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Jeffrey D. Medwin

KT88 Direct-Coupled Design

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Posted (edited)
On 6/2/2019 at 11:23 AM, Schu said:

I bet the Underwriters Laboratory would love to get a peek at the under hood nest...

Well to be fair, I think the Serious Stereo amps are at least safely built. He seems to know basic electrical construction. It's only Jeff who believes in that fuse bypass switch! And what's ironic is if you are so worried about sonic damage from a line fuse, then simply leave it out! Look at all the classic tube amps, Dynaco, Fisher, for example that didn't have line fuses. Modern power transformers are built with safe failure modes in mind. Many are even UL recognized having internal fuses or thermal cut-outs. What would be really funny is if Hammond does employ an internal fuse or cut-out. How does Jeff propose to bypass that? But hey, he does have transformer surgery experience.

Edited by Mr. EE

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Posted (edited)
7 hours ago, Jeffrey D. Medwin said:

A key part of what any amp I build uses , is Dennis' L. S.E.S. power supply filter.   As ( soon to be determined - if he is an E.E. from Purdue University  ) DIYer John Hasquin, so eloquently explains it, on Page eight of this thread, L.S.E.S.  it is something the " old timers" ( In E..E. ) have overlooked.  As I explain to you all, it goes against the E.E.'s training on L-Critical chokes and lots of capacitance, and MOST E.Es can NOT wrap their minds around it.  We also have the Dean of E. E., University of Alabama EE School, ridiculing E.E.s , in my letter on page eight.  Hilarious eh ?? 

 

Jeffrey D. Medwin

But why is this new found knowledge from what 2006-2010? not officially published? Or was it 1989 when you say Dennis came up with it? You mean in over ten years no university or corporation has bothered to investigate this theory? What about Purdue? If John Hasquin is an alumni wouldn't they be most likely to publish his work? Look at all the megabuck research being done today in power conversion technology. Electric cars, solar inverters, even getting your smart phone to use less battery power. You don't think that LSES would have some application in all those technologies? After all the output of a modern switch mode power supply is back to a simple half wave rectifier, choke and capacitor right off the inverter  transformer. All the complex regulation happens on the front side. At least some research would have been done by now if there was any practical theory to explore. Do you also believe that in 100 years plus of simple rectifier, choke, capacitor power supply circuits nobody would have stumbled onto this until 2010 or when ever you and Dennis say you discovered it?

 

And it doesn't matter if John Hasquin is an accredited EE or not.  Professionals argue all the time for their scientific agendas. That's why there is peer review and research. If you and John were right, this material would have been officially published by now.

 

And again none of the so called "papers" you present are verified as authentic. Some author's are conveniently deceased but what about the others. AFAIK, at least John Swenson is still around selling his magical Mac Mini power linear supplies*, why doesn't he come to your defense here. Ditto that for John Hasquin if he's still around. Can't the come in here and substantiate their claims you are presenting as their work.

 

*Yup, get rid of that nasty switch mode wall brick that is separated from the MAC by several cable feet. But never mind the numerous internal switch mode power converters on the Mac mother board. Yup, we can't do anything about those so they magically don't cause any audible problems either! Just trust me and buy my after market power supply!

 

If you want my advice, take the money that the Swenson power supply costs and buy a decent quality external DAC with it. Should be a few hundred dollars max. That will truly keep the computer EMI/RFI out of your analog audio signal to the point of inaudibility. And don't waste any money on these USB isolators or "fix it" boxes either. I think John sells those too. Just more snake oil.

Edited by Mr. EE

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40 minutes ago, Mr. EE said:

If I want a next level design, I'll go with the class D modules from Bruno Pultsy(sp?). These are very good class D amp that many high end audio vendors like Theta use. I'm not interested in some amplifier based on 1930s technology.

