't seem to "get it" in that thread.  The best graph shown he has a "yuck" noted about it.

 

 

No, he doesn't.

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2 hours ago, Skelt said:

The crossovers in Set 12's fortes were parted out and sold on ebay

 

  Cool.  Do we know what he went to, and uses now ?

 

  Maybe he improved upon the German ones, and since life is short, elected to use something he finds as better ?

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20 hours ago, Jeffrey D. Medwin said:

 

So Cool !!

 

Looks like you and I own the same Intact Audio double-switch modules

 

Have you ever A-Bed , say a Crites 3636 VS a Slagle , as, say, a Line Attenuator ?? 

 

Have you ever thought to augment the module's  PC traces, between the two switches ??

 

I wouldn't bother to use a Slagle product for a crites 3636 or whatever klipsch used. The klipsch and crites are fine for the application.

 

I use Slagle AVCs as pasive preamps or attentuation for amplifiers, preamplifiers and the likes.

 

The modules and traces are fine. I see no problem with them. I've wired them myself without the traces on earlier versions. They all work great.

 

I plan on building another amp with all Slagle interstage transformers, nickle chokes, and his top of the line outputs. Gonna be fun.

 

 

 

 

 

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7 hours ago, seti said:

 

I wouldn't bother to use a Slagle product for a crites 3636 or whatever klipsch used. The klipsch and crites are fine for the application.

 

I use Slagle AVCs as pasive preamps or attentuation for amplifiers, preamplifiers and the likes.

 

The modules and traces are fine. I see no problem with them. I've wired them myself without the traces on earlier versions. They all work great.

 

I plan on building another amp with all Slagle interstage transformers, nickle chokes, and his top of the line outputs. Gonna be fun.

 

 

 

 

 

 

That sounds cool.  I am not surprised at your report and opinion on the PC Board traces of our Intact Audio attenuator modules.  Enjoy your build

 

But what works for you, Dave, and many others, may not work for my builds. 

 

My DIY SE KT88 amp, built in 2019, uses a low DCR power supply, and special wiring, no one else has ever used.   Think of this TOTAL combination  seti :

 

multiple 6 Ohm DCR power supply chokes,

two, not one  5U4GB rectifier,

8 AWG Mil Spec ground and buss wires,

GTO caps to the Finals tube, 1,500 Ampere instantaneous-peak-capable

double shunt B+ regulation to the front end 

Final ( L/C ) Filters to the Input tube, and Final ( L/C ) Filters to G2, with zero lead lengths

an all-silver ( Cardas 19 AWG, polished, multiple parallel runs ) audio path.   

 

Every magnetic component has had its leads replaced by me, and mil spec wire-optimized, to do peak current pulses and also maintain wide bandwidth.  As a result of ALL of the above, in combination with each other,  this SE KT88 DC amp now has the best signal resolution, AND very best dynamic differentiation capability, of any tube amp I have ever heard - in all of my own audio listening. 

 

So seti, those thin PC traces between those adjustment switches, for a Volume control feeding this amp, will likely be an "issue" for me, in my system, to improve upon.  I did augment mine, easily,  ............. and in less than two hour's time.   

 

A thin PC trace is never the equal to real wire - wire that is optimally selected for the task.  A thin PC trace has never been superior, nor will it ever be.

 

Mr. Robert W. Fulton, my first audio Mentor ( 1978-88  ) used to always tell me " an inch of bad wire can ruin the musical experience".  He was correct. 

 

Its a whole lot of fun, and rewarding when completed, to design and build high performance  DIY SE tube amps , with all of this kept in mind.  Thought and effort, equals results.  Amps are the weak link, the real turkeys in my opinion and experience.   Amps are where the biggest performance gains can be had, not speakers, most speakers are WAY better than the amps used on them.  Have fun seti, I sure do.

 

Jeffrey Medwin

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24 minutes ago, Jeffrey D. Medwin said:

 

That sound cool.  I am not surprised at your report and opinion on the PC Board traces of our Intact Audio attenuator modules.  Enjoy your build

 

But what works for you, Dave, and many others, may not work for my builds. 

 

My DIY SET KT88 amp, built in 2019, uses a low DCR power supply, and special wiring, no one else has ever used.   Think of this TOTAL combination  seti :

 

multiple 6 Ohm DCR power supply chokes,

two, not one  5U4GB rectifier,

8 AWG Mil Spec ground and buss wires,

GTO caps to the Finals tube, 1,500 Ampere peak capable

double shunt B+ regulation to the front end 

Final ( L/C ) Filters to the Input tube, and Final ( L/C ) Filters to G2, with zero lead lengths

an all-silver ( Cardas 19 AWG, polished, multiple parallel runs ) audio path.   

