gbdweller
Structural Member
They used vulcanian corbomite...
They used vulcanian corbomite...
mshilarious
Banned
It wouldn't have to be low impedance output--although that is a good idea for other reasons, it requires power, and tube amp purists might not be enamoured of the idea.
Instead, simply float the pickups and create a balanced input stage on the amp. From the guitar's point of view, it would have to be wired slightly differently, but if you plugged a TS connector into it, it would work like a standard guitar as the plug grounded the cold output. But with a TRS cable into a sympathetic amp, it just might do the job. Heck, a guitar signal is orders of magnitude stronger than a mic signal, so it can't be that hard.
The trick is getting the amp makers to change their designs. For a solid state, no biggie, many have an opamp as the first stage, so just change the configuration. It's a little different to do variable gain in a differential input stage, so it might be tricky to do a mod, but in a new design, it would add essentially nothing to the cost.
Tube amps are harder, the typical input stage is single-ended, so there is an increase in cost there.
I did think of doing a balanced input version of my DI connector. I think I might have to get out the ol' So-Cal and see what I can come up with. I always have RFI problems in my house, due to the lack of funds to replace all the crappy dimmer switches with the good, quiet ones. So it is definitely something I could use, and I can change the input stage of my Extreme Peavey RAGE! to balanced input.
Schematics to follow if it works . . .
dgatwood
is out. Leave a message.
Engineer: We need to add balanced input.
Marketing: How much will it cost?
Engineer: About an extra $100 per unit.
Marketing: No way. Tell me how we can do it for under 50 cents per unit.
Engineer: Well, I suppose we could use a shitty Chinese transformer, but the sound would be horrible.
Marketing: I'll pass that on.
Marketing: The engineer said that we can add this feature for 50 cents by using a Chinese transformer or for $100 with a redesigned input stage. The sound will be acceptable either way.
Marketing Manager: I'll pass it on.
Marketing Manager: I'm told that we can save $99.50 off our manufacturing costs by using a Chinese transformer for our balanced input, plus we can save on R&D by not having to debug a new board layout.
Engineering Manager: Sounds great. I'll get the engineers on it.
Engineering Manager: I'm told that the best transformers for this job are made in China.
Engineer: Uh...
Engineering Manager: I want you to get with Chinese transformer vendors and find one to build into the existing amp design. We'll use the redesigned balanced input stage in a future, "improved" version. (The manager makes the quote fingers when he says "improved".)
Engineering: So when are we building the improved version of this amp with a balanced input stage?
Marketing: We cancelled that project. You said it wouldn't make any difference.
mshilarious
Banned
Yeah . . . . or they could add another 4580 for $0.10 . . . whatever. Why do I care what Chinese manufacturers do, this stuff is easy to DIY.
C
chazba
terminally hip
Hmmmmmmmmmmm!!!
Dgatewood has spent time in the corporate world. Sad but true that this is the way decisions are made in the world of mass production and mass marketing. Somewhere a boutique amp guy is reading this and going "hmmmmmmmm"
chazba
Dgatewood has spent time in the corporate world. Sad but true that this is the way decisions are made in the world of mass production and mass marketing. Somewhere a boutique amp guy is reading this and going "hmmmmmmmm"
chazba
mshilarious
Banned
I ain't gonna flatter myself that much. It's too obvious of an idea, which means that there is probably a good reason it hasn't been done.
Anyway, it occurs to me that 40 years ago plenty of people realized high-impedance unbalanced mics were not a very good idea. While Fender still owned Fender, he had both the amps and guitars in one house, so there would not have been the chicken-and-egg problem that other manufacturers might have worried about. Plus with the single coils, there was more to gain . . . if it works.
I will find out soon enough . . .
C
chazba
terminally hip
I just checked my "junk box" and found a handfull of mini xfmr's from early solid state days. I made a direct box from one and never found a use for the rest (till now...hmmmmm) I think I bought a plastic bag full of these for about a buck from Philmore in the mid 60's. Why does my wife say that I'm a packrat???
chazba
chazba
mshilarious
Banned
And the results! Sorry it took me a while, I had to get a suitable transformer, then wire it up in a connector, then rewire my guitar for a floating output . . .
OK, here we go:
The chain: A Fender So-Cal, with a single humbucker, handwound by me to about 5K ohm DC resistance. Pretty low for a hummer, but nice and bright like I like it. Rewired to floating output to a TRS jack. The control cavity is heavily shielded with copper tape, and the jack shield is connected to cavity, bridge, and pot case. Single volume pot is wired between the pickup leads and NOT ground-referenced.
Balanced: connected via 10' TRS cable to transformer adaptor (with floating input on tip and ring), then 10' XLR cable to ART DMPA mic input.
Unbalanced: the same, except using a TS cable to reference one side of pickup (and transformer primary) to ground.
Here is the "fingers off" comparison, not a surprise really, but still very nice to have:
mshilarious
Banned
And fingers on, not as audible, but nonetheless still quieter than unbalanced (sorry I reversed the color scheme on this one 
) :
) :
69 SG
Banned
What is Sheilding
What is Sheilding
Without reading any of this.
Are Solar Flares or EMI degrading tape over time or something?
What is Sheilding
Without reading any of this.
Are Solar Flares or EMI degrading tape over time or something?
Outlaws
New member
Wow. I can't believe I actually read all that crap.
mshilarious
Banned
As it turns out, there is a patent application for a similar balanced guitar idea:
http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&co1=AND&d=PG01&s1=20020073830&OS=20020073830&RS=20020073830
Although it isn't necessary to use the DPDT switch, nor it is necessary to use two separate coils in the manner illustrated, so long as the coil is isolated from ground. For the volume and tone controls, rather than ground-referencing, they can simply run between the two sides of the coil. A dual pot is helpful for volume; a single pot will work with some added resistors, but not as well. The switch becomes unnecessary when a TS plug is inserted into the guitar; that grounds the ring side and thus makes the entire circuit like a regular guitar.
The patent also doesn't specify the nature of the balun required, which is the trick. There isn't an ideal off-the-shelf transformer. I used a 200K:1K, which is fine for mic input, but it drops more dB than one would like feeding an amp. 200K:10K would be better, but custom wound jobs are expensive. A balanced input stompbox buffer would work too.
I wonder if any of the big boys have stepped up to challenge the patent; otherwise this guy will own the concept of balanced pickup wiring, since he claims any variation on the circuit, active or passive, including phantom powering . . .
http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&co1=AND&d=PG01&s1=20020073830&OS=20020073830&RS=20020073830
Although it isn't necessary to use the DPDT switch, nor it is necessary to use two separate coils in the manner illustrated, so long as the coil is isolated from ground. For the volume and tone controls, rather than ground-referencing, they can simply run between the two sides of the coil. A dual pot is helpful for volume; a single pot will work with some added resistors, but not as well. The switch becomes unnecessary when a TS plug is inserted into the guitar; that grounds the ring side and thus makes the entire circuit like a regular guitar.
The patent also doesn't specify the nature of the balun required, which is the trick. There isn't an ideal off-the-shelf transformer. I used a 200K:1K, which is fine for mic input, but it drops more dB than one would like feeding an amp. 200K:10K would be better, but custom wound jobs are expensive. A balanced input stompbox buffer would work too.
I wonder if any of the big boys have stepped up to challenge the patent; otherwise this guy will own the concept of balanced pickup wiring, since he claims any variation on the circuit, active or passive, including phantom powering . . .