Harmonica Amp Questions

[jmcglynn]

I'm thinking about building a harmonica amp. My requirements are

- 5-10 watts, essentially low enough power that I can drive it hard for tone at home and in small jam sessions without too much volume
- Ideally, tremolo built in
- Tone and gain optimized for harmonica

That last one is really the main question. There are no shortage of low-powered amp circuits I could copy or build from a kit, but my understanding is that not all of them sound ideal for amplified harmonica. My guess is that lower gain in the pre-amp and a more flat tone stack (no scooped mids) are the key bits, but I'm 100% guessing. Does anyone have any recommendations?

I have seen recommendations for the Kalamazoo Model 1 and 2 amps (not the weird late model 2 solid state one, the original tube version). Kalamazoo Model 2

So one option would be to just copy that, but I'd really like to understand what make purpose-built harp amps different from a guitar amp.

[jmcglynn]

The Weber 5F2H kit is the only harmonica-oriented amp kit I've seen. I'm concerned that it would be way too much amp for practicing.

I do have a Universal Audio OX, so I could deal with that just using it as an attenuator. In fact, I've been using it with my Tweedle-Dee that I built and set up a "rig" that has a 10" blue speaker, close and room mics, a little slap-back delay and eq boost in the low and mids and a tiny bit of compression. If I was far enough along with learning Harmonica I'd post a clip, but this is like day 3 or learning harmonica and I'm certainly not ready to have anyone hear me!

But I want to have a small combo that gives me the tone I want without so much gear. Plus, it sounds like a fun project.

[martin manning]

The 5F2H is still a pretty low power amp, looks like a moded 5F2 Princeton w/ KT66. Worth a shot, probably. A 6V6 Princeton would be around 5W, it's pretty much a Champ with a Tweed Deluxe tone control.
Looks like there is some pertinent info here: http://bluesharpamps.blogspot.com/2008/ ... -amps.html You can probably other sites that discuss harp amps.

This .pdf is something I saved some years ago on this subject.

[katopan]

I built this for a friend many years ago and he is still using it regularly. With the VVR it's good for home and VVR up full is good for modest volume jams with friends. At gigs he plugs the line out into the PA and it works a treat. I started working on an improved version that would have a bit more flexibility but never finished it.
https://sites.google.com/site/chosenaud ... hedforharp

For myself (I'm mainly guitar but dabble in bad blues harp playing) I built a 5F1 Tweed Champ sort of build (without tone control) and put a switchable 3.3nF cap across the whole volume pot to ground. Switched out it's standard Champ for guitar. Switched in works pretty well for harp. Got this simple idea from one of the Masco amps that's known as a good harp amp, which has that cap hardwired in.

One of the list of reasons why I built a 6G6-B Bassman was that it's not only a great guitar amp (both channels) but the stock circuit kills for harp with no mods, just very different knob settings. I use that if I need gig or louder jam level power. Instead of the normal hi/lo jacks, I made input '1' a 1Meg input impedance for guitar and reluctance mics, and input '2' 5Meg for my crystal mic on both normal and bass channels. Like for guitar, the two channels have a different flavour for harp but both work. Of course the presence gets set all the way down and then the treble is adjusted down in the bottom quarter to taste.

[jmcglynn]

This .pdf is something I saved some years ago on this subject.

Cool, I actually just found that same information myself here: https://www.harpamps.com/weber/Guitar51.html

On the same site there are pictures of vintage amps like the Premier 50 and Twin 8 that are popular with harmonica players.

It will be interesting to see if any of the vintage circuits follow the guidelines you posted. I looked briefly at the Premier Twin ( schematic and it doesn't use a larger coupling cap at least.

[martin manning]

Since we are talking harp stuff, I'll link this video featuring the late, great Norton Buffalo, playing with Bonnie Raitt and showing off his mastery of modulation: https://www.youtube.com/watch?v=HPzcZNgVfpA

[brewdude]

I don’t know if it’s true, but someone told me that when that amazing harp performance was taped Norton Buffalo was sick and suffering a 102F temperature.

