JLM AUDIO

So if I get another 48V smps I can make bipolar 15-17V, but I need two TREX pcb's with one of the pcb's having its polarity reserved (so +48V into 0V, Vin to case ground) and exchanging regulator with tip126, and reversing all caps and zeners? Could it be done with a TREX2 alone (+2 smps)?

fragletrollet wrote: ↑

Thu Nov 04, 2021 11:36 pm

So if I get another 48V smps I can make bipolar 15-17V, but I need two TREX pcb's with one of the pcb's having its polarity reserved (so +48V into 0V, Vin to case ground) and exchanging regulator with tip126, and reversing all caps and zeners? Could it be done with a TREX2 alone (+2 smps)?

You can build a reversed polarity TREX as you describe but it has to be a seperate TREX. TREX2 would have to normal or fully reversed. It cannot be half and half.

I do have a 48v rail splitter in the works which will make +/-24vdc and has 2 x regs for +/-12v to +/-18v. But it will probably not be ready until next year.

Hi Joe,
I bought your TREX and the +48v SMPS for my Neve 1073 project that is more or less finished. I had a bit of crackly noise with the cheap Chinese +24v SMPS I originally purchased on eBay to test it (As I don't have a bench psu for testing yet).

I built your TREX and tested it yesterday and adjusted the voltage unloaded to +24v. I also constructed a phantom power box in an old stage box with through xlr's. All was tested, but then I came to problem of how to mount this little TREX?

There are no screws holes as I am accustomed to for mounting pcb's. What is you solution for this? As an interim measure I stuck cloth tape on the metal work and used a hot glue gun to glue the pcb to the chassis. Fast forward a couple of hours I plug in the psu and the 1073 and open up protools to run signal in and out. Very weak signal, then fades to nothing. I though 'oh dear, what's going on here?' So I test the rail with a multimeter and get 0v. Then I unplug everything and test each component, the SMPS is ok, the +24v is now +48v!

Opps. So I pull the pcb and test on bench still 48 unreg, then I power down and diode test the TIP122, cooked. Shorted. Remove TIP122 and test, still cooked.

My questions are:
Likely cause?
Just go ahead and replace TIP122?
Mounting?
Any damage to 1073 to be expected? i.e. transistors?
And, do I need a heatsink?
Thanks,
Stuart.

stuartpre123 wrote: ↑

Tue Aug 02, 2022 10:06 am

Hi Joe,
I bought your TREX and the +48v SMPS for my Neve 1073 project that is more or less finished. I had a bit of crackly noise with the cheap Chinese +24v SMPS I originally purchased on eBay to test it (As I don't have a bench psu for testing yet).

I built your TREX and tested it yesterday and adjusted the voltage unloaded to +24v. I also constructed a phantom power box in an old stage box with through xlr's. All was tested, but then I came to problem of how to mount this little TREX?

There are no screws holes as I am accustomed to for mounting pcb's. What is you solution for this? As an interim measure I stuck cloth tape on the metal work and used a hot glue gun to glue the pcb to the chassis. Fast forward a couple of hours I plug in the psu and the 1073 and open up protools to run signal in and out. Very weak signal, then fades to nothing. I though 'oh dear, what's going on here?' So I test the rail with a multimeter and get 0v. Then I unplug everything and test each component, the SMPS is ok, the +24v is now +48v!

Opps. So I pull the pcb and test on bench still 48 unreg, then I power down and diode test the TIP122, cooked. Shorted. Remove TIP122 and test, still cooked.

My questions are:
Likely cause?
Just go ahead and replace TIP122?
Mounting?
Any damage to 1073 to be expected? i.e. transistors?
Thanks,
Stuart.

The Trex mounts with the TIP122 metal tab mounting kit provided in the kit (3M bolt and silicon thermal pad and white bush and nut and washer) to a metal case or heatsink needed to get rid of the 3watts of heat it is generating when running one 1073. You should also have a 250mA slow blow fuse after the 48v smps and before the TREX as if the insulation kit or multimeter probe ever short the tip122 metal tab which to the case it will cause a dead short circuit. If heatsinked properly the TIP122 will handle 1A or more. Without heatsinking you will cook it.

Joe Malone wrote: ↑

Tue Aug 02, 2022 10:27 am

stuartpre123 wrote: ↑

Tue Aug 02, 2022 10:06 am

Hi Joe,
I bought your TREX and the +48v SMPS for my Neve 1073 project that is more or less finished. I had a bit of crackly noise with the cheap Chinese +24v SMPS I originally purchased on eBay to test it (As I don't have a bench psu for testing yet).

I built your TREX and tested it yesterday and adjusted the voltage unloaded to +24v. I also constructed a phantom power box in an old stage box with through xlr's. All was tested, but then I came to problem of how to mount this little TREX?

There are no screws holes as I am accustomed to for mounting pcb's. What is you solution for this? As an interim measure I stuck cloth tape on the metal work and used a hot glue gun to glue the pcb to the chassis. Fast forward a couple of hours I plug in the psu and the 1073 and open up protools to run signal in and out. Very weak signal, then fades to nothing. I though 'oh dear, what's going on here?' So I test the rail with a multimeter and get 0v. Then I unplug everything and test each component, the SMPS is ok, the +24v is now +48v!

