Marzio &Jelasi's Direct Coupled SE Amp

[oldeurope]

Hello,
I am searching for the schematic of Ciro Marzio & Christiano Jelasi's Direct Coupled SE Amp.

All I've found is this thread.

Thanks,
Darius

 

[Michael Koster]

Hi Darius,

It's in Sound Practices Vol. 2 issue 5.

Michael

 

[oldeurope]

Hi Darius,

It's in Sound Practices Vol. 2 issue 5.

Michael

Hi Michael,

schematic available?

thanks,
Darius

 

[Zen Mod]

Hi Michael,

schematic available?

thanks,
Darius

send me mail and I'll send you pdf of article

 

[oldeurope]

send me mail and I'll send you pdf of article

Done,
I am looking forward for the article. 🙂

BTW: Why not posting the schematic in the forum?
Since only members can see the attachments,
there isn't a copyright problem. 😕

 

[oldeurope]

Thanks 🙂

I thought there is something true in this post:
link

No Loftin White, please note C5 and ...

Kind regards,
Darius

 

[sgerus]

Here is another direct coupled 2A3 circuit

 

[diy4]

sgerus -
Do you know who the designer of that schematic is?
Appears to be French.
Where did you find it?
thx.

 

[Michael Koster]

#7

The designer of this well-known circuit is Isamu Asano.

http://www.eifl.co.jp/index/export/asano.html

Michael

 

[diy4]

Thanks. I knew I'd seen that somewhere before.

 

[oldeurope]

circuit design ...

Thanks. I knew I'd seen that somewhere before.

A well designed circuit has a closed output current loop and
no influence of the output current in the driving voltage.
E.g. the Western Electric (repeater amplifier)
http://www.nutshellhifi.com/library/Tube_Fest_Talk.html
You can see that most circuit makers don't care about this aspect, I do.
😉

Kind regards,
Darius

 

[Nikolas Ojala]

Thanks!

A well designed circuit has a closed output current loop and
no influence of the output current in the driving voltage.
E.g. the Western Electric (repeater amplifier)
http://www.nutshellhifi.com/library/Tube_Fest_Talk.html
You can see that most circuit makers don't care about this aspect, I do.
😉

Kind regards,
Darius

That was extremely interesting, especially the last example on the first page.

 

[sgerus]

Where did you find it?

http://www.bonavolta.ch/hobby/en/audio/audioel.htm
(Lots of good info here... look under amps, 2A3 se-pp)

The schematic I posted looks a lot like the Marzio & Jelasi schematic.... they both have the 2A3 cahtode bypass cap on the 2.5vac center tap, and they both use the "ultrapath" cap from b+ to the + side of the cathode bypass cap.

What am missing about this thread? Is the Marzio & Jelasi amp a Loftin-White amp?

 

[oldeurope]

...
What am missing about this thread? Is the Marzio & Jelasi amp a Loftin-White amp?

No, it is simply direct coupling.

 

[chrismercurio]

resurrecting an old thread

Can someone pm me the Sound Practices article? I have pm's enabled in my profile.

Thank you in advance,

chris

p.s. If no one has it, I will just buy the CD...and will anyway. I'm just impatient to read it.

 

[chrismercurio]

I found it here:

http://www.ispra.net/audio/DCSingleEndedAmplifier/index.php

Chris

 

[sgerus]

Chris,

If you’re thinking of building a direct coupled amp, you might want to take a look at the “DRD” design by Electra-Print

http://www.electra-print.com/2a3drd.php

The advantage of the DRD is that the input tube’s B++ comes from the cathode of the output tube…. So overall you use less current, and you burn less current with the cathode bypass resistor because about %25 of the current from the output tube goes to the input tube.

Another plus of the DRD design is that is that the grid of the output tube will always be at a lower voltage that the cathode…. Even if the input tube fails.
(That’s not the case with the loften-white)

I’m thinking of building a 2A3 DRD for my next amp…. Any input on the pros/cons of the DRD vs. Loften-White would be appreciated.

 

[chrismercurio]

I have looked at the DRD stuff at Electraprint. I decided against it as the PS is solid state. I still think Jack at Electraprint is a great source for iron though, and his prices for custom handbuilt is cost competitive with Hammond.

Best,

Chris

 

[chrismercurio]

Power Supply Question

In the attached schematic, the mains transformer is tapped at 410V and going into the mercury rectifier. If I used a mains transformer with a lower voltage and reduced the value of R1 such that the voltage after the choke input filter was the same as it was at 410V, does that work? I assume, (and I need to do some more reading), that the values in the choke filter need to be altered as well.

Thank you in advance for any and all help,

Chris

 

[analog_sa]

Re: Power Supply Question

reduced the value of R1

Dangerous. The 83 is designed to work with a choke input filter and i would imagine R1 is trying to look like a choke. Reduction may lead to fireworks.