Pre-Amp

[Mindcrime]

Hey guys,
I have been looking for a budget pre-amp kit. although not a kit I thought this looked interesting..any thoughts?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=150115837156&ssPageName=STRK:MEWA:IT&ih=005

 

[dsavitsk]

It's not grounded properly.

 

[Tweeker]

12AU7 wouldnt be my first choice for a preamp.

Please tell me the wall wart in the lower left picture isnt the outboard power supply.

 

[Mindcrime]

good catch, but I don't think it is.... lol

 

[SY]

12AU7. Two wire power cord. Pass.

 

[Mindcrime]

Thanks for the input, any suggestions?

 

[Sonusthree]

Thanks for the input, any suggestions?

Email the seller with some questions about the supply at least. I suspect that it is a relatively low voltage device but I may be wrong (there's a millionth time for everything). This might be why it is so cheap. It may well be working on a 12 or 24V supply with (or without) a voltage doubler or similar to supply a viable B+. Ask the guy and see what he says.

I'm really enjoying my experimentation with low voltage tube stuff so I'd hate to pay for anything (so easily DIY'able) that wasn't a proper (scary voltages) circuit.

Regards,
Martin.

 

[jduffy]

I'm cautious when I see someone use the word "phylosophy".

 

[Tweeker]

Phylosophy is a perfectly cromulent word.

 

[FastEddy]

" ... a perfectly cromulent ... " pre-amp = http://www.bottlehead.com/et/adobespc/foreplay3/foreplay3.htm

Granted, about 2X the amount shown on the eBay dice, but at least its grounded properly ... just add solder.

 

[jduffy]

Phylosophy is a perfectly cromulent word.

Quoting the classics I see!

Excellent.....

 

[kevinkr]

My uninformed suspicion is that it uses a low voltage wall wart for power and the two wires you see are conveying low voltage ac to a filament supply and doubler for B+. The box looks small enough that he would be hard pressed to fit a small transformer in there to step up the ac for a higher B+ supply.

Provided that the wall wart is double insulated there may be no issue with the lack of a ground connection, but I'd want to know the answer to that question at least before I bought one of these.

I'd email the seller and ask for more technical details, OTOH you could build something better for about the same expenditure if you shop around carefully for the parts.

I'd look at the 5687, 6H30 or ECC99 as viable single tube pre-amp candidates. All have significantly better linearity and lower Rp, gain might be excessive which is probably an issue with the design on eBay as well.