Transformer Placement and the Effect on Tone....?

[caphead]

I figure I'll ask you Trainwreck guys about this considering Ken Fischer was well known to put the power and output transformers very close to one another......

I am in the process of putting together a Marshall style amp (multi channel with some hi-gain sounds) which I am aiming to have the feel of a 66-67' era Super Lead with lowish filter values and period correct chassis arrangement. The one notable aspect of these early plexi's was how the transformers were placed on the chassis; much closer together than the latter era Marshall's. So my question to all you guys who have experience with this type of arrangement is that if there is a noticeable effect on the tone, feel, response, ect. in comparison to other more conventionally spaced transformer layouts? And on the contrary what are the risks; noise, stability issues, otherwise?

Me personally, I have unfortunately never really experimented with this, the obvious reason being how hard it would be to build an amp first then install it's output transformer afterwards, lol! The closest direct observation I have on this is in fact doing the opposite; placing the transformers as far away from each other as possible. What I noted with that amp was a sort of 'thin-ness' to the overall sound, though many other factors could have contributed to that.

Any first hand experience with this would be great to hear about; thanks everyone!

[xtian]

I can't imagine how you could influence the end "tone" of the amp by transformer placement, other than by making it worse due to the hum you can introduce by POOR placement.

Read up on the "headphone trick" for transformer placement and orientation. You can literally listen to the results as you move and rotate the PT and OT in relation to each other. It is possible to place the two transformers right next to each other in such a way that no extra hum is induced in your circuit.

[caphead]

I can't imagine how you could influence the end "tone" of the amp by transformer placement, other than by making it worse due to the hum you can introduce by POOR placement.

Read up on the "headphone trick" for transformer placement and orientation. You can literally listen to the results as you move and rotate the PT and OT in relation to each other. It is possible to place the two transformers right next to each other in such a way that no extra hum is induced in your circuit.

I certainly am no stranger to transformer placement for reasons of space and noise rejection. While I've never done the headphone trick, I've usually done a sufficient job of placement using a ruler and pencil. My question is if there is any noticeable change in the actual sound (noise aside) as the output transformer is moved around? I remember reading a while back that Ken Fischer used to do this before actually bolting the OT to the chassis. This of course could have been speculation, misinterpretation and/or hearsay as everyone knows how 'facts' are distributed through out the internet, lol!

Anyways though, see attached picture (I know it is a clone, but it is the clearest demonstration of the typical top side TW layout I could find). The way I see it, if transformer placement does not effect tone at all, what would be the point of arranging the transformers in such an inconvenient manner? Having both transformers being mounted on the left hand side of the chassis doesn't really make for a stable platform when building and working on the actual electronics. There has to be a point of why they are where they are and not for example even slightly more spaced out so that the power tubes don't have to double as a kick-stand when you need to take it out of it's head shell

[geetarpicker]

I remember talking to KF about this exact subject. He thought the orientation and close proximity of the OT to the output tubes made a difference in the early plexi 100s. What difference I can't recall...just that he thought it was part of what gave those amps their character.

[geetarpicker]

Maybe the placement of the TW transformers started out as a way to keep the noise down by keeping the PT as far away from V1 as possible. Also perhaps such a high gain amp is more apt to be stable with the OT also as far as possible from the preamp. Maybe that was more the priority over the slight AC hum coupling of having the transformers close to each other.

[martin manning]

Maybe the placement of the TW transformers started out as a way to keep the noise down by keeping the PT as far away from V1 as possible. Also perhaps such a high gain amp is more apt to be stable with the OT also as far as possible from the preamp. Maybe that was more the priority over the slight AC hum coupling of having the transformers close to each other.

I'm inclined to agree with this line of reasoning. Also, a 2204-ish amp with TW transformer placement that I built sounds very good, and does not have any induced hum, in spite of its having only 1/4" between the OT bell and the PT lams.

[sliberty]

I remember talking to KF about this exact subject. He thought the orientation and close proximity of the OT to the output tubes made a difference in the early plexi 100s. What difference I can't recall...just that he thought it was part of what gave those amps their character.

But he also claimed that wire insulation color was significant

[Blackburn]

I remember talking to KF about this exact subject. He thought the orientation and close proximity of the OT to the output tubes made a difference in the early plexi 100s. What difference I can't recall...just that he thought it was part of what gave those amps their character.

