Replacement Output Transformer

[jzucker]

I just bought a bandmaster reverb/vibroclone (with 2x10). I plan to replace the output transformer with a bassman sized one since the bandmaster one is wimpy (to my tastes).

Just wondering about transformer recommendations. The best thing would be to get a real '60s bassman output transformer but short of that, it looks like Allen is now offering a bassman output transformer but it has 4 & 8 ohm taps and my experience is that you always want to use the highest tap to take advantage of the entire transformer secondary.

I've tried New Sensor's universal bassman output transformer and was not too impressed with it.

I know about MM. Are they the final word on this kind of thing or are their other options?

Jaz

Bah!!! You want beef? Drop a Twin OT in there and run that sucker at 8 ohms!!! Although the downside is I believe the choke will also need to be moved over a bit for all to fit nice and comfy.

Heard nothing but good things about the Allen amps so I'm guessing you can't really go wrong with the iron. Haven't used any of his OT's myself, couple of PT's and been quite impressed. Used a handful of MM Plexi OT's and really like them, 100 times better than stock iron but have no experience with thier Fender stuff.

bwilliamson
boxerboards.com

[jzucker]

Originally posted by BWilliamson
Bah!!! You want beef? Drop a Twin OT in there and run that sucker at 8 ohms!!! Although the downside is I believe the choke will also need to be moved over a bit for all to fit nice and comfy.

Heard nothing but good things about the Allen amps so I'm guessing you can't really go wrong with the iron. Haven't used any of his OT's myself, couple of PT's and been quite impressed. Used a handful of MM Plexi OT's and really like them, 100 times better than stock iron but have no experience with thier Fender stuff.
bwilliamson
boxerboards.com

If the Power Tranny was able to handle the extra load, I'd probably get a MM Plexi OT and put EL34 tubes in there but I'm not sure a BF Bandmaster PT could handle the extra heater current required.

How much of a real difference does it make to run a multi-tap OT on the lower tap? That's the only downside to Allen's 50 Watt OT as far as I can tell. I'm going to typically run it at the 4 ohm tap so I won't be using all the secondary windings...According to Gerald Weber, this makes a huge diff but I'm not prepared to believe everything he says!

How much of a real difference does it make to run a multi-tap OT on the lower tap? That's the only downside to Allen's 50 Watt OT as far as I can tell. I'm going to typically run it at the 4 ohm tap so I won't be using all the secondary windings...According to Gerald Weber, this makes a huge diff but I'm not prepared to believe everything he says!

Honestly I don't have the money/time to invest in a bunch of the same speakers to do that type of imperical testing. I just go with what I got and tweak the circuit it till I like it or scrap it working with what I got. As the choices really aren't that plentiful it seems to be about the only way to go.

They were talking on Ampage awhile back about this and I didn't read too closely but once of the techs I respected was saying that modern transformers can take into accoun and somewhat negate that.

got to run, try and finish my thought later

[jzucker]

Originally posted by BWilliamson
Honestly I don't have the money/time to invest in a bunch of the same speakers to do that type of imperical testing. I just go with what I got and tweak the circuit it till I like it or scrap it working with what I got. As the choices really aren't that plentiful it seems to be about the only way to go.

That makes sense. If I knew of an exact BF Bassman repro transformer, that might be the way to go. Either that or buy a busted up BF Bassman head and steal the OT...

[JamesPeters]

If you want a really good Fender replacement tranny, Heyboer is up to the task.

You can pick one from Mojotone.com instead of calling Heyboer--I'm pretty sure Heyboer makes all their Fender replacement trannies (you can ask them if you want). For a one-off it's better to go to Mojotone, probably.

I wouldn't go with a plexi OT in that amp personally. I'd just get a good Fender type tranny. If you're trying to make a plexi, then use a plexi tranny.

anyway, back from dinner with a little time.

Don't think you could go wrong with either the MM or Allen OT. Might have to tweak either way to get the response you want from the amplifier but in the end probably worth it.

As for running EL34's, I've done it in a Bassman and I'm not sure if they speced a different PT for the Bassman and Bandmaster. Not sure why they would but that goes without saying. Heard some say they've run 34's in Bassman's for years and blown others. Who know who did what?

Since your modding it anyway I'd go ahead and use the 34's and the OT of your choice. Believe I read this is a Bandmaster Reverb with a tube rectifier. Use a copper cap instead of the tube and the 5A winding won't be sucking anything and might help out the load with the 6.3V. If it blows replace it, I can recommend the Allen PT as I'm running a Bassman head with 4 12AX7 and a pair of 6550's in it and it barely gets warm after an hour. T.Weber suppose to be having some PT made for him, B+ is mulitapped at something like 320 and 360 which would be nice for a variety of voltages. And his specs were way big enough for 34's plus all the 12ax7's you have.

