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Re: ok , question for SpeedRacer

1/29/2004 2:51 PM
SpeedRacer Re: ok , question for SpeedRacer
Hi Chris:  
To add the bias mod trem, it's probably not a bad idea to back off on the bias but I'd do some measurements first to see if there really is a potential problem. I'm not sure if there is. I probably bias a little colder than most folks though.
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1/29/2004 3:07 PM

What Speedo said....  
The things with bias-mod trem that do it for me are:
1. It's smoother  
2. It's more musical  
3. The volume varies a bit up as well as down,  
so the average sound level doesn't drop off  
as much  
4. You get to watch the blue glow inside the  
tubes pulsing at the trem rate if you turn  
out the lights  
5. It retrofits rather easily into the BF/SF  
6. It much better simulates that "AM station  
drifting in and out" vibe than the  
optoroach does
I have a '66 Deluxe that I did the bias-mod trem circuit mod in, and it is a night and day change from the crappy optoroach trem.  
I also routinely pull out the .02 trem oscillator cap, parallel the first .01 with it, and put in a .03 in the place formerly occupied by the .02. This gives a nicer speed range, IMHO, with a really slow pulse at the slow end, and not disappearing into methamphetamine-like jitters at the fast end....  
C ya,  
1/29/2004 8:42 PM
John G Roach trem-Chris W
Don't forget when you have the Roach trem chassis out open on the work bench and the overhead lighting is illuminating the area, you can have a situation where if the roaches are NOT completely sealed then any light that sneaks in can turn the LDR partially on diminishing the trem depth. I only know this by finding out the hard way ie. by chasing my tail once many years ago.Red faces all round when I did realize what was going on.  
John G
1/30/2004 12:06 AM
Chris ( CMW amps )

Thanks , John !  
Right now , I did leave the tremolo stock except for a speed-tweak .  
Was busy voicing the normal channel for a more blues/swampy sound ( verb/trem on both channels ) and did put the chassis in the cab after testing & tweaking around midnight .....  
Anyway :  
Gonna try a bias-modulating trem too ( later on , some other jobs/projects waiting ) and lower the vibrato-channel coupling-cap to 0.047 or less after removing the int.-pot over there ..... still got my bf Bandmaster with export SR PT , time for a tube-rectifier and a bias-modulating-trem :) .  
again : thanks to all for sharing their experiences !  
Ps blackfacing a late 70s / UltraLineair Fender ain't no fun :D but the cool thing is the bigger OT ( 2 /4 ohms Bassman/SuperReverb size ) compared to the earlier Bandmaster(Reverb) amps
2/9/2004 8:20 PM
Chris ( CMW amps )
thanks to Dutch & Joe
Altough I haven't had the time to work again on that BMR I just did modify a '71 Bandmaster with a Vibroverb 6G16 a like tremolo-circuit .  
WaYyYyYyY nIcEr ! :)  
One cool extra + :  
this one does work without the footswitch / "shorted RCA-plug" connected .  
thanks again ,  
2/11/2004 9:05 PM

Now it may be my imagination, but it seems like a Sovtek 12AX7WA gives a stronger tremolo than US 12AX7's.  
2/11/2004 10:13 PM
Chris ( CMW amps )

Hi Mike !  
Woah :)  
Without kidding : just did convert the tremolo in the BMR and did use a Sovtek 12AX7WA and it does sound stronger compared to the same trem. in a BM with a chinese or UOS us 12AX7 .  
Couple of customers and some buddies did test the amp and everybody's really excited about the tremolo ( besides the other stuff in the amp :) ) .  

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