Opps. So I pull the pcb and test on bench still 48 unreg, then I power down and diode test the TIP122, cooked. Shorted. Remove TIP122 and test, still cooked.

My questions are:
Likely cause?
Just go ahead and replace TIP122?
Mounting?
Any damage to 1073 to be expected? i.e. transistors?
Thanks,
Stuart.

The Trex mounts with the TIP122 metal tab mounting kit provided in the kit (3M bolt and silicon thermal pad and white bush and nut and washer) to a metal case or heatsink needed to get rid of the 3watts of heat it is generating when running one 1073. You should also have a 250mA slow blow fuse after the 48v smps and before the TREX as if the insulation kit or multimeter probe ever short the tip122 metal tab which to the case it will cause a dead short circuit. If heatsinked properly the TIP122 will handle 1A or more. Without heatsinking you will cook it.

Ok, that makes sense. Should I use heatsink paste?

stuartpre123 wrote: ↑

Tue Aug 02, 2022 11:51 am

Joe Malone wrote: ↑

Tue Aug 02, 2022 10:27 am

stuartpre123 wrote: ↑

Tue Aug 02, 2022 10:06 am

Hi Joe,
I bought your TREX and the +48v SMPS for my Neve 1073 project that is more or less finished. I had a bit of crackly noise with the cheap Chinese +24v SMPS I originally purchased on eBay to test it (As I don't have a bench psu for testing yet).

I built your TREX and tested it yesterday and adjusted the voltage unloaded to +24v. I also constructed a phantom power box in an old stage box with through xlr's. All was tested, but then I came to problem of how to mount this little TREX?

There are no screws holes as I am accustomed to for mounting pcb's. What is you solution for this? As an interim measure I stuck cloth tape on the metal work and used a hot glue gun to glue the pcb to the chassis. Fast forward a couple of hours I plug in the psu and the 1073 and open up protools to run signal in and out. Very weak signal, then fades to nothing. I though 'oh dear, what's going on here?' So I test the rail with a multimeter and get 0v. Then I unplug everything and test each component, the SMPS is ok, the +24v is now +48v!

Opps. So I pull the pcb and test on bench still 48 unreg, then I power down and diode test the TIP122, cooked. Shorted. Remove TIP122 and test, still cooked.

My questions are:
Likely cause?
Just go ahead and replace TIP122?
Mounting?
Any damage to 1073 to be expected? i.e. transistors?
Thanks,
Stuart.

The Trex mounts with the TIP122 metal tab mounting kit provided in the kit (3M bolt and silicon thermal pad and white bush and nut and washer) to a metal case or heatsink needed to get rid of the 3watts of heat it is generating when running one 1073. You should also have a 250mA slow blow fuse after the 48v smps and before the TREX as if the insulation kit or multimeter probe ever short the tip122 metal tab which to the case it will cause a dead short circuit. If heatsinked properly the TIP122 will handle 1A or more. Without heatsinking you will cook it.

Ok, that makes sense. Should I use heatsink paste?

NO the grey stick on silicon pad doesn't require any paste. Make sure you deburr the 3mm hole you drill to mount the TREX and fit the 3M bolt from outside of case into 3mm hole then silicon pad then TIP122 hole and fit the white bush into the hole on the TO220 before fitting the lock washer and nut. Tighten and test that you have no short between the TIP122 metal tab and chassis or heatsink before wiring to the TREX.

Joe Malone wrote: ↑

Tue Aug 02, 2022 1:30 pm

stuartpre123 wrote: ↑

Tue Aug 02, 2022 11:51 am

Joe Malone wrote: ↑

Tue Aug 02, 2022 10:27 am

The Trex mounts with the TIP122 metal tab mounting kit provided in the kit (3M bolt and silicon thermal pad and white bush and nut and washer) to a metal case or heatsink needed to get rid of the 3watts of heat it is generating when running one 1073. You should also have a 250mA slow blow fuse after the 48v smps and before the TREX as if the insulation kit or multimeter probe ever short the tip122 metal tab which to the case it will cause a dead short circuit. If heatsinked properly the TIP122 will handle 1A or more. Without heatsinking you will cook it.

Ok, that makes sense. Should I use heatsink paste?

NO the grey stick on silicon pad doesn't require any paste. Make sure you deburr the 3mm hole you drill to mount the TREX and fit the 3M bolt from outside of case into 3mm hole then silicon pad then TIP122 hole and fit the white bush into the hole on the TO220 before fitting the lock washer and nut. Tighten and test that you have no short between the TIP122 metal tab and chassis or heatsink before wiring to the TREX.

