JCM800 w/ 6550.. leaving me uninspired

[Kapo_Polenton]

Maybe I've been spoiled by my lynchbox and the cool Lynch sig. modules that are available to me but I cranked my JCM through a hotplate today and it left me really uninspired. Sounded flat and a tad tubby when opened up and simply put, this thing is seriously lacking in gain. The low end is not a problem... the gain is. Now, I'm not a huge fan of modding this amp by way of putting switches on the chassis etc but a few values I would swap out inside the amp. So my questions are:

1.There are a few known simple mods that can be done for subtle gain.. for example: http://www.mrbobo.com/music_JCM800_mods.htm.
Anyone tried these and liked these?

2.Pushing it with a pedal... I wasn't digging it with my bad monkey. I generally use OD's to tighten the low end and add a slight boost. Not crazy about the bass tone in the first place and that is the problem. I also don't need to spend another 150$ on a good OD.

3. Converting to EL34's. These would probably be less stiff and i understand that 6550's were used for reliability reasons in the first place in favour of EL34's. Would the 34's be a tad gainier in that circuit?

4. Put a PTP board in place of the current board and mod to my heart's content.

Suggestions? I guess I'm just not thrilled by the 6550 tone plain and simple. I guess selling it is an option, but i can't seem to part with the nostalgia of an original early 80's Marshall on my hand. It is the combo version and will also be handy when i have small gigs or practices too rather than lugging a 4 x 12 and heavy ass Randall head. Combos with a mic into the board are perfect for that..

 

[johnpace2]

IMO, Marshall's should have EL34's. Put some Winged C's in there and let her rip. I usually add a little bit of gain with my TS-9 Tubescreamer too.

 

[splawner]

Throw a Boss SD-1 in front of it Gain 9 o clock Level 3 o clock Tone 2 o clock nothing better for me as far as great 80's tone

 

[Kapo_Polenton]

I'll try it, have an SD-1 in the basement I'll dig it out... I think EL-34's would be a good mod though and not that hard to do.

 

[splawner]

I'll try it, have an SD-1 in the basement I'll dig it out... I think EL-34's would be a good mod though and not that hard to do.

Ya throw the EL-34's in you will thank me later

 

[charveldan]

Ditch the hotplate, boost it with a ZW-44 Wylde Overdrive, crank that fugger and thank me later.

 

[Rogue]

How long have those tubes been in there? It might be time for a retube. It won't give you any more gain, or not much if it does, but it may return it to the tone beast it's supposed to be.

 

[Wizard of Ozz]

IMO, Marshall's should have EL34's. Put some Winged C's in there and let her rip. I usually add a little bit of gain with my TS-9 Tubescreamer too.

This + 100

Me no likey 6550s or KT88s in the 2203 circuit. EL34s are where it's at.

 

[Greazygeo]

No need to swap to EL34's and ruin the tone. Really the only difference you will find is way less bottom end and a nasally midrange quality. The Hotplates work great with Marshalls, just don't use the -16 setting or eq switches. Just add either a TS9 or SD1. The Bad Monkey is cool just run the level cranked and gain around 9:00. Same with the other OD's....

 

[70strathead]

I prefer EL34's but I've played through some with 6550's that sounded fine especiallly with humbucker equiped guitars. Also, if you havent tried, set to 8 OHMs insead of 16 OHm into your 4X12. All my Marshalls are set that way and cant explain but it sounds better IMO.

OD pedals

SD-1, TS-9 ( if u want the mid hump), Fulltone OCD, Xotic BB, BOSS Blues Driver, DOD250 all work killer through a stock JMP/800. One thing that i did because i play mostly strats, is swapped out the bright cap in the main input to elinimate that ice pick brightness which the JMP masters were know for having. It tames that and darkens the tone, the presence and treble knob I have to tweak, but it works out for me.

Gotta crank that sucker though unfortunately to get the love. u cant still use hot plate and get great tone, but i wouldnt go past 8 db.

 

[Kapo_Polenton]

Well I think the hot plate is out.. I tried it again and not digging it. The tubes are old now that I think of it.. but damn 6550's are rather expensive last I looked! The SD-1 was a HUGE difference from the bad monkey. More gain and crunch on tap and i ran it level 3 - gain 9- tone 1 as mentioned. Definitely gave me some balls. That said, I found myself playing a lot of thrash alla early metallica and megadeth. I am really interested in picking up a Wylde OD used now to get a little flatter response. Just thinking now that the BB preamp I sold last year would have suited this amp well and I remember thinking it made it feel like a much heavier amp. I used to have a working Blues Driver, that probably also would have worked. I found the DOD OD's to be a bit too raspy with this circuit. OCD I'd love to try out. Any preferences on the version that works best? I like tight and mids, not huge on big fat bass.

I might still do the swap to EL34's down the line but seeing as I already have an EL-34 monster, it might just be good to leave this one as a stocker. We'll see. I'll continue trying to try some other OD's.

Another thing I just thought of, I should check the bias.. a "cold" amp can probably sound stiff and gain challenged from what I remember of playing with my DIY plexi. If I remember correctly, I had read that a lot of MArshall amps and amps in general are shipped biased cold to preserve life of tubes.

 

[steve_k]

Lose the Hotplate. That will just compress the shit out of it and turn the tone to mush.

 

[Kapo_Polenton]

That's what was happening when I cranked it.

