• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Schematic with ECC88

Hi. I'll have to disagree with you here: this has got to be the poorest schematic that our friend Gost22 has ever come up with... :D

Hmm. wasnt it just a two stage ckt with current feedback? I didnt look too closely, but didnt seem like a bad starting point. I was sceptical to the grid leak bias of stage 2, but apparently many people like that, so I didnt bother bring it up. I always figure people will experiment and tweak the initial designs anyways. So to me it looked like something to try.
 
It was pointless WITH the subject as well. This poster has started thread after thread asking the same question. He has had numerous suggestions and apparently has tried none of them, but just opens yet another thread asking the same questions again.

The removed schematic was from an ethically-challenged Chinese vendor using a stolen trademark. It was pretty much the same as all the other Chinese vendor schematics that this member has posted before.
 

Shoog

Member
2002-08-15 10:16 pm
Eire
The X10D as produced by Musical Fidelity is benign and does what it claims it does when used between a CD player and a Preamp. I had one for quite some years and was never disappointed with it until I changed out the stock 6922 for some NOS Mullard ECC88's. This caused the sound to go very syrupy and I sold it soon after.

It seems that this circuit is very finely tuned to one particular brand of valve which means that attempting to duplicate it with "premium" valves may end up disappointing.

Shoog
 
I don't know why they delete schematics. 99.9% of these designs are over 80 years old. And revamping the design with semiconductors doesn't make it original either. nor littering the design with extra components.


anyways, to get back on subject. I would try the newest name for the self current regulator amp ( the AKIDO ) as a preamp. The reason why the semiconductor css ( which is nothing more than substituting a tube for a semiconductor device ) is popular is it does fix some issues with bad designs however, the semiconductor based css has a tendency to color the audio by making it dry and edgy.

The audio still works into the css regardless what other people say.
 

Shoog

Member
2002-08-15 10:16 pm
Eire
I don't know why they delete schematics. 99.9% of these designs are over 80 years old. And revamping the design with semiconductors doesn't make it original either. nor littering the design with extra components.


anyways, to get back on subject. I would try the newest name for the self current regulator amp ( the AKIDO ) as a preamp. The reason why the semiconductor css ( which is nothing more than substituting a tube for a semiconductor device ) is popular is it does fix some issues with bad designs however, the semiconductor based css has a tendency to color the audio by making it dry and edgy.

The audio still works into the css regardless what other people say.

That was suggested to the poster about 6months ago - he ignored that advice along with every other piece of good advice in favour of the medicro ideas he has chosen to share with us. Hence the fustration of all the seasoned members here.

Shoog
 
The X10D as produced by Musical Fidelity is benign and does what it claims it does when used between a CD player and a Preamp. I had one for quite some years and was never disappointed with it until I changed out the stock 6922 for some NOS Mullard ECC88's. This caused the sound to go very syrupy and I sold it soon after.

It seems that this circuit is very finely tuned to one particular brand of valve which means that attempting to duplicate it with "premium" valves may end up disappointing.

Shoog
Hi Shoog!
Is this preamp (see schematic) works well with tube/valve 6n1p-EV (Russian military), because I have these two pieces.
Cheers!:cheers:
 
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So we shall not know ..... but I was far too absent here too often, so never mind!

I read something about grid leak bias, and am going to risk giving unrequested and perhaps well-known advice. But for those who do not know:

Grid auto-bias (e.g. an 8,2 - 15 megohm grid resistor and cathode grounded) is conditionally in order. It must be fed from a low impedance source otherwise distortion is markedly higher than with cathode bias. (Tube data sheets confirm this.) That is because the grid actually draws current to bias it, though minute. That 'generates' a non-linear grid input impedance which needs to be swamped by a feeding impedance of no more than preferably < 1k.ohm. Okay, that is a very general rule, but it is typically used with tubes requiring a small grid bias voltage (say 12AX7 and sharp cut-off pentodes like EF86 etc.) For ECC88? Mmmmm - on the border!

End of tutorial .... but I have seen it used with tubes and under conditions not optimal for it. With modern low-voltage electrolytic capacitors being of small physical size, cathode resistors can be bypassed with high value caps, eliminating fear of hum etc. Those privileged to own a spectrum analyser can test.
 
Hi,
This is, in the found good schematic of Aikido cathode follower. Now I need a PCB for the schemeatic.
thank you
 

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