LAB10 Audio Amplifier Project

[lineup]

not the least thought about any jacking

to me, you are showing interest in the subject
and doing good contribution:
Some little reading for me and for our friend beppe61 from Italy

[beppe61]

Originally posted by lineup
not the least thought about any jacking
to me, you are showing interest in the subject
and doing good contribution:
Some little reading for me and for our friend beppe61 from Italy

This is sure and thank you sincerely Mr Lineup for this extremely interesting 3D.
Maybe I am quite superficial but I do not think that complexity is a guarantee for a good sound.
Instead I like terms like: short signal path, few gain stages, single pair of good output devices, no current limiting circuits, ecc.
Of course in some situations complexity is a must.
For instance to power big speakers in big rooms we need a lot of output pairs ...
But in a "normal" listening room with normally efficient speakers a beautiful simple amp can give really nice performance.
Thanks again and kind regards,

beppe

[richie00boy]

Beppe, by saying better ways I did not necessarily mean more complex, nor more active parts. I'm sure my design will fit in with your ideals.

[beppe61]

Originally posted by richie00boy
The voltage gain is not the issue, the op-amp section can only swing within a couple of volts of it's rails, so with rails limited to 18 volts by the op-amp maker, it's pointless using higher rails for the power stage.
There are also better ways to make a power buffer than what is shown here, at least where providing a good quality bias is concerned.
I am actually in the middle of prototyping an amp using TIP142/147 devices, as you inspired me to design a simple, easy to build yet good performing amp when we corresponded about the Albarry design. It's all done bar some fine tuning.

Very beautiful indeed Sir!
Great and extremely nice little amp.
Congratulations!
I confirm you that with just a pair of TIP142/147 devices it is possible to get very good sound as in the Albarry design.
When we opened one of these monos we could see:
1) very big toroidal for a 45W/8 ohm amp (a about 400VA very nice toroid from ILP, UK)
2) two big filter caps of the screw terminals type
I think that the secret of its clean and powerful sound could be this very powerful power supply and the lack of current limiting devices/circuits that can harm the dynamic response.

Anyway, could you give us some more details of your excellent amp?
Voltage rails, voltage gain, input impedance, what kind of protection have you chosen (very important point for me).
It looks very very well done.
And very cute also.
Please keep us informed on this 3D.

Thanks a lot and kind regards,
beppe

P.S. and the next maybe "final" step would be to replace the output pair for a pair of mighty Sankens darlingtons in order to get a dynamite little monster.
I understand that Sanken are the best for linearity and ability to deliver clean current to loads.
If I am not wrong they can source more than 10A and give a prodigious response.
Nevertheless I can testimony that just a single pair of TIP142/147 can give an enough astonishing sound.

[beppe61]

Originally posted by richie00boy
Beppe, by saying better ways I did not necessarily mean more complex, nor more active parts.
I'm sure my design will fit in with your ideals.

Completely Sir!
Please give us more details.
Thanks again and kind regards,

beppe

[richie00boy]

This is the prototype schematic, note that it's design and/or components values may be subject to change once testing is complete.

Ignore the transistor types, they are just what models I have in the schematic program. 2N5401 is used in the input stage and ZTX653/753 in the voltage amplifier stage.



Sanken devices could be used, but to gain the best results, i.e. take advantage of the increased speed, the compensation may need to be adjusted a little.

As you can see no protection other than rail fuses is implemented. I think this gives best dynamic response. The amp is designed such that if either of the rail fuses blows, the amp shuts down immediately so there is no way that there will be a bad DC output fault.

Input impedance is approximately 35k, voltage gain is approx 27 from input to output. PSU is 25 volt transformer.