Simple tube preamp...

chrille · 18th February 2003, 01:50 PM

I am looking for a very simple but good tube preamp. If possible, with only one tube per channel. No output transformer.
I would be happy if the preamp could be used as a headphone amp too.

fdegrove · 18th February 2003, 03:10 PM

Hi,

You can have a look at this one for instance:

JOEL'S ALL PURPOSE PREAMP

Cheers,

chrille · 18th February 2003, 04:43 PM

Maybe this one will work?
Anyone having some PSU recommendations?

http://hjem.get2net.dk/aaholm_audio/schems/6dj8_1.htm

Brett · 18th February 2003, 05:16 PM

Quote:

Originally posted by chrille
Maybe this one will work?http://hjem.get2net.dk/aaholm_audio/schems/6dj8_1.htm

Nope. If you want a line pre as well as a headphone amp, that one won't work. It's output Z = 4k8 and gain (into a high Z load) will be about 20. Probably fine as a line amp on it's own, though it wouldn't be my first choice. A headphone amp requires quite a lot of drive capability into low impedance loads. A single tube, without a transformer is too big an ask, esp if you want to drive something like Grado's (32 ohms?), and presumably want to have some gain in the stage.

Joel's schem Frank linked above would be better than the one you linked.

fdegrove · 18th February 2003, 05:46 PM

Hi,

Quote:

If possible, with only one tube per channel

That is certainly possible.
The drawback is that you will have to use octal or novar types of dissimilar triodes such as a 6EW7,6GF7 etc.

One of the triodes can be used for voltage amplification and the other as the poweramp part.

If you need to keep things small then there is this one :

http://www.diyaudio.com/forums/showthread.php?s=&threadid=10984

Cheers,

Brett · 18th February 2003, 06:14 PM

Frank,

You're right. I was thinking of a single triode/pentode per channel, not a dual in a single envelope. At a glance, the 6EW7 looks like a good possibility for a setup similar to Joels, ie CC->CF. Or what about a 6080 / 6AS7 SRPP? :-)

Cheers

chrille · 18th February 2003, 08:21 PM

I think I give this circuit a trie
(I can build a headphone amp separate instead)

http://hjem.get2net.dk/aaholm_audio/schems/6dj8_1.htm

Its cheap and very very simple... perfect for a tube beginner like me.

BUT I dont know which PSU I am going to use?

Sch3mat1c · 18th February 2003, 09:09 PM

Years ago I made a little preamp...I call it my Experimenting Chassis because I have B+, heater and ground wires lead out externally for the breadboard...

Drives a 5k load fine...not too much gain overall though, not with the tone circuits in.

BTW if anyone was curious about the tone circuit in my 6L6GC SE amp, this is where I developed it.

Mods I recommend:
- Increased coupling caps.
- Seperate cathode bias, and more bias (1k per cathode), likewise smaller plate resistors (circa 100k).
- Higher voltage - a single, purpose-built transformer would function better than the current arrangement. If nothing else, a larger 2nd transformer and a voltage doubler.

DC filaments if you feel adventurous...maybe a cathode follower output instead...

Tim

fdegrove · 18th February 2003, 09:44 PM

Hi Brett,

Quote:

Or what about a 6080 / 6AS7 SRPP? :-)

A Sovtek 6AS7G could do, the others may cause trouble with cathode bias...

Either way, it won't have much gain to play with.

Cheers,

P.S. You are aware that most people want to burn off lots of gain,aren't you?

18th February 2003, 01:50 PM	#1
chrille diyAudio Member Join Date: Jul 2002 Location: sweden	Simple tube preamp... I am looking for a very simple but good tube preamp. If possible, with only one tube per channel. No output transformer. I would be happy if the preamp could be used as a headphone amp too.

18th February 2003, 03:10 PM	#2
fdegrove diyAudio Senior Member Join Date: Aug 2002 Location: Belgium	PREAMP. Hi, You can have a look at this one for instance: JOEL'S ALL PURPOSE PREAMP Cheers, __________________ Frank

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18th February 2003, 04:43 PM	#3
chrille diyAudio Member Join Date: Jul 2002 Location: sweden	Maybe this one will work? Anyone having some PSU recommendations? http://hjem.get2net.dk/aaholm_audio/schems/6dj8_1.htm

18th February 2003, 06:14 PM	#6
Brett diyAudio Member Join Date: Jan 2002	Frank, You're right. I was thinking of a single triode/pentode per channel, not a dual in a single envelope. At a glance, the 6EW7 looks like a good possibility for a setup similar to Joels, ie CC->CF. Or what about a 6080 / 6AS7 SRPP? :-) Cheers

18th February 2003, 08:21 PM	#7
chrille diyAudio Member Join Date: Jul 2002 Location: sweden	I think I give this circuit a trie (I can build a headphone amp separate instead) http://hjem.get2net.dk/aaholm_audio/schems/6dj8_1.htm Its cheap and very very simple... perfect for a tube beginner like me. BUT I dont know which PSU I am going to use?