JCM 900 Help

[Norm Fireland]

Ok i have bought a JCM 900 reissue head about 2 months ago, im sure alot of the people on this forum will be coughing and spluttering at the thought of someone spending their hard earned pennies on this amp.. hee hee i joke i joke!!

Im after an early AC/DC rhythm sound, think she's got balls or bad boy boogie, with my lead sounds tending to be pretty similar to Zakk Wylde (No rest for the wicked/No More tears era). Here is the catch...

The amp is way too trebely, my settings are

Bass 7  
Mid 9
Treble 0
Presence 0

Gain A 8  (Lower gain channel)
Gain B 5  (Higher gain channel)

Master 3-6  and no reverb

I use a Greenback loaded 4x12 and my guitar is a Hamer Korina Flying V with seymour duncan 59's

Firstly, it comes with 5881 power amp tubes, anyone think going to EL34's is a good idea?

Secondly, anyone any ideas on how to get less treble? Im aware that my pickups are PAF type/clones and so can be trebely, but i love that raspiness to them.

Change of Speakers? Hot plate (to crank even more)? Pre-amp valves?

I really dont want to change amp as i have lost way to much money lately on swapping gear about, and i suppose after a list of gear the length of your arm you got to stop.

Any help will be greatly appreciated guys :)

[FELINEGUITARS]

Hi Norm

Definitely change the power valves to EL34s and get it biased for them
Consider changing the pre-amp tubes too and find ones that are full bodied tone-wise

Now - also you're plying a Korina V into the amp
I make Korina guitars and they are bright by nature

Duncan 59s are a good choice but consider trying a BKP VH2
Seems to fill out the sound a bit as well
It's what i have in mine....

Also consider changing the capacitor in the guitar to an oil and paper one - like a Vitamin Q or a Hovland musicap
Will help re-voice the guitar a bit and help it sound a bit more vintage

Also - maybe just back the pickups away from the strings a bit - can help reduce top end and is easy to change back with a turn of a screwdriver if you don't like the result


Or trade the amp in for a JCM800.....

[Jonesy76]

I changed the tone control in my Korina V over to a 300K pot which also helped a bit.

[the_bleeding]

hahah you just have a trebly setup.

marshall/chinese preamp tubes = trebel
korina = trebel
'59 = trebel
greenbacks = LOTS OF TREBEL

for pretubes, i'd reccommend staying away from electroharmonix because they're really trebely... maybe mullards or JJ's for ya... and some people like the chinese 9th generation in their marshalls (like me, i have a mix of jj's and chinese) gives it a nice gritty punch.

my advice would be to put an EQ in the fx loop to round off some of those highs.  Maybe get a bright mod done if you're into that... but it will void your warranty.

5881's are good tubes, they just sound pretty bland, nothing special about them, theyre basically the vanilla tube. el34's will be good and give you more mids and that fabled compression associated with marshalls.  If your jcm900 is a 4100, i'd say stay away from 6550's because they have very high breakup, so your amp will have to be literally taking the neighborhood down before you get any poweramp breakup.

for speakers, you cant go wrong with v30's. Lots of mids, nice and punchy. Last time i tried a jcm900 though, i found that g12t-75's actually sounded good with it, which is a first in my books. So maybe carry your head into a shop and test out some cabs :)

[Crazy_Joe]

hahah you just have a trebly setup.

marshall/chinese preamp tubes = trebel
korina = trebel
'59 = trebel
greenbacks = LOTS OF TREBEL

Treble  

[the_bleeding]

hahah you just have a trebly setup.

marshall/chinese preamp tubes = trebel
korina = trebel
'59 = trebel
greenbacks = LOTS OF TREBEL

Treble  

my bad, i'll pull the hangover card on this one

[HTH AMPS]

I'm curious - why did you buy this amp?  It doesn't seem to fulfill any of the criteria you've outlined.  900's ain't bad amps (imo), but I wouldn't recommend them for what you want.

Changing to EL34s ain't gonna help you I'm afraid - I'd consider them a backwards step since you want more bass and less treble really.  

Get some nice 6L6s and bias the amp up, it'll give you a fighting chance at a 'phat' tone.  I'd go with one of the current small-bottle 6L6 variants (they'll most likely have a WGB suffix).  The reason I say this is that the WGB/small bottle types breakup earlier and have a big thick tone.

Some darker ECC83s will help beef it up a bit but I think you just have the wrong amp.  A 2204/2203 and an SD-1 would have fit your need much better.

 :twisted:

[Norm Fireland]

Aggggh, i had written a really long reply to all the comments so far and my computer crashed, i got to be up at 6 in the morning so ill post tomorrow afternoon/evening!! Thanks for the replies so far though!! :)

[ericsabbath]

put g12t75 speakers and less mids

[fps_dean]

for pretubes, i'd reccommend staying away from electroharmonix because they're really trebely... maybe mullards or JJ's for ya... and some people like the chinese 9th generation in their marshalls (like me, i have a mix of jj's and chinese) gives it a nice gritty punch.

