Output transformers and overall amp tone

[Guitar Coach]

I am wanting to learn about how output transformers effects the tone of a guitar amp. I'm not referring to whether certain manufactures or brands of transformers are better and produce better tone (not trying to fan any flames). But the difference between say a Fender twin output transformer and a Marshall Super Lead 100.

I am curious as to what and how different specifications of transformers differ and what that does to the overall tone that the amp produces.

I am new to amp building/modifying, so if this has already been addressed in other threads please point me to them. Thank you.

[selloutrr]

Some reading material

http://www.geofex.com/Article_Folders/x ... former.htm

http://www.tone-lizard.com/transformers.html

[Guitar Coach]

Thank you.

[renshen1957]

I am wanting to learn about how output transformers effects the tone of a guitar amp. I'm not referring to whether certain manufactures or brands of transformers are better and produce better tone (not trying to fan any flames). But the difference between say a Fender twin output transformer and a Marshall Super Lead 100.

I am curious as to what and how different specifications of transformers differ and what that does to the overall tone that the amp produces.

I am new to amp building/modifying, so if this has already been addressed in other threads please point me to them. Thank you.

Hi,

Both Fender and Marshall have used various manufacturers for Output Transformers over the years. Compared to a Hammond Transformer for 100 Watt amp the size either transformer is undersized in dimension and weight by comparison with a narrower bandwidth.

The circuit used is part of the equation. The Twin's circuit does not exceed the bandwidth of the Transformer and would be considered completely adequate. Most Twin buyers and players are not known for their distortion playing, usually the Country, Western, and Jazz, in short basically loud and clean. (The exception was Jimi Hendrix. He recorded some his earlier Experience singles with a maxed out Twin, some with a Tele.)

The Marshall transformer isn't likely to be used cleanly, most likely it is going to be abused (if the venue will allow it, or if used with a power brake, etc).

There are some who will tell if you only switched transformers, (from Twin to Marshall Super Lead 100 and vice, verse) you wouldn't notice much difference. Or a replacement that had the general specs wouldn't be noticed.

On the other hand there are some who say there is an audible difference between Marshall transformers: Vintage, New Marshall, modern blue printed reproductions using updated methods (plastic bobbin and insulation), modern blue printed reproductions using vintage hand winding methods (paper wound), and modern transformers with similar specifications sold such as by Weber made in China.

On the subject of Paper VS. Plastic, http://www.classictone.net/PaperVsPlastic.html

There are other factors, the speaker cabinet (combo, open back, closed back), the speakers (wattage, manufacture, type of cone, dust cap).

The original 5F6-A Tweed Bassman was cloned by Marshall to produce their first amps. Both amps initially featured 5558 tubes, but the Marshall was built as a head with a closed cab with lower voltage celestion speakers. The Radio Spare output transformer had a different primary than the Fender. However the vintage Marshall head with a 4X10" open back alnico Jensens in the speaker cab wouldn't sound much different than the variation between individual units of vintage Bassmans. If the one example of the Fender Tweed Bassman which was custom built as a head was placed on a Marshall closed back Cab it would sound similar to the original Marshall Product.

There are some differences. The Marshall was built with an aluminium (English Spelling) chassis as opposed to the steel Fender used, the caps were by different mfgs, the resistors were different mfgs, however the basic circuit is similar with 1 or 2 exceptions is identical.

Fender did produce Head and Cabs (based on the Twin Reverb, initially without the Reverb) in its CBS era, Big Brother and the Holding Company used these and played them loud and pushed by pedals, too. By this time the Fender's Tubes were 6L6GCs, the tone stack had been moved between the 1st and 2nd preamp stage, etc. Marshalls had used briefly the EL37 (UK version of the 6L6) KT66 (another 6L6 tube without the Kink) and finally settled on the EL34. Along the way the amp was made brighter and brighter for lead work. Apples and Oranges by this time.

So to answer your question, the OT is part of the equation, with circuitry, speakers, output tubes, and amp configuration. The transformer will make a difference, how much difference depends on the above.

[Guitar Coach]

Thanks for the response. I'm just starting to learn about all the different parts that go into guitar amplifier tone.

What I'm asking more specifically is how does the output transformer equate into the shaping of amp tone. I've read post in which people talk a switching the transformers in their amps to "big iron" transformers to modify there sound. I'm Guessing this is can be related to switching tube types in an i.e. 6l6 or el34.

