Good transistor amp


2016-04-22 7:27 pm
My first post here so please be kind :)

I am looking to build a good transistorised amp. Preferably 60-70 watts. I have already made the philips amp with universal preamp so looking for something that is better sounding than this one. Plan to use it as my primary amp.

Any ideas...

Ps: no chip need amps please.....



Paid Member
2007-09-15 8:14 am
Welcome to diyAudio :)

A question like that will get you countless different answers. How about something a bit oddball like the original Hitachi lateral FET design. Very simple and with very very good performance even by todays standards. Modern lateral FETs from Exicon an SEMELAB would be ideal.

Maplin did a kit for this years and years ago. Do your research and you should be able to come up with board layouts etc.
Circlophone is excellent (I have one) but a bit more complicated than some of the simple amps with maybe circa 8 transistors.

The Apex FX8 is very simple and easy to build lateral MOSFET. This thread has dozens of amp designs, almost all easy to build and sound great.

AX11 and FX8 are probably simplest.


Want something more sporty? AX11TEF

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I threw this amp together for a few local fans in 2009, It may be of interest to you. It is the kind of amp you build and it works first time. It is a simple single board design that contains the power supply as well. Power transformer can be around 35-0-35 VAC. The attached graphs are really short term power predictions, and useful to someone who listens to music and not pump sine waves at full power for hours on end.

You are welcome to ask as many questions you like, I will try to answer them as accurately as possible.

Everything you need to do the PCBs are contained in the files, even Gerber plots. This amp is a lot of fun and sounds pretty nice.

The amp shown in the picture is one my brother built (he is not an electronic guy at all) using the base plate (2mm thick) as heat sink - it is super simple amp.

EDIT: There is a wire link under the board connecting the ground at the terminal the the start ground at the other end of the board, just to keep things tidy.

EDIT2: Just in case someone asks the question. The picture is of my wife of 40 years and still going strong and hated my hobby since the day we met.


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One of the few amps not using a differential LTP on the input. Do you have a circuit schematic?

If You want a very very stable AMP - try this one very simple Lateral Mosfet AMP. Driver (VAS) and CCS transistors are video amplifier transistors - from CRT TV.
I could not make it to oscillate even with unity gain. No compensation needed.
THD with BIAS current 40-30mA - 0.1% and not rising till 20kHz.
Hitachi amp is good, good balance both diff-cascades, but its prone to oscillate, the gain vs frequency is rising (before falling) if there is no ~300pF at input.

EDIT: There is a Vbe multiplier in this schematic - if using not Lateral mosfets. With laterals - It is not needed, Vbe mult. could be replaced with 1-2k pot.


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I recently made this amp. Super simple build and excellent sound and predicted performance in sims is quite amazing. Clean squarewave to 200kHz. Inexpensive IRFP MOSFETs.

Schematic (note that a 2.2k needs to be added to input between 10uF and 22k):

As built:
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Hi Bangla H,
Sorry did not noticed about which amp are You speaking.
Thought that You know the name of the member xrk971 - is Nico :)

After looking again- with sharp eyes i found a missed pot.
That pot will not affect the bias current of Output mosfets.
You need to add a pot, for example - instead of one of biasing diodes.

If you just add third diode - it could result bias current too high.