[katopan]

Since we are talking harp stuff, I'll link this video featuring the late, great Norton Buffalo, playing with Bonnie Raitt and showing off his mastery of modulation: https://www.youtube.com/watch?v=HPzcZNgVfpA

Yeah man, that was awesome!

[jmcglynn]

I came across this site yesterday, it has a few harp-specific amp designs and reviews of commercial amps. He wasn't impressed with the Weber 5f2h kit, but I'm considering it.

https://harpamps.de/en/home.html

[martin manning]

Interesting site there. Weber kits aren't that great. What you would get out of it, or a Mojo 5F2-A kit for that matter, is a platform that you could do as you like with in the way of a 6V6 single-ended circuit. I'm not a big fan of Mojo either, FWIW. If a 6V6 (5W) isn't enough power, and you want to go to a SE 6L6 (10W), then look elsewhere as you would need to get new transformers.

[jmcglynn]

Here is another site, and this link specifically is for a DIY SE 6L6.
https://www.lonewolfblues.com/proj6l6se.html

I'm more concerned about too much power than too little power. I built a Ceriatone Tweedle Dee kit recently -- and I love it -- but it was too loud to play at a jam session at work in our studio. At home I play it though my OX box, but if I ended up with a single combo that had a killer tone but was too quiet for jam sessions (hard to imagine) or gigs (likely) I'd still count it as a win I think. 90% of my use will be at home practicing -- certainly until we're past the pandemic and I can play more than four notes haltingly

[jmcglynn]

I tried something different last night -- this is more complex and totally not in line with my end goal of a small single combo -- but I like the tone a lot. Certainly not in my budget or most people's, but I work at an audio company so I have access to this kind of stuff to experiment with.

It's a Universal Audio 710 mic preamp, this one has both a tube (12AX7) and solid state amp mic preamp in parallel with a blend knob between them. Bullettini harp mic into a Flashback2 for a little slapback delay, into the Hi-Z input on the mic pre, then into my audio interface so I can listen through headphones. I could set up a studio monitor but honestly I'm not a point where anyone wants to me me yet

With the blend all the way on "tube" and the gain cranked up and the level down the tone sounds better to me than other things I've tried so far. I'll practice a bit more and then maybe post a sound clip - maybe I can record something dry and then through the 710, and once more with the delay added for comparison. Four notes, three combinations, that should only take me the rest of the day.

[martin manning]

I'll bet that does sound nice. Nice single ended 6L6 amp here with an attenuator: https://ampgarage.com/forum/viewtopic.p ... 76#p410876 Maybe a MV at the input to the power stage would do as well or better. You could drive the second stage a bit harder, and then knock the volume down with the MV.

[pdf64]

Unless you’re in an ‘instrumentals only’ kinda band, there’s going to be a PA; so should you need to be louder, mic up your combo. It’s a lot easier to get good results making a quiet amp louder than a loud amp quieter.

[billyz]

There are a lot of misconceptions about what makes a good or great Harp amp. Yes, it should have a low or Olden times normal gain front end. The biggest factor to getting the Overdriven Harp tone is the Microphone ! and how it's cupped or sealed. Which overdrives the Element. This is why Bullet mics excel . Get an older Shure CR element, high impedance, put it in a Jt30 shell and seal it with a good gasket ( front to back ) of the element. This allows the element to be " Crushed by your air" takes practice to get a really great tone. Open up your chest and airways, breathe from your diaphragm. I can make virtually any amp, big or small sound overdriven with this technique. Twin Reverb, no problem . The reason you see so many great players use bigger amps is for the bottom end . Bad mic, Bad technique = bad thin tone. Of course this is for the Blues tone, Country = no cup , use a modern mic, different technique.
MY favorite amps for Harp are, 47' Supro ( two 6v6's , 10" Jensen), 57' Gibson Maestro ga45t ( two 6v6's, 4 8" jensens), 57' fender bandmaster, ( stock). But I have gotten great results with a 68' Bandmaster reverb and a 66' Vibrolux reverb. I built a SE 6l6, with 3 5x7" jensens.
grid leak 12ax7 input, cathode biased stage 2. Lots of filtering, gigantic inductor for low noise. He loves it.