Hanging Amps Off The Standard Symphony Head Unit

**robmawer** · 29-06-2003, 17:01

So, we finally got round to trying to fit the amps onto the back
of the standard head unit.

The amps to be used were a Pioneer 2x35W (RMS) unit, and
a Pioneer 2x80W (RMS) unit - not extemely powerful, but enough
to make the setup easier to hear. The lower power sub was due
to go on the back, the higher on the front (in accordance with
speaker quality).

I won't run into too much detail about the loom unless requested.
Basically, into the HU's line out a "yellow plug" to RCA adapter
was fitted. This was then connected to each amp, and the output
from each amp was then fed into an 8 pin ISO connecter, which
fitted into the speaker connecter originally plugged into the back
of the head unit.

During production, testing using the small amp revealed that
the amp had a weak right channel - worked a bit, faded, wiggling
it about brought it back before it died.

So then the line out was bridged such that the larger amp could
be used to power both front and rear. Worked a treat - played
about with volume, balance and gain. This revealed the front
wing mirror tweeters distorted way before any of the other
aftermarket units. Pulled these out, and the sound was spot on.

Putting it all together, the left channel died. Turned out to be a
loose connection. This rectified, the right channel went silent.
Nothing wrong with the wiring - test with a multimeter revealed
the right channel on the amp had gone! Bit more multimeter
testing on the line out revealed that the voltage varied from
high extremes, and far more than would be expected.

Result: two broken amps.

Conclusion: There might be something wrong with my particular
head unit. Testing this might be tricky, as if it is an issue with
the Symphony it will destroy the amp.
If it is a problem with all Symphony units, then the only way
to increase the power of the system is an aftermarket HU.

Thanks to Ian (Tavia4x4) and Paul (ffelan) for their efforts!

Rob.

redbaron · 29-06-2003, 17:37

no probs Rob,

hopefully we can have a more conclusive project next week.... I have just tried a std pioneer 2500 single cd with 4x45 amp... in lieu of the std symphony.... it does make a big difference although i quickly found the limits of my speakers... I think your infinity units might handle the power better.....

**robmawer** · 29-06-2003, 22:04

Well, what I was thinking was to get a head unit with RCA outputs on it. Seems to me most of
the manufacturers' are quoting peak not RMS, so even a 4x50 unit will only be 4x25 RMS - less than
the big amp's output when bridged. So if I get a head unit with outputs, I'd probably still whack the
amp on the back of it if Ian finds out what's wrong with it!

My only dilemma now is...new CD changer (and probably new wiring down the car), or get a head
unit that can play MP3 CDs. Or get a CD changer *and* a head unit that will read MP3 CDs...

Rob.

redbaron · 29-06-2003, 22:43

will lend u the spare pion cd that i was messing with....?
4x45 1x preouts changer controller?

**robmawer** · 29-06-2003, 23:07

I'm guessing that would need a Pioneer changer to work though?
Though I suppose, if we tested it all out and it worked, I could slip you a few
notes for it and then the changer could be tackled at a later date...?

And hey, I'd have something TVR in the Skoda then!

Rob.

redbaron · 30-06-2003, 08:57

sounds like a plan...

redbaron · 30-06-2003, 14:23

Rob,

found the cheap shop on the web...

was

www.cel-direct.com

pion changer @ 89

**robmawer** · 30-06-2003, 14:54

Hmm...thay also have a Pioneer MP3 head unit for £140!

What was the name of that audio shop in Bolton - Alpha Audio? Might try driving for a pricematch,
saves the hassle of mail order.

Rob.

redbaron · 30-06-2003, 14:59

bolton...

www.alphacaraudio.co.uk

or 01204 366 386

**robmawer** · 30-06-2003, 16:29

Cheers Paul - they seem reluctant to quote their prices on the web, so I hope that will work out in a good way!

Rob.

redbaron · 30-06-2003, 16:32

ive just ordered from cel... some alpine gear... let u know how it goes...

