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DIY Stompboxes => Building your own stompbox => Topic started by: Paul Marossy on June 30, 2012, 12:54:44 PM

Title: Schematic for the MXR Dynacomp Rev. F?
Post by: Paul Marossy on June 30, 2012, 12:54:44 PM
Anyone have a schematic for the MXR Dynacomp Rev. F?

Rev F uses an LM13700 dual OTA instead of the CA3080. I'm wondering what changes may have been done to the the circuit with that change. Rev F seems to be sound just a little diffenent than the Rev E version.
Title: Re: Schematic for the MXR Dynacomp Rev. F?
Post by: Nocaster Cat on June 30, 2012, 03:07:37 PM
I've heard that the LM13600 is a couple of 3080's in a single package, could be wrong though.
Title: Re: Schematic for the MXR Dynacomp Rev. F?
Post by: Mark Hammer on June 30, 2012, 03:35:03 PM
You're close.  It contains two transconductance amplifiers (which the 3080 is) but is a slightly different design internally, and has better specs.  A bit like saying a TL072 is a pair of 741s: they're both op-amps, true, but not quite the same performance as op-amps.

The 3080 has ceased production, AFAIK, so as the supply dwindles down, many manufacturers have switched to the LM13600 and LM13700.  The same is true of the CA3094 (also a single OTA, but with an added output stage).
Title: Re: Schematic for the MXR Dynacomp Rev. F?
Post by: Paul Marossy on July 01, 2012, 07:06:05 PM
So what do they do with the 2nd stage? Just leave it unconnected? I guess I could look at it and figure it out.
Title: Re: Schematic for the MXR Dynacomp Rev. F?
Post by: Nocaster Cat on July 01, 2012, 08:12:23 PM
Quote from: Paul Marossy on July 01, 2012, 07:06:05 PM
So what do they do with the 2nd stage? Just leave it unconnected? I guess I could look at it and figure it out.

I believe so.
Title: Re: Schematic for the MXR Dynacomp Rev. F?
Post by: SISKO on July 01, 2012, 09:02:46 PM
Something like this? http://tonepad.com/getFileInfo.asp?id=121
Title: Re: Schematic for the MXR Dynacomp Rev. F?
Post by: Paul Marossy on July 02, 2012, 01:12:22 PM
I guess the Rev F version shouldn't sound different than the Rev E version, but they seem a little different to me.  :icon_confused:

I modded the Rev E version for someone recently and it seemed to have more "sizzle" with the sensitivity maxxed and it seemed to decay into feedback better than my Rev F that I picked up cheap the other day. That's what made me wonder if a CA3080 and 1/2 of an LM13700 are really the same thing. They seem slightly different to me...