JJs will definitely be too thin for that amp.  I'd suggest finding some NOS German made RFTs.  The current line of Electro Harmonix 12AX7s actually have more mids than treble and while they may be brighter than the JJs, they have a lot more body as well which more than makes up the fact that JJs have a little less high end.

I always run EL34s in my 900.  You probably want the Mullards, with SED "Winged C" being the second choice as they have more mids and Electro Harmonix the third.

[Norm Fireland]

As said in my last post, thanks for the replies, always a wealth of knowledge on this forum (everyone give themselves a big pat on the back) lol.

Feline, As funds are low at the moment, a new set of BKP's is a no go, i do have a set of nailbombs that i dont use, too much of a modern sound for me now i guess, i was playing in a power metal band before. Where could i get the capacitors you mentioned? Any other ways i could make the axe sound even more vintage?

Jonesy, what will the differnece in the tone pot do? Less Treble?

The bleeding, thanks for the advice on tubes!! Whats the best stores? Watford valves?

Heavier than Hell, I bought this amp when i was in my previous band, i'm starting to wonder why i bought it!!  :roll:

Eric Hellstyle, i love mids, gets me to cut through a mix, i dont like g12t75 speakers, they sound too modern to my ear.

fps_dean, again cheers for the info on tubes!!!


To give some idea of amps i have owned, DSL, Marshall 30th Anniversiry head, JTM45, Engl Thunder, Mesa Dual Rec, Fender Twin, JCM800 (4 input)  

The thing with all the amps i have owned (except the twin) is that they just dont have enough dynamics for me. The twin was nice, but not enough balls to it.  The JCM900 has sounded alot better than all the other amps, apart from way too much treble. I read posts all the time on this forum about amps and i get way too jealous. Im probably rambling now, but basically i feel cheated, ive spent so much on amps but none have the right dynamics or enough sheer balls. I may have to just get rid of this one and start again.. Anyone any ideas, think vintage sounds, early ZZ Top, Leslie West, AC/DC with the most agressive sound being Zakk in his first few albums with Ozzy. Kill me... lol

[the_bleeding]

sorry buddy, i dont know any british tube stores, i just live a 25 minute drive from www.thetubestore.com's headquarters (which is in canada).

tone caps are funny to describe though, what they do is remove treble and add bass, but the values of caps determine how much more or less bass you get when your tone is set to 0.

I think that one of the first good things to do to that amp though is to invest into some celestion v30's. They have tons of mids, and the treble isnt as harsh as those greenbacks. After that, maybe look into upgrading those pretubes into something less harsh sounding.  If all is lost, you could look into getting it bright modded, which is where a tech will upgrade some of the internal caps to roll off the harsh treble. Current production Marshalls typically are made with low quality chinese capacitors which are known for harsh treble.  A mod like this shouldn't cost much at all.

Though if nothing works... to get more vintage sounds... i'd really have to say go look at some orange amps and see what you think. AD series is more vintage than the rockverbs.

[HTH AMPS]

Anyone any ideas, think vintage sounds, early ZZ Top, Leslie West, AC/DC with the most agressive sound being Zakk in his first few albums with Ozzy. Kill me... lol

It's really simple, you need a 2204 (50w) or 2203 (100w) model Marshall.  

These are the single channel amps that were the first to feature master volumes in the Marshall range - they also took to opportunity to cascade the first gain stage rather than have parallel bright/normal stages.  This means you get more gain too (yay).

These amps will give you all the tones you're after - for Zakk just add an SD-1 like he does (he's uses 2203s btw).

You can get them in the older JMP cosmetics or the JCM800 - same amps, just the 800s seem to go for more cash with Zakk being a famous user of them.  The later JCM800 2204/2203 amps with the horizontal inputs are the ones to stay away from since they changed the circuit and the build quality is shockingly poor.

Here's what you're after... http://cgi.ebay.co.uk/Marshall-JMP-50-Watt-Valve-Amp-1979-80_W0QQitemZ190155022842QQihZ009QQcategoryZ10171QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 :twisted:

[Mr Ed]

HURRAH! A fellow 900 owner... although, no offense, I wouldn't touch the reissues with a rusty bargepole. They suck.

I've never experienced the trebley problem - my main pickup is a SD JB (quite trebley by nature) and I just roll off the treble, use presence to control the top end, I swapped my speakers out for Vintage 30's and I have a nice mid-range hump to really cut through.

For tubes, definately check out... www.hotroxuk.com

Mine's in the shop at the moment, being biased and having the 5881's replaced with EL34's. Can't wait to get it back.

[fps_dean]

HURRAH! A fellow 900 owner... although, no offense, I wouldn't touch the reissues with a rusty bargepole. They suck.

All the current Marshalls do... that company is in a pretty sad state these days.

Other than the Vintage Modern if you are a strat player.