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tubes for big bass

jjhaller

Silver Supporting Member
Messages
690
Any tube suggestions for a Budda SD 30 (1st series) that could increase the bass? I currently have JJ EL-84 power tubes and Tung Sol 12AX7s in the preamp.

Thanks!
 

buddastrat

Member
Messages
14,690
I don't think you're going to get big bass with 84's. I had an SD30 and it was a sweet, barking mid amp. Very round.

The things to do is stick an EQ in the loop and get some low end, much more than any tube change.

Also you could use a big clean power amp as a slave.
 

Timbre Wolf

Hyperspatial Gravity Surfer
Platinum Supporting Member
Messages
10,094
If you do try the preamp tube change, I do recommend '60s short-plate RCA 12AX7A (not 7025) for that purpose. In my experience, they've got very big bottom.



The things to do is stick an EQ in the loop and get some low end, much more than any tube change.
Though it is not an e.q., along similar lines: use a BBE Sonic Maximizer, and emphasize the bass process. The sonic stomp can do this, in a pedal format. Don't overdo it - if you find you have that tendency, consider using a different cabinet instead.

- Thom
 

Doug

Member
Messages
815
I'm not familiar with your amp, but I just put a couple of NOS RFT 12AX7s in my Marshall 1974x on recommendation from Mike at KCA. As one of the above posters mentioned, I doubt you'll get big bass out of an EL84 amp, but these RFTs really fattened up the tone on my 18 watter. It got rid of the grainy-ness on the top end, and just puts out fat, juicy saturated tone. May be worth a try.

I also replaced the JJ EL84s with TAD EL84s, and that helped fatten it up a bit as well.
 

jjhaller

Silver Supporting Member
Messages
690
thanks for the suggestions. I'm not looking to achieve blackface style bass, just a little more umph, particularly at lower volumes. ANy thoughts on the Barber EQ?
 

Miles19

Member
Messages
62
Changing tubes is unlikely to affect the bass at all, as pretty much every tube amplifies all the way down to 0 Hz (DC) with no loss of gain. Bass response is entirely affected by coupling caps, the output transformer, the speaker and its enclosure. I suppose a tube that's weak in high frequencies might make it sound like the bass is being emphasized but I suspect that's not the sound you are looking for.

Miles
 

Timbre Wolf

Hyperspatial Gravity Surfer
Platinum Supporting Member
Messages
10,094
Changing tubes is unlikely to affect the bass at all
I have to disagree - there can be profound change in bass. Have you ever tried this? I have, literally hundreds of times. But tube changes do have a smaller degree of influence than do speaker and/or cabinet changes.

- Thom
 

jjhaller

Silver Supporting Member
Messages
690
I currently run the amp through a Trutone custom semi open 2x12 cab loaded with Austin Speaker Works KTS-70 speakers. The speakers are rather new, perhaps not yet broken in. They sound fantastic every where else in the audio spectrum, and when I pump my Holland Little Jimi, a blackface deluxe type amp, through the cab there is a lot more lows.
 

Timbre Wolf

Hyperspatial Gravity Surfer
Platinum Supporting Member
Messages
10,094
Just a thought: you don't have the cabinet on a stand, now, do you? That'll reduce lows quite a bit, depending on your floor type/size.

- T
 

jjhaller

Silver Supporting Member
Messages
690
Just a thought: you don't have the cabinet on a stand, now, do you? That'll reduce lows quite a bit, depending on your floor type/size.

- T
Nope, on the floor about 6 inches from the wall. I have the option to close the back of the cab, but currently with the partially open option seems to allow the low end bloom a little bit more.
 

donnyjaguar

Member
Messages
4,199
Changing tubes is unlikely to affect the bass at all, as pretty much every tube amplifies all the way down to 0 Hz (DC) with no loss of gain. Bass response is entirely affected by coupling caps, the output transformer, the speaker and its enclosure. I suppose a tube that's weak in high frequencies might make it sound like the bass is being emphasized but I suspect that's not the sound you are looking for.

Miles
Although an output transformer will pass a low signal, the efficiency drops a lot and the waveform becomes very distorted. Lots of inductance and a large lamination stack help here, but that doesn't describe most EL84 equipped amp's I've worked on. The limiting factor is the output transformer and the amount of current the tubes can serve up. The only quick and easy way to improve the latter is to wire the output section in triode. This will of course reduce output power but it will indeed serve up relatively more solid bass.
 

jcarpenter

Gold Supporting Member
Messages
1,829
I would do the eq thing plus the 12 ax7 swap. JJ el84 is the best for that family of power tubes. Speaker would be the next step. If all else fails, then do the transformer triode thing. All the little things put together could get it done. Tone is loosely comprised of 1/4 pick-ups, 1/4 speaker, 1/8 tubes, 1/8 cables, 1/8 (materials wood etc.), 1/8 hands (only if fundementally sound, or this negaites all of this if you lack technique and experiance.)


Happy Hunting
 




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