Treble bleed alternatives

[Joe Gwinn]

Guitar cord capacitance typically runs about 20-30pF per foot. I think George L's is 21pF. 5pF/ft is almost impossible, because the capacitance depends on the logarithm of the ratio between core and screen diameters. To get the capacitance down by a factor of 4, you have to make the centre core e^4 times, or about 54 times smaller.

There are many coaxial cable types with about 20 pF/foot capacitance, but they are easily crushed if stepped on, as the dielectric is a very airy polyetheylene foam. I agree that 5 pF/foot is likely impractical for a flexible cable.

Scope probe leads need very low cable capacitance, so they use a hair-thin steel wire in a foamed poly dielectric. The wire breaks easily and is a PITA to mend: you couldn't use it as guitar cord.

The wire is made of nichrome, I think. The intent is to make the cable a distributed RC structure that will preserve pulse shape at the expense of attenuation. Such probes typically attenuate input voltages by a factor of ten.

[Mike Sulzer]

Craig Anderton also used to do blind tests showing that people struggled to tell the difference between solid state and tube guitar amps. That would get him burnt at the stake here :-)

Guitar cord capacitance typically runs about 20-30pF per foot. I think George L's is 21pF. 5pF/ft is almost impossible, because the capacitance depends on the logarithm of the ratio between core and screen diameters. To get the capacitance down by a factor of 4, you have to make the centre core e^4 times, or about 54 times smaller.

Scope probe leads need very low cable capacitance, so they use a hair-thin steel wire in a foamed poly dielectric. The wire breaks easily and is a PITA to mend: you couldn't use it as guitar cord.

I am with you on the guitar cable, but there must be something wrong with those amp comparisons. First, guitar amps are typically played non-linear, a little or a lot, or anything in between. It takes a lot of design work to make a SS amp that distorts like a tube amp, and when I say "like", I mean you can get close, but I doubt that you can really get it exactly the same.

I was very pleasantly surprised when one of my daughters, home for a visit, said without being asked, "Wow, that sounds exactly like a 70's guitar." She was hearing a guitar with a low level solid state distortion circuit I had built played through a clean tube guitar amp. Why still use a tube amp if you can get the distortion pretty well with an SS circuit?

Consider the clean sound of SS and tube amps. It is easy these days to make an SS amp that is extremely clean with very little coloration. Tube amps always have some coloration. You cannot get rid of all the distortion. This is from the tubes themselves in practical circuits and the transformer has an audible effect even at low levels.

This tube coloration has become part of the accepted sound of the guitar. It is not easy to duplicate it with SS. Nor is it difficult to conduct a good listening test to show that it is there. I suppose that you can duplicate tube coloration as closely as you like if you work hard enough, but is it worth it?

[David Schwab]

Consider the clean sound of SS and tube amps. It is easy these days to make an SS amp that is extremely clean with very little coloration. Tube amps always have some coloration. You cannot get rid of all the distortion. This is from the tubes themselves in practical circuits and the transformer has an audible effect even at low levels.

Some people forget about the role of the output transformers on the tone.

Bassist Jonas Hellborg co designed an amplifier with bass maker Warwick that combines a SS power amp with an output transformer.

This tube coloration has become part of the accepted sound of the guitar. It is not easy to duplicate it with SS. Nor is it difficult to conduct a good listening test to show that it is there. I suppose that you can duplicate tube coloration as closely as you like if you work hard enough, but is it worth it?

One story has it that Leo Fender rejected the first speakers he got from what ever company he was getting speakers from because they were too clean sounding.

Not only is tube distortion part of the sound of guitar, and popular music, but so are the various early guitar models, such as Fenders and Gibsons, and their associated pickups. The music was created around the sound of those elements.

[Possum]

...

the George L cable showed up yesterday a 15 footer, very nice cable, lets alot of treble through. The plugs they use screw into the cable to make contact and read you can have problems with these if you abuse the cable etc. but I figure if the connection goes bad just cut off that part of the cable and screw on the plug for a new connection.

Mike I'm surprised you support that view of tube amps, thats not a very engineery point of view I don't think there's a SS amp made that do everything tubes do or I'd be first in line to buy one. Where the SS amp modelers fail is in the borderline area where a tube amp isn't totally cranked or totally played clean, but just with a little bit of grit. The SS can do the extremes pretty well but not the little bit of tube grit tone. Funny thing is alot of jazz players like SS amps, like the Polytone I think its called, George Benson loves that amp as others do. I still think the best jazz tones I heard are the earlier stuff through tube amps with some distortion and P90s or Charlie Christian pickups, those tones have so much more character to them for me.

