Any DIY attempt on HU?

[HiFiManish]

Hi,
I have sony CD xGT460 US as head unit (HU) in my car. For some time I am thinking to add an amp in the car. The HU has only a sub-out, so obvious choice is to upgrade the HU first with some more pre outs having HU.

However I want to check whether we can do some DIY attemt in current HU to get 2 or 4 channel pre amp level connections!!! So I am writing here for some guidance and to start with following queries:

1. Has anyone attempted any sort of DIY on HU circuits?
2. Ant idea on how easy or difficult the circuits would be? I mean would it be possible to identify preamp and power amp separately? or is it single IC based? I have not searched it till now and writing here directly!
3. My expectation is that I should be able to simply tap out wires between pre amp and power amp stage. Let's say I identified this point, then will it need some extra circuit components to make pre amp signal usable outside?
4. Approching any professional technician is my second last option. Please do let me know any such technician in Bangalore.

By above questions I am trying to see if it will be worth spending resources!! Further if I get guidance from someone who has already done it, then nothing like it!!

Hope its not a completely crazy idea!!

Your guidance, thoughts and ideas are most welcome.

Regards,

 

[greenhorn]

you do know that installing a convertor, or using an amp with high level inputs is far easier, right?

 

[HiFiManish]

you do know that installing a convertor, or using an amp with high level inputs is far easier, right?

Thats right Greenhorn, however before budgeting for the same, had wanted to explore DIY option. Thanks!

 

[omishra]

I have done small amp addition to my car few years back. See here -

SX4 OEM HU: By pass surgery for Amp section - Team-BHP

Don't miss the later stages of mod where I have redone the things.

 

[sarith]

I have done small amp addition to my car few years back.

A neat job:thumbsup:

wanted to explore DIY option. Thanks!

A 12VDC to +/-30VDC converter can be used for a diy amp. I've seen converters upto +/-60VDC.

 

[karthi1000]

I have done small amp addition to my car few years back. See here -

SX4 OEM HU: By pass surgery for Amp section - Team-BHP

Don't miss the later stages of mod where I have redone the things.

:clapping: :clapping:

 

[HiFiManish]

I have done small amp addition to my car few years back. See here -

SX4 OEM HU: By pass surgery for Amp section - Team-BHP

Don't miss the later stages of mod where I have redone the things.

Wow...This is great!!!:clapping: would take some time to read and understand entire thread...Thanks !!

 

[HiFiManish]

@Greenhorn: My apologies! Before reading the team-bhp post, I had no clue of OLT. I assumed you were talking about amp only!! Pardon my ignorance.

@omishra: Gone through the complete thread...and understood that in medical parlance it is really a bypass surgery!!...while my knowledge was limited to medicine for common cold!

Key pointers for me, out of that thread are following:

Post no. 7: You wrote - pre amp level won't give complete details. Also the picture shows your HU has 2 channel RCA out. Question: So at what amplification level, HUs tap RCA level output?

Post no. 7: You wrote - That's why I avoided preout and trapped the audio signal at the source, just at the output of DAC(+Volume control). Question: My HU has AUX input as well. At which part of amplification stage this will go in HU?

Post no. 21 & 22: Output from DAC directly won't be useful without pre amp, as the cables need to run for few feet. Question: Does it mean my idea of tapping wires from pre amp out for RCA output is not 'practical'?

Post no. 29: Op - amp may be a necessity in my plan! It is also mentioned that it is used for some sort of buffering. Question: For tapping RCA out, do I need to put an op-amp as well?

Post no 41: noise reason is clock frequency mismatch. I read it as: here goes off my naive plans! :-(

Post no 73: You are recommending LOC. Question: I did some search on net. Though it is said, there are no SQ loss with LOC, but just wondering that LOC input will be amplified signals, which would include all the noise etc, introduced due to various reasons and from various sources in HU curcuits. So compared to RCA out, how good or bad will LOC output be?

Thanks,

 

[greenhorn]

@Greenhorn: My apologies! Before reading the team-bhp post, I had no clue of OLT. I assumed you were talking about amp only!! Pardon my ignorance.

Didn't understand this part

There will be a loss with an LOC, because you are taking the signal out from the power amp output, which would have slightly more distortion and noise than a line level output, but for most people, and in a car, this should not be a big deal.

 

[HiFiManish]

Hello,
I did some research and found following three amps, which have speaker level input as well.

Ground Zero gzia 411 hpx
Blaupunkt ema 455
JBL gt a644si

So with any of these, I won't need LOC. I want to choose on sound quality. I am afraid sound should not be too bright as this is what I have seen in some of other ICEs. I did not find much qualitative reviews on net. Also searched local shops for demo, bur no luck with any of above models.

If anyone has listening experiance of above, please let me know.
Thanks.