69, 1987 Filtering and Tone

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69, 1987 Filtering and Tone

Post by revolver1 » Fri Jun 25, 2021 12:55 pm

Hi All,

Thought I'd share some things I've been trying out on my 69, 1987. I've been having a time of it nailing the tone I want out of it but I think I'm pretty much there now.

First off I should clarify the sound because I know this won't be for everyone, I've been chasing Mark Fords tone from when he was in the Black Crowes.

Probably around mid way through the second albums tour he had acquired a 69 or 70 50w 1987 that I believe was slightly modified by the time they came to do the third album. It sounded pretty stock on the second albums tour but by the third album the sound had changed both in the studio and live. He has used a couple of different second amps but the 50w has always been there since he got it.

I know as with most talented players loads of it is in his fingers but he swaps guitars and uses fuzz and wah and boosts and to me they all sound glorious. I just couldn't even get close with the stock amp. He gets great sparkly cleans by rolling the guitar volume back and great 70's Stones sounds that just remind me of Mick Taylor but he can then also get great heavy rock tones and then this gritty hair on his solo notes oozing with harmonics. Obviously pedals vary one unit to another but even so I have alot if what he has used at one point or another but none of it sounded remotely close for me.

Circuit wise its stock except for the .0022pf coupling cap I swapped out for a .0047pf. This just seems to let a touch more bottom end through to thicken the sound up a touch. It seems to help with the fuzz and wah like it's got a bit more to get ahold of now. The .0022pf wasn't doing it for me, it was just a bit thin and one dimensional.

Mixer, Tone Stack and P.I caps are all silver mica lemco's with a 4700pf bright cap on the V1 Volume pot.

I was messing around with the filtering and this is what really pulled it all together for me. As you probably know (but for those of you who don't) the 50w can be a pain because of the rectifier design, there's alot of ripple in the supply and to top it off the screens and P.I share the same cap can. Also looking for other options for what may have left the factory some late 68ish amps had 40/40uf cans that I can't find anywhere of a decent brand.

First I had 100uf mains 50uf screens, 50uf P.I and 32/32uf on the preamp. This sounds O.K when it's just the amp, quite aggressive but pedals just out right suck and sound awful.

I then tried a dual 32 for the screens and P.I and it did sound better, headed in the right direction but still not very impressive with the pedals.

I then tried a 16/32uf for 48uf on the mains but it was not so good, almost like some of the sound was missing and a bit more noise which was O.K with just the amp but too noisy for me with any boosts or fuzz.

So I put a 32/32uf for 64uf on the mains and this I liked, much more like it with the pedals they actually sounded half decent now. The only criticism was it did still seem like a touch of the sound was missing, not as bad as 48uf but it now ghosts a bit much for me even without boosts.

Out of curiosity I put a 16/32uf on the Screens and P.I, 16uf Screens and 32 P.I. it did give a nice greasy feel but I think it must be the 16uf on the screens seemed to loose a bit of top end or something so the fuzz didn't seem as rawkous, it was just a bit flat.

So now I'm running out of options, I like 64uf on the mains but it ghosts and I like the feel of 16uf on the screens but that makes the ghosts even more angry and it's not so great with the fuzz because of the frequency attenuation.

So I took an ARS 22uf 500v electrolytic axial and soldered it to the jumper between the two terminals of the dual 32uf mains cap and soldered the negative end to the mains cap ground lug. Although I don't overly trust my capacitance meter it at least gives a rough idea of what's going on and I was reading 80.1uf on the circuit side of the cap. I put the 32/32uf back in for the Screens and P.I and still had the 32/32 on the pre.

Wow! This sounds and feels alot more like it. There is the tiniest bit of ghosting but it doesn't bother me at all, it kind of goes away when boosted. I can't imagine you'd hear it at all with a band.

Lastly I felt there was maybe a touch too much gain making it a bit hard edged so I was considering changing the pre amp droppers for a 2w 15k, then I remembered something....
(I have to thank Dave Weyer for this tip from the West Coast thread) this is what really nailed it for me.

I put a Mullard ecc81 12at7 in the P.I and Shazam that's it. It's still aggressive Marshall tone but it has a sort of Fender flavour to it. Almost what I liked about the 16uf on the Screens or lower filtering in general but with out the frequency attenuation or loss of power, if anything it kinda adds something like a good line booster would.

The whole setup feels even more greasy than it did before but it's so much more natural and organic sounding, a bit more interesting and separates it from the herd. Every one of my pedals actually sound amazing at last and makes it even more fun to play wich really should be the point. To my amazement I'm getting all of the sounds I was after, big grins...

The ecc81 12at7 may not be every ones cup of tea but it definitely has a vintage vibe about it that reminds me alot of the Classic tones but it doesn't stop me getting more contemporary sounds as well. :thumbsup: I would say that it is a bit noisier but nothing to really worry about and the benefits far surpass the issue although I still have to put the amp back in its head shell wich may quieten it a tad.

Think I'm going to give one a go in my late 67 100w and see what happens. :rockon:


Chanels jumped.

Presence just before 6
Bass 4
Mids just before 6
Treble 6
V1 just before 4
V2 just before 6

Ts808 settings

Gain 1/4
Vol 3/4
Tone a bit over 1/4

I did try 60% and 63% bias but settled on 65% .

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Re: 69, 1987 Filtering and Tone

Post by danman » Fri Jun 25, 2021 6:54 pm

Glad you finally got it sounding like you wanted! I'll have to try the 12at7 next time I have my 50 watter hooked up.

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Re: 69, 1987 Filtering and Tone

Post by neikeel » Mon Sep 20, 2021 4:18 pm

A 5751 or CV4004 works well in the PI too (IMO of course!)

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Re: 69, 1987 Filtering and Tone

Post by Freebird » Wed Sep 22, 2021 2:57 pm

Thanks a lot for sharing your experience. I also have to give a 12at7 in the PI section a chance the next time.


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