Tube Amps / Music Electronics
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|5/27/2003 10:21 AM|
||Re: Why not balance?|
I realize all that. I have quiet amps, and noisy amps. I'm still tracking down a ground loop in my rack, but I think I know what's causing it. I'm just trying to denoise as much stuff as possible in my room. I figure it's easier in the long run to put as little noise in a recording for CoolEdit to try to remove, than to possibly strangle a good sounding recording trying to remove it after recording.
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|5/27/2003 2:56 PM|
Nothing about the amp affects the contribution of the cord and guitar.
I understand your point but some tube amps seem to be particularly noisy with single coil pickups, especially if you are within 2 or 3 feet of the amp. The transformers on the Peavey Classic 30 seem to produce more noise with single coil pickups than other amps with comparable gain. Once you get about 4 feet from the amp that particular noise seems to go away.
So do you have any ideas for an all-tube guitar preamp circuit that would accept a balanced input? I.e., a way to wire up tube stages like the + and - inputs of an op amp...
|5/27/2003 4:05 PM|
Steve, the problem with single coils is the transformer hum is picked up primarily by the coil itself, and won't be affected by balancing. The cable picks up hum, too (which is canceled by balancing), but this noise is swamped by the noise from the pickup --as Enzo stated (or at least implied).
|5/27/2003 10:09 PM|
Steve, the problem with single coils is the transformer hum is picked up primarily by the coil itself, and won't be affected by balancing.
A balanced cable should reduce the noise from a single coil pickup since it would have a dedicated ground for the shields and a dedicated signal return (signal minus) line. But as you pointed out the hum still reaching the single coil [with the improved shielding] would not be cancelled out by having the output balanced.
Enzo had a good point: make sure that you have correctly identified the source of the noise before taking steps to reduce it. For example, switching your filaments over to DC when the problem is really lead dress. (Bruce mentioned a good way to check for noise from the AC heater supply... with the amp warmed up disconnect the heater supply. The sound should fade out but as it is fading out you can listen to see if your hum disappeared the moment you disconnected the heater supply. Alternately you can try hooking up a 6 volt lantern battery to the first preamp tube and see if that helps. It if doesn't then switching your filament supply to DC is not going to help that particular noise problem.)
In any case I'm still wondering if anyone has any ideas for a balanced guitar input that is all tube (with no transformer and no op amp). If we can reduce the hum and noise of an amp being miked even a decible or two that would help the signal-to-noise ratio a little bit (and every little bit counts!).
|5/27/2003 3:47 PM|
Actually, it's a good thing that so much has been unbalanced all these years. Here's why.
The rule of thumb for tape has always been wider tape on a thicker substrate and faster recording speed equals higher quality sound. Cassettes, with their too-slow speed (1-7/8ips instead of a preferred 15) too narrow tape (1/8" instead of 1" or 2"), and too thin tape (don't have the numbers handy) was sort of the worst case scenario for magnetic media, but the convenience it provided, not to mention low cost, were too irrestistible to the industry. What it did over the years was do its damndest to turn that sow's ear into a silk purse: figure out ways to make what should not have been workable, very workable. It's still not 2" tape, but everything that served to make 1/8" tape usable has helped to make 2" tape astounding.
In the same way, balanced holds many sonic advantages over unbalanced, but the convenience and cost aspects of unbalanced have been too irresistible to the industry and consumers. Just like 1/8" tape, the industry has striven to make the less preferable mode of signal conduction become as good as its traditionally upper crust cousin, whether by improvements to cables and shielding media, transducers, connectors, resistors or semiconductors.
Balanced will probably continue to be quieter than unbalanced in most applications, but the industry's desire to try and close that gap has brought some real improvements to the technology.
|5/28/2003 8:37 AM|
Balanced input stages have been around forever in mic pres. I am sure it would be straightforward to adapt one of those circuits. They come with and without transformers.
|5/28/2003 10:39 AM|
This all started with trying to connect as much stuff as possible as balanced. The ironic thing is, I still MAY want to use some of my unbalanced stuff (old ADA, Tapco rack stuff, etc., or reamping thru a stompbox)to grunge up things a bit. But I want the sound...not the noise. I realize I'm going to get noise. But part of the fun (and frustration) of having an 8 track R-R synced to a computer is trying to get an "old school" sound that is transparent. Heck, I could just use the Delta 1010, use only the balanced stuff, and use plug-ins for effects.....but what would I learn from that ? It's too late now, but it would be much nicer if everything had been adopted at one standard, (the better one), or there were easier ways to interconnect the different ones, but we do with what we have, I guess. I had tried to put all my EQ's together, all my reverb/delay/harmonizer,etc together, all my level tamers...etc....but that turned into patchbay hell, so I kept them together if balanced, then put the unbalanced stuff toward the bottom to further avoid confusion in patching.
As I said, luckily most of my stuff is either balanced or switchable...so I guess I lucked out in my pawnshop forays. (Wonder how many times before I decided to learn about all this did I run mismatched signals and wonder what was wrong?)
Anyway, thanks again...things are coming along. Maybe soon, I can be done with "the build" and get back to creating.
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