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Post by roadtonever on Aug 6, 2011 5:07:12 GMT -5
Found this in a wiring blog: I gather Jerry Garcia used a similar setup and his tone was certainly awesome. Has anyone had experience with setup such as this? What could be expected from it?
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Post by JohnH on Aug 6, 2011 7:22:26 GMT -5
Its very similar to how I have wired built in buffers. You can expect a clear extended high end, and the ability to drive extended cable lengths or plug directly into a mixer line-in. I like to do them with a JFET however.
Clicking on the picture, follows back to the blog. It seems this fellow is setting out to re-present alot of basic wiring. There's not much new there, but he does nice pictures.
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Post by newey on Aug 6, 2011 7:34:58 GMT -5
No personal experience with this type of set-up, but the buffer is used for the same reason a buffer is usually used- to allow for long cable runs onstage without the dreaded "tone suck". Putting the tone control before the buffer allows for the standard parallel interaction between the pickups and the tone control; the volume goes afterwards so the output from the buffer can be controlled. Usually, this is done with a unity-gain buffer, not a booster. Garcia's set-up did employ a passive tone control, a unity-gain buffer, and an active volume control, but was a good deal nutzier. In his "Tiger" guitar (I'm not sure how "Wolf" was wired), the buffer first goes to a TRS jack which serves as an onboard effects loop. The effects signal goes out to the pedals and back into the guitar (via a 3-conductor cable), and then to the active volume control, and from there to the output jack. This set-up was designed so that the effects output could be controlled by the guitar's volume pot. I posted a copy of Tiger's schematic a while back for discussion, as I thought it was an interesting idea, but rather than discuss the wiring, some of our resident Dead-Haters used it as an excuse to pile on, so the thread died there: Tiger Wiring( Note: The statement that the tone control was also after the effects loop in Tiger, made in the linked article and repeated by me, is in error, as a review of the schematic shows.) EDIT: AAACK! Ninja'd by JohnH!
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Post by roadtonever on Aug 6, 2011 10:07:29 GMT -5
Its very similar to how I have wired built in buffers. You can expect a clear extended high end, and the ability to drive extended cable lengths or plug directly into a mixer line-in. I like to do them with a JFET however. Clicking on the picture, follows back to the blog. It seems this fellow is setting out to re-present alot of basic wiring. There's not much new there, but he does nice pictures. I've actually ordered the parts required for your tiny buffer module which I plan to add at the output jack on my axes. Would there be a significant difference in tone with the placement of the buffer as above(and the 25k pot)? Would it be similar to the flatter extended responce you get from turning down the volume quite a bit in a normal setup? If so could the passive tone control bring back the controls at "10" sound? Sorry about all the questions as you can see I'm a bit intrigued. It's a nice blog indeed! No personal experience with this type of set-up, but the buffer is used for the same reason a buffer is usually used- to allow for long cable runs onstage without the dreaded "tone suck". Putting the tone control before the buffer allows for the standard parallel interaction between the pickups and the tone control; the volume goes afterwards so the output from the buffer can be controlled. Usually, this is done with a unity-gain buffer, not a booster. Garcia's set-up did employ a passive tone control, a unity-gain buffer, and an active volume control, but was a good deal nutzier. In his "Tiger" guitar (I'm not sure how "Wolf" was wired), the buffer first goes to a TRS jack which serves as an onboard effects loop. The effects signal goes out to the pedals and back into the guitar (via a 3-conductor cable), and then to the active volume control, and from there to the output jack. This set-up was designed so that the effects output could be controlled by the guitar's volume pot. I posted a copy of Tiger's schematic a while back for discussion, as I thought it was an interesting idea, but rather than discuss the wiring, some of our resident Dead-Haters used it as an excuse to pile on, so the thread died there: Tiger Wiring( Note: The statement that the tone control was also after the effects loop in Tiger, made in the linked article and repeated by me, is in error, as a review of the schematic shows.) EDIT: AAACK! Ninja'd by JohnH! The concepts in the Tiger scheme like the buffered onboard effects loop seem too awesome. I'm almost ashamed I put it in context to the diagram above...
