Vintage AMPEG SB-12 vs new PF20-T?

L

lookah

Sep 21, 2024
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#1
Hello. My first post here ..

I'm building a small project home studio and have acquired a new Ampeg PF112HE cab. Now looking at a vintage SB12 head (there's a few out there) or a newer PF20T. Somewhat surprisingly, I'm having a hard time finding any comparison between these two. Anyone had a chance to play them side by side? The earlier SB12s had 7868 power tunes (which I've read are closer to 6V6s) and the pf20-t is 6V6s. So at least the output should be somewhat similar...

Thanks

Luca
 
#2
7868 were/are a "stronger" tube with 19 watts max plate dissipation compared to the 6V6GT of 12 watts max. There are adaptors available to sub 7591A or 6GM5 tubes. EH for one is offering new stock although I've not myself ever been "happy" with their offerings usually resulting in power loss, but still "sounding" good.
 
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#3
lookah said:
Hello. My first post here ..

I'm building a small project home studio and have acquired a new Ampeg PF112HE cab. Now looking at a vintage SB12 head (there's a few out there) or a newer PF20T. Somewhat surprisingly, I'm having a hard time finding any comparison between these two. Anyone had a chance to play them side by side? The earlier SB12s had 7868 power tunes (which I've read are closer to 6V6s) and the pf20-t is 6V6s. So at least the output should be somewhat similar...

Thanks

Luca
Click to expand...
Haven’t had the good fortune of playing through an SB12, but here’s my recommendation to ya. I love the pair!
 

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#4
Factor in that the new amp will be reliable and comes with a warranty. The tubes are readily available. The 20T can be operated without a speaker connected, directly into your converter box. It’s more versatile with outputs.

A vintage SB-12 amp may require some work which adds to the price, requires a speaker of dummy load box at all times, has harder to source tubes.

The pre-amp tone stages are the same in the two.

I like them both but would go with the PF-20T for studio use in a heartbeat.
 
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#6
In the early 1970s (to the best of my recollection) I brought home a used SB-12. I'd just switched from guitar to bass. It sounded weak, no punch at all, and all I was doing was practicing in my room along with records. I took it back a week or two later and came home with a used B-15. World of difference. I'm sorry but I can't tell you what shape the SB-12's head was in, or what shape the speaker was in, or even if it was the correct speaker vs some blind swap. It wasn't distorting or breaking up, it just lacked muscle of any sort and sounded "meh".

[EDIT: Fix SB-12 description]
 
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#7
Appreciate all the super helpful the feedback so far! The pf20-t def has its modern advantages and might be the obvious choice. Should say I do own a Ironman attenuator so the load box/DI line out can be achieved with the SB12. I'd still be interested to hear if anyone has compared the two side by side?
 
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#11
the sb12 is one of my favorite amps of all time. they sound so sweet and theyre just beautiful pieces of american industrial design, not to mention bass history. the 60's "blue checkered" style has that classic deco aesthetic that is just so cool. note that the 60's version transmitted the speaker signal through the cabinet latches, so it needs its original cabinet unless it has been modified with a speaker jack. the 70's version had a speaker cable but its the weird (but clever) 4-pin xlr style, so you would need either an adapter (from fliptops.com) or for it to have been modified with a standard phono jack as well.
i have three sb-12s. two need servicing!
...so i agree that for studio work, the pf 20 is definitely going to be more versatile, for the reasons beans-on-toast mentioned above, and probably more dependable... although on the other hand the 50 year old amp was hand-built to last in New Jersey with relatively simple and robust components, where as the PF line is built in the far east with cheap parts, surface mounted circuit boards and mass production levels of quality control. I owned a PF20 and i was personally never overly excited by the tone; though i don't doubt they're capable of sounding great, maybe with some tube swaps. i much prefer the PF50 i have now as i feel it has a bit more "bite" or "grit" or something.
In keeping with well established Talk Bass conventions, i can only recommend that you just buy both!
 
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#12
blastoff said:
the sb12 is one of my favorite amps of all time. they sound so sweet and theyre just beautiful pieces of american industrial design, not to mention bass history. the 60's "blue checkered" style has that classic deco aesthetic that is just so cool. note that the 60's version transmitted the speaker signal through the cabinet latches, so it needs its original cabinet unless it has been modified with a speaker jack. the 70's version had a speaker cable but its the weird (but clever) 4-pin xlr style, so you would need either an adapter (from fliptops.com) or for it to have been modified with a standard phono jack as well.
i have three sb-12s. two need servicing!
...so i agree that for studio work, the pf 20 is definitely going to be more versatile, for the reasons beans-on-toast mentioned above, and probably more dependable... although on the other hand the 50 year old amp was hand-built to last in New Jersey with relatively simple and robust components, where as the PF line is built in the far east with cheap parts, surface mounted circuit boards and mass production levels of quality control. I owned a PF20 and i was personally never overly excited by the tone; though i don't doubt they're capable of sounding great, maybe with some tube swaps. i much prefer the PF50 i have now as i feel it has a bit more "bite" or "grit" or something.
In keeping with well established Talk Bass conventions, i can only recommend that you just buy both!
Click to expand...
haha. I hear all that. longer story...i'm namely a guitarist and became a handwired/tube amp junkie after a bad experience bringing a PCB tube amp to a NYC tech many years ago. They were so reluctant to open it up and deal with it that it took 6 months of nagging to get it back. i immediately sold it and started schooling myself on servicing older amps and have acquired a nice collection since.

at the very least, now that i've ordered a bass cab, i can run many of my old fender amps into the pf112. one of them being a 68 showman reverb -- which seemed good enough for jamerson on the live marvin gaye footage.



but the sb12 is still appealing because 1) well, it means more gear! and 2) it's a dedicated bass amp 3) has the low volume mojo

certainly could order a pf20t to compare and always return it.

i don't think we're on the same coast or i'd see if you wanted to let go of one of your sb12's!
 
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#15
There is a distinct difference between the sound of a SB-12 and the B-15N. To my ears the SB-12 was designed as a companion piece for the Ampeg Baby Bass. It works very well in that application. I think that the PF 20t has more in common with the B-15N . so that would be my choice based on my experience playing a SB-12 and a B-15N. Just my take. As I remember the SB-12 is @ 15 watts RMS. Just my take of course.
 
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#16
Ric Vice said:
There is a distinct difference between the sound of a SB-12 and the B-15N. To my ears the SB-12 was designed as a companion piece for the Ampeg Baby Bass. It works very well in that application. I think that the PF 20t has more in common with the B-15N . so that would be my choice based on my experience playing a SB-12 and a B-15N. Just my take. As I remember the SB-12 is @ 15 watts RMS. Just my take of course.
Click to expand...
thx Ric, that's all very useful to know. the sb12 is 25watts from what i'm seeing
 
#17
I checked the 1967 product brochure and you are indeed correct that the SB-12 is rated at 25 watts amps RMS. Since Ampeg was always pretty conservative with their power ratings it’s,probably closer to 30 watts while the B-15N was conservatively rated at 30 watts. So the the Portaflex double baffle reflex design and its larger 15” speaker made it sound fuller.
 
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#19
My SB-12 has been dead reliable. One tube shorted and took out 1 resistor in 25 years of use.

It was my stage guitar amp for a few years and is always my go to recording amp for guitar. I record bass with it when I want vintage rock sounds.

Mostly it is my practice amp and sounds very sweet at low volume. I sometimes jump the latch connection with a cable I built for the task , into a 115 with a JBL D-140 in it.

If you can find one for a good price I say do it!
 
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