Tremolo Intensity and Negative Feedback in Older Fender amps

[bassisst90]

Hello all. I've been looking to increase the tremolo intensity of my BFDR and my ULSFTW for a long time now. Tried slowing the speed of the tremolo, changing to a vactrol, cutting out the lamp and using an led instead, but none of those really helped the intensity. It barely seems to pulse when its on 6-7 and I'm unsure why. Anyone know of any way to achieve this goal?
On another note, I've been trying to install a resonance control on the ULSFTW, just to try it out, and I'm unsure that its working properly. I really just want something to sound like the headroom has been lowered even though its still not gonna be as low as a BFTW would be. Anyway, there are two wires connected to one side of the feedback resistor, one to the extension speaker jack and the other to the transformer. When I attached the pot to the feedback resistor and the speaker jack, leaving the transformer connected to the feedback resistor, it would go to stock sound then silence as soon as I moved the pot. I then tried putting a pot between the feedback resistor and the two wires together, and I got stock sound and a tiny difference in sound but nothing different enough to call this a modification. Is this correct or am I doing something wrong?

[sluckey]

What is "ULSFTW"? A schematic would be a big help.

[echuta13]

UltraLinearSilverFaceTWin? 

[tubeswell]

You put a new roach in? Replaced the trem tube?

[SoundmasterG]

The problem with the roach trems as used in the classic Fender circuits as far as getting more intensity out of the trem aren't due to the parts used....it is due to where the signal is injected. Fender does it after two stages.....Silvertone did it after one stage in the 1484/1485 and those have a fantasic sounding trem that uses much the same parts as the Fender circuit. Moving the trem injection point earlier in the amp can be done, but it causes other issues because Fender takes advantage of the channel mixing resistors to inject the trem where he does. The Silvertone trem only works on one channel, though either can be made to inject into the preamp earlier and work on both channels too. I did this on my brother's Silvertone and it works great. I forget at the moment how I did this....I'd have to look at the schematic, but I probably added a couple mixing resistors where it injects if I had to guess. If you would like to know for sure I can take a look at the schematic and get back to you.

You could also duplicate the effect you get from moving the trem injection point to an earlier part of the amp by increasing the amplitude of the trem signal but that is harder to do.

Greg

[bassisst90]

Yea, I was abreviating the BFDR- Black face deluxe reverb, and ULSFTW was Ultra linear silver face twin reverb. Sorry about that.
O.K. I see. I never thought of that. Thank you. If you wouldn't mind taking a look at these schematics, it would truly help me out

[SoundmasterG]

Yea, I was abreviating the BFDR- Black face deluxe reverb, and ULSFTW was Ultra linear silver face twin reverb. Sorry about that.
O.K. I see. I never thought of that. Thank you. If you wouldn't mind taking a look at these schematics, it would truly help me out

I'll take a look and see what I can find as far as what I did later tonight and post back.

Greg

[bassisst90]

Thank you very much Greg. I really really appreciate it!!!

[SoundmasterG]

I finally got a chance to look at the schematic of what I did to my brother's Silvertone 1484 with the trem. To make it work on the Fender, you would need to add a mixer section with a couple resistors like they do on the Fender....a couple 220k's would be fine, but the problem with this is that it will reduce the gain over what you have now if you add another mixer stage in there. In my brother's amp it didn't matter since I was redesigning the whole preamp but in a Fender where you are expecting a certain amount of gain then it may be an issue. I'd suggest to try it and see. So coming off the plate of each of the first preamp stages, you would add a series resistor before the tone stack, and after each resistor you would have the signal from the trem.....but if you only want it on one channel then just add a series resistor after the coupling cap and before the tone stack and inject the trem there. See what you think....you should have more intensity.

Greg

[bassisst90]

O.K. I'll try that out. So I'd add the 220k resistor to the plate of v2 if I just want it on the second channel then?

[SoundmasterG]

O.K. I'll try that out. So I'd add the 220k resistor to the plate of v2 if I just want it on the second channel then?

Well take a look at the Silvertone 1484 schematic. On my brother's amp I initially moved the trem to the same place fender has it in their amps after two stages because I was adding a Fender reverb circuit to it. The effect of that though was to greatly weaken the trem effect, which I didn't like. So I moved it back and copied the Silvertone setup for the trem, though my setup is slightly different because I used a different preamp setup on channel 1 with an EF86, a cathode follower, and a Fenderish tone stack. I used a switch to interface the trem signal to each channel with channel two the same as the Silvertone setup. Channel one goes right to the plate of the EF86 through a cap to block the DC and I don't need the isolating resistors since I use a switch, though I kept the resistor on channel 2 because my brother wanted that channel to be stock. Sticking the trem signal at the plate of the EF86 made for a very intense trem effect, and the Silvertone already has a nice and intense trem on the stock channel two anyway so you can imagine. I left the reverb setup the same as Fender's with the two mixing resistors. It works well and I can move the trem effect from one channel to the other or completely off so you get max gain.

Hope that makes more sense?

Greg