Ad VU meter api 312
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Rybow
Well-known member
When I did mine I used the 34mm VU meter and VU buffer kits from JLM audio. Easy peasy lemon squeezy.
djmiggymigz
Well-known member
we're back!! I Love reactivating old threads lol.
Working on the same thing here. Just want to confirm, are the 2 unused output transformer leads (Vio/Gry) what would be routed to the VU meter inputs? I'm currently looking at the JLM 34mm VU as well as their buffer circuit.
Working on the same thing here. Just want to confirm, are the 2 unused output transformer leads (Vio/Gry) what would be routed to the VU meter inputs? I'm currently looking at the JLM 34mm VU as well as their buffer circuit.
Walrus
Well-known member
Yes, you can use that spare winding, but as the transformer is a 1:1:1:1 ratio and you are joining 2 of the windings in series for the output (1:2 step up),
the spare Violet Gray winding will only show half the level of the actual output.
I've not looked, can the JLM buffer board be adjusted enough to correct for this?
the spare Violet Gray winding will only show half the level of the actual output.
I've not looked, can the JLM buffer board be adjusted enough to correct for this?
djmiggymigz
Well-known member
Hmm okay cool Yeah I'll look into that and see. I'm not sure if the buffer is just isolating the power supply to the VU or if its actually adding some gain as well. There is a TL072 in the circuit so maybe that's configured to amplify the input signal?
You don't need a vu buffer amp. API consoles did not have vu buffer amps, and neither did most consoles pre 1980, and at least half of 1980 to 1985 consoles still had no vu buffer amps.
A true vu meter will read 0vu when driven by a +4db signal through a 3.6kohm resistor. The 3.6kohm resistor buffers the signal just enough that few will notice the tiny added distortion and actually distortion from a vu meter fed by 3.6kohm resistor makes for better sound for all forms of rock and pop music but probably not legit traditional classical or jazz. It may be that the improvement in sound will only happen if the signal path is Output tyranny>>3.6kohm resistor>>vu meter. Historically the move away from true vu meters to toy meters driven by buffer (beginning around 1980) probably contributed to the apparent thinning sound (as compared to vintage gear) but it was often experienced cuz a lot of vintage consoles built correctly were still in use. As the SSL and Neve V series pushed a lot of or most of the vintage consoles out of top rated studios the sound of pop and rock music thinned out across the board and yet there were still some fat sounding recordings for various reasons such as tracked at a "B" studio that had a vintage console even though mixed at an "A" studio on SSL console.
Even though with some difficulty one can find cheap (made in china) vu meters that require the 3.6kohm resistor they may still be toys in that they will not have correct ballistics...typically the needle response will be too fast, and so distortion signature might not be the right flavor.
I'm just guessing...but if you look at this recording session (look at the gear, use of protocols) I suspect a lack of vu meter distortion....so sad in a way...japanese rockers wowed by Ed Sheeran's succe$$ (even though different genre) and they ended up with a sound of only average excitement and only faux angst compared to, from similar genre, "In the End" by Linkin' Park.
"In the end" was recorded at NRG studios in North Hollywood, Ca, circa 2000. I think they had a Neve console.
A true vu meter will read 0vu when driven by a +4db signal through a 3.6kohm resistor. The 3.6kohm resistor buffers the signal just enough that few will notice the tiny added distortion and actually distortion from a vu meter fed by 3.6kohm resistor makes for better sound for all forms of rock and pop music but probably not legit traditional classical or jazz. It may be that the improvement in sound will only happen if the signal path is Output tyranny>>3.6kohm resistor>>vu meter. Historically the move away from true vu meters to toy meters driven by buffer (beginning around 1980) probably contributed to the apparent thinning sound (as compared to vintage gear) but it was often experienced cuz a lot of vintage consoles built correctly were still in use. As the SSL and Neve V series pushed a lot of or most of the vintage consoles out of top rated studios the sound of pop and rock music thinned out across the board and yet there were still some fat sounding recordings for various reasons such as tracked at a "B" studio that had a vintage console even though mixed at an "A" studio on SSL console.
Even though with some difficulty one can find cheap (made in china) vu meters that require the 3.6kohm resistor they may still be toys in that they will not have correct ballistics...typically the needle response will be too fast, and so distortion signature might not be the right flavor.
I'm just guessing...but if you look at this recording session (look at the gear, use of protocols) I suspect a lack of vu meter distortion....so sad in a way...japanese rockers wowed by Ed Sheeran's succe$$ (even though different genre) and they ended up with a sound of only average excitement and only faux angst compared to, from similar genre, "In the End" by Linkin' Park.
"In the end" was recorded at NRG studios in North Hollywood, Ca, circa 2000. I think they had a Neve console.
djmiggymigz
Well-known member
Hmmm interesting!! How does the VU meter affect the sound of the pre? For example, where my current design/pcb layout is at, the vio/gry output tx leads are just unconnected. So how would the sound of the pre vary between that and having those leads connected to a good VU/a cheap VU??
Edit: Re-reading your post, so the VU meter itself adds some level of distortion that also makes it to the output of the preamp via the output transformer? Is the function of the VU buffer to fully isolate it then so that none of that distortion is present at the output? I suppose that could be a fun thing to experiment with! Could potentially be cool to figure out how to get some medium-heavy-ish distortion out of the VU and then have a switch to swap between the buffer/clean and no buffer/dirty! (Tho that may be too much to even fit in a 500 series build!!)
Edit: Re-reading your post, so the VU meter itself adds some level of distortion that also makes it to the output of the preamp via the output transformer? Is the function of the VU buffer to fully isolate it then so that none of that distortion is present at the output? I suppose that could be a fun thing to experiment with! Could potentially be cool to figure out how to get some medium-heavy-ish distortion out of the VU and then have a switch to swap between the buffer/clean and no buffer/dirty! (Tho that may be too much to even fit in a 500 series build!!)
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djmiggymigz
Well-known member
Okay so I've found that there's "real" VU's and then tons of cheap "not real" vu's around these days. So If I got a cheap vu from say Aliexpress, I would certainly need a buffer circuit for it to work. However if I got something like the Sifam AL15 meter (linked is the data sheet) then I wouldn't need a buffer circuit and coould run this straight from the vio/gry output tx taps?
Sifam AL series datasheet
Sifam AL series datasheet
