Bassman 10 -- Where's the Love?

[Richard]

How are the speakers in the Ten? I've plugged my bass into my SRRI and it sounds good but they don't do so well down low. I'm sure the open backed cabinet and the 5 string bass make it a little harder. 50 watts is on the low end of what a bass amp needs for me.

[Leo_Gnardo]

How are the speakers in the Ten? I've plugged my bass into my SRRI and it sounds good but they don't do so well down low. I'm sure the open backed cabinet and the 5 string bass make it a little harder. 50 watts is on the low end of what a bass amp needs for me.

Naturally you'll get a good deal less low bass out of your open-back Super Reverb. As I mentioned a couple of days ago, it helps to bolster a Bassman Ten's closed back cab to minimize rattling. And you can always swap in some upscale speakers for improved tone. On the cheap end, Jensen MOD 50's, which also make a good sub for SVT cabs. Feeling spendy? Score a quad of ToneTubby 10" bass speakers & enjoy a Cadillac ride. Well, as far as 50 watts will get you. Good enough for all but loud rock & heavy metal gigs. If you really want to feel the low B throb, better get you an 18".

[Justin Thomas]

Low B... phbhphphbhbhbt.

Zackly.

Justin

[Steve A.]

Looking at the schematic I seem to recall that the speakers are 32 ohms for an 8 ohm load on the OT...

Steve A.

P.S. The last time I checked GC was shipping used amps for around $32. It was a lot higher last year.

[Leo_Gnardo]

Looking at the schematic I seem to recall that the speakers are 32 ohms for an 8 ohm load on the OT.

FWIW Jensen MOD 50 are available in 32 ohm. Also - it would be a good upgrade for those who need a clear deep low frequency response to replace the Ten's walnut sized OT with a hefty Super Reverb/ Bassman unit, and some of these are available with multiple output taps 2, 4 & 8 ohms.

[Steve A.]

FWIW Jensen MOD 50 are available in 32 ohm. Also - it would be a good upgrade for those who need a clear deep low frequency response to replace the Ten's walnut sized OT with a hefty Super Reverb/ Bassman unit, and some of these are available with multiple output taps 2, 4 & 8 ohms.

I like the idea of replacing the OT. I usually buy speakers with the idea that I might move them around from one amp to another so they are usually 8 ohm (I'm a Fender guy.)

So what if four 8 ohm speakers were wired in series/parallel like a Marshall amp? How would the sound of that compare to four 32 ohm speakers wired in parallel assuming that the speakers were otherwise the same? I read here a long time ago that wiring two speakers in series changes the interaction between them compared to a parallel linkage...

Steve Ahola

[Leo_Gnardo]

How would the sound of that compare to four 32 ohm speakers wired in parallel assuming that the speakers were otherwise the same? I read here a long time ago that wiring two speakers in series changes the interaction between them compared to a parallel linkage...

That's another question that's been kicked around for decades. I had the opportunity to audition some Marshall cabs under careful conditions in 1986. They both had Celestion G12-80 speakers. One was wired series parallel 16 ohms, the other full parallel 4 ohms. Sounded near identical, driven by a 100W Marshall head. If anything the low bass was a little tighter in the parallel wired speaker. Tighter as in, the note stops when the string stops. Series-parallel seemed to have a little "overhang", just a dab of extra bass as if the cones kept moving a fraction of a second after the string was stopped. Not a heck of a lot of difference all in all, also not the kind of thing that would show up in a standard frequency response chart, it would have taken a "waterfall" chart to show the time-reactance difference between the cabs. If it wasn't just my imagination. So, wire your speakers in a way that's most convenient for you, or will allow an optimum impedance match or max power delivery between amp & cab. Don't worry much over parallel or series-parallel.

[Richard]

I usually play through an Ampeg with a 15".

[Richard]

I have a hypothesis that dissimilar speakers should be in parallel. I think as the impedance varies with frequency the power will flow to one speaker or the other (somewhat like a crossover on a much smaller scale) whereas if they are in series they should have the exact same signal.

[bob p]

You scored big time - I always like it when friends & customers & fellow MEFsters get a great deal. And you didn't have to pay shipping $$$$ (and get it bashed up that way) either. Good all around. You'll have to try that James stack channel for a while, see how you get along having a little Ampeg flavor built into the amp.

There's something to be said for having an Ampeg type preamp and a Fender type preamp in the same box.

I was actually returning a combo that had been destroyed by UPS when I found the B10 at my local GC store. I have not had good luck buying amps online. They always seem to get destroyed in shipping. But that's a subject for another thread...

[bob p]

FWIW Jensen MOD 50 are available in 32 ohm. Also - it would be a good upgrade for those who need a clear deep low frequency response to replace the Ten's walnut sized OT with a hefty Super Reverb/ Bassman unit, and some of these are available with multiple output taps 2, 4 & 8 ohms.

Yes, the B10 does have a much smaller OT than a 50W Bassman -- visually the difference is striking. But there's a reason for this -- the B10 is actually a 40W amp that shares it's supply iron with the other Fender 40W guitar amps, not with the 50W Bassmen. During sine wave stress testing I drove the PI really hard. I was able to make the amp deliver 20 volts RMS into a 10R resistive load. Doing the math, it's obvious that this is a 40W amp. Conventional wisdom says that all Bassmen are 50W minimum, but I don't think those specs apply to this model.

As far as using this amp as a 21st Century bass amp is concerned -- there's a lot working against it: low power, diminutive OT, low-powered Utah 10" speakers, cabinet with port diameters that are way too small to be effective... It's just not designed to be a high power gigging bass amp and using it to reproduce 30 Hz tones is just silly. Rather than fitting it with a bigger OT and real bass drivers in real bass cabs, I'd recommend rethinking the decision to use this as a modern bass amp. But for low-volume practice and recording work this amp has the tone in spades. There's lots of Motown and "cop show" mojo coming out of this amp. Realistically speaking that's all anyone should expect of it as a bass amp.

