cheap output transformers??

[yunger]

i frequently read suggestions of upgrading "cheap" ot's to improve tone. for instance, i built a homebrew circuit using a pro junior chassis and transformers. what would i gain by swapping ot's? what are we talking?? better bass response?? better note articulation??
i ask because i'm new to this and have no working experience. could someone enlighten me? thanks.

[mac1amps]

I've been working with a lot of xformer upgrades in the last few years, and yes it CAN be amazing, the kind of results you can achieve. I have one client that brought in a Dr. Z 1x12 (kind of an AC-15 knock-off), who wanted a bit more "headroom", and I eventually decided to add (2) additional EL84's to the output network, which meant it should have a new O.T. to accommodate. I ended up using a Hammond 1600 series xformer (which is, BTW a series originally designed for stereo/ hi-fi applications), and couldn't have been happier with the results. The low end was certainly improved. The high-end "definition" was also greatly improved, AND with significantly reduced harshness. All of the improvements were evident weather the amp was being used "clean", or maximum overdrive. My client ended up having a few of his other amp's trannys upgraded as well (obviously, he was also quite happy with the results). I've gone back and forth with Hammond as well as Mercury Magnetics transformers as well, all with gorgeous results. I also like the additional option of having multiple speaker impedance taps for maximum compatibility with alternate cabinets. I should also let you know that I did this procedure with a Pro Jr. of my own (as well as a SF Vibrolux, and a SF [modified] Bassman), with the same results. I WILL have to say that the improved results tends to be a bit more apparent with higher power models (20 Watts or higher), but still worth the effort IMO.

[defaced]

Check this out: http://unionjackaudio.com/transformers.html

[Bruce / Mission Amps]

The Mercury Magnetics OT sounded the most lifeless to me but to be honest the amp sounded like ass anyhow.

[Steve Conner]

Back in the day, there were basically two kinds of OPT. Expensive "full bandwidth" ones for hi-fi use, and reduced bandwidth for PA, musical instrument amps, table radios, and so on.

A full bandwidth OPT would be the kind of thing you'd find in a Williamson amp or whatever. They have plenty of inductance and interleaved windings, and the result is a bandwidth that comfortably exceeds the hi-fi audio range. (Williamson specified the behaviour of his OPT from 3.3Hz to 90kHz.)

A reduced bandwidth OPT basically skimps on everything to save money. Smaller core, less copper, fewer interleavings.

Now the thing is that the reduced bandwidth OPTs can actually sound better in guitar and even bass amps. The lack of high-end response acts as a filter to take harshness out of the tone, and the restricted low-end ends up generating distortion harmonics that fatten up the bass, and give the illusion of more bottom end. In an open-backed combo, this is actually better than undistorted bass output that would just rupture your speaker.

This is where it all gets confusing, as companies like Mercury Magnetics make high-priced boutique clones of these "classic" reduced bandwidth designs. You're paying more for less performance, on the grounds that it's exactly the right kind of "less" to improve your tone.

Hammond sell both full and reduced bandwidth types at reasonable prices. They used to say that their hi-fi OPTs were suitable for guitar, if you just picked the next size down, but now they have a range specially for MI use.

Orange recently brought out the Thunderverb 200 head, and their advertising bumf mentions that it has a "Full bandwidth output transformer" and is suitable for either guitar or bass. Patent pending, apparently.

[TD_Madden]

Hacked-up a Dr. Z?? whew.......

Why not just sell it and buy an amp that sounds the way you want it to?

[octal]

Why not hack up a Dr. Z? It's not an irreplaceable vintage amp or anything...
I'd probably scratch build myself if I found myself in that situation, but if you want a nice chassis, cabinet, etc and you already own a Z and have the coin, why not?

[octal]

Now the thing is that the reduced bandwidth OPTs can actually sound better in guitar and even bass amps. The lack of high-end response acts as a filter to take harshness out of the tone, and the restricted low-end ends up generating distortion harmonics that fatten up the bass, and give the illusion of more bottom end. In an open-backed combo, this is actually better than undistorted bass output that would just rupture your speaker.

This is where it all gets confusing, as companies like Mercury Magnetics make high-priced boutique clones of these "classic" reduced bandwidth designs. You're paying more for less performance, on the grounds that it's exactly the right kind of "less" to improve your tone.

Hammond sell both full and reduced bandwidth types at reasonable prices. They used to say that their hi-fi OPTs were suitable for guitar, if you just picked the next size down, but now they have a range specially for MI use.

Since the "full bandwidth" transformers are often ironically cheaper than the "high price boutique clones of restricted bandwidth transformers," I've been experimenting a bit with conjunctive filters. My amp so equipped sounds much less transistory and harsh than without. Most of the Hammond guitar amp line is specced to be +- 1 dB from 70Hz to 15K which is restricted compared to their hi-fi line I suppose, but still far too little high end roll off to reduce harshness.

Nathan

[rudutch]

I put a 22w deluxe OT (from Triode Electronics) in my pro junior.
Louder, more bass, and a sonic improvement

[tedmich]

edcor sells three "trim levels" of OTs, for PP they have:
XPP series: 70 to 18K Hz.
CXPP series: 20 to 20K Hz.
GXPP series: 40 to 18K Hz.

I have been interested in conjunctive filtering since reading Eric Nyberg's stuff on his ax84 projects
EHN's AX84 Page