hello,

I am thinking of starting a first amp project and i'd like to have some advices from you experienced people.

First some background: i have been building guitar effects and 1 tube amp in the last 2 years. I have a general understanding of circuits and how some parts of them work, but nothing really complicated yet.
I usually play at designing my own pcbs in eagle when i see a schematic that i like. Usually it's much simpler than an amp, but nothing seems too complicated to be done with 2 layers and a few squares inches of pcb.

I have a solid state amp project that i'd like to concretize and i would like to have your opinion and advices.
The idea behind the project is to clone my beloved polytone mini brute.
The preamp would be a clone of the preamp of the mini brute (basically an op-amp amplification device with an active bandaxall EQ).
For the power amp, I've heard the polytone power amps are really hard to bias and basically a bad design. I've also read that power amps basically do NOT change the sound at all, they just amplify the sound. So i was thinking that i could move away from the polytone power amp for a classical design with more qualities. However, i would like to be SURE that i' wouldn't be loosing some of the key features of the polytone sound by doing that.. do power amp influence the sound/dynamics/feel of the amps at all?
Power supply : linked to the power amp i suppose -> ??
Dimensions : as small and light as possible .. my polytone packs everything in a very tight package, and 9 kgs.. i'm hoping to do that, or better as components are now smaller...


Here is what i already know that i don't know...
- The practical connectivity into the amp: how to send signals/power to the boards (if there are more then one), and switches.. what physical connections should be used and how.
- heatsink!!! i don't know anything about it. my polytone has 2 power transistors glued to 2 big heatsinks, which are stuffed into the CLOSED amp, filled with fiberglass foam .... so i guess heat dissipation is not at its best, still, it doesn't seem to matter.. i guess it's possible to do better, how to manage that properly.
- power supply needed : depends of the circuit and power
- where to order a decent and not too expensive faceplate
- the actual cabinet construction . not the slightest experience but i can be helped.

So my main question at this point is : would changing the power amp fro mthe polytone power amp to a classical design change the sound?
How do i calculate the needed heatsink and power supply ?

Thanks in advance

Hello,

I'm quite new to amplifier tweaking/building. I recently serviced a polytone i bought used for 25 euros and that got me thinking about building a polyclone.

The amp i have does follow exactly the schematics on the murchmusic site.
However, i read that this power amp was difficult to bias and was not really easy to build. Another guy that build a polyclone told that he replaced it by a FET power amp.
How much does a power amp change would change the sound of the amp?
Are there classical and good sounding power amp designs around 80 or 100 Watts that would preserve the polytone sound?

In general, are power amps transparent and does the color of the amp comes from the preamp?
Thanks in advance for your help

Hello,

New member here,
as my polytone is waiting for the post office to be opened to have the needed caps to finish the cap job, i thought i might as well post some gut pics here.

From what i gathered, the preamp and power amp correspond to the schematics posted on murchmusic's website.


Hope it helps someone.

Cheers
Arnaud