Re: [Harp-L] SuproSupremeFinal sound file & JAYPHAT intro

[spschndr@xxxxxxx]

To Hal Iwan and anyone else who's wondering: Yes, the amps in the cycle 
of sound clips have got some tweaks, but those just highlight what is 
happening at the input end.  I will detail the amp tweaks at the 
initial mention of each amp.

The SuproSupremeFinal clip I put up on the Harp-L parking lot at 
http://google.com.groups/group/harp-l/files/ grew into a series of 
clips demonstrating some microphone impedance matching issues.  
(Right-clicking on the filename will let you save the file to your 
machine for playback if streaming doesn't work right.)  For those of 
you whose eyes glaze over at the mention of amplified gear, the clear 
finding on these clips is that proper impedance matching for your 
microphone can greatly accentuate your hand effects as you play, 
amplifying not only your volume level but the expressive aspects of 
your playing as well, making the whole rig more an extension of your 
instrument.

These clips involve an outboard impedance matching box designed/built 
by my friend Greg Schlacter ca. 2001.  What it does is buffer a 
high-impedance mic from everything downstream of it, and provide a 
steady high impedance loading for the mic element, minimizing loss of 
signal to ground and maximizing the micâs tone.  More on the box in the 
next post.

SuproSupremeFinal is my brotherâs 1947 Supro Supreme amp I was 
overhauling for sale, temporarily modified for harp with 0.1mfd 
coupling c
aps (to fatten tone) and no bypass cap on the input stage (to 
reduce preamp gain).  The first filter cap is 47 mfd; screen filter is 
20; preamp filter is 10 mfd.  This amp model has push-pull 6V6GTs with 
6SC7 inverter and 6J7 input tube, 5Y3GT rectifier, plus a 10â field 
coil speaker; very common postwar amp sold as Supro, National, Valco, 
Oahu, McKinney, I think Bronson, and more, as Hal mentions; the 
earliest ones have no tone knob.  It is basically a 6V6 version of the 
National amp that influenced Gerald Weberâs Kendrick harp amp design.  
1947Supro at the Files page is a photo of this amp.  You can find a 
schematic for this design by following the Amp Schematics link at the 
Weber VST Amps forum to Supro and Supreme.  A design quirk is that it 
has a very low input impedance of 100K; that dumps a lot of mic signal 
off to ground, really doesnât let older hi-Z mic designs do their best 
work.

You will hear this to a comical degree when I switch to the MC-151 
crystal mic w/ 5Meg volume pot, as both the lows and the overall level 
disappear.  Using the outboard impedance box changes that dramatically. 
 Using a controlled magnetic (CM) element straight in sounds pretty 
good, but listen carefully to what happens on the 4D when I add the 
impedance box: the sound with my hands open expands dramatically.  The 
impedance box doesnât induce serious feedback problems wit
h either 
mic--I was standing closer to the amp than I would on a stage--but it 
really emphasizes what Iâm doing with my hands as I play.

I returned the Supreme to guitar mode after making this clip, so it 
doesn't show up on the others.  On this clip I am playing a Bb Joe 
Spiers custom MB in 7-limit just intonation tuning; the A and D harps 
on the other clips are MBs I customized myself, also in 7-limit JI 
tuning.  I tried to play repetitive old-school bits with tonal 
exaggeration on these clips to emphasize the A/B differences.  Sorry if 
it gets boring.  Youtube addicts are encouraged to print out the photo 
file of the 1947 Supro amp and stare at the photo while listening to 
the Supro file, which is not much different than watching some Youtube 
amp clips.

Stephen Schneider