Whistle Rock Audio ML12 preamp BUILD/HELP thread!

[redear]

Why do you think that?
Whats the problem? you gave no information

The hum can be from a lot of different places and reasons.
Why do you think the PSU is noisy?

Hum can be from a bad ground connection, or a ground loop.
Hum can be also electromagnetic interference from the Power transformer,
it's better to understand first wheres the source for the noise, your PSU might be totally fine

I think you should probably do a seperate thread for your problems and for what you want to accomplish as this thread is for the "Whistle Rock Audio ML12 preamp" project only

Essentially, unless I turn a guitar amp up real loud, far louder than I wish to work, I get no signal. The guy who built it said it was for drums but I can’t get any useful signal in that context either as we just don’t play that loud.

Re: the hum; The actual PSU unit makes noise. There is also a grounding issue but I know about that. I mean that there is a low but audible hum from the power supply as a noise in the room.

My thought was that I would move the transformer and opamp to 4 ML12 cards. This posting here. But if that is not possible I’m back to the drawing board and will post elsewhere gladly. 

 

[TillM]

Yes you can build the ML12 with the Jensen transformers and the 990opamp.
But as far as I understand, your pre don’t work like it should.

 

[redear]

Yes you can build the ML12 with the Jensen transformers and the 990opamp.
But as far as I understand, your pre don’t work like it should.

Indeed. But it seems more straight forward to me, not try to repair a preamp for which I have no schematic and to simply build a on a known and proven design.

 

[Whoops]

I know what you mean and feel.

I also was in th same situation in the past, and I find it's much more easy to build myself a project from scratch that to try to fix or repair an "almost complete project built by another person".

I don't think tracing the schematic would be hard as it seems a simple enough circuit but by the photo you shown it really seems like a huge wiring mess, it doesn't even look like a nice build.

I would do exactly what you suggested, dismantle everything and built another project with the parts from scratch.

I guess you still need an output transformer, no?

 

[redear]

I would need an output transformer but I know there  are a lot of sources for those. I honestly wish I could find a way to move these into a 500 format simply... ahh well.

 

[Meathands]

Just wanted to notify this thread that we are sold out and won't be restocking ML12 PCBs at DIYRE. But I uploaded them to OSHPark and made them public so you can order them in sets of 3 for a pretty reasonable price:

https://oshpark.com/shared_projects/Q8ffv5SG
https://oshpark.com/shared_projects/eXbLkFWG
https://oshpark.com/shared_projects/E344D0uR

 

[TillM]

Thanks for that Peterson.
The only thing I don’t like ordering at oshpark is, that you always have to buy 3 PCBs.

 

[Chris-audio.com]

Hey All,
im wondering if you can help. Im pretty stuck when it comes to connecting the power transformer to this build. Ive only ever built guitar pedals before and accustomed to only dealing with 9v.

Basically my questions is.. Im using a Triad VPT36-690 Power Transformer. I have no idea how to connect the four input wires (Brown, Blue, Grey And Violet) to my IEC power socket. Do I combine the colors in a certain configuration?

Secondly, I am confused regarding how to connect the four output wires (black, red, yellow and orange) to the input of the ML12 PSU PCB.

Any help would be very greatly appreciated.

Thank you

 

[Whoops]

Just wanted to notify this thread that we are sold out and won't be restocking ML12 PCBs at DIYRE. But I uploaded them to OSHPark and made them public so you can order them in sets of 3 for a pretty reasonable price:

https://oshpark.com/shared_projects/Q8ffv5SG
https://oshpark.com/shared_projects/eXbLkFWG
https://oshpark.com/shared_projects/E344D0uR

Thank you so much Peterson

 

[Whoops]

I honestly wish I could find a way to move these into a 500 format simply... ahh well.

That's pretty easy an inexpensive to do, get a kit from avdaudio it includes PCB , Front panel and L-Bracket

http://www.avdaudio.com/catalog.htm?id=1413

 

[Whoops]

Hey All,
im wondering if you can help. Im pretty stuck when it comes to connecting the power transformer to this build. Ive only ever built guitar pedals before and accustomed to only dealing with 9v.

