Can anyone help me figure out why my '72 50 watt has so much more gain than my '76 50 watt?

Maxbrothman

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No not really, providing your using the same set of tubes for each amp and they're all biased to the same dissipation. What you'd probably hear would be a slight difference in character between some of the amps due to PT and OT wind tolerances.
I thought one reason for a PCB circuit was consistency and that hand-wired point to point could have breakup happening on 6 with one and 7 on another.
 

Pete Farrington

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PT and OT wind tolerances.
I think the usual resistor ‘tolerance to nominal’ used in most amps up until the 90s is 5%, caps will be 10% at best, 20% more likely.
I suspect transformer winding ratios will be at least 5%, maybe better.

I thought one reason for a PCB circuit was consistency and that hand-wired point to point could have breakup happening on 6 with one and 7 on another.
I think you may have unrealistic expectations of the consistency of pot tapers.
The pots used in guitar amps are cheap crap really, tapers are untoleranced, could be anything.
PCB consistency advantage will be in regard of very high frequency response / stability.
 

TAZIN

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I thought one reason for a PCB circuit was consistency and that hand-wired point to point could have breakup happening on 6 with one and 7 on another.
PCB's just made it cheaper and easier for Marshall to produce their product. If you removed the components from a PTP board and put them into a PCB the amp would/should sound the same. Marshall used good quality resistors & capacitors back then which "by themselves" would produce consistent results. Aside from valves/tubes, the components which tend to create "variables" in tone/sound would be the transformers due to their manufacturing tolerance and the potentiometers to a lesser degree. I mention potentiometers since the ones Marshall used were along the lines of 10% - 15% tolerance and Marshall was notorious for using Logarithmic pots instead of Linear for the Middle & Treble controls frequently. Log pots will give the Eq network a different curve (or sound) for a particular dial setting compared to a Linear pot. Another thing that cannot be ruled out regarding potentiometers is whether Marshall received Log pots for their Volume & Bass controls that had different taper percentages. A pot with a 10% taper will behave differently than one with a 20% taper.

Anyhow, boutique amp builders such as Germino, Suhr, Friedman, etc., are able to control component types & tolerances which is why their able to create products with tone/sound repeatability.
 

TAZIN

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I think you may have unrealistic expectations of the consistency of pot tapers.
The pots used in guitar amps are cheap crap really, tapers are untoleranced, could be anything.
I see we were thinking along the same lines. Actually the CTS/AB pots were of good quality but Radio Spares (supplier) just gave Marshall whatever they had on hand.

I suspect transformer winding ratios will be at least 5%, maybe better.
I would have thought closer to 10% tolerance per finished unit. That's taking into account vendor supply tolerance on the raw materials.
 

RWMusic

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Sorry I should delete this, not into the whole "interwebs" drama.

Just saw he had made a post at another forum that was................. less than positive regarding his treatment here.

Being a loyal M. F. er I wanted him to know at least one of us saw the derogatory remark he made concerning our membership and how he was treated in this thread.

So, I calls 'em as I see's 'em.

Wouldn't shock me if that remark has been deleted. He was just trying to impress the "cool" kids. Lol

Nothing regarding you @neikeel , you sir, a true gentleman and all my interactions with you have ended with me knowing more than I did before! You are very generous with your knowledge, and time I know my forum bro.s and I sure appreciate your sharing of your valuable time and knowledge.

Man, people are taking stuff way too seriously. It's just some questions about a couple of old guitar amps.

When the first few replies are people basically telling me they are too busy, learn it yourself, or in other words 'pound sand', or trying to scour post history to try to get one over on me and catch a contradiction, how do you think that will be perceived?

I got the answers I was looking for at TGP with no drama and in an easy to understand way, with followup questions answered. Much better experience. It shouldn't be difficult.

and @Pete Farrington That post about the '76 was made before I even owned the '72. It was true at the time, but after getting the '72, I noticed the drastic difference in amount of gain. What I thought was decent crunch before paled in comparison. Not sure what you were hoping to achieve with that reply. Wasn't very helpful, and was pretty rude. In fact it's not the first time you replied to one of my threads with what I took as an attitude. Not sure what that's about.
 

Seanxk

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Man, people are taking stuff way too seriously. It's just some questions about a couple of old guitar amps.
You came to The Marshall forum, we take Marshall's seriously, to TGP yes they're just old amps.
When the first few replies are people basically telling me they are too busy, learn it yourself, or in other words 'pound sand', or trying to scour post history to try to get one over on me and catch a contradiction, how do you think that will be perceived?
It's not going to be just one component as was said, but you know that now don't you?
I got the answers I was looking for at TGP with no drama and in an easy to understand way, with followup questions answered. Much better experience. It shouldn't be difficult.
It's a good job one of us is over there then......but I'm not going to ask why are you still here?, because I think you should stay, you've got some great amps ( serious amps actually ) and there's plenty more to learn.
 

RWMusic

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Not looking to stir up crap to be honest. Was just trying to get more info on what I have.
 

playloud

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and @Pete Farrington That post about the '76 was made before I even owned the '72. It was true at the time, but after getting the '72, I noticed the drastic difference in amount of gain. What I thought was decent crunch before paled in comparison. Not sure what you were hoping to achieve with that reply. Wasn't very helpful, and was pretty rude. In fact it's not the first time you replied to one of my threads with what I took as an attitude. Not sure what that's about.

Sorry to prolong the spectacle, but choosing Pete as a target for criticism is just bananas. It's probably no exaggeration to say his generous and patient advice saves the forum membership several hundred dollars a week in averted repair fees (if not more).

Mother Theresa and Gandhi should count themselves lucky they weren't able to join the forum in their time!
 

Pete Farrington

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I would have thought closer to 10% tolerance per finished unit. That's taking into account vendor supply tolerance on the raw materials
My thinking is that equipment manufacturers have to deal with the constraints of the +/-10% limit on the valve heater voltage, and mains voltage variance which might take up most, if not all, of that slack. Hence that doesn't leave much margin for deviation from the nominal, loaded secondary voltages on the power transformer, for the heater winding at least. And unless there was a significant surcharge, it would be normal to specify the same tolerance on all secondaries.
Plus mechanical turns counters are pretty simple things which I suspect have been around for a long time, so achieving tight tolerance of the transformer winding ratios shouldn’t ever have been a big deal.
And by the 50s, copper wire and silicon steel production should have been under good control, in regard of supplies for higher end gear at least; it's not like the manufacturers of the guitar amps we're interested in were buying bottom of the barrel parts.
So I don't see a problem with either the manufacturing materials and process in achieving a loaded voltage tolerance for PT secondaries much tighter than 10%.
Rather a 2% tolerance seems like it should have been a reasonable expectation for a long time, eg https://www.hammfg.com/files/parts/pdf/291KX.pdf
and @Pete Farrington That post about the '76 was made before I even owned the '72. It was true at the time, but after getting the '72, I noticed the drastic difference in amount of gain. What I thought was decent crunch before paled in comparison. Not sure what you were hoping to achieve with that reply. Wasn't very helpful, and was pretty rude. In fact it's not the first time you replied to one of my threads with what I took as an attitude. Not sure what that's about.
Sorry for any offence, I was hoping you would provide clarification regarding the apparently contradictory descriptions, thank you :)
 


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