Ampeg B25

[TylerDurdenPSSC]

Found a couple of these low-watt beasts on eBay, and am considering the purchase since playing out isn't of the essence right now.

My only concern is impedence.

The auction says you should run a 16Ohm cab with a dummy wire in the Ext. Speaker port (parallel to the cab) to achieve appropriate load.

True or false?

Couldn't you just run one 8Ohm cab and be okay?

[someparts]

To correctly access the 8 ohm tap you have to use the dummy plug. Could the transformers handle the mismatch for a while? Probably...this amp has bigger iron than a Marshall 100 watter, haha. There's no reason to do that though, the dummy plug is easy stuff.

The B-25B has some killer tone, but don't sell the power of this amp short...with an efficient 2x15 cab the B-25B hangs in most band situations. There are also a couple simple mods you can do to increase the useable power.

[TylerDurdenPSSC]

Assuming those mods include swapping "up" to the 6550 power pair? (I think I read of a few users doing this with their V4B's.)

I just love the vintage Ampeg tone to death! I made the mistake of parting with a V4B, and am attempting to correct that tonight soon. =P

I'd love to own one of each of Ampeg's tube amps. Just such a sucker for them!

[coreyfyfe]

Changing the power tubes won't increase your output, only change the tone and breakup characteristics. You'd have to change the transformer to get more output.

[TylerDurdenPSSC]

Ahhh... I see...

I still have much to learn.

=P

[brandau]

I ran mine into an 8 ohm cab for months with no problem... Eventually I had my tech make a simple mod to make it 8ohms.

Also, it's every bit as loud as my v4 b, and through my 215 ampeg cab it can keep up w any band Ive ever played with...

[TylerDurdenPSSC]

How do you compare the tone of the B25 when compared to the V4B? Am I correct in assuming very similar?

What does the mod involve going from 16Ohms to 8? Is it possible to go down to 4 Ohms?

[someparts]

Cap mod noted here:

Does the Ampeg B-25B ruin speakers?


Also you can change the rectifier to solid state to take a little of the tube sag out. I like mine with the tube though...with a pair of EVM 15Ls.

[someparts]

To go to 4 ohms would require a new transformer.

Channel 1 is more treble and can be used for guitar. Channel 2 is Fliptop Motown goodness. And the power tube grind is great also.

[TylerDurdenPSSC]

Lost the auction, dadgummit!

Bought an Ampeg hoody to tie me over instead. =P

Gonna get to reading on that mod.

Thanks for the info guys, I'd love to learn as much as possible about tube amplification, mods, repairs, etc... This stuff really interests me!