Marshall Lead 100 MOSFET 3210 Head

[phatt]

I lost my Wife last year And 20 years earlier she lost her son to suicide, she carried on but it left a mark on her outlook on life.
Yes the things that life throws at us can be soul destroying.
So I have some understanding of your great loss.
Phil.

[J M Fahey]

Sad about some if your news, happy you made it through your operations and are still with us.
Doubly so because you want to plug the old soldering iron again 😄
Keep us updated.

[Kaz Kylheku]

I was looking at the schematic of the power section of this amp recently.

Supposedly, it doesn't have a bad DC offset, only something like 0.1V.

Yet, there is a severely mismatched DC resistance at the differential stages. Like 47 kΩ on the input side, and 10 kΩ on the feedback side.

I'm thinking, they used the collector resistances to more or less balance it? On the input side of the differential stage, there is a 1 kΩ load resistor on the collector, but the opposite side has a 100 Ω.  I'm guessing that results in more base current.

If you can get 4.7X the current to flow through the 10 k, it will create the same offset voltage as the 47 k.

I have some book somewhere with a chapter on diff amps; should brush the dust off.

[J M Fahey]

In the real world, no big deal.
Since forever I used 100k to ground at the input differential leg and 10k as NFB from speaker out to negative keg and my typical offset is around 40-50 mV so I never bothered to correct it.
So you are fine.

[J M Fahey]

I lost my Wife last year And 20 years earlier she lost her son to suicide, she carried on but it left a mark on her outlook on life.
Yes the things that life throws at us can be soul destroying.
So I have some understanding of your great loss.
Phil.

Ouch!
Hard blows for sure but hey, we must keep playing no matter what cards does Life deal us.
What else? 🤷🏻

[phatt]

Thanks Juan,
            At least I have several recording of my wife singing that we recorded some years back. I'm so glad that I persuaded her as she was a trained singer with a unique tone and range. I was able to play one of her recording at her Funeral which got a huge response.
Now I just sing at open mic jams, the music keeps me sane.
Phil.