[Mike Sulzer]

Mike I'm surprised you support that view of tube amps, thats not a very engineery point of view

Engineering is whatever it takes to get the job done. In audio that means if there is an apparent contradiction between what you think you hear and the way theory says it has to work, you must track it down.

I agree, a bit of crunchiness is hard to do with SS. If someone has found a way to get the "clean" sound of a tube amp with SS, more power to them!

[Steve Conner]

I don't see any (engineering) reason why we shouldn't have boutique solid-state amps that have all the tone and touch response of tube ones.

I've done a fair amount of experimenting with SS and hybrid amps in the last few years, and have been pleasantly surprised at every turn.

You can make JFET circuits that have the "little bit of dirt" like tubes do, and you can make solid-state power amps that have a high output impedance, presence controls and so on, to get that presence boost that makes tube amps sound "alive".

You can make solid-state power amps that soft-clip too, but it's academic, because 95% of tube musical instrument power stages don't! The clipping in all the classic amps, Plexi and so on, is hard and nasty, caused by running the power tubes into grid current. You can take an old Maplin Mosfet 100 watt amp module, overdrive the hell out of it, and it actually has better clipping behaviour than a 100 watt tube amp. So you can just beat crap out of the power amp, and if it's going through a good guitar speaker, and it's not some bipolar design that sticks to the rails and recovers slowly from clipping, it'll sound fine.

I think all our little three-legged friends have is an image problem. Everyone believes they sound like crap, so when people fire up a transistor amp they hear crap. And this image problem is self-perpetuating, because it means that transistors only get used in cheap crappy amps with cheap speakers and particle-board cabinets, that are perceived as second best.

I believe the truth is, like tubes, transistors can sound any way a good designer wants them to sound. But because of the image problem, they don't attract good designers with good ears for tone.

Speaking personally, my next amp build is going to be a hybrid, and the one after that pure solid-state.

[David Schwab]

I think all our little three-legged friends have is an image problem. Everyone believes they sound like crap, so when people fire up a transistor amp they hear crap.

Right, and then they stick a TubeScreamer before their boutique $4000 4-watt tube amp...

[Steve Conner]

Well, it's called a Tubescreamer, so it must have tubes in it! I knew a guitarist who believed that and I struggled to convince him that it was solid-state.

I let him play through my homebuilt tube amps, but he always insisted on using the clean channel with his Tubescreamer, over my carefully tweaked all-tube dirty channels. :-(

Sometimes we would swap instruments at gigs, I would play guitar and he would play bass on a number, and I got to play my amp set up the way he liked it, with his pedalboard. I had to admit that the Tubescreamer sound, though it's kind of harsh and transistor-y in the lab, works well in a band context. When you play it live the harshness makes it harder and more cutting than an all-tube circuit, and that contrast worked nicely with a tube clean channel.

Of course you can argue that I just don't know how to design a dirty channel. :-(

Oh, and I thought the Warwick amp with the output transformer was crazy! One of the reasons people like SS bass amps is that they weigh less, so why stick another big lump of iron in there?!

[David Schwab]

Well, it's called a Tubescreamer, so it must have tubes in it! I knew a guitarist who believed that and I struggled to convince him that it was solid-state.

I have an old BK Butler Blue Tube. It can sound just as harsh as a solid state overdrive. I think the old Anderton Tube Sound Fuzz circuit sounds a little more like a tube amp on fuzzier settings.

I've modded a few TubeScreamers for people, and they sound a lot better once you change a few things.

Oh, and I thought the Warwick amp with the output transformer was crazy! One of the reasons people like SS bass amps is that they weigh less, so why stick another big lump of iron in there?!

I prefer SS bass amps because they feel quicker. I have a very nice sounding Mesa 400+, and it's just too damn heavy. It was never as loud as my GK 800RB without breaking up, but it sounds good at moderate volumes.

Also with the advent of high powered SS bass amps bass players could actually hear themselves on stage!

[Mike Sulzer]

I don't see any (engineering) reason why we shouldn't have boutique solid-state amps that have all the tone and touch response of tube ones.....

I agree with that, but we might disagree with how hard it is to do. A sort of generic design tube amp sounds pretty good for guitar and can be really good without too many changes. A generic SS amp does not. You have a lot further to go to make it good.

[RedHouse]

Just got back from being out-of-town, I'll do multi-responses in one post...

...most guitar players like the change in taper...A parallel resistor is the only way to get a circuit that works somewhat evenly at all volumes.

I personally disagree after testing both ways with push-pull pots on a few guitars, but of course your mileage may vary, and if it works well for you then you're there.