 

Every magnetic component has had its leads replaced by me, and mil spec wire-optimized, to do peak current pulses and also maintain wide bandwidth.  As a result of ALL of the above, in combination with each other,  this SE KT88 amp now has the best signal resolution, AND very best dynamic differentiation capability, of any tube amp I have ever heard - in all of my own audio listening. 

 

So seti, those thin PC traces between those adjustment switches, for a Volume control feeding this amp, will likely be an "issue" for me, in my system, to improve upon.  I did, easily,  ............. and in less than two hour's time.   

 

A thin PC trace is never the equal to real wire - wire that is optimally selected for the task.  A thin PC trace has never been superior, nor will it ever be.

 

Mr. Robert W. Fulton, my first audio Mentor ( 1978-88  ) used to always tell me " an inch of bad wire can ruin the musical experience".  He was correct. 

 

Its a whole lot of fun, and rewarding when completed, to design and build high performance  DIY SE tube amps , with all of this kept in mind.  Thought and effort, equals results.  Amps are the weak link, the real turkeys in my opinion and experience.   Amps are where the biggest performance gains can be had, not speakers, most speakers are WAY better than the amps used on them.  Have fun seti, I sure do.

 

Jeffrey Medwin

 

 

I respectfully disagree on the pc traces and wire stuff. That is why its called do it yourself lol.... Have fun.

 

 

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11 minutes ago, seti said:

 

 

I respectfully disagree on the pc traces and wire stuff. That is why its called do it yourself lol.... Have fun.

 

 

 

I appreciate fully, and respect your thoughtful, kind response .    No problem.   Its a shame you were not local to me, or vice versa, so we could A-B and learn from each other. Also, very few people ( 4 so far ) have ever heard what I described above !

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There is no doubt whatsoever about the differences in the conductivity of metals and their effect on current flow. Many PCB board traces are made of tin, or if you're lucky copper. Silver is more conductive than both, so in theory, beefing up PCB board traces with silver plated wire will increase conductivity. I have been beefing up the thin, tin traces on my Dynaco ST-70 Series ii with silver plated copper wire and I feel like the quality of the bass has improved along with cleaner highs and even an improved soundstage (These tin traces are a weakness of this amp). It's a subtle improvement, but the mod is cheap and easy to do and can certainly do no harm. I am focusing on traces in the signal path at first. You can't argue with the improved conductivity and lowered resistivity of silver.

 

Thanks for the great advice Jeffery!

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On 12/27/2019 at 12:31 AM, MechEngVic said:

There is no doubt whatsoever about the differences in the conductivity of metals and their effect on current flow. Many PCB board traces are made of tin, or if you're lucky copper. Silver is more conductive than both, so in theory, beefing up PCB board traces with silver plated wire will increase conductivity. I have been beefing up the thin, tin traces on my Dynaco ST-70 Series ii with silver plated copper wire and I feel like the quality of the bass has improved along with cleaner highs and even an improved soundstage (These tin traces are a weakness of this amp). It's a subtle improvement, but the mod is cheap and easy to do and can certainly do no harm. I am focusing on traces in the signal path at first. You can't argue with the improved conductivity and lowered resistivity of silver.

 

Thanks for the great advice Jeffery!

 

 

Thanks for describing for others, what you heard.  'Am very happy that you are pleased.

 

On the two Intact Audio boards, which retail for $350 a pair, I applied less than 25 cents worth of this special wire !!!!

 

For the record, it is m22759/11 wire ...multi stranded copper, silver plated, teflon jacketed, Military Spec wire.  I strip off the teflon jacket, and 18 AWG ( 26 cents a foot ! surplus priced ) seems ideal for the thin PC board traces.  I used 16 AWG, from the board to the RCA jacks.  AWG-wise, use of 16 and 14 AWG will MAINTAIN the highs, AND the bass information nicely, for LINE level signals with m22759/11.  Dennis Fraker, my Mentor,  taught me this.

 

Easiest low priced, reliable-to-deal-with wire source is Steve Slater at Apex Jr. Surplus,  in Torrance, CA, and on line.  See :

 

                                                           1514581324_ApexJr..JPG.5a935af55e5b885a5c1dc5e386fff733.JPG

 

 

In 2019, the most cost effective, highest performing speaker wire ( I have ever heard  ) is a paralleled trio of 12+12+14 AWG of m22759/11, in Robert W. Fulton multiples of 57 1/8th inches.  Two multiples, at 9.52 feet each, are my favorite speaker length.  Lightly twist each polarity or wire-trio, but be SURE that the polarities do not touch each other, amp to crossover -  crossover to drivers, as its an audible sonic degrade.  A wire with some  silver content is needed, if you wanna hear more than just midrange playback.

 

" Scientists don't pursue the truth, it pursues them ".  RWF  1978

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Mr. Robert W. Fulton, my first audio Mentor ( 1978-88  ) used to always tell me " an inch of bad wire can ruin the musical experience".  He was correct. 