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Post by ashcatlt on Aug 6, 2011 12:28:19 GMT -5
If the V pot comes before the buffer/booster you will have treble loss as the V is turned down, though maybe not quite so much as if the first active stage was at the end of a capacitive cable. The T control cant really help that.
With the V after the active stage it will just get quieter as you turn down, retaining essentially the exact same frequency response. Of course, amp compression/overdrive and good old Fletcher/Munson might mean it sounds like the response changes.
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Post by roadtonever on Aug 6, 2011 14:17:41 GMT -5
If the V pot comes before the buffer/booster you will have treble loss as the V is turned down, though maybe not quite so much as if the first active stage was at the end of a capacitive cable. The T control cant really help that. With the V after the active stage it will just get quieter as you turn down, retaining essentially the exact same frequency response. Of course, amp compression/overdrive and good old Fletcher/Munson might mean it sounds like the response changes. Thanks for the explanation. Sounds like the active stage after the volume makes an ideal treble-bleed alternative. Maybe it's not for me then as I usually have the volume control at ten and sometimes turn down the volume to get a specific tone.
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Post by roadtonever on Aug 6, 2011 15:42:25 GMT -5
OT: I wonder if this is like the "anti-treble bleed" for jazz tones I dreamt up a while back. Gonna have to try it out
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Post by JohnH on Aug 6, 2011 16:01:13 GMT -5
If the V pot comes before the buffer/booster you will have treble loss as the V is turned down, though maybe not quite so much as if the first active stage was at the end of a capacitive cable. i would differ on that point. I think both buffer positions avoid treble loss due to the cable. On my builds, I use the usual guitar volume pot (eg 500k) before the buffer, with no treble bleed, and tone is constant all through the volume range. With a high impedance buffer, and no cable capacitance in play, the pickups are feeding into a contant load at all volume positions. Putting the buffer after the vol pot also results in the lowest output impedance, with no pot after the buffer. Thats why in the blog diagram, the volume pot is a low value at 25k. No fundamental problem there, but the buffer then has to drive current through that pot. With no pot after the buffer, the JFEt circuit can be configured to run at a truely minute amount of current (depends on the output resistor), lower than any Opamp, and still give the required performance. Theres a couple of versions of the buffer on the schematics section post. They all work, but which parts have you got? The main choices depend on which JFET you have, and what type of input you want to drive. The most versatile one is the last buffer circuit: which will drive a mixer line-in, and draw about 0.3mA (maybe 1000 hours from an alkaline battery). If you dont need to do that and are happy to plug into normal guitar amp/pedal inputs, you can increase R4, and current drops in proportion - I reckon 33, 39 or 47k is a good value, but you can go up to 100k. John
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Post by newey on Aug 6, 2011 16:47:04 GMT -5
Moving to a 1M pot (I have done this on my white/gold Strat) won't preserve more treble as you turn the control down, as a treble bleed does. The treble bleed works by diverting a part of the frequency spectrum of the signal past the pot, so that that portion of the frequency spectrum is unaffected by the pot.
With a 1M pot, the entire signal is affected as you turn the pot down.
A 1M pot will make the tone brighter when at "10", and it will have less of a "range of adjustment" than a lower-value pot; most of the action will happen over a narrower range of travel.
My white Strat is so bright with 1M pots (both pots are 1M) that I keep the tone control perpetually at about "7". If I ever open it up in the future, I will swap out at least one of the pots for a lower value. I like a bright tone, but this guitar is a bit much. And in addition to turning down the tone control on the guitar, I also end up re-EQing at the amp when I use it, to dial the tone back a bit more than I can do on the guitar without it getting too muddy.
