Explendid amplifier designed by Michael Bittner, our MikeB

[MikeB]

No one interested in trying this amp ?

[dimitri]

No one interested in trying this amp ?

whisn one? there were at least 5 mentioned ...

[destroyer X]

As i am....

Dimitri has enormous International experience in electronics, his degrées papers, University Certificates will be shocked compared to many of us.

This man, some of the Russian Brains that are turning more rich the US know how, are someone very special, he is the one that is called when no one can find solutions for hard problems.

His presence here, loosing his precious time reading the thread and watching the schematics, is by itself, an evidence of Mike design quality.

thank you Dimitri, your presence here have enormous weigth to this thread value.

In my point of view, as i constructed this amplifier, is that everyone will be very surprised and satisfied with it.

If result was not very impressive.... check your circuit....i guarantee that something was made wrong related the construction or parts selection.

Since the first moment you switch this amplifier on, you will perceive how good it is... and prepare yourself to fall down from your chair when some dinamic peak appear, punching your stomach hard and shaking your home glasses.

Dimitri, i will prepare, rigth now, a Vodka, with lemmon and suggar....a Caipiroska!... in your honor.

Cheers!

Carlos

[MikeB]

Originally posted by dimitri


whisn one? there were at least 5 mentioned ...

Sorry for this...

This is symasym4:
http://www.diyaudio.com/forums/attac...amp=1121552051

This is symasym5:
http://www.diyaudio.com/forums/attac...amp=1121720926

These are the 2 interesting ones, symasym4 is the one carlos have built,
symasym5 has sligthly changed feedback, i think it sounds better and
is the one i actually listen to...

Mike

[sajti]

Hi Mike!

I will try to listen Your amplifier, if I have some time to build it. Currently I'm working on N-channel amplifier with MOSFETs but the topology looks something close to Yours.

sajti

[MikeB]

Hi sajti !
Yes, this topology seems to have much potential !
I wish you luck with your N-channel amp,
Mike

[sajti]

Originally posted by MikeB
Hi sajti !
Yes, this topology seems to have much potential !
I wish you luck with your N-channel amp,
Mike

Mike!

Is it right, that the VAS has about 2.5mA bias? I made some calculation, and it looks about 2.2-2.5mA depends by the Vbe of the ccs.
I feel, that 2.5mA is not enough to drive the output stage...

sajti

[MikeB]

Hi Saijti,
I had the same feeling, but simulations showed that it is enough
(With this topology), so i tried in realworld, and it really works !
It sounds very powerful, not weak or compressed in any form.
I just wanted to keep the smallsignalbjts.
When hardly driven, current goes to 5ma, and when saturating
it even goes up to 15ma, but this happens only when reaching
slewratelimit.
But, this low current makes it difficult to tune this amp to more power.
(For me, more than enough for now)
Of course, high beta devices are necessary for the outputstage,
was no problem, these onsemi devices measured hfe > 100,
this gives a currentgain above 1:10.000 for the output.
(actually, mje15030 = 130, mjl3281 = ~110)

Mike

[sajti]

I think, that I will try to increase the bias little bit. Say 5-6mA looks enough, to drive 2ohms loads as well. For my N-channel amplifier I use 10mA, but little more would be better.
Did You tried this amplifier with triple darlington output?

sajti

[MikeB]

I choosed the ~2.5ma to avoid heatup the smallsignal-bjts, with
5ma they will get very hot. Now they operate at ~40° (or less),
just feeling very warm, not hot yet.
I tried a tripledarlington with this amp, but already gave up in sims,
it get's too difficult to get good stability. With a stable version i ended
up in an amp having much higher phasehifts and higher thd.
It's too much gain in this case...

I use this amp to drive 4ohm speakers, and it plays effortless up to
very high volumes, so i think it's currentcapabilities should be high enough.

Mike