Other Amps

Is This Doable?

1

I have a Peavey Delta Blues amp I decided to sell as I need to unload a couple amps. Lovely amp,just not using it as much as I should. I'm shooting a bit high ($475) as I don't need to sell, and today finally got a guy who is possibly interested in a trade for a Ampeg Reverberocket. Link From the pic's it looks to be in good shape,will know more this afternoon.I believe it to be more likely a '65 as I think they used 6V6 before then.It's my understanding that they went to 7591 for less distortion as Mr Hull was a jazz purist. The 6v6 amps are apparently more sought out hence more sellable. A vintage amp in good shape should ,in general, be easier to sell . That said I'll probably trade and toy with it awhile. Looking at the schematics it looks like it'd be easy to rewire for 6v6, but what I'd like to try IF it's doable would be to add a 5PDT switch somewhere not easily gotten to that would switch the wiring from 7591 to a 6v6 and back as desired. Preferably the switch would have a lock out feature to prevent any mis tripping of the switch. Does anyone know where such a switch may be found?

3

Well, I guess I should have said where I could find one switch. They have 25 minimum order. Also, the plate voltages are 450v , so I assume the switch would need to be rated that as well?

4

I have a 64 Reverberocket with 7591 tubes and there is nothing wrong with it's overdrive. I know they changed from 6V6 to these to keep them cleaner but it overdrives just fine. For me it's no problem because I also have a '60 Tweed Deluxe that does the 6V6 overdrive... Both beautiful, just a bit different.

5

It's more of an itch I have. The 7591's are fine I'm sure . I had the thought that someone has done what I described and had the roadwork figured out.I've played several other Ampegs but they were all converted.Killer amps all in their own way.

6

Well, I guess I should have said where I could find one switch. They have 25 minimum order. Also, the plate voltages are 450v , so I assume the switch would need to be rated that as well?

– Opie

Perhaps this: https://www.arrow.com/en/pr...

Note that since the switch will be operated only when the amp if off (and capacitors allowed to discharge), the relevant parameter is insulation resistance.

7

I have both a Delta Blues (my second, bought after I realized I shouldn't have sold the first) and a mid-60s Reverberocket with 7591s. Of course you know they're very different amps - you too may be sorry for selling the D Blues.

You should buy the Ampeg outright, and you'll never be sorry about that either.

Not for any reason, not on a dare, not to please my mother, would I change a THING in the Reverberocket - much less the tube complement. I don't think these amps are about breakup, for most players; they're about an incredible unique clean tone and delicious reverb. But they're not high-powered amps with TONS of headroom, so you can crank'em for a grind at (really big and tolerant) room volume.

Before I bought it, my amp was used to record an entire album, cranked to the bejesus, just for its tone. Guy who sold it to me said if it was more loud-gig-worthy, he would have kept it.

Ifwhen you get it, please live with the 7591s for a good long while before deciding to hack around at it. If you end up modding it, please don't tell me.

8

Hull lived in my hometown. Met him when I was 14. He was anti rock and roll and the idea then (shocking!!) was that distortion was a Bad Thing to be engineered out of a design. They even had advice not to turn the amps over half volume. It was a different world back then. He quit the company he started because he wanted nothing to do with the direction things were going.

Ampeg experimented with new tube designs way more than Fender who mostly stuck with the same old stuff. Reverbrockets are cool and not too expensive. 7591s got expensive for a while because all the Japanese tube audio dudes were buying up the old stock. Then it was reissued.

9

Having it home and spending a little time with it I probably will not change it. Great sounding amp,as Proteus says, nice clean yet with a tad of hair at low volume, balls out as it cranks. Very old school which suits me.Thar be magic in those bottle tubes.It has been modified, the accordion and mic inputs are now a standby and dc switch,whatever that is. It hums quite a bit, likely filter caps,or perhaps a preamp tube. Also sounds like a tremolo motorboat thing happens when bass goes above 5. Volume drops considerably when reverb is pushed.I get time this weekend I'll peak at the innards and see what's what. GG said"Note that since the switch will be operated only when the amp if off (and capacitors allowed to discharge), the relevant parameter is insulation resistance." I thought that might be the case, but am better reassured hearing it.Thanks.

10

Oh, the auto switch would be perfect,why didn't I think of that?