As a guitar amp there are only a few circuit tweaks required to put the electronics into Super territory. Depending on what you're looking for the small OT isn't all that bad. It depends on whether you want the smoothing effect of a smaller OT or the bigger sound of a huge OT with lots of bass response. I think that the OT is matched fairly well to the speakers/enclosure. By putting bigger iron into an amp like this I think that all you'll end up accomplishing is moving the weakest link in the chain to a different location. I'm not sure that the cab/speakers would sound better with bigger OT iron, it might stress them. If bigger sound is the goal with an OT upgrade then this amp would probably work best as a head conversion. Personally, for big sound I think it's easier to switch on my Twin Reverb.

[Tom Phillips]

...One of the odd things about the Fender assembly line is how they used creativity to assure that every unoccupied pin on a 6L6 socket got used for something. Fender always seems to have grid stoppers and plate resistors mounted across the tube sockets, but this amp takes the Fender weirdness one step farther -- those 0.002uF oscillation suppressors are mounted on the socket, with one lead going from the proximal side of the grid stopper and the other to the cathode pin then passing through the cathode pin to the chassis. What is really odd about this setup is that the capacitor lead that goes through the cathode pin ends up being soldered to the chassis to form the tube's chassis ground! I wish I had taken a photo to document this weirdness, but I ran out of battery.

Bob,
Actually I have seen similar practices in various old hand wired electronics. I expect that the designers were pleased that they figured out ways to eliminate extra wiring steps, terminal strips etc. Older components also were supplied with much longer wire leads than are available today. That allowed such things as the method used to ground the cathode bypass caps to the brass plate in the old Fenders. Why add an extra wire when you already have that long lead hanging off the component. Same thing for components that have a lead routed under the parts board to an adjacent eyelet.
Cheers,
Tom

[Leo_Gnardo]

Conventional wisdom says that all Bassmen are 50W minimum, but I don't think those specs apply to this model.

Having worked on hundreds of them, Fender "50" watt Bass heads usually turn out 40 watts give or take 10% at clip to 4 ohms. What I find with smaller transformers, like the A6A found in Bandmaster & Pro, the waveform starts looking distorted before reaching full power at 40 Hz (low E fundamental) whereas the full size Bassman OT, and modern multitap replacements pass a nice looking sine wave at 40 Hz 40 watts. As long as the transformer isn't breaking down it may be part of the tone to have some "grunt" at the lower frequencies. "If it sounds good it is good."

In a similar format amp, many years ago I got an Ampeg VT40 which had a wrecked baffle. I just cut it out with an electric hand jigsaw, and used the remains to mount a new baffle sporting a 15" JBL. And that my friends was heavenly, no trouble at all "gettin' way down there." In fact one of my customers who ordinarily played an SVT bought that amp to play in his wedding band.

Funny you mention those one inch ports. I call 'em "whistlers." Push enough air thru at low frequencies, that's what they'll do.

[bob p]

yeah, "whistlers." at high volume I could feel jets of air coming out of those ports. they're definitely way too small -- if you play bass at high enough volume then the cabinet ends up pressurizing and the LF will "pump" through those ports as the pressure builds and releases. Fender definitely needed to make them larger. they're too restrictive in their stock form.

You're hard core, Leo -- I do sine wave drive tests for post-repair burn-in, but not for initial check-out. I wasn't quite brave enough to drive the little amp with 40 Hz sine wave ... there's a lot of energy in that kind of LF content and I didn't want to push the amp THAT hard until I got to know it better. It's still got all of it's original caps, and LF sine is a good way to take an amp that's working OK on marginal caps and precipitate the need for a cap job. Ask me how I know!

I guess great minds think alike -- I have an extra EVM-15B that I had thought about fitting in with a new baffle if I decide to make the amp a dedicated bass rig, and a spare 15L if I want to go guitar/bass. but I'm resisting the temptation to immediately hack this amp into a conversion. I'd like to get to know it better first.

One problem with the 15" conversion is that the T-S math says the box volume is a little small for that size driver. Even though the cab is too small for a T-S ported driver, I guess I could always redo the box as a small sealed enclosure. The Ampeg B-15 was an awfully small box and being undersized gave it some of it's charm. Were your JBL conversions ported or sealed?

[Leo_Gnardo]

Were your JBL conversions ported or sealed?

As I recall, sealed box on that VT40 conversion to 15".

On the Ten, I think Fender could have put in a single port a bit larger and spared themselves the "whistler" holes.

Can't say I've ever pushed marginal filter caps to breaking with a low frequency test signal, otoh it's very rare I'll keep old caps in an amp. Of course I look first; any caps leaking goo or with split seals & "pimples" out they go. I may warm up an amp for a while, and feel whether filter caps are warming up themselves due to excessive leakage. It's taken me a while to realize those caps aren't just 20 or 30 years old. Time's gone by - they're 50 years old now, without a doubt time to swap 'em out. Funny I still consider Fender silver faces to be "those new amps," an idea that settled in my head when I was in junior high school.

Now for a quick tale of premature failure. I just fixed a DRRI this week, built 2008. Its main filter is a 47 uF 500V with a 220 uF 100V stacked in series. There's a 470K resistor across the 47, and a 100K across the 220.... why Fender chose this combination is beyond my imagination. In any case the amp was buzzing ominously, and it turned out the Lelon brand 47 uF was just plain kaput. Whaz going on here? Cheap part doomed to fail in spite of being under-challenged? Go figure.