Need an output transformer recommendation for a 4x6L6 build.

[mhartman]

I currently am using a vintage Fender Twin OT, but it doesn't feel like it has a big enough bottom end for my tastes. My amp seems to lack the deep, lower frequency "thump" that I get with some other similar amps when I whack on an open E string. I'm pretty sure that it is the OT that is lacking down there.

Any recommendations for a bigger bottomed OT? What specs should I be looking for in an OT to achieve this goal?

[roberto]

Are you sure it's a problem of extreme low end? Usually what makes you feel more punch from an amp are low mids, so not OT extension on lowest notes.

[M Fowler]

Stiffen the power supply.

[mhartman]

Thanks guys. I'm not certain of the exact freq range, but OT is that "feel it in your chest" range. The amp that I was comparing mine to sounded similar throughout except for that "deep" bass area. The same speaker cab felt much different. Maybe the OT is a red herring, I'll look to the low miss and power supply a bit.

When you say stiffen the power supply, where would you start? I've got a 7H choke, two 220ufs in series and then 22uf on each "node".

Thanks,
Mike

[talbany]

Mike
Are you sure the OT is not on the way out..I've heard some Twins that have some pretty serious punch ..Other ones you could try are the
Hammond 1650
Bassman 100 Mercury Mag or there High powered Tweed Twin replacement9this is a wonderful Xformer)
Mercury also makes a Twin FAT stack

You could also move to a 7581 power tube

Good Luck!!

Tony

[mhartman]

Mike
Are you sure the OT is not on the way out..I've heard some Twins that have some pretty serious punch ..Other ones you could try are the
Hammond 1650
Bassman 100 Mercury Mag or there High powered Tweed Twin replacement9this is a wonderful Xformer)
Mercury also makes a Twin FAT stack

You could also move to a 7581 power tube

Good Luck!!

Tony

Thanks for the recommendations Tony. The OT could be failing, I'm not sure because it sounds strong other than the deep bass freqs. I've got an old 8 ohm Showman OT and a PA135 OT that I may try subbing in.

[talbany]

Mike
Are you sure the OT is not on the way out..I've heard some Twins that have some pretty serious punch ..Other ones you could try are the
Hammond 1650
Bassman 100 Mercury Mag or there High powered Tweed Twin replacement9this is a wonderful Xformer)
Mercury also makes a Twin FAT stack

You could also move to a 7581 power tube

Good Luck!!

Tony

Thanks for the recommendations Tony. The OT could be failing, I'm not sure because it sounds strong other than the deep bass freqs. I've got an old 8 ohm Showman OT and a PA135 OT that I may try subbing in.

The Deep bass thing can be an illusive creature.. I've had several Silverface Twins in that have it in spades and yet I have built amps with much larger iron that don't do that deep bass thing quite like those Twins..So I think there is more to that than just the OPT..When I figure that out I'll let you know!!
Good luck tacking in that Showman!!

Tony

[mhartman]

I'll tack it in and report back. Should be interesting to hear the difference, if any. Thanks again.

[mhartman]

Well, I tacked in the Showman OT. It sounds fuller. Not a ton of difference, but nicer in the "hit you in the chest" frequencies. I don't think my Twin OT was bad because it sounded good and strong, just not down there. I'm wondering is the difference between 4 vs 8 ohms into an 8 ohm cab, 1.9k vs 2k primary, or even negative feedback going into 8 vs 4. Who knows, maybe one saw 1000 hours cranked and one saw 10? In any event, maybe I'll try the PA135 OT just for kicks as well.

Now I'm wondering if a big, new OT would make a difference. I guess building a couple amps vs 1000 keeps a guy wondering what makes that last 1%.

[talbany]

Like I said man it's a strange thing..IMO larger iron does make a difference but is no guarantee you will get that BIG fat blooming low end.. I don't think it lies behind the NFB curtain..It seems to me to be more in the tone caps (I find the Mallory 150's do it the best) as well as the larger plate 35w 6L6 types (although those twins had 6L's) like the 7581's or even KT88's.. I know the transformer has to produce those lower frequency's, but am not quite certain that that's where they are generated..Please let us know if you can figure this one out!!
BTW you should hear a deeper low end on the higher ohm tap.. This is because you are using more wire/windings in the OPT sec..But the difference is a bit subtle..IMO

Tony

[mhartman]

Well, I finally got a chance to sit down and play the amp tonight for a while. Wow, that Showman transformer sounds completely different in the low end. Now I'm getting what I was looking for. Tight, hit you in the chest low end. It is a mystery to me as to why it helped, but I'll take it. Only thing is that now the amp is feeling a little bit stiffer than I like -- maybe because I've tweaked it based on the old OT for the last 3 weeks. Well, back to tweaking I guess.

I'll let you know if I can figure out what made the difference in the low end. I might have to try some Mallory 150s as well and see where it takes it (I've also got some NTE mylar/poly film caps that I want to audition on it).

Thanks again for chiming in and offering ideas!