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Post by ozboomer on Sept 8, 2008 2:03:21 GMT -5
[...about pickups...] Well, I think your idea of making the 'one change at a time' would be instructive. It's all about teaching my ears about what they're hearing, I think... Still, I can't help myself re: aesthetics I've been researching some pickup covers/knobs, etc... and it's kinda interesting... Very few of the on-line sellers seem to be aware of the different sizes/pitches in the pickup covers.. and they (metaphorically) look at me like I'm crazy when I say the poles on the pickups vary in their spacing.. but looking at the pickups on 3 different guitars give me 3 different dimensions for each of the pickups (between the outer edges of the outer poles); we're talking anywhere between 50mm and 57mm across all the pickups across all the guitars. So, I was thinking about getting some cheap-ish pickups to help 'guarantee' the covers match the pickups themselves... ...but maybe I'll just dig out the Dremel and 'make' things fit; it IS a project guitar after all.. and I guess it should have some sort of 'modified' look, eh? Anyway, I'll let the design posting here stand for a day or two.. make a 'final' diagram... and meanwhile, I'll see if I can work out how to do the real wiring(!).
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Post by lpf3 on Sept 8, 2008 19:05:56 GMT -5
oz - I think this is a good idea too , I recently did a few things all at once to my Tele - made a dramatic difference but I'm not entirely sure what did what As far as pup covers , here's a look I kinda like With these ya don't have to worry about polepiece spacing & they don't seem to change the tone , output , ( yet ) Both Allparts & HASsound stock 'em , they're on our links page . Hope this helps -lpf3
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Post by ozboomer on Sept 8, 2008 22:20:08 GMT -5
As I let the comments/final thoughts on the design trickle through, I think I'll let the cats loose amongst the pigeons... Also, given a choice, log pots are better for tone, while for volume pots, log or lin is a personal choice, I like linear pots, unless Im adding treble bleed caps and resistors (a good idea IMO - as suggested for the blender) in which case log. Your blender is best as lin pot. Ok... As I understand it, the audio response of the ear is a logarithmic function, hence you'd use audio pots for the volume control... so we sort of agree on that... ...but why would you use audio taper (log) pots on tone? The tone controls are merely shifting a cutoff frequency in a passive low pass filter (of sorts), so why wouldn't you use a linear pot? ...or is it again something to do with how the cutoff frequency sweeps across the spectrum; from a given starting point, is it really a log relationship to move the cutoff frequency "down" an equal amount to how far it moves "up"? (see en.wikipedia.org/wiki/Frequency_response. for example) This is always a favourite argument and I don't even know how to search for it on this site(!), so I thought I'd at least float it here and maybe we could make a 'sticky' out of this section of the thread and drop it in the reference section sometime...
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Post by ozboomer on Sept 8, 2008 22:35:46 GMT -5
As far as pup covers , here's a look I kinda like [...] With these ya don't have to worry about polepiece spacing Hmm... Well, it's a treatment I'd not even considered... I'll put it into the mix... Thanks. How do those covers go with staggered pole pieces though... or they're of such a depth that it's not an issue? It seems the pole spacing is not really standardized so I'm half-guessing ('coz I haven't measured them) the depth of the various pickups, with or without staggered pole pieces, would also not be standardized... so I'd still have to check with the shop I'm buying 'em from about measuring the depth of the covers without holes... Pffft!
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Post by lpf3 on Sept 8, 2008 23:18:07 GMT -5
oz - The pups in the pic have staggered polepieces & the covers don't cover all the way to the bottom , the gap is about the same as the amount that the highest polepiece sticks out ( obviously ) . To protect the coils I wrapped one layer of electrical tape around them & no problem . Figured that was no different than open humbuckers anyway . I've since put the guitar together , played it , taken it apart , etc . etc . with seemingly no problem ,they're clean , protected , & covered & I think they're fine - for me anyway . -lpf3 EDIT : oz , I should add that a while back I was peeling the tape back off a coil , not carefully enough , & much of the winding came with it . That wasn't good . Just wanted to share that ........
