NAD - Ampeg B25B

banikek · #1 11-16-2010, 09:58 PM

Many years ago I picked up an old, beat up Ampeg B-18 speaker cabinet. Almost all the tolex was gone and no amp was included. Since then it has gone thru a few incarnations and currently is loaded with a nice JBL 18. Today I picked up an Ampeg B25B head. Very clean. Paired up nicely with the old (now new) B-18 cab.

Did the plug trick on the back to fool it into 8 ohm mode. Also played around with crossing the channels etc. Sounded best with my old P bass with flats and also with an old Mosrite bass I have. Please let me know if anyone out there has some tricks or tips for me in regards to this amp. Should be fun!

Also, anyone ever use a B-18 with an upright bass? If so do you mic it or use a pickup?

thanks,
chris

JimmyM · #2 11-16-2010, 10:00 PM

nice rig! crazy retolex job on that b-18 cab! never ran upright with a b-18 but i do it all the time with my b-15. i use a pickup...the clef revolution solo 2. fantastic pickup! i see no reason upright wouldn't kill with that rig.

banikek · #3 11-16-2010, 10:12 PM

The tolex was done buy a guy here in Minneapolis who does work for Savage. I was gonna do the whole blue diamond thing but when he matched up some Fender tan tolex, Marshall grill cloth, and piping, he caught me at a weak moment. Plus at the time it was super hard to find the blue diamond stuff.

chris

vistacruiser · #4 11-17-2010, 12:29 AM

Congrats on picking up really cool amp, looks great! Is that an 8 ohm speaker? If so just use the ext. spkr. jack and you'll be fine, (I've driven 4 ohm cabs on occasion and no issues yet). You asked for tips? here's a couple.... Channel 2 has a deeper bass tone, so I plug in to "2 normal" and run my short loop cord from "2 bright" over to "1 normal". Another idea, if you have an A-B-Y box, is to run a clean signal to ch2 and an effects signal to ch1.
A very simple mod you can do is to pull the rectifier tube (5AR4), and replace it with a solid state unit. There is quite a difference, the tube slows the attack and the ss increases attack, gives the amp more punch. Some will prefer the tube, I like the ss. You can find solid state rectifiers at many tube supplies for about $10.

Here's how I do the "loop"

stiles72 · #5 11-17-2010, 12:39 AM

I've been playing a Baby Bass through my B15. I run the stock diaphram pickup into channel two and run a Schaller magnetic pickup into Channel 1. Your B25 head with the B18 cab should make for a great pairing - have fun with it!

coreyfyfe · #6 11-17-2010, 06:09 AM

I have nothing to add except that that is a schweet lookin' set up. Congrats on the new amp.

banikek · #7 11-17-2010, 11:53 AM

Vistacruiser - great minds think alike! My playing around last night landed me plugging into Normal 2 for the best tone.

Another question - when you plug an 8 ohm speaker into the "Ext. Speaker" output, are you also putting a "dummy" jack into the "Speaker"? That is what I was doing.

I will check out the ss rectifier. I also tried the VT Bass pedal with it and that sounded damn good too. Not sure if that was sacrilege tho!!

thanks again,
chris

JimmyM · #8 11-17-2010, 12:26 PM

not sacrilege at all. i always use a vt deluxe with my tube ampegs. for one thing, doubling on upright requires a 2-channel device with an eq for at least one channel. for another, i've become an electric bass distortion nut and i always like at least a little on it at all times now. but i can't even turn up a b-15 loud enough with my bands to get distortion so the vt is how i get it.

vistacruiser · #9 11-17-2010, 06:45 PM

Quote:

Originally Posted by banikek

Another question - when you plug an 8 ohm speaker into the "Ext. Speaker" output, are you also putting a "dummy" jack into the "Speaker"? That is what I was doing.

Chris, short answer, no.

When I use an 8 ohm cab I use the ext. speaker jack as if it were the main speaker out, same as I would any other amp. As I read the schematic, (1968 model B25b by Joe Piazza) when the ext spkr jack (it's a switching jack) is used, it cuts off the 16 ohm main output, and switches to an 8 ohm tap off the output transformer. Also, my '69 model has an attached main output speaker cable with a 4 prong plug that only fits the orig 16 ohm cab. Yours is newer, may be '72 to '75? and I'm not sure if you have that set up or if it was modified.

BTW- I think that B-18 cab looks pretty neat, I often plug into an SWR single 15", no vintage vibe thing there.