| Author | Message | ||
     Mike H |
Anyone have any good mods to the limiter channel? I see that the later models modified the limiter tone stack to match the clean channel to include a mid shift -- I'm sure this reduces some of the mids that can muddy the limiter channel. Anyone try anything else? Let me know what you did and how you like it. Also, I have an early RD without the mid switch. Anyone who has the later model, how do you like the mid switch? Is it a pull out knob or what? | ||
| Pie Man |
test | ||
| Ed Goforth (ed_goforth) Username: ed_goforth Registered: 06-2006 |
The later Mid shift model switches where the older model has the clean/limit swutch. It works good for fattening up a single coil, but humbuckers sound somewhat too midhonky. Depends on what you are doing. The later RD-50 cathode on the first 12ax7 stage V1A has a 560k plate resistor and a 5.1k 2.2uf cathode arrangement. second stage has a 3.3k with a 2.2uf cap on the cathode and the plate resistor for V1/B is 330k. The older RD-50 had 470k V1A plate and 5.1//2.2uf cathode. V2B has 4.7meg plate and the cathode goes to ground. This would make limiter more compressed or muddy. I have reworked this limiter so that the lower gain settings are very much the stock vibe of the RD but as the gain is brought up, it gets more articulate and crunchy with a good blues/rock tone. The gain is actully incresed from stock at max settings with this mod. Some folks have adressed that on the older RD, the limit channel is not brite enough, the later RD was somewhat too brite. The later has a brite cap over the gain pot to briten it up, but can be swapped for a value to taste. I also like to replace the power supply caps with higher uf rating for the main high voltage (6L6) supply. The stock 2uf also gets replaced with a higher cap for tighter, less mud, less noise and also change out the rectifier diodes to FRED's Much better transients a nd les harshness like that of a GZ-34 rectifier tube. Try to find a EV SRO Alnico 12 or a Weber Michigan 12 and get the magnet saturated! The rest of the mods are my big secret :^) This amp is capable of blowing a Mesa Mark I out the window! Think classic Robben Ford and Michael Bloomfield tones here! Also a set of T.A.D. 6L6 short bottle blackplates should sound killer in these as well. | ||
| Ed Goforth (ed_goforth) Username: ed_goforth Registered: 06-2006 |
I have come across some mods to the limiter channel as well as the clean that were posted on Ampage. There is a mod that changing the plate and cathode resistors and caps on the 12ax7 stage open the amp up and gives it more headroom and less mud. More usable overdive from sweet blues to singing leads similar to a Plexi or D*MBLE ODS. These mods are more advanced and should be done by some one who is very experienced. These changes really make a difference! Adding ceramic caps across the top and middle lugs of the volume controls can take off some harshness. The schematic shows a 50 pf across the volume of each channel, the mod indicated something like 500 pf on the clean and 1500 on the Limit volume pot. I have tried this and it does smooth things out and warms it up. Its easy enough to add the caps to the pots. It also seems to add a nice compression. The Limit mods were more intense but very effective. This is a starting point, each player and the pickups etc. may need to vary the values somewhat. I liked 500pf on the Limit channel since I also use the neck pickup a lot for solo's and it lets some highs through to make the neck pickup sing. If you use the bridge a lot, more capacitance makes it compress and sound fatter to an extent say 1500pf. | ||
| Mike (mike_h) Username: mike_h Registered: 06-2006 |
I need to check this board more often. Here's where I'm at now on my limiter channel. my filter caps are up from 60uf to 100uf and from 2uf to 4uf, might try 10uf. I've tried all sorts of values of caps and resistors for the 12ax7. I finally threw in the towell and made mine like the lastest version of the RD50. Still don't care for the sound of the limter channel with a 12AX7, but it gets better, almost usable, with a 12DW7. The lows are still too loose, but the tone is better. Hadn't thought about the rectifier -- might give that a try. Any other hints are welcome as always. | ||
| Mike (mike_h) Username: mike_h Registered: 06-2006 |
I also changed made the tone stack in the limiter channel match the clean channel. | ||
| Mike (mike_h) Username: mike_h Registered: 06-2006 |
I've thought a lot of the rectifier mods and I guess this allows faster power conversion so quicker power tightens the lows? Which FREDs do you use? I'm not familar with FREDs. Are they a drop in replacement for the 1N4003 working in the same bridge configuration? | ||
| Mike (mike_h) Username: mike_h Registered: 06-2006 |
I've thought a lot of the rectifier mods and I guess this allows faster power conversion so quicker power tightens the lows? Which FREDs do you use? I'm not familar with FREDs. Are they a drop in replacement for the 1N4003 working in the same bridge configuration? | ||
| Ed Goforth (ed_goforth) Username: ed_goforth Registered: 06-2006 |
My "Special" mod takes care of the loose bowel lows... Much more articulate and usable. | ||
| Ed Goforth (ed_goforth) Username: ed_goforth Registered: 06-2006 |
If you go check out "Tone Quest Report" there is a article on the fred's there. Ed |