What is the most aggressive transformer you could put in a superlead, and why in your opinion?

[Nickerz]

You know I've always found the SLO to be my favorite amp to play, but I've always felt, personally, that they sound off. There's something almost too creamy about it. So when I got an SLO preamp into a superlead style power section I found home. And now I'm in that dirty stage where you go from the 99% there and obsess over stupid 1% details. Personal preference obviously, but I've always felt like early hotrod JCM800s 2203s and older hotrod Plexis always sounded the best recorded with exception to some Bogners as well. As Marshalls have gotten more modern, I haven't found that they've gotten better IMO. They seem to have a touch more presence, maybe even some attack, but they're just not as ballsy somehow. Theorys about from metallurgy, to construction to specs etc. And so, I guess before I rip the heart out of an older Marshall for selfish dirty reasons... I wonder, is there another way. And if budget wasn't the concern, what heart you'd put in and why.

[brewdude]

Aggressive transformer?

[Nickerz]

For lack of a better word, yes. Mid forward, lots of KERRANG as they say. Chutzpa. This question obviously applies to people who don't believe that cheaping out on this is the best approach. Not that MSRP is the prime determinate of quality, but there are some people that will put the cheapest "close enough" spec'd transformer they can into an amp. I already have a good transformer, and now I want to try and take that just a step further.

[Roe]

I also prefer marshalls to SLOs. For good replica of the plexi transformers, consider Chris Merren or MArstran/Heyboer

[Stevem]

There’s a lot more then just having a power transformer or power supply with excess current to get that chunk and punch hanging in as you rev the amp out!

The amount of global feedback adds tremendously to how tight the bottom end stays, how high the high end goes and how low it will reproduce notes until you run out of it ( feedback ) once the output stage starts to clip.

Once the feedback starts to go dry the gain level starts to come up , the the overall frequency range narrows up so the mids start to get more pronounced and the low end will start to get flabby .

It can get expensive real fast to experiment with power transformers for the sake of auditioning ones with more voltage, current or both!

I would start out by going Xs two with the filtering on the first power supply node and then going 50% more on the screen supply node and then see how you like it for starters.

Output tubes such as Groovetubes EL34S in a number 10 rating can add up to 10% more clean power before they start to clip heavy, and they also have noticeably better bottom then Russian made outputs like Sovtec, Ruby And Mesa.

And keep in mind that if you have a 100 watt model you can install a London power 4 way adjustable bias circuit and try out a combo of 6L6 and EL34 tubes or 6550/KT88 and EL34 outputs to really fine tune in on what makes you smile!

One not terribly expensive way to get a bit of added current out of what you have now would be to install A separate Filament transformer to run the heaters off of .

Another great cost nothing experiment to try is to disconnect your amps feedback wire from the output transformer secondary and experience just how much gain the full amount of applied feedback removes from your amp!

[Nickerz]

I also prefer marshalls to SLOs. For good replica of the plexi transformers, consider Chris Merren or MArstran/Heyboer

Do you think there's any magic to older OEM transformers? Also looking into this a bit, it looks like the JCM vs plexi argument is something like brightness vs chewiness. I am looking for brightness, so in that regard might it make more sense to look for an 800 transformer or clone?

[Stevem]

If your looking for more top then lower resistance of the preamp section power supply dropping resistor to get more voltage to the plates, I mean atleast to the first gain stage.

[Roe]

I also prefer marshalls to SLOs. For good replica of the plexi transformers, consider Chris Merren or MArstran/Heyboer

Do you think there's any magic to older OEM transformers? Also looking into this a bit, it looks like the JCM vs plexi argument is something like brightness vs chewiness. I am looking for brightness, so in that regard might it make more sense to look for an 800 transformer or clone?

the 1959s and 2203s used the same transformers, but the transformers changed gradually. First nylon insulation was introduced and the voltages lowered somewhat. Much later there seem to have been some changes due to secuity measures and probably change of metal alloys. but many 70s and 80s transformers are perfectly fine

[Faze]

I owned a 1959 back in1970. The b+ was 560 volts. It could maintain clean to a point And brightness. On a resistive 8 ohm load I would measure 160 watts after doing the math with a lean sine wave on a scope. (Probably 10% distortion clean) I remember measuring later Marshall’s at 480 volts. They would sound good but not the same. The preamp distortion thing changed the quality in another sought direction at the time.

[Roe]

I owned a 1959 back in1970. The b+ was 560 volts. It could maintain clean to a point And brightness. On a resistive 8 ohm load I would measure 160 watts after doing the math with a lean sine wave on a scope. (Probably 10% distortion clean) I remember measuring later Marshall’s at 480 volts. They would sound good but not the same. The preamp distortion thing changed the quality in another sought direction at the time.

560v is to be expected from an early 1959, aka super 100 amplifier or jtm45/100. the later 1959s should have much lower voltage really, although some report voltages as high as 520-30v

[Gaz]

You didn't say power or output transformer, but I'm guessing you meant output. Personally I think this is a fool's errand (no offense), and that changing a transformer out for one you already think sounds fine and is good quality is a lot of effort and expense for an imperceivable difference in sound. I don't even think you could perceive at all without a direct A/B comparison.

That said, I take your tonequest seriously, and would play around with the NFB. You said that when you changed from SLO to SL power amp. Well, they are the same power amp besides the amount of NFB, so there's probably some more experimentation to be had there. You could also try a .47 or .68 presence cap like some Marshalls had. The SLO preamp itself has a ton to play with, and there could be a book written about the subject. In fact there's a whole forum started devoted to it: http://www.slocloneforums.com/viewtopic.php?f=6&t=6724

[pdf64]

560v is to be expected from an early 1959, aka super 100 amplifier or jtm45/100. the later 1959s should have much lower voltage really, although some report voltages as high as 520-30v

Is there a timeline anywhere for how things changed?

[Roe]

yes, here https://folk.ntnu.no/roef/JTM100.html

[roberto]

If you take a look at sloclone as Gaz suggested, you can find a project called Marsholdano that has been developed by Joey, BRBS and me 15 to 20 years ago.
It is an hybrid between Marshall and Soldano. You can of course move the lever to more Marshall or more Soldano as you like.

[Leo_Gnardo]

I owned a 1959 back in1970. The b+ was 560 volts. It could maintain clean to a point And brightness. On a resistive 8 ohm load I would measure 160 watts after doing the math with a lean sine wave on a scope. (Probably 10% distortion clean) I remember measuring later Marshall’s at 480 volts. They would sound good but not the same. The preamp distortion thing changed the quality in another sought direction at the time.

I think this observation has some relevance to the tone you're seeking Nickerz. Something I've noticed, others too, is higher voltage power supplies tend to make the signal processed through the amp's circuits sound brighter & more present. Perhaps that could be translated as "aggressive." And lower voltage supplies promote a more relaxed tone. I've noted before, the French translation of high voltage, haute tension (= high tension), which shows up at the B+ fuse holder as HT by coincidence. In any case it may serve you better, and much cheaper, to bump up the power supply voltage in the preamp and drive circuits rather than take the expensive and probably not very effective route of swapping out the OT. All it takes is a couple of resistors. Of course one could install a power transformer that would increase the overall B+ voltage in the amp, but I think that's not really necessary. A couple of resistors, or perhaps only one, paralleling the dropping resistors in the power supply may yield the tone change you're looking for. A cheap experiment, worth a try.