Bassman transformer for Bandmaster - which is better?

[Chevy]

Hi Guys,
I fairly recently replaced my Bandmaster Reverb amp's output transformer with a Hammond Bassman OT. Wow - what a difference! The amp used to start to compress at about 4 on the dial, and there was no real headroom beyond that. Now with the new bassman OT, I can run at about 7 on the dial, and there is still some headroom left, and the bottom is so much tighter and present, it's great. Sounds better overall... haven't A/B'd them side by side, but seems there is an overall tonal improvement, besides the headroom issue. I can't believe it took me all these years to wake up to this part of the picture... sheesh.
Anyways, I don't have any experience with Mercury Magnetics, but am wondering if there is a worthwhile improvement yet to go with a step up to a MM Bassman OT? There is probably some room for fidelity improvement in my current amp, in terms of clarity and perhaps sweetness/amount of top end... I don't think I'm hearing all that can be realized just yet...
The MM OT runs about $160-$195. or so... is it worth the extra amount? (lots of models to choose from) Don't know how the Hammond compares with the original Fender replacement OT, either.
There is also a Haebor unit from Allen amps as well, made for the Bandmaster/Vibrolux... anyone try that or an equivalent?
Any thoughts would be appreciated. Trying to get the best sound out of my amp...
Thanks much,

[JoeM]

Hammonds are excellent, IMO you'd just be throwing more money changing to a different brand. You've already upgraded, enjoy the sound improvement.

[Tom Phillips]

Hammonds are excellent, IMO you'd just be throwing more money changing to a different brand. You've already upgraded, enjoy the sound improvement.

+1 No more to say.

[olddawg]

Yeah....I wonder about the oversized OT thing. My go to club amp is a 18 watt Marshall variant. It has a standard Heyboer PT, but the OT is this giant monstrosity that says Zenith on it. Everyone tells me that they have never heard an 18 watt amp so loud. I have sound men griping all of the time. I love the articulation and sensitivity. With an OD and an old Rat it screams and cleans up.

[Chuck H]

I build with the 16xx series "off the shelf" Hammonds whenever the numbers line up with what I'm doing. I usually de-rate by 50% (as instructed by a tech at hammond that builds his own guitar amps, before Hammond had their guitar amp line). I'm never dissapointed. One amp I make is a 2XEL84 thing that puts out about 15W clean. The prototype uses a Hammond 1608. The sale model uses a proprietary Heyboer. The Hammond "off the shelf and half rated" OT is a little larger and sounds better.

I do think the guitar amp line is made as close to stock specs as possible and uses modern materials. The shelf models are carefully interleaved and high pot tested and selected with a 50% de-rate seem to saturate just a tad on the top end but keep a big bottom. Just as ideal as I can imagine. I would NEVER spend more on MM iron. In fact, there was an individual here who was on a tone quest with his plexi clone. He tried a few different OT's. MM was one of the contenders but the builder/owner picked the Hammond guitar amp replacement OT for that amp above all others for tone. Nuff said. My only gripe with Hammond is that they don't play ball on a price break for amp builders. Only transformer distributors get a price break.

[Chevy]

OK guys, seems the concensus is pretty clear... I'll just stay with the Hammond. Saves me a bag of $ and a fair bit of work, so thanks much for your ears of experience !
Chevy.

[pdf64]

Which model of Bandmaster Reverb? If you haven't already done it, on the older versions, the reservoir cap values can be increased (from 2 x 70uF in series to 2 x 100uF). You may find that helps with the bottom end.
Pete.

[Chevy]

It's a TFL 5005D. And yep, I've already put in 220uF x 2 caps in there... that's probably why, with the new Hammond OT, that it doesn't compress much now. But that's what I was after... I like the dynamics, and being able to dig in sometimes in the bass freqs without mushing out.

[Jag]

Yeah, I was going to suggest upping them to 220uf x 2. I have done that on a couple of my Bassman amps and it made a huge difference on how tight the bottom end is.

[mort]

Forgive me if I'm incorrect as I'm just now learning a little about reservoir caps, but wouldn't such a high value put a big strain on the PT?

[soundmasterg]

Forgive me if I'm incorrect as I'm just now learning a little about reservoir caps, but wouldn't such a high value put a big strain on the PT?

The vintage Fender amps always had a power transformer that was pretty robust. You don't see them blowing out often. Going from 70uf to 220uf isn't all that big of a jump, and in the Fender they are connected in series, so it is really like going from a single 35uf cap to a single 110uf cap.....not that big of a jump. If you went to a 10000uf cap, then that would be a big jump and you may want to do some checking to see if the power transformer could supply that much current that quickly. Merlin's power supply book likely has some info in it relating to this...

Greg

[mort]

The vintage Fender amps always had a power transformer that was pretty robust. You don't see them blowing out often. Going from 70uf to 220uf isn't all that big of a jump, and in the Fender they are connected in series, so it is really like going from a single 35uf cap to a single 110uf cap.....not that big of a jump. If you went to a 10000uf cap, then that would be a big jump and you may want to do some checking to see if the power transformer could supply that much current that quickly. Merlin's power supply book likely has some info in it relating to this...

Greg

I read some of Merlin's webpage earlier today concerning smoothing and the res cap. It noted that a tube recto could stand less "uppage" on the uF value than SS rectos, but I didn't realize that they could go that much higher. Cool. Gives me something to experiment with later on down the road with my own project.

[Chuck H]

There's another way to increase filtering with a tube rectifier. A simple pi filter. You can have a lower uf cap right off the rectifier follower by a resistor that only has to be significant to the rectifiers resistance. Since a pi filter doesn't cause much sag due to resistance, a tube rectifier followed by a 20uf cap, then , say, 68R to 100R resistor and then an 80uf cap can give you plenty of filtering, no apreciable stress on the tube rectifier and very little additional sag. I can't site a bunch of principals about this, but I know it works.

[EFK]

Absolutely, what Chuck said (right above). I use a 5V4 very frequently for a 50s type of amp I make that uses 6L6 tubes. A 5V4 is only rated for around 10 uf right off the rectifier but obviously 2 X 6L6 need quite a bit more than that. Pi filter to the rescue! And, you can easily fine-tune the sag and compression depending upon the resistance value and the cap value.

[soundmasterg]

I read some of Merlin's webpage earlier today concerning smoothing and the res cap. It noted that a tube recto could stand less "uppage" on the uF value than SS rectos, but I didn't realize that they could go that much higher. Cool. Gives me something to experiment with later on down the road with my own project.

Don't take what I said to mean that you can exceed the ratings for tube rectifiers and their max cap value after them. Using the approach than Chuck H and EFK meantioned works great, but aside from that, you wouldn't want to exceed the max cap specs right off a rectifier tube. This thread was about Bassman transformers vs Bandmaster transformers, and in both of those amps, a SS rectifier is used, so all of my large cap recommendations above were based on the fact that there would be a solid state rectifier in use.

If you go to an extreme and use say a 10000uf cap after the diode rectifiers, then you ruin all the touch response of the amp, nevermind any other potential issues. Part of the charm of the guitar amps we know and love is that they use unregulated power supplies with small filtering. Go too big and even if the power transformer can supply the current to charge the cap quickly enough without overheating, having such a large cap there doesn't allow the amp to sag at all, and the nice "feel" goes away. Remember....everything in moderation!

Greg

Greg