The 6550 Experience

His guitar slung across his back, his dusty boots is his cadillac.

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Xplorer
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Re: The 6550 Experience

Post by Xplorer » Mon Oct 29, 2018 12:35 pm

Fantastic build Bill !!! And don't listen to these stupid agressive comments .... They simply don't know that this amp can be set differently and totaly produce the woodstok tone or BOG, also using different pickups on the strat.

claiming it sounds like shit and provide a different amp played with a les paul .... LOL

PS : i DO have some pictures of the back of the amps at the BOG Fillmore east show .... and they DO feature Dave's oval white West coast logo .... And the transformers seems very big.
the quality is very low on these images from a film, but to me they're here. Have a look, i've put it online. it was filmed a few seconds or minutes after the Fillmore east went from 1969 to 1970.



Here's an old clip i did with the west coast amp, and the same fuzz that Bill used. + my honey univibe on standby. octavia from roger mayer. G12H30 pulsonic. 69 slider's pickups. See how it can get even more bog with some slight variations. Sorry for the playing, it's not synchronized with the basse etc ... i know.
I just can't wait to try it with Dave's germanium always ON fuzz !

https://soundcloud.com/xplorer80/170618 ... s-extraits

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Re: The 6550 Experience

Post by shakti » Mon Oct 29, 2018 1:49 pm

Great clip Adrien! The basic sound is definitely there. What are the specs of the amp you're using in that clip?
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

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Re: The 6550 Experience

Post by Xplorer » Mon Oct 29, 2018 2:12 pm

Thanks !
Well, it's a metro 69 SL , shared cathod, about 530 V, and Dave's mods. No fancy things. Quite simple.

Then pres 10, middle 10, treble 10, bright vol 7

i'll re do this amp from scratch, with new transformers and leave this metro kit alone, back to EL34.

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Re: The 6550 Experience

Post by shakti » Mon Oct 29, 2018 3:43 pm

There you have it. Basically the same specs as mine. I am still using the stock transformers, but mismatched so the primary impedance is increased. Not going to mod the transformers on mine, it sounds so good already. Besides, we have yet to see clear photographic evidence of a Hendrix amp with replaced transformers.

I recently bought a 1970 Super PA which I am currently modding into stock 69 Super Lead specs with EL34s. Got to have that sound as well as the West Coast sound. V1 (channel 3 and 4) will be stock Super Lead, V2 (channel 1 only) will be 2203 specs. So a different take on Neil's special 2-in-1, where you can get 100% Super Lead specs and 99% 2203 specs albeit with a different (Lar-Mar) master volume.
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

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Re: The 6550 Experience

Post by Xplorer » Mon Oct 29, 2018 4:22 pm

2 in 1 ? i'm not aware of this project, interesting. great to have a west coast and classic el 34 SL 69 all in one amp !
Besides, we have yet to see clear photographic evidence of a Hendrix amp with replaced transformers.
not sure if it's big enough, but here's one of jimi's 10590 SL, which had tung sol 6550 in. As you can read, this amp was spotted on photos from various concerts, including the Fillmore east one ( second page )

article and photos : https://imgur.com/a/e2R0hRa

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Re: The 6550 Experience

Post by revolver1 » Mon Oct 29, 2018 4:38 pm

I need to read the new explosion of posts but just wanted to throw this in.

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Re: The 6550 Experience

Post by revolver1 » Mon Oct 29, 2018 4:40 pm

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Re: The 6550 Experience

Post by revolver1 » Mon Oct 29, 2018 4:40 pm

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Re: The 6550 Experience

Post by revolver1 » Mon Oct 29, 2018 4:41 pm

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Re: The 6550 Experience

Post by shakti » Mon Oct 29, 2018 5:35 pm

Xplorer wrote:
Mon Oct 29, 2018 4:22 pm
2 in 1 ? i'm not aware of this project, interesting. great to have a west coast and classic el 34 SL 69 all in one amp !
Besides, we have yet to see clear photographic evidence of a Hendrix amp with replaced transformers.
not sure if it's big enough, but here's one of jimi's 10590 SL, which had tung sol 6550 in. As you can read, this amp was spotted on photos from various concerts, including the Fillmore east one ( second page )

article and photos : https://imgur.com/a/e2R0hRa

Image
Image
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Yep, anyone still in doubt that Jimi's amps in 69 and 70 had 6550s has not been paying attention. But 10590 also appears to have its stock transformers.

