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Audion Edison 60 building and using report
Audion Edison 60 building and using report
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Old 17th January 2020, 01:42 PM   #51
baudouin0 is offline baudouin0
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Basically this amp sounds so good as it is that I'm not interested in changing anything. I'm now using it with Gold Lion KT77s, they are certainly better than the original Electroharmonix EL34 (especially in the bass). My intention was to erase this thread altogether after the bashing from people who never post any builds of themselves happened, but as that wasn't possible it's still here for all to enjoy.
I'm not sure what "Is it a good candidate for 2020" means? You can get an extraordinary good kit, with some esoteric parts if that's your hobby, for not too much money, that sounds just as good in 2020 as it did in 2017 (in my case).
Its disappointing when that happens. If you put your amp on display and ask for comments that what you got! Many of them are good suggestions which others have spent time on. I find it better to ask a question when you have an issue. The ringing on the square wave I would look into. I have built both SS and valve amps from scratch.
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Old 21st January 2020, 04:56 PM   #52
OldHector is online now OldHector
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Originally Posted by OldHector View Post
I have read through this thread, and it seemed like fb2017 got a bit of a raw deal at the start, since there were some quite negative comments about the topology of the design.

I'm still finding my way with tube circuits, and I was struggling to make sense of the design. The part I was confused over were the cathode coupled driver tubes, ringed in yellow below.

The circuit reminded me of the GEC 50W amplifier, and examining that more closely I think it is identical. So then I looked at the write up of the GEC amp on The Valve Museum, and I have saved an expert's response here, because now I can see the justification for the topology.

From the valve museum ...
The use of a push-pull pair of triodes for the driver stage was chosen so that the output stage would be symmetrically driven, and that no unbalanced operation would occur even at the onset of grid current in the output valves during overload. The removal of the phase splitter to an earlier stage ensures that the time constants in the grid circuits of the output valves are the same. The B329 is used in this stage because it has a low anode impedance, about 10,000 Ohms. With this low value of driver impedance the phase shift due to the input capacity of the output stage is relegated to frequencies above 50 kHz, and this, combined with the symmetry of the circuit, greatly assists in ensuring freedom from HF instability when feedback is applied overall.
Design for a 50 Watt Amplifier

The article does suggest that there should be some mechanism to balance the driver stage, for the best hifi solution.

The phase splitter is a floating paraphase, and that got a lot of abuse at the start of this thread as being 'old fashioned', but it is just another way to skin a cat, isn't it?

Is the Edison 60 a sound schematic, that is a good build candidate for 2020? Or is the design dated because it is tackling the problem in an archaic way, and hence it is not a good solution? Could it be that the design is good, but more suited to tubes that are hard to drive?
Just bumping my post #49 above. I had no replies.

The original poster got quite a lot of grief for the schematic of this kit, with the implication it was a primitive design, and not worthy of being built today.

The schema is basically the same as the GEC 50W amplifier, and gets discussed alongside other classic designs.

I'm starting to think about my next build, which will be a classic design, and since I have a pair of OPTs from the same kit, I was considering this design as a starting point. Another option is the Brimar 25P1 (simpler design with pentode gain, double triode LTP phase splitter, KT66 equivalents output).

I have an old PA case from the 50's, with a nice cage. Chassis size is 21cm x 42cm.
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Old 22nd January 2020, 04:25 AM   #53
fb2017 is offline fb2017
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If your question is about the OPTs, obviously the Silver Night ones are of extremely high quality, probably the best in class. And I can tell you, the OPTs are defining 90% of your sound.
I would like to suggest you to build the SE variant of the kit I have, if you want to experiment with SE. Otherwise just buy the kit and build the push-pull Class A amp I have.
If you worry about the sound quality - in the dual monoblock variant I have made (fully separated power sources), and with the Dallas II horns, it gives me plenty of jawdropping moments. Recently I am listening to a lot of classic (think YoYoMa's recent high resolution recordings of Bach's cello suites, or Mozart concerts for strings or wind instruments. Another album that impressed me was Taylor Swift's Reputation - the bass is extremely tight and well defined. I'm not sure how some people can think they have the right of an opinion on this schematic without hearing the actual amp at work, so that's that... Like I said, the 50W Silver Night OPTs will absolutely define your sound.
Quote:
Originally Posted by OldHector View Post
Just bumping my post #49 above. I had no replies.

