Simple balanced driver circuit.

[Graham Maynard]

This topology could be modified to become an audio amplifier, a headphone amplifier, a line driver or preamp.

Shown here as 8 ohm class-A which should sound first class.

[destroyer X]

Have you constructed this one dear Graham?

The reason of my question was because a friend came to me and asked if i had constructed the last GEM,...that one with the choque, the enormous coil in series with the output line...the upper rail load.... and i perceive that he will not construct, as i told him that i personally had not constructed that last design.

I told that i did not have listened to that one....but also i told him that one Brazilian had assembled, Eddie Eayoama, and it may be reproduccing the unit to close friends...he said sounded great.

But i have not made exactly that last one...mine was another one... and this made my friend give up....this is a very sensitive matter as i could see...people want a complete guarantee...and this can be given if the unit was tested real world and subjected to heavy and continuous testing.

I have perceived that people trust, a little bit more, in those already tested real life amplifiers....and this is the reason of my question about this one.

It seems that you have simulated it only.... this do not turns the amplifier bad...as it is clearly good...but may reduce people trust on it.

I will tell you about another forum...hehe...more an Prisional institution, where banished people are there making noises...and other good people too....those guys loves brand new ideas...i think they will love your circuits.

I was almost kicked out from there...one single bad educated guy, but all moderators entered and used the long arm of the law...i loved that...they are Police!..the way i always dream about moderators.

there are many good here....Weldon is fair...SY is an supersonic figther, Anatech is friendly, Planet 10 has a chinese patience..well...Variac is kind...we have a lot good here...but those there hold a double barreled and shot clearly between the eyes....GREAT!

am i wrong?

regards,

Carlos

[janneman]

Originally posted by Graham Maynard
This topology could be modified to become an audio amplifier, a headphone amplifier, a line driver or preamp.

Shown here as 8 ohm class-A which should sound first class.

Graham,

That's an interesting circuit for sure. I like people that go into uncharted terrain! I see a lot of opamp techniques in it. The abundance of large elcaps isn't too attractive but possibly that can be reduced in further evolution. What I wonder is how the thermal stability is like? Any thermal feedback necessary between the bias setting current sources and the output stage?

Jan Didden

[destroyer X]

A very good guy too.

regards,

Carlos

[Graham Maynard]

Hi Carlos,

This circuit is based on buffers that have already been constructed and are running with the GEM amplifier. They SOUND good.
No not built - just out of my head today.

Many folk seem wary of the choke in my 100W GEM design. Sonically it works just fine. It is fully tested and fully satisfies me.

Daniel Bosch in S Africa has built several 200W GEMs with the CCS class-A load, and says he is going to sue me - for 'time'. He uses them with ordinary LS and Apogees, and says that once he starts listening - he can't stop !!!

Hi Jan,

My thoughts are that the single bias setting transistor could be thermally coupled to a heatsink for power amplifier design.

Here would be a 600 ohm line driver version running from regulated +/-24V rails. VERY low distortion. 12dB gain. 100k input impedance.

[Graham Maynard]

(Carlos,
your own thread had gone quiet and I felt that something was missing, so I had to do something ! )

[janneman]

Originally posted by Graham Maynard
Hi Carlos,

This circuit is based on buffers that have already been constructed and are running with the GEM amplifier. They SOUND good.
No not built - just out of my head today.

Many folk seem wary of the choke in my 100W GEM design. Sonically it works just fine. It is fully tested and fully satisfies me.

Daniel Bosch in S Africa has built several 200W GEMs with the CCS class-A load, and says he is going to sue me - for 'time'. He uses them with ordinary LS and Apogees, and says that once he starts listening - he can't stop !!!

Hi Jan,

My thoughts are that the single bias setting transistor could be thermally coupled to a heatsink for power amplifier design.

Here would be a 600 ohm line driver version running from regulated +/-24V rails. VERY low distortion. 12dB gain. 100k input impedance.

How about making that 22 ohms into 2 x 11 ohms, couple the output from the tap, and replace the two 4m7 caps with a single 2m2 across the 2 x 112 ohms? Would that work? Apart from the offset, that can be dealt with cheaply anyway.

Jan Didden

[lumanauw]

Hi, Mr. Maynard,

I want to ask you about the 4700uF cap in the feedback network. In your experience, is it OK to put big valued caps in that place? (not disturbing the sonics). I assume this cap can be below 10V rating?

[ilimzn]

Originally posted by janneman
How about making that 22 ohms into 2 x 11 ohms, couple the output from the tap, and replace the two 4m7 caps with a single 2m2

that's actually not completely equivalent, the 11 ohms are in series with the output impedancesof the top and bottom half of the buffer, whereas in the original schematics the 22 ohms is AC bypassed. However, given there is already a series resistor after that, one could use this fact to eliminate it.
The way this buffer derives it's quiescent curent reminds me strongly of the MF A1 amplifier. It also used a symetrical layout where the halves are conencted via resistors, and each half has a DC bias introuduced, in order to have a defined quiescent current through the connecting resistor.

The only slight complait i have with this is about the 'balanced' - to be honest, reading the title, i was expecting a differential driver

[destroyer X]

mission completed related that thread Graham...good that we have you once again....very good.

regards,

Carlos