Does anyone care to ask an amplifier designer a technical question? My door is open.


I closed the cable and fuse thread because the trolls were making a mess of things. I hope they dont find me here.

I design Tube and Solid State power amps and preamps for Music Reference. I have a degree in Electrical Engineering, have trained my ears keenly to hear frequency response differences, distortion and pretty good at guessing SPL. Ive spent 40 years doing that as a tech, store owner, and designer.
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Perhaps someone would like to ask a question about how one designs a successfull amplifier? What determines damping factor and what damping factor does besides damping the woofer. There is an entirely different, I feel better way to look at damping and call it Regulation , which is 1/damping.

I like to tell true stories of my experience with others in this industry.

I have started a school which you can visit at http://berkeleyhifischool.com/ There you can see some of my presentations.

On YouTube go to the Music Reference channel to see how to design and build your own tube linestage. The series has over 200,000 views. You have to hit the video tab to see all.

I am not here to advertise for MR. Soon I will be making and posting more videos on YouTube. I don’t make any money off the videos, I just want to share knowledge and I hope others will share knowledge. Asking a good question is actually a display of your knowledge because you know enough to formulate a decent question.

Starting in January I plan to make these videos and post them on the HiFi school site and hosted on a new YouTube channel belonging to the school.


128x128ramtubes
If I am a good guesser I would have to say that since wolf_garcia plays guitar and he has mentioned the Grateful Dead in a few of his posts the reference would be to the Doug Irwin Wolf guitar (known for the Dire Wolf inlay) made for Jerry Garcia. I’ve seen Garcia play it a number of times and the current owner of the guitar has made it available to be played by others, most notably Steve Kimock who Garcia really respected as a guitarist. You can see it here:

https://liveforlivemusic.com/features/a-brief-history-of-jerry-garcias-five-most-well-known-guitars/

[Side Note: Upon Garcia’s death some of the Irwin guitars made for him were auctioned off to help pay for Doug Irwin’s medical expenses, and it got a little gnarly with the Grateful Dead asking for a piece of the action since they contended none of the equipment ever belonged to Garcia, but was purchased under the Grateful Dead corporate umbrella. In essence the guitars weren’t Garcia’s to give away. So the band got to keep a couple of the guitars in the legal settlement. So much for that community thing.]

As for the Dennis Had Inspire amp, I have a lot of respect for Dennis having owned and enjoyed very early Cary equipment, but knowing someone that measured one of these amps I couldn’t ever bring myself to buy one. If anyone wants to have their amp measured Roger is game to do it (even brought his equipment to Burning Amp one year to measure amps). He keeps notes on all the amps (and some preamps) he has measured. I think Roger has measured most of my equipment and even I was surprised at some of the results.

@cakyol

I predict that these capacitors will be in a vicinity with a temperature of about 60 - 65 C most of the time
  • Definitely use 105°C parts.
  • Cap ESR goes up with age, so while the C may still be good with old parts, the increased ESR will play havoc with Z.
  • Dielectric degrades with time and more so when not charged.
  • A small DC fan could cool the temperature by 30°C. 12VDC fan on 3V is inaudible from 6 inches. Two 60mm fans operating push pull will keep things very cool.

You may find this link interesting. "Determining end-of-life, ESR, and lifetime calculations for electrolytic capacitors at higher temperatures"
https://www.edn.com/design/components-and-packaging/4326347/Determining-end-of-life-ESR-and-lifetime...
My name has zero to do with Jerry Garcia...I borrowed the last names of two people in my office (Tom Garcia and Dave Wolf) around 20 years ago for an open mike thing I was doing, and I kept the name for professional use and to disguise my identity as an international celebrity. As far as the Dead goes, I recently found a ticket I didn't know I had kept (I don't keep stuff like that) in a bag of papers from my late mother's stuff...3 bucks for a Dead show I saw in Honolulu on Jan 3rd 1970...framed it! There's a recording of that show someplace that I should try harder to find, just to complete the set.

I like the fact that my Dennis Had amp is relatively "unmeasured," although I'm sure somebody has looked into that...if measurements for the thing were available, I still would not care one iota as the thing simply reproduces music so beautifully among my gear pile it's earned its place several times over.
With some affinity for The Dead, corporate or not
in the old days before they had to feed the wall of sound monster, they used 4 x MC240 in bridged mode to run the PA
those are 50# each, so that was an ungainly bit of plywood all four were attached to....
Roger - one of my first memories is also at age 4 watching the MC240 and Bozaks arrive in my parents house
no $ for furniture, plenty for music and HiFi

i still have the 1961 MC240 / MX110 Z

have you measured a 240 ??????


Hi Ramtubes,

”Are we talking about NYAL Futterman? Perhaps I have missed something in this thread? Do you mean Jon Snyder?”

You will be sorry you asked!

Let me fill you in on my setup.

When I was 14 years old (that’s many many years ago. It was the Summer of Love), I started out with a Dyna 70, a Dyna PAS, a Garrard table, a Stanton cartridge, and a pair of Lafayette two way speakers.

Around the late 80s, I had built up to the configuration that I more or less have today:
Altec Lansing 604Cs and 604Ds
Mastering Lab crossovers
New York Audio Lab (NYAL) OTL3s (Futterman)
Beard P505 preamp
Sumiko MMT arm
VPI HW table (MK II then, MK IV with SAM today)
Koetsu cartridge (Black then, Onyx today)

and just this month, I added a Velodyne 15 inch sub that keeps anything below 70 or 75 hz from reaching the Altecs.