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Post by JohnH on Sept 8, 2008 23:28:57 GMT -5
On tone pots, as you turn down the tone with say a 500k pot, not so much happens for the first 400k or so, just a gradual slight diminishing of the high treble. Below that, there’s audibly greater change with the most tone-cut drama in the last 20 or 30k. So with a log pot, the change of pot resistance with the greatest effect occupies a reasonable amount of the pot turn, while with a linear pot, most of it is between 0 and 2. Of course, it works technically either way. One of mine has a linear tone pot, because it is with a push/pull switch and that’s what I had. Given a choice, I think log is more controllable.
With volume pots, that argument about the logarithmic response of human hearing is often quoted as a reason why the pots should be log. I think that’s all fine for a volume control on a radio. But I don’t buy it on a guitar, I think it depends how you want to use the volume pot. If you want to make a small reduction of a few db, say to change from a clean or mildly overdriven lead down to a clean rhythm, then a linear pot gives more control at the top range. They are also better if you have two volume controls and use them for mixing pickup sounds, because you only need a small reduction in one pup to make it audibly fade away, relative to the other. But if you use it to clean up a highly overdriven signal by making a large volume reduction then a log pot is better. Also, due to hte way the treble bleed cap/resistor changes the pot taper, I find a log pot is better, in fact ideal, in those cases.
Note a log pot is actually an approximation using two linear ranges. I think they usually go from 0 to about 10% in the first half turn, then 10% to 100% in the second half. So if you use a log pot only from 5 to 10, you are actually just using just a linear section of track.
John
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Post by ozboomer on Sept 9, 2008 0:33:12 GMT -5
On tone pots, as you turn down the tone with say a 500k pot, not so much happens for the first 400k or so... Okie.. So, returning to the diagram for a minute, given what you say above, is it a good idea to have the 500k pots for the volume/tone controls? ...or is this one of the things to 'experiment' with? Is it a subtlety thing, that a smaller value will give greater/faster changes? I just guessed at the 500k pots in my original design as that's what I'd seen used elsewhere...?!? Still, from what ChrisK suggests about loading, it would seem the 250k blender pot is probably Ok, given the configuration of the pot that we're using here. Note a log pot is actually an approximation using two linear ranges. I think they usually go from 0 to about 10% in the first half turn, then 10% to 100% in the second half. So if you use a log pot only from 5 to 10, you are actually just using just a linear section of track. Yup, I've seen some diagrams that describe that... but Fanx! again for your help John
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Post by ozboomer on Sept 9, 2008 0:45:03 GMT -5
oz , I should add that a while back I was peeling the tape back off a coil , not carefully enough , & much of the winding came with it . That wasn't good . Just wanted to share that ........ Yessss.... This is why I'm kindof nervous about fiddling about (too much) with pickups at this stage; but I thought I couldn't get into too much trouble by just changing the covers on 'em... until I found out about the different sizes, etc(!)
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Post by JohnH on Sept 9, 2008 1:39:39 GMT -5
500k is the best value for your tone pot, theres a small but worthwhile extra bit of brightness available compared to a 250k pot. This is particularly true with series wiring, due to the greater inductance of two pickups in series (this upper range of the tone pot operation is more to do with the pot resistance interacting with the pup inductance and not much to do with the actual tone cap). As the tone pot reduces in resistance, it adds more load to the pickups, reducing treble by acting as an LR filter. The cap starts to get more significant as you approach the low end of the tone pot. Eventually, at 0 on the tone pot, you have an L R C filter (R at that stage is the resistance of the pickups), with a new resonant peak somewher in the midrange, and a sharp fall at higher frequencies.
The blender pot is also across the pickups, and woudl be loading them except for the cutting of the track. Instead, it loads neither in the mid position, or just one pup at a time when you turn it away from centre, reducing the upper harmonics of the dimished pup (which contain most of the character of he sound)ahead of the lower harmonics. It' s part of the way it works and I reckon you'll like it!.
