• 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.

looking for a pre-amp schematic

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Hi

I was thinking of building a class-D amplifier from a kit but i got chatting to a retired guy who used to play around with valve hi-fi back in the 1960s and he has convinced me to spend a bit more and build an all-tube system

however, I don't know where to look for schematics (or a kit would be even better) and i was hoping that there would be a thread on here with links to circuit diagrams or maybe a link to a site that has them

it would be for a phono pre-amp (to connect up to a Technics turntable with an Ortofon cartridge) with two stages of amplification - so i guess it would have 4 tubes (???)

and this leads me to my second (and probably stupid) question : why are there no knobs and other controls on the pre-amp projects in the photo gallery on here ?

I think i would want 3 source inputs (Phono, Tuner Aux), bass, midrange and treble controls, volume control, balance control, headphone jack ... and apparently it would also require internal filters to make the incoming phono signal more linear across the frequencies but i can't find any info about this

so - has anyone got any ideas about where i might find schematics for this kind of pre-amp ?
 
The reason you don't see tone controls is their negative impact on sound quality. Surprisingly few recordings benefit from tone control circuitry. Good tone control circuitry is not simple and should be completely defeatable.

Phono preamps are among the most difficult of projects to execute well. IMO, you would do well to tackle something else, 1st.

You said an all tubed system would be assembled. What sort of speakers are you planning on using?
 
Eli Duttman said:
The reason you don't see tone controls is their negative impact on sound quality. Surprisingly few recordings benefit from tone control circuitry. Good tone control circuitry is not simple and should be completely defeatable.


ok fair enough.

Phono preamps are among the most difficult of projects to execute well. IMO, you would do well to tackle something else, 1st.

so if i build just the power amp (which, I agree, seems a lot simpler to put together) what should i use to pre-amplify the phono signal ?


You said an all tubed system would be assembled. What sort of speakers are you planning on using?

I don't know yet - my existing speakers are so apallingly awful that I'm looking around for some decent second-hand ones
 
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