The version C BOM for Cadet V Scaler says DNP for U3 and U4, however, the circuit is obviously needed to offset the zero referenced +/-5V to the 0-1V output. All of the circuit resistors are in the BOM.
Caps C5 and C9 for op amp U4 should also be populated.
It’s been fixed, thank you!
1v to 5v version has some errors too – the schematic and BOM don’t match. The schematic asks for TL072, but the BOM lists LM6172, which I’m hoping is correct, as I’d like to add some gain to video signals. Also, the vref. circuit looks a little strange – there’s an op-amp just connected to ground? I built some simple LM6172 amplifiers on strip without a reference and they didn’t work the way I expected.
If you are doing video to video voltage conversions then use the very high bandwidth LM6172 parts. If you are doing audio to video or video to audio conversions then the TL072 op amps are more than adequate at 1/10th the cost.
The vref circuit is not needed for 1V to 5V conversion since it is just a straight x 5 amplification. No DC offset is needed.
The vref for U1 and U2 should be tied to ground in the 1V to 5V Alt A schematic. If the schematic is correct then it ties to nothing. I dont have a Scaler board in front of me so I cant check what happens in the actual board.
I made a couple of LM6172 single-channel chiclets on strip to boost the outputs of some utility video mixers, and DUH, my circuit was biased weirdly not because of the vref (which I just had connected to GND) but because I didn’t tie the ground rails together. They work fine now. It was user error. I followed the schematic and just used LM6172 instead of TL072.
Correcting my statement on the C5 alt A schematic, 1V to 5V. U4 is used solely to provide the ground to “vref” of the 4 scaler op amps. An LM6172 is a waste of money there. I would just use a TL072 for U4 regardless of the signal speed.
Yeah, TL072, or you can probably jumper it easily! This was a case where I designed the C5 board and tried to include population options for a lot of things. Some of the alternate BOMs are a bit awkward, but it does show examples of flexible build possibilities (which was the intention.) In my case I wanted a board where I could do whatever preset amp/attenuation/offset arrangement I needed.
Back to the Alt C BOM for +/-5V to 0-1V, there is an error in the value for R7. The BOM shows 10K, it should be 20K. 10K gives only -0.5V at the Vref output, which is halved by the inverting scaler op amp stages, giving +0.25 V offset for the 1 Vpp signal. Changing R7 to 20K fixes the offset range.
Thanks @microtonal for creating this thread
For everyone else, here is a link for the C5 Scaler page to find the updated BOMs and other info files just for the sake of speed.
This is now borked with the website redesign…
@creatorlars It seems that the BOM for Alternativ C is missing in the Github Page: https://github.com/lzxindustries/documentation/tree/master/Cadet%20V%20Scaler
Im about to order components for all flavors of builds, and although i can find older versions of the BOM for Alt C, i see above that there might be errors in the old BOMS, and want to be up to date when ordering.
Can you throw an updated Bom for Alt C to the Github, Please, and thanks!
So if i want to retain as much bandwidth as possible on the +/-5v to 1v conversion (ALT C) I should just substitute the TL072 on Alt C with a LM6172.
If i understand correctly this will not require additional changes of components?
My plan is to try and see what happens when i scale video rate signals to +/- 5V and process them in my newly bought semimodular audio synth, and then scale them back to video rate. In this situation i will want to retain as much bandwidth as possible, in the event that the audio circuits have some higher bandwidth components than absolutely nessecary for audio.
I figure that even if they have only audio rate speeds, it will not make things worse using LM6172 in favor of TL072? Or will I perhaps see more high frequency noize (might be desirable or not) in the converted signal, that would otherwise be filtered by the TL072?
Trying to get my brain to process all these electroncs concepts, it so much fun! Any clarifications much appreciated!
You are unlikely to see any benefit for video rate speeds into audio rate circuits. All digital audio based circuits will be bandwidth limited, normally 15-20 KHz. Full analog path circuits are almost certainly using TL072 op amps or equivalents, not high bandwidth parts. Many circuit designs will intentionally limit the bandwidth to prevent spurious operation from ultra audio frequencies.
Net: I wouldn’t bother with LM6172s if you are interfacing through audio circuits.
Hello everyone. This is my first post on here and I just got into video synthesis. I am confused on the scaler BOM. I’m trying to build the +/- 5V to 0-1V version. I have this link https://github.com/lzxindustries/documentation/blob/master/Cadet%20V%20Scaler/Cadet%20V%20Scaler%20BOM%20Alt%20B%20%2B-5V%20to%201V.csv and I also have this link https://docs.google.com/spreadsheets/d/1WeydKarDzDZUDWkLj3EB8UL3tLL-mQJ8KeChnifF9Vs/edit#gid=1580385246 The BOM lists DNP C5 and C9 but I obviously need those if I’m placing U4 in. It leaves R11, R13, R25, R27 blank but says the value is 1.1K. Says R8 and R9 are DNP. Also it leaves R4 ,R6, R18, R20 out of the BOM completely. Can anyone that has done this build confirm this for me. Thank you.
Edit: So I found this post C5 Scaler BOMs Missing Resistors? and Lars cleared that up. But I still don’t know what value resistor to place in R4 ,R6, R18, R20 if you are building the +/- 5V to 0-1V version. 1V to 5V calls for 100K and 5V to 1V calls for 4.99K
Your second link does not have an entry for +/-5V to 1V. You seem to have confused the 1V to +/-5V column with the reverse operation.
For +/-5V to 1V, I have 10K resistors for R11, R13, R25 and R17, not DNP or 1.1K.
I have 4.99K resistors for R12, R14, R26 & R28.
For the Cadet V Scaler +/-5V to 1V operation, R4, R6, R18 & R20 should be 1.43K WHEN using 20K input resistors at R1, R3, R15 & R17. The C5 +/-5v->1V ALT B BOM on Github lists R1, R3… at 1K which is an error.
I have built and tested this version using a scope for confirmation. I need to check my entire BOM against the Github version as there are multiple errors there.
Around the +/-5V to 1V Cadet V Scaler voltage reference I have the following values, generating -1.0V output to the signal amplifying and shifting phases:
R7, R8 = 20K
R29, R31 = 10K
R30 = 15K
R10 = DNP
R9 = Wire Jumper
Again, tested and verified.
Do you mean that if you want a +/-5v to -1v conversion, you should use those values in your last post or are those additional corrected values to get +/-5v to 1v?