John
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Post by ozboomer on Sept 9, 2008 6:27:27 GMT -5
500k is the best value for your tone pot, theres a small but worthwhile extra bit of brightness available compared to a 250k pot.... Another helpful explanation, thanks JohnH... Hmm... This project started out as purely a means for me to get my hands dirty with playing about in the guts of one of my guitars... and it's become a good refresher in some basic electronics. Now all I have to do is to recognize the relationships between what I end-up building and what the (new) components/wiring in the guitar will be doing(!).. I'll get to the revised 'final' circuit in the next day or so ( hmm... should it be v5 or should it be v1.0.0 for the 'first final public release'? ;D ) I know it'll take me a few days to get the actual wiring diagram (not the circuit) drawn (and somehow understood)... but I'll get there... and I have to work out where I'm going to buy the guitar knobs, etc... and the electronics... Decisions, decisions... More later.. John
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Post by ozboomer on Sept 11, 2008 6:08:51 GMT -5
Here we go with a couple of diagrams... The 'final' circuit diagram of the design... and (after I don't know how many hours!), a wiring diagram (apologies, BTW, for the large image): I've tried to make the wiring diagram look something like how the rear of the pickguard would look... Note that the 'J' points are simply junctions that help me understand what the heck is going on I was thinking, once I've made the wired connections to/from the pots, I thought I'd be able to rotate them a little if they somehow physically interfered with each other. Although, I think it's all Ok, I'd still like to get some more eyes to check over my 'translation' of the circuit... and I still have a question: In the middle of the wiring diagram, I've placed an 'ultimate' ground. Where would I make that connection? I have recollections of a wire between the bridge, the tremolo claw, the output jack... or something...? Anyway, I hope the diagrams are understandable... and I'd appreciate any validation thoughts... Thanks! John
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Post by ashcatlt on Sept 11, 2008 14:43:01 GMT -5
Ground is found through the amp, so you're "ultimate" ground is already represented in your diagram by the jack sleeve. That big green blob is redundant. You will probably want to find somewhere to connect the bridge/string ground wire (called such because it connects the bridge and strings to ground at the amp), and that lug of the switch is about as good a place as any other.
Are you going to shield this thing while you've got it open?
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Post by ozboomer on Sept 11, 2008 18:40:01 GMT -5
Ground is found through the amp, so you're "ultimate" ground is already represented in your diagram by the jack sleeve. [...] and that lug of the switch is about as good a place as any other. Okie.... So, if I scrounge around and find a wire that seems to go through the body and connects to the tremolo spring claw, I can connect that to where the 'blob' is now and everything will be grounded Ok? It's just that in most of the diagrams and photos I've seen, they never show the actual connection of a ground wire in the circuit to the bridge/strings... and I have no doubt that would be a trap for those of us who have never done any significant guitar re-wiring(!) Are you going to shield this thing while you've got it open? I doubt it. This current project is already pretty demanding for me... and although I'd like to try the QTB mod, it would take me a zillion more hours to adapt it to this non-standard wiring I'm using here... and it is, therefore, probably a project for another time (and another guitar!)
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Post by JohnH on Sept 11, 2008 20:09:09 GMT -5
Getting some decent shielding and grounding is not as hard as it looks. A wire from the bridge, or anywhere electrically connected to it, such as a trem claw, goes to any ground point on the circuit, most probably the back of a pot if you are soldering grounds to that. The purpose is to ground the strings and to ground you, which cuts out a heap of noise. All commercial guitars have this feature
Before you wire up, its well worth putting foil all over the back of the pickguard. Some guitars already have a small piece just under the controls.
You can use kitchen foil (as I have), but copper foil is better, being more durable. Just cover the front of the pg with cling film to protect it, spray contact glue on the back and smooth down a layer of foil all over. Then trim carefully around the edge – its an easy and neat job. If you do nothing else, this will contact with the pot cases, at least one of which you will ground and so give you shielding from the front of the guitar. Similarly, you can line the interior with foil, and here the advantages of copper are greater because you can solder to it to connect up and its less likely to tear. I did one reasonably successfully with aluminium however. Fold it up a bit over the edges so that it clamps done and gets grounded when the pg gets screwed down. This shielding to the cavity, you can add later, but its better to at least do the back of the pg now, so that you don’t later have to remove the wiring from the pg.
The QTB mod also has other features such a safety cap, and talks about star grounding. These are nice ideas, but not really essential.
John
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Post by ozboomer on Sept 11, 2008 21:15:43 GMT -5
Getting some decent shielding and grounding is not as hard as it looks. ... Hmm... Well, it certainly wouldn't be too much of a drama to do the pickguard, I guess... and providing I was able to guarantee the pots and switches made good contact with the pickguard shielding, I expect I could remove the ground wires in the circuit joining the volume and tone pots, as well as off the DPDT switch as the shielding would be making those contacts.. or is that too unreliable and maybe I should leave those ground wires in...? Will they form ground loops...? ...or maybe their effect is small, given the low currents here...?
