JCM 800 Mods (1 Viewer)

[PaoloJM]

The purpose of the mods was for warmer, thicker, meatier sounds with more gain at bedroom volumes. In this vid the MV is set to 4 with the Hot Plate @ -16dB and dialed down to half way.
The vid description gives details of work so far.
I'd be interested if your thoughts, suggestions and/or critisisms.
Regards,
Paul.

[ame="http://www.youtube.com/watch?v=7lsnwmeWvNg"]YouTube - Paolo Marshall JCM 800 2203 mods[/ame]

 

[Kermit McDermott]

Sounds fine.

I use 1 of these

JCM 800 4211 which is the combo version of the 2210 head. No mods. I use the pre amp overdrive and a clean boast to push it when needed. Thank god for the master volume switch.

 

[Break Neck Speed]

So have you actually moded yer head or are you just using a hotplate? (i havent watched the video as ive no sound)

 

[PaoloJM]

So have you actually moded yer head or are you just using a hotplate? (i havent watched the video as ive no sound)

Yeah, I've done a bunch of gain and tone mods as well as fitting the amp out for KT77 output valves. The Hotplate is just to take the volume down a bit for recording as the digital camera clips/compresses fairly hard even a lowish volumes.

 

[mark]

Yeah, I've done a bunch of gain and tone mods as well as fitting the amp out for KT77 output valves. The Hotplate is just to take the volume down a bit for recording as the digital camera clips/compresses fairly hard even a lowish volumes.

whats the deal with those KT77 valves? are the more like 6L6s or EL34s?

 

[PaoloJM]

whats the deal with those KT77 valves? are the more like 6L6s or EL34s?

They're more like an EL34 than a 6L6, but have more low end as opposed the the mid ranch "punch" of an EL34 so it lends itself more to metal sounds, IMO. EL34/6L6 is more the whole brittish/american sound thing, Marshall vs Fender etc.
KT77s seem to get a bad rap for high failure rates. KT77s bias a good bit "hotter" than EL34s so are not a simple drop in replacement, you do need to re-bias the amp properly. I think people just see a web article saying saying they're a direct replacement and put them in, turn the amp on and then give out when a month later the valves fail.
Best way is to hear the difference is to try them out in your amp, but do remember to check the bias or have a tech check and set it for you.