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Title: How do I test my Pre-Amp?
Post by: One-way on June 14, 2009, 04:49:07 AM

Hi Folks,
Ive finally got round to completing the Eliiot pre-amp and want to be able to test it so I know its working correctly before concentrating on the power amp section which Ive started on.
Ive got a 12 volt regulated power supply that i hooked up to the + and - 15 volt rails. Nothing went bang or got hot so I guess "so far so good"
I looped all the connections that go to the control pots together so there is a circuit through.
What voltage readings/ tests can I take to know everything will work as designed.
Can i hook up a speaker or headphones to hear an input signal?
http://www.ssguitar.com/index.php?action=dlattach;topic=1083.0;attach=620;image

Title: Re: How do I test my Pre-Amp?
Post by: phatt on June 14, 2009, 09:47:50 AM

Hi 1way,
Yes just make a small audio lead up and plug it into any line input or other similar equipment.
Old Tape recorders/Ghetto blasters come in handy for things like this. 8|

If no go, check you have DC on the power pins of the opamp,, Pin4 = Neg
Pin8 =Pos
Cheers Phil.

Title: Re: How do I test my Pre-Amp?
Post by: One-way on June 15, 2009, 08:21:42 PM

Thanks for that. I will check the voltages. What voltage should I be seeing at pin 4 and 8 going through the resistors and capacitors with a 12 volt supply? I hooked up a guitar jack to the input and plugged in my LP but Im guessing the input signal is too small to reproduce thru a speaker without going thru the power amp as well.

Title: Re: How do I test my Pre-Amp?
Post by: J M Fahey on June 16, 2009, 09:43:36 AM

Excuse me OneWay, but, what did you say you powered it with? Did I hear "a 12 volt supply"? A single one? 2 wires, as in +12V and ground (or "negative")?
You need 3 wires: +15, -15, and ground. You may skimp on the voltages and use +12 and -12 (plus ground) and in a pinch +9 , -9, and ground, using 2 x 9V batteries in series, with the center tap grounded. Good luck with your preamp.
You can wire a plug to its output and hook it to some friend´s guitar amp (if possible to a power amp in or loop return jack, but if not available, the regular input will do; or wire a couple RCA plugs and hook it to same HiFi equipment you have around. As Phil suggested, even a ghetto blaster aux input will do.

Title: Re: How do I test my Pre-Amp?
Post by: One-way on June 16, 2009, 10:15:50 PM

OK I get it now with the floating power supply. Thanks

Title: Re: How do I test my Pre-Amp?
Post by: troublerat on June 28, 2009, 10:53:43 AM

Not that I can add a lot to what has been said, but I have built that pre-amp and am very pleased with the sound. I used R G method of getting 9+ 9- out of 9volts supply. Use a 1044 charge pump. I like the way elliot makes the tone shaping elements so you can totally cut a particular band.

Title: Re: How do I test my Pre-Amp?
Post by: J M Fahey on June 29, 2009, 10:01:11 AM

Hi Troublerat. To grant our respects to the original designer, that tone control is Leo Fender´s creation, and yes, works like a charm and has been *widely* copied. Hail Leo !!

Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Preamps and Effects => Topic started by: One-way on June 14, 2009, 04:49:07 AM