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EHX Freedom Preamp schematic?

Posted: Thu Jul 12, 2018 7:00 pm
by n-eight_Archive
bassdriver wrote:to me the "bite" cuircuit looks like a bandpass filter, so it will not have much effect on the distortion. maybe Nate or Dr Balls could enlighten us?The bite pot is in a parallel feedback loop of the last gain stage, so it's will have an effect on the gain of that stage. I haven't scoped or simulated it, but it may be able to drive the opamp into clipping.

EHX Freedom Preamp schematic?

Posted: Thu Jul 12, 2018 7:00 pm
by the finger genius_Archive
Yes, I think that's what's happening - is there a way to increase the amount of feedback / gain here by changing some values?

EHX Freedom Preamp schematic?

Posted: Fri Jul 13, 2018 7:00 pm
by bassdriver_Archive
I watched 2 Mike Matthews Freedom Amp Demos on youTube and also found a quote on the EHX forum saying that the bite pot is actually a mid boost. In both videos the amp was rather clean sounding btw. Since I didn t have the original PNP transistor this could vary a bit, but on my breadboarded circuit the sweet spot for the trimpot is somewhere between 500 ohms and 1K. This let s me use the volume pot to blend from clean to heavy distortion. If the signal breaks up just slightly then one can use the mid boost to get a little more overdrive.I think I would add a volume control at the output if using the circuit as a pedal as it has a very high output when heavily overdriven.

EHX Freedom Preamp schematic?

Posted: Sat Jul 14, 2018 7:00 pm
by bassdriver_Archive
I finally read through the entire thread as I got the feeling that I m missing the point. Finger genius, since you own a dirt road special, what does the bite pot do on your amp. And, are we talking about a clean preamp pedal or would you like to use it as an overdrive/distortion pedal? After watching those freedom amp demo videos I m not sure if the preamp is actually supposed to clip at all.

EHX Freedom Preamp schematic?

Posted: Sat Jul 14, 2018 7:00 pm
by bassdriver_Archive
Ok. I tried the following on my breadboard: remove all parts from that bite circuit (the 2 10nF caps, the 22nF cap, the 2 4k7 and the 2k2 resistor) except for the trimpot. Now the bite pot can be used as pure gain pot for that stage. I actually used a 500k pot there. That worked fine on my breadboard. Now I m actually able to blend from clean to overdriven via the bite pot. Still the trimpot has to be set pretty low as it defines the gain of the stage together with resistance of the bite pot.Hope that helps.

EHX Freedom Preamp schematic?

Posted: Sat Jul 14, 2018 7:00 pm
by the finger genius_Archive
I'm looking for a something that I can use as a clean preamp (I run into an old Altec power amp) and also can dial up some dirt. On my DRS the bite definitely drives it into clipping, which is what I am hoping for - the pedal form seems to be doing something similar for me, I'm just wondering what I might try to have the bite knob drive it a bit further.

EHX Freedom Preamp schematic?

Posted: Sat Jul 14, 2018 7:00 pm
by the finger genius_Archive
Hey, I got everything working! Bite pot definitely does seem to boost the mids, can be into distortion. I think one issue was just that I was working with a crappy tiny breadboard and there may have been some bad connection problems. One other issue is the 4.7K resistors I ordered turned out to be 2.7K resistors and I had a hard time measuring them with my old analog radioshack voltmeter - when I changed the values out on these the bite knob boost definitely increased. Thanks for everyone's help! I will try out your suggestion as I think having an overall boost might be a more useful sound there.

EHX Freedom Preamp schematic?

Posted: Sun Jul 15, 2018 7:00 pm
by J Burns_Archive
Store by my has a Dirt Road Special for three bills. Can't justify it with vet bills and mechanic bills but oh lord am I tempted.

EHX Freedom Preamp schematic?

Posted: Sun Jul 15, 2018 7:00 pm
by n-eight_Archive
That DRS I posted recently is still up on Reverb for ~$250 shipped: https://reverb.com/item/12297952-electr ... ial-1970-s

EHX Freedom Preamp schematic?

Posted: Wed Jul 17, 2019 7:00 pm
by Dr Tony Balls_Archive
tallchris wrote:GUYShttps://reverb.com/news/ehx-remakes-its ... snamm-20191) They will fundamentally alter it somehow2) I'm sure it comes with the *legendary* build quality of modern EHX