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SS poweramp as preamp

Started by mgr800, June 15, 2006, 09:19:10 PM

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mgr800

I just found this site and am eager to comment on my rig. I'll spare you the effects before the amp.
first its a Crate GFX 15 practice amp which i run at full volume for distortion, the headphone out is sent to a transformer that i salvaged from the power supply from some computer speakers and a potentiometer as a master volume. This is all sent to a BBE 822 sonic maximizer which goes to the effects return of a Carvin SX-200 combo amp.
You got all that?
I really like the tone of set-up but i was just wondering if this is in some way bad for the amplifiers involved. I've been using this set-up (minus the BBE) for atleast 4 months.

joecool85

From what I gathered from your post it shouldn't be a problem since you are running it from the headphone out.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

mgr800

yeah i didnt really think there was a problem, i just like telling people about my rig and thought this would be  a good place.

joecool85

You should take a picture of it, I wanna see this thing.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

teemuk

Interesting setup. How did you hook up the transformer and what turns ratio does it have? I assume you have it "reversed" (if you can say this about transformers) so that it attenuates the signal from the headphone out and does some impedance matching as well. Do you have any resistors or other stuff in the circuit (besides the potentiometer of course)?

mgr800

I dont have any pictures but i drew up a quick diagram/schematic for it. The transformer does attenuate the signal but i put it there to get rid of a nasty hum from a ground loop. I used a power transformer because its all i had. I intended to replace it with a 1:1 audio transformer but i havent gotten around to it. I kinda like the way it colors the sound.

I just bought another used crate practice amp and i'm gonna tinker with it further. I also found a cool mod that uses a small lightbulb as a power attenuator that i want to try.

joecool85

Never heard of anyone doing the lightbulb attenuator on anything other than tube, but if it works it works.  If you do it, be sure to tell us about it.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

teemuk

Actually, the lamp attenuator should work better with SS. With tube amps the more load less watts rule does not hold true: Increasing secondary impedance will increase primary impedance as well. Increased primary impedance will mean more gain. Lamp may attenuate the power over the speaker but at the same time it pushes the power amp harder.

About turns, ratio: I think you have the optimal now. 1:1 might be too high since headphone out can have amplitude of few volts. If you drive a line level equipment or power amp in -jack something under 1V is usually better. Why I asked is that I might like to try something similar myself. What was the secondary voltage of the system you ripped out the transformer and do you have 110V or 230V?

By the way, I really like those low power Crate amps. I have a GX-15R. It´s one of the best low power amps I have ever tried although the distortion channel is a joke: Virtually undestructable, has a nice clean tone, very compact to carry to acustic jams etc. I swapped the speaker and it really does awesome job as recording amplifier. Has a really full and nice sounding reverb although the tank is one of the tinyest I´ve ever seen. Could improce with better switching etc. but I always couple it with outboard effects anyway.

joecool85

On the topic of small amps, I love my Dean Markley K-20X.  I personally haven't heard anything with as great a clean channel as it, and it has a really solid overdrive channel.  To tell you the truth, its basically my favorite overdrive sound.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

Ge_Whiz

Interesting rig. Reminds me of Dave Davies's rig from the early Kinks days, with his little practice amp overdriving something more powerful.


RDV

Quote from: joecool85 on June 16, 2006, 07:03:52 PM
On the topic of small amps, I love my Dean Markley K-20X.  I personally haven't heard anything with as great a clean channel as it, and it has a really solid overdrive channel.  To tell you the truth, its basically my favorite overdrive sound.
It's basically a Distortion+ as a preamp, the DM OD channel of yours. I used to run mine into a large Peavey amp back in the eighties for my rock gigs.

RDV