mcpigeon Posted March 20, 2012 Share Posted March 20, 2012 Thanks utc_pyro! Yeah- I was referring to what happens when you hold down the Audio button. I'm trying to figure out which OEM solution to get, and I've come to the conclusion that all of them (Cleansweep, H660, MS-8) all suffer from having to use their volume controls to maintain a consistent EQ output. It looks like after doing this mod, you can pretty much use any of them without worry that the equalization will will be thrown way off at different volume levels. Right now I'm leaning heavily towards the H660 since it can be found for about the same price as the Cleansweep and includes time alignment and can be used for an active front stage. Link to comment Share on other sites More sharing options...
BigTDogg MA Posted May 1, 2012 Share Posted May 1, 2012 So I forget, RCAs are center positive, right? Does this still allow for tone controls? Just eliminates the factory volume filter, right? Lastly, doing this mod would eliminate the "need" for a MS-8, correct? Link to comment Share on other sites More sharing options...
ean611 Posted May 1, 2012 Share Posted May 1, 2012 So I forget, RCAs are center positive, right? Does this still allow for tone controls? Just eliminates the factory volume filter, right? Lastly, doing this mod would eliminate the "need" for a MS-8, correct? Center positive yes. Tone controls yes. The only thing this kills is loudness. This does NOT kill the need for an MS-8, as an MS-8 will do tons of equalization that will make the car stereo sound much better than without. That being said, the output of the radio with this mod is pretty linear. Your car on the other hand, is NOT, and EQ's are a very good thing. Link to comment Share on other sites More sharing options...
BigTDogg MA Posted May 1, 2012 Share Posted May 1, 2012 Yeah, so this is a better starting point for the MS-8 then, right? BTW, do you work at Bose? Or have you ever? Link to comment Share on other sites More sharing options...
ean611 Posted May 1, 2012 Share Posted May 1, 2012 Yeah, so this is a better starting point for the MS-8 then, right? BTW, do you work at Bose? Or have you ever? No, I have not worked at Bose. Why do you ask? It would be better to do this prior to using an MS-8, 3Sixty.2, or Audison Bit1. Link to comment Share on other sites More sharing options...
BigTDogg MA Posted May 1, 2012 Share Posted May 1, 2012 You seem like an audio guy, and you're in Framingham. I fail at amateur sleuthing Link to comment Share on other sites More sharing options...
TehRicer Posted October 31, 2012 Share Posted October 31, 2012 Thanks for the walk through! What exact voltage were you getting off points C201, C207, C301, and C307? Link to comment Share on other sites More sharing options...
utc_pyro Posted November 1, 2012 Author Share Posted November 1, 2012 Never actually checked the voltage at the caps... Just the output. Theoretically you should see about 4vdc, but I've never tested it. If you're refering to the ouput post mod, just below 2v unless you did something odd with the settings (33 vol, bass +6). The volume controll IC is fed with 8vdc, so presuming it's not a rail to rail output design the theoretical max is around 2.1-2.3v. Link to comment Share on other sites More sharing options...
TehRicer Posted November 2, 2012 Share Posted November 2, 2012 Never actually checked the voltage at the caps... Just the output. Theoretically you should see about 4vdc, but I've never tested it. If you're refering to the ouput post mod, just below 2v unless you did something odd with the settings (33 vol, bass +6). The volume controll IC is fed with 8vdc, so presuming it's not a rail to rail output design the theoretical max is around 2.1-2.3v. Thanks, Yeah I was curious. My miniDSP accepts both .9V & I can switch a set of jumpers so it can be fed up to 2V Just maybeeeeeeeeeeeeeeeeeee, I wouldn't need a LOC lol Link to comment Share on other sites More sharing options...
TehRicer Posted November 23, 2012 Share Posted November 23, 2012 Is there any reason you didn't bypass the OEM H/U amplifier? Link to comment Share on other sites More sharing options...
utc_pyro Posted December 3, 2012 Author Share Posted December 3, 2012 It is bypassed? Look at the circuit diagrams earlyer in this thread. We tap in right after the volume control, before the factory EQ and amp. There really isnt a reason to disable it if that's what you're asking. Might as well leave it running incase I have to sell the car in a hurry and want to put stock speakers back in. Link to comment Share on other sites More sharing options...
LightFantastic Posted October 12, 2014 Share Posted October 12, 2014 Anyone know if this modification will work on the P-201UH models? Link to comment Share on other sites More sharing options...
Canon20D Posted October 12, 2014 Share Posted October 12, 2014 should be all the same. Your just hijacking the audio lines before they get to the built in amp that corrects higher volume bass adjustment. If you need a HU to work on, mines for sale. Link to comment Share on other sites More sharing options...
LightFantastic Posted October 12, 2014 Share Posted October 12, 2014 I just pulled my P-201UH out. Totally different layout. In fact, I can't even find the capacitors the OP listed. They are non-existent on here. Anyone wanna do a P-201UH mod? I won't have access to a scope til' spring semester. They only let "juniors and above" in the lab, lmao. lmao Link to comment Share on other sites More sharing options...
SVXdc Posted October 13, 2014 Share Posted October 13, 2014 P-201UH (Matsushita CQ-EF1461L) service manual PDF Link to comment Share on other sites More sharing options...
