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Jeffrey D. Medwin

KT88 Direct-Coupled Design

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Posted (edited)
1 hour ago, Jeffrey D. Medwin said:

 

It isn't stupid to those who may be able to comprehend it !!  

But the problem is nobody can comprehend it. A layman lacks the background in university physics to analyze the technical points. And those who do have that knowledge and education can't make the numbers work either based on well established and proven theory.

 

Yet some stereo store owner has made this groundbreaking discovery years ago and to date it still has no commercial acceptance!

Edited by Mr. EE

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5 hours ago, Mr. EE said:

2) Wire tie color? Huh? Are we saying the color or rather the plastic composition of the wire tie has some audible effect? First the wire tie is over the wire insulation. The wire tie never touches the electrical conductor. As for compositions of insulator plastics including color pigments influencing the signal, yes perhaps at RF frequencies and under the right conditions. But this idea is absurd at audio frequencies and the lengths in play.

 

Yeah, but aren't you a classically trained engineer?

 

:ph34r: :emotion-14:

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4 hours ago, Mr. EE said:

Bottom cover removed, quiet fan moves air through underside. Front panel has calibrated clip indicator, when the audio peaks on the KT66 plates equal a set point for more than 10ms, the clip LED for that channel comes on for 100ms.

 

The two flat driver boards are obvious. The two vertical boards, left is the 380v driver regulator with MOSFET heat sinked to top plate, the right board is the Gyrator that is a modern substitute for a power supply choke. It also contains the delayed B+ turn on circuit which is done at a low voltage level in the MOSFET gate circuit. No HV relays needed. The board on the lower right is the bias regulated power supply. The small power transformer powers the front panel clip indicator board and the DC fan. Lower left board is of course the power supply rectifier and filter caps. Two 470uf caps in series. Those little PC boards behind each KT66 is the bias adjust pot for that tube.

 

Anybody see the unique difference in the driver board layouts? They are mirror imaged from each other to minimize the tube sockets lead length! Easy to do with DIY PC boards, Just flip the photomask when exposing the second board!

 

All your details are in vain.  I understand your entire house faces west....  the earth's magnetic pull would be more beneficial to you if you adjusted the direction your house faces to the far more neutral south east. 

 

(no worries, I'm sure you must have skipped out on that day's class when getting schooled)

 

:unsure2:

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4 minutes ago, Coytee said:

 

Yeah, but aren't you a classically trained engineer?

 

:ph34r: :emotion-14:

Yes, most unfortunate if I am to ever design good audio equipment!

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6 hours ago, Mr. EE said:

I'll do a seperate post on the decoders and processors if there is any interest.

Yes please, by all means.

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Now if I want more open high end and better bottom do I space both blue and red zip ties equidistant all along the wire bundle? Or do they need to overlap? Or God forbid do I need to choose one and give up on the other? 

Did I mention Floobydust?

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1 hour ago, Mr. EE said:

Well you tell me!

 

1)What is the problem with copper circuit board traces, btw they are solder plated with standard 60/40 solder? The dielectric material is standard FR4. What is the capacitance versus the impedance of the circuits and the operating frequencies and bandwidth? How is this circuit board construction causing s negative performance of this audio amplifier?

 

2) What is the problem with stranded wire? That does happen to be mostly silver plated Teflon but only because I have a cheap source of it. And it is very nice to work with. But I'm not going to claim it sounds any better than plain old PVC copper wire because there is no scientific evidence it should or does.

 

3) Those OPTs are the Hammond potted series, a step up from the standard line. In what way are they deficient in your mind?

 

4) What is wrong with electrolytic caps as long as they are used properly? Lifespan of only 20 years? OK but besides that?

 

And take special note I said nothing of it's performance. I'm sure it sounds just like many other DIY and commercial designs based on the same circuit topology. I think it sounds good. And I am happy to show it off and answer questions as to my specific design choices. But I'm not going shove it down everybody's throat as the absolute best and only KT66 amp ever built because nobody can honestly make such a distinction - for any amp!

 

Why don't you ponder those four questions above. Then consider why a practicing EE and electronics hobbyist with commercial electronic design experience would make those choices.

 

I didn't mean to suggest that there was anything "wrong" with the PP KT66 amplifier. 

As you suggest, your amplifier sounds just like other similar designs and sounds subjectively good.

 

But is it a "next level" design/build that represents the absolute best of breed?   That is what I am looking for in audio.

 

I own a few similar PP 6650's - commercial amplifiers with printed circuit boards used to drive inefficient speakers in a home theatre system.

 

These PP amps sound OK, good enough for watching movies or casual listening while I do some house chores.

 

But compared subjectively to SE DC amplifiers with point to point construction, wired in stranded high purity silver featuring the best OPT's like Tango or Tamura … I can't be bothered with them.  

 

A superior level of subjective audiophile performance has to be experienced in the flesh. Once you hear it, there is no going back.

 

Tube Hawk 6AQ5

 

 

 

 

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Well...all of this unimbibed Kool-Aid I have been reading makes me want to have a beer, instead   enjoy the Kool-aid folks!

