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    Building, troubleshooting and testing of these amplifiers should only be
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How can I improve this tube amp (see pics)?


2005-08-03 12:06 pm
Hi, according to the image below, it is a local-brand tube amp with two 12AX7 tubes. I just want to improve it. Unfortunately, doing the modification without schematic is kinda risky. I guess the first step would be two brown capacitors. I may replace both of them with better ones (i.e. Auricap). Please advise.


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diyAudio Moderator Emeritus
2002-10-24 10:19 pm
Replacing parts willy-nilly will make your parts vendor happy, and keep you off the streets and out of trouble, but is unlikely to enhance the performance of your amp (looks more like a preamp?). Start with the basics: what is it you're trying to improve, specifically? The next step is to trace out the circuit, then analyze it to see how it works. At that point, you can make an intelligent guess about the direction to proceed.
Well for sure the first thing you should've done before posting is get rid of that printed circuit board, it'll flatten the sound like nobody's business! Don't believe anyone who says PCBs sound good!!!!!

*SIGH* :rolleyes:

Old wives' tale. This is a misconception derived from RF practice. To be sure, ground plane (a.k.a. Dead Bug) construction works best for RF since it reduces the stray capacitance. However, that stray capacitance doesn't amount to much at 25KHz, whereas it's quite significant at 25MHz. If you have a PCB that flattens the sound, then it was a poorly laid out PCB. You can have the same problem with a poorly laid out point-to-point or dead bug board.

The one and only reason I don't go with PCBs for my projects is that I can have the circuit half completed dead bug style in the time it would take to lay out the PCB and etch it. If I were going to make them by the dozens, then I'd go for PCB for sure.
First question: Why you need to improve that preamp?
Have you high-grade source and amp, much better than this preamp in your system, so that you need to improve the preamp?

Second: maybe a larger photo will be better, to see all the preamp.

Every device can be improved, but it depend of many factors. If you have expensive - state of art - devices in your hi-fi system you need to improve the preamp with expensive components, like paper-oil caps or polystyrene or polycarbonate(for details on caps see http://members.aol.com/sbench102/caps.html ), alps or noble pot and so on. Also nos Mullard ECC83 are fine... ;)
If you have human devices I don't think you will see differences just improving only this preamp...

Post Scriptum: Tubes work better in vertical position.

My 5 cents-