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Post by JohnH on Sept 11, 2008 21:39:23 GMT -5
You should use wires for all the signal-carrying grounds, ie between the pot and switch lugs and to the jack - ie so the thing forms a functional circuit without the shielding. All the pot and switch cases will contact the foil, but they are not on the signal path. Ideally, you then have just one place where the whole shielding system is grounded. You can do that with one wire soldered to the back of a pot, and connected to a grounded part of the circuit. The back of this pot is also a good place to connect the bridge wire and any grounded wires or braids from the pickups.
To solder to the back of pots, you need a powerful iron of 40W or more. I prefer not to and I just solder a wire to a washer and slip this onto a pot shaft, then the other end of the wire gets grounded. I use a bare wire for so I can solder other things needing grounding to it.
People get worried about ground loops in a guitar - ie, having more than one route to ground. IMO, this is not a real problem in a guitar circuit, but the above system avoids this anyway.
John
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Post by ozboomer on Sept 13, 2008 17:42:17 GMT -5
I've been researching where/how to buy the components, etc for the project and I've come up with a few questions/thoughts on the exercise: - The Squier Affinity Strat that is my 'main' guitar was modified at some stage and the tone capacitor was changed. What came out was a 0.033uF 'greencap'. Now, it sounded Ok, just not bright enough, hence the change to a 0.022uF, which currently sounds Ok to me. After scratching my way through the 'Capacitors for Guitar' topic a little, I can see there's not a real big deal about using 'greencaps' rather than the 'orange drop' caps... but what should I do about the voltage rating? Ceramic discs run at maybe 50V and I can get 100V greencaps (what I was going to use) -- Other than some protection from dodgy wiring/amps, etc is there any specific requirement of the voltage rating of the caps? ...and really, what are some of the on-line retailers ON about with selling ceramics/greencaps for $2 when I can get them at a local electronics place for $0.20!?!? - Does anyone have any idea about the importance/relevance of the 'slot spacing' on a split-shaft pot? I just took a knob off one of the Squiers here and the pot had, what I might call 'fairly coarse' spacing of the slots around the shaft. Conversely, the inside of the knob had many more, finer-spaced slots inside... and I have no idea about whether the shaft and/or knob inside are metric or otherwise. What difference would it make anyway, as the knobs are already EXTREMELY difficult to remove?? - Regarding the blender pot we've described earlier in this topic... I assume if I buy CTS pots or similar (they are only a little more expensive than normal pots from the local electronics shop), they'll be Ok to take apart and modify the carbon track inside them... but would I do better to look for a 'centre detent' style of pot that (sounds like) it already has the track removed ( maybe see www.guitarpartsdepot.com/250K-250K_Pot_Audio_Taper_Center_Click.html )... What do you think? - DUMB question: What are some other names for "solder lugs"? I can't find these things in the catalogs of the local electronics places...? Thanks, folks.
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Post by JohnH on Sept 13, 2008 18:20:08 GMT -5
On caps, the value of the tone cap makes almost no difference with tone at 10, it only makes a difference with tone set low, but 0.022uF is fine with your design. Voltage rating is irrelevant for these, any type of cap is fine and 20 cents is a better price than $2. Some people say that ceramic caps sound different to others, or that other particular types sound different. The concessus here is that that is mostly or entirely bunkum. I use the green ones or the yellow ones from Dick Smith or Jaycar.
You raise a good point about pot shafts and knobs. There seems to be variations in the pitch of the splines on slotted shafts, and also of course you can get solid shafts. If you want to use the same knobs, that will take some research. I’ve sometimes just gone to set screwed knobs of a different style, which I can make work with various pot shafts.