The original poster got quite a lot of grief for the schematic of this kit, with the implication it was a primitive design, and not worthy of being built today.

The schema is basically the same as the GEC 50W amplifier, and gets discussed alongside other classic designs.

I'm starting to think about my next build, which will be a classic design, and since I have a pair of OPTs from the same kit, I was considering this design as a starting point. Another option is the Brimar 25P1 (simpler design with pentode gain, double triode LTP phase splitter, KT66 equivalents output).

I have an old PA case from the 50's, with a nice cage. Chassis size is 21cm x 42cm.
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Old 22nd January 2020, 11:35 PM   #54
andersss2013 is offline andersss2013
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It makes me happy to read your build report about the amplifier and I have a small story about it. This was my first build many, many!, years ago. By a chance I happen to meet the designer who happen to live in southern part of Stockholm (still does) at the time. His name is found on the schematics, Erik Andersson, famous for other amplifier designs as well. He worked together with David Chessel and designed the Audion at the time. Anyhow I met him at my work and we started talking about his affection for motorcycle and he told me he was working with tube amplifiers and had a small workshop in his home. He invited me to his home and demonstrated this amplifier and I was so impressed that I bought a kit directly from him. Ended up making a misstake because i misunderstood something in the schematic and had to pay him a visit to get it fixt but after that the amplifier sounded amazing and I used it for many years. I returned to Erik many times and bought also other kits from him, the 300B and so on. I have a deep respect for Erik and his designs and perhaps mostly because of the amazing sound from a relatively simple looking design. I have built many amplifiers since then but I'm not a superexpert but do not think it is outdated. I much regret that I sold my Edisson 60 and would love to build one again. The fact that it is still available speaks for itself. Also interesting that you now run kt77 instead of the EL34. Thanks for your original post!
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Old Yesterday, 04:36 AM   #55
PRR is offline PRR  United States
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> What is this stage doing?

It's a gain stage. We have a beastly Power Stage, a delicate Input/NFB Stage, and for these tube types we really want one more stage.

> bumping my post #49 above. I had no replies.

I thought you replied-yourself admirably.

Paraphase gets no respect because it is out of fashion. Engineering is NOT pure logic. Designers go with what tickles their fancy. NON-designers echo garbles of what they think they read/heard somewhere.

Considering the expected imperfect balance across the output pair(s), I would not fret about driver balance. I have had totally-trimmable amplifiers and did not think they sounded better than amps built with 20% tube and 5% resistor tolerance.
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Old Yesterday, 08:36 AM   #56
fb2017 is offline fb2017
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Originally Posted by PRR View Post

Considering the expected imperfect balance across the output pair(s), I would not fret about driver balance.
Do you refer here to the Auto-Bias?
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Old Yesterday, 08:52 AM   #57
OldHector is online now OldHector
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If you check out the article on The Valve Museum, linked to my earlier post, they have a discussion around adding a balancing circuit to balance the signal received at the output valves, to compensate for variations in the phase splitter and parallel gain stage.
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Old Yesterday, 01:23 PM   #58
fb2017 is offline fb2017
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Originally Posted by andersss2013 View Post
Also interesting that you now run kt77 instead of the EL34. Thanks for your original post!
You're welcome! Your story is also very interesting, I would have loved to meet the designer as well. Indeed, the KT77 is a drop in replacement for the EL34 in this amp, and they work perfectly. Due to its conversion to 100V, the bias and maximum power output is slightly lower now on mine, but that hasn't affected the quality a bit...
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