Randall RM50 Combo newbie

[Darkhorse]

Hi from the UK,

Just purchased a new RM50 Combo with Blackface & XTC modules from a guitar store. Will use it to gig regularly with a Classic Rock covers band (Bad Company, Thin Lizzy. Cream etc).
The Blackface module sounds superb but when switching to the XTC, the amp has undesirable backgroud noise (much more so than my Fender Blues Deluxe channel 2). This seems to be the same with direct guitar or via pedalboard. The module sounds great but I'm wondering if I need to purchase a Noise Gate (Boss N2?).
My gigging guitars are (Primary) PRS Singlcut Trem (Secondary) Strat Plus and either Gibson LP Standard or SG Classic (depending on my mood). Whichever of these guitars are plugged in I get the same background noise.
The dial settings on the XTC are GAIN - just past 12'o-clock, TONE - all approx 12'o-clock LEVEL - 2'o-clock.
I purchased the Randall because I didn't like the sound of the Overdrive channel on the Fender Blues Deluxe for the type of material with the current band.
Although a lot of users may suggest I should get a JTM or PLEXI for 70's kind of Rock, I thought the XTC may be more versatile because we don't only do British stuff and the XTC seemed to do the Santana sustain well.
Any advice or guidance would be greatly appreciated.

 

[JKMV12]

As far as noise gates go...the ISP Decimator is among the best. Though before you go buying pedals...try a JAN Phillips 5751 in the phase inverter (preamp tube closest to the power tubes). After doing that my RM80 sounded much better...noise was practically nonexistent. I ended up selling my ISP after that b/c i had no use for it anymore.

Welcome to the MTS world! It won't be too long b4 you catch the mod'd module fever like the rest of us :lol:

 

[Darkhorse]

Thanks for the reply JKMV12,

Wow! - it's just dawned on me that the Randall world isn't just full of tone loving musicians but you guys are electrical engineers as well. I've got a lot to learn.
I haven't seen the ISP Decimator here in the UK, so not sure if I will be able to try it out.
With regard to your advice about the JAN Phillips 5751 - I'm sorry but haven't a clue what this means. Can you explain further and point me in the right direction of obtaining info on how to go about this.

I didn't think it was possible to get all the tone one wants in a single amp, but this RM50 seems to fit the bill - so yes if it takes a little work to perfect it - then bring it on.

Doctor, Doctor, save me from the module fever - I just want to play guitar!!

 

[Mike361]

He means a preamp tube. Buy the tube mentioned, take out your existing tube and replace with bought tube. They just pull straight out, sometimes you have to wiggle a little. Look at pins as they must line up. Hope that helps.

 

[JKMV12]

lol...i am far from an electrical engineer...though i am on the way to learning everything about vacuum tube amps and circuits.

yes the JAN 5751 is a preamp tube. Check either dougstubes.com, thetubedepot.com, or thetubestore.com. analogtubes.com is another good site. Find that tube...buy it...and put it in the phase inverter spot and the noise issue should be reduced. Good luck!

 

[Darkhorse]

Thanks guys,

I now know that a JAN Phillips is a suggested replacement valve for a 12AX7.
These are difficult to obtain in the UK but can be got for around ?25 each.
More readily available is the EH 5751 GOLD (slightly less expensive).

Question: do I simply swap the two valves in the XTC module with two JAN Phillips?

Just in passing - viewed a couple of video's of the Tone King comparing different Randall MTS high gain modules. It seems the background noise was prevalent there too. Maybe Randall amps are just inherently noisier than Fenders.

 

[Mike361]

You can swap any preamp valves you want, but to lesson the noise it is suggested that you put the jan in the phase inverter slot in the amp itself. Also any higher gain module will have some noise when you turn the gain up. All amps have some. Good luck

 

[Daryl]

Thanks guys,

I now know that a JAN Phillips is a suggested replacement valve for a 12AX7.
These are difficult to obtain in the UK but can be got for around ?25 each.
More readily available is the EH 5751 GOLD (slightly less expensive).

Question: do I simply swap the two valves in the XTC module with two JAN Phillips?

Just in passing - viewed a couple of video's of the Tone King comparing different Randall MTS high gain modules. It seems the background noise was prevalent there too. Maybe Randall amps are just inherently noisier than Fenders.

