hey luke,
found this today with a google search, and thought it might help. old Dat-Heads post. This guy might be able to help, if you can track him down. If you can find a schematic, or come up with any cool mods, please share!!!!
From: Hawker <Hawker@Connriver.net>
Subject: DA-P1 mods and upgrades
Date: Fri, 05 Nov 1999 11:21:32 -0500
Howdy all.
I have been perusing over the DA-P1 schematic and it looks VERY ripe for mods, improvements etc. I was wondering if anyone here has played with this b4 and am interested in some feedback. Since I no longer have regular access to an AP1 (Audio Precision System 1) I have no way
to PROVE that my mods make a difference other than my ear. So I am looking for thoughts on where to focus my energy.
I have already made some mic-pre gain structure mods with good results.
Wondering if anyone else has mad any other mods and with what results.
Areas I see for mods,
General Audio Mods
1) add the missing .1uF Bypass caps,
2) Change Electrolytics to Tantalum caps,
3) increase size/quality of DC coupling caps,
4) change Ru02 0805 resistors with Mini-Melf (like Apogee uses).
5) Upgrade NJM2115 op-amps (Any ideas what has enough headroom to use here, can't us a OPA2604, OPA2134, NE5532, NJM 2114 etc here)
Some of the bypass caps shown on the schematic are not actually on the PCB (cost reasons?), add those back in.
Ideas to Improve 48V and -5V switching regulator,
1) substitute RC filters with LC filters,
2) Add snubber caps/resisters
3) Linear Post Regulation?
4) add the missing .1uF Bypass caps,
5) Change Electrolytics to Tantalum caps.
6) Upgrade the ADC (Anyone got data on a AK5340 it was not a US AKM release)
Mic Pre ideas
1) Add complementary Pairs to the Transistors on the mic pre,
2) Add better constant current source
3) Change Volume control to change gain of stage rather than attenuate
4) Of course change the gain level of the first stage to be more what we really need (lower).