I never had that one, but I did work with a band that had the PA version - two 15's, and a round horn at the top. Same PITA to haul around, I betcha.How about the Kustom with 3 15" speakers? That was a real killer.
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Double Bass Ampeg B15
- Thread starter Dave Martin
- Start date
- May 6, 2003
- 5,272
- 160
- 64
- Disclosures
- Proprietor Fifth Avenue Fret Shop. Technical Editor Bass Gear Magazine
I swear part of my back problems began years ago when we would ride around in the back of a van trying to sleep on top of those Damn Roll and Pleat Kustom speakers and amps we all played through.
They seem comfortable until you hit a pothole.
They seem comfortable until you hit a pothole.
I recently purchased a B15N (head only) from a dealer in the USA via e-bay.
The amp arrived and I was elated. Its better than I imagined.
The tubes look to be original. In fact the 6SL7s say Ampeg on the plastic base.
The amp has a "anti hum" adjustment on the rear. I assume this is a bias adjustment.
I am curious to know, should I decide to, which tubes should I replace the originals with and do I need to adjust the bias on the amp once I do swap the tubes.
Any input or advice would be appreciated.
The amp arrived and I was elated. Its better than I imagined.
The tubes look to be original. In fact the 6SL7s say Ampeg on the plastic base.
The amp has a "anti hum" adjustment on the rear. I assume this is a bias adjustment.
I am curious to know, should I decide to, which tubes should I replace the originals with and do I need to adjust the bias on the amp once I do swap the tubes.
Any input or advice would be appreciated.
Far as I know, there is no bias adjustment; the "hum balance" is just that. Turn the amp up all the way and turn the pot til the hum is least audible. If the tubes aren't microphonic, leave'em alone. 6SL7s are still around, as are 7027As and 5AR4s. NOS 7199s are getting pricey, though. Just Google "vacuum tubes" and you'll find lots of dealers.
I have a local tube dealer that I bought some Winged C's from for my Traynor YBA 200.
The B15 says use 6L6 power and 6SL7 pre. I have heard that people have used different tubes to achieve more Db's or other changes.
Personally I like fat round and smooth sound and not at all worried about volume as I use this amp in my jam/recording studio and I can easily keep up with my band mates in the Db dept.
I am most inclined to use the same tubes, but I have heard that the older amps are not self biasing and might need to have that adjustment made by a Technician at the time of the tube swap as some even matched tubes will behave slightly differently than the ones which are being swapped out, or for that matter the original tubes.
Well, I think at the time the cab design was innovative enough to be part of the total package. But nowadays cabs have come so far in every sense--quality, voicing, power-to-weight ratio--I'm sure some of the newer available options are at least as good.
Mine's a 1961(!)--it's so early it's pre-diamond check. It sports the previous tolex style: navy random flair. 6L6s in the power stage, the 5AR4 rectifier, and yes, some of my preamp tubes are still Ampeg originals.
Another poster mentioned that 7027A tubes are readily available. I seem to remember them being scarce, but things may have changed since I read that.
Best bass amp ever, if you ask me. Certainly the blueprint of bass amplification, at the very least.
JAM
I use my early 70's B-15 for just about all my gigs. It is a little heavy but I think it's well worth it for the tone and the vibe. I figure if this amp won't cover the gig, then we're trying to play too loud!!
I've seen a couple of the reissues on e-bay, but they always go out of my bidding range.
I've seen a couple of the reissues on e-bay, but they always go out of my bidding range.
Jeff,
I couldn't agree more. The B-15 was a inspirational design, based on cutting edge technology for that time. The reflex baffle design of that cabinet was a very intelligent way to make use of an amplifier that only produced @35 watts. It's a very musical sounding amplifier as long as you don't push it. They were also built to last. That's why there are so many of them still around. In some ways, tube amps are easier to repair, you can just replace the rectifier, power, and preamp sections by changing out the tubes, no soldering required. Problem is if they blow a transformer it's now a expensive proposition. It was designed in a time where things were built to last.
