VUPPM500 KIT Build Thread

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adalogue
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Joined: Tue Oct 19, 2021 2:05 pm

Re: VUPPM500 KIT Build Thread

Post by adalogue »

I seem to have lost one 1uF ceramic axial cap. I have a bunch of 0.1uF axial ceramic lying around for use as bypass caps, can those be substituted for the two caps under the CPU, or is 1uF required? I'm having some issues getting the unit totally calibrated, wonder if this might be influencing that.

Adam
Seattle, WA
Adam
Seattle, WA

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Joe Malone
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Re: VUPPM500 KIT Build Thread

Post by Joe Malone »

adalogue wrote:
Wed Oct 20, 2021 8:59 am
I seem to have lost one 1uF ceramic axial cap. I have a bunch of 0.1uF axial ceramic lying around for use as bypass caps, can those be substituted for the two caps under the CPU, or is 1uF required? I'm having some issues getting the unit totally calibrated, wonder if this might be influencing that.

Adam
Seattle, WA
HI Adam
Sorry I didn't get a notification for this post. That 0.1uF will be fine. What problem are you having with the calibration?
Joe :-)
JLM Audio
Capturing Audio without Injury

adalogue
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Re: VUPPM500 KIT Build Thread

Post by adalogue »

HI Adam
Sorry I didn't get a notification for this post. That 0.1uF will be fine. What problem are you having with the calibration?
Hi Joe.

I went ahead and installed the two 1uF bypass caps since I had already ordered them, I also desoldered and flipped the trimmers since I stuffed them backwards so made adjustment counter intuitive.

I went trough the cal process again and now have a new issue with the left channel not being able to adjust the peak indication. Maybe I overheated a trimmer during rework. Are schematics confidential or possible to share?

However, I think I have two legit cal challenges shown in this video for the right channel, one with peak indication not being accurate for entire range, and the other being left/right tracking through the entire range.
https://youtu.be/t-XIbsSxMOI
Adam
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Joe Malone
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Re: VUPPM500 KIT Build Thread

Post by Joe Malone »

adalogue wrote:
Mon Nov 15, 2021 2:41 am
HI Adam
Sorry I didn't get a notification for this post. That 0.1uF will be fine. What problem are you having with the calibration?
Hi Joe.

I went ahead and installed the two 1uF bypass caps since I had already ordered them, I also desoldered and flipped the trimmers since I stuffed them backwards so made adjustment counter intuitive.

I went trough the cal process again and now have a new issue with the left channel not being able to adjust the peak indication. Maybe I overheated a trimmer during rework. Are schematics confidential or possible to share?

However, I think I have two legit cal challenges shown in this video for the right channel, one with peak indication not being accurate for entire range, and the other being left/right tracking through the entire range.
https://youtu.be/t-XIbsSxMOI
Can you send me some well lit in focus photos of the top and bottom of the pcb build. It is worth cleaning the bottom of the pcb with pcb cleaner or alcohol encase the solder is a modern no clean type which are sometimes resistive. When sending in a 1kHz tone the PPM level should = the VU level. The PPM level is set by the input level pots and then the VU pots set to match PPM. The leds should track perfectly as 4 x A/D ports use the same level chart so the problem has to be in the analog section. I can send you the schematic for the analog section by reply email to the photos you send me.
Joe :-)
JLM Audio
Capturing Audio without Injury

adalogue
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Re: VUPPM500 KIT Build Thread

Post by adalogue »

Email sent, thank you Joe. The PPM is not peak value of waveform but rather highest RMS value over a period of time? I though main VU was RMS and peak VU was waveform peak, if that’s not right then it explains some of my issues. Appreciate your help.
Adam
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Joe Malone
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Re: VUPPM500 KIT Build Thread

Post by Joe Malone »

adalogue wrote:
Sun Dec 26, 2021 11:20 am
Email sent, thank you Joe. The PPM is not peak value of waveform but rather highest RMS value over a period of time? I though main VU was RMS and peak VU was waveform peak, if that’s not right then it explains some of my issues. Appreciate your help.
The VU and PPM will be the same exact level for a constant 1khz tone. PPM is peak but VU is average with 300mS attack and release not true RMS.