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Post by roadtonever on Aug 7, 2011 0:32:50 GMT -5
The most versatile one is the last buffer circuit: That's the one! I'm gonna use your stripboard layout and swap 100k for 22k and 330nf for 2200nf. Moving to a 1M pot (I have done this on my white/gold Strat) won't preserve more treble as you turn the control down, as a treble bleed does. I understand that. I was thinking about a control that aims to do the opposite of a treble bleed, sounding like a volume control tuned down without loosing volume.
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Post by roadtonever on Aug 7, 2011 15:37:24 GMT -5
JohnH, regarding your buffer module; If I'm reading the datasheets correctly it seems it would be hard to fit the I/O caps neatly in one row. Would it be acceptable to pre-fit both caps before soldering the large cap and the smaller cap thereafter? Also do you have any recommendation for brand/series of caps for this application? Lastly you've mentioned in an other thread a bass cut starts somewhere around 50Hz. I was too curious about the extent of it so I broke down and miraculously managed to get LTspice up and running, thanks to some good tutorials really. But I'm unsure about the results. Either I made a mistake or the bass cut is negligible even for bass. Also the current draw models some 30% lower than expected. edit: grammar
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Post by sumgai on Aug 8, 2011 2:31:27 GMT -5
rtn,
+1 for the humor value of that last image!
sumgai
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Post by JohnH on Aug 8, 2011 5:15:39 GMT -5
sumgai - even himself has to have some down time, and theres nothing like a little active electronics for relaxation after a hard day rockin' the free world.
'Road to never' the output circuit, with the 2200nF cap (thats better known as a 2.2uF electrolytic), could be made to stand vertically in that space, most neatly if it is a type that has both wires at one end. It will be about the size of the 10uF, and the + end should go to the JFET. Nothing special about it, any brand will work.
In your analysis (well done for doing it), the bass response will depend on the input resistance of whatever device comes after it, so for modelling, you could represent that with another resistor in parallel with the 3.3M. Try a 20k, to respresent a mixer line-in. BTW, the 3.3M doesnt do much other than to keep the output cap grounded, avoiding a crackle or two when you plug it.
The circuit should have very little bass roll off at guitar frequencies, even if loaded by a line-in. If its only for a guitar amp input, you could revert to the 330nF cap if you wish, but I think its good to have the option of plugging into a variety of devices.
John
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Post by roadtonever on Aug 8, 2011 7:21:14 GMT -5
2.2uf electrolytic? Aren't those "bad" for the signal path? I was thinking poly film. I added a 10k resistor in parallel w the 3.3M to simulate an unbalanced line input and I got a 0.15dB drop at 40Hz, does that seem right?
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Post by JohnH on Aug 8, 2011 15:35:25 GMT -5
The electrolytic seems to work fine, but you could use a smaller poly one if you prefer. The 0.15db drop that you calculated is the right result, so, assuming this is to go in a guitar, why not test what the cap would be for say, 0.5 or 1db drop at say 50hz?
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Post by roadtonever on Aug 8, 2011 18:12:25 GMT -5
Using a target of max 0.5dB reduction at the fundamental of the lowest note(40Hz and 80Hz), connecting to a 10k input(unbalanced line-in). For bass one could get away with a 22nF output cap. For guitar it's 5.6nF. What an interesting and fun exercise EDIT: I extended the "how low can you go" test to the input cap and was more conscious of the E12 series this time. For bass I could get away with 1.2uf and 22nF, for guitar it's 0.56uf and 15nF.
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Post by JohnH on Aug 8, 2011 20:36:56 GMT -5
something wrong with those output cap calcs. i agreed with your earlier result for 2.2uF, but for -0.5db at 40 and 80 hz, by the same hand calc method, I get 1.2uF and 560nF, to the nearest standard values, into a 10k load.
Dont foget about drop tuning too.
John
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Post by roadtonever on Aug 8, 2011 21:32:55 GMT -5
Thanks for your values, they will help me troubleshoot my model.
