Comments on: Mullard 520 Power Amplifier c.1956

By: BCNZ

BCNZ — Sat, 26 Oct 2024 09:56:12 +0000

I’m a bit late to the party but try this link if you don’t already have the PDF:

https://www.worldradiohistory.com/BOOKSHELF-ARH/Circuits-For-Audio-Amplifiers-Mullard-1963%20.pdf

By: David Douglas

David Douglas — Sun, 20 Mar 2022 09:36:37 +0000

HI what can I say we brits Do what we Do best this is where we excell in valve amp Design others make great amps as well but it.s mullard who started it went from there there are also great transistor amps eg leak armstrong quad etc very sought after still around the world need I say more .Happy building David Douglas

By: Trevor Gale (Electronics Design, Space)

Trevor Gale (Electronics Design, Space) — Sat, 22 May 2021 00:29:37 +0000

In reply to Kurt Lilienthal Steffensen.

The ECC83 in the design above is NOT ‘paralleled’, the first (left) triode grid is fed with the audio signal (and bias) from the EF86 and outputs at its anode the drive for the first (upper) EL34 output valve.
The second (right) triode of the ECC83 receives only the bias D.C. voltage from the EF86 anode – as it is decoupled at audio by the capacitor to ground; this triode acts as a phase splitter as it’s in common-cathode connection so outputs at its anode the drive in opposite phase to the second (bottom) EL34 output valve. That way the pair of output valves (EL34’s) operate in push-pull into the output transformer, properly balanced.

By: Xiangui Liu

Xiangui Liu — Thu, 25 Feb 2021 11:53:26 +0000

I am looking for the Armstrong A 10 MKII Amplifier ‘s schematic, Can anyone offer?
Thank you!
Please contact me liuxiangui@126.com.

By: Jerry B. Williams

Jerry B. Williams — Wed, 28 Aug 2019 15:25:42 +0000

In reply to Steve Calver.

Steve:

It’s probably just me, but…..when I had “Copied & Pasted” the URL link you have provided to download the “MULLARD Circuits for Audio Amplifiers.pdf”, I received the following error message:

404
The page you requested was not found.

Do you have anything more recent and/or updated? THANKS!!

JBWilliams

By: Benjamin Digo

Benjamin Digo — Fri, 16 Aug 2019 10:18:17 +0000

R9 should be 82,000 ohms, not 8,200 ohms.

By: barbaro francisco

barbaro francisco — Sat, 26 Dec 2015 15:04:43 +0000

ola econstruido infinidad amp valvulares tengo experiencia en puss phull ultra lineal ytriodos varios desde 2a3 a6550 tambien en sigle ended mi experiencia me dice que el mejor circuito es el mullard pero tiene muchas variantes no todas suenan bien lo mejor esde entrada una 5751 sonido sedoso lo mejor como divisor defase 6sn7 desalida desde 2a3 6b4 el34 6l6 6550 en cneccion triodo ojo respetar tenciones y cargas el punto clave es el inversor alimentarlo con 430 v tension de rejilla 11o 115 v seria muy largo explicar mas detalles cualquier duda cnsultar

By: Steve Calver

Steve Calver — Wed, 22 Oct 2014 17:18:53 +0000

you can download a copy for free of the Mullard Circuits for Audio Amplifiers from here:
basaudio.net/blog/wp-content/uploads/2013/01/19400164-Mullard-Circuits-for-Audio-Amplifiers.pdf or 19400164-Mullard-Circuits-for-Audio-Amplifiers – BasAudio.Net

By: antonio carlos novelli

antonio carlos novelli — Sun, 20 Jan 2013 02:40:32 +0000

In reply to Kurt Lilienthal Steffensen. Com referência ao amplificador citado por mim, que usa um circuito Mullard 520 modificado, fiz um apdate, retirei as EL34, e substitui pelas 6550, troquei os transformadores de saída por outros de 60 watts, com uma carga de primário de 4K3! Com +B de 450volts. Acho que quase consegui alcançar o "santo gráu sônico" Obs: as vávulas de saídas, trabalham com fixed bias!

By: highburn

highburn — Thu, 10 Jan 2013 05:36:19 +0000

Those old Radio and Television News are more fun to read for the ads and the general flavor shown in articles, but there is still a great deal of interesting tech stuff and I’d love to be able to buy them as an e-book today. It would be vitally important to scan them so that the margins are not blurred, though.

In this circuit, the output transformer is going to be pretty critical and it’s interesting that it lists several commercial ones some of which I know to be quite different from each other. I really wonder if they built this amp and tried each of the recommended ones for stability with the component values listed.

Would I build one today? Hard to say. I think an all triode front end would be better, especially as the EF86 was a noisy tube as I recall. Are there some more common pentodes that would give the gain needed with less noise? I’ll look through my RCA Receiving Tube manuals for some ideas.