Best 50w marshall OT?

[daz]

Aside from MM and heyboer, is there a marshall style OT thats known as very good that will give my heyboer equipped el34 50 watt a smoother more relaxed hi-mid to treble? The heyboer is the only common element left after changing everything in the amp at least once, and i really don't think they're good for this type of build. Both amps i built have a certain voice that has not changed no matter what i do and they both have the heyboer OT's in common and nothing else. So i'd like to try a OT made for marshall 50 style circuits that is a known good OT. MM is out because i've read horror stories about thier CS, plus thier prices are high and it's too big a loss if it happens not to help.

[Russ]

daz,

Hamond is now making guitar OTs. A marshall 50w is I think 75$ at antique electronics.
Don't know what they sound like, but Hammond has a pretty good rep with the rest of their products.

[daz]

Yeah, hammond is ok i guess, but i really want to know what is a known very good OT for a marshall 50. Otherwise i could just choose anything. Thats the point of the post. For example, there was one called OEI from i believe obsolete electronics that was supposed to be very good from what i read in old posts here. But they are gone now. Gotta be something people have found since then thats known to be very good for this type of build.

[Chuck H]

Well, other than MM and Heyboer there are some really custom hand wound jobbies, very expensive. There is the new line of replacement units by Hammond. Theres regular Hammond off the shelf units. Theres the Marstran unit. Supposed to be good.

The rub is that tone is subjective. Every time I see this discussion here it ends up the same way. A few responses from posters talking about the OT THEY used and they like their amp. But no real meat like "the MM sounds different in THIS way from the Heyboer. There was once a Marshall OT shootout conducted by some SF bay area members back when this forum was on the old format. I don't remember the outcome (or even if it actually happened) but you might check the archives. FWIW OEI probably would have won that shootout. But sadly, I don't think they're in business anymore. If you can find an OEI OT (good luck with that) they were universally considered THE Marshall replacement OT.

There are other much more affordable options. Consider that some TW Express amps were built with a regular Stancor A-3801. And that the original Marshall OT was just a Drake off the shelf unit. I built an incredible sounding 2X EL34 amp using an OT I pilfered from an old The Fisher 500B. (it was a stereo unit so I have one more of these OTs, but no ones getting it)
So it is possible to experiment with off the shelf and salvaged OTs to find what your after. The worst that can happen is that you'll probably end up with 4 perfectly good OTs for the same price as the MM unit. Other than the work to install them, it's really an adventure worth taking, tone wise.

Chuck

[daz]

I know it's subjective and all. But just considering typical marshall, say jcm800 tone, i want something that will closely resemble that tone all else being equal. i believe my heyboer is not a good OT for that sound. they may be great OT's, but not for that IMO. I believe this because other than that i have tried everything else, and i've used 2 different heyboers that both have that same sound. And more than that, someone elsewhere described the exact same sonic traits in HIS marshall build using a heyboer. So i'm not so much looking for a killer OT, but something thats going to sound at least as good as the original OT's they used for the 800's with the same traits. i realize that unless i built the amp exactly in all other respects it will never sound exactly the same. but thats not my goal. My goal is for it to sound like it does now but with the smoother mids and highs and tighter bass that the 800's had compared to what i get with the heyboer. But the fact that someone described what i'm getting to a T when marshall production circuits never sound like this tells me that i very well may be onto something here. so i want a very good marshall OT. preferably what would be an UPGRADE, but if i can't have that at least an equal.

[HTH]

Marstran make a JCM800 OT repro, check them out (as do Mercury Magnetics).

[dai h.]

personally I think the JCM800 50W OTs suck, but you should probably get one if that is what you like. FWIW, as far as I know (early) OEI and Marstran transformers were/are from Heyboer and they were meant to sound like the earlier ones not the JCM800 era ones. My JCM800 50W OTs (from my 4010 and 2204) sounded the same as the newer "784-139" 50W replacement from Marshall (the one with the silver coloured laminations). I assume the amp in question is a clone, and in that regard I would also look into the build (i.e. what is different from what you're trying to clone).

