transformer recommendations for deluxe reverb/18 watt TMB

[steve-o]

Hey all, up front, I must confess I'm building my first amp (with help from a more-experienced friend). I bought a blues jr, (and since S2 is no longer selling kits for them) am putting in my own circuit. The preamp section is very fender-ish. The power amp section is very marshall 18 watt TMB-ish. My question is, I'm stumped when it comes to trannys. Should I be using a heyboer for the output and a fender-type tranny for the power transformer? A little deeper question: what makes a given transformer good for a particular circuit? How much difference does it make? I've been told that almost any transformer I get will be better than what was in my stock blues jr. Thanks for your help, and feel free to link me to previous posts it that would be more helpful.
Thanks again!
steve

[Allynmey]

The trannys are based on the power requirements and impedance requirements of the power tubes. Are you using (2) el-84's in the power section? Then get something that will handle 8K Primaries and 4/8/16 secondaries. Just about any of the common 18 watt trannys will do. You could also use any 18 watt power tranny too. 275-0-275 secondaries and 150mA should work.

Allyn

[Bob-I]

steve-o, welcome to your new addiction, amp building. I'm a big fan of donor amps like this. I built an Hi-Octane in a Peavey SS amp, modded a Peavey hybrid, SS preamp tube power amp, into a Dumble (Peav-umble?), put a Dumble amp into a Crate SS amp (Crumble?) so enjoy. It's a ton of fun and you should get a great amp out of it.

So like Allyn said, it depends on what you're planning to do. If you want to keep the same tubes and sockets go with a pair of Marshall style xformers. If you want to go more Fender-y and change to octal sockets and 6V6's get a Fender Deluxe style xformer pair.

In either case I like the xformers from mojotone.com and tubesandmore.com . I've had great success with both. If you're budget minded tedweber.com Weber, has some nice budget xformers that sound damn good for the price. I have 2 amps with Weber xformers in them and as much as I hate Ted and TA I just can't pass up their prices.

Good luck, make sure you draw up an accurate layout and post it here for review. Lots of good minds hang out here.

[rfgordon]

Output transformers can be a vexing at first, so your not alone in trying to figure out what works with what.

Here's a chart to help that along:

2 EL84s (or 2 6V6s) need to see 8K primary
4 EL84s (or 4 6V6s or 2 6L6s) need to see a 4K primary

A tranny that's 4k pri with 4/8 ohm taps becomes an 8K pri if you double the impedance of the speaker thats connected. You can always go with up in wattage rating safely, and sometimes that can yield pleasing results, like increased headroom when cranked. On the other hand, a properly rated OT can add to the vibe if it saturates nicely when the amp is really pushed. It ends up being a matter of taste. Even the primary impedance numbers are not necessarily set in stone. If it sounds good and doesn't explode, go for it.

[steve-o]

Hey guys, thanks so much for the help! I honestly didn't expect anybody to post on this so fast. This forum is great! Anyway, I guess I'll go shopping for trannies now. I'm going to go to the sites you mentioned above and see what I can find. Any other recommendations for where to get a good deal on trannies? I think I'm going to go with OT and PT for an 18 watt marshall to keep the EL-84 circuit. Now, what recto should I be running with those? EZ81? GZ34? Thanks again, all,
steve
p.s. I'll remember to get some pics and/or schematics up when I'm done.

[rfgordon]

As for sources for transformers, you lave lots of options.
If you wanna blow a whole month's lunch money all at once, there's Mercury Magnetics. Very fine iron, but MUCHO dinero!

Heyboer transformers are nice, excellent for the price, and are available at several places, including AllenAmps.com and Turretboards.com (you have to email Ken Watts at Turretboards to get price and models).

Webervst.com has lots of transformers.

http://westlabs.com/Frames.HTML Westlabs has what he says are PT/choke/OT sets in 15 watts and 30 watts ratings that were made for the original Matchless folks. Can't really vouch for that, but, if true, are very nice values. I suspect they are overbuilt and the stated ratings are conservative.

I have built amps with Heyboer iron and some with iron out of vintage amps like Newcomb and Harmon Kardon. If you like to experiment, sometimes the vintage units yield good results, but I wouldn't sell an amp like that, unless it had a really great, unique voice. But sometimes you can score an old office mono PA for a few bucks and learn a lot from building that way.

Remember that the OT can have a dramatic impact on the feel and personality of the amp. You may find that trying a few different ones leads you to the tone and feel you are looking for.