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.

[dai h.]

jeez, relax. I'm not saying you are stupid, I'm just saying consider the possibility that it's what you did or did not do instead of blaming it on the perceived deficiencies of Heyboer OTs. I think it's pretty much a fact that differences in outcome can result from an amp (or a piece of electronics) being built by different builders. That's not voodoo or anything like that. You can have more control the more you know what is going on.

[daz]

I'm just saying consider the possibility that it's what you did or did not do instead of blaming it on the perceived deficiencies of Heyboer OTs

My point was that i DID do everything. Name it. Lets look at the NFB for example. I have tried changing most every component there to 3 or 4 values and tried the different combinations till i knew there was not better than what i eventually ended up with. I even did that several times because i felt when i change another part of the circuit that the NFB then might respond differently now ! Now consider that i did that with probably every part of the circuit. It's even been a totally different amp going from cathode biased/tube rectifier/no nfb to just the opposite of all those. This is what i've been trying to say....the OT is the only common part to the particular tonal aspects that are always there. OK, the PT too, but i can't imagine after voltages going up and down with cathode to fixed and tube to SS rectification that it would be responsible.

[mac1amps]

I'm really curious about this "terrible CS" you describe, referring to MM (I assume that you're referring to their customer service??). I've done a number of Mercury OT installations (along with "chokes"), all of which made a substantial improvement in the amp's overall response, touch sensetivity, string seperation, high-end definition (without harshness). This was done with Fenders, Dr. Z's, a (built) JTM 45, and RI Vox's. I WILL say that I wasn't that impressed with their upgrade "kits" for the Champ 600's, then again, how much TONE can you expect out of a 6" speaker in an open back cabinet (even if it's a Weber).
I've also worked with a lot of Hammonds, but NOT their new line of "drop-ins" (I''ve used their 1600 series on a few of my own Fenders, specifically a SF Vibrolux, SF Deluxe, SF Bassman [re-built to John McIntyres specs], and a Pro Jr. They ALL sound GORGEOUS!).
I get the impression that Hammond's new "drop-in" line are essentially "built TO specs", whereas their 1600 series seriously EXCEEDS the original specs (plus adds the convenience of multiple impedance taps).
My few experiences with the Heyboer transformers found them to be pretty much "generic" (i.e. UP to the specs of the originals, but not exceeding them)

[daz]

I refer not to my experience with them since i have none. I've just read negitive reports about their customer service over the years, and it seems more than typical. (because we all know every co. has SOME negitive responses) I must say tho they were quite friendly and nice pre sale. Of course that can sometimes turn 180 after the sale.

In any case, your experience with OT's is interesting. It sounds like you felt heyboers are not equal to MM iron. Thats something i've wondered about but it's hard to determine because opinions are quite varied. I think however that opinions on MM iron may be inaccurate due to the fact that they are so expensive i imagine a lot of people expect miracles, and when they only get great sound instead they become angry. Who knows.

[Steve Conner]

Well, when you think about it, I imagine it is possible for an OT to add a character to the mids and highs like what Daz experienced. They have stray inductances that start to do stuff and interact with your amp's NFB in that frequency range.

Also, the EVM12L's huge magnet couples it really tightly to the power stage, and I guess that makes it more sensitive to the choice of OT and the NFB loop than many other speakers. I got an EVM12L Classic reissue a while back and it was mainly the amount of bass damping that surprised me, but that damping must be happening at other frequencies too.

In a high gain amp, this interaction has to be got right, because you rely on it to soften the harshness of the raw preamp distortion. A hi-fi OT will reproduce the top end flat, just as it comes out of the preamp. A cheesy guitar one will filter out the highs, and the NFB may even interact with this to make a peak in the upper mids before it rolls off. Maybe that's what's happening in your case, I don't know. Maybe Heyboer never tried their Marshall OT in a JCM800 circuit with an EVM12L, and would have hated it if they did.

Bear in mind that in guitar tone there is no "right" or "wrong", so it's impossible to define the meaning of "upgrade" or judge one part as "better" than another. You need to find the tone that's right for you, and yes, a Mercury Magnetics OT would probably make a difference. If it doesn't, at least it'll be easy to resell because of their reputation.

[daz]

I'm not worried about having to sell it if i don't like it because they have a return policy based on the customer being happy with the improvement. Tho this would be a huge pain to do. But no loss if i don't like it.
By the way, the OT isn't a marshall replacement by heyboer. It's just a heyboer that i asked for with na 4 k primary at 50 watts. Thats what they wound for me. Maybe theres some other spec thats not good in this type of amp, but those are the only specs i knew to ask for. Initially i was going to use it for a 4xEL84 amp then changed my mind to a 2xEL34 or i'd have asked for a 3.2k ala marshall. Don't know if that has anything to do with it, but i doubt it because i've tried other taps to see what they do to the tone and people have suggested in the past to me that it doesn't matter.

[Steve Conner]

Oh, well there are about 10 other specs beside the impedance and wattage that you need to get right to make the transformer an accurate clone. Nobody ever publishes them, it's kind of like the secret recipe for Coke.

