AML 52F50

[dkziemann]

Bumping for visibility

 

[andYz00m]

There are two jumpers on the main PCB that let you choose whether you want to use the xlr on the back of the rack for stereo linking or the backplane.

If you use the xlr option, you connect the xlr inputs of the second card (two slot unit) to bridge the stereo link. In the colourbook it shows the xlr stereo link being the hot lead of the xlr input of the second card.

Hope this helps.

 

[noizetoys]

Here's the pdf I got from Colin.

 

[JMan]

Does that mean that to link two units, you simply connect them with a male-to-male xlr to that port on each unit?

 

[andYz00m]

Yes. Or if you have a lunchbox that has TRS I/O as well you could just patch it.

make sure you have the stereo link jumpers configured correctly!

 

[dkziemann]

Thank you all!

 

[dkziemann]

Hey everyone — built one of these up and everything works well! (This was after accidentally melting one of the 24v relay switches... but I swapped it out and everything is good again).

There's one issue I can't trace, though. When I engage the first (f1) HPF while in gain reduction mode, the meter doesn't react — no movement at all. I can definitely hear the difference, but it doesn't show me how much gain reduction there is. When the HPF is off or on f2, the meter reacts normally.


Any thoughts on how to troubleshoot this?

Thanks

 

[dkziemann]

Thanks for your reply. Sorry I didn't see it until today.

The unit does power up just fine. In fact, the unit appears to be working just fine with the sole exception of the metering in gain reduction mode. The meter works just fine in input and output modes, but never moves off of the bottom in gain reduction mode (even though there is gain reduction happening). Seems like it should be a fairly easy thing to track down, but I haven't managed to figure it out yet. I'll check the clearances again more carefully, but I didn't see anything amiss in that area upon first inspection.

Did you ever figure out the issue? My unit is displaying the exact same behavior in gain reduction mode while on the first sidechain setting.

 

[dkziemann]

Bumping for visibility in case anyone has suggestions

 

[Phantasm]

First post on groupdiy so hello all.

I've just built an AML 52F50 comp and having trouble with the calibration. It would appear that I see around 17V on R156 - has anyone else seen this? I have an IGS audio rack an its PSU led's are all happy so doesn't appear to be doing anything bad to the PSU but the instructions suggest 130mV which is a huge difference. Anyone else seen this? I removed all other modules so the rack was only powering the AML and I have no stereo links fitted.

I built it very carefully each component value at a time and have a lot of experience with hand building prototype PCB's and cannot see any build errors. I checked off each component with a highlighter at each step and didn't run into any components in incorrect locations during the build so don't think it's anything like that at fault. Cannot see any shorts and checked each solder joint when fitting each component for solder through to the topside of the PCB so should all have good joints.

When comp is switched in the signal drops to almost nothing also so must be something significantly wrong. I've message Colin at AML but no reply so far so thought I'd try here for any suggestions as I'm guessing he's busy.

Thanks in advance.

 

[Phantasm]

Heard back from Colin at AML and he doesn't offer any kind of tech support or any advice on thing to check but said I could return it for repair but think I'll persevere for a bit first as just been allowed to borrow a better function generator from work and after all I took this on to learn more about audio gear and do it myself plus need to make the extender cards earn their money. I'll report back with findings.

 

[andYz00m]

Hey everyone — built one of these up and everything works well! (This was after accidentally melting one of the 24v relay switches... but I swapped it out and everything is good again).

There's one issue I can't trace, though. When I engage the first (f1) HPF while in gain reduction mode, the meter doesn't react — no movement at all. I can definitely hear the difference, but it doesn't show me how much gain reduction there is. When the HPF is off or on f2, the meter reacts normally.


Any thoughts on how to troubleshoot this?

Thanks

The first HPF is pretty high (I think its like 300Hz) so the detector is missing a whole lot of low end which is way more signal that high frequencies. This is intentional so that you let the low end isnt pumping the detector circuit. Try cranking down the threshold to see if the GR meter shows more gain reduced.

If the unit is built correctly, you will see way less GR on HPF f1 than the other two modes.

 

[andYz00m]

First post on groupdiy so hello all.

I've just built an AML 52F50 comp and having trouble with the calibration. It would appear that I see around 17V on R156 - has anyone else seen this? I have an IGS audio rack an its PSU led's are all happy so doesn't appear to be doing anything bad to the PSU but the instructions suggest 130mV which is a huge difference. Anyone else seen this? I removed all other modules so the rack was only powering the AML and I have no stereo links fitted.

