thanks for this bud! I can whip this up in one day on the bench, and it was most illuminating! And to think you were using about the most awful garbage turntable/cartridge you could find (not meant as an insult, this is a test setup I know)! lol... I have have quite a few new AX7's in the shop .... gonna do this, thanks for posting this! :)
very nice! it sounds very rich indeed, i am looking to build one also, however i am having trouble understanding how you have 2 channel in and out yet only one 12ax7? please explain as i am very novice in valves...
@preludefan The reason for that is that this was the only terminal jack board I had at the time! Two of the jacks are not used for this mono preamp. You will need 2 12AX7s for stereo.
@preludefan This is just a prototype to see if the circuit functions properly. I was planning to make a stereo version after this one, but never got around to it.
@JPa311979 Yes, the transformer is from AES but it produces quite a bit of hum. I wouldn't recommend it for this project. The rectifier is a regular full-wave bridge rectifier from RadioShack. I didn't feel like taking the time to draw diodes at angles with Paint.
That's a nice sounding pre-amp. The schematic is identical to one I found on the web several years ago except there was no power supply. It had the B+ at 250V so I used a voltage doubler from another circuit. Also, I had to make the filament voltage DC to get rid of the buzz.
@AllAmericanFiveRadio The ground is actually a bus wire connected to the chassis at a single point, so it's not really floating. Maybe I'll build a stereo one and build it into a source selector preamp. Then I could have a complete DIY stereo system with homemade preamp, power amp, radio, and cassette recorder :)
thanks for this bud! I can whip this up in one day on the bench, and it was most illuminating! And to think you were using about the most awful garbage turntable/cartridge you could find (not meant as an insult, this is a test setup I know)! lol... I have have quite a few new AX7's in the shop .... gonna do this, thanks for posting this! :)
googulisevilscum 2 weeks ago
good sound
MrXyloxylo 3 months ago
Nice sound! What setup is your turntable? Stock tonearm/cartridge/stylus? Thanks!
LambdaRF 4 months ago
@LambdaRF It's a stock, cheap turntable from RadioShack.
CameramanLink 4 months ago
very nice! it sounds very rich indeed, i am looking to build one also, however i am having trouble understanding how you have 2 channel in and out yet only one 12ax7? please explain as i am very novice in valves...
preludefan 7 months ago
@preludefan The reason for that is that this was the only terminal jack board I had at the time! Two of the jacks are not used for this mono preamp. You will need 2 12AX7s for stereo.
CameramanLink 7 months ago
@CameramanLink ahhh, as i suspected, it was mono... very nice sound- kinda prooves stereo isint that important sometimes... thank you for that!
preludefan 7 months ago
@preludefan This is just a prototype to see if the circuit functions properly. I was planning to make a stereo version after this one, but never got around to it.
CameramanLink 7 months ago
Were did you purchase that power transformer from? AES? Also, I have never seen that kind of rectifier since it has a box around it.
JPa311979 1 year ago
@JPa311979 Yes, the transformer is from AES but it produces quite a bit of hum. I wouldn't recommend it for this project. The rectifier is a regular full-wave bridge rectifier from RadioShack. I didn't feel like taking the time to draw diodes at angles with Paint.
CameramanLink 1 year ago
That's a nice sounding pre-amp. The schematic is identical to one I found on the web several years ago except there was no power supply. It had the B+ at 250V so I used a voltage doubler from another circuit. Also, I had to make the filament voltage DC to get rid of the buzz.
gregbarrett9 1 year ago
You must be very knowledgeable about electronics...for a homemade preamp sure sounds excellent...& a phono pream to boot, u get an A+!
rc52 1 year ago
@rc52 Thank you!
CameramanLink 1 year ago
I like the floating ground. Nice project!
AllAmericanFiveRadio 1 year ago
@AllAmericanFiveRadio The ground is actually a bus wire connected to the chassis at a single point, so it's not really floating. Maybe I'll build a stereo one and build it into a source selector preamp. Then I could have a complete DIY stereo system with homemade preamp, power amp, radio, and cassette recorder :)
CameramanLink 1 year ago