AMPEG B-25B Help

[TRichardsbass]

A B-25B head is available to me along with a 2X12 Bogan cab.

I'm not familiar with this Ampeg Tube head.

Need your help/input/comments asap!

tom

[Alex1984]

I tend to see it as a muscled up B15. Some people not as much power as the V4B and a bit anemic, others say it's the best tone they ever heard.

[coreyfyfe]

I think it was more similar in topology to the B-18 than the B15 though it used 12AX7s instead of 6SL7s. It had the same 7199 PI and 7027 power tubes and the schematics show pretty similar tone circuits and power amps.

[pgk]

absolutely incredible amp once it's freshened up with fresh power supply caps and so on. needs very efficient cabinets to sound it's best.

[Oren Hudson]

The search function is your friend.

[johnk_10]

IMO, the b25B's are great sounding amps, but they don't have nearly enough power for an amp that i could use on a gig.

[Colbymck]

I have a 1970 B25B. I believe it was modeled after the B18, which was modeled after the B15. (don't quote me on that). So it does sound more like a B15 than an SVT, but that being said, it's the best bass tone I've ever heard. (granted, I haven't played every amp in the world), but I still LOVE my rig.

I got mine with the matching 2x15 cab, and in my opinion, the cab is where the magic is. Orignal Altec 421A speakers. It is absolutely buttery. Always been enough volume for the venues I'm at. I bridge the two channels with a patch cable and then boost treble on the first channel and boost bass on the second. Sounds amazing.

[JimmyM]

It's a weird amp in that it's designed to operate with two 16 ohm cabs, but if you put in a dummy 1/4" plug into the first speaker out, you can run an 8 ohm cab safely in the second. Low power oddball vintage Ampeg tube amps are teh rox0rZ!

[vistacruiser]

I've had one for a long time and love it. 1969 Linden N.J. model. I got it with the matching 16 ohm, 2x15 cab that uses that 4 prong Mic plug looking connector thingy. I like it best with the orig. cab, (mine has the stamped basket, square magnet speakers, not Altec's) but it also has worked great with several 8 ohm cabs. I simply plug in with a cable from the EXT. SPEAKER jack, to the cab. Never given me any trouble.
If the Bogan is 8 ohm, it should be fine. One of the cabs I like is a MusicMan 4X12 sealed, I think it sounds great through 12's.

You'll notice channel 2 gives more deep bass response, so you can plug in to "2 normal", and run your jumper from 2 bright over to 1 normal, and mix your sound using both channels.

I replaced the rectifier tube (5AR4) in mine, with a solid state unit that just plugs in like any tube. It has less compression and more punch. I like it, some may prefer the tube recto sag, it's simple to change back.

I played around with different preamp tubes and found the Tung-sol 12ax7 to be my favorite current prod tube. The Phase Inverter (7199) did not like the Sovtek replacement tube, having a nasty hum, it required a NOS 7199.
The 7027a power tubes are Sylvanias that have been in there a long time and still doing fine. I have a new set of Sovteks on hand if the time comes.

I mostly use it for practice and recording, but just for grins I played a job with it a year ago at a smaller club, the amp shined!

[vistacruiser]

Colbymck'

Nice photo, that amp is in like new shape!

When I got mine in 1976, it was already beat up from the road.