But he also claimed that wire insulation color was significant

Yeah, but that one was just to screw with people.

[caphead]

Thanks for the responses guys; this was exactly the sort of feedback I was hoping for asking the Trainwreck forum as opposed to any of the more technical ones. Ken Fischer's methodology sometimes did defy 'logic', but it cannot be argued that the end result of that effort was superior for it. I'm glad the information I heard about Ken's philosophy on transformer placement turned out to be based on fact, this has provided me with the confidence to experiment with the concept.

Perhaps the logic was to keep the OT as far away from V1 as possible to reduce all possibility of it picking up stray noise, which absolutely makes sense, but I can think of many modern hi-gain amps (like newer Marshalls for example) that put the OT and PT on opposite ends of the chassis; with the OT being right in the neighborhood of V1. It seems KF's logic was that of the sound and/or feel being superior to more conventional arrangements. Afterall Ken started off modding old Marshalls, so I can perhaps assume this is where that methodology could have originated.

I am at the point in this amp project where the transformers must be bolted to the chassis, so I will do the headphone trick to find the most noise free positioning whilst putting them as close to one another as I can. I would really like to perform this step after the amp is built, but unfortunately I would have to remove the internal boards and risk getting metal shavings everywhere to do it. Does anyone have any tips of how to experiment with transformer placement after an amp is assembled?

[Blackburn]

And to the OP, just place them as conveniently as possible and keep the noise down to nothing if you can. I'm fairly certain that with the standard tranny configuration in wrecks it is impossible to get zero noise. However, the lowest I've been able to achieve is 3 or 4mv and I don't believe it is remotely perceivable over any preamp noise or even when in standby and also don't believe there is any effect on the tone. Even with severe 60 cycle hum I haven't noticed any impact on tone. Just my $.02

[caphead]

So I did the 'headphone trick' and I am absolutely stunned at it's results....... It turns out that the arrangement used by Ken Fischer is the quietest position, despite both transformers being within inches of each other! This arrangement was pretty much as quiet as placing the OT far from the PT. Unfortunately I already placed my (vertical mount) power transformer in the traditional place, laminations facing front and back, placed at the far left of the chassis, roughly center; so thus it will be very hard to re-arrange it since I've already wired it to the mains supply. A solution for anyone who would like to take advantage of this arrangement without putting both transformers on the same axis could in theory orient the power transformer so that the end bells face front and back and then the output transformer (oriented of course laminations facing front and back) could then be moved pretty much as close as one would want.

[Plexified]

this is a great question and one that is of some really heavy tech . Once you start to dig around a bit in hi fi design you can learn some of the design parameters that cause an effect on the tone . I guess if you think of the design plane as three dimensional you can imagine the effect of magnetic radiation on the surrounding components . Crazy as it sounds because we design with what is perceived as colorization in tube guitar amps , hi fi designs for linearity and transparency . So the materials the power and output are made from effect the tone as well as its orientation and the impact on the parts around it ! Its a design tool to introduce the color or effect you wish to attain . Alot of design , forethought and experience become priceless . You can throw one side of a tube compliment some magnetic radiation and it really changes things in terms of symetry and balance . This is a very complicated subject with the engineers in the know passing on without the knowledge being extracted . When you design for linearity you know what takes away from your goals. We need all that knowledge to add more options to our color wheel . These minor options of design all stack up to add the distinctive color of the tone of an amp . The visual radiation map of a particular core of a transformer gives a good indication of what will be radiated upon for example . Just as an aluminum chassis reacts differently than a steel chassis in this sense . Like I said its pretty mind numbing and worth the time to investigate . Guys like Bob Wood and younger keepers of this torch like Andy Johns and Chris Merren can go on and on about the heart of the amp . Tim Tsang is another mad scientist talking about materials . Sourced from copper to the laminates to the winding tensions go insanely technical and its very hard to listen to changes here , cause its not like plugging in tubes . Fun stuff , but considering , I think the sensitivity of these builds exploits how important little stuff makes big results when stacked up . And btw the plexi is a great example , steel and aluminum chassis and multiple style transformers and layout with essentially the same circuit . Look closely at the physics here and you will be smiling as it becomes apparent when you can envision who effects who in the chassis zoo . Great topic !