Basically my questions is.. Im using a Triad VPT36-690 Power Transformer. I have no idea how to connect the four input wires (Brown, Blue, Grey And Violet) to my IEC power socket. Do I combine the colors in a certain configuration?

Secondly, I am confused regarding how to connect the four output wires (black, red, yellow and orange) to the input of the ML12 PSU PCB.

Any help would be very greatly appreciated.

Thank you

Post a picture of that specific transformer schematic/diagram and we will let you know

Let us know where are you located also, is it a 240V , 120V or 110V country?

 

[Chris-audio.com]

Post a picture of that specific transformer schematic/diagram and we will let you know

Let us know where are you located also, is it a 240V , 120V or 110V country?

Hey, I am in USA ..110V

I can't seem to figure out a picture, But the Datasheet for transformer with schematic is here.

https://www.mouser.com/datasheet/2/410/media-1067252.pdf



On the PCB for the PSU it looks like there are 4 inputs that should come from power transformer, Labeled AC, CT, CT, AC.

Thank you!

 

[Chris-audio.com]

Im led to believe ....

"Okay, CT stands for center tap.

Which is the point between the windings in you put them in series.

You either want black and yellow for CT and red and orange for AC or the other way around. It doesn’t matter because it’s AC (unless you need the output to be in phase with mains, which you don’t here)."

 

[TillM]

I think your transformer has to much power.
When you center tap them, you get 36vac.
So you have to put them in parallel.
So that you just connect the AC on your PCB.
Then you get 18VAC.
Do you want to use it with +/- 16v or +/-24v ?

 

[Chris-audio.com]

I think your transformer has to much power.
When you center tap them, you get 36vac.
So you have to put them in parallel.
So that you just connect the AC on your PCB.
Then you get 18VAC.
Do you want to use it with +/- 16v or +/-24v ?

I have no idea if I want to use it with 16 or 24. I have been trying to figure out how to connect this transformer to this PCB for close to 2 months. Honestly thinking maybe ill just go buy a new pre. I wish I were a little more knowledge. Cannot seem to figure this out for the life of me.

My current plan was to combine (Brown and Grey) and (Vio and Blue) for input. Then outputs to the PCB would be Red And Orange into the two AC point, Black and Yellow into the two CT spots.

Will that work?

 

[Whoops]

Hey, I am in USA ..110V

I can't seem to figure out a picture,

Don't you know how to do a print screen?
And then post a picture in the post?

If you try to make what you need more clear and with less hassle for the other users, more people will help you.
If it's too much hassle for others, probably you will not get much help in forums.

My 2 cents

 

[Whoops]

This is how you should wire it:

 

[Whoops]

I think your transformer has to much power.

Too much power?

It's 700mA per each primary. So it's good to power 4x 312 Mic preamps plus phantom power and still have some good safety margin.

 

[Chris-audio.com]

This is how you should wire it:

Hey Whoops,

As per your picture, are you saying that Red and Orange should go to where it says CT on the board?

Its a little confusing because the board is labeled as such

  ~  - AC
0V - CT
  ~  - CT
0V - AC

Weirdly enough, where you say to put Red and Orange to 0V . On the pcb its labeled 0V next to a pin that says AC.

Im so sorry, im not sure why this is so incredibly confusing to me. I fee like the labels next to the Pins (~ and 0V) totally contradict that its labeled AC on the board.

Im really not trying to make this more difficult.  When you says connect Black and Yellow to AC as per your diagram (thanks). On the build document is says 0V next to a pin that is labeled AC.


Effectively what im saying is... Nothing on the board is labeled 0V. But an AC pin on the board is labeled 0V in the manual.

 

[Chris-audio.com]

This is how you should wire it:

I have basically put the black to where it says AC on board, put the yellow to where it says AC on board, then i combined the red and orange and put them both to CT & CT. I have no clue if this is correct. I cant believe this problem is still so difficult for me

I have attempted to attach a picture of this.

https://drive.google.com/file/d/1Fsxf5oezSIP59UuWMqivnRPlKY508afs/view?usp=sharing