EHX - Freedom Pre-Amp

Dr Tony Balls · Post by **Dr Tony Balls** » 29 Feb 2012, 14:46

Anyone know whats inside one of these?

Ive never heard of one and never seen a schematic. A person or two on the DAM forum seem to have them so im trying to get gut-shots of one.

Scruffie · Post by **Scruffie** » 29 Feb 2012, 15:18

I've got a schematic for the actual Amp I think but not the seperate Preamp, never knew it came like that.

Dr Tony Balls · Post by **Dr Tony Balls** » 29 Feb 2012, 15:38

I wonder how different the amp is, or if it is at all (preamp-wise, anyway)

uncleboko · Post by **uncleboko** » 29 Feb 2012, 16:04

I should think it's the same - the amp had tone and bite controls, also the Dirt Road Special amp

darthoverdrive · Post by **darthoverdrive** » 29 Feb 2012, 16:07

I found this. I love that layout.

http://www.effectsdatabase.com/model/eh/freedompreamp

Dr Tony Balls · Post by **Dr Tony Balls** » 29 Feb 2012, 16:20

found a bunch more of what looks to be the same unit here: http://stompboxes.co.uk/forum/viewtopic.php?f=6&t=11956

im starting a trace.

phibes · Post by **phibes** » 29 Feb 2012, 17:32

Trace it up!

Dr Tony Balls · Post by **Dr Tony Balls** » 29 Feb 2012, 18:31

Hrmm....im at kind of a loss here because of the trim pot on the solder side blocking a big chunk of the view. Anyone have any ideas? Here are my pics of where I am now. I'm assuing the IC is a dual op-amp.

front by thetonyballs, on Flickr

The schematic looks odd, too....not sure if its making sense

phibes · Post by **phibes** » 29 Feb 2012, 19:26

Yeah it'd be way easier if that guy could take pics closer to the trimmer. I'll look closer later.

I was guessing this thing would be similar to a Boss FA-1.

Dr Tony Balls · Post by **Dr Tony Balls** » 29 Feb 2012, 19:45

Also in that schematic fragment R10 and R7 are supposed to pots, and every line pointing down is a ground connection. DIYLC doesnt have those things, it seems.

Hides-His-Eyes · Post by **Hides-His-Eyes** » 29 Feb 2012, 19:55

You should be able to work out those last few connections based on the pinout of the op-amp. It needs to get power, and the signal goes towards inputs and away from outputs.

Duckman · Post by **Duckman** » 29 Feb 2012, 20:23

I'm not 100% sure, but in this picture, looks like there's nothing connected to pin4 and pin8 and both 4k7 resistors goes to pin7 and 10k goes to pin6, maybe pin5, too.

Dr Tony Balls · Post by **Dr Tony Balls** » 29 Feb 2012, 20:33

Duckman wrote:I'm not 100% sure, but in this picture, looks like there's nothing connected to pin4 and pin8

I think those go to ground and +V, respectively, but the trace is underneath the IC.

Duckman · Post by **Duckman** » 29 Feb 2012, 21:11

Dr Tony Balls wrote:
Duckman wrote:I'm not 100% sure, but in this picture, looks like there's nothing connected to pin4 and pin8
I think those go to ground and +V, respectively, but the trace is underneath the IC.

Right

Pin4 goes to the black wire, presumable ground

Surely, the trace between legs, from the down side, to the 47k resistor in the 5087 emmiter carries power from pin8.

Duckman wrote:both 4k7 resistors goes to pin7

Wrong. Just one does.

Dr Tony Balls · Post by **Dr Tony Balls** » 29 Feb 2012, 21:15

I believe the black wire it actually +V. Theres that large pad just above the IC that should be ground, and it doesnt appear to connect to it.

Duckman · Post by **Duckman** » 29 Feb 2012, 21:53

Mmmm... We're preassuming that's a dual OA... and we got a 5087 PNP device... I'm confused about V+ and V- right now

analogguru · Post by **analogguru** » 29 Feb 2012, 23:03

Where do you see a problem ?

: Electro-Harmonix Freedom Pre-Amp schema

Quod erat demonstrandum,

analogguru

Duckman · Post by **Duckman** » 01 Mar 2012, 00:17

analogguru wrote:Where do you see a problem ?

Apart of my noobness? The time you take to post it

I didn't see a problem, just was confused

Sciens minus potest cognoscere

phibes · Post by **phibes** » 01 Mar 2012, 04:52

uncleboko · Post by **uncleboko** » 01 Mar 2012, 09:16

"Quod erat demonstrandum"

Et Dirtus Roadus Specialus est

EHX - Freedom Pre-Amp [schematic]