Just to be clear for the sake of people trying to do your mod, the math on the slope resistor appears to be off. If you bypass the 150K slope with a 68K resistor you get a 40K equivalent. If you bypass the 150K with a 330K, you will get "100"K. Unless I misunderstood your description.
Also, when you say the NLFB is a compression option, do you mean with the feedback engaged you get more "compression"? That was my finding, although I wouldn't call is so much compression as "a narrowing of the bandwidth" with the NLFB engaged, which may sound like compression. But if that is what you found as well, why do you would seek less "compression" when using a Strat, which naturally will sound less compressed than humbuckers due to its lower output? It almost sounds like maybe you and I hear things differently.
Cheers,
Gil
bluesfendermanblues wrote:Mod 1
- 100k slope with
- 22n (Blusier) or 47n (more scoped, more country) - I have settled on 32n bypassing the 10n mid with a 22n cap. The 150k slope is bypassed wtih a 68k resistor.
Mod 1
- 100k slope with
- 22n (Blusier) or 47n (more scoped, more country) - I have settled on 32n bypassing the 10n mid with a 22n cap. The 150k slope is bypassed wtih a 68k resistor.
I have put both on a switch, on the bottom of the chassis, close to the slope/mid cap - flipping the switch and running the Bass control low gives me Classic stack values.
Doesn't 68k in parallel with 150k = about 47k? Don't you need 300k in parallel with 150k to get 100k? I guess I am missing something?
EDIT: Sorry I just notice that Gil already stated this.
i was also thinking of putting the slope resistor on a pot and also the NFB resistor with a 4k7 in series with a 1M to give me positive feedback at max, and 4k7 nfb (stock) at min.
Be real careful with putting the slope resistor on a pot. The Slope resistor carries 200 volts DC and it'll be a very scratchy pot with pure dc on. You wont be able to use it with voltage on the amp. Much better to put it on a switch.
The slope resistor is decoupled by the caps in the tone stack - i.e., there is no DC load on the tone stack end. If a pot is used to replace this resistor, you have the same DC voltage on both ends of the pot, with a net zero volts across the pot. Same principal as the LAM-MAR MV.
That is a killin' Strat tone with one of these amps!! I must follow this recipe, Gil.
ayan wrote:
The very brief clip I'm attaching was recorded during a rehearsal with a handheld recorder. It was intended to show the smoothness and sustain achieved using a Strat on the lead channel with definitely not a lot of distortion dialed in. I shared it with a couple of board members about a year ago after I finished turning one of my amps into a 102 circuit. And while I'm discussing distortion, I found that if the coupling caps are oriented properly, you can dial in the overdrive a lot higher and the amp will not sound so much "distorted" as it will "sustainy." I have discussed this with several people and we've all arrived at this same finding.
In terms of amp settings, I think the key to getting a good sound with a Strat with any Skyliner type amp is to keep the bass dialed low and the preamp volume high.
Lou, the Lar-Mar MV is located after the PI coupling caps and so it has only bias voltage on it relative to ground and no DC flowing. The slope resistor is directly connected to the plate (or cathode in some cases) of the stage driving the tone stack as Vibratoking says, so it has ~200V on it's element, again relative to ground.
The slope resistor will not have a DC voltage drop across it, however, it sits at about 200 VDC with respect to ground, so one needs to be very respecful of that.
Gil
bluesfendermanblues wrote:
The slope resistor is decoupled by the caps in the tone stack - i.e., there is no DC load on the tone stack end. If a pot is used to replace this resistor, you have the same DC voltage on both ends of the pot, with a net zero volts across the pot. Same principal as the LAM-MAR MV.
vibratoking wrote:The slope resistor is fed directly off the plate of V1 and has around 200VDC on it!
Yes, that is correct. But since the other end of the resistor is AC-coupled to the tone stack, you wind up with the same DC voltage on BOTH sides of the resistor, which results in zero volts DC across the resistor. The only time a pot sounds scratchy (assuming it's not dirty) is when there is a DC voltage across the pot. When you've got +200V at each end of the pot, there is no DC voltage across it.
Lou, I completely agree there is no voltage drop across the slope resistor. Just making a comment that there is 200VDC for those that might not understand what 'voltage load' means.
Thought so..
Here is my opinion on those P&O caps FWIW
The first ODS style amp I built (12 years ago) I used the Jensen P&O caps and found that they are a very smooth sounding cap but I found them to be a bit dark and lifeless especially on thoe top end..The amp also didn't want to sustain very well and the notes seemed to want to die off rather quickly and also had a kind of stiffness to it as well.. I eventually converted that amp over to the PS series caps and the amp regained it's sparkle as well as a more prominent mid range (more in the guitars range) ..The amp opened right up and the sustain/bloom came right back..P&0 caps are good for some things (PA applications/Tone caps for guitar) but not for guitar amps!!
This is of coarse just my opinion but I think worth mentioning since I have been down that road and didn't like it..
Good Luck with the build!!
Tony
" The psychics on my bench is the same as Dumble'"