The speakers have have been re-coned three times, most recently three years ago, each time by Gabriel Sound in NJ. They do a lot of pro stuff: stadium work for Pink Floyd for example.

Jon Specter, not Snyder, is his name. I found him accidentally when I was following an Ebay listing for a pair of Futtermans. After many weeks with not a nibble, I “contacted the seller” - Jon - and suggested he add search words like Macintosh, Conrad Johnson, etc because “outside of a small circle of friends” as the late great Phil Ochs said, nobody knows what a Futterman is.

Not yet knowing who the seller was, I asked him how he came upon them, and he says he built them himself when he was at NYAL.

How serindipitous. Recently, a tube in one of my Futtermans blew up - literally, glass shattered - and seemed to have taken out half the circuitry. Until then, George Kaye had done my repairs, and while he does excellent work, he lives up in Brattleboro and it’s a schlep (he has his own company, btw, Moscode) and it turned out that Jon lives in Staten Island! So I asked him if he could repair the amp. He said yes but suggested that I listen to his pair - which had the triode mod - and if I liked them to just swap.

So we tried that, and they sounded great, but cosmetically they were a different iteration which I didn’t like so I declined the swap and had him do the mod on my pair and relied on my Dynas while I waited. He relisted his pair per my suggestion and sure enough he found a buyer - in Austin Texas, I believe - in three days.

John did another mod for an old Cooper Union alumni colleague of mine last year: he says that to date, those are the only three OTL3 Futtermans that he is aware of with the triode modification. I know George was involved because I was at Jon’s shop a couple times when he called George to consult on some issues, and I was still keeping in touch with George myself.

The triode mods actually have more power somehow. I know Jon put a tiny little transformer in there somewhere, he explained what it is for and that it’s not in the output circuitry but I’m not technical enough to remember.

I think you said that you dont believe in “audio grade caps” but Jon put a bunch of them in the Futtermans, the Beard, and the Mastering Labs. Jon said they would take about 100 hrs to break in and I didn’t hear anything at 100 hrs. At 150 I still didn’t hear it and I was beginning to wonder if I wasted some money, but at 200 they kicked in and I did in fact hear a difference, nothing dramatic, it was subtle: the sound became silkier and more open.

Btw, Jon also plays a great blues guitar in a band that he has, and is a cousin of Al Kooper.

The result of this configuration of components and the work put into them is a very, very lifelike presentation. I have heard equipment - some of it quite expensive, eg speakers that cost three times as much as my entire system - in audio showrooms that sound more accurate in terms of the timbre/texture of voices, instruments, etc. And you must know that for decades audiophiles would sneer at Altecs. I’m sure there are many in this forum. But I am telling you, I have never heard anything that comes even remotely close to having the lifelike acoustical space, nor the absolutely incredible dynamic punch that this configuration does. With some recordings - I’m thinking of the Frank Sinatras in particular, both Capitol and Reprise era, even the mono presses - the effect is of a startlingly present and holographic sound. The one weakness had been the bass was sometimes wimpy. With my new listening room and the Velodyne, that problem is gone.

As for Pearson: I sometimes read reviews in Stereo Review of components costing $30K to ... what is that pair of horn speakers (funny how horns are back!) for $600K? Magico? I would regularly post the comment “Is the Law of Diminishing returns somehow made obsolete in the audio world? Where is Haffler now that we really need him?”

One anecdote with regard to expensive speakers and irresponsible audio designers/manufacturers and then then I will look forward to your reply:

I was walking home one day, when I was still in NoHo in NYC, and I saw a pair of speakers through a storefront window in an audio showroom that caught my attention. I went in for a closer look.

The cabinet was about the same same size and proportions as mine were. The speakers had no grille cloth, so I could see the coaxial driver, identical to mine. The only thing different was the cosmetics of the cabinetry, which had a beautiful brick colored wood finish. I looked at the price tag, and then asked for a salesperson. I asked him what went into the $33,000 cost of the speakers.

After about 10 minutes he more or less concludes, and I say “that’s all interesting. Now could you tell me if that is a 604C or a 604D driver in there, or did the manufacturer copy it from scratch?” He looks a little confused. I continue “I know that’s an Altec 604C. I’ve been using them for almost 40 years. In your presentation, however, you did not once mention that fact. What distinguishes this speaker from the 604?” He then goes back to the crossover design, and I interrupt “I heard you the first time. It sounds like the Mastering Lab crossovers, by Sachs. You did not mention him. Everyone knows that the stock crossover in the Altec wasn’t what it should be, and Sachs came up with a two shelf design. I see similar knobs on the back of the cabinet.”

I continue “So, it seems like, excepting for the craftsmanship of the cabinet, which is extraordinary beautiful, these are the exact same speakers as mine - drivers, crossovers, cabinet geometry. Except that I put $3,300 into acquiring mine and getting them to perform at their best, while you are asking for ten times that amount. Are you suggesting that the cabinet aesthetic is worth the $29,700 difference? Or is there some other magic that this manufacturer has put into the performance - which is where the rubber is supposed to meet the road - of this pair of speakers? Could we remove the back panel, maybe, and see inside, see what has been put into this?”

By this time, I had attracted a small crowd. I concluded by saying “Sorry, I have an appointment to make and I’m already late, maybe another day! Thank you for your time!” I left, figuring that some dumb Wall Street sucker who doesn’t know what to do with his money will pick them up. They did, in fact, sell within the month.