In the long run replacing both trannies is cheaper than buying a Bassman to scavenge a OT. .....but then again you have another modding platform. I love Bassman's, that one with the 6550's is a Bogner XTC dirty channel into a Marshall rear-end and sounds pretty decent in a stealth package.

amp PORN: http://bwilliamson.home.mchsi.com/bassexp.htm

[jzucker]

Originally posted by JamesPeters
If you want a really good Fender replacement tranny, Heyboer is up to the task.

You can pick one from Mojotone.com instead of calling Heyboer--I'm pretty sure Heyboer makes all their Fender replacement trannies (you can ask them if you want). For a one-off it's better to go to Mojotone, probably.

I wouldn't go with a plexi OT in that amp personally. I'd just get a good Fender type tranny. If you're trying to make a plexi, then use a plexi tranny.

Thanks James...I'd feel better if I could see a picture of them on their site. I was disappointed in the quality of the transformers that New Sensor was selling. Their universal bassman output transformer in particular...

[jzucker]

Actually, Mojo doesn't have a 4 ohm Bassman OT on their site. They have a universal 2,4,8 and a tweed bassman OT...

[jzucker]

Originally posted by BWilliamson
anyway, back from dinner with a little time.

Don't think you could go wrong with either the MM or Allen OT. Might have to tweak either way to get the response you want from the amplifier but in the end probably worth it.

Thanks Brent. One more question...Have you tried the new sensor bassman OT? It's less than $50 and is 4 ohm like I'm looking for...As I said, I was disappointed in the multi-tap version of their bassman OT . Not sure if this is the same tranny without the other two taps or not...Someone told me the new sensor trannies are made offshore now though their site says U.S.

Regarding the bandmaster PT, it's HUGE. I don't know why they thought they needed something so big, particularly since they dropped the voltages down with a 5U4 rectifier. I'm guessing that it'll work fine with EL34s, particularly if I use a copper cap rectifier as you mention. Since I don't use both channels, I could pull the normal channel preamp tubes too...

Anyway, this is a much more fun way to approach an amp project than starting off fixing design issues. Thanks everyone for your help!

[jzucker]

P.S.

Brent - Your amp looks incredible You have clips online?

Not sure who this Bruce fella is, but I've never tried the OT you've mentioned.

Thanks about the amp, quite proud of that one as it pretty much is the pinnacle of my building and all my amp layouts are pretty much looking the same no matter what cirucit that I chose. Honestly it was more a challenge to see how it worked and if it would work as I don't do many high gain circuits as they really don't appeal to me. Was quite the fun project that came together quite quickly.

As for clips, can barely play a note anymore. Just enough to fire them up and tweak a bit before I send them off with buddies of mine for the real abuse and feedback. Really just love the thrill of the chase these days. One day I'll find the Perfect Circuit!

brentwilliamson
boxerboards.com

[jzucker]

Originally posted by BWilliamson
Not sure who this Bruce fella is, but I've never tried the OT you've mentioned.

Bruce?!?

http://www.amazon.com/exec/obidos/tg...glance&s=music

You mean, that's not you!?!

Thanks about the amp, quite proud of that one as it pretty much is the pinnacle of my building and all my amp layouts are pretty much looking the same no matter what cirucit that I chose. Honestly it was more a challenge to see how it worked and if it would work as I don't do many high gain circuits as they really don't appeal to me. Was quite the fun project that came together quite quickly.

As for clips, can barely play a note anymore. Just enough to fire them up and tweak a bit before I send them off with buddies of mine for the real abuse and feedback. Really just love the thrill of the chase these days. One day I'll find the Perfect Circuit!

brentwilliamson
boxerboards.com

Well, I'd love to hear your amps. They look wonderful. Thanks for the inspiration. Sorry about screwing up your name.

- Zack oops, i mean Jack...

[JamesPeters]

Jack, if those Mojotones are made by Heyboer, I'd say their quality shouldn't be a concern. Their stuff is made very well. I deal with them directly because I have my trannies custom made by them, but even their "stock" offerings that I've seen are really well-built.

[jzucker]

Originally posted by JamesPeters
Jack, if those Mojotones are made by Heyboer, I'd say their quality shouldn't be a concern. Their stuff is made very well. I deal with them directly because I have my trannies custom made by them, but even their "stock" offerings that I've seen are really well-built.

I'll email them and ask them if Heyboer makes them.