Would you provide me with a product number for that cable?

Thanks.

Sure Mike, here's one I use when I need decent multi-conductor wire for a in-instrument wiring harness, it's Mogami W2901 (and Canare has an equivalent), it's actually meant for use as a balanced microphone cable on lavalier mics but it works VERY well inside unshielded guitar cavities. Ah but I see I was mistaken as it's actually 9pF/Ft. I guess in my mind I was thinking 3-5pF because typically one uses about 6" of wire from the pickup to the controll cavity.

...you don't get the dulling effect when you turn down the pot. The tone stays even...

Sure an onboard preamp works nicely but an on-board preamp requires installing a small PCB/Circuit and worse ...a battery (or rigging for phantom power) which is why the simple 2-component treble bleed circuit is always the "next best thing" and more importanly the least disruptive to restoration of the instrument should that be required.

When I get jobs that request a treble-bleed, I try my best to talk the user into swapping out one of their tone control pots for a push-pull pot so the treble-bleed can be switched in or out on demand.

Actually there are very few factory made guitars with decent wiring harnesses, almost all of them can be improved on. You just have to try it or you will never believe it, theory holds no water in this case. If you prefer the plastic coated wire with the foil shield and thin tiny leads over vintage cloth wire, cut identical leads of each, say 2-3 feet long and use your Extech and read the capacitance of each, the vintage cloth/braid wire wins everytime. But there isn't ONE version of the vintage braid/cloth and they vary in capacitance from manufacturer to manufacturer. I have a custom made tele that cost a ton of money and the luthier wired it with that awful plastic crap and it really dulls the sparkle from the single coils alot. He used a complex switing deal so just don't have time to rewire the guitar from scratch.

Changing your guitar cord isn't going to help your wiring harness at all. You need to start at the source, guitar cords are secondary and much easier to change. I just got a George L cable today, so I'm not blind to guitar cords. Fender makes a cheapie low capacitance cord for about 25 bucks but the molded ends always fail, been through 3 of those so far and done with 'em.

But the "decent" factory made guitars do have decent wire and rarely require a wiring harness upgrade. When I say Les Paul I mean Gibson not Epiphone, Strat not Squire/MIM. Most of the guitars and amps that come through my shop are decent stuff, I don't get many "off shore" guitars come through, I'm recalling like one Epiphone in the last seven years and two MIM/Strats both belonging to my nephews. I had an old Silvertone and a Teisco come through last year but wiring harness cable capacitance wasn't an issue ...originality was.

I agree about theory, one does need to audition the component after setting down the spec sheet and calculator.

Are you really putting 3 feet of wire into your guitars?

When you do put 3-ft of cable are you really finding cable capacitance becomming a problematic low-pass filter? Hmmm.

If it's not shielded cable, you wont have capacitance issues. If the insulator between the shield and the hot is thicker, the capacitance should be lower.

Vintage cloth/braid wire loses if you need 4 conductor cables...

TOTALLY agree with that! In fact when doing full cavity shielding jobs as I often do, the need for shielded wire vanishes and the cable capacitance issue drops to virtually zero.

Craig Anderton also used to do blind tests showing that people struggled to tell the difference between solid state and tube guitar amps. That would get him burnt at the stake here :-)

Guitar cord capacitance typically runs about 20-30pF per foot. I think George L's is 21pF. 5pF/ft is almost impossible, because the capacitance depends on the logarithm of the ratio between core and screen diameters. To get the capacitance down by a factor of 4, you have to make the centre core e^4 times, or about 54 times smaller.

Scope probe leads need very low cable capacitance, so they use a hair-thin steel wire in a foamed poly dielectric. The wire breaks easily and is a PITA to mend: you couldn't use it as guitar cord.

Craig was a typical EE no disrespect intended, he was good and a ground breaker, helped get DIY effects into the mainstream and yes I read his columns and bought his book back in the 70's. But a good example of an EE that can use his ears is Tom Sholtz, he was able to find sound.

Guitar cable is indeed typicaly as high as that Steve, but my post was relative to in-instrument wiring harnesses as Possum had mentioned regarding replacing "crappy" wire with other "less crappy" wire. I use low pF/Ft wire when I need to in wiring harnesses, then I use Canare or Mogami, most of the time I prefer to do a cavity shield job and then use individual un-bundled wire. I was responding to wiring harness ideas, it was Mike that brought the guitar cable issue into the thread.

...I had to admit that the Tubescreamer sound, though it's kind of harsh and transistor-y in the lab, works well in a band context. When you play it live the harshness makes it harder and more cutting than an all-tube circuit, and that contrast worked nicely with a tube clean channel.