Ric
Regarding the tube complement, I was going from what my B18 has; some iterations of these amps used different tubes. Use only what the tube chart in your amp calls for.
Scott is correct they are different. You should have all tube #'s on the back side of the head painted in white, on the chrome chassis, directly
below the corresponding tube.
The B-18 had a 50 watt head so the tubes are different to achieve that
power rating. It also had a "solid state rectifier" in in the early models.
Later they reverted back to a 5AR4 for the rectifier tube. The B-18 had 7027 A power tubes and a 7199 phase inverter. Both amps used 6L7's in the pre amp. B-15 used a 6L6 for power tubes. There were corresponding military tubes that could be used instead.
Here are links to the schematics
[Invalid or Expired Link Removed] just click on the Schematic's Link
I love my b-15s, but have never been able to get the sound I want for upright out of them, I recentley picked up the 91st one made for $100 because the store selling it didn't know there was a head in the beat up cabinet. great amps though
If it hasn't already been mentioned, good alternatives to rectifier tubes are the Weber Copper Cap solid state rectifier replacement devices: [Invalid or Expired Link Removed]
As I recall, the 7027A has a slightly different pinout than the 6L6 family. Make sure your amp is compatible before interchanging these tubes.
As I recall, the 7027A has a slightly different pinout than the 6L6 family. Make sure your amp is compatible before interchanging these tubes.
Greg Clinkingbeard
Commercial User
These can slam the tubes hard at startup. I'd just prefer a good rectifier tube. A tube is easier on the amp.
The Weber Copper Caps are designed to have a soft start, much like a vacuum tube rectifier. Also the Copper Caps do not have a filament like a vacuum tube rectifier does, so less current is drawn from the power transformer, which really is much easier on the amp (less current = less heat). Finally tube rectifiers are far from perfect. They can and do short out without warning. This is very hard on the amp to say the least. The Weber Copper Caps are far more reliable than vacuum tube rectifiers, which is the primary reason to use them.
A whole lot of B-15's are collecting dust somewhere or have gone to the bone yard because the power transformer failed, usually due to the rectifier tube shorting out.
BTW on older tube amps, filter capacitors are also prone to failing, often with disastrous results. These capacitors really should be replaced.
Greg Clinkingbeard
Commercial User
I'm not familiar with this particular thing; just with other solid state plug in rectifiers some would use in old Hi Fi gear. If these Weber things are indeed soft start, they may be the ticket.
I know what you're talking about, and you're right they're not so great. The Weber Copper Caps are much more sophisticated. They have effectively the same characteristics as a tube rectifier, without the tube's drawbacks.
BTW I have no connection with Weber Copper Caps. It's just a good product.
Rob,
If I have my information when Ampeg revised the B-15N(B) in 1962 they replaced the 5U4 rectifier tube with a "Solid State' Rectifier, but they went back to a different tube 5AR4 in 1967. I wonder why they took this step backward. I have a Webber Copper Cap in my newly reconditioned B-15 it sounds great.
Ric
I haven't seen a B-15N with a solid state rectifier from the factory, but I suppose it's possible. If Ampeg did go back to using a tube rectifier later, keep in mind that in the 1960's solid state devices (transistors, diodes) were nowhere near as reliable or well understood as they are today. Those of us old enough may remember some of the early transistor amps. There aren't many that are still around (unlike the old tube amps), and there aren't many that anyone would want now either. The transistor-equipped BT-15 in particular was a disaster for Ampeg with a very high failure rate, and many field technicians weren't used to working with solid state devices. The BT-12 was in production for a relatively short time, while tube amp production continued on.
edit: I just found a schematic for a B-15NB, and it did indeed use a solid state rectifier bridge.
I have a early 70s b15,it sounds fine with a electric bass,, but when I put the upright through it it makes a pop with the note ,,you would think the speaker is busted, but I have tried another speaker, and another cabnit just to be sure thats not it,I had new tubes put in 5 yrs or so ago,, and still have the pop,,I was told it might need caps??? anyone ever heard of this problem?? I'd love to get it back 100%, and use it.
