Good Mods for Harp Amp Designs

[Magnatron]

I would like to build a new amp based on the 5E3 or Princeton design that is more geared toward harp use. Harp has some special challenges from the standard guitar circuit designs. The popular purpose-built amps lean toward the bass frequencies without being boomy or flabby, and generally have lower gain preamp tubes as the mics drive to feedback pretty quick. These mics can be dynamic, controlled reluctance, or crystal. The amps in most cases outside of the Bassman size are generally 5-20 watts driving 10" speakers.

What circuit design mods would be recommended to build a harp-purposed amp?

[Reeltarded]

Fairly stock with a large treble cap to dump more range. If it is muddy, a smaller and smaller early stage coupling cap. This can depend on speaker as much as anything. Celestions get your target bandpass without doing anything to a 5e3.

What mic do you really like? SM57 with boiled out transformer and blocked vents makes a virtual SM7 with good rejection and lower output. It is a good and cheap choice and maybe even the best depending on player's technique. You can over-blow the living shit out of it and gain the amp more without surprise feedback explosions.

[Magnatron]

Fairly stock with a large treble cap to dump more range. If it is muddy, a smaller and smaller early stage coupling cap. This can depend on speaker as much as anything. Celestions get your target bandpass without doing anything to a 5e3.

What mic do you really like? SM57 with boiled out transformer and blocked vents makes a virtual SM7 with good rejection and lower output. It is a good and cheap choice and maybe even the best depending on player's technique. You can over-blow the living shit out of it and gain the amp more without surprise feedback explosions.

My current mic is a BlowsMeAway Bulletini, which uses a dynamic element with some special tweaks. I've talked to folks with Fender Deluxes and they don't seem to like the amp for harp. Too shrill is the most prevalent comment. I really like that amp for guitar though, but hoped to use the dirt it's known for with a harp. I've been partial to Weber speakers in my other builds. I have a couple of purpose built harp amps now -- a Windy City Plus and a Harpgear -- but wanted to try my hand at building one myself.

[martin manning]

If you haven't seen it, in this newsgroup archive there is a link to Gerald Webber's harp amp recommendations (link still works) and some comments on them.
https://alt.music.harmonica.narkive.com ... s-for-harp

[arnenym]

This thread is a year old now, but i put in some of my tips anyway.
Replace one of the lo inputs with a 1M Linear pot and replace the 1M resistor with a volume pot.
https://ampgarage.com/forum/viewtopic.php?t=23447
For a browner sound you can separate cathodes on V1 with one 1,5k resistor and 47uF bypass cap. The other cathode could be a grid biased triode.
Connect the volume pots as it is on a Bassman with the Wiper out and sepparation 270k reistors. Put the treble cut after the resistors.
The amp can be a "little to kind!" if you do both mods but you can always have the master volume on max.

A alternative to a pot you could tame the amp with a 2 resistor voltage divider instead of a master volume pot.
For example a 220k resitor -out to PI-750K resistor to ground.