The blender pot really has to be linear, not audio. 250k is best, but 100k to 300k is OK. 500k is too high. So it could also be 300k linear, which is a value used on some Les Pauls for volume controls. It also best as a 24mm diameter, and CTS is great, but also Alpha (more common and cheaper) or anything else of that size, where you can bend up the casing lugs to get at the inards is fine too. A centre detent would be ideal – I’ve been looking for a source of linear 24mm detented pots for a couple of years, and I can’t find them (anywhere). Dick Smith used to stock a 24mm dual-gang detented linear 100k pot. I bought all of those I could find, (sorry, I’ve used them all) and in fact the back section of these can be modified to make the blender. 100k is OK, and the detent makes it feel very nice. They now sell a 16mm one, but the detent mechanism of those gets trashed if you take it apart.
John
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Post by ChrisK on Sept 15, 2008 18:41:22 GMT -5
There are ceramic capacitors that are of good quality and those that are of bypass quality.
A Z5U ceramic capacitor usually has a tolerance of -20%/+80% and higher leakage. These are used for local supply bypassing such as +5VDC to DGND for logic circuits.
An X7R ceramic capacitor usually has a tolerance of -20%/+20% (or better with higher cost) and lower leakage. I've used these with success (brand specific in 1,000,000's) for years on data acquisition analog inputs with frequency responses up to 100 Hz. These are fairly stable.
A COG or NPO ceramic capacitor usually has a tolerance of -20%/+80% (or better with higher cost) and lowest leakage. These have the best stability. Unfortunately these are generally available only up to 1,000 pF.
There are several important characteristics of note when selecting a capacitor. Most vendor's within this space only disclose a few; the value, the cost, maybe the voltage rating, and, of course, the "vintageousity". They DO NOT disclose the type characteristic (such as X7R).
This isn't due to their secretive business practices (well, they do sell at 10 to 50 times the price when ordered in 100's), they just plain don't have a clue.
For all audio work, I tend to use polypropylene or polycarbonate.
With a Weatherby rifle and a Zeiss scope, I'm probably not going to use the cheapest ammo available.
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Post by ozboomer on Sept 22, 2008 1:45:41 GMT -5
Grrr... Same old garbage with dealing with on-line retailers I've sent e-mail to maybe 4 or 5 places this past week and not one of them has bothered to respond; I guess one little $30-$50 order doesn't mean anything to these people... Anyway, regarding the linear 250k pot we've talked about for the blender... It seems kind of difficult to get that pot (and still have the total order price come up to something reasonable)... Heh.. it's getting to the point that to get a few parts will end-up costing half as much as the whole guitar cost(!)... Crazy. Maybe it's back to grabbing some pots locally and possibly using non-standard knobs, hmm? ..and BTW... Other than the disadvantage of not having as much room on the pot to solder wires, is there any real problem with the 16mm pots compared to the 24mm pots? Not that this will be a real issue if I decide to get the pots locally anyway... Also, I remember in earlier discussions, there wasn't really a problem if we used a 100k linear pot rather than the 250k value. With the latest design, d'you think the circuit would still work Ok with a 100k pot? 'tis just that, again, even locally, it can be a bit tricky to get that 250k linear pot... Decisions, decisions..
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Post by newey on Sept 22, 2008 5:13:42 GMT -5
Jaycar has 250K linear taper pots, but not with a splined shaft. These are solid shaft ones with the long shaft you can cut to the needed length: 250K potI usually do as JohnH does, use set-screw knobs. "Solder lugs" are also called simply "lugs" by many electronics places. What you don't want is anything described as having a "terminal lug" or anything specified as PC mounted.
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Post by ozboomer on Sept 23, 2008 1:15:09 GMT -5
Well, I have a few things in the works, now... Some locally-sourced bits.. and some bits that I'll get from one of the on-line places.. So fingers crossed Should the progress reports/photos of the project go into "The Gallery" forum as a separate topic now and we (almost) retire this one? ...and what happens about posting the design to the "Schematics" forum? (or we do that once the project works -- positive thinking!) Still coming to grips with "The Protocol" for developing/producing these guitar projects, y'see ;D ... In any event, many thanks and considerable bouquets to everyone who's been helping me out
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Post by newey on Sept 23, 2008 6:21:14 GMT -5
Oz-
If you want people to see it, it's best to start a thread in the gallery. This thread is now 4 pages long, and few folks are going to hunt up page 4 for your photos.
Your gallery post can link back to this one for reference. Same with the Schematics board. Per protocol, you have to come up with a snazzy name for your scheme for the Schematics Board, thereby luring in the next unsuspecting victim . . . .
