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#1
Alright i sniffed around some schematics and the JCM and Laney LC15 are really similar in preamp terms (different power amp with different tubes of course) so i decided to turn my laney into a real amp, a jcm800 build 2203. There wasnt much to figure out about it, i just compared the schematics of the two amps and wrote down the differences & changed the components needed to eliminate the differences in my laney. These same mods could be done with many amps that have 3 preamp gain stages with a fourth cathode follower and a tone stack after it. Its a common design used by many amp makers, just marshall was the pioneer at making it sound awesome


1. Put a 100pF cap between the 6th and 8th leg of the first preamp valve (V1)

2. Short out C4
Replace C3 with a 22nF cap

3.Replace R7 with a 470k resistor and add a 470 pF cap parallel to it

4. Replace C5 with a 1nF cap

5. Short out R8

6. Remove C20

7. Add a 470pF cap parallel to R11

And there you go, 100% identical preamp to the JCM800, with a fraction of the cost, in the shell of the cheapest push-pull valve amp in europe. Does really have that marshallish vibe now and the overdrive is not as fuzzy as it was before, its pleasantly smoother.

Edit: It took about a hour to do the mods because i wasnt familiar with its circuit board before, and didnt cost anything because i already had the necessary components at home. Even buying all the components would cost 5 dollars or less i figure, definitely worth the money in my opinion, but judge it by the clip.

Heres a sound clip with the first 25 seconds from the unmodified laney and the second half of the clip with the marshallified preamp (crappy guitar playing from yours truly). the mic was absolute crap though and the clip lacks warmth because of that. sounds better in real life

http://rapidshare.de/files/38465471/lc15.wav.html
Last edited by 1337void at Feb 1, 2008,
#4
I didnt bother to take pics but ill do it tomorrow if you guys are interested, and sound clips too. though it still has that cheesy speaker so its no instant miracle! still a great improvement though.

Void out!
#7
tagged
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#8
if your not lying im gnna go buy a lanely tomarrow along with another handle
Member #5 of the UG Luthier's club.
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EDIT: t heff wins the for the best response.

Quote by carousel182
i im gonna have to agree with t heff
#10
I doubt he is lying. Preamps make up most of your tone so changing it around will make all the difference in the world. The power amp will have an effect too so it's not going to make it sound 100% marshall, but I'm sure it gets it a hell of a lot closer. I'd just like to hear clips is all. I totally beleive the claim though.
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#11
why would it be illegal? i know because its fun.. well no its not illegal
Member #5 of the UG Luthier's club.
member #3 of the vermont cult
Member of the Frank Zappa Fan Club. PM deadhead313313 to join"

Quote by LightningRider
T Heff, No shit I'm a n00b

Quote by Will_Minus

EDIT: t heff wins the for the best response.

Quote by carousel182
i im gonna have to agree with t heff
#12
cord i love oyu im gonna have to agree
Member #5 of the UG Luthier's club.
member #3 of the vermont cult
Member of the Frank Zappa Fan Club. PM deadhead313313 to join"

Quote by LightningRider
T Heff, No shit I'm a n00b

Quote by Will_Minus

EDIT: t heff wins the for the best response.

Quote by carousel182
i im gonna have to agree with t heff
#14
how much did the transformation cost and was it cost effective?
those are real questions for this thread.
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#16
Quote by TheDev01dOne
Yeah this seems pretty awesome. A 15w JCM 800 could have some interesting applications!

Did you learn this from a website or something or just figure it out yourself?

I want before and after soundclips!


He's not gonna be able to get a 'before' soundclip now, is he?

Unless he already recorded something a while ago I guess...
#19
They're finally finding out how easy it is! I like EL84s, what's wrong with them?

Don't stop with those upgrades... just keep on upgrading! Definitely upgrade the output xformer and tubes. Might want to use higher quality coupling caps as well.
#20
first off, this rules and you are a legend

2. soundclips

3. pics of the custom parts to help a noob understand

4. could this be done with an LC30?

thanks man, if i could do this mod its more or less solved my which amp dilemma
#22
Hmm, I would like to mod my VC30 actually... But then again I really should restrain myself.

Got any schems for the VC15 or VC30, TS?
The Laney Thread are big and clever. No exceptions.
#24
Ah I see, ohh I never realised the LC15 had 4 triodes in the pre!

Oh, and as a hint for another mod, change R21 to 470. As it's a Vox-style PI, as with all Vox style amps, that resistor is set at 1.2k+, which runs the PI quite cold. Change it to 470 like on most other amps - and especially the JCM800 - and you'll eliminate a bit of that nasty upper-end harshness in the dirt you get with the Vox-type amps.
The Laney Thread are big and clever. No exceptions.
#26


What might be a good idea is just to wire a little trimpot or something in there and adjust it to taste
The Laney Thread are big and clever. No exceptions.
#28
Wow, VOID FTW!
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#29
Damn after playing it a few days i can reassure it really sounds great. when cranked and having a boost in front of it its instant metallica - kill em all tones. with lower gain and some eq adjustment its ac/dc or bluesy rock. the break up is very natural compared to what it was like before.
really versatile in gain terms indeed. no wonder the JCM800 is hailed so greatly. really is voiced very well.
#30
how hard of a crunch is it and does it have alot of the gain like the ones slayer or dokken or loudness used?
Member #5 of the UG Luthier's club.
member #3 of the vermont cult
Member of the Frank Zappa Fan Club. PM deadhead313313 to join"

Quote by LightningRider
T Heff, No shit I'm a n00b

Quote by Will_Minus

EDIT: t heff wins the for the best response.

Quote by carousel182
i im gonna have to agree with t heff
#34
Throw in a Celestion V30, and thatll help alot im assuming, since that whats in the 1960 cabs, and that should help out with the tone. I wonder if theres something like this you could do with a Valveking. Laneys are a tad more expensive in the States, so maybe try and mod a VK next?
#36
Wow...thats actualy pretty amazing. I'm going to look into all this and see what I can do to help out my VK.
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#37
Wait. Isn't the jcm 800 100 wats? And the lc15 is only 15 so does the watage increase just from changing those parts on the preamp?

This mod might be great to have a jcm800 playable at bedroom volumes.
#39
Quote by superbadboy2
Wait. Isn't the jcm 800 100 wats? And the lc15 is only 15 so does the watage increase just from changing those parts on the preamp?

This mod might be great to have a jcm800 playable at bedroom volumes.


wattage does not increase
#40
Please rehost sound clip!
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