• 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.

Inherited DIY Tube PreAmplifier

Hey all,

I recently got the chance to acquire a DIY Tube PreAmp for 300€, it was inherited to the person so they couldn’t tell me that much. I have also no clue when it comes to Tube Amplifier since this is my first one, so I’m curious if you guys can tell me some more about it, was it the money worth? what exactly is it, a rebuild? I know that it has 4 Line.Inputs + 1 Tape and a Phono (MM) Input.

Thank you in advance

8F723124-5F39-4F3B-B63E-D535F24AFDF6.jpeg
EB6655FE-366D-40DE-9520-D3B6C49EC450.png
37D767EE-7612-4DA6-BE0F-82515270B9CA.jpeg
56DAB641-C224-4518-BBA5-E45163A224D2.jpeg
88D424C7-3103-443D-BD2F-6B248BF7D41C.jpeg
 
This is a scratch build, but it's hard to tell whether it is a clone of some existing circuit, or something novel.
Maybe it has a passive line stage. Was there a schematic diagram with it? What are the tube types?
 
It's reasonably well-built with standard parts, has all point to point wiring, and seems to have separate volume controls
per channel. It could have been built almost any time since the stereo era began.
 
The filter capacitors are dated 6/1979; volume potentiometers are also from the '80s, maybe early '90s. It is not a professional build quality, components are soldered without consideration for future servicing, but it is a good DIY build. Due to the age, the small electrolytic capacitors may be degraded and should be checked. Filter capacitors may be still ok despite the age, but if the amplifier has not been used for decades, they also may be leaky. 300 euro for a unrestored DIY build of this kind is a lot of money, it may eventually be a fair price if the tubes are at 100% emission and sought after.