Suggestions for mono block amplifier?

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Duco

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Joined 2011
Dear All,

I just finished my first amplifier ever. And it sounds wonderful to my opinion:D It's based on the L12-2 amplifier board often offered on ebay.

But I still got some transformers and capacitors left:
2* 300VA 2x22V transformers
4* Mallory 17000MFD @ 40V
4* (oversized) Sprague 50000MFD @40V
8* Philips 15000MFD @ 40V

I was thinking to build a set of mono block amplifiers, not too fancy but nice enough for my monitor audio RX2 speakers. Can some one help me point out some amplifier kits? I am still a rookie so i don't think I can handle a build completely from scratch.

Hope you can help me:)

-Duco
 
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Duco

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Joined 2011
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Duco

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Joined 2011
Bigun

Bigun

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diyaudio.com/community/threads/tgm8-an-amplifier-based-on-rod-elliot-p3a.245619/
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my vote goes for a JLH 1969 Class A amplifier. Last time I looked there were pcb's and kits available on ebay. Here's an example from a seller with 100% feedback rating:
http://www.ebay.ca/itm/2pcs-High-qu...Components&hash=item1e6be3cea0#ht_3494wt_1413


The circuit is simple and elegant - learning about how it works is worthwhile.

The Class-A Amplifier Site

It's capacitor coupled output so built-in speaker protection. If you use 2N3055 power output transistors they should be easy to find at a reasonable price and you shouldn't have to worry about amplifier stability/frequency compensation since they are relatively 'slow'. The amp has an excellent reputation for sound quality.

The Hiraga amps are also excellent, but I believe they are more prone to power supply hum at the output.

With any Class A amplifier you'll need to get some heatsinks. They will need to be large. But they don't need to be fancy so look around for eBay options.

and I'm willing to follow my own advice - I'm currently building a dual-mono JLH 1969 myself.

It's one of the most popular amps of all time and there's a long standing thread about it here: http://www.diyaudio.com/forums/solid-state/3075-jlh-10-watt-class-amplifier.html
 
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Duco

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Joined 2011
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wahab

Member
Joined 2009
Duco said:
I have looked at all results so far and narrowed my options:

This ones should work perfectly on +/- 32V without adjustments right?
MX50X2 Class AB Power Amplifier Board AMP Kit 2-Channel | eBay
Click to expand...

This one should have the best perfs of the three mentionned
in the post above.
Besides , the guy give the schematic , wich show a classic topology
that perform well, yet it can be improved with very few typical mods
that you can fish in this forum not counting that depending of your
heatspreaders it can be biaised in class A.
 
D

Duco

Member
Joined 2011
wahab said:
This one should have the best perfs of the three mentionned
in the post above.
Besides , the guy give the schematic , wich show a classic topology
that perform well, yet it can be improved with very few typical mods
that you can fish in this forum not counting that depending of your
heatspreaders it can be biaised in class A.
Click to expand...

Allright. How "in short" can I modify it to run in class A? Is it better than the SKA GB150? I read good things about them..

-Duco
 
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wahab

Member
Joined 2009
There s a pot in the board to set the bias current.
If needed the bias range can be extended by sligtly
increasing/decreasing one of the resistors connected to its extremities.

As for the GB150 , i dont know its schematic so i cant give any opinion
about it.
 
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Duco

Member
Joined 2011
Dear audiodiy people,

Thanks a bunch for all your replies! I've been quite busy studying for my exams. But i'm going to continue with the diy project.

I would really like to contruct a pair of monoblocks or a stereo amplifier based on the pass f5 design. During my search I stumbled opon a small f5 pcb, I could not figure out what it's name is and where to buy it. So thats my first question.

Second, i would like to use my two 2 x 22v 300VA transformers, so I can shrink the stash of parts i collected in quite some time. Is this possible with the F5 design?

Yours,
Duco
 
Bigun

Bigun

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for pcb's try here: First Watt Clones - Power Amplifiers - PCBs

Your transformers are something I would consider suitable for a Class A amplifier. I have a trafo with 18V outputs and I'm using for a Class A amplifier (a JLH rather than an F5).

I'd suggest a single chasis, saves building two complete units. You can still use dual-mono construction of the amplifier - meaning each one has it's own trafo and separate wiring. They would share the same mains cable and power switch.
 
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Bigun

Bigun

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Duco said:
Allright! Thanks!

The JLH looks pretty nice. But I heart so much good things about the F5 amplifier, that I want to build one for myself. But the 2 x 22Vac secondaries are not suitable for a Pass amp?

Duco
Click to expand...

Let me think about this a bit more. Your transformers when rectified will give 22 x 1.4 = 30V d.c. per secondary. Probably the best option therefore is to use one trafo for each power rail, i.e. one for +ve and one for -ve which doesn't allow dual mono but I don't think that's something to lose sleep over.

The F5 schematics I saw call for +/-24V rails. So you could build a power supply with Capacitance Multiplier to smooth the rails and drop the 6V from your rectified 30V to around 24V per rail.

You will get the best advice by posting over on the PASS forum rather than this as many over there are familiar with the F5 amplifier you want to build.

I way yes - you can build it, just need to decide on the tradeoffs and do get yourself a big heatsink.

p.s. you can always build a JLH in the future and try it in the same chasis with the same power supply, say just one channel, and then you can compare the F5 with JLH. The journey has no end - be warned ! :D
 
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Duco

Member
Joined 2011
Thanks for the advice. I will ask it on the Pass forum :)

I stumbled upon these last week and they stayed on my mind:
2 x Class A 10W Power Amplifier PCB Based on Aleph Mini | eBay

MOSFET Pure Class A Amplifier Kit Thick PCB | eBay

Hiraga Super 30W Class A Amplifier Kit | eBay

I heart a lot of good things about the Hiraga super, one is based on the F5 and the last one the Aleph mini. I'm still having troubles on deciding weather or not i could run them on a 22*Sqrt[2] = 31Vdc power supply. I'd love to start building soon:D but i don't want to waste my money on a project that will not succeed:D

will some of the above cirquits work on the 31Vdc with minor adjustments?
 
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