Increase headroom in bassman 50W

[JimmyM]

Funny, but, the last time Bill Fitzmaurice was asked about the fridge, he claimed that, if you cut it in half ( longways ), it would be actually more efficient and just as loud. I never could tell if he was being sarcastic or not.

He was dead serious.

 

[chadds]

Who said that?

#31

But hey my interpretation. Could actually mean top of his spectrum.

Hey Foxen nice tone on your sample. Your Selmer sounds quite usable. Your settings seem to accentuate more highs and mids. That would make less wattage usable. Some bassists aren't doing the Rotosound grind and need low clear boom which requires watts.

Personal preference our mileage may and does vary.


Happy Thanksgiving y'all.

 

[b-b-b-bass]

My rig is a 50W tube head (originally 100W, but with 2 of 4 output tubes pulled), going through a 1x12 Beta-12A ported cab. It is totally capable and appropriate for bar/club gigs without PA reinforcement.

The Beta 12A speaker works well in both sealed and vented cabs, and is quite efficient. I say "go for it" and put them in your cab. The 1968 2x12 bassman cabinet is about 5 cu. ft. internal, and as long as it is sealed, is a perfect size for a pair of Betas. It will be loud and punchy with 50 watts, with a response curve very similar to a SVT 810 in the low end, and a bit less in the high end.

 

[BassmanPaul]

50w selmer with active 5 string, not really opened up so its still clean

I must admit I always liked the TB50. If I had my time over again I'd have bought one instead of the VOX AC50 that was my first amp. i rebuilt the VOX using the TB50 pre-amp schematic, twin channels and all. It was a much better livelier, amp after the rebuild.

 

[Pilgrim]

I had an old Blackface Bassman 50 for years. It was well maintained and all that.
I had great speaker cabs and all that.
While it sounded wonderful for what it was; it "was what it was," and I could never have gigged it.

clearly, ymmv with this, as the wide range of posts indicates.

I owned a 1967 blackface Bassman until earlier this year - 46 years. I had the caps replaced and a grounded AC cord added. Since I stopped playing with big bands (dinner jacket bands playing Glenn Miller, etc.) in 1973, I never used it for performance. Even the Hartke 1400 solid state amp I bought in 1997 (140W into 4 ohms, 80W into 8 ohms) outperformed it for $99.

IMO a Bassman makes a great practice amp and an amp for jazz and small room settings, but not for volume. It makes a nice sound up to about 4 on the vol knob, and at 5 it's about as loud as it will get. E string farting was common with my original 1967-vintage Fender 2x15 cab, so I moved to other cabs and sold the Fender.

The handiest thing about the Bassman is the four inputs - two for Bass, two for "Normal". That makes it easy to connect a sound source to the high input and your bass to the low bass input. This makes it an outstanding practice amp.

I sold it to my guitar player. By today's standards it's a great guitar amp, but a marginal bass amp for anything but practice or very low-volume gigs.

I play a Genz-Benz Shuttle 6.0 now, and it outperforms the Bassman in every respect. Even better, it weighs 3.75 pounds, not 30.

I truly appreciate the vintage look of the 60's Fender and Ampeg gear, but look isn't sound. I use what works best for me. (Heck, I'm pretty vintage myself.)

 

[Bowe]

Amps don't have loudness, db is a function of speakers.

Actually amps can be (and in some places are) measured in dBW, which makes calculating the SPL level of an amp+speaker combination easier. The real problem is how the wattage is measured, as many amps are spec'd at clip and others are 3dB (or more) before clip. Then of course is how the amp is voiced, which gets into the perceived volume but that is an entirely different battle.

That being said, the speaker efficiency is much more important to the total dB(SPL) than the amp is. If you consider a 1000W amp can only add 30dB and the average speaker is well over 90dB.

 

[Sid Fang]

I'm really surprised no-one else has mentioned this, but if you really want to get the most audio out of a limited power budget, in addition to sensitive speakers, another thing to look at is taking very low frequencies out of the input. You could build (or have built) a very simple stomp box that does this, or you could use a graphic equalizer stomp box (it would need to be a pretty big one though, 10 bands or so) and seriously cut everything below 80Hz. I know that sounds counter-intuitive - we're talking about bass, after all - but what people actually hear in bass parts is above 80-100Hz, and the additional volume you can have when your amp isn't struggling to force your speaker to reproduce very low frequencies will likely more than make up for it. At some point you're going to need more than 50W, but if you really like the sound of your amp, investing in signal conditioning like this could extend the scope of its usefulness.

 

[Martin Beer]

I'm really surprised no-one else has mentioned this, but if you really want to get the most audio out of a limited power budget, in addition to sensitive speakers, another thing to look at is taking very low frequencies out of the input.

They have! Post 45, with the recommendations for different types of HPF. I have also had good results taming the low-end response of valve amps by reducing the value of the cathode bypass capacitor in the first preamp stage. In Fender amps this is 25uF which lets pretty much everything through.

 

[David Jayne]

Don't tube amps tend to roll off the low end anyway? I thought the output transformers did that for you to some degree.

 

[Mr. Foxen]

Don't tube amps tend to roll off the low end anyway? I thought the output transformers did that for you to some degree.

They do, but at the output, it doesn't save you any power, and contributes distortion, which triggers the 'at x% THD' part of the watt rating limit.

 

[David Jayne]

They do, but at the output, it doesn't save you any power, and contributes distortion, which triggers the 'at x% THD' part of the watt rating limit.

Ah gotcha. It's too late to help at that point.

 

[Mr. Foxen]

Ah gotcha. It's too late to help at that point.

It does help with speaker limits though, less likely to fart them out and suchlike. Not generally an issue with 50w head though.

 

[David Jayne]

It does help with speaker limits though, less likely to fart them out and suchlike. Not generally an issue with 50w head though.

Yep I'm with ya. Makes sense.

 

[webmonster]

So... back to the OP's questions
The amp's looks, tone and vibe - he likes them, but not enough headroom.
After a sevice/recap for a true evaluation of what the amp is like, what next?

Post #8 about (slightly) modding the 50 for 6550s would increase headroom. I imagine this is easily reversible.
Post #14 about *not* modding an unmolested amp to retain its value is equally compelling, especially if you could sell it to help buy a louder amp.
Post #68 slight mod of reducing the value of the cathode bypass capacitor in the first preamp stage to roll off some very low bass for more headroom.
The posts about high efficiency SPL speakers/cabs - all sensible.

So much comes down to how much money does he want to spend?
Is this amp is 'the one' for him? Good tone, good price, mint condition etc?
Would a Bassman 100/135 be a better starting point? - same tone and looks (but slightly taller/wider)
If he replaces the 12" drivers, would a Bassman 100 fit on the 2x12 if he changed amp later on?
Fender has 'matching' 2x15 cabs, but they're bigger to schlep around.

*If* the look and tone of a silverface Bassman *is* 100% what he wants (but louder) what is the 'most sensible'* course of action.

* 'most sensible' need not be 100% rational e.g. some of us really like classic cars even though a modern car would be more sensible for lots of reasons.