 

What evidence do you have besides expectation bias that all this point to point  silver wiring makes any performance difference? Especially considering the noise floor and distortion levels in a 1930s amp design? If these SE amplifiers and truly the best, why are they only found in a niche area of consumer HiFi? Why aren't mastering studios using them? Why isn't there any deep pocket research by prominent electronics companies to improve their performance?

 

What I am hearing here is classic audio snobbery! It really not about the actual reproduced sound quality at all. Its all about fashion labels.

 

The zero feedback  SE DC amplifiers I am referring to will not satisfy your EE requirements for best measured performance vs. the commercial-grade PP circuits you have built.  

 

But subjectively on high efficiency transducers (mainly horn speakers) the SE amplifiers deliver an unrivaled musical experience, IMO/IME. 

 

I am fortunate enough to have a  serious audiophile contact in my area who has the financial means to rotate very $$$ expensive tube amps and horn speakers in/out of his system on a regular basis.   I benefit by hearing the best gear and learning from that experience.

 

Once in a while, a PP tube amp gets rotated in for fun, but won't last very long in one of our listening sessions. The SE amps go back in.

 

As for your comment on the noise floor of SE amplifiers, I have looked at this on an FFT in real time - typically the 60 & 120Hz energy is in the

-80dB range below a 1kHz sine fundamental.  The noise floor is usually -10db below that.  This is mostly using 2A3 finals with AC filaments.

 

If you are getting lots of noise out of a SE amplifier, something is wrong - poor orientation of parts, poor grounding , under filtered PS capacity, bad tubes, etc.   

 

Nothing about this is audiophile snobbery. I have listened to many tube amplifiers on great full range horn systems.

 

I know what I want to hear and what sort of gear will deliver that experience. Life is too short for anything less.

 

Tube Hawk 6AQ5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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30 minutes ago, Tube Hawk 6AQ5 said:

 

As for your comment on the noise floor of SE amplifiers, I have looked at this on an FFT in real time - typically the 60 & 120Hz energy is in the

-80dB range below a 1kHz sine fundamental.  The noise floor is usually -10db below that.  This is mostly using 2A3 finals with AC filaments.

 

Tube Hawk 6AQ5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Hum and noise 90db down? That's pretty piss poor even for 1950s HiFi technology! State of the art power amplifiers are around 105db down and source gear these days can easily hit -110db or better.

 

What's even worse is that these flea powered amps require very sensitive speakers to work well. So here, the poor S/N is even further aggravated

 

Sadly using modern technology an SE amp can be made over -100db S/N. DC heaters, Regulated power supply which is fine for class A operation. And some do. But it;s the old audiophile voodoo that eschews using newer technology used to improve classic designs due to mis-understood beliefs.

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2 minutes ago, Mr. EE said:

Hum and noise 90db down? That's pretty piss poor even for 1950s HiFi technology! State of the art power amplifiers are around 105db down and source gear these days can easily hit -110db or better.

 

What's even worse is that these flea powered amps require very sensitive speakers to work well. So here, the poor S/N is even further aggravated

 

Sadly using modern technology an SE amp can be made over -100db S/N. DC heaters, Regulated power supply which is fine for class A operation. And some do. But it;s the old audiophile voodoo that eschews using newer technology used to improve classic designs due to mis-understood beliefs.

Based on your comments, you don't seem to have much experience listening to SE DHT tube amplifiers or high efficiency horn systems.

 

If PP tubes , Class D modules and inefficient  speakers float your boat,  you are welcome to them. They are OK for home theater.

 

As I have stated before, I won't waste my time with that sort of gear for  audiophile reference listening. I know better.

 

Enjoy your afternoon, sir.

 

Tube Hawk 6AQ5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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8 hours ago, Tube Hawk 6AQ5 said:

 

The zero feedback  SE DC amplifiers I am referring to will not satisfy your EE requirements for best measured performance vs. the commercial-grade PP circuits you have built.  

 

But subjectively on high efficiency transducers (mainly horn speakers) the SE amplifiers deliver an unrivaled musical experience, IMO/IME. 

