Hi there! I've recently looked into making a buffer/preamp for my Fender Stratocaster - all single coil. My reason for doing this was primarily to maintain a strong signal when running through a passive A/B/A+B switch, as I noticed a clarity drop-off using A+B.
I built this buffer:
and it definitely took care of the issue stated above. However, I find now that there are a couple of undesireable effects:
1) too amount of treble in the signal. Am I boosting treble here?
2) though I don't lose treble when bringing down the volume, the volume does drop off too fast.
if there are changes to the circuitry that would address these issues, please point them out to me. i'm learning as i go on all things electronics related!
Also I have not changed tone pot or volume pot values.
I suspect that the volume issue could be adjusted by changing R1 or possible even removing it. ?
And - this preamp is between the pickup and the volume knob, powered by a 9v battery, wired to a TRS input jack to "turn it off" when the cable is out.
Thanks in advance for any help!
Jeff
I built this buffer:
An externally hosted image should be here but it was not working when we last tested it.
and it definitely took care of the issue stated above. However, I find now that there are a couple of undesireable effects:
1) too amount of treble in the signal. Am I boosting treble here?
2) though I don't lose treble when bringing down the volume, the volume does drop off too fast.
if there are changes to the circuitry that would address these issues, please point them out to me. i'm learning as i go on all things electronics related!
Also I have not changed tone pot or volume pot values.
I suspect that the volume issue could be adjusted by changing R1 or possible even removing it. ?
And - this preamp is between the pickup and the volume knob, powered by a 9v battery, wired to a TRS input jack to "turn it off" when the cable is out.
Thanks in advance for any help!
Jeff
that shows up as a link? I just selected a gif of it and pasted it into the message body.
its the top schematic at this page:
AMZ - Guitar Effects & JFET Splitter
its the top schematic at this page:
AMZ - Guitar Effects & JFET Splitter
I would lose R1 and R5. I'm not sure why they're being called "pulldown resistors." Don't remove the capacitors. And at the "original article" link it states, "The values shown here will give good performance but can be tweaked to suit your taste. For example, if it is a bit too bright for your rig, reduce the values of both R2 and R3 to 1M, or even 470k to see if the lower input impedance takes some of the edge off." Hopefully these things will fix the volume control problems too.
its getting better!
I took your advice, dropped R1 and R5 entirely, and effectively brought R2 and R3 to 687k. Its much better! Not as much emphasis on the treble side for sure, a little beefier tone. I still may try something to "bleed" off a touch of high end response. Do you know - could a capacitor be used across R2 similar to a treble rolloff capacitor on a plate in a tube gain stage? What would be the harm in trying? I've got plenty of 250pf s sitting around. I may give that a whirl at my next string change.
I took your advice, dropped R1 and R5 entirely, and effectively brought R2 and R3 to 687k. Its much better! Not as much emphasis on the treble side for sure, a little beefier tone. I still may try something to "bleed" off a touch of high end response. Do you know - could a capacitor be used across R2 similar to a treble rolloff capacitor on a plate in a tube gain stage? What would be the harm in trying? I've got plenty of 250pf s sitting around. I may give that a whirl at my next string change.
Basically, magnetic pickups are inductors, so reducing the impedance they're feeding into reduces treble response. When you put in a high impedance buffer, you're getting the actual output of the coil; accurate, but you consider too rich in high frequencies. Putting a capacitor across makes a resonant circuit; which might sound quite interesting, but is only one sound. Most tone controls leave a bit of resistance, to damp it down.
When volume and tone are at maximum you can get some pretty weird effects from long jack cables, but the buffer will eliminate these.
When volume and tone are at maximum you can get some pretty weird effects from long jack cables, but the buffer will eliminate these.
I'm done tweaking for now!
well, thanks for the replies and the interest!
believe it or not, I decided to go to a set of D'Addario Chromes for awhile. I'd used them years ago for recording (no string noise, still relatively bright) and wanted to revisit the sound. I've also been kinda jazzing it up around the house. Anyway, going from round wounds to Chromes, which are flats, significantly removed the icepicks from the sound. I'm going to let these strings ride for awhile, but when I'm ready to change them I'll reopen the cavity and try some more tweeking. Maybe I'll also move the circuit to the vibrato spring cover plate - right now its velcro'd to the back of the pickguard!