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                       6-1-19  Progress Photos 

 

Did Heater wiring to KT 88, both sockets, and drilled / tapped two holes to make a second Brass panel support, for the two 4 uF DynamiCaps caps, destined to lie close to the hot chassis.   This assembly is for the Dennis Fraker Final Filter ( L/C)  to each  KT88's G2/Screen .  With the newly added brass plate, these two 4uF caps will NOT be subjected to excessive heat.  Long term reliability thinking / designing here !!   Plan ahead. 

 

Have fun looking . Chassis up front, half empty now, will begin to get crowded ............soon !! 

 

Going to order 20 feet of 10 AWG Mil Spec, from Apex Jr.Surplus Electronics  on Monday.  Have 12 and 8 AWG, need some 10 AWG  in a few key places !!

 

 

 

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                          829117568_6-1B.JPG.69293d727170fabd7ed29e7bdd1cad46.JPG

 

                                                 Midnight Blue Wrinkle, powder coated finish.  14 gauge steel, welded corner chassis.   Durable, long term.

 

 

 

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 Brass washer pyramids for mounting, 2+2+2 different washer diameters. .  Wires crossing at 90 degrees to each other. Ultra short Rk return-to-ground bus           distance ( top of photo) .  Love it.

 

 

 

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                  Looks nice - to me. Jitter-bug sanded brass piece with 80 grit, then  Clear-Coated it.  8 AWG  as ground bus sounds great to me in 6005 amp..

 

 

 

                          877425854_6-1E.JPG.e6b4fdc2cf9cfecc6b6c17edb55586b8.JPG

 

                                                             Brass plate specifically added to raise these two 4 uF Dyna\miCaps caps off of a hot Chassis,

                                                         Short lead lengths were planned for, in advance.  Layout is critical in a SE tube amp. All is inter-related.

 

Thank you,  for looking.

 

Jeffrey

 

 

 

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8 hours ago, Mr. EE said:

But the problem is nobody can comprehend it. A layman lacks the background in university physics to analyze the technical points. And those who do have that knowledge and education can't make the numbers work either based on well established and proven theory.

 

Yet some stereo store owner has made this groundbreaking discovery years ago and to date it still has no commercial acceptance!

 

Hopefully you did at least de-gauss your cable ties, as recommended by the late gentleman from the AA Tweakers' Forum!

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My wife, who has become quite a techie over the years, has been thoroughly enjoying this thread!  She is amazed that Jeff is going to spend more on his 4 Dynamicaps at $66 each than the entire parts cost of one of my budget designs!  She also couldn’t imagine spending $50 for a single tube socket which she doesn’t believe could work any better than the NOS Cinch sockets that I normally use.  And, I can’t repeat what she said about cable tie colors affecting the sound......

 

This is what makes the hobby so much fun.

 

Maynard

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45 minutes ago, tube fanatic said:

She also couldn’t imagine spending $50 for a single tube socket which she doesn’t believe could work any better than the NOS Cinch sockets that I normally use.  And, I can’t repeat what she said about cable tie colors affecting the sound......

 

 

Obviously she's been classically trained as an engineer....  probably holds a Phd...otherwise she'd get it.

 

Just saying...

 

(sorry wifey!!)

 

:wub:

 

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Smiles aside, I will say that I respect anyone that's able to build this stuff and the detail that's going into this (as well as others who build these things).

 

I sit back & wonder....  what causes someone to wake up one morning, decide to do this and document / comment to the level he has....all the commentary, the pictures with labels...

 

In the beginning, I totally felt it was a precursor to some sales pitch which has yet to come.  I keep waiting for it....and it's yet to come.  Makes me think perhaps I'm wrong and he might just be a consumer of highly caffeinated beverages.

 

 

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13 hours ago, Coytee said:

Smiles aside, I will say that I respect anyone that's able to build this stuff and the detail that's going into this (as well as others who build these things).

 

I sit back & wonder....  what causes someone to wake up one morning, decide to do this and document / comment to the level he has....all the commentary, the pictures with labels...

 

In the beginning, I totally felt it was a precursor to some sales pitch which has yet to come.  I keep waiting for it....and it's yet to come.  Makes me think perhaps I'm wrong and he might just be a consumer of highly caffeinated beverages.

 

 

 

 

Coytee, 

 

Let me explain myself to you.  When I came home from the hospital, my Dad owned an ALTEC 604,  (their first coaxial ), and Mom nursed me with that 604, giving us WOR, the New York City Classical FM radio station, playing nice background music. Dad took me by the hand, his young child, and we traveled from Trenton N.J.  to N.Y., N.Y. to attend High Fidelity shows in NYC hotels.   When I was maybe eight years old or so, Dad bought the newly released ALTEC 604B model, and the Medwin home had STEREO !!  My Dad was cool.  Bought a VW bug in 1957, a Lambretta 150 CC motorscooter in 1958, and a Saab (93 (?) in 1962.