 

I am fortunate enough to have a  serious audiophile contact in my area who has the financial means to rotate very $$$ expensive tube amps and horn speakers in/out of his system on a regular basis.   I benefit by hearing the best gear and learning from that experience.

 

Once in a while, a PP tube amp gets rotated in for fun, but won't last very long in one of our listening sessions. The SE amps go back in.

 

As for your comment on the noise floor of SE amplifiers, I have looked at this on an FFT in real time - typically the 60 & 120Hz energy is in the

-80dB range below a 1kHz sine fundamental.  The noise floor is usually -10db below that.  This is mostly using 2A3 finals with AC filaments.

 

If you are getting lots of noise out of a SE amplifier, something is wrong - poor orientation of parts, poor grounding , under filtered PS capacity, bad tubes, etc.   

 

Nothing about this is audiophile snobbery. I have listened to many tube amplifiers on great full range horn systems.

 

I know what I want to hear and what sort of gear will deliver that experience. Life is too short for anything less.

 

Tube Hawk 6AQ5

 

 

 

You are so right !! 

 

Life is too short to use second best and/or to own sub-performing audio amps !!!   That has been my feeling, and main motivation in DIYing DHT, etc. tube amps,  ever since 1979.

 

Thank you for posting that.  A few good people reading this thread will take notice and appreciate your point of view.   Bravo to you..

 

Jeffrey

 

 

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There's a great divide.  On one hand a well designed push pull tube amplifier which most likely measures quite nicely and with relatively low output impedance vs a well designed (careful operating points, etc) singled ended tube amplifier with minimal ("excess") gain (for the source output vs speaker sensitivity) and no global feedback. 

 

In the high sensitivity world of horn speakers,  the single ended amplifier (if done well) will have its adherents and can be perceived as "better".  That same amplifier might fail miserably with say an 88dB speaker and only a watt or two output.   In the horn world - it gets wild - kinda like "should Harold S. Black be thanked - or spanked for NFB?

 

Here's my old nearly unmovable clunker from 26yrs ago - after losing a houseful of audio stuff (the house was 50ft from the county jail) , I decided to make something which one would regret if trying to steal - its ugly and heavy even with the dinky One Electron UBT-1 transformers

 

It barely squeaked out 3 watts at 30Hz.  It ran Bruce Edgar's first

products - a straight little "100Hz" horn w. JBL 2220H, tractrix midhorn w. JBL LE5, and T35 or Audax bullet tweeter.

 

I don't think it would drive a Karlson with heavy percussion.  I like a couple of hundred watts of cheap solid state for that duty.

 

Maybe its best to agree to disagree on the two approaches.

 

 

OB FAST with tube + SS amplifier ? - diyAudio

 

 

 

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         6-3-19   Progress Photos

 

Well, I tried to use 8 AWG in the distance between the KT88 tube socket's Cathode Pin and the tube's Rk.  See the beefy two red wires?   This is the second time in audio anyone's likely ever done this.  8 AWG Mil Spec wire will have great signal transfer efficiency, and because of the 133 silver plated copper strands, it is likely to keep an OK high frequency response.

 

I was going to do this span in 10 AWG Mil Spec, but I have experimentally used 8 AWG tonight, and it seems to solder in OK,  325 Watt iron 

 

1329275445_snip6-31.JPG.eb811d1c09789267426c89dc4c3e33b0.JPG

  

                                                                                            m22759/11 8

 

                 Such Cathode return wiring for a KT88 has never been used before in audio. What will be heard ( from the music  )??  I am interested

       to find out !!   It was much nicer , listening-wise, last week on the 2018 6005 SE DC amp - when similarly executed.  Surprisingly-so to me.   

       Most casual builders ( and stuck-in-the-mud non-experimenters / non- listeners ) might likely fully miss the point of whats being done. 

                             " An inch of bad wire can ruin the musical experience"                Robert W. Fulton 1977.