Did he have any opinion about cold solder joints? What about the wire in component leads?

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On 12/27/2019 at 10:40 PM, codewritinfool said:

 


Did he have any opinion about cold solder joints? What about the wire in component leads?

 

 

Good questions !!

 

Mr. Fulton sadly died from Cancer in 1988, so he was unable to critique what you are addressing in 2019.  He wouldn't approve of cold solder joints.  Look at the Autoformer photos posted at the beginning of this thread, and ponder the most recent soldering , if you will.  It looks OK - enough to me.

 

Component leads ???   

 

I am probably the only person on this Forum, who will thoughtfully replace component leads, adding m22759/11 Mil Spec wire, on almost every magnetic component, to maintain transfer-efficiency through the amp.  This Forum's mid-year 2019 KT88 build thread .............show many detailed photos / examples of this !!

 

My DIY amps, ( and my mentor's manufactured amps ), are designed for maximum dynamic contrasting, of the original recorded event, to be displayed by the high efficiency speaker.  No one else I AM AWARE OF, except us two individuals, designs specifically for maximum dynamic contrasting. 

 

To obtain maximum possible dynamic contrasting, ( the ability of the amp to faithfully play back accurately fast repeated PULSES ), requires that ALL the wiring inside the amp, be optimized, and this, codewritinfool, means each and every lead in the circuit needs to be scrutinized, for high transfer efficiency, for pulse performance.

 

There are two performance areas that effect our perceived playback of a good audio amp :

 

The first is music signal resolution, playing back the minute details of the recorded event, without any smearing, or missing any of it, in proper time ( zero feedback ) and - with proper timbre accuracy.  What comes to mind, word-wise, and loosely,  is what William Z. Johnson of Audio Research Corporation used to term " High Definition ",...... that verbiage.

 

The second performance area of a tube amp, unrecognized and seldom addressed , I like to call " High Dynamic Resolution ".  No one, except my mentor and I, design specifically for this.  Dynamic resolution occurs partially, in all other tube amps,  only as a byproduct of the designer's general circuit execution.

 

High Dynamic Resolution comes about as a result of careful attention to the amp's power supply, ( much more so than what almost everyone else now does ) , and proper wiring techniques, internally.  This allows for the best signal transfer efficiency, especially under pulsed conditions.

 

Inside amps, I have soldered  bare 14 AWG ( m22759/11 14) across 3/4 inch long looped leads of a Mills MRA-12 resistor, series-feeding a driver / input tube, ( running at only 1 mA. ), to good-effect aurally, dynamic-response-wise.  An E.E. trained person, alas, would NEVER think to do that.  They'd tell us all " its impossible."

 

Yes, most DIY builders and almost all the tube amp Manufacturers, are totally unaware, .....to design this way.

 

How come?  Why ?  First of all, they have too-high DCRs in their tube amps.  Secondly, they use unconscious wire executions, which will not allow them to hear this.  So, combining these two very negative design factors,  they never have a chance to obtain the performance benefits of high signal resolution, .........AND .................... high dynamic resolution.

 

From my listening tests in Montana, this year, I should inform you all, my 2019 SE KT88 amp, is the first tube audio amp I have ever heard, that does both high signal resolution, AND highest dynamic resolution.   Such unique performance did not exist, in my listening experience, with any tube amplifier, prior to that KT88 2019 DIY build - which I did under my mentor's guidance and urging.

 

Recall the  2019 KT88 amp thread  codewritinfool ?   

 

https://community.klipsch.com/index.php?/topic/182623-kt88-direct-coupled-design/

 

 

I personally selected and used a 8 AWG Mil Spec ground buss ( coming out of the Power Transformer's high voltage center tap ) , and ..... several 8 AWG Mil Spec ground returns .   This is the first tube amp ever in audio, that I am aware of,  so designed .  It was clearly audible to us all assembled, when I schlepped that prototype amp to Montana. 

 

A 8 AWG m22759/11 ground buss, codewritinfool,..... IS...... a component lead.

 

Now you all finally have the truth from that Montana visit, as we all heard it - when using high resolution source material !!   The KT88 amp was fantastic to experience - none of us ever heard any amp DO this before : High Signal Resolution combined with ...... High Dynamic Resolution.

 

Yes, I re-do component leads extensively - thoughtfully.  Learned to do so from both my mentors, my teachers ( Fulton and Fraker ).

 

How can I explain this , so its understood, to my very nice friend Maynard, who only asks to see a square wave?

  • Confused 1

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Jeffrey, there is really nothing to explain.  All I ask is that you show me the square waves at the frequencies that I requested and your calculations of the amp’s output impedance.  
 

