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SRPP question

Hello, guys. This is mi second thread in this area.
Despite of I´m electronic engineer, I don´t have any experience in tubes design. I have couple of ECC88 (6DJ8), 12AX7, 12AT7,ECC80 an EL34. I´ve been reading a lot about SRPP (mainly from www.tubecad.com) and presently I´m a little confused. I want to build a pre amplifier for CD/DVD/Tape and, in the future, phono too.
Which configuration do you recomended for a beginner?? SRPP of CF??
I now there are a lot of things involves here, like Zout/Zin/Gain, etc... but I´m interested in the quality of sound, ´cause there are detractors in both sides and mainly in your owns experiences.
Any advice and comment It will be appreciated.
Thanks you.


2002-06-06 4:43 am

The SRPP stage is very useful especially because it has a low output impedance and better gain than the standard stage. For use as a DAC buffer I think it is very good. I have not measured its noise performance but it certainly has better distortion figures. I will check this out again and post some data.
The SRPP is not hard to use even in a phono stage. Note that you can also use a transistor in place of the resistor above the bottom tube. Tube Cad has the details. This is trickier than the plain resistor but performs better.
You can do something as simple as using a 12AX7 hooked as follows. RCA plug to potentiometer to one side of tube, twice, for stereo. If you are using it for low level with high efficiency drivers a single 12AX7 can run a stereo SE amp, all on the same chassis. The SRPP has you runing the signal through one side then the next so then you would use 2 tubes intead of one. So if you are single ended you now have 4 tubes, not counting the rectifier. SRPP does have quite a bit going on in a small place so a recommendation is to use an octal based dual triode like a 6SL7 as you have about triple the space in the socket area to work in. This is like building a ship in a bottle, lots of things in a small space that is hard to move around in. Have fun and use the right tools.
Thanks for your answers.
The amount of tubes It´s not a problem. When I said "a couple", I wasn´t clear. The true It´s that I have almost 20 12AT7, 24 12AX7, and 15 ECC88 (6DJ8), 10 ECC80 and 5 EL34. I have others, that I think there aren´t suitable for audio: 7 6F6GT and 4 6AV6.
Imagine that with this amount of tubes I can build a lot of pre amplifiers, and in several configurations... I think that I´ll start with SRPP. For this I started this thread,´cause I´m not sure about the quality of sound that I can achieve with this configuration.
At the moment I´ve been looking for alternatives to the PSU. First I thought in TL783 from Texas, but presently I´m decided in using LM317T.
Thanks for your answers.