Line driver help

[vwdude]

I think my sld44 is adding distortion to the system as it's all I added and now I have distortion. The gains on the amp are all the way down. Then I get the gains on the line driver near 1/2 I get noise, but I have plenty of volume with them near zero as well. The problem is, when I turn my head unit up to volume 12 or 13 I get distortion at peaks.

Is my line driver bad or set wrong? The volume on my ms8 was at -7db, I lowered it to -25db in order to increase the line driver gains from zero to just above zero (otherwise my sub was draining out my components).

[vwdude]

After reading Eric Ds thread I need to add some I go.

Before the line driver was installed I used to have 15 as my normal loud volume level on e deck, with no audible distortion. This was when my ms8 was at -7db (which should be slightly less than 2.6 volts of signal). The amp gains were somewhere between 1/2 and 2/3.

Now, with the ms8 volume at -25db (much less than 2.6 volts of signal) and the amp gains down to zero and the line driver (suspect) gains at no more than 1/3 I have some very audible distortion at head unit volume 13 (other than the distortion, the loudness is about the same as 15 was previous to the line driver).

It was my understanding that he line driver would need to be turned up more than it is now, even with the amps down to zero. Does the line driver have a voltage boost even at zero gain? [\b]

And to better explain, when I first installed the line driver, my ms8 was at -7db, amp gains all at 0 and line driver gains all at 0. My sub was overpowering the rest of the speakers so I lowered the ms8 volume and then increased the line driver gain to level everything out. This is now where I have distortion. I also tried to defeat the ms8 processing to eliminate a bad eq setting but the distortion is still present.

[trickyricky]

If you think about it....if you lower your signal from the very beginning your just begging for noise. Especially after you use a line driver and try to get the most out of it.

Think about it this way, now that you lower your input signal any low noise can boosted tremendously by the line driver.


Someone please correct me if I am wrong, as this is just an assumption from me.


I would think the best way to set the line driver would be to have the input signal as high as possible (while being clean...no audible distortion/noise/clipping) then adjust the line driver to get the most out of it without any audible distortion/noise/clipping. That would be my best guess.

[vwdude]

Ricky you are spot on and I agree. My issue was that with the higher signal voltage I had no adjustability to tune the sub down.

The more I listen the worse it's getting. Now the left side is starting to cut out. I got this line driver on eBay and it came without a power plug (I got one separately) and there is a sharpie mark going through the PG logo, I wonder if this unit is bad.

I had expected it all to o like this: I set my head unit to 15, I have the ms8 volume pretty high, I set te line driver near 1/2 gain and the amp gains at 0. With that configuration I would blow my speakers (and ear drums).

If the radio volume were set to 0 to start I could set everything else how I expect and then turn the radio volume up.

[ajaye]

The first thing that jumps out at me is the MS8's SNR listed at 90(db I assume, it just says "90") for the line level stage. I think the least expensive amp I have specs at >100db. The SLD44 specs at >110db for line level for comparison. That really shouldn't be causing distorted transients though.

If it didn't behave like this before and the only thing you did was add the SLD44, then I would go back and turn the line driver output gains all the way down and the amp input gains all the way down. If you still hear the distortion at the head unit set where you usually had it as "loud but clean" before, then you are overdriving something on the input side somehow, presumably the line driver. If its clean then you are overdriving the amps with the line driver. Remember +3db gain is like adding 1.4 volts give or take, so with up to +34db on the line driver, with it 1/2 way up you are adding almost 8 volts. Even if you're peaks are 2 volts from the MS8 that's pushing 10 to the amps.

[Drock]

Is the line driver before or after the ms8?

Did you just add the line driver without resetting the ms8?

Ms8's max output is 2.4 volts.

I had the same problem and moved the line driver to after the ms8. Worked fine after that. I use a tld66.


Sent from my iPhone using Tapatalk

[vwdude]

The first thing that jumps out at me is the MS8's SNR listed at 90(db I assume, it just says "90") for the line level stage. I think the least expensive amp I have specs at >100db. The SLD44 specs at >110db for line level for comparison. That really shouldn't be causing distorted transients though.

If it didn't behave like this before and the only thing you did was add the SLD44, then I would go back and turn the line driver output gains all the way down and the amp input gains all the way down. If you still hear the distortion at the head unit set where you usually had it as "loud but clean" before, then you are overdriving something on the input side somehow, presumably the line driver. If its clean then you are overdriving the amps with the line driver. Remember +3db gain is like adding 1.4 volts give or take, so with up to +34db on the line driver, with it 1/2 way up you are adding almost 8 volts. Even if you're peaks are 2 volts from the MS8 that's pushing 10 to the amps.

So you are saying that with the line driver gains at 0 (all the way down) it is as if it's not there? It makes sense but that's not how my system reacted. Previous to the sld44 my amp gains were above 1/2, after I turned them down to 0 and with the line driver set to 0 gain I had much more volume from the sub and a little more from he speakers. This is of course after retuning the ms8.

I will try it again though. I am a bit worried that the sld44 is bad internally, but this will be a good test.

Is the line driver before or after the ms8?

Did you just add the line driver without resetting the ms8?

Ms8's max output is 2.4 volts.

