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Topic: Low Impedance Pre-Amp??? |
Pete Burak
From:
Portland, OR USA
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Posted 25 Dec 2005 1:12 pm |
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So I was reading a write-up on a Low-Impedance Pre-amp, and wondering if there is a need for this in the steel world?
Is there already something like this for steelers?
This was for a circuit that mounts in a guitar.
I know the SGBB does a similar task, but not sure about the Low-impedance thing.
(snip)
The buffer drops the guitar's output to a low impedence, which does a number of things including allowing you to run the signal through long lengths of cable with much less signal loss, like a low-z vs. hi-z mic. It's also great for driving effects and maintaining the highs in your signal. With your signal buffered the guitar's hi-z pickups don't get loaded down by effects.
This allows you to have a wide open signal to your effects chain and have the post-effects volume controllable from the
guitar.
It also allows you to true bypass the entire effects chain using a switch on the guitar. With the effects seeing a constant wide open signal their sound is more reliable, especially with touch-controlled effects.
Ever dial-in the perfect sound on an effect and then change the volume on your guitar and have the tone go out the window?
You don't get that with this unit.
The the onboard loop requires the guitar's signal to go through lots of cable, making the buffer preamp at the beginning of the chain critical.
[This message was edited by Pete Burak on 25 December 2005 at 01:14 PM.] |
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Jack Stoner
From:
Kansas City, MO
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Posted 25 Dec 2005 4:18 pm
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There are many devices around that have a Low Impedence output. The Hilton Pedal, I think, has a Low Z output. The old "Lil Izzy" provided a low Z output. The Goodrich devices such as a "Matchbox" may have a Low Z output. Many stomp boxes have Low Z outputs.
I have an old MXR Microamp and it has a Low Z output.
Low Z will allow you to drive a long distance and not have any frequency loss, but if you are under 20 ft then High Z (Impedence) will work just as good for guitar (instrument) levels. If you were going to feed the steel directly to a mixer board you would need a balanced Low Z (e.g. XLR) which is different than an "unbalanced" line like a standard guitar cord and in most cases all you need is a "D.I. Box" to connect directly to a board.
On an acoustic guitar pickup, many need a preamp to amplify it to "instrument" level. |
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Dave Mudgett
From:
Central Pennsylvania and Gallatin, Tennessee
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Posted 25 Dec 2005 5:00 pm
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Most well designed guitar pedals have a high impedance input and a low impedance output, for precisely the reasons in your snip.
This thread, started by Brad Sarno, has perhaps more on the subject of input/output impedances than most people would want to know. 
http://steelguitarforum.com/Forum11/HTML/007805.html |
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John Bechtel
From:
Nashville, Tennessee, R.I.P.
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Posted 25 Dec 2005 7:26 pm
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I recently found an old AB Open~Back 250K Audio-Pot from an old Fender Pedal that I once owned. Since clean/clear 500K Audio-Pots are so hard to find nowadays, I used a superb cleaner on my 250K Pot and replaced the noisey 500K pot with it. I really don't notice any difference in the two pots, except for the lack of the scratchyness! What am I missing/losing by doing this? My P/U's are Geo. L. 10–1, then through a Kleen~Kick, which I guess is similar to the Izzy+ and then through my Volume-Pedal and into my ’65 Re-Issue Fender Twin~Reverb Custom™ 15 Amp. _ _ _ _ I’m convinced the different pot has nothing to do with another problem, because; I had it before the pot-change. And that is a slight amount of distorted sound when using the Kleen~Kick, even with a fresh battery, in this All-Tube Amplifier! _ _ _ _ My most important concern is about any loss by switching to the 250K Pot.
------------------
“Big John” Bechtel
Burgundy D–10 Derby
’65 Re-Issue Fender Twin–Reverb Custom™ 15”
Current Equipment
Newest Steel
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Brad Sarno
From:
St. Louis, MO USA
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Posted 28 Dec 2005 8:16 am
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Pete, great topic. Those low impedance issues are commonly addressed with the many buffer products out there. On my Revelation Preamp I have two stages where the impedance is lowered. The input buffer stage where your guitar plugs in has a low-z output which then goes to the volume pedal. That allows you to run long cables and add effect pedals and not risk tone loss. Then after you come back from the volume pedal (or any FX pedals) the preamp is high impedance until the final stage where the output driver tubes are set up for low-z outputs for the same benefits. Preamps like the Alembic F2-B have hi-z outputs. That's really not a problem if you keep your cable runs short, but it does create limitations. Low Z can drive forever, well almost.
Brad |
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