sluckey wrote: ↑Wed Jan 08, 2020 4:55 pm
Take a look at this Supro schematic. Basically the same as your trem circuit. Don't be concerned with the component differences in the oscillator. But look at the circuitry between the oscillator plate and the cathode follower grid. There's an extra RC filter stage. Your circuit has one, the Supro has two. These filters help smooth out the LFO (trem) signal and also act as a voltage divider to reduce the LFO signal some more before hitting the CF. I think it would be worthwhile to add the extra RC filter to your circuit.
If I understand correctly, you're not 100% sure how the trem was implemented in the original?
That is great! Thank you for the information and for the intel. I think the Boderline circuit is also similar to the S6698 (attached). I am happy to try the circutry between the oscillator plate and the cathode follower grid. I will check if I have all the componentes needed.
As far as the Borderline I am 100% sure the schematic is correct and as per original. Sergio was the original tracer and I spent a considerable amount of time double checking everything. But it is not working for me so happy to make it work in other ways!
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That schematic is burned into my brain! I want to see a complete schematic for Ry Cooder's Borderline Special amp. I don't think it's in this thread. If the schematic does not exist then please post the schematic/layout you are using to build this amp.
sluckey wrote: ↑Wed Jan 08, 2020 5:41 pm
That schematic is burned into my brain! I want to see a complete schematic for Ry Cooder's Borderline Special amp. I don't think it's in this thread. If the schematic does not exist then please post the schematic/layout you are using to build this amp.
No such thing has been made as neither Sergio or I are interested in the rest of the amp to be honest. But it is just a ODS with different presence and different GNFB nothing that is unfamiliar. Therefore it is just plugging this into an ODS
erwin_ve wrote: ↑Wed Jan 08, 2020 4:04 pm
Rafael: Before putting the 820 Ohm in could you check:
What is your plate voltage of the trem triode (that has a shared cathode point with the tonestack cathode?) and the plate voltage of the tonestack triode?
Off to measuring this:
(I) with the tremolo circuit not grounded at all
1) tremolo circuit completely disconnected via the toggle between PIN3 of the tonestack and PIN8 of the tremolo driver, that means that the cathode of the driver is floating
a) ZD (plate of the driver): 296V
b) ZC (plate of the LFO): 294V
c) XA (tonestack supply): 228V - and PIN1 149V / PIN 6 146.7V
2) tremolo connected via toggle and connected via footswitch
a) ZD (plate of the driver): 95V
b) ZC (plate of the LFO): 94V
c) XA (tonestack supply): 232V - and PIN1 223V / PIN 6 149V
(II) with the tremolo circuit grounded
1) tremolo circuit completely disconnected via the toggle between PIN3 of the tonestack and PIN8 of the tremolo driver, that means that the cathode of the driver is floating
a) ZD (plate of the driver): 261V
b) ZC (plate of the LFO): 256V
c) XA (tonestack supply): 227V - and PIN1 149V / PIN 6 146.9V
2) tremolo connected via toggle and connected via footswitch
a) ZD (plate of the driver): 203.6V
b) ZC (plate of the LFO): 203V
c) XA (tonestack supply): 230V - and PIN1 179V / PIN 6 147.8V
sluckey wrote: ↑Wed Jan 08, 2020 4:28 pm
If you turn the intensity to zero does the pumping sound go away? If so, can you turn the intensity up to get a good trem effect without the pumping? Or does the pumping begin as soon as you touch the intensity pot?
Now checking this:
With Master and Volume at 12 o’clock, and Speed at Zero: the intensity pot works as a volume for the ticking, which increases (as far as loudness) as I turn the pot open
With Master and Volume at 12 o’clock, and Speed at Max, the ticking starts very strong from the beginning of the Intensity but the loudness of it does not change as I turn the Intensity pot open
Both audios attached
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2) tremolo connected via toggle and disconnected via footswitch
a) ZD (plate of the driver): 204.1V
b) ZC (plate of the LFO): 202.3V
c) XA (tonestack supply): 229.6V - and PIN1 179.3V / PIN 6 148.2V
Basically the same as when the circuit is connected via footswitch
erwin_ve wrote: ↑Wed Jan 08, 2020 4:04 pm
Rafael: Before putting the 820 Ohm in could you check:
What is your plate voltage of the trem triode (that has a shared cathode point with the tonestack cathode?) and the plate voltage of the tonestack triode?
I added a 1.5K in parallel with the cathode resistor (making it 820R). The ticking is still here but less loud although still very pronounced
norburybrook wrote: ↑Wed Jan 08, 2020 10:38 am
have you tried chop sticking leads around for the ticking? On my Bandmaster reverb with a ticking trem moving a few wires made a difference.
Just a thought.
M
Thanks for the suggestion Marcus, I will give it a try. I also want to try some different AX7s to make sure its not the tube.
My ticking is more like a motorboat than what you would have on a AB763. Attached a recording first turning the volume up and then the master up. I don’t remember the exact settings I had on speed and intensity (as I recorded this some time back) but can assure they were between 12 o'clock and 3 o’clock
Tried a couple different 12AX7 and same issue..can rule that one out
I noticed that there is still a loud pop when engaging the footswitch (Fender Style). I disconnected the tremolo from the footswitch just to make sure the ticking was not a ground loop originated there, no difference.
I just tried the S6698 topology on the driver tube but with a 250k Intensity pot instead of 500K and .05uF before the 2.2M instead of the .03uf
I added the 6.8M resistor (I experimented all the way down to 4.7M) and the .1uF across the pot (I also experimented with .05uF).
With this Supro driver most of the pumping is gone. I only have it with Intensity pot at Zero or from 3 o’clock. Opening the Speed intensified it. The issue becomes the fact that the tremolo effect is super super subtle...specially with Intensity and Speed anywhere before 12 o’clock, almost cannot tell it is on
So I guess a safe bet would be to convert the Borderline trem to this Supro circuit exactly. Or to Sluckeys one..
You're getting closer to the Supro circuit. Now, take it all the way! Connect the trem output to V1 pin 3 rather than V3 pin 3. And use a 1.5K with 35µF on the cathode of V1. I believe the 35µF cap also has a smoothing effect on the trem signal. And injecting the trem in the first preamp stage as Supro did will result in a stronger effect.
Take a look at the Supro schematic I linked. I know this circuit produces a strong smooth trem effect. Xtian has built this same circuit. Maybe he'll chime in.
