Hi everyone I'm new to the forum, I had a question. About the Oatley sobmini headphone am kit. I have read on this forum that former incarnations of this headphone amp were used quite successfully as pre-amps for hi-fi. I was wanting to know is there anyway this kit could be.modified to be used as a bass guitar pre-amp? If so how exactly what parts would I change and how will it effect the sound ect... Also if I want to wire it up not using battery power can I just get a 3 volt wall wart and use it or do other things need doing? And one last question. Are there any eBay Chinese pre-amp kits that are capable of being used as is or modified for bass guitar pre-amp use?perhaps the 12ax7.and 12au7 type with hv supplies would be the closest thing? IDK noob obviously. ....thanks so much and nice to finally post
The batteries to power one of these will last a long time, no sense going to AC unless you want noise and potentially hum.
However, the subminiature tubes used in these amps are VERY microphonic. Add to the fact that they are directly heated tubes (no cathode) and the unsupported filaments love to oscillate. Out of maybe 12 tubes I only got 2 or 3 that didn't have a high frequency oscillation.
Definitely NOT recommended for a low level signal out of a guitar. You'll just be amplifying a lot of nasties once you plug one of these into your guitar amp.
Steve
However, the subminiature tubes used in these amps are VERY microphonic. Add to the fact that they are directly heated tubes (no cathode) and the unsupported filaments love to oscillate. Out of maybe 12 tubes I only got 2 or 3 that didn't have a high frequency oscillation.
Definitely NOT recommended for a low level signal out of a guitar. You'll just be amplifying a lot of nasties once you plug one of these into your guitar amp.
Steve
DC Walwart ti submini tube preamp
How can I use this as a simple pre-amp for feeding a basic power amp for music listening. I have a enclosure. Other than input output jacks and DC in jack what else would I need to make this a finished Pre amplifier that could run. From a DC walkway 6 v or 18 v if voltage bobooster were bypassed.? Any filtering of the DC with caps?could someone walk me through this if possible It would be greatly appreciated .thank you very much. Any questions let me know I'll tell u what I'm looking for.
How can I use this as a simple pre-amp for feeding a basic power amp for music listening. I have a enclosure. Other than input output jacks and DC in jack what else would I need to make this a finished Pre amplifier that could run. From a DC walkway 6 v or 18 v if voltage bobooster were bypassed.? Any filtering of the DC with caps?could someone walk me through this if possible It would be greatly appreciated .thank you very much. Any questions let me know I'll tell u what I'm looking for.
Have you already bought a K272C? If I understand your post #5 you want to use it as a sort of line stage. Yes it will work as a line stage but you'll want to use a regular dual pot for volume and not individual trimmer pots supplied with the kit.
You can go with a DC wall wart but why not stick with batteries? 3 D-cells will last a long time and avoid any noise issues from an AC-powered supply.
The thing is, and I've played with these things a bit and have experienced the tube noise and microphonics first hand, it's not really an ideal line stage. Tube noise issues aside there is an op amp chip after the tube gain stage. It's run from a single polarity supply so it needs an output capacitor, in this case a nasty electrolytic. You could replace it with a say, 1uF film cap if you will only be driving an amp and not headphones.
You'll have fun fooling around with it and the voltages are low so you won't hurt yourself. If you want a true tube line stage with no crazy voltages try this one from Broskie: New Aikido 12Vac PCB and part kits
Good luck,
Steve
You can go with a DC wall wart but why not stick with batteries? 3 D-cells will last a long time and avoid any noise issues from an AC-powered supply.
The thing is, and I've played with these things a bit and have experienced the tube noise and microphonics first hand, it's not really an ideal line stage. Tube noise issues aside there is an op amp chip after the tube gain stage. It's run from a single polarity supply so it needs an output capacitor, in this case a nasty electrolytic. You could replace it with a say, 1uF film cap if you will only be driving an amp and not headphones.
You'll have fun fooling around with it and the voltages are low so you won't hurt yourself. If you want a true tube line stage with no crazy voltages try this one from Broskie: New Aikido 12Vac PCB and part kits
Good luck,
Steve
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