 

Maynard

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A New Year's Evening UPDATE :

 

My KT88 prototype amp, with a mu ( gain ) of 100 front end tube ( 1/2 of a 12BZ7 )  has too much gain, through the entire amp.  I have all the parts on hand, and in Q1 sometime, I will install a mu ( gain ) of 20 6FQ7 triode, instead, in that front end tube spot.   A 6FQ7 is my audio mentor's suggestion, I did the math, schematic changes, and simulations, and will execute it

 

     863569131_6FQ7FINALat5mA.edited.thumb.jpg.62943408563f3ac44f4f9695c18f178d.jpg

   

 

 

 

Just got the KT88 amp back home, after three months sojourn at the Kansas City 1911 horse-drawn Firehouse.   Been listening to the amp for four hours, its very satisfying.  

 

                                         585078075_Randys1911Horse-Drawn-FirehouuseHome.JPG.b0a9f851ec916580e3a8850ab5dd8404.JPG

 

 

Well, I A-Bed the Resistive Ladder Attenuator ( 10K wirewound Bourns precision multi-turn pots ) , VS the new Autoformer Attenuator shown in the first post of this thread.

 

It wasn't a fair A-B, the amp has too much excess gain, with the 12BZ7, .......such that I could not turn the Resistive Attenuator up more than 3 to 5 percent from full-off, to get a nice listening level.    This is the worst way to use a resistive volume control.  6FQ7 needed !!

 

Well, with an Autoformer Attenuator,  (as you can see from the simulations earlier in this thread ), large attenuation is NO problem, and is actually an advantage.

 

So, on a quick initial A-B, the Autoformer Volume control totally ATE my Resistive 10K Ladder Attenuator.   The Autoformer maintains DYNAMICS when you turn it down low !! My amp and system DOES dynamics especially well, so it was easy for anyone to hear.

 

I got to wondering, the Resistive Pot Attenuator had Vampire RCAs, and the Autoformer was using those lowest cost Radio Shack RCA jacks.  What would happen, if I put a couple of Vampire jacks in place of the Radio Shack RCAs??  Well, I did that,  an hour ago, and have been VERY surprised, and impressed with the fidelity improvement.  My goodness !!  Listening to Dave Grusin, and the solder joints in the Autoformer, and the KT88 amp, is breaking in and warming up.   This sure is fun.

 

Happy New Year.  I'm pleased .  When the 6FQ7 gets installed, I will do Attenuators A-Bing  again, and report the results.

 

Jeffrey Medwin

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57 minutes ago, Jeffrey D. Medwin said:

Listening to Dave Grusin, and the solder joints in the Autoformer, and the KT88 amp, is breaking in and warming up.

Jeffrey,

  You're listening to solder joints?  You're listening to solder joints warming up?  I'm trying to understand what this sentence is saying.

Happy New Year

code

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14 minutes ago, codewritinfool said:

  You're listening to solder joints?  You're listening to solder joints warming up?  I'm trying to understand what this sentence is saying.

 

mad_scientist.gif&f=1&nofb=1

 

giphy.gif&f=1&nofb=1

 

I_dunno.0.gif&f=1&nofb=1

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1 hour ago, codewritinfool said:

Jeffrey,

  You're listening to solder joints?  You're listening to solder joints warming up?  I'm trying to understand what this sentence is saying.

Happy New Year

code

 

Yes, of course, everything has to break in .  When you plug and unplug an RCA jack, on a transparent system, that takes a while, hours, to settle-in !!   Didn't you know that ? 

 

Actually, I was thinking precisely of you in the last hour as I have been listening. You need to take a train from St. Louis to my home town.  The station is 3 blocks from my home.  You need to HEAR this new amp, and this Autoformer Volume control, playing these A7-8 two-way speakers.   Then and only then, would you understand and appreciate what is occurring.  You are invited, and if you don't mind sleeping on a large leather couch, you can stay overnight for free, take a train back the next day.   Its four hours, a bit over 200 miles, and $32.00 fare each way.  I know how to scramble eggs for breakfast, but that is all I can cook !! 

 

Jeffrey Medwin

 

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Yes, of course, everything has to break in .  When you plug and unplug an RCA jack, on a transparent system, that takes a while, hours, to settle-in !!   Didn't you know that ? 


Well, I’ve heard people say that, but I”m not sure I believe it.



Actually, I was thinking precisely of you in the last hour as I have been listening. You need to take a train from St. Louis to my home town.  The station is 3 blocks from my home.  You need to HEAR this new amp, and this Autoformer Volume control, playing these A7-8 two-way speakers.   Then and only then, would you understand and appreciate what is occurring.  You are invited, and if you don't mind sleeping on a large leather couch, you can stay overnight for free, take a train back the next day.   Its four hours, a bit over 200 miles, and $32.00 fare each way.  I know how to scramble eggs for breakfast, but that is all I can cook !! 
 
Jeffrey Medwin
 


Very kind of you, thank you.
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