This thread will remain here, slowly working its way down the list, until someone has another question or comment, at which point it will be resurrected.
EDIT:And, if you have the technology, sound samples to show the tonal variations can be posted in the Sound Samples board. Read the ground rules therein if so doing.
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Post by newey on Oct 1, 2008 5:48:46 GMT -5
Oz- Now that this thread has been "trifurcated" between the Schematics board, the Gallery, and here, a comment as I reread through this and viewed your final schematic. Back on page 1, you said you'd be using the stock Squier pots for the V and T. These will usually be 250K pots. However, all diagrams posted thereafter show 500K pots, and I'm sure JohnH and ChrisK were considering that value in subsequent discussions. Not a huge deal, either value will work just fine. Putting larger value pots into a Strat is a common mod for a bit of extra brightness. But you may want to consider whether the treble bleed should have a different value if, in fact, you are using 250K pots. Looking forward to your build of this baby . . .
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Post by ozboomer on Oct 1, 2008 7:33:17 GMT -5
Back on page 1, you said you'd be using the stock Squier pots for the V and T. These will usually be 250K pots. Actually, with the subsequent discussions that have gone on, I decided to replace all the pots as per the final schematic... unless I find out something strange with the new pots I have. Nonetheless, you're quite right - I plan to use 500k pots for the Volume and Tone controls... and, as there have been "supply issues", I've opted for a 100k linear pot for the blender. I also expect I might need to experiment some with the treble bleed arrangement. I wonder if JohnH's Guitar Frequency Response Calculator might be useful in guiding me to the values to use? I still don't fancy selecting some values, installing everything, re-stringing, re-setting-up... trying it.. find the values don't work then pull everything apart, change the capacitor/resistor values and re-build... all a dozen times... but I guess doing all that is part of the (sic) fun ;D
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Post by JohnH on Oct 1, 2008 15:53:28 GMT -5
On treble bleed, I keep coming back to 220k in parallel with 1nF. By the spreadsheet was made specifically to test that, so play away.
One question is, what length of cord do you use?, and how do you use the volume? ie if its not at 10, where else is it most likely to be, or at what setting would you most want the tone to be the similar as at 10? Or would you like it to get brighter and twangier as you turn down the volume (as on a Tele - which often has a 1nF and no extra resistor), or warmer with les highs (no treble bleed - every other guitar)
These passive treble bleeds are a best compromise, but cant keep the tone absoluteley constant. IMO they are much better than not having one.
On my guitars, I have 2 with treble bleed, both 1nF and 220k, and two with active JFET buffers which do keep the tone constant and are one of my favorite gadgets.
John
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Post by ozboomer on Oct 2, 2008 6:23:57 GMT -5
On treble bleed, I keep coming back to 220k in parallel with 1nF. By the spreadsheet was made specifically to test that, so play away. Okie.. I only ever read about 0.001uF in parallel with 150k, although I know Chris Kinman likes them in series. One question is, what length of cord do you use?, and how do you use the volume? ie if its not at 10, where else is it most likely to be, or at what setting would you most want the tone to be the similar as at 10?... My cords are only fairly short; they'd never get beyond 5m or so, I think.... Hmm...Thinking about the volume/tone... I would probably only ever have the volume on 6-7 if not 10 or 0; it's a fairly simple requirement for me - as long as the highs don't drop out in that top half of the turn range, I'll be happy. active JFET buffers which do keep the tone constant and are one of my favorite gadgets. If we're talking about something like Don Tillman's design, I was already thinking about something like that for another project - the low output level on all my guitars make me crazy when I'm fiddling with levels... The only thing is the 201 JFETs are NOT something I can grab easily here... and my electronics is so basic that I don't know what/how to think about a substitute. In any event, I wonder how something like that will work as an external box? I mean, I don't particularly want to hack around my guitars to install battery boxes, etc... and yet I'd like to get some sort of small, battery-powered (meaning quiet) preamp arranged for each of the guitars... and Tillman's JFET design would fit in a matchbox (except for the 9V batteries - I don't think Lithium button batteries would work, somehow).
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Post by JohnH on Oct 2, 2008 8:26:17 GMT -5
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