When upgrading a Fender output Transformer?

[Slobrain]

Well here I go again, new thread.

JoeM suggested the replacement from Allen for my bandmaster reverb which seems like a really good OT. Beefy and a good drop in replacement.

New Sensor has the Fender Twin Reverb replacement OT that would really beef up my amp and the price is good.

After reading about vibroclones the twin OT looks good but not sure if it will fit on my BMR chassis.

Has anyone here tried the new Sensor Twin replacement OT's? any thoughts on the sound???

Thanks

Slo

[JoeM]

Are you looking for more clean headroom from the Bandmaster? I recommended the Allen since it's a direct drop in replacement, I had planned to use this in a build but used a Bandmaster OT (started out as a Weber kit). I've heard stock Bandmasters though with good speakers and still feel that it doesnt make sense to upgrade the OT if the speakers you're using could be improved.

[Slobrain]

Hey Joe,

Actually i'm using 2x12 cab loaded with celestion 70's. Great sounding cab. The stock OT is good. The amp starts to distort around 5 on the vol. I switched from a tube rectifier to a SS one, so that upped the voltage at around 475vdc from 440, rebiased the tubes and it did seem to get a bit louder and tighter after that change.

Im looking for a smoother low end. the amp does sound good stock. The output tubes are some old Sylvamia 6L6 STR super 6 usa made.

Clean the amp can nail Dick Dale to the old La bamba movie soundtrack. Using a Boss super overdrive can get the Lynyrd Skynyrd sound and more modern pedals sound good too. I just like having a very smooth bottom end. so thats why I wanted the beefy OT.

If I were to use a twin OT since I'm only running two power tubes it will be 8 ohm output, perfect for that 2x12 cab I'm using.

The Allen OT seems good, I emailed David Allen and he gave me a quote on shipping. I guess I'm trying to figure what the best bang for the buck would be.

Thanks

Slo

[JoeM]

I think the Twin OT is overkill for the 2 6L6 Bandmaster, (IMO). The Allen would give you more bottom end, but dont expect miracles. Plus the Allen wont require any chassis modification to fit. Increasing the filtering would help too. (Plates & Screens). Does the amp still have the original filter caps?

[Slobrain]

Hey Joe,

New Sprague Atom caps installed for filtering. I just replaced out a bunch of parts and replaced the 470 ohm with 1k 5-watt for the screens and replaced the 1.5k grids with flame proof.

I haven't changed any of the caps on the preamp tubes so they may be way over due since the amp is 43 yrs old.

Still some work to do but it still sounds good. maybe I will try the Allan OT so I won't have to modify.

Slo

[soundguruman]

Well here I go again, new thread.

JoeM suggested the replacement from Allen for my bandmaster reverb which seems like a really good OT. Beefy and a good drop in replacement.

New Sensor has the Fender Twin Reverb replacement OT that would really beef up my amp and the price is good.

After reading about vibroclones the twin OT looks good but not sure if it will fit on my BMR chassis.

Has anyone here tried the new Sensor Twin replacement OT's? any thoughts on the sound???

Thanks

Slo

I think you will spend a bunch of money on a transformer, and hardly notice any difference at all.
The transformers offered to "upgrade" amps are 90% hype and 10% emotion.
There is no magic transformation that is acquired, just because you change the transformer. Mostly imaginary, I would say.
Changing the circuit, and changing to a better speaker(s), better pickups, will make the most noticeable improvement. Tranny is the least noticeable.

[Smitty]

A Twin Reverb transformer will give you a dramatic increase in bass response. It will look for an 8 ohm load and run fine at 4 ohms.

The size of the core has a lot to do with the sound of the low end. Bigger core more low end. Smaller core more core saturation which is a little like compression.

I use the Classictone stuff and I thinks it's good.

[Iplayloud]

A resonance mod can work wonders for low end response, very popular with Marshalls. Like a Presence pot which is a higher frequency treble, a resonance pot is a lower bass boost. Increasing the filtering on the plates and screens definitely works too, you could swap the two series on the plates for 150 UF or even 220 and the screens from 20 to 33 or 50. More filtering means more bass but also a stiffer sound. Note that the Twin Reverb reissue has a pair of 220uf on the plates, which is not faithful to the AB763 circuit and gives the amp a big bass boost. You could also put a .01 cap across the 820 ohm feedback resistor, like the 135 watts Twin, it's alike a fix resonance boost.

[pdf64]

You could also put a .01 cap across the 820 ohm feedback resistor, like the 135 watts Twin, it's alike a fix resonance boost.

That cap is cutting super high frequencies and should have a minimal audible effect (all else being equal - it may be stopping oscillation or even inducing a resonant treble peak, depending on the idiosyncrasies of the build).
To get a 'resonance' type boost, a cap (~1 uF) would have to be fitted in series with the 820 ohm.
My experience of those small 125A6A 35 watt output transformers is that there's a noticeable benefit from replacing them with 'bassman' sized type, in terms of a bigger, smoother, more solid sound. More of a perception thing, not measureable with my basic test gear.