RM100: Low end problem?

Discussion for both Egnater & Randall modular amps

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Post by JKD » Thu Mar 22, 2018 12:34 pm

Stuff like that can drive you crazy, I doubt you are crazy...would be interesting to see the spectrum of both amps.

Having own enough ENGLs and Dual Rec type amps, I know what you mean about them....I just haven't experienced any lack of low end in teh room here but then I'm not really looking for it either. For all I know it's a factor of the design / transformers whatever.

The only way to know for sure if your amp is acting up would be to try someone else amp though :-/
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Post by Mattfig » Thu Mar 22, 2018 2:32 pm

Just thought I'd chime in once more and remove my suggestion of BBE or the like....Most suck pretty bad since you can't put that magical low end where you need it....But, I will add, if you can find an Aphex with Big Bottom, they play REALLY nicely with RM100s....I have two Aphex C2 units for this reason...

If you get an EQ (which is an easier and more direct option), just be sure it can run at line level.... :)

Cheers and best luck,
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Post by Rilke » Fri Mar 23, 2018 2:57 am

JKD! Exactly!! It's exactly stuff like that which can drive you crazy (trying to find low range, which maybe isn't needed anyway haha). During the last recording I checked the response of the RM100 vs an earlier recorded Dual rec with a PAZ analyser (same cab), which seemed to suggest that a Dual rec ("unfair" comparison I know considering the low-end in that particular amp) had a lot more info going on in the 60-150 region than the RM100 through the Mamba module. This is of course so unscientific that it's laughable but it kinda leads me to the thought that the RM100 just rolls off at a higher EQ point.

When looking at the amp specs (particularly the coupling capacitors), the RM100 has a higher value input CC than the Rec, which should suggest that the RM100 should be dark. Of course the Rec is build dark as a mofo and along different design specs than the RM100, so the 1:1 comparison isn't at all valid in this case, but the RM100 should (on paper, and listening to other peoples experience) be dark. I stumbled upon an article regarding the KH100 that they changed value on the coupling capacitor near the power amp to make it even darker voiced (which suggests a higher value there).

So my thoughts atm are that my RM100 might at some point in history perhaps have undergone a capacitor change (I'm a recent owner of the amp so I have no idea of it's history), perhaps towards brigter cap values.

As you say it might just aswell be a design factor which isn't really easily fixable.

And yes, the only way to know for sure would be having another RM100 in the room and A/B'ing (live in Denmark and my RM100 seems almost to be the only one I can see in the vicinity).

Atm my thoughts are to bring it by my amp-tech and have him check it through and through, and consult him on a change of CC-values at some point in case he can't find anything wrong.

Mattfig! Cheers, totally forgotten the line level thing thank you! You might have saved a couple of bucks and headaches there :) Aphex C2 units aren't really up for grabs around here (again Denmark :/ ), but I might go grab one.

Anyway, I think my next step is to check with a line level EQ in the series loop (see what happens), but also grab the head and hand it off to the amp tech, and see if he finds something. I've had it by him earlier in an unrelated repair, so don't think he went through it there.

Could be brillant if it was something wrong with the head and I've started this whole thread because of a broken amp. Somehow crossing fingers that this is the case (in that case I sincerely apologize for this novel), but if it's not, then a CC change/mod might give me my lacking lows.

Lastly if have a Erect mod incoming so depending on the low's in that mod, my problem might reside in the C3 in the preamp modules, instead of the amp in itself.

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Post by iekobrid » Fri Mar 23, 2018 9:28 am

Have you tried running the RM-100's preamp signal out into a different head or power amp, to try to identify where the issue really lies?

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Post by Rilke » Wed Mar 28, 2018 5:19 am

Alright! Back at it again!
I've just tried (pr Matt's suggestion) running an EQ in the series loop (had to dust off an old TC G major unit to find something that runs line lvl). And lo' and behold, there was the low end. I found that with a 3-4 db boost, relatively small Q, set somewhere along the lines of 90-130, the thump of the amp comes through, and matches favorably up to other to thump of other highgain amps.

I would imagine that this is obtainable with a capacitor change somewhere along the line aswell (have contacted the amp guy regarding this and waiting to hear his suggestions), so I won't have to run an effect just for the thump, but I can testify that this does indeed make the amp much more pleasing in regards to establishing the thump.

I must admit that I can't rule out that this is just a problem in my amp (which may have been modded at an earlier point to become tighter unbeknownst to me) but if you have a low-end problem, a line level EQ unit does indeed fix up the bottom end.

I'll prolly update this thread once more, once I've heard back from the amp tech regarding possible mods within the head itself, as I could imagine that it might be of interest to others who feel that the amp lacks a bit in the sub-low department.
Anyway thanks for all the helpful comments! :)

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