RM100 sound issue

[Chak_wylde]

Im not sure what is wrong with my Rm100 head. I'm not getting the sound i'm after. It kinda sounds like its under a blanket or something. Theres no punchy low end and theres no crunchy top end and note definition. Sounds ok within like the first 20 min but after that it starts to loose clarity and sounds dull. Sometimes even looses volume after a while. Anyone got any suggestions as to what it could be? I'm playing it through a randall warhead cab loaded with V30's and a JJ6l6gc power section biased fairly low. I'm really thinkng about getting an Engl Savage but just can't afford one atm.

P.s Are there any randall amp techs in the UK?

 

[Julia]

Check your power tube bias. Make sure you warm up the amp (guitar unplugged, MV and channel volumes at 0, and have the amp switched to operating position not on standby) for about 20 to 30 minutes before you check bias. Why? Bias can drift higher as the tubes warm up.

Could be old tubes. Could be bias is set too high (which would translate into looseness of the tone).

If you're running EL34s I'd not bias higher than 33 mV per tube on this amp. Set the bias, then play the amp for about an hour, then before you shut down, turn all the volume knobs to 0 again, unplug your guitar cable from the amp and recheck the bias and adjust as necessary. That way you've biased the amp for when the tubes have really been warmed up.

 

[ak37]

Ditto on what Julia said mate! Check the bias! Too low can give a cold, sterile feeling. More like you are trying to drag the tone out of it. It is so easy to do yet I myself am guilty of changing tubes and not biasing the amp. I went from 6L6 to EL34's and it was HOT! Real HOT and it was awesome for about 10 minutes then I started noticing the smells in the room. I shut it down and the tubes were clicking like a LeCar just off of the autobahn! There is a reference for ya! Anyway, a new set of tubes and a bias later it has been pure bliss! Cheers!

 

[Chak_wylde]

Thanks guys. I think the bias for my jj6l6gc's are at about 33mv. Is that too low then? Also thinking about getting some different tubes. What are 6550 tubes like and how do the 6l6's differ to the 6l6gc?

 

[crankyrayhanky]

no doubt those tubes need replacing!

 

[KillTone]

When I first got my RM100 I thought it sounded too dark and muddy. I made a few changes that really helped. 1) had my modules upgraded by GigMods and 2) changed tubes.

Re: the tubes - The amp came with JJ 6L6GC's and I switched to Svetlana EL34's. HUGE difference. Most of the modules, besides being stock had JJ's in them as well. A lot of people think that JJ 12ax7's are dark and lifeless sounding (in the MTS, I agree). Try some brighter 12ax7's both in the module and in V1. Re-issue Tung-Sols and Chinese 12ax7's may do the trick. A few NOS 12ax7wa's would help big time, but they can be expensive unless you get lucky on E-bay.

Good Luck!

 

[El-Kabong]

Thanks guys. I think the bias for my jj6l6gc's are at about 33mv. Is that too low then? Also thinking about getting some different tubes. What are 6550 tubes like and how do the 6l6's differ to the 6l6gc?

6L6GC is just the latest version of the 6L6 type. New manufacture tubes should all meet the 6L6GC spec. 33mv bias reading on those is fine in the Randall, even the manual allows up to 35mv. That difference won't pull the blanket off the tone.

6550 is a good tube, as is KT88. I have a KT88/KT66 combo in my RM100 right now, and I like it. Big and clear with a nice bottom end resonance. YMMV.