I have the original head unit in my 2001 P38.
It is hooked up to a parrot hands-free kit and works very well. I am able to playback music through the parrot as well as using it as a hands-free.
As of a couple of days ago, switch on the radio and nothing. Occasionally I will get a thump, thump from the rear bass speaker, but nothing else.

Any ideas?

A 2001 may well have the dreaded DSP amp in the boot which are known for dying without warning. Often temperature related when they initially fail so it might just start to work when it gets warmer (or colder). Is this in all modes or just when streaming?

All modes.

Do you have the DSP option under the tone button? If you do, it will be the amp almost certainly. New they are horrendously expensive and used is always a gamble as to how much life they have left in them. The DSP chip is sealed to the circuit board with some sort of resin and the general consensus is that the resin has a different coefficient of expansion than the chip and board so the stress of multiple hot cold cycles over the years causes the chip pins to come away from the board. Unfortunately nobody has yet succeeded in getting the resin off without destroying the chip.

Will have a look. What is DSP?

Digital Signal Processor/ing
It's a fancy way of applying effects like Theatre, Concert Hall etc. It's like having presets on an equaliser.
Utterly pointless but was all the rage for a while.

and still is. You won't find a system in a car that doesn't have it these days.

As pretty much every car with a separate DSP amplifier is known to give problems in later life I cannot understand why none of the Far Eastern suppliers make an affordable generic "universal" replacement that can be programmed to match pretty much any car.

Fundamentally the output side of a DSP amp is simply a bunch of class D amplifiers each driving a single speaker over a pre-programmed frequency range. The input side is basically either just an analogue to digital converter if the head unit output is analogue or a simple digital pass through if the head unit output is already digital. The bit in the middle just chops things up to get the right amounts of the right frequencies out to the amplifier driving each speaker.

Not forgetting the all important modifications and twiddly bits en-route producing all the (inaudibly different) special effects needed to look good on the specification sheets. A car, even a large quiet car like the P38, is pretty much the poster child for poor listening environment. Hard to think of a worse location than the bottom of the door for speakers! About the only way to make something sound seriously different is to wreck any pretensions to sensible audio.

So all you need is an amplifier box with enough outputs to handle all your speakers, suitable wiring to connect the car controls to the box and a phone app to program things. My iPhone does a very nice job of correcting my totally crappy hearing into something half sensible, the world is silly noisy using Airpods in transparency mode, so something to program a generic DSP isn't unreasonable.

I imagine that coming up with the mucked up sounds just like the original (Harman Kardon?) box if you load up with half a million quids worth of audio spectrum analyser might be bit more challenging. But making something that works with a decent sound will be pretty trivial these days.

Far as I could see from occasional looks inside the box most of the DSP amps were made in a manner intended to conceal the fact that, engineering wise, they were cheap crap with lashings of specmanship to convince folk they were paying for a real deal.

To modify a sometime well known quote from Peter Walker, head honcho of Quad Audio in their glory days

"If electrons could read we'd have serious hysteria induced distortion."

Peter was referring to the outpourings of the Audiophile press and the adverts therein but it it seems equally relevant when applied to DSP and in car audio in general specifications.

Clive

Gilbertd wrote:

and still is. You won't find a system in a car that doesn't have it these days.

Well, our youngest car is an 02 so I wouldn't know! :D I thought we'd grown out of it.

Sorry Clive, for once I have to totally disagree with you. Having a dead P38 HK DSP amp here the output stages are TDA8563Q Class-B amps. The output from the head unit is analogue at around 2.5V p-p so higher than normal line level (1V p-p) but lower than speaker level but only with two channels, left and right, the fade between front and rear is done by the amp. There is a data line from the head unit that controls the balance, fade, bass, sub level and treble. I will admit that the P38 amp is pretty basic compared with modern systems with just the presets for Spacial and Driver but it was designed when DSP was in its infancy.

In contrast, the Kenwood head unit I have in my car is pretty damn good. I know the theory of how it works but still can't get my head around how it actually achieves it. As well as a number of presets (Natural, Pop, Rock, Easy, Top 40, Jazz and Powerful) it also has full manual control of the 9 band graphic (which it took a mate, a retired sound engineer, the entire journey to the Dutch/German border to get how it should sound) which can be different for each source, as well as settings to tailor the sound for different types of car, different sized speakers, different speaker placings and a setting that allows the sound stage to be moved. So even though the speakers are low down in the doors, it can make them sound as though they are at ear level. With all the different settings, you now know why I never disconnect the battery on my car! I've changed the original door speakers for JBL Stage 600 CE units (straight swap) and also have a Pioneer powered underseat sub on top of the BeCM under the drivers seats. Listening at an 'adequate' volume, it sounds extremely good but can't hold a candle to something like the Meridian system in a L322 or later, or the Bose systems in a high line Audi or Bentley.

Marty did a replacement for the DSP amp using 4 door amps from a previous generation P38 as they were matched to the level and impedance coming from the standard head unit. Unfortunately to fit it involves sitting in the boot soldering and heat shrinking something like 40 wires. I've got the dead DSP amp, a pair of 50W Class D stereo modules, and four 2 way crossovers with the intention of building them into the original DSP amp box to make a plug and play replacement. The only additional wiring needed would be the two rear speaker outputs from the head unit. These are still there as they were used on the earlier door amp equipped cars but with no wiring in the loom to the DSP amp. However, it is one of those things that I went through how it could be done theoretically and bought the bits but never actually put them together as I don't have a car with the DSP system to try it in.

Sounds like you do now!!
And if you don't, I bet The Duchess will blow her DSP amp the moment I get her back on the road....

How strange, it started working again yesterday.

I won’t question it, but will think of some replacement for the future.

The weather has changed so if it is, as suspected, temperature related that would make sense.