 

 

 

970655197_6-33snip.JPG.3277edd75571209c404f55186235e2ce.JPG

                                                                                                      RED wire, above and below...see.

                                        2030118816_MasterSchematic8AWGSNIP-Highlighted7.thumb.jpg.3bebef977aa121c1862c5fc3303ad5b2.jpg

 

 

2110265727_6-34snip.JPG.4829b3387b71fa2571216523da22ed3b.JPG

 

 

274687696_6-35snip9.jpg.cdc8ea5ebd3f512a39ab8df6c3480340.jpg

 

 

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5 hours ago, Jeffrey D. Medwin said:

 

 

You are so right !! 

 

Life is too short to use second best and/or to own sub-performing audio amps !!!   That has been my feeling, and main motivation in DIYing DHT, etc. tube amps,  ever since 1979.

 

Thank you for posting that.  A few good people reading this thread will take notice and appreciate your point of view.   Bravo to you..

 

Jeffrey

 

 

To be honest, I could go to eBay and buy a Chinese made PP tube amp similar to what has presented here for less than $1K - good enough for home theater or casual listening duties.  

 

PP tube amps are what I started out with in this hobby several decades ago with inefficient panel speakers. 

 

But after I was exposed to a massive full loaded horn system with SE tube amplifiers on the main drivers - there was no turning back to PP tubes.

 

Actually, even a modestly budgeted low DCR SE amp beats the pants off of 90% of SE and PP amps out there subjectively on high efficiency horns, IMO/IME.

 

The fact that you spent many hours with Dennis Fraker at RMAF listening to his 2A3 amps gives you a massive advantage in knowing what a great SE amp/system should sound like vs. 99% of most audiophiles have experienced.  

 

In this thread we can see the benefit of that experience.

 

Tube Hawk 6AQ5

 

 

 

 

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19 hours ago, Tube Hawk 6AQ5 said:

I know what I want to hear

Bingo!

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Posted (edited)
9 hours ago, Tube Hawk 6AQ5 said:

To be honest, I could go to eBay and buy a Chinese made PP tube amp similar to what has presented here for less than $1K - good enough for home theater or casual listening duties.  

 

PP tube amps are what I started out with in this hobby several decades ago with inefficient panel speakers. 

 

But after I was exposed to a massive full loaded horn system with SE tube amplifiers on the main drivers - there was no turning back to PP tubes.

 

Actually, even a modestly budgeted low DCR SE amp beats the pants off of 90% of SE and PP amps out there subjectively on high efficiency horns, IMO/IME.

 

The fact that you spent many hours with Dennis Fraker at RMAF listening to his 2A3 amps gives you a massive advantage in knowing what a great SE amp/system should sound like vs. 99% of most audiophiles have experienced.  

 

In this thread we can see the benefit of that experience.

 

Tube Hawk 6AQ5

 

 

 

 

Yes and I could also go to Ebay and buy one of several 2A3 designs for around $1000 that will sound just as good as the Serious Stereo product. What determines the sound is the topology, the tubes, and the output iron. Of course so does the power supply but we have determined through visual observation the Serious Stereo amp seems to have more than sufficient filter capacitance as not to be classified as a LSES.

 

All this silver hookup wire, three dimensional layout, stacks of brass washers, make no audible difference in sound reproduction based on my experience of audio amplifiers in general.

 

If one indeed likes the signature sound of the SE amps with efficient speakers, there are far more cost effective ways to get it even if you don't DIY.

Edited by Mr. EE

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Mr. EE,

 

I am very impressed with the quality of the workmanship on both projects you have shared here - and I say this as a user and builder of primarily singled-ended designs!  And I must admit that I have heard some very, very respectable PP designs as well.  It is in fact possible for both topologies to quite happily exist under the same roof.  I think we can discuss both in terms of one or the other being simply a matter of personal choice.  I would add, too, that the efficacy of either may, in a very large part, have to do with design and implementation rather than class of operation and/or the fact that one happens to be push-pull and the other single-ended.  Did you mention what speakers you’re driving with that really nice looking valve amp?  Maybe I missed that detail...