29-06-2003, 17:01	#1
robmawer Briskodian Join Date: Jan 2003 Location: Rochdale Posts: 12,418 Thanks: 2 Thanked 69 Times in 62 Posts	Hanging Amps Off The Standard Symphony Head Unit So, we finally got round to trying to fit the amps onto the back of the standard head unit. The amps to be used were a Pioneer 2x35W (RMS) unit, and a Pioneer 2x80W (RMS) unit - not extemely powerful, but enough to make the setup easier to hear. The lower power sub was due to go on the back, the higher on the front (in accordance with speaker quality). I won't run into too much detail about the loom unless requested. Basically, into the HU's line out a "yellow plug" to RCA adapter was fitted. This was then connected to each amp, and the output from each amp was then fed into an 8 pin ISO connecter, which fitted into the speaker connecter originally plugged into the back of the head unit. During production, testing using the small amp revealed that the amp had a weak right channel - worked a bit, faded, wiggling it about brought it back before it died. So then the line out was bridged such that the larger amp could be used to power both front and rear. Worked a treat - played about with volume, balance and gain. This revealed the front wing mirror tweeters distorted way before any of the other aftermarket units. Pulled these out, and the sound was spot on. Putting it all together, the left channel died. Turned out to be a loose connection. This rectified, the right channel went silent. Nothing wrong with the wiring - test with a multimeter revealed the right channel on the amp had gone! Bit more multimeter testing on the line out revealed that the voltage varied from high extremes, and far more than would be expected. Result: two broken amps. Conclusion: There might be something wrong with my particular head unit. Testing this might be tricky, as if it is an issue with the Symphony it will destroy the amp. If it is a problem with all Symphony units, then the only way to increase the power of the system is an aftermarket HU. Thanks to Ian (Tavia4x4) and Paul (ffelan) for their efforts! Rob.

29-06-2003, 17:37	#2
redbaron Briskodian Join Date: Jun 2003 Posts: 9,404 Thanks: 13 Thanked 64 Times in 56 Posts	no probs Rob, hopefully we can have a more conclusive project next week.... I have just tried a std pioneer 2500 single cd with 4x45 amp... in lieu of the std symphony.... it does make a big difference although i quickly found the limits of my speakers... I think your infinity units might handle the power better..... __________________ ________________________________________ Some times I just feel like smiling.

29-06-2003, 22:04	#3
robmawer Briskodian Join Date: Jan 2003 Location: Rochdale Posts: 12,418 Thanks: 2 Thanked 69 Times in 62 Posts	Well, what I was thinking was to get a head unit with RCA outputs on it. Seems to me most of the manufacturers' are quoting peak not RMS, so even a 4x50 unit will only be 4x25 RMS - less than the big amp's output when bridged. So if I get a head unit with outputs, I'd probably still whack the amp on the back of it if Ian finds out what's wrong with it! My only dilemma now is...new CD changer (and probably new wiring down the car), or get a head unit that can play MP3 CDs. Or get a CD changer and a head unit that will read MP3 CDs... Rob. __________________

29-06-2003, 22:43	#4
redbaron Briskodian Join Date: Jun 2003 Posts: 9,404 Thanks: 13 Thanked 64 Times in 56 Posts	will lend u the spare pion cd that i was messing with....? 4x45 1x preouts changer controller? __________________ ________________________________________ Some times I just feel like smiling.

29-06-2003, 23:07	#5
robmawer Briskodian Join Date: Jan 2003 Location: Rochdale Posts: 12,418 Thanks: 2 Thanked 69 Times in 62 Posts	I'm guessing that would need a Pioneer changer to work though? Though I suppose, if we tested it all out and it worked, I could slip you a few notes for it and then the changer could be tackled at a later date...? And hey, I'd have something TVR in the Skoda then! Rob. __________________

30-06-2003, 08:57	#6
redbaron Briskodian Join Date: Jun 2003 Posts: 9,404 Thanks: 13 Thanked 64 Times in 56 Posts	sounds like a plan... __________________ ________________________________________ Some times I just feel like smiling.

30-06-2003, 14:23	#7
redbaron Briskodian Join Date: Jun 2003 Posts: 9,404 Thanks: 13 Thanked 64 Times in 56 Posts	Rob, found the cheap shop on the web... was www.cel-direct.com pion changer @ 89 __________________ ________________________________________ Some times I just feel like smiling.

30-06-2003, 14:54	#8
robmawer Briskodian Join Date: Jan 2003 Location: Rochdale Posts: 12,418 Thanks: 2 Thanked 69 Times in 62 Posts	Hmm...thay also have a Pioneer MP3 head unit for £140! What was the name of that audio shop in Bolton - Alpha Audio? Might try driving for a pricematch, saves the hassle of mail order. Rob. __________________

30-06-2003, 14:59	#9
redbaron Briskodian Join Date: Jun 2003 Posts: 9,404 Thanks: 13 Thanked 64 Times in 56 Posts	bolton... www.alphacaraudio.co.uk or 01204 366 386 __________________ ________________________________________ Some times I just feel like smiling.

30-06-2003, 16:29	#10
robmawer Briskodian Join Date: Jan 2003 Location: Rochdale Posts: 12,418 Thanks: 2 Thanked 69 Times in 62 Posts	Cheers Paul - they seem reluctant to quote their prices on the web, so I hope that will work out in a good way! Rob. __________________

30-06-2003, 16:32	#11
redbaron Briskodian Join Date: Jun 2003 Posts: 9,404 Thanks: 13 Thanked 64 Times in 56 Posts	ive just ordered from cel... some alpine gear... let u know how it goes... __________________ ________________________________________ Some times I just feel like smiling.

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