[Steve Conner]

While we're on the topic, did you notice the presence control behaving differently to your previous Marshall builds? Maybe it's time to start playing with the NFB resistor, the tap you take NFB off, even the value of the compensating capacitor between the PI plates. Some tweaking of your NFB loop could maybe get you where you want without having to shell out for a whole new OPT.

[daz]

Like every other place in this amp, i have tried every reasonable value in the loop. At this pint the amp sound very good, but thats with a 100k R across the treble pot. It works well to smooth out the sound, but it is a bandaid that masks (and not 100%) a issue. That issue i have come to believe is the heyboer OT. I've built 2 amps with heyboers and even have a 3rd heyboer and 1)-they are the only things in common and that hasn't been swapped with other values/designs/etc, and 2)-both amps displayed this same tone, and 3)-i never seem to hear of anyone using heyboers for marshall style high gain preamp builds. It makes no sense to me at this point that there could be any other reason. You guys here have helped me with both amps forever and told me uncountable things to try after i posted probably 10 different schematics. It left everyone here, AND at several other forums where i also asked the same things puzzled.

[Chuck H]

Just a shot in the dark here. But if your having the same trouble with a couple of different amps then it's fair to consider anything else they may have in common besides the OT. Do you use the same speaker cabinet with these amps? Speakers will certainly make a huge difference. If you have two similar amps and both sound "wrong" somehow, it could be that the cabinet your plugging them into is just not suited to that style of amplifier.

Chuck

[daz]

The OT is all thats left in common besides the PT.

[dai h.]

also the builder

[Rick Erickson]

Dai - you're killing me.... I had the exact same responses as I was reading this thread. The JCM 800 transformers were not "quality" units at all compared to the OEI's or the Mercury Magnetics. Heyboer has been making good transformers fora long time and is a well respected name brand. Hard to believe they could make a stock JCM circuit sound any worse. Perhaps it's just bringing out the amp's true character. Is Joe still selling the OEI's? I haven't heard from him in years. I've used his 50W OT's and his AC30 OT's with great results. I probably have a couple of those "rare original" JCM OT's kicking around from the swaps. I always offer parts back but many customers just tell me to keep them.

RE

[dai h.]

yeah, this...

the smoother mids and highs and tighter bass that the 800's had compared to what i get with the heyboer

seemed to be the opposite of what I experienced going from the stock JCM800 OT (harsh highs and mushy lows--even after many hours trying to tweak the circuit) to an OEI (clear highs, tight lows), so that did strike me as strange.

As far as Joe, there was a thread with some info a while back and from what I remember he is (unfortunately) no longer in business selling OTs (but he did have some stock remaining--someone may have listed an email address for him). His Kiwi (as in New Zealand) OEI partner Simcha Delft is apparently still offering handwound versions with different core material (IIRC).

[daz]

Maybe you never played a good 800. I had a number of them and i agree with the mushy sound and all that. Especially after they warmed up for a set. BUT< they didn't all have the same trannies and some of the earlier ones that didn't sounded great with none of those issues. I had both and the difference was nite and day. However, that said, even the "bad" ones had a good smooth sound like i described compared to how the heyboer sounds, and while you site my lack of knowledge as the reason, you don't know me and theres a lot more to making an amp sound good than just being knowledgable. I'm proof of that because at this point it sounds better than most of not all marshalls i've owned. my only complaint is it's different in a way i don't want it to be. Nit picking if you will. You people know a lot more than I do technically, but it's also about being smart enough and intuitive enough to make up for what you don't know to arrive at your goal using you people and every other resource i could think of. You call me an idiot in so many words, but somehow this idiot built a pretty good sounding amp....no, far more than pretty good. Suprise suprise. But you just assume that when i ask about sonic issues that i'm saying the amp sound like crap. Not so. Who here doesn't try to achieve perfection? Maybe instead of insulting me you could act civil and either try and help or just remain quiet. thats how i am with others, but then i have consideration for others.