LightFantastic Posted October 14, 2014 Share Posted October 14, 2014 Workin on it:) I posted a thread on the physics forums. Will post up when we get it. U have a link to the p204uh so we can compare. Thnks Link to comment Share on other sites More sharing options...
Leviman Posted October 21, 2014 Share Posted October 21, 2014 I'd love to see work on the older radio as well! Just bought an '05 OBXT and I need to get my audio up to par. I think with some good door speakers and a small sub the deck would sound good with the weird EQ disabled. Link to comment Share on other sites More sharing options...
snm95ls Posted November 23, 2014 Share Posted November 23, 2014 Sucessfully completed addition of line level outputs on a 2006 P-203UH. The sound quality is pretty damn decent right out of IC206 which is the fader and volume control chip. Soldering to the tiny SMT pads is quite the trick. Now I think I just might have to snag a P-204UH for a nice OEM aux input. FWIW, you really need a line driver for this to work well. I can get my old XTANT 404m to work, but only at one input sensitivity jumper setting. I am guessing there might be something funky between the output from the IC206 and the amplifier. I'll have to dig into that if I can. I also removed R237, R238, R239, and R240 in an attempt to gain slightly better channel separation. I'll never use the OEM sub output anyway. Link to comment Share on other sites More sharing options...
utc_pyro Posted December 5, 2014 Author Share Posted December 5, 2014 I'm running a line driver in my setup, but it was working successfully without it on the old radio. I actually have the gain only cracked open so it dosent clip my MS-8. Ony real downside of using it straight is massive turn-on/turn-off pop. Link to comment Share on other sites More sharing options...
snm95ls Posted December 7, 2014 Share Posted December 7, 2014 I'm running a line driver in my setup, but it was working successfully without it on the old radio. I actually have the gain only cracked open so it dosent clip my MS-8. Ony real downside of using it straight is massive turn-on/turn-off pop. I didn't have any issues with the on/off pop after the unit was powered up for the first time after being disconnected from power. I have been trying to figure out the very audible noise when the HVAC is connected. Just paid for a P-204UH which seems to be a lot easier to modify to begin with and I will finally have the option for a decent AUX input. Link to comment Share on other sites More sharing options...
utc_pyro Posted December 17, 2014 Author Share Posted December 17, 2014 Sound from the radio or your speakers? With the HVAC plugged in my radio makes a pretty loud buzzing sound, but all three have done so. Output from the volume control IC has always been fairly clean with just some faint white noise. Link to comment Share on other sites More sharing options...
snm95ls Posted December 17, 2014 Share Posted December 17, 2014 Sound from the radio or your speakers? With the HVAC plugged in my radio makes a pretty loud buzzing sound, but all three have done so. Output from the volume control IC has always been fairly clean with just some faint white noise. The noise is quite evident through the speakers with my modified P203-UH. It could be my lackluster soldering skills with SMT board architecture. The unmodified P204-UH has quite a lot of noise during track selection in CD mode. Kind of annoying/disappointing considering it seems like a noticeable upgrade from the P203-UH in just about every other way. Link to comment Share on other sites More sharing options...
technicalgarage Posted March 23, 2015 Share Posted March 23, 2015 Just did the loudness kill and line out to my 204uh. Don't have an amp but when I plug in some random unpowered speaker with an rca on the end, I get a loud pop and it kills speaker output. removing restores speaker output. I'm getting ready for an amp install and wanted to make sure my wiring is ok. can anybody confirm that this is normal behavior? Link to comment Share on other sites More sharing options...
utc_pyro Posted July 13, 2015 Author Share Posted July 13, 2015 This is super late, but yes that would be normal. The driver circuit that we pick up on cant really handle a speaker, unless it's one of those piezo deals for a crystal radio. Link to comment Share on other sites More sharing options...
utc_pyro Posted March 4, 2016 Author Share Posted March 4, 2016 Hey, Just wanted to let everyone know: The P-206UHB head unit is a MUCH better choice for aftermarket audio. The EQ step after the volume control chip is completely gone and the SRSWOW chip before that has been bypassed as well. The other head units tended to roll the bass off around 60hz on the output stage and had a bunch of crazy notch filters. The SRS chip seemed to cause some signal clipping issues as well. Output stage is a TA8264AHQ, a particularly low THD low noise version of the power amp used in the other radios. It should generate a balanced 6.32 rms max signal with 34db of gain. There appears to be a voltage divider between the volume control chip in the amp, but I don't see any additional signal processing. It's perfectly capable of driving normal speakers (~18WRMS at 1%THD) or acting as a balanced line driver (how harman used it). Loudness stuff is still there if you want to bypass it. You can still use the built in amp even with it bypassed though. Internal Pictures Here The ground point used my instructions isnt actually an audio ground, thus causing all sorts of fun issues with noise. As part of a system rework in my car I'm putting in one of these and running the high level input on my MS8 instead. Edit: Testing results=> Unit puts out 8vrms unloaded (should be about this into a 10K load or 120ohm MS8 load). It WILL clip at "39" on the dial. 38 and below is 100% clean. There are white noise issues like on the other units:mad: Link to comment Share on other sites More sharing options...
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