Email with a schematic of analog section sent
Joe :-)
JLM Audio
Capturing Audio without Injury

adalogue
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Re: VUPPM500 KIT Build Thread

Post by adalogue »

For the record this ended up being both a cold solder joint or two, both sides of meter now repsonding.
Adam
Seattle, WA

gwpt
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Re: VUPPM500 KIT Build Thread

Post by gwpt »

Hi Joe,
I just finished building the VUPPM and everything appears to be working fine :)
Now I am up to calibration, and I realised that I am unsure on how to "Send in 1k tone at 0dFS or +18dBu to"

How about this for an idea:
From reading +18dbu = 6.153 VRms

I have a bench signal generator (a siglent SDG1025) which can produce 2 outputs.
If I created 2 sin waves (180 degrees out of phase) and created a balanced output from them, and give them an vrms voltage of 6.153V would that be a valid way to calibrate?
I have a Fluke 289 True RMS multimeter to verify the output is correct


Also, I am a little unclear on the modes. The VUPPM makes sense, and I see the 2 superimposed over each other.
But I don't get 'Colour Mode 1' and 'Colour Mode 2'. They seems the same on mine (I can't see any difference)

you mention "Colour modes shows Classic VU Green, Yellow, Red with PPM peak led."
Mine appear to have 2 peaks, so is the main display a VU meter, and there is a VU Peak and a PPM as well?

Thanks
Guy

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Joe Malone
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Re: VUPPM500 KIT Build Thread

Post by Joe Malone »

gwpt wrote:
Tue Sep 20, 2022 11:10 am
Hi Joe,
I just finished building the VUPPM and everything appears to be working fine :)
Now I am up to calibration, and I realised that I am unsure on how to "Send in 1k tone at 0dFS or +18dBu to"

How about this for an idea:
From reading +18dbu = 6.153 VRms

I have a bench signal generator (a siglent SDG1025) which can produce 2 outputs.
If I created 2 sin waves (180 degrees out of phase) and created a balanced output from them, and give them an vrms voltage of 6.153V would that be a valid way to calibrate?
I have a Fluke 289 True RMS multimeter to verify the output is correct


Also, I am a little unclear on the modes. The VUPPM makes sense, and I see the 2 superimposed over each other.
But I don't get 'Colour Mode 1' and 'Colour Mode 2'. They seems the same on mine (I can't see any difference)

you mention "Colour modes shows Classic VU Green, Yellow, Red with PPM peak led."
Mine appear to have 2 peaks, so is the main display a VU meter, and there is a VU Peak and a PPM as well?

Thanks
Guy
HI Guy
Yep that volts cal idea will work fine for +18dBu but best to let me know what you will use these for. As if they are on the output of your say Appollo which clips @ +22dABu = 0dBFS then that would be the level you would use etc.

The colour modes are normal VU with PPM peak and you can also turn on and off VU peak led (press peak mode to go from peak hold to peak decay to vu peak off etc). The colour 1 & colour 2 are only different where they change to yellow at either K18 or K14 down from 0dBFS. If you have a tone on you will see this change.

Hold outside 2 buttons down until you go into test led mode and use the centre button to set one of the 3 brightness levels. Then press any outside buttonm to go back to meter.
Joe :-)
JLM Audio
Capturing Audio without Injury

gwpt
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Joined: Mon Sep 19, 2022 3:26 pm

Re: VUPPM500 KIT Build Thread

Post by gwpt »

Hi Joe,
Great, thanks for the clarification on the modes.

I was planning on having the VUPPM in my 500 case to measure gain staging along my vocal chain. So I assumed the +18dbu was the way to go.