Thanks again!
well, thanks for the replies and the interest!
believe it or not, I decided to go to a set of D'Addario Chromes for awhile. I'd used them years ago for recording (no string noise, still relatively bright) and wanted to revisit the sound. I've also been kinda jazzing it up around the house. Anyway, going from round wounds to Chromes, which are flats, significantly removed the icepicks from the sound. I'm going to let these strings ride for awhile, but when I'm ready to change them I'll reopen the cavity and try some more tweeking. Maybe I'll also move the circuit to the vibrato spring cover plate - right now its velcro'd to the back of the pickguard!
Thanks again!
Thanks Keriwena,
I'd removed R1 & R5 altogether, and dropped R2 & R3 to around 680k. I didn't seem to lose range, but the high response is definitely tamed - still "cleaner" than no buffer at all, though.
Is it detrimental to leave it set up like this, from the standpoint of pick-up performance? Preamp performance?
I'd removed R1 & R5 altogether, and dropped R2 & R3 to around 680k. I didn't seem to lose range, but the high response is definitely tamed - still "cleaner" than no buffer at all, though.
Is it detrimental to leave it set up like this, from the standpoint of pick-up performance? Preamp performance?
Well, the article below the one you used states, "[FONT=verdana,arial,helvetica]If you want to change the input impedance, the values of R2 and R3 can be altered to suit your taste. If the signal seems too crisp and bright, lower the values of those two resistors to 470k each. Always keep R2 equal to R3. [/FONT]", so I guess you're not hurting the preamp. Still, if it's causing you to use flatwounds I'd say it's definitely on the bright side.
Normally, you have a cable between your guitar and the amp and the cable's capacitance rolls off quite a few highs. When Santana started using a wireless, PRS installed a switch with a small cap to ground in his guitar because Carlos complained about the extra highs that occurred when he used a 1' cable to a belt back on his strap as opposed to a 20' cable to a pedal board. With an onboard preamp, you have the same situation as the preamp buffers your cable and prevents the typical treble loss.
Granted, there's some personal taste involved in terms of 'pickup performance', but if you have to change anything on your guitar, including the knob settings, then I'd tweak the input of the preamp so the guitar behaves "normally". An overly sharp (high Q) peak from the pickups produces a "brittle" or "ice pick" tone that's hard to correct as other tweaks have a broader effect and so while you can roll off the treble, you'll still have a spike in the roll-off. Best to fix it at the source.
Normally, you have a cable between your guitar and the amp and the cable's capacitance rolls off quite a few highs. When Santana started using a wireless, PRS installed a switch with a small cap to ground in his guitar because Carlos complained about the extra highs that occurred when he used a 1' cable to a belt back on his strap as opposed to a 20' cable to a pedal board. With an onboard preamp, you have the same situation as the preamp buffers your cable and prevents the typical treble loss.
Granted, there's some personal taste involved in terms of 'pickup performance', but if you have to change anything on your guitar, including the knob settings, then I'd tweak the input of the preamp so the guitar behaves "normally". An overly sharp (high Q) peak from the pickups produces a "brittle" or "ice pick" tone that's hard to correct as other tweaks have a broader effect and so while you can roll off the treble, you'll still have a spike in the roll-off. Best to fix it at the source.
Last edited:
Thanks Keriwena!
Believe it or not, the flatwounds were actually something I wanted to revisit anyway. That desire, plus the need for new strings, just happened to coincide with the buffer impulse. I really only mention them because using them currently does alter the tonal output and make comparing pre- and post- modification performance of the buffer skewed. It wasn't the best time to change string types for an A/B comparison.
I have thought to get another pickguard to play around with, put the buffer in it and add a switch or two to play with the tone of the guitar in general. This strat is an american model from around 1980, and though not necessarily "collectible", it is still "protectable" from modifications that might reduce its value. There are several strat mods that I've read of that would be fun to try.
Thanks for the ideas. I will tweak more with this guitar in the future and post any further modifications from the current circuit. For now, I am enjoying the tones available to me with the current set-up.
Believe it or not, the flatwounds were actually something I wanted to revisit anyway. That desire, plus the need for new strings, just happened to coincide with the buffer impulse. I really only mention them because using them currently does alter the tonal output and make comparing pre- and post- modification performance of the buffer skewed. It wasn't the best time to change string types for an A/B comparison.
I have thought to get another pickguard to play around with, put the buffer in it and add a switch or two to play with the tone of the guitar in general. This strat is an american model from around 1980, and though not necessarily "collectible", it is still "protectable" from modifications that might reduce its value. There are several strat mods that I've read of that would be fun to try.
Thanks for the ideas. I will tweak more with this guitar in the future and post any further modifications from the current circuit. For now, I am enjoying the tones available to me with the current set-up.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.