Hi Joe,
I did the above the psu test fine. Unfortunately my 1073 is not working as well as before. The sound is very quiet. I have checked transistors, they seem ok. I think the 48v got applied to the 1073 for a minute or so. What components would suffer? Should I be replacing the 25v capacitors around BA283 connector?

stuartpre123 wrote: ↑

Wed Aug 03, 2022 5:38 pm

Joe Malone wrote: ↑

Tue Aug 02, 2022 1:30 pm

stuartpre123 wrote: ↑

Tue Aug 02, 2022 11:51 am

Ok, that makes sense. Should I use heatsink paste?

NO the grey stick on silicon pad doesn't require any paste. Make sure you deburr the 3mm hole you drill to mount the TREX and fit the 3M bolt from outside of case into 3mm hole then silicon pad then TIP122 hole and fit the white bush into the hole on the TO220 before fitting the lock washer and nut. Tighten and test that you have no short between the TIP122 metal tab and chassis or heatsink before wiring to the TREX.

Hi Joe,
I did the above the psu test fine. Unfortunately my 1073 is not working as well as before. The sound is very quiet. I have checked transistors, they seem ok. I think the 48v got applied to the 1073 for a minute or so. What components would suffer? Should I be replacing the 25v capacitors around BA283 connector?

The caps are all resistively feed so should be fine unless one has popped the can or a tant has gone short circuit. I would check 12R 1W is still intact and if it still has 1.4v across it? The most likely would be a bc transistor on the output stage. Listen to the Feed to the output volume pot to see if the preamps are working or not.

Joe,

Question -

If I wanted +48v/-24v for a build, could I simply float the input (+/-) of your +48 SMPS and run the (-) rail to a polarity-flipped T-Rex to get it down to -24v?

I've got some PNP TIP 125's on the bench and boy oh boy would that be a cheap solution for this.

In the case that works, what would connect to OV on the T-Rex? The chassis/Audio ground?

TheFrozenone wrote: ↑

Tue Aug 16, 2022 4:31 pm

Joe,

Question -

If I wanted +48v/-24v for a build, could I simply float the input (+/-) of your +48 SMPS and run the (-) rail to a polarity-flipped T-Rex to get it down to -24v?

I've got some PNP TIP 125's on the bench and boy oh boy would that be a cheap solution for this.

In the case that works, what would connect to OV on the T-Rex? The chassis/Audio ground?

No 48vdc cannot be made into 72vdc = +48vdc to -24vdc. Use our AC/DC EM kit with 2 x 25vac transformer to give you +48vdc and +/-24vdc

OK, copy that. I'm going to grab a few of those and make some external power supplies for the final builds. Of course you have a solution for this on deck! Much appreciated!


I do have a hypothetical here for you Joe. I need +48vdc/-24vdc for this circuit. The +48vdc is just for phantom power, the -24vdc is the power for the preamp.

If I wanted to - just for temporary testing purposes - could I run a +48vdc SMPS for the phantom power AND a -24vdc SMPS for the preamp power on seperate 2.1mm jacks, referencing both of them to the same ground (chassis/audio ground)?

I've tried the -24vdc SMPS by itself and it seems to run the pre, but I'm not sure if its OK to reference two different PSU's to the same ground like that, especially if one is (-) and one (+).

Showing my inexperience here. Thanks for any advice Joe.

TheFrozenone wrote: ↑

Tue Aug 16, 2022 8:38 pm

OK, copy that. I'm going to grab a few of those and make some external power supplies for the final builds. Of course you have a solution for this on deck! Much appreciated!


I do have a hypothetical here for you Joe. I need +48vdc/-24vdc for this circuit. The +48vdc is just for phantom power, the -24vdc is the power for the preamp.

If I wanted to - just for temporary testing purposes - could I run a +48vdc SMPS for the phantom power AND a -24vdc SMPS for the preamp power on seperate 2.1mm jacks, referencing both of them to the same ground (chassis/audio ground)?

I've tried the -24vdc SMPS by itself and it seems to run the pre, but I'm not sure if its OK to reference two different PSU's to the same ground like that, especially if one is (-) and one (+).

Showing my inexperience here. Thanks for any advice Joe.

If the 2 power supplies are floating then yes you can connect them to make +48v and -24v with the connection between them being 0v.

Joe,

One last point of confusion for me on this:

If I run the (+) of the 48vdc PSU to the Phantom switch, and ground the (-) at the chassis, and then do the opposite for the 24vdc PSU - (-) to preamp, (+) to chassis - aren't these no longer "floating" supplies? Does that matter, or am I missing something here?

Once again, excuse my ignorance on these details. And thanks again Joe.

TheFrozenone wrote: ↑

Wed Aug 17, 2022 6:24 am

Joe,

One last point of confusion for me on this:

If I run the (+) of the 48vdc PSU to the Phantom switch, and ground the (-) at the chassis, and then do the opposite for the 24vdc PSU - (-) to preamp, (+) to chassis - aren't these no longer "floating" supplies? Does that matter, or am I missing something here?

Once again, excuse my ignorance on these details. And thanks again Joe.

Yes once you connect them to together and to chassis they are referenced to mains ground and not floating which is fine. The floating is only important as some SMPS have -v linked to mains ground and if you try to make a -V it will short out.

Thanks Joe! That helped a lot.