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12bh7 for a 12au7 - Page 3

post #31 of 37
Thread Starter 
The 580's sound pretty good on some tracks but I am going to take them out and give it a try. I don't know if it is me or not but it seems that my 225's are more sensitive to tuberolling than the 580's. Also, the 580's seem to have a steely sound to them compared to my 225's. My 225's sound more warm I guess you could say.I noticed this with an RFT tube I am using at the moment.
post #32 of 37
The type of resistors can make a difference, too. I normally stick with the V-D's everywhere, but they don't sound good on the output positions. I've got some 100 ohm carbon Stackpole's from Handmade and they sound really great with both my HD580's and my SR80's - K81DJ's, too. The highs are detailed, but "sweet." (Bass is always a constant with this thing.)

Blooze has always said this (he used Kiwame's), but the solid-state guys use the V-D's so much I thought they were OK - not so in comparison.
post #33 of 37
Thread Starter 
Ya, I got some stackpoles (I think) from handmade. I will have to try those.
post #34 of 37
Thread Starter 
You are right. I just put some stackpole 100 ohms in and it does sound warmer.
post #35 of 37

Hello !

i am very interested in this SOHA amp discussion

I have some question

I think this is the schematic

 

 

The questions are:

1)  could you tell me the voltage gain of the circuit ?

2)  any idea of the output impedance at the tube output

3)  for the 3D Starter.  have you tried the 12bh7 in the end ?  Personally i think that this tube is indeed a great tube. Much more robust than the 12au7.  This tube is usually found as driver in many high end tube amps.

 

Any other suggestion of similar hybrid headphone amps would be very welcome and much appreciated.

 

Thank you very much indeed

Kind regards,

gino

post #36 of 37
Quote:
Originally Posted by ginetto61 View Post

Hello !

i am very interested in this SOHA amp discussion

I have some question

I think this is the schematic

 

 

The questions are:

1)  could you tell me the voltage gain of the circuit ?

2)  any idea of the output impedance at the tube output

3)  for the 3D Starter.  have you tried the 12bh7 in the end ?  Personally i think that this tube is indeed a great tube. Much more robust than the 12au7.  This tube is usually found as driver in many high end tube amps.

 

Any other suggestion of similar hybrid headphone amps would be very welcome and much appreciated.

 

Thank you very much indeed

Kind regards,

gino

I built about 4 or 5 of these in various forms when it was first popular.  I can answer a couple of the questions:

1. Actual gain is somewhat less that the tube amplification factor, but that's about 19, which is very significant.  The design called for very large output resistors in an effort to control that kind of gain.

2. As mentioned above, the output resistors were so large, they pretty much over-rode any other impedances.  If you notice in the schematic you posted above, "RH" is 100-150 ohms.  Those are the output resistors.

3. Can't answer this one.

 

As for similar hybrids, they are numerous - Millett Hybrid, MAX, MiniMAX, Starving Student, SOHA II, EHHA, CTH, etc., etc.  Although the SOHA II is a direct descendent, my guess is that many would say the CTH probably meets the original SOHA intent as a very compact, hybrid implementation of the 12AU7.

post #37 of 37

Thank you very much indeed for your kind and valuable reply

As you can very easily understand i am a beginner

The gain is really too high.  I am looking for a low voltage gain amp that can double as a line preamp

A gain up to 4-5 would be also acceptable because my amp as an attenuator at the input

I like the idea of a tube in the signal path to give a more spacious and "musical" sound

Thanks a lot again

Kind regards,

gino

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