So if you didn't ask for a Marshall OT, it's not surprising that you got one that doesn't sound quite like a Marshall OT. Even then, there were several 50 watt Marshalls all with different OTs. If you tried swapping the OTs between a Plexi and a JCM800, you'd get a surprise, probably on account of the Plexi owner chasing you with a kitchen knife :D

Out of interest, did you ever try getting an actual replacement JCM800 OT from a Marshall/Korg dealer?

[daz]

probably on account of the Plexi owner chasing you with a kitchen knife

LOL!!

So if you didn't ask for a Marshall OT, it's not surprising that you got one that doesn't sound quite like a Marshall OT

Hmmm......i guess i could be on the right track in a big way in considering a MM plexi OT then.

Out of interest, did you ever try getting an actual replacement JCM800 OT from a Marshall/Korg dealer?

No, but i never really was interested in getting an exact JCM800 sound. What i meant when i used that as an example was more to say like a high gain marshall sort of sound. And a 800 seemed like the best example to use because the rest of the high gain marshalls are jam packed with more SS devices than an electronics store. Thats not to say i don't like any of those, but a JCM800 without channel switching is about the highest gain preamp in a marshall w/o SS devices i know of. So i was really just trying to suggest that i'm not after the cranked output sound, but a marshall high gain pre on a very good sounding marshall 50 watt output section sort of affair.

[HTH]

Speaking of Mercury Magnetics' customer service, I can only report what I've found and that is some of the best customer service I've experienced. I had some trouble with oscillation using one of their OT's which turned out to be my own silly mistake, but they helped me through it anyway.

I've used their MMO-100M (optimized for 6L6/KT88/6550), their O45RS-L (Bluesbreaker repro) and their Epi Valve juinor kit. All surpassed my expectations, expecially the RS one which is an amazing piece of work.

Having said that, they are very harmonically rich and you may find them too toppy - they do take a while to break in and the tone does change alot during this time.

So, my original suggestion of a Marstran unit would stand, I think they would be your best bet.

[daz]

Well, i told Patrick at MM about my amp and that there was too much high end and that i wished it were a bit less so and smoother. He recommended the plexi OT because of that. So if they are correct it shouldn't be toppy like your MM OT's were. even if i consider a marstran it would only be after trying a MM because of the satisfaction return policy MM has. May as well try that first, otherwise if i'm not happy with the marstran i'd be stuck with it and kicking myself for not trying the MM first.

[OverDriven]

I thought the JCM800 and Plexi transformers are the same. Companies like Hammond have the drop in replacement for JCM800 and Plexi listed as the same part number.

[Rick Erickson]

[Companies like Hammond have the drop in replacement for JCM800 and Plexi listed as the same part number.]

That doesn't mean the originals were identical, just that you can put a replacement transformer in either amp and it will meet the basic spec. requirements for impedance and power output. Original tone is not usually guaranteed in generic replacement parts.

RE

[Guitarist]

I know of one designer, Wizard amps, that seriously gets hyped (citing the mids) about OTs.
They're like the lens in a camera- .
That said, any one part in a tube amp can overtly alter its character.

Sometimes a fresh opinion (or some time) can reveal a [I]block. I am sure that many know the frustrations that arise working with music amps. Hey, I have a shelved Hiwatt due to this. I know it isn't the transformers ;).
I think every amp should be minorly customized to it's player.

Would you feel OK with sharing some pics of your amp? That might help.
What kind of treble cap do you use in the tone stack. Ceramic I hope. How much pF are you bleeding out of the single path? Do you wire the V2 swapped to accept a 12DW7?

I hope those new Hammond transformers kick a~~. They have been out a while so we should have some more opinions...

[Chris - CMW amps]

I thought the JCM800 and Plexi transformers are the same.

As example post '66 50 Watts Marshalls OTs; transformer-code is always the same, size and weight too but (let's say) a '67 one does sound completely different than the "same" Drake from (let's say) '70 or '83.

[CarlZ]

What I have historically found is that in most amplifiers, some very critical parts such as the transformers have some of the worst tolerances of any component in the amplifier. Most trannies are wound during production runs on the order of +/- 20%. That's a TON and can make a huge difference from amplifier to amplifier. It's not impossible and is actually quite likely that two of the same tranny from the same mfg will make an amp sound completely different.

Aside from outputs; power supply voltages, capacitor and resistor tolerances, variations in preamp and power amp tube characteristic curves, and a host of other variables can also cause two apparently identical amplifiers to sound completely different. And as the gain of the amplifier increases so does the sensitivity of the amplifier to the aforementioned variances.

Up until the age of the internet, very few people would even consider buying a guitar amp "blind". We'd go to music stores, plug in and play a couple of the same amplifier. One would sound like ass and the other godlike. It's the nature of the beast and as a builder what you generally need to do is find transformers that function at least close to what you're looking for and start performing small tweaks to the circuit. Sculpting the tone to exactly where your ears want it and let the chips fall as they may. Its a difficult and time consuming operation that really requires experience and patience to get right. And if somebody isn't willing or able to do that then they're probably going to have to settle for an amplifier that's about 90% of where they want it to be.

Well, that's my two cents on the subject and feel free to take it for what it's worth.

-Carl

[daz]

I hope those new Hammond transformers kick a~~. They have been out a while so we should have some more opinions...

Hmmm....which ones are new? Is the 1750N i'm considering new ?