"Ding....." and Steve just hit reality bell, c'mon down!.

Playing (whatever) guitar with (whatever) pickups through (whatever) effects and (whatever) amp setup in a lab/shop/bedroom/basement/garage etc just doesn't cut it when trying to critically compare/evaluate components and component substitutions (A-B) including Treble-Bleed circuits.

One must definately get the gear into the right environment, most often live, stage volume, with the other instruments (at volume) ...then decide what works and what doesn't. Your tube sceamer example is quite accurate, alone with just the guitar and an amp and one's self in a room a tube screamer sounds, well, crappy, but get it in the right environment and it can sound really good.

When I first started working on guitars and amps 36 years ago, my immediate goal was to get the gear to sound as good at the gig as it did in the shop. It was easy with my own stuff because I could make notes and make alterations the next day, but when it came to doing work for others I most often had to go to their gig and listen and make notes and then take their gear home and work it then bring it back next night. It was the only way to actually get the stuff to sound right.

Anytime one auditions the gear outside the target environment it's a crap-shoot as to whether it will sound right at a gig or a jam.

Of course if one doesn't gig then one's work is finished in the shop. One tweaks it to taste, leaves it alone, and swears that it's the "best" way to have it. That's where disagreement arises when communicating with others, what works in the shop rarely optimal on the stage or at least jamming at playing volumes with others.

Recording things can bring out the "ear" in people when they're not playing the instrument. When you play an instrument like a guitar/bass you have more than just he "sound" that others hear entering your consciousness, you get tactile and vibratory feedback from the guitar/amp-speakers and you are much more sensitive to the instruments response and play differently than when you are not playing and critically listening to an instrument being played.

In addition sometimes, as in the case of treble bleed, a player (not listener) can percieve the additional treble (or loss of bass if you will) as more "spank" or presence, or definition, and appreciate it as a good thing, which tends to allow one to play better because they get into the sound more, while on the other hand another the person in the room listening (not playing) might say it sounded better w/o the treble bleed based soley on it's sound w/o tactile feedback.

[Glass Snuff]

You make a lot of good points, Brad, in particular I like the last paragraph.

Since this is the pickup maker's forum, I have a related question (that maybe should be a new thread) - why don't pickup makers sell pickups with a wiring harness dialed in to their pickups? At the very least, it would seem a given pickup might work best with a specific volume pot load.

[RedHouse]

You make a lot of good points, Brad, in particular I like the last paragraph.

Since this is the pickup maker's forum, I have a related question (that maybe should be a new thread) - why don't pickup makers sell pickups with a wiring harness dialed in to their pickups? At the very least, it would seem a given pickup might work best with a specific volume pot load.

I don't know glass, doesn't EMG provide a wiring harness? regarding a pot load the industry is kinda settled on 250K and 500K for passives and 10K-50K for actives.

[Steve Conner]

The 9pF/ft for the Mogami cable is a "partial capacitance". It's the capacitance between the two cores, but you also have to take into account the capacitance between each core and the screening, which is listed as 54pF/ft.

So when wired unbalanced, as it is in a guitar, the Mogami stuff actually has 64pF/ft. That's what I'd have expected from microphone cable: higher capacitance per foot than guitar cable.

Maybe the extra capacitance affects the tone in a good way, I don't know.

@Mike Sulzer: Generic tube amps sound good because of a happy accident. Tubes are so musical-instrument-friendly by their nature that you can throw together a circuit from a Mullard handbook, plug a Strat into it and it'll sound good even though the designer has no clue what he's doing. They're almost little instrument parts in their own right, like the strings of a guitar or the reed in a saxophone.

But with solid-state devices you need an understanding of what makes tubes sound good, and how to emulate it. So maybe generic SS amps sound bad because they were designed by people who don't really understand tubes.

[Mike Sulzer]

Sure Mike, here's one I use when I need decent multi-conductor wire for a in-instrument wiring harness, it's Mogami W2901 (and Canare has an equivalent), it's actually meant for use as a balanced microphone cable on lavalier mics but it works VERY well inside unshielded guitar cavities. Ah but I see I was mistaken as it's actually 9pF/Ft. I guess in my mind I was thinking 3-5pF because typically one uses about 6" of wire from the pickup to the controll cavity.

Thanks, but that's 54 pF/ft from either conductor to the shield and 9.8 pF/ft between the two conductors.This could be significant in a Gibson type guitar on the path from vol pot to switch and to the jack. (You probably do want shielded cable on that path.)

It should be possible to use some of the lower pF/ft cable that Joe mentioned because it is protected inside a guitar.