MKB wrote:IMO what you are paying Fulltone for is the ears and knowledge to combine such tiny mojo effects together to make a superior whole.
DougH wrote:Here's a couple frequency plots of the "OCD" output stage in "HP" and "LP" mode to compare. I ran an AC simulation in SIMETRIX, swept from 10Hz to 20KHz, 3v peak input signal (with a 4.5v DC bias) into the output stage, fixed the tone control pot at 5k, left out the 56k to simplify, etc... R3 was changed from 33k for "HP" mode to 13.2k for "LP" mode to compare.
http://s14.photobucket.com/albums/a320/Doug_H/Analysis/
It does pretty much what I expected. The resistor reacts with the 47n tone control cap and in "HP" mode rolls off more highs. Yawn...
cbriere wrote:"Electronics WorkBench " for me,
i simulated the output circuit only .
top SW is OFF
bottom SW is ON.
http://i77.photobucket.com/albums/j69/c ... ircuit.jpg
I am in doubt of the retracing of the OCD?
as the switch is not doing LPF/HPF
what would be better is to put the 0.1u+20K circuit
in series to do HPF.
jg wrote:3V peak? meaning 6 V p-p? Into a circuit with a gain of ~3.8 powered by 9V? Hmmmmm.
I would have also expected shelving of the higher frequencies since there is no cap directly to ground but your sim doesn't show that......
DougH wrote:OK John.
Here are the new pictures with 1v input signal.
Not much difference...
http://s14.photobucket.com/albums/a320/Doug_H/Analysis/
DougH wrote:http://s14.photobucket.com/albums/a320/Doug_H/Analysis/?action=view¤t=ocd_output-graph2.gif
The upper set of curves is "LP" mode while the lower set is for "HP". Tone resistor settings are 1k, 5k, and 10k.
I realize Pspice has its limitations, but it can be useful for comparing before/after effects relative to ea other. I'm not trying to prove/disprove how "well-centered" or well voiced the circuit is. Just trying to show the effect of the LP/HP resistors.
After all these curves my point still stands. The "HP/LP" switch is just a variable low-pass filter. Nothing more- nothing less. Doesn't affect low freq response, etc, etc... In this case, pspice agrees with my original intuition anyway.
jg wrote:I thought the HP/LP stood for High Peak/Low Peak (of the tone control)? Did you think it stood for High Pass/Low Pass or something?
On the website http://www.fulltone.com/ocd.asp it describes the switch settings as "Low Peak" and "High Peak" in the descriptions of the sound clips. So maybe there was some confusion about what they meant by a number of people.DougH wrote:jg wrote:I thought the HP/LP stood for High Peak/Low Peak (of the tone control)? Did you think it stood for High Pass/Low Pass or something?
Hey, I have no idea what it stood for.![]()
Others in this thread mentioned a high pass filter effect.
But even if it does stand for high/low peak, it appears to be labeled backwards (according to the posted schem). I don't really care about the labeling though- wasn't addressing that.
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