Best 50w marshall OT?

[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

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- [i deleted a few more analogies].
That said, any one part in a tube amp can overtly alter its character.

Sometimes a fresh opinion (or some time) can reveal a 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