Enjoy the benefits of a premium membership!
Upgrade Account
-
TalkBass has been independent since 1998. Add your voice.
Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
Join free Log in
Want zero display ads or expanded classifieds tools? Compare plans.
GK rails in a pedal?
- Thread starter sprag
- Start date
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
BTW, I just removed the J113 front end buffer and tried mine in its place and there's zero static on the pot. mine has a lot more gain though and it seems to have more of the fizzy decay that I don't care for.
With Q4 collector connected to Q2 there is some asymmetrical clipping. With Q4 collector connected to Q1 the clipping is symmetrical. We can put a SPDT switch in the circuit, so that you can have a choice of clipping modes. Try the jumper to Q1 and let me know if you hear the difference.
OK, so opamp buffer it is!
-Frank
And one last check for the input buffer and pot static... can you drop an NPN in for Q7 and see if that makes a difference?
-Frank
-Frank
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
yeah I can do that.
BTW, to me, there's not a lot of difference between the sym and asym clipping but I think that I slightly prefer the asym clipping.
BTW, to me, there's not a lot of difference between the sym and asym clipping but I think that I slightly prefer the asym clipping.
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
just tried it with a 2N3904 (with no other components changed). the static is more pronounced. it's also duller sounding than the J113, so I prefer the Jfet.
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
BTW, I also hooked the foldback switch back up and there's no oscillations anymore. it's very subtle but when engaged it seems to be a little better than without it.
Thanx for the info John!
Try 3K3 for R19 and R20 for a more dramatic effect in the foldback, and let me know if foldback is a keeper or not.
When foldback is clipping the signal, Q1/Q2 are not clipping to the power rails. You are clipping the the signal at the base of Q1/Q2, I would think that it would sound more like a RAT distortion, because they are similar in operation.
What value of R7 do you want for max output?
These are the changes for V5 that I have so far:
Quiet input buffer, use U1b
Keep asym clipping, Q4c to Q2b
Change Q1/Q2 bias resistors to 47K
Keep R16 1K, high gain
Let me know if you can think of others that I haven't listed.
-Frank
Try 3K3 for R19 and R20 for a more dramatic effect in the foldback, and let me know if foldback is a keeper or not.
When foldback is clipping the signal, Q1/Q2 are not clipping to the power rails. You are clipping the the signal at the base of Q1/Q2, I would think that it would sound more like a RAT distortion, because they are similar in operation.
What value of R7 do you want for max output?
These are the changes for V5 that I have so far:
Quiet input buffer, use U1b
Keep asym clipping, Q4c to Q2b
Change Q1/Q2 bias resistors to 47K
Keep R16 1K, high gain
Let me know if you can think of others that I haven't listed.
-Frank
It is starting to sound pretty awesome. It really is cool how you guys collaborate over TB. Where else can we see genius like this working together to make something new and exciting. I can't wait to hear (and hopefully use) the final product.
Not very much design (except for open source projects) will happen on forums. Most designers will hold their cards close to the vest.
-Frank
Exactly why this is such an incredible treat to witness happen. Best stuff I've seen here on TB in a long time, if not ever. Thanks to you both for your selflessness and creativity!
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
as far as adjustments, that's all I can think of at this point Frank.
i'm thinking that I might want to have a switch to switch between asym and sym clipping since it's so easy to implement.
the same goes for the foldback.
I already have the foldback switch on mine so i'll also add a sym/asym switch to it and post some clips tomorrow of all four options/settings.
I also try 3k3's for R19 & R20 to see if it's better (or worse).
hopefully the opamp line amp will will alleviate the static on the input level control.
the saga continues.........................
John, connect a series 0.01uF and 10 ohm resistor from the junction of R1/R2 to ground... this should help dampen that fizzyness of the amp ringing on clipping transients.
-Frank
-Frank
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
added the 10n & 10R from R1/R2 to ground and here's a quick recording of it at full input level.
it still has a bit of a fizzy decay that would be nice to get rid of (at least more than i'd prefer).
hopefully you can hear it on this recording.
[Invalid or Expired Link Removed]
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
after comparing all four combinations of the switches for the sym/asym and foldback/no foldback modes, I think that the symmetrical and foldback NOT engaged is the best.
IMO, since it so subtle between any of the settings, I don't think having the two switches is necessary at all, so I wouldn't include them in V5.
the symmetrical mode also has the best sounding decay.
IMO, since it so subtle between any of the settings, I don't think having the two switches is necessary at all, so I wouldn't include them in V5.
the symmetrical mode also has the best sounding decay.
Last edited:
- Feb 16, 2008
- 21,240
- 23,634
- Disclosures
- John K Custom Basses
BTW, I just added the TY-250P and tested its tone using its output (VR2)
there's no top end so it sounds very dull. I used an A1K pot for VR2 and it's output is A LOT lower than using VR1.
there's no top end so it sounds very dull. I used an A1K pot for VR2 and it's output is A LOT lower than using VR1.
This is great stuf!
These are the changes for V5 that I have so far:
Quiet input buffer, use U1b
Change to sym clipping, Q4c to Q1b
Change Q1/Q2 bias resistors to 47K
Keep R16 1K, high gain
No foldback
The 1K VR2 drops the tranny output by 6dB. If you use a 5K or 10K the output will be higher, but you will need to find out what taper pot feels best.
We may also need to AC couple the primary coil because its DCR is only 170 0hms. Try a 10uF capacitor in series with the primary.
-Frank
I am thinking that some of that fizzyness might be from clipping noise finding its way back into the front end. Let's see if the better input amp in V5 helps before diving in too deep with this one.
-Frank
-Frank