11

Man, I hope someone can help me figure this thing out. I opened it up for a looksee, and discovered I must have some rare bird. I searched the internet for all I could find about these amps ,and not one source has anything like it. This one has 7591's ,no tremolo,just reverb. SS rectifier that appears to me to be half rectified,though I could be wrong.But what is baffling the most is there are only 5 tubes, with the exception of a very early one with tube rectifier and tremolo, no verb. All the various schematics I've downloaded have 6. The serial # indicates 1962, but the tube chart shows 5 tubes, 6v6 with a tube rectifier. To complicate it further, it's obviously been modded with a DC switch to cut plate voltage and a standby in place of the mic and accordian inputs. Why,I've no idea. Also note the diagonal slant to those inputs, of the dozens of examples I've seen online, none has that feature. I hope someone knows of a schematic that matches what I have. Really love this amp, but I got to know what it is in order to get it restored proper.

12

Label pic,

13

Slant inputs,

14

It looks like an heavily modified R12 or R12A. The Reverb is not original and the tremolo circuit is used as part of the reverb. We can see that the original tone control is now treble, speed is now bass and intensity is now reverb. The 5Y3 has been replaced by a solid state rectifier and the DC and standby switches added to allow the proper turn on sequence. One tube (most likely the one between the 7591s and the transformer) has been added to drive the reverb. I may be wrong, but this is my best guess.

15

You may be on to something.I could tell that the reverb tank was new, but you think this was originally a non-verb? The transformer between tubes is for the new reverb circuit which uses parts from the old tremolo? Sheesh Boo Boo, someone really went to a lot of trouble to mod this thing. You suppose the 7591's are not original as well? Why a dc and a standby, seems a bit redundant. Which do I flip first, dc or sb?

16

Look at the "rev" switch. We can stil see the I and part of the N and the end of the Y of INTENSITY. If You're in doubth, remove the stickers which are not original for sure. Look under the octogonal plate with the black wire going through it, you'll likely see the hole for the 5Y3 socket. I did not say that the transformer is used for the reverb, I'm taalking about the tube next to it. Both the R12 and the R12A had only 5 tubes. I don't know what the DC switch does, but the standby is to be used like the one on a Blues Deluxe. Finally, I'm trying to help, if you're not interested let me know.

17

Look at the "rev" switch. We can stil see the I and part of the N and the end of the Y of INTENSITY. If You're in doubth, remove the stickers which are not original for sure. Look under the octogonal plate with the black wire going through it, you'll likely see the hole for the 5Y3 socket. I did not say that the transformer is used for the reverb, I'm taalking about the tube next to it. Both the R12 and the R12A had only 5 tubes. I don't know what the DC switch does, but the standby is to be used like the one on a Blues Deluxe. Finally, I'm trying to help, if you're not interested let me know.

– GG

GG, I sincerely apologize if I came off wrong. I am very interested and am wishing to learn. My sense of humor comes off the wrong way sometimes I guess.

18

GG, I sincerely apologize if I came off wrong. I am very interested and am wishing to learn. My sense of humor comes off the wrong way sometimes I guess.

– Opie

It's O.K. I understand, I have similar problems with my own sense of humor. Don't worry, I'll get used to it.

19

Here is what your amp looked like before being modded. It had volume, tone, speed and intensity control, but no treble, bass nor reverb, and the model number is R12.

20

And the back configuration was like this:

21

Yep,that's gotta be it. I found two schematics online, both which show it with 6v6. I wonder if they ever did these with the 7591's ? From what I've gathered about Ampeg, they could change things from day to day. It would be nice to know what this one had originally before the mod-a-thon. The other thing I noticed is lack of supply caps,mine has I think one 20uf and another 10uf, not the three 20uf you see on schematic. Is that because SS rectifiers require less? BTW, that your amp?

22

There should be a schematic glued to the inside of the back panel. That will tell you how it left the factory.

23

There should be a schematic glued to the inside of the back panel. That will tell you how it left the factory.

– Billy Zoom

Yes, something that looks like this:

24

It most likely came with 6V6. I'll try to summarize the mods that have been done. 1. Change the tone into a treble control circuit; this might involve only a change in compnent values 2. Change the tremolo circuit into a bass control; this is a more significant change 3. Replace the 5Y3 with SS rectifiers or half bridge, adjust the filter capacitor and resistor values to obtain the same voltage. 4. Replace the 6V6s with 7591s shift them into the 6V6 and 5Y3 position, change resistor values where needed. 5. Use the now empty 6V6 socket to install a 6SN7 (most likely), add a transformer to implement the reverb circuit. To come up with a schematic of the amp as it is now, all these will need to be sorted out. It will probably look like a mixture of an R12 (rocket) and an R12R (reverberocket).

25

BTW, my amp is a Princeton Reverb Re-Issue 65. The configuration is not that far from a Reverberocket.


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