I believe that the suggestion was to place a 5751 in the P1 or phase inverter position(nearest the power tubes in the amp itself) You could certainly use any 5751 in that spot. It is just a lower gain alternative to the 12AX7.
For the valves in the XTC module, I would personally stick with 12AX7. I use the Tung-Sol gold pin ones. They are a little more spendy, but they are low noise. High gain preamps are just noisier to begin with IMO.
I like Ebay and http://www.tubedepot.com/5751.html

 

[JKMV12]

i know the JAN is a bit expensive but it is worth it imo. it is very similar to the 12AX7 but it has less gain. it would also be nice in a mid/low gain or clean module if you want a similar sound to 12AX7 w/o having too much gain.

here is an article that was posted here a while back that talks about the phase inverter. very interesting read. not too technical. hopefully it provides some good insight.

http://www.guitaramplifierblueprinting.com/files/Phaseinverter.pdf

 

[Daryl]

i know the JAN is a bit expensive but it is worth it imo. it is very similar to the 12AX7 but it has less gain. it would also be nice in a mid/low gain or clean module if you want a similar sound to 12AX7 w/o having too much gain.

here is an article that was posted here a while back that talks about the phase inverter. very interesting read. not too technical. hopefully it provides some good insight.

http://www.guitaramplifierblueprinting.com/files/Phaseinverter.pdf

Hey man,
Great little article...
Thanks for posting.

 

[Darkhorse]

Wow - it's been a focused week of learning. Thanks to all respondents for the education.
Reading the phase inverter article was amazing - it explains so much. And maybe why the overdrive channel of my Fender Blues Deluxe sounds so crappy.
I guess you can liken this to using lower output humbuckers on a Gibson LP to obtain a more musical tone. At least that's how I am beginning to understand it.
I will definately order a JAN Phillips 5751 to try out.

Another consideration is that the RM50 Combo being new, the speaker will still be tight and will need to open up before the potential of the amp is realised.
First outing this weekend, gigging with my band (obviously without the 5751 until it arrives). Should be able to see how the RM50 holds up to a bit of Classic Rock.

Will report back as and when - thanks again.

 

[JKMV12]

Wow - it's been a focused week of learning. Thanks to all respondents for the education.
Reading the phase inverter article was amazing - it explains so much. And maybe why the overdrive channel of my Fender Blues Deluxe sounds so crappy.
I guess you can liken this to using lower output humbuckers on a Gibson LP to obtain a more musical tone. At least that's how I am beginning to understand it.
I will definately order a JAN Phillips 5751 to try out.

Another consideration is that the RM50 Combo being new, the speaker will still be tight and will need to open up before the potential of the amp is realised.
First outing this weekend, gigging with my band (obviously without the 5751 until it arrives). Should be able to see how the RM50 holds up to a bit of Classic Rock.

Will report back as and when - thanks again.

what you are talking about with the lower output pickups could be attributed to the fact that a lower input signal into the amp will drive the preamp gain stages less and therefore reduce the amount of clipping. Of course there will still be clipping but the onset of clipping may be a bit softer which would indicate more even order harmonic distortion (the kind of distortion that give tubes their characteristic sound). On the other hand transistors mainly produce odd order harmonics which aren't as pleasing to the ear as even order.

bottom line is that the preamp stages are not being that heavily driven. you can probably achieve a similar and more interesting effect by using a lower gain tube like the 12AT7 in the V1 of the amp. this will increase headroom and decrease input sensitivity. remember that these tubes are dual triodes so they are two gain stages in one tube. so the very first gain stage will not cause the signal to be severely clipped. the second gain stage will induce clipping but it won't be that harsh. it will introduce more even order harmonic distortion. then once you get to the module preamp tubes...they will do most of the overdriving. not the best setup if you are like me and want crushing hi gain distortion for metal...but for lower gain stuff...it might be worth checking out.

Now what i have just said is to the best of my knowledge. I may be slightly off on a few things. Though i am sure that the 12AT7 will give you less gain (amplification factor of like 70) and this will not drive the module as hard. you say that you play classic rock...this might be something worth trying. if you don't like it in the amp V1 then maybe it will sound better in the module V1 or V2. it takes a bit of experimenting. that is one of the many great things about this series. Now as far as brands go i can't tell you much. I have the Mullard 12AT7 and it is pretty good...though it is a bit expensive. I say go for the JJ or the JAN Phillips.

http://tubedepot.com/12at7.html

If i have stated anything false, please correct me. I'm still learning about vacuum tube amps so i could be mistaken on a few things.

Take Care,
John