 

I also use speakers that are capable of over 100 decibels with a single watt, and what you have said about any residual 60 cps hum from AC on directly heated cathodes can definitely be be aggravating.  I suspect it’s a compromise one who prefers AC heaters on those big output stage triodes is willing to accept.  I have in fact used regulated DC on both 2a3 and 300Bs, and just seemed to convince myself AC sounded better somehow....or I’ve fooled myself into thinking so!  Most likely the latter.

 

Your lead dressing is really exemplary, and no doubt you took care not to bundle signal and AC mains wiring together.

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1 hour ago, Mr. EE said:

Yes and I could also go to Ebay and buy one of several 2A3 designs for around $1000 that will sound just as good as the Serious Stereo product. What determines the sound is the topology, the tubes, and the output iron. Of course so does the power supply but we have determined through visual observation the Serious Stereo amp seems to have more than sufficient filter capacitance as not to be classified as a LSES.

 

All this silver hookup wire, three dimensional layout, stacks of brass washers, make no audible difference in sound reproduction based on my experience of audio amplifiers in general.

 

If one indeed likes the signature sound of the SE amps with efficient speakers, there are far more cost effective ways to get it even if you don't DIY.

$1K would not even pay for the bypass caps in one of Dennis Fraker's  Serious Stereo 2A3 mono amplifiers.

 

And you will not find a well crafted SE amplifier with similar build characteristics or subjective performance attributes at such a modest price point on eBay.  

 

There are many levels to the audiophile hobby and you seem sort of clueless to that reality.

 

Thanks for sharing and providing me with a good chuckle after a long day at work. 

 

Tube Hawk 6AQ5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Posted (edited)
27 minutes ago, Tube Hawk 6AQ5 said:

$1K would not even pay for the bypass caps in one of Dennis Fraker's  Serious Stereo 2A3 mono amplifiers.

 

And you will not find a well crafted SE amplifier with similar build characteristics or subjective performance attributes at such a modest price point on eBay.  

 

There are many levels to the audiophile hobby and you seem sort of clueless to that reality.

 

Thanks for sharing and providing me with a good chuckle after a long day at work. 

 

Tube Hawk 6AQ5

 

 

I am clueless to your reality like $1K spent for a cathode bypass cap on a HiFi amplifier? Do you know why the bypass cap is there? Do you know exactly how it works in the circuit? Or do you just blindly believe it must be expensive and exotic because an audiophile amp vendor with no formal electronics background says so?

 

When it comes to the realities of electronic design I'm afraid you  are clueless blinded by snakeoil.

Edited by Mr. EE
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Posted (edited)
1 hour ago, erik2A3 said:

Mr. EE,

 

I am very impressed with the quality of the workmanship on both projects you have shared here - and I say this as a user and builder of primarily singled-ended designs!  And I must admit that I have heard some very, very respectable PP designs as well.  It is in fact possible for both topologies to quite happily exist under the same roof.  I think we can discuss both in terms of one or the other being simply a matter of personal choice.  I would add, too, that the efficacy of either may, in a very large part, have to do with design and implementation rather than class of operation and/or the fact that one happens to be push-pull and the other single-ended.  Did you mention what speakers you’re driving with that really nice looking valve amp?  Maybe I missed that detail...

 

I also use speakers that are capable of over 100 decibels with a single watt, and what you have said about any residual 60 cps hum from AC on directly heated cathodes can definitely be be aggravating.  I suspect it’s a compromise one who prefers AC heaters on those big output stage triodes is willing to accept.  I have in fact used regulated DC on both 2a3 and 300Bs, and just seemed to convince myself AC sounded better somehow....or I’ve fooled myself into thinking so!  Most likely the latter.

 

Your lead dressing is really exemplary, and no doubt you took care not to bundle signal and AC mains wiring together.

