This is the Peach Guitars version of the Hudson Broadcast, as traced by V1nce69 and posted on the Guitar FX layout forum. Others also did work on tracing in this thread, so sorry if I left anyone out. Lots of great gut shots and a bunch of measured voltages there too.
The layout is basically a redraw of the original, which used 0.15" vero - but without the charge pump daughter board (I'm not a big fan of using charge pumps, as most pedal power supplies have high voltage outputs these days).
You can't use these layouts on standard vero, or if you do, you'll have a hell of a time getting it all to fit.
HUDSON BROADCAST - 0.15" VERO LAYOUT
Note: The gain switch can be either ON-ON or ON-OFF-ON. Stock is ON-OFF-ON
HUDSON BROADCAST - LTSPICE
This is trickier than usual to model, as a germanium transistor and a transformer are involved. LTspice doesn't have a transformer model library (which is annoying), so you have to model your own using inductors. I measured the inductance and resistance of a TY-141-P transformer, so hopefully, the model is close. Same with germanium transistors - they can be different enough individually, let alone simulating one.
Anyways, here it is.
If you like more bass, decrease R13. I found changing the 330n capacitor moves the mid-range peak in conjunction with the lo-cut control. Increasing to 1u brings the peak lower, at the cost of some high frequencies elsewhere.
The overall response can be quite gain dependent, as it appears to have a bit of a mid hump at its highest gain setting (no bass cut)
Same again but with gain fixed at 100% and the locus sweeping a few values.
The output stage forms a high-pass filter with the transformer - I think this is mainly what the transformer is adding to the mix. I'm sure it does a little bit more, but perhaps not a lot.
The first time I built one, I didn't have the correct value transformer, and the difference in inductance changed the low-frequency response too much (not enough bass in my case). I had to remove resistors to make it sound close to the original.
First of all thank you for this layout.
ReplyDeleteShort question: shouldn't the gain switch be a ON-OFF-ON SPDT Switch, as it has three gain stages?
Correct: The Peach edition had a three way switch. I normally use the two-way switch, as I it covers the full range of options and can easily be converted into a Dual Broadcast.
DeleteHi! thanks for the help with the Benson, this will be my next build, can you guide me a bit on how to change it to the dual version. According to what I think:
ReplyDelete- add a new A100k level pot (both same pinouts right?)
- change the switch for a 3PDT
- one pole to switch between levels jumping the output from the main 3pdt
- another pole for the gain switch (swith 3 unconnected?)
- last pole for led
Hello. If you search dual broadcast on the blog, you’ll find a point to point layout. Just follow the off board wiring and you’ll be fine.
ReplyDeleteThe dual uses 25k pots for volume. Basically the signal comes off the board and goes to both volume pots (pin 3 as per normal).
The second switch, switches between the two volume pots outputs (pin 2) - and it changes the gain from high to low at the same time - clever….
That p2p layout looks cool, i have never made a p2p FX maybe i'll give it a try, a regular perfboard is ok right?
DeleteHello.
DeleteCheck out my how to, if you haven’t done P2P before. It will be difficult, but it is satisfying when you finish.
I use perfboard without pads and physically join the component legs / wires together before soldering them.