looking for simple discrete 100W DIY amp

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I've built several headphone chip-amps and would like to build a simple but good performing discrete power amp for my office speakers. They are inefficient but decent sounding, and would like to get at least 100W x2 into 8 ohms. I found the c200 at ampslab. Are there other simple, easy-to-build discrete DIY designs of similar (or higher) caliber that I could look at?

TIA,
-Jason
 
Hi halusha,

You might like to check out the new 'Simple Killer Amp' I designed
earlier this year, it's available as a kit (without heatsink) -

http://members.dodo.com.au/~gregball/guru_004.htm

and is discussed quite thoroughly in -

http://www.diyaudio.com/forums/showthread.php?s=&threadid=65286

This design delivers more efficiency, more performance, is 'patent pending', simple to build and, for now, low cost. You can build two simple low cost monoblocks (only needs 160VA traffo) and blow the monster amps away.
:D

Cheers,
Greg
 
Hi DW,

Hmmm. How do you describe all the parameters of a PP Class A SS amp in a few sentences? Tricky........:bawling:

Stage current in the input diff pair need not be much more than 1mA. Anything up to 5mA is fine, with jfets needing more to extract the last bit of transconductance.

Stage current in the voltage amplifier depends upon:

1. Number of output pairs, their beta, and input capacitance.
2. Bipolar or Mosfet.
3. Driver parameters.
4. Required slew rate.
5. Stage current in diff pair.
6. Rail voltage.
7. Loading of the VAS output; sometimes a resistor is used here, as in the Symasym 5 from Michael Bittner.

As a general rule, for 36V rails, a 60W into 8R amp, around 7mA is sufficient with a high beta bipolar output stage. Increase this around 40% for mosfets, since they have no driver and are connected directly at the gate to the VAS output.

When you look at amp design, there are a myriad of designs and operating points out there, and some are just plain wrong, yet they work OK. You have to do your testing carefully, and move the operating points up and down until you get the optimum sonics. This takes time and effort.

Miller capacitance calculation is possible to calculate, but it's tricky because of parasitics in the circuit board and other spurious issues around the design. As a general rule, the best approach is empirical. Start around 100pF, and using standard values, move down to the minimum. The amp will become audibly fuzzy and distorted at too low a value, and may even blow up the speaker AND the output stage; go up 10pF from this point, and move forward in 5pF steps from this reference. The value will change with layout, component choice, etc. Of course, it goes without saying that you should use a conventional loudspeaker with commonplace impedance characteristics; you will find that the optimum miller cap for one speaker will be different for another. This is perhaps what makes it so difficult; you have to make the amp stable for all loads, yet too much Miller capacitance will destroy the sonics.

Hope this at least introduces you to the complexities; it's not particularly scientific, more empirical, but there is a very good reason for this; there is no standard load, and the amp is not judged on its specs but rather on its sonics - a highly subjective, market judgement which any designer ignores at his peril.

Cheers,

Hugh
 
DW?..lol..im sure thats from a cartoon..ah yes..darkWing duck..hahahhhhaa..used to love that show..nice one hugh :)..thank you so much for the paragraph you wrote..being as that i am inexperienced, i will go away and digest this stuff...may i ask more questions if needed?..thnak you once again i really appreciate it
 
Hi Sagarverma,

Complicated isn't it. Just look at C3,4 =1n - that'll kill PSRR on both supplies. You'll be listening to PS artefacts - at HF where they all end up!

Eliminating the nasty high order distortions is fundamental to a good sounding amplifier. Taking care of PSRR is part of that. Reducing output stage high order nonlinearity and applying positive and negative feedbacks judiciously will improve the resolution and lower the residual miasma.


These principles are embodied in my amps. Nothing mystical.

Cheers,
Greg
 
Thanks for all of the suggestions and links! I am leaning towards building the ESP project 3A or 101 (or the SKA, ahhhhh so many choices!).

Where do you guys and gals find good enclosures and heatsinks? The enclosure work is the part I hate most about any project, so a ready-made one would be tops.

-Jason
 
AKSA said:
DW,

Ask away, I will answer if I know the detail! :clown:

BTW, Sagar, there is generally poor correlation between low distortion figures and great sound. I have a few ideas, but most of them are heresy........:D

Cheers,

Hugh

plz tell more.


amplifierguru said:
Hi Sagarverma,

Complicated isn't it. Just look at C3,4 =1n - that'll kill PSRR on both supplies. You'll be listening to PS artefacts - at HF where they all end up!

Eliminating the nasty high order distortions is fundamental to a good sounding amplifier. Taking care of PSRR is part of that. Reducing output stage high order nonlinearity and applying positive and negative feedbacks judiciously will improve the resolution and lower the residual miasma.


These principles are embodied in my amps. Nothing mystical.

Cheers,
Greg

sugest possible cures in this amp.


halusha said:
Thanks for all of the suggestions and links! I am leaning towards building the ESP project 3A or 101 (or the SKA, ahhhhh so many choices!).

nice and simple(p3a).i have heard it playin.
 
Hi Sagarverma,

If you had something as breakthrough as SKA you'd promote it too. Do you want me to walk you through it's advantages again?

Re: Hafler You can improve this amplifier with two-pole compensation techniques as made public by D.Self. The basic topology is a limitation which is why I designed my new topology with considerable intrinsic superiority.

It disappoints me that my SKA is even compared in this company,
with it's revolutionary topology, quality double sided fully ground planed and through hole plated boards and matched components and an absolute bargain compared with ugly inefficient generic application note rehashes - and I may leave these forums.

Greg
 
Sagar,

Try any single ended triode amp. A good one will not exceed about 2% at listening levels, yet they sound glorious, in another category from the usual SS stuff. Would you tolerate 2% on a SS amp at listening levels, particularly a global feedback, PP amp?

No, there is something more to it - this debate has been raging for decades, with considerable bad feeling in opposing camps.

You might do lots of reading in the tube forum........

Cheers,

Hugh
 
hi Hugh,

i dunno y,but i simply love IC amps.its been 11yrs working on chips.small size,compact.:eek: it all fascinates me.moreover,class d looks ultimate to me.small 'heatsinkless' amp with SMPS power supply will give such a small and powerful amp::IMAGINE!

discrete has come recently in my mind.
triode also on cards(so r d tubes;) ),but simply jus 4 experience.bec my heart lies inside ICs:)


offline::hw u made out my name?
 
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