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This is a general question.
Let's say you are restoring and upgrading a tube amp. Is your goal to make it sound a clean as possible. By that I mean balanced, no distortion, new parts and a razor sharp square wave.
With all things being equal like iron, tubes, etc... where is the difference between a good restoration and a "good" modern tube amp. Again I'm talking about a good modern amp with good iron
Follow Ups:
I don't know the answer to your question but I'm about to find out.
I'm in the process of gutting an Eico-60 and replacing everything. Silver wire, new input/output silver jacks, modern caps, resisters, tube sockets, etc...
I am keeping about 90% of the original circuit. I would love to compare it to other HF-60 mods. I live in north Atlanta if anyone wants to have some fun.
Hi Lokie,
Your idea is refreshing and a great answer to Airtimes question. Count me in on what you find out, hear, improve, or blow up. It would be a perfect (tutorial) if you log it in Cap'n. If not I'd still love to hear your progress as it will improve my odds at success when I finally get to my dream projects in my , not proud of this, tube stash.....sincerely Mark Korda
There are probably a lot of different perspectives on this. I found the vintage amplifiers I tried each had their own sound. So you find one you like with your other components, you don't want to lose that sound, but you do want to make it more reliable and possibly improve specific characteristics. Others covered this, stiffen the power supply, replace out of spec components, low noise rectifiers, similar type but better coupling caps, sometimes bypassed, tube rolling...
I had a couple of eye opening experiences. One was on a cd player, not an amplifier. A friend and I both bought the same model, I put in better DAC's, coupling caps and a completely different low noise power supply. The sound was cleaner, and improved dynamics. My friend prefered the stock one, to his ears more musical.
With amplifiers, when I could I kept stock, and modified so I could compare them. Coupling caps were the biggest challenge. I would let them play a week or so, then compare them. I thought I had made good choices. There were some cases when I comapred them 6 months or so later, and my impressions at times were significantly different. And in all cases the same source, preamp and speakers was an absolute requirement.
So I guess my conclusion is that I'm not after necessarily a cleaner, more accurate amplification, but a sound I like and was synergistic with the other system components.
A side note, I have always wondered what amplifier manufacturers use as their reference speakers. And how much that impacts the amplfiers they produce.
1- First focus is installing good sounding audio coupling caps.
2- Next are using best sounding tubes.
3- Finally, a well filtered power supply. Also, a solid-state rectifier is used, remove the 1N4007s or similar voltage rectifiers and install low noise UF4007.
A funny thing. I used to restore Fisher 400, 500 & 800. (I have one more left to restore, but only rebuilt one this year).
The big guys, that is, well known rebuilders paid no attention to my list above. They build reliable units, but they did not sound good. The power supplies from these rebuilders had 25 volts ripple to the power tubes and no poly type cap filter on the voltage doubler output. What a crime just for starters.
And, they think they have a premium rebuild- how disgusting. They did everything to knock down my rebuilds including getting me kicked off of Audiokarma. I was taking a huge share of their work. AA is at least 15 years ahead of Audiokarma design wise anyways. I work as a GM Rep now.
hey Sony. I remember reading your posts a lot over at Audiokarma and really enjoying/learning from them. I also learned a lot working on two fishers. Probably more than other things due to them being a bit picky about what used where. It seemed pretty easy to loose the magic. Getting the output coupling caps right was very hard. I ended up using Mylar film and foils. I have a little x-100-3 that I have to get right.
Anyway, where would you put the poly cap in the power supply and what value? I assume from the output of the voltage doubler to ground.
Thanks.
10uF on the power supply output.
Thank you. I'll give it a go.
As for me, I want the closest replication for live, unamplified music regardless of the age of the amplifier.
Modern designs typically offer balanced operation for a lower noise floor, more linear coupling capacitors and far stiffer power supplies for improved resolution and dynamic punch.
Your call.
I'm not a engineer so redoing the whole circuit isn't really realistic. I really just want to make it reliable and renewed for trouble free operation for years to come. I'll borrow some tricks such as upgrading certain part quality or doubling the power supply capacitance. Sometimes someone will put a fix out for a flaw that I'll implement like correcting a riaa curve etc that I'll also use.
"Let's say you are restoring and upgrading a tube amp. Is your goal to make it sound a clean as possible. By that I mean balanced, no distortion, new parts and a razor sharp square wave."
IMHO the entire audio chain should be concerned with reproducing what went into it. By this I mean we should be able to record what we play, play that recording back and record it again.....repeat process over and over...and have it sound the same, and look the same on a scope, after several generations. So I vote for clean. BTW, the limiting factor is typically the speakers.
"With all things being equal like iron, tubes, etc... where is the difference between a good restoration and a "good" modern tube amp. Again I'm talking about a good modern amp with good iron."
I think it is hard to have a level playing field. How do you compare western electric to any present day offering? That WE amp was never sold, only leased. WE invented the high vacuum tube and loudspeakers. It was an engineered "package" and top quality, relibility, and long life were goals.....not cost or looks. They made and controlled all aspects and never had to worry about sales and cost. There just isn't anything close. And yes, I would put up one of their complete sound systems from the early 1900's against anything made in any time period (might even say the same about early RCA).
Now if we move forward, to say the 60's and later, matters are quite different. IMHO these tube amps all suffered from the same basic problem....how to get as many watts as possible from as small/pretty a package as possible. If one has a different design goal they can all be easily bettered (with perhaps a few exceptions). New amps are forced to use current production tubes which limits things a lot. I also doubt transformer design is quite the art it once was. Many parts are loads better though and circuit design has evolved. We can also use solid stae parts.
Now I would like to ask you something. What would it take for you to consider building your own amp from scratch? A regulated power supply....CCS loads for the tubes....a fairly simple circuit with limited distributed/local feedback loops....well, I think you would ditch your lust for vintage in a hurry (in all fairness there are a few vintage amps that are of great design and somewhat beyond a home builders prowess).
Hi Airtime,
That last thing Russ said is so true about losing your lust for vintage when building your own amp. I saw on Ebay a simple basic looking box preamp that clones the Marantz 7 preamp circuits and is also trimmed down a bit of controls. The kit is from China but uses the best connectors,caps, resistors, ect. and it costs 125 bucks. In a blind test it might beat the Marantz.
I think you already know your own answer and it might be with transformers which I heard is your expertise Charles. Before the internet there was Audiomart for vintage nuts looking for equipment, remember Airtime? The guy who ran it, Walt Bender wrote this statement in a copy of Listener mag. in an article about the Dyna ST-70 by Peter Brueniger...let me go find it......Walt said that transformers take up to 3 to 6 months to come up to 80 % and but take over 40 years to come up to the remaining 20%. This explains the stratospheric prices paid for Western Electric gear. It's not for the collectability but for the sound. That was Sept/Oct. 2001, Listener mag.
I don't know whats true but I'm just writing the quote down.
Airtime, Prima Luna has a great new ad in Absolute Sound and it's more of a tutorial on their point to point wiring being superior to tube circuit boards ect...that might be an answer to your question also....hey......have you seen any scorpions or rattlers out there yet?....take care...Mark Korda
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