I had the same problem and moved the line driver to after the ms8. Worked fine after that. I use a tld66.


Sent from my iPhone using Tapatalk

The line driver is after the ms8. It wouldn't work before it as the ms8 has a max output of 2.6 volts and I'm using ZPA amps which need 8 volts of signal.

[groundpounder]

Is the line driver housing isolated from the vehicle chasses and vehicle ground?

[vwdude]

Yea it's mounted on a wooden board like my ms8, passive crossovers and distribution block. It is grounded to the same ground as the rest of the system.

[zeropoint0.5]

do you have this distortion on all 4 of the outputs of the sld44 ?

could you try the setup out on a aftermarket headunit with rica outputs, straight to the sld44 ,
then to the zpa's with closed gains......

my thoughts about the trimmers of the sld44, is that they are linear pots, so you will never have
to turn them as much open as for example the pld1 with the logaritmic gain pots......
people correct me if i'm wrong in this........

the most easiest way to test would be if you had an second sld44 to try out of course.........

[vwdude]

I dont have an ability to go straight from an aftermarket head unit to the sld.

Not sure if it's on all 4 channels as two are to the sub, but I can move the channels around.

I'm in search of a pair of PLDs to try out/ replace the sld with. Id prefer older ones with the older PG logo, if anyone knows of someone selling any.

[Corty75]

Did have the same issue with a pld1 mkI

Moved the pld1 from the 3ft RCA from HU, to the back 3ft before the AMP !
It worked.. Then i twisted all the power suply wirering.
Dont know if it would work ina sld44

[vwdude]

So you moved the line driver closer to the amp and it made it work better?

I have less than 2 feet of RCA between my ms8, sld and amps.. I made the RCAs myself from shielded and twisted high end microphone cable and high end home audio RCA cables (in case anyone suspects the cables).

Tomorrow I will try lowering the line driver gains all the way and increasing the amp gains where needed to balance the system. Before I had the line driver I didn't have any distortion or noise so if I can eliminate it from the line driver then the sound should improve.

[vwdude]

I lowered the line driver gains for my front speakers to zero and the distortion dropped significantly and I no longer hear idle noise. My amp gains are still at zero, I just increased my ms8 volume a little.

So my question, is the
Line driver supposed to give a voltage boost even with zero gain? Is the line driver bad if it's adding noise and distortion even at less than 1/3 gain or is just that I had to lower the ms8 signal too much when I used any gain from the line driver?

Either way, I think I found my happy medium. I'm getting very little distortion, but it's at levels higher than I ever plan to listen at anyway.

Edit: the more I think about this I think the problem might be that the amps are too powerful. Is that possible? At zero gain on the amp I needed to lower something to have some adjustability when I used the line driver. I guess I need to just keep the line driver at zero gain. Without the line driver I needed the amp gains over 1/2.

[ajaye]

I lowered the line driver gains for my front speakers to zero and the distortion dropped significantly and I no longer hear idle noise. My amp gains are still at zero, I just increased my ms8 volume a little.

So my question, is the
Line driver supposed to give a voltage boost even with zero gain? Is the line driver bad if it's adding noise and distortion even at less than 1/3 gain or is just that I had to lower the ms8 signal too much when I used any gain from the line driver?

Either way, I think I found my happy medium. I'm getting very little distortion, but it's at levels higher than I ever plan to listen at anyway.

Edit: the more I think about this I think the problem might be that the amps are too powerful. Is that possible? At zero gain on the amp I needed to lower something to have some adjustability when I used the line driver. I guess I need to just keep the line driver at zero gain. Without the line driver I needed the amp gains over 1/2.

Some of your questions are good ones but impossible to answer without knowing way more info. Like zeropoint said, the sld44 has linear trim pots so how much they are turned up physically is a lot less a concern than how much boost they are actually adding to the signal and what the signal was to start. That thing can push a hot enough signal to overdrive a lot of amps' inputs with a decent signal fed to it already. I have no experience with the MS8 or anything like it..ideally you need to feed a clean signal directly to the line driver and determine if the driver is injecting noise or if its the ms8 making the noise and the line driver just amplifying it. You can try using an ipod/iphone straight to the line driver. They are noisey little shits themselves though, especially from the headphone jack.

If you want some tones at different levels to help you fine tune/troubleshoot I can make you just about anything you want and you can just burn to CD or even put on an iphone.

[vwdude]

I'm planning to run the source going into the sld to channel 1 of my oscope and the output to channel 2 to compare. Then I'll run a sine wave. That should tell me if it's adding distortion. I just haven't had time to do it.

Thanks for the help. I'll report back once I've done that, posting a pic of the screen.

[vwdude]

I finally got around to removing the SLD44. What do you all think of what I found?





To explain what I see (if it's not showing in the pics) the blue nichicon caps have a crystallized material near the base of them. I've never seen this before, but I ordered all new caps (both the blue and the black ones, not the smaller ones) as well as all new ICs (4 opamp sand 1 PWM).

I tried to get ELNA caps but to match the size I would need a uf rating somewhere around 10% of what's there (35v, 22uf) so needless to say it wouldn't work. When I got all new ICs I got all TI. The OEM ones are Fairchild. Not sure if that's an upgrade, downgrade, or lateral move.