 

On my own, out of school, my first consumer purchase in 1968 was a pair of Tannoy 15 Inch ( got the driver- size right ) Monitor Golds in GRF enclosures.   When I drove them with a ST-70 and a Mac C-22, I KNEW something was wrong, funky, and it was likely the amp, not the speaker.  Speakers were way better then ( and today )  then any of the existing amps I used back then.  Starting in 1962, I was buying L.P. s for myself. ( Have over 10,000 now ). 

 

On Page eight of this thread, you have my audio amplifier history, starting with meeting Fulton, Bob Fulton, in 1978.  Mr. Fulton always would tell me, amps, not speakers, are the big problem in audio.  Fulton died in 1988, and Dennis Fraker became my second close Audio Mentor and friend.  We two shared a like interest.  Dennis , besides being a sharp-minded audiophile and a great guy, owned and technically designed / serviced Movie Theatres for decades.  Since 1998 - he builds the worlds best sounding and performing 2A3 amps, in my experience.  

 

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 ?? 

 

The typical .E. E.s  rigid education, and inability to think out of the box, precludes them from true understanding.  None of the E.E.s who post up here have ever even heard this type of amplifier, nor will they take the time to open-mindedly read Swenson and Hasquin compilations I freely offer to all.  They already THINK that they know the correct answer.  They will ascribe false reasoning to support " their turf ". .  That is their problem, and great loss, not mine !!

 

SO, Coytee, with me being 74 1/2, and my mentor getting older, I am doing this tube amp build thread for the sake of long term posterity.  So that his ( and my ) lifetime of audio work in amplifiers, does not get lost .   I am VERY thankful to be able to document what is most likely the world's first KT88 directly-coupled amp build, on the Klipsch Forum.  Thank you all - for following along.  Interesting isn't it.  Best of all, its an all- true story, and it is REAL !!

 

Does this make sense to you now sir??

 

Best to you, and ALL E.E's.  There are some very good ones out there, and I appreciate them greatly.

 

Jeffrey D. Medwin

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Moderator, please delete this box.  No post was intended. Thank you very much.

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On 5/30/2019 at 3:28 PM, Tube Hawk 6AQ5 said:

 

This is a master class in SE tube amps from a man who was mentored by the legendary Dennis Fraker of Serious Stereo fame.

Tube Hawk 6AQ5

 

 

hogwash.. master class ???... Fraker legendary ???  LOL... maybe in his, medwin and your mind...

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14 hours ago, tube fanatic said:

My wife, who has become quite a techie over the years, has been thoroughly enjoying this thread!  She is amazed that Jeff is going to spend more on his 4 Dynamicaps at $66 each than the entire parts cost of one of my budget designs!  She also couldn’t imagine spending $50 for a single tube socket which she doesn’t believe could work any better than the NOS Cinch sockets that I normally use.  And, I can’t repeat what she said about cable tie colors affecting the sound......

 

This is what makes the hobby so much fun.

 

Maynard

 

Hello Maynard !!

 

After 4 or 5 tube insertions, the standard Cinch socket gets " wallowed out ", such that the tube's pins are not held as tightly as the first (or second ) tube pin insertion.  The Jakeband ( Italian-Parma ) sockets are precision made of high quality materials, that will not as easily wallow out over time. 

 

In an amp with a mu of 100 Input tube, and a mu of 4 to 12 Finals, the majority of what we hear IS the input stage.  If the Input stage " misses out " in producing the full music information from our source, HOW can the Finals tube "make it up??"   It can't.  Never !! 

 

SO, I spent my money where it counts the most.  I always do this : shunt regulate the Input tube.  The Shunt Regulator ( just one part ! ) is drawing about  ten times more than the audio tube.  Imagine what THAT does.  If you can't imagine it, I can tell you -  its mandatory for higher quality amplification Maynard.   

 

I just do and use what works, as needed.  As determined by all prior amp building, experimenting,  and listening .  Build and listen, re-build and listen, no O-scope used typically. 

 

I appreciate you always Maynard..  Lovely to hear you have a good wife.  You deserve each other I bet !!

 

Jeffrey 

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13 hours ago, babadono said:

Did I mention Floobydust?

 

Richie Havens Front Cover copy.jpg

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

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

 

I didn't mean to suggest that there was anything "wrong" with the PP KT66 amplifier. 

As you suggest, your amplifier sounds just like other similar designs and sounds subjectively good.

 

But is it a "next level" design/build that represents the absolute best of breed?   That is what I am looking for in audio.

 

I own a few similar PP 6650's - commercial amplifiers with printed circuit boards used to drive inefficient speakers in a home theatre system.

 

These PP amps sound OK, good enough for watching movies or casual listening while I do some house chores.

 

But compared subjectively to SE DC amplifiers with point to point construction, wired in stranded high purity silver featuring the best OPT's like Tango or Tamura … I can't be bothered with them.  

 

A superior level of subjective audiophile performance has to be experienced in the flesh. Once you hear it, there is no going back.

 

Tube Hawk 6AQ5

 

 

 

 

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.

Edited by Mr. EE
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