The 2-in-1 is all EL34, it's just that you can get classic Super Lead specs *and* classic 2203/late 70s master volume specs in the same amp. Just a little fun project. I modded a similar Super PA for a friend of mine into Super Lead specs, and the results were so good I wanted to make one for myself. But I didn't want to drill any holes, so I thought...what can I do with the extra channels? Basically I remove the input Jacks for channel 1 and 2, put in 2 new plastic Jacks like they used on the master volume amps, plus two switches, in the four input Jack holes. One switch to switch the input grid to V3 (tone stack) between 1959 and 2203, and the other to switch the .68 across V2a cathode in and out (69-70 SLs had it, later SLs and master volume amps didn't). I'll put up some photos when it's done. It's going to be my go-to Marshall "rock" amp.

The West Coast amp is a different beast - kind of cleaner, more hi-fi. The cascade mod is cool in this when combined with a master volume.
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

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Re: The 6550 Experience

Post by Xplorer » Mon Oct 29, 2018 6:36 pm

Yes, well, it seems to "do it" even with a lower plate voltage. it works at 560 v, it works at 530 v for us ...
and from the article it seems to put out 129 w, but it was tested with el34.

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Re: The 6550 Experience

Post by daveweyer » Mon Oct 29, 2018 8:57 pm

Revolver nice build, exceptionally clean and orderly. It is a proud amp. Jim Marshall wished he could make them like that.

Re:
No evidence of replaced transformers. I'd like to make a suggestion here that the transformers actually had been replaced on that SL in the photo, and not because they are bigger. I would also like to suggest that the measurements were made with the 6550s in the amp--the photo shows the signal generator running and a reading on the output meter, all with the old tubes. Now, with 6550s and a "hot" replacement stock SL transformer, you can get 127 watts output, no problem. For a normal SL with EL34s, that is asking a lot. They will do it with high enough B+, for a while.
The easiest mod to do on those amps was grab a "hot" transformer, say one that provided 560, 570, 580, or even more DC on the power tube plates. These would drop right in without any alterations; Jimi would be happy because the amp was louder and stronger, and no one outside of the inner circle of West Coast, Jimi, and maybe some roadies, would ever be the wiser.
One other mention, the voltage sag also varied with those transformers; if it could supply the current at the higher voltages, you got a real powerhouse of an amp. That is also where the main filter caps enter the picture. I think the words "more hi-fi" captures the situation pretty well. Of course that is where your 3 transistor FF unit comes in.
Sound reasonable to you all?

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Re: The 6550 Experience

Post by revolver1 » Tue Oct 30, 2018 4:05 am

Thank you Dave for the kind words and making all this possible.

Glad you made the comments on the transformers it clears things up for me. So you just used stock transformers with above average out put and good regulation characteristics. Not JTM or 45/100 iron, just stock 69 superlead.

I had read that original amps had a lot of variation in out put unlike the replica transformers we use these days.

Explorer, Great info! Also the sound clips :clap: :thumbsup: blew me away. Very good.
:worthy:

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Re: The 6550 Experience

Post by Tazin » Tue Oct 30, 2018 10:33 am

daveweyer wrote:
Mon Oct 29, 2018 8:57 pm
Re:
No evidence of replaced transformers. I'd like to make a suggestion here that the transformers actually had been replaced on that SL in the photo, and not because they are bigger.
I can tell you that the transformers are original Dagnall T2562 & C1998 units.

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Re: The 6550 Experience

Post by Xplorer » Tue Oct 30, 2018 11:12 am

Well, who knows if the PT wasn't replaced when they reverted it back to EL34 in 1974 .... and maybe they hacked the interior too. That, or a stock hot one, and as Dave said earlier, no one would see the difference.
+ this is one among several others ..... he had some in america, and some in europe.
Anyway, as you can see in the video i posted, all the amps at the BOG show seem to feature the west coast sticker at the back, and the 10590 is said to have been spotted on various pictures, including the bog rehearsals.
+ if you read the article i reposted, there was at least one cab with J.B Lansing speakers 120-F-6, and that would explain the shiny cone center that was discussed here previously, extensively.
i have a picture of one super tremolo he had, and it seems to be a stock transfomer, not a 45/100. But i don't know if it was touched by Dave. No west coast sticker on this one.
Dave, a hot transformer could vary up to such high voltage ? 530 V - 560 V - 580 V ?

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