Randall RG100G3 Too Bassy

Mitch21

AlanRatcliffe

Preamp valves aren't biased, but any valve gets hot. When working hard, Mosfets get hot too (and they work better when they are hot - up to a point). So it may well be in normal range.

Whether it's too hot, I don't know - you'll maybe have to compare to another example or check with the shop you bought it from.

Gearhead

Mitch21 wrote Im not sure if maybe the 12at7 is biased too hot, and its heating up the interior?

It probably is not, but even if it is - you wouldn't know this by the temperature it reaches anyway.

Alan Ratcliffe wrote Preamp valves aren't biased

Don't want to be a nitpicker, but just to be accurate: invariably preamp tubes are cathode based. This means that there is an 'automatic' biasing system that, up to a point, compensates for the tube characteristics. A tube with a lower internal resistance will draw more current, which will give more voltage drop across the cathode resistor which will bias it cooler, so that it does not run as hot as it would with fixed bias.

Mitch21

Cool, thanks for the info.

I think its just me being paranoid, its my new baby, so you can probably understand ?

AlanRatcliffe

I usually only get worried if things reach the point where I can't touch an amp. ?

Speakers usually warm up and soften up with use - new they are brighter and tighter. So I don't think it will get better - probably a little worse.

Mitch21

Gearhead

You're looking for a way to take out stuff below 80Hz, not affecting your guitar tone.
Edit: I have only been able to find a RG100ES schematic, so I might be talking sh!t here:
The coupling caps in the tube preamp are all .02 already, so the well known mod (0.047 to 0.022) that tightens up a lot of bass is not possible. There is a less known mod, in which you make one or more of the cathode resistor bypass caps smaller. This will effectively lower the gain underneath a certain threshold by (depending on the bias) about 6dB, perfect for your application. It works like this: the cap is essentially always a highpass filter, increasing the gain of the stage by limiting the voltage swing of the cathode. If it is 'too' small, low frequencies will saturate the cap so there is cathode voltage swing and the stage looses gain. Trouble is while modding, to get the frequency (cap size) right. There are some 10u caps in (small already) so you could try a couple of 5u, 2u or 1u to see whether you like the mod. You can get away with fairly cheap electrolytics in those positions, so it's a cheap test.
Is it only in the red channel or also in the green channel?

AlanRatcliffe

Is it not a panel vibration you are getting - part of the cabinet resonating with the bassier stuff?

Karel-Mars

Hi Mitch

On the heating side: Usually you need to keep the heat below 75 deg C, otherwise the plastic starts melting. That is pretty hot btw. A friend of mine has a infra red temp reader, and I have measured heat on a variety of objects. See if you can get someone to give you a reading of the actual mosfets on the heatsink.

Bass floppiness: I would try to isolate if it is a cabinet problem or an amp problem. I don't really think there is a problem though. Do you have an external cab you could connect?

I usually do not evaluate an amp before I have put a 100 hours of music through the combo/amp/speakers. The electrolytic caps need running in to perform optimally. There is a lot of difference of opinion on this topic, but try it for yourself. Connect your iPod/mp3 player to the aux in/FX return/Lo Z input and set the sound to the best/cleanest sound possible. Keep it running at a comfortable level for days on end. Switch off/turn down to save relationships with neigh bours/wife/loved ones, switch on again when you go out or when the neighbour does rebuilding to his/her garage etc.

I reckon you should start getting a better sound after 24/48 hours.

Mitch21

bENDER

This might be dududuuuu stupid....but in what size room do you play? I have the RG200 and the bass does get a bit heavy, but I play in a room of about 4mx4m...even in a room of about 8mx8m the bass was heavy. I blame it on resonance!!! Whahahaha!