Thinking about it I was wondering if I can just send a test signal out the sounds card to calibrate? (I have a Steinberg UR824 sound card). If I measured the vrms across one of the output (putting the output of the card to full) and it's 6.153VRms, I assume that would be the same thing?

Thanks
Guy

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Joe Malone
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Re: VUPPM500 KIT Build Thread

Post by Joe Malone »

gwpt wrote:
Tue Sep 20, 2022 12:26 pm
Hi Joe,
Great, thanks for the clarification on the modes.

I was planning on having the VUPPM in my 500 case to measure gain staging along my vocal chain. So I assumed the +18dbu was the way to go.

Thinking about it I was wondering if I can just send a test signal out the sounds card to calibrate? (I have a Steinberg UR824 sound card). If I measured the vrms across one of the output (putting the output of the card to full) and it's 6.153VRms, I assume that would be the same thing?

Thanks
Guy
The line outs level of Steinberg UR824 is 0dBFS = +18dBu. So +18dBu is the way to go :-)
Joe :-)
JLM Audio
Capturing Audio without Injury

gwpt
Posts: 4
Joined: Mon Sep 19, 2022 3:26 pm

Re: VUPPM500 KIT Build Thread

Post by gwpt »

Hi Joe,
sorry for all the questions, but this is the first time I am trying to calibrate something properly like this!

I tried run a 1kz 0db sine wave out of my ur824 which I got here: https://virtualzeroaudio.com/pages/1khz-sine-wave
it states that it's -3dbFS

So my assumption was, that if I played that with the sound card (volume on max), it would be +18dbu (the max out) -3 (the -3dbFS of the file) = +15dbu

When I measure the output I'm getting 4.7341V (I measured between the Tip and the Sleeve), which my meter says is 13.55dbv which I converted to dbu = 15.77dbu close but a bit out!

Does that seem correct? As in the output is 15.77dbu and could calibrate to that?
Is measuring between the Tip and Sleeve the correct way to measure the output for a balanced signal? (or it it reduced by 3db as I'm only measuring 'half' the signlal)
Is a sin the best wave to use?
I fear I may have a step wrong in there somewhere, so would really appreciate it if you could confirm.
Thanks
Guy

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Joe Malone
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Re: VUPPM500 KIT Build Thread

Post by Joe Malone »

gwpt wrote:
Tue Sep 20, 2022 6:04 pm
Hi Joe,
sorry for all the questions, but this is the first time I am trying to calibrate something properly like this!

I tried run a 1kz 0db sine wave out of my ur824 which I got here: https://virtualzeroaudio.com/pages/1khz-sine-wave
it states that it's -3dbFS

So my assumption was, that if I played that with the sound card (volume on max), it would be +18dbu (the max out) -3 (the -3dbFS of the file) = +15dbu

When I measure the output I'm getting 4.7341V (I measured between the Tip and the Sleeve), which my meter says is 13.55dbv which I converted to dbu = 15.77dbu close but a bit out!

Does that seem correct? As in the output is 15.77dbu and could calibrate to that?
Is measuring between the Tip and Sleeve the correct way to measure the output for a balanced signal? (or it it reduced by 3db as I'm only measuring 'half' the signlal)
Is a sin the best wave to use?
I fear I may have a step wrong in there somewhere, so would really appreciate it if you could confirm.
Thanks
Guy
I presume the output is TRS so if measuring Tip and sleeve it would only be half the actual voltage the Tip to Ring balance out is outputting ? But I couldn’t find much info in the UR824

If you are running windows use the tone gen and meter software mentioned in the audio software post at the beginning of the forum as it is free
Joe :-)
JLM Audio
Capturing Audio without Injury

gwpt
Posts: 4
Joined: Mon Sep 19, 2022 3:26 pm

Re: VUPPM500 KIT Build Thread

Post by gwpt »

Great, thanks Joe
That app made it really easy :)

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