I need a great harp amp design

[67polara]

Now, I know nothing about harp amps but I have two people I play blues with on Thursday nights that play Harp.  They want a killer amp built for them.  This is what they tell me, Lots of Bass, Reverb and Grit.  Does that make sense?  Now one uses a 25 watt Fender Tube amp I don't know which one but has a 1X12, he hates it says underpowered no bottom, the other has a Blues Deville with 4X10's hates it to much power and no grit.  Now I'm thinking the TOS with reverb.  How do I get the Bass or possibly the lack of treble per their request?  I understand I need to soften the front end a lot and drop voltages down.  I think I need to remove at least 2 gain stages.

What are your thoughts?

Tony

[Fresh_Start]

Tony - starting with the T.O.S. then subtracting 2 gain stages doesn't seem to make much sense, at least to me.  That amp is designed for maximum touch sensitivity and a fairly high-gain overdrive, neither of which are things you want in a harp amp.

Do a SEARCH here for harp amp.  You'll come up with some basic ideas.  The AMPAGE Harp Amp forum has a lot of good ideas:  http://music-electronics-forum.com/f36/

I built a Super Reverb derivative with the "Normal" channel intended for harp use, and the harp player seems to like it a lot.  However, he likes a fairly clean harp tone, not that wonderful greasy Chicago sound your guys may be shooting for.

Maybe a Brown Vibroverb, single channel w/o tremolo, and lower voltages throughout the preamp would be a good starting point?  Guys seem to like Tweed preamp tone, sometimes even with that pre-common cathode gain stage topology (can't remember the name this second).  Fender reverb is the way to go for this applicaiton IMHO, but a Dwell knob would help a lot in controlling/limiting feedback.  Minimizing the number of gain stages would also be a plus.  Then you tune cathode bypass and coupling caps for harp-range values.  Just a possible idea...

Chip

[67polara]

ok, Thanks for the link I now see I am 180 out of phase here LOL.   So now looks like maybe a 59 bass man to start with a few voltage tweaks.  Add reverb--Done!  Does that sound right?

This what it seems like they need:

Weak saggy power supplies with low voltages.
Ability to break up early with out needing full volume yet still get loud if needed.
Low feed back.  (low voltages on tubes)

Now how do I get this done?  My guys want reverb also>

Tony

[jjasilli]

There is no "there" there.  For harp some people like a 5 watt amp from the '40's (which can always be miked).  Others prefer a BF Bassman.  There's a whole lot in between.  For clean tone, my hotrodded SF Princeton was (inadvertently) the best harp amp I ever heard.  And the harp players used it clean at a blues jam.  But it didn't sound like Little Walter or Paul Butterfield.

In sum  as presented this quest for tone is too vague.  It is not clear that either of your 2 potential customers actually agree on what their ideal harp amp would sound like.  So you could wind up chasing rainbows.  Can they identify a player's tone that they do like?

[bigdaddy]

Being a blues player I am familiar with harp players and no 2 want the same amp.

But there are standard things about the amp. One is low gain and saggy power supply's. Feedback is a huge issue. You have to rethink things and forget about what a guitar does. This is a microphone with a different impedance and when the player blows harder and bends notes it does jack up the output a lot.

Also many harp player use a different mic depending on the room. Some use only one mic......like I said everybody's different. The key is low gain and being able to control the feedback without losing power and still being able to get distortion. Remember those old amps having mic inputs, even accordion inputs.

I would suggest a few different inputs tailored to his microphones, maybe using their own preamp triode. Also stay away from high gain tubes like the 12AX7, maybe go with the big bottle 6SL7 and 6SN7 tubes to get a fatter sound with less gain. Also many harpies like mixed speakers like 2x8' and a 12". I know they do like those old alnico 8" Heppner speakers, they have a lot of mids, much more then a C8R, I know I have a bunch of them both. Maybe a 40-50 watt amp with 2x10 and a 15 using alnico lower sensitivity speakers like a pair of P10Qs and a C15N type??????

Big iron, low voltage(paralleled 5Y3s???), big bottles, a lot of sag yet a lot of preamp filtering and low gain with some ability to dial out feedback(some type of NFB/resonance control).....a tall order indeed but it can and has been done.