Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: LooseChange on September 16, 2010, 04:26:15 pm
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I know that having a big loud clean (Like a Twin Reverb) is the way to go but I want more...
I'm Looking for some ideas on how to mod the typical Fender tone stack to work best with a pedal steel guitar. It's quite possible that the Twin is already perfect but what do you say?
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LC, I've spent literally hours playing around w/ different values using Duncan's calculator and came up w/ something I've used many many times. It has a better response in most everything I use it in and I wonder if others will shoot me down about it or might like it as much as I do? But IMHO it gives a better response than most everything I've used it in. Here's the values and I'd really appreciate honest feedback from other's trying it. PS - this isn't reinventing the wheel but I don't quite ever see everything being exact and it really has to be for the response to work as it does. It has just enough scoop in the right place and the bass response can be changed slightly depending how much you need by going w/ a .1 to a .02 -
using the fender/marshall stack but w/ these values:
250k-B treb pot, 1M-A for bass pot
500pf to lug 1 of treb pot, 100k slope, .1 to .02 (cap for bass amount) to lug 2 of bass pot, .01 to lug 3 of bass pot
I like a 10k mid resistor for only a two control Treb/Bass set-up or you can do whatever value when using a pot for mid ie, 25k or 50k. But I find better overall control and use w/ the 25k (based on my settings mostly being between 1 & 6 when using a 50k pot while playing)
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Pedal steel PU's can put out 1 volt, so you want a 1st stage that can handle that. Cathode resistor value is signifigant for input signal voltage. Dave Funk 's Tube Amp Workbook recommends 820R - 1K for this purpose. Per Dave Funk and a recent thread here (with great info from Merlin) you can temporarily use a 50K pot to dial in your cathode resistor value.
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After buying a cheap lap steel and trying to play it....wow you have no idea how much it hurts after a few minutes of holding a tone bar when you're not used to it......I also have listened to a lot of pedal steel players too.
So honestly the first issue is in fact the output of it. That's a lot of power coming from all those strings and so much sustain from the tone bar as opposed to a pick. So for the first stage a low gain setup might be a good idea. Plus a good power supply without any sag that can handle the low notes.
But I think the whole real issue is the speakers. The lows and highs are amazing from a lap steel and the old timers always used a 15" speaker and a clean powerful amp. That's why yes a Twin is probably perfect from jump street except for the 12s. It needs a 15" speaker like an E140 JBL. Having the aluminum dome helps reproduce the highs cleanly. The only other approach would be to use a Xover and a quality horn like modern bass cabs. Making the sound with pedal steel, then the amp and then reproducing what the amp amplified is the key.