Marshall lead 12 'Vintage Mod' or champanzee your 80's hi-gain SS practice amp

[sonic66]

Everyone  who has used a Marshall Lead 12  will know that it sounds thin and only really sounds any good with the gain near max, 

Well this might qualify  as my first authentic mod....



Having previously i 'd  changed R1 to 1M and got a very hi-gain sound.  Now i changed the volume pot to a 100k C pot for smoother volume control,

and also the bass pot to 100k C for more bass control(?)


So thinking about the 'sound of resistors' more than the implications of the change in valve of resistance i decided  to change R1 to an old 1K carbon comp resistor,

and suddenly the amps in a whole new territory ...  could even be described as warm and having tone!

Of course running though  two eminence Beta 12s  has helped a great deal

but overall the character of the sound would be far more of the 'vintage' than JCM  800

clean then with compression.mp3 - 0.62MB

compressor+ SD-2crunch.mp3 - 0.20MB

compressor+SD-2lead.mp3 - 0.37MB

gritty -then with compress.mp3 - 0.35MB

compressor boost level + max gain on amp.mp3 - 0.37MB


theses clips were recorded with a Shure 57 through an Audiotrak Inca88 quickly and shabbily... to give an idea of the sound ( rather my playing skill or lack of it )


If you have slow connection give them time to buffer ... i have never used this host before so i' don't know how long the clips will be up



Observations.

1.While the pickups should be loaded down by this (?) placing a boss compressor in line doesn't  seem to change the attenuation of highs much ,though does make it sound punchier a little richer.

2. The best point to use this at is just before breakup so that heavy playing doesn't make a kind cracking distortion  ( which was there before the resistor swap anyway) . The  guitar volume rolled up or the level on the compressor or other pedal used to push it well into breakup.

3.  This mod is a bit of a one trick pony. The eq is set with bas an treble both 8-10 range and the mid way low at about 2-3 at most , a lot of mid will sound smothered wooly. The clips that have been recorded are with a ibanez LP  copy with Seymour Duncan SH1  bridge pickup the tone on both rolled down to  about 7. 'clean level on the amp is about 7  then it suddenly gets gritty and overdriven above that. The  sound at those settings  is about right .. but it was a one trick pony before anyway. It takes booster   pedals  quite well as there is not too much gain to begin with.
   
4.  the sound has a lot of nose this could be due to the old resistor, or its low valve , which is probably a 1 watt too , a 5532  as a replacement for the LM1458 might sound cleaner, though might not work with the 1k resistor

though these changes will be unlikely to make it sound much better with the existing speaker and cab, which both keep it thin sounding and if too much mid is used it will be worse by far.




If anyone wants to suggest other changes, for R4 , R5, C1 or R7 , perhaps i've started the ball rolling  so as to turn this amp into a cleaner monster.