Well like I said before, there is nothing wrong with bundling wires as long as you bundle the right wires! Even bundling input wires with the AC line can be allowed under the right conditions though not advisable if it can be avoided.

 

Note that in my 4 channel SS amp the unbalanced module inputs were actually bundled with the speaker output wires! Now in the KT66 tube amp, the unbalanced input leads were loose and kept close the the sides of he chassis. Different conditions. The SS amp has a very low impedance driver (50 ohms approx) on the input board so those module input leads are very immune from EMI/RFI. OTOH, the KT66 amp has much higher input impedance. Input leads are much more susceptible to EMI/RFI ingress even with the shielding.

Edited by Mr. EE

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11 minutes ago, Mr. EE said:

I am clueless to your reality like $1K spent for a cathode bypass cap on a HiFi amplifier? Do you know why the bypass cap is there? Do you know exactly how it works in the circuit? Or do you just blindly believe it must be expensive and exotic because an amp vendor says so?

 

When it comes to the realities of electronic design I'm afraid you  are clueless blinded by snakeoil.

Any goofball can cut and paste electronic theory from a Wiki page, so I am not impressed by people posturing as "EE" asking remedial questions.

 

You seem to  have no SE building or listening experience as far as I can tell and none regarding the sort of SE builds presented in this thread or you would know the answers about bypass caps. 

 

This exchange is beyond time wasting to me at this point.

 

Believe as you wish, sir.  It makes no difference to me.

 

Tube Hawk 6AQ5

 

 

 

 

 

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Posted (edited)
5 minutes ago, Tube Hawk 6AQ5 said:

Any goofball can cut and paste electronic theory from a Wiki page, so I am not impressed by people posturing as "EE" asking remedial questions.

 

You seem to  have no SE building or listening experience as far as I can tell and none regarding the sort of SE builds presented in this thread or you would know the answers about bypass caps. 

 

This exchange is beyond time wasting to me at this point.

 

Believe as you wish, sir.  It makes no difference to me.

 

Tube Hawk 6AQ5

 

 

Well again I posted several examples of my experience, at your initial request BTW. You have shown us nothing here except your shilling for Serious Stereo products.

 

We'll let the readers judge for themselves. I have nothing against SE amps for those who like them. I do have a problem with the promotion of grossly overpriced SE amps who's superior advertised attributes are built on a foundation of junk science. 

Edited by Mr. EE
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Forget the sciencey stuff. Let me see that $1000 bypass cap!

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Posted (edited)
32 minutes ago, Tube Hawk 6AQ5 said:

 

Again, you have displayed no SE amplifier building or listening experience but you feel justified in sniping at Medwin or Fraker from the sidelines.

 

You are not even in the same universe as an audiophile compared to those guys.

 

I would use your KT66 amp as a door stop at my next audiophile listening session because nobody would want to hear it.

 

How's that for being a shill, you nerd!

 

TH 6AQ5

 

 

Why are you so fixated on the SE amplifier? What is so special design wise about an SE versus a PP amp. As far as basic construction and components go, they are no different. Yes they both have different circuit designs, attributes, and different applications but what make you think somebody who has built a PP amp either can't or hasn't built an SE amp?

 

I'll ask again when are we going to see some of your work. You first insisted I had nothing to show. Let's now see some of yours.

Edited by Mr. EE

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2 hours ago, Tube Hawk 6AQ5 said:

$1K would not even pay for the bypass caps in one of Dennis Fraker's  Serious Stereo 2A3 mono amplifiers.

 

And you will not find a well crafted SE amplifier with similar build characteristics or subjective performance attributes at such a modest price point on eBay.  

 

There are many levels to the audiophile hobby and you seem sort of clueless to that reality.

 

Thanks for sharing and providing me with a good chuckle after a long day at work. 

 

Tube Hawk 6AQ5

 

Out of curiousity, do you have any idea  what particular property the $1K+  bypass capacitors have that would account for their expense?  What, technically, are they able to do that cheaper, standard capacitors cannot do?

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