 

[Greazygeo]

Well I think the hot plate is out.. I tried it again and not digging it. The tubes are old now that I think of it.. but damn 6550's are rather expensive last I looked! The SD-1 was a HUGE difference from the bad monkey. More gain and crunch on tap and i ran it level 3 - gain 9- tone 1 as mentioned. Definitely gave me some balls. That said, I found myself playing a lot of thrash alla early metallica and megadeth. I am really interested in picking up a Wylde OD used now to get a little flatter response. Just thinking now that the BB preamp I sold last year would have suited this amp well and I remember thinking it made it feel like a much heavier amp. I used to have a working Blues Driver, that probably also would have worked. I found the DOD OD's to be a bit too raspy with this circuit. OCD I'd love to try out. Any preferences on the version that works best? I like tight and mids, not huge on big fat bass.

I might still do the swap to EL34's down the line but seeing as I already have an EL-34 monster, it might just be good to leave this one as a stocker. We'll see. I'll continue trying to try some other OD's.

Another thing I just thought of, I should check the bias.. a "cold" amp can probably sound stiff and gain challenged from what I remember of playing with my DIY plexi. If I remember correctly, I had read that a lot of MArshall amps and amps in general are shipped biased cold to preserve life of tubes.

If the amp sounds bad thru the Hotplate you are not using it right. Find the amps sweet spot, where the power section is just starting to break up with the guitar all the way up. Set it up for the gain level that will get you ac/dc type levels, then hit it with an OD. This should also be where it will clean up with the guitar volume down (with the OD off). That should be pretty loud. Attenuate down from there. -4 -8 and -12 should be fine and leave the eq switches off.

Have you tried the amp cranked without the Hotplate?

Like Ant said, also try the amp set to 8 ohms with a 16 ohm cab....sounds best to me too.

 

[Kapo_Polenton]

Definitely not tried it balls out without attenuation.... the thing is freakin loud on 2 for god's sakes. Listening to the difference between the tubes here https://www.youtube.com/watch?v=CXRhWqNlcNs, the difference between 6550 and EL34 is actually not as drastic as I might have thought. I also here tighter lows and highs from the 6550. I just dug out a pair of NOS 6550 that i got in a deal with this amp. Never bothered trying them out... i think retube, rebias is in order and then we'll see how this things sounds. BTW I had the preamp gain cranked before which would account for some of the muddiness when the amp was opened up and attenuated.

 

[70strathead]

Definitely not tried it balls out without attenuation.... the thing is freakin loud on 2 for god's sakes. Listening to the difference between the tubes here https://www.youtube.com/watch?v=CXRhWqNlcNs, the difference between 6550 and EL34 is actually not as drastic as I might have thought. I also here tighter lows and highs from the 6550. I just dug out a pair of NOS 6550 that i got in a deal with this amp. Never bothered trying them out... i think retube, rebias is in order and then we'll see how this things sounds. BTW I had the preamp gain cranked before which would account for some of the muddiness when the amp was opened up and attenuated.

yep they are loud. The EL34's will break up earlier and compressed more and have the mids. I like this sound, especially with a 50w head. But 6550' take more to break up and have that tighter bottom and highs. My JCM800 is an 82' and had an effects loop put into that was caliberated for an echoplex. so I leave the echoplex on really faintly because it beefs up and adds a certain color ( not a bad color) to the overall sound...almost like a plexi on steroids and tons of warmth
forgot to mention the Cusak V.2 Screamer. its a boutique OD that pretty much can go from a vintage TS-808 with more gain on tap and a open soundind transpaent OD. my favorite OD pedal at the moment

 

[joepete77]

I hate the 6550 in stock marshalls , they are to hard to break up. I had a jmp swithed over to el34 in the past and was much more pleased. An easy mod for more gain is to switch the first 10k resistor on the board to a lower value like a 2.7k or any value in between. I have done this before along with the tube swap and been more pleased with this easy swap then have been with more expensive total mod packages.

 

[Greazygeo]

Definitely not tried it balls out without attenuation.... the thing is freakin loud on 2 for god's sakes. Listening to the difference between the tubes here https://www.youtube.com/watch?v=CXRhWqNlcNs, the difference between 6550 and EL34 is actually not as drastic as I might have thought. I also here tighter lows and highs from the 6550. I just dug out a pair of NOS 6550 that i got in a deal with this amp. Never bothered trying them out... i think retube, rebias is in order and then we'll see how this things sounds. BTW I had the preamp gain cranked before which would account for some of the muddiness when the amp was opened up and attenuated.

It may be a situation where using the amp cranked without the Hotplate you won't like either. A cranked amp doesn't always give great results, especially when the bias is set to high. Things get muddy in a hurry. Generally I find with the gain around 6-7 and master anywhere in the 4-6 range gives a good balance. Than add an od on top of that. Also with Marshall circuits the more the amp is cranked the more you need to reduce the bass.

With NMV amps I like EL34's with MV amps I prefer 6550/KT88's. KT88's are nice cause they have a nice "bend" to them when they clip. Another cool tweak is to swap the bright cap on the gain control to a 100pf.

 

[Kapo_Polenton]

All great suggestions guys.... I think I'll start with the 6550 swap because i have them on hand + rebias. I'm interested in trying the resistor swap as well but to be honest, getting these damn PCB boards up is a pain. I did it when I did the #34 Levi mod and what a b_tch that was working on it without disconnecting all the preamp tubes and some of the other connections.

Cusak screamer I have heard good things about.. Lynch loves or rather loveD it for the longest time before switching screamer type pedals yet again.

Are the KT88 that much different than 6550? Is there more breakup? Also, I trust KT88's are a direct drop in for 6550 or will I have to mod the circuit some?

 

[Greazygeo]

Are the KT88 that much different than 6550? Is there more breakup? Also, I trust KT88's are a direct drop in for 6550 or will I have to mod the circuit some?

KT88's will interchange with 6550's, just bias as needed. They have the same frequency response, but are smoother when they breakup. A 6550 is alittle harder edged.