[omishra]

Originally Posted by noidaboy

Congrats for the efforts and the success,this is an astounding DIY.

The tech specs went over my head as well,but in lay man's language,Did you fiddle with the internal amp of the system?

Thanks.
Yes, I fiddle with internal amp of OEM HU, removed that chip

Originally Posted by navin

I'm a big fan of OP275s. Try them instead.

That is exact I wanted, but unable to source it from local market. Anyway I will be looking for the same and DIP-8 pins match 1-1. So no issue to replace that in this socket itself. Thanks

Originally Posted by navin

why go PWM at all. How much power (in db) are you gaining?

If you choose your speakers carefully you might be able to get the same SPL with a class AB amp.

In dB I can not tell, but it was RMS which I wanted.

I already have my own built class AB MOSFET amp and PWM amp in house. The time I started to look for solution to be inside OEM HU, heatsink requirements and footprint were only issue in my mind. But anyway now after looking inside HU you can mount it outside HU only. Still I already went ahead with class-T because its upgraded PWM not a normal switching AMP. Also my previous listening experience was good with this kind of amp. Beside standby/awake control and low standby current, here I was able to avoid relay as switches.

Originally Posted by mjothi

Awesome. I was thinking so much to do DIY just for the 2 rear speakers and here you are doing complete upgrade on the OEM HU

And you designed everything yourself. Thats something great. Congrats.

Thanks! I also keep learning new thing but never forget my basics.

Originally Posted by greenhorn

+1 to navin's suggestion
From the datasheet. I'd recommend AM mode since you're running off 14.4V anyway (PWM mode makes a difference only for higher voltages), and the THD+N figures are lower for AM mode as well

If you remember, I already put a control to switch AM and switched mode. here for radio there is no issue as I am using in AM of AMP. I took out "CD logic" (some green/yellow wire) out from HU for this mode switchover purpose.

Issue was for CD play back. And anyway if possible why to do compromise?

[omishra]

It is time to do some cleanup job. I verified this system and tested for almost last 3 weeks. Some professional touch was required.

1. To add the pre-amp section in a new box and integrate everything together. Big heatsink also added though not required at all. It's just cold after playing 1 hr.



2. OP-AMP based preamplifier refused to work cleanly and was picking hum in car. So LM 317 based regulated power supply of 9 volt derived which you can see fixed hanging at leftside of PCB. In right side lower corner you can see ferrite coil I added in powerline.

Input, output and power wires are at different corners of the box.



3. Output and power and logic terminals ->

• upper lane is output of this amp.
• below from left MUTE, ANOLOG/SWITCHED MODE. After that the left one marked red is from key switch to awake amp. This is new thing. In previous config Amp was drawing ~200mA standby current though key was removed. Now it made to SLEEP with 200uA (micro ampere) and awake with input when key is inserted and HU is turned on.
• Next pin is unsued, followed by power ground and main 12V/10A power line.

One more pic ->



4. Inputs are standard RCA with no contact between box and ground of RCA. This is because I wanted signal ground to be separately maintained with ferrite bead in between power ground at main amp.

No part /circuit is grounded to box - box will be grounded to HU by screws and metal strip which holds it.



5. HU looks neat and clean, ready for fitment. Wire terminals are soldered at wires of 18SWG. I will be be using more than 20Watts per channel. So satisfied with this. Again I am using OEM harness so can not torture it. No more power required for my listening tastes.



6. Sitting on the back of HU ( below HU actually, I have toppled it for fitting).





7. Final assembly -






Result - Along with increased sound level, I got Alternator whine as a free gift with added hiss, thanks to preamp sensitivity.

Fix-

1. First separated all pre-amp grounds and RCA wires.
2. Power Amp is OK only culprit was one RCA ipnut which was touching its ground to metal box and bringing in whine. Just separated it.
3. Made sure that preAmp ground is coming from HU preout ground and AGND of AMP which is separate than power ground.
4. Blue RCA cable is nonsense stuff as its shielding is low quality aluminium foil which is brreaking as well as not grounded at all. I just left it there rafter grounding that foil. Still some engine whine is there. I need to get get good cable or prepare new home brewed sheilded cable. Other components are cleared for this issue.Because after grounding - resistance of that foil in 12 inch cable is ~20ohms. My any normal wire has 0.6ohms including DMM terminals has 0.5 ohms in it. So this needs to be changed with better one.

Now about HU after putting preamp -

1. Better S/N between volume level 15-40. Below 15 its hiss and above 40 I could not test as it was already deafening sound level in parking.
2. For CD some tracks are clear some are played with so called residual noise. So this noise is not from my added parts.
3. Bass is there and OEM speakers playing it.

To sum up , these HU noise can not be detected unless gap between tracks in CD. I tested with other small AMP too. CD player has it and tuner is clear.

Request - Please suggest me some good and properly shielded RCA cable. That blue input cable part I need to replace.

On next Pune t-bhp meet, I would like you to listen and give your feedback. Till that time I am holding my plans for OEM speaker upgrade and damping.

My new amp is clear and loud. That's all from me. Now I would like to listen this.

[navin]

Originally Posted by omishra

Request - Please suggest me some good and properly shielded RCA cable. That blue input cable part I need to replace.

Try Supra or if on a budget Sommer.

[gigy]

Very nice diy. You do have a great amount of patience.

