tube/SS hybrid (low power)- need tube help

trespasser_guy · 26th June 2003, 08:17 PM

Hi all. I attached the schem of a tube/SS amp I have been working on. It would be used for headphones... I just want some comments from tube-minded folks.

Values:

C1- 1uF
C2- 4.7uF
P1- 100k
Q1, Q2- 2N5484
R1- 1M
R2- 330
R3- 200k
R4- 100
R5- 820
R6- 1k
R7- 1k
R8- 200k
R9- 1k
R10- 18k
R11- 1k
R12- 100
R13- 10

gain of opamp=10... biased into "class a", and all that stuff. I understand that... just wonder about the tube section. Opamps will run on either +/-12V or +/-15V... lost my good tranny so I may have to settle for 12V.

The tube will be run at +/-42V, probably. Does everything look ok?

How do you think it would sound? I haven't really heard many good things about tube/SS hybrids, but some peopl use them... so I thought I'd check them out. Thanks

analog_sa · 26th June 2003, 08:26 PM

But what's the purpose of the valve? It's clearly redundant in this circuit. It would probably have some justification if you had a valve amplification stage followed by a buffer to match the load, but as shown it only adds noise and distortion. This is not what valves are meant to do.

SY · 26th June 2003, 08:35 PM

And why use a bipolar supply if both the tube input and output are capacitively coupled? If you wanted to use a much simpler single-ened supply, the redundant R1 can be snipped out.

trespasser_guy · 26th June 2003, 08:58 PM

The tube is just supposed to put in its 'tube sound' and not do much else- add a tiny amount of gain. How bad of distortion? Hmm...

SY · 26th June 2003, 09:04 PM

Quote:

add a tiny amount of gain.

I doubt that. It's a cathode follower.

zobsky · 26th June 2003, 09:56 PM

i'm interested in this too, kinda ....

suppposed i wanted to use a tube pre-amp with a solid state power amp i have to inject some "tube flava", would i not use something like trespasser_guy, ..except maybe tap off with a bypass cap at the anode, as opposed to the cathode?

i already did this when testing the pre-amp section of a simple 6bq5 triode strapped amp i built last week. ..but is this the correct way to do this

questions from a newbie

fdegrove · 26th June 2003, 10:21 PM

Hi,

Quote:

i'm interested in this too, kinda ....

One word: forget.

Cheers,

trespasser_guy · 26th June 2003, 11:02 PM

So, more or less, there really is no way to implement it and achieve a suitable result?

zobsky · 26th June 2003, 11:07 PM

well for headphones only / preamp use, there are several excellent tube-only designs. headwize has some good info

trespasser_guy · 27th June 2003, 12:01 AM

Yes... but they all cost a fortune... if done right. And, this way, I would be able to build something I know how to build (the SS part) so in the event that the tube thing didn't work out, I still had a good SS headphone amp. Plus, I'd get to use up my OPA637s and BUFs. I would love an all tube, and was about to order the parts a few days ago... but talked myself out of it because I have never done it before, and the amount of money I'd sink in it is a lot to lose...

26th June 2003, 08:35 PM	#3
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	And why use a bipolar supply if both the tube input and output are capacitively coupled? If you wanted to use a much simpler single-ened supply, the redundant R1 can be snipped out. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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26th June 2003, 08:26 PM	#2
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	But what's the purpose of the valve? It's clearly redundant in this circuit. It would probably have some justification if you had a valve amplification stage followed by a buffer to match the load, but as shown it only adds noise and distortion. This is not what valves are meant to do.

26th June 2003, 08:58 PM	#4
trespasser_guy diyAudio Member Join Date: Aug 2002 Location: USA	The tube is just supposed to put in its 'tube sound' and not do much else- add a tiny amount of gain. How bad of distortion? Hmm...

26th June 2003, 09:56 PM	#6
zobsky diyAudio Member Join Date: Mar 2002 Location: Dallas, Tx, USA	i'm interested in this too, kinda .... suppposed i wanted to use a tube pre-amp with a solid state power amp i have to inject some "tube flava", would i not use something like trespasser_guy, ..except maybe tap off with a bypass cap at the anode, as opposed to the cathode? i already did this when testing the pre-amp section of a simple 6bq5 triode strapped amp i built last week. ..but is this the correct way to do this questions from a newbie

26th June 2003, 11:02 PM	#8
trespasser_guy diyAudio Member Join Date: Aug 2002 Location: USA	So, more or less, there really is no way to implement it and achieve a suitable result?

26th June 2003, 11:07 PM	#9
zobsky diyAudio Member Join Date: Mar 2002 Location: Dallas, Tx, USA	well for headphones only / preamp use, there are several excellent tube-only designs. headwize has some good info

27th June 2003, 12:01 AM	#10
trespasser_guy diyAudio Member Join Date: Aug 2002 Location: USA	Yes... but they all cost a fortune... if done right. And, this way, I would be able to build something I know how to build (the SS part) so in the event that the tube thing didn't work out, I still had a good SS headphone amp. Plus, I'd get to use up my OPA637s and BUFs. I would love an all tube, and was about to order the parts a few days ago... but talked myself out of it because I have never done it before, and the amount of money I'd sink in it is a lot to lose...

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