Something seems a bit 'off' with the low-tom on my recent Nava build. There is a really strong attack that just isn't present on the mid and high toms. I've uploaded a clip here: https://clyp.it/jjjh51wu Maybe it's normal behavior.
All dials are at 12 o'clock. The 4/4 beat is the low-tom, and on the 3 is mid-tom and on the 7 is high-tom, for comparison. About halfway through I tune the low-tom all the way down then all they way up.
Not sure how to diagnose this one since it kind of works. Thank you for any help.
Please tell me if this low tom sounds off
Jep, sounds wrong to me... but quite interesting!
Toms are actually synthesized from 3 OSCs each with an individual ENV, plus a NOISE that is mixed to one of the Oscillators.
It seems, that one of the Oscillators is missing in your Low Tom. So actually you should check the 3 oscillators and the 3 envelopes seperately.
Does the Decay Pot affect the sound at all? because that one only controls ENV 2...
make sure to check Tom's circuit analysis here: http://hardware.freepage.de/raf909/
Toms are actually synthesized from 3 OSCs each with an individual ENV, plus a NOISE that is mixed to one of the Oscillators.
It seems, that one of the Oscillators is missing in your Low Tom. So actually you should check the 3 oscillators and the 3 envelopes seperately.
Does the Decay Pot affect the sound at all? because that one only controls ENV 2...
make sure to check Tom's circuit analysis here: http://hardware.freepage.de/raf909/
Hey Galaxy3000 - thanks for listening to the issue and for the advice. I narrowed the issue to VCO1 not making any sound. When I checked with meter it's at 14VDC constantly, and looks like the middle pin of Q18 is at constant 14VDC.
If I could trouble you or someone for next step....
I don't see a short anywhere in the VCO1 circuit area (it's only a few components looks like)...could it be I have a bad 2SC2603-F since I'm getting that 14VDC at Q18?
If I could trouble you or someone for next step....
I don't see a short anywhere in the VCO1 circuit area (it's only a few components looks like)...could it be I have a bad 2SC2603-F since I'm getting that 14VDC at Q18?
If there is a constant voltage at collector (middle pin) of Q18 it's high likely, that there is also one at the Output of IC15B, since Q18 just passes the TRI wave comming from IC15B to the Amp Circuit (Q19). If so, then the problem is more likely within the OSC circuit (IC15A, IC15B, IC16A, IC16B, Resistors and Cap)
In your audio sample you point to a very strong