[DerAlte]

Originally Posted by omishra

...
4. Inputs are standard RCA with no contact between box and ground of RCA. This is because I wanted signal ground to be separately maintained with ferrite bead in between power ground at main amp.

No part /circuit is grounded to box - box will be grounded to HU by screws and metal strip which holds it.
...

Ati uttam hasta-shilpa karya, Mishra-ji, dekh ke chitta prasanna ho gaya!!!

Not to rain on your party, but... IMHO you should review your policy of not using the box as the single reference for both signal and power. No wonder you opamps are seeing ghosts - to protect against induced EMI, you will then need another shield tied to vehicle ground.

6-side-shielding is a wise policy for getting rid of the pesky stuff.

[omishra]

Navin, gigy and DerAlte: Thanks

Originally Posted by navin

Try Supra or if on a budget Sommer.

Navin, I can see these Supra are really great cables. Can you/anybody suggest where I can buy these in Pune. And what could be price for 1.5 meters approx.

Originally Posted by gigy

Very nice diy. You do have a great amount of patience.

Originally Posted by DerAlte

Ati uttam hasta-shilpa karya, Mishra-ji, dekh ke chitta prasanna ho gaya!!!

Not to rain on your party, but... IMHO you should review your policy of not using the box as the single reference for both signal and power. No wonder you opamps are seeing ghosts - to protect against induced EMI, you will then need another shield tied to vehicle ground.

6-side-shielding is a wise policy for getting rid of the pesky stuff.

DerAlte, 6-side-shielding is already there. Box has same ground as HU metal shell. Even HU has same policy of keeping audio ground separated from power ground.
This whine is listened at volume level 1-5 ( total max is 45). It remains there const at idle rpm and does not increase with volume level. Once car moves it vanishes with turning into whistle and gone. What to say. Isn't input RCA picking this?
Normally I listen at 15+ level. Nobody other than me can recognize whine and differenciate from cabin noise. But I don't have that 100% silent.

[omishra]

I would like to thanks everybody for their support
now,

All below noises are gone now!

Hiss - this is taken care by reducing the input to my amp about 1/3 of output of HU - DAC output. At level 1 I can here only audio no hiss and at Max 50 now I reach upto amp saturation and distortion at very high SPL.

Whine - Aha! This was quite interesting problem. I got to know it from two angles. There was no ground loops.
1. Input cable replaced with another good shielded local cable and kept away from power lines. <- main part
2. Power and ground wires are replaced with 5mm thick multistrand Finolex cables. Additionally I put three tantalum capacitors in all power inputs of OEM HU (two X 1,uf/35V ) and one X 10,uf/35V for my amp power input.

Now I have audio with dark background, dead silence and clean audio, even tuner reception improved too.

Regards,

[ImmortalZ]

Just read through the entire thread.

Being an electronics hobbyist since I was in high school, your worklog was very enlightening and a delight to read through.

'gratz on the work! Truly an inspiration to every audio DIYer here

[techn0l0gist]

Originally Posted by omishra

Thanks.
That is exact I wanted, but unable to source it from local market. Anyway I will be looking for the same and DIP-8 pins match 1-1. So no issue to replace that in this socket itself. Thanks

Wonderful DIY job there ! In case you'd really want the OPA275, I guess they're available at rsindia www.rsindia.com cost is Rs 295 for single quantities.

Cheers,

Amit

P.S. I am not associated with rsindia , just recommended them as i find them convenient and they have good service

[navin]

Originally Posted by omishra

Navin, I can see these Supra are really great cables. Can you/anybody suggest where I can buy these in Pune. And what could be price for 1.5 meters approx.

PM B&T he can arrange for them.

[omishra]

Originally Posted by techn0l0gist

Wonderful DIY job there ! In case you'd really want the OPA275, I guess they're available at rsindia www.rsindia.com cost is Rs 295 for single quantities.

Thanks Amit, I think that's OP275 (not OPA275) you are talking about and its priced for 1 STK=100 pieces for Rs 295

Originally Posted by navin

PM B&T he can arrange for them.

Done Sir

[Ramsagar]

OOps.I missed this thread for a long time,let me iterate it once again.
OMG you have done a great job mishrajii on the stock HU.
can we add a USB support for a normal pioneer-6950ib player.Hell with using CD's.
we cant control the volume & tracks from the HU wen ipod is connected to AUX.

Else need to change my player only for USB.This would be helpful for other members also to follow.

[omishra]

Originally Posted by Ramsagar

OOps.I missed this thread for a long time,let me iterate it once again.
OMG you have done a great job mishrajii on the stock HU.
can we add a USB support for a normal pioneer-6950ib player.Hell with using CD's.
we cant control the volume & tracks from the HU wen ipod is connected to AUX.

Else need to change my player only for USB.This would be helpful for other members also to follow.

Hi, Thanks for your appreciation.

Regarding USB support - I never thought to add any feature unsupported by OEM. As far as enhancement goes, its easy.

Anyway I started thinking over it. It may be matter of ample free time (Q: When? A: God knows only)

[sdh]

What is that torroid next to the amp9 power connectors. I do not have it in the kit I got. Can you share the purpose and spec of the same.

[ghpk]

Mishra ji,
How good are the Luxco Speakers ?
I see them in first page, and I think those are made in my town,
Do they compete with Those Branded Speakers in ICE market ?