PRS MT15 O/T upgrade

[wildboy280]

Hi everyone,
I own a PRS MT15 amp and I'd like to upgrade the the output transformer to achieve more headroom.

Transformers I'm considering are all Hammond:
1760J (40W, 4k)
1750N (50W, 3.2k)
1750Q (50W, 7.3k)

Original o/t is 3.6k, unknown power (somewhere around 25W?).

Ideally the 1760J would be the first choice because it seems a direct fit, having only two mounting holes.

Which one would be better?

[pdf64]

Hi everyone,
I own a PRS MT15 amp and I'd like to upgrade the the output transformer to achieve more headroom.
…

What exactly do you mean by ‘more headroom’?
Guitarist’s use to to mean ‘lower gain’ eg I swapped V1 from 12AX7 to 12AY7 to get more headroom.
But also higher power output, eg my 100W full stack has more headroom than my 50W half stack.

Are you expecting any change to result in a measurable difference?

[sluckey]

The 1760J sounds very nice in my Phoenix PP 6L6 amp.

[wildboy280]

There are several videos and threads of people who replaced the o/t in this amp and they all noticed more clarity and more balanced low end in the lead channel. Also more room for the clean channel before break up. All those people used a 50W O/t.

I was thinking about the 1760J because I won't need to drill the chassis, which is a plus. Also, all those models are locally available. My question is whether a 40W o/t would be a noticeable improvement from the stock one with 5881 tubes.

Amp sounds great in stock condition, but if it can sound even better in a band/gig environment, why not?

[sluckey]

I doubt anyone reading this has put a 1760J in that particular amp, so you're kinda on your own. Just do it and let us know what you think.

[shooter]

fwiw, I like large OT's compared to measured watts, I also like SE amps and that method of oversizing the OT comes with many $$'s and lots of lbs.
most 10-12w PP amps i've built, i used 25W iron, the last 4 SE 16W amps had 25W iron.
believe you get a broader range of frequencies through, giving you a "fuller" sound, gain doesn't really change

[pdf64]

There are several videos and threads of people who replaced the o/t in this amp and they all noticed more clarity and more balanced low end in the lead channel. Also more room for the clean channel before break up. …

Has anyone reported solid data, eg a change that has been measured?
Consider the possibility that people may be tricking themselves, hearing something they want to hear. As by that point, having bought and fitted a big heavy lump of OT, they’re rather invested in the change being beneficial.
Hence double blind comparison testing being a thing.

[PRR]

> Has anyone reported solid data, eg a change that has been measured?

    

> people may be tricking themselves

 

> Hence double blind comparison testing being a thing.

 
Subjectivism is the one true religion.

[pdf64]

To be fair, different OTs of the same primary impedance can sound a bit different.
Maybe with high end lab grade test gear, those differences could be displayed, analysed, and attributed to particular materials / construction technique. But I’m not aware of anyone doing that yet.
Rather the market leader upgrade transformer manufacturer relies on BS snake oil marketing.

Given either commonly used metric related to ‘headroom’ I gave earlier, changing the OT for one of the same impedance is really unlikely to result in the amp’s headroom being affected. The stock OT would need to be absolute junk.

So if your ‘headroom’ correlates with gain or power output, I suggest that you’d be better off saving your time and money. If you want to sound better, use that time to work on guitar playing technique.

If you meant something different with your use of ‘headroom’, it would be helpful to explain it, or provide a definition.