I built it very carefully each component value at a time and have a lot of experience with hand building prototype PCB's and cannot see any build errors. I checked off each component with a highlighter at each step and didn't run into any components in incorrect locations during the build so don't think it's anything like that at fault. Cannot see any shorts and checked each solder joint when fitting each component for solder through to the topside of the PCB so should all have good joints.

When comp is switched in the signal drops to almost nothing also so must be something significantly wrong. I've message Colin at AML but no reply so far so thought I'd try here for any suggestions as I'm guessing he's busy.

Thanks in advance.

Lots of things to test. I never got R156 to give me an accurate reading ever, tried multiple ways. I ended up just using a DC bench supply to measure how much current was being drawn and used that to calibrate the bias.

Another thing you can do is just put the bias pot in the middle (20 turns total end to end on those little trim pots). So turn the bias pot all the way counter clock wise until it starts clicking (bottoms out) and then turn it 10 full rotations clockwise. You will have a reasonable bias. If you crank the bias up too high you will have distortion. (I know this first hand as my original bias using R156 method ended up being like 210mv) This method is totally fine especially if you arent using a stereo pair as you dont care as much about them being exactly the same.

hope this helps.

 

[Phantasm]

Lots of things to test. I never got R156 to give me an accurate reading ever, tried multiple ways. I ended up just using a DC bench supply to measure how much current was being drawn and used that to calibrate the bias.

Another thing you can do is just put the bias pot in the middle (20 turns total end to end on those little trim pots). So turn the bias pot all the way counter clock wise until it starts clicking (bottoms out) and then turn it 10 full rotations clockwise. You will have a reasonable bias. If you crank the bias up too high you will have distortion. (I know this first hand as my original bias using R156 method ended up being like 210mv) This method is totally fine especially if you arent using a stereo pair as you dont care as much about them being exactly the same.

hope this helps.

Hey, thanks very much for the tips - I'm going to be using it in mono so no worries with matching for a pair so I will give your method a whirl. Yeah a lot of turns on those trim pots - spent years tweaking those at work so quite familiar but just don't appear to be giving much adjustment on my module so something else is wrong I'm sure. I'll figure everything out and come back with findings for anyone else's future reference and add to the knowledge base. Most perplexed at the 1ohm resister showing 17V which suggests 17A which I would think would be letting the smoke out pretty quickly if genuine. My DMM isn't calibrated but even so is pretty accurate - a Metrix MX54 so pretty decent.

Thanks again.

 

[Beeswax]

Lots of things to test. I never got R156 to give me an accurate reading ever, tried multiple ways. I ended up just using a DC bench supply to measure how much current was being drawn and used that to calibrate the bias.

Another thing you can do is just put the bias pot in the middle (20 turns total end to end on those little trim pots). So turn the bias pot all the way counter clock wise until it starts clicking (bottoms out) and then turn it 10 full rotations clockwise. You will have a reasonable bias. If you crank the bias up too high you will have distortion. (I know this first hand as my original bias using R156 method ended up being like 210mv) This method is totally fine especially if you arent using a stereo pair as you dont care as much about them being exactly the same.

hope this helps.

I've turned the O/P Bias Adjust more than 100 times and no click - no reading either. It measures resistance on the probe and when I turn it, so it's not broken. Getting +/- 16v too.

 

[dkziemann]

The first HPF is pretty high (I think its like 300Hz) so the detector is missing a whole lot of low end which is way more signal that high frequencies. This is intentional so that you let the low end isnt pumping the detector circuit. Try cranking down the threshold to see if the GR meter shows more gain reduced.

If the unit is built correctly, you will see way less GR on HPF f1 than the other two modes.

Thank you so much for the reply!

 

[Phantasm]

I've turned the O/P Bias Adjust more than 100 times and no click - no reading either. It measures resistance on the probe and when I turn it, so it's not broken. Getting +/- 16v too.

Have you done full turns? With these trimmers sometimes it seems like they go on forever but the end stop should be there. Mine took a long time to get to the end stop.

 

[andYz00m]

Yeah the little Bourns blue trim pots right? They do seem to go forever! But there should be a tiny audible click at both min and max.

you could also just turn it like 30 times and assume you have it at the minimum…

 

[Phantasm]

Yeah the little Bourns blue trim pots right? They do seem to go forever! But there should be a tiny audible click at both min and max.

you could also just turn it like 30 times and assume you have it at the minimum…

That's them. Haven't had the need to meddle with any for a long time and forgot how long they go on for with this build but carried on and found the end stop.

 

[Beeswax]

That's them. Haven't had the need to meddle with any for a long time and forgot how long they go on for with this build but carried on and found the end stop.

Does this timmer affect initial mA/mV reading across R156? I've turned this trimmer 100 times