DIY Solid State Harp Amp Success!!!

I built my own all solid state 25W Harp Amp, and it works! Give it a listen (use good speakers or headphones), and let me know what you think. The amp is based on an lm1875 chip amp kit from qkits.com (25w chipamp), and the "professor tweed" distortion/preamp circuit from runoffgroove.com. If you want more details, check out my posts on the ssguitar forum www.ssguitar.com

Category:

Music

Tags:

• Blues
• Harmonica
• amplifier
• solid
• state
• diy
• homemade
• amplified
• mic
• preamp

[gullywoots]

cool project! I'd love to see people's faces when you take that radio onstage. do you have any samples of guitar plugged into that amp?

[isaacullah]

@gullywoots Thanks! I haven't made any vids of me playing guitar through it, but it sounds great with my Cigar Box Guitar. Actually, I think it sounds better with guitar than with harp. In fact, I basically only play guitar through it these days. I don't play it a lot, though because it gets really hot, especially if I crank it all the way up. I need to get a bigger heat sink for the chip amp, but I haven't gotten around to it yet!

[otofotobingoloto]

The amp is great, so bad you had to redord it with camera mic.

[isaacullah]

@otofotobingoloto Thanks! Yeah, I should record it with a better mic... :)

[ovation05]

I can't beleive you found a valve amp and replaced the guts with solid state. What were you thinking?

[isaacullah]

@ovation05 Well, 1) I found a Tube RADIO, not a tube amp. 2) The thing wasn't working 3) I built a brand new amp, and used the housing to give it a retro stle 4) Did you actually listen to the way it sounds? It sounds damn good.

That last point is all that matters, really. Just because an amp uses tubes, does not mean is will sound good. Just because an amp is solid state, does not mean it will sound bad. It's the circuit design and the frequency tailoring that matter, not the components.

[isaacullah]

Yeah, I thought it was a bit small too, but I've run it for several hours, and it only gets warm to the touch... The chip has never gone into thermal shutdown either....

I'm going to change out the pre-amp on this eventually.... The prof tweed is kind of a one trick pony, and I'm getting a little tired of it now...

[tuomollo]

I think that the heatsink is a bit too small

[fabzoundfactory]

very nice job for this rebuild amp , isaac !!!

[isaacullah]

Hmmm... I'll have to investigate this. You are certainly correct that too much bass distortion will "muddy" the tone. One of the mods I did was to lower the bass thrshold (not by much, but I definately lowered it). It's a common mod that folks do to fender guitar amps to "voice" them for harp. I'll stick an EQ pedal before the amp, fiddle with the input freqs., and see what happens. If need be, I'll raise the bass cutoff threshold on the first gain stage. Thanks for the comment!