I know this is still an open ended question. Thanks again for your response.

[renshen1957]

Thanks for the response. I'm just starting to learn about all the different parts that go into guitar amplifier tone.

What I'm asking more specifically is how does the output transformer equate into the shaping of amp tone. I've read post in which people talk a switching the transformers in their amps to "big iron" transformers to modify there sound. I'm Guessing this is can be related to switching tube types in an i.e. 6l6 or el34.

I know this is still an open ended question. Thanks again for your response.

Hi Guitar Coach, a larger Output transformer (in size, with the same primary and secondary specifications) will have a wider bandwidth (better bass response, extended treble). There may be a more effortless or unrestrained tone or sound.

The flip side is most of the classic records were recorded with the limitations of the bandwidth, undersized transformers (compared to Hi fidelity Xformers), lower grade Iron, transformers employed with more than the normal design specification pushed through them, cores with DC saturation, and the results, warts and all, became our references and tonal Icons. Fender Clean, Plexi distortion, Vox sparkle, etc.

The Vox AC30/6 OTs (there were more than one Albion, Woden...) are roughly the size of the Hammond 125E OT which is rated for 15Watts. Compare the size with the original AC30/4 Radio Spare transformer (which was also in the some Marshalls such as the Bluesbreaker) with the later evolved AC30s. Quite a size descrepency.

Most traditional Guitar Amps are not very wide bandwidth as one is playing a bass instrument (yes, a Guitar would be considered a bass instrument comparable to say a violincello) through a woofer (bass speaker) and the predominant amount of tone is at the midrange area. Also the design parameters were for cleanly played instruments. A louder sound of an Acoustic Guitar to play with Big Bands, in larger venues for Country Players and Jazz players (with other band members). Fender and Ampeg were late to make changes in their guitars during the British Invasion (Ampeg's Hall, "Rock doesn't Swing," and Fender never could figure out distortion into the equation). The Major Canadian Companies, Traynor and Garnet (there are others) made guitars and basses to be played loud and clean for the most part (Garnet did have the Deputy (play on words for Marshall).

Slight digression, quiz, who had the first master volume on a production guitar? Traynor, 1962. If you said Marshall, they were the last, Fender had MV before the big M!

Back to OTs, This is not a plug, but check out how many different clones of original transformers Mercury Magnetic has for Tweed Amps. Sometimes a transformer was whatever was available from supplier or an alternative.

At lower levels (before distortion) the bandwidth of a smaller transformer is not a limitation, only when the amp is really pushed does the bandwidth markedly decreases and the signature sounds of an overdriven or distorted amp come into play.

In recent years big iron (larger transformer, wider bandwidth) has become popular, but not necessarily universal. Toroid OTs have become more common (savings in weight and size). However one can still achieve the iconic sounds with a few changes in caps or other modification to the circuit. A 60W transformer could be used in place of the anemic by comparison small OT in the Vox (if one could find the room).

One myth I would like to nip in the bud. That certain size tubes will provide so many Watts in a circuit. If there was sufficient voltage in the heater filaments, a Tweed deluxe amp would produce no more power with 6L6GC, EL34s (after a small wiriing change to the socket, or KT88, just different tones from the tubes and alot more heat to deal with.

Other factors such as plate voltages, OT transformer primary specifications, the current capabilities of the PT come into play as to how much power one can get from a pair (or Quad) of tubes.

Tubes and OTs interact, a 10W amp with 8k or 10k primary will just as easily accomdate a pair 5581 tubes or EL34 as a 40 Watt amp with an OT with 4k primary. That same 4K primary (and different voltage) was used by Marshall with KT66 tubes (quad) in the JTM45 100 Watt.

The EL34 does have a higher voltage rating for the plates and screens and could be used in a Traynor Bassmaster (another Fender Tweed Bassman descendant) and produces 80Watts with a 4k primary OT. A few circuit tweeks and mods on one could convert the YBA-1A into a Marchall plexi clone. The Transformer would be larger than the original 50 Watt transformer, which Dave Funk said is really more of a 35Watt transformer.

I know I haven't completely answered your question, as tubes being so variable and the interaction of the speaker through the OT and vice, verce.

There isn't a simple answer, just food for thought.


Best Regards,

Steve