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Post by roadtonever on Aug 10, 2011 5:17:37 GMT -5
Still can't manage to get your values to correspond with my model. Could you be so kind kind as to recommend values for guitar and bass with my targets? I never down-tune or trem.
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Post by roadtonever on Aug 10, 2011 7:47:04 GMT -5
In the mean time I drew this: It's the "impedance tuner mod" mentioned in reply #6 replacing the volume control. I reckon it could be useful for someone that doesn't use the volume control as such.
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Post by JohnH on Aug 10, 2011 15:36:11 GMT -5
Still can't manage to get your values to correspond with my model. Could you be so kind kind as to recommend values for guitar and bass with my targets? I never down-tune or trem. I use the 2.2uF electro and it works fine for me. but ill try running a model to check some different values - may be a couple of days. John
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Post by JohnH on Aug 11, 2011 15:35:38 GMT -5
I did run a model - and got the same results as in my hand calculation in post 16 above. So if you want the option of using 10k line-in to plug into, use at least 560nF for guitar and 1.2uF for bass to get less than 0.5db roll off at 80 and 40hz. If you dont want to have the line-in option, then about 390nF is fine for either. Ill post graphs tomorrow.
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Post by JohnH on Aug 12, 2011 16:54:15 GMT -5
Here's some output from 5Spice: Circuit: Graphs are shown for the circuit feeding into three values of output load (R5), and with a range of output caps (C1) Output frequency response into a 10k load (such as an unbalanced line-in,), with output cap varied from 200nF up to 1200nF = 1.2uF: 100k load: 500k load (such as a guitar amp or stompbox): The vertical cursor lines are set to 40hz, for bass. With the low impedance load (1st graph), you can see how one might want the largest cap. At higher impedance loads, the cap can be much less if you wish, but I dont see any advantage in going smaller than 390 or 330nF. Another interesting thing to see from these graphs is that the overall output at higher frequencies is about -0.37db with the high impedance load. This small loss is due to the JFET and is pretty much negligible. At 10k load, the output is about -1.2db, still not a big deal, but it shows how putting a 10k load on this circuit drops the output by about 0.8db. From that, we can estimate the output impedance of the circuit: 10^ (-0.8/20) = 0.91 This is the ratio by which the output voltage drops due to a 10k load, and suggests that the effective output impedance of this circuit is about 1k = not bad at all. BTW - my calcs are with a 2N5457 JFET, since I dont have a 201 in the model library. But this circuit is not very sensitive to JFET type. John
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Post by roadtonever on Aug 14, 2011 19:45:45 GMT -5
I've had some computer issues in the last days so I haven't had the chance to reply until now. First of all thanks for the graphs, JohnH! I'll use your values as I can't rule out user error or JFET model differences with any confidence While sorting out my computer issues I updated my soundcard driver and saw a new button in the mixer software that converted a stereo line input into a balanced mono input. I'm compelled to think about using your module in a balanced config because of this! Google tells me in most cases the third pin could be left hanging in an unbalanced situation which means I'd be covered no matter what I plug into. Would love to hear your thoughs about this, JohnH.
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Post by JohnH on Aug 14, 2011 20:49:25 GMT -5
Balanced is nice, and its the best way to connect pro audio systems together, but I’d say it’s probably not particularly helpful from a guitar unless you want to reinvent guitar wiring and do balanced all the way from the pickups. Guitar circuits and their switching and grounding are based on being unbalanced, with a signal ground and a hot output. It would be quite feasible to design a balanced-output guitar, and it might be a good thing, but to do it properly it would need special pickup switching and a two-core output lead, like with a microphone, and different electronics if it was active.
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Post by roadtonever on Aug 14, 2011 21:26:26 GMT -5
I see. I was thinking about reducing mains hum and maybe RF through a faux-balanced config. But I'm dragging my feet... EDIT: I realize that was kind of a dumb reply on my part considering you're a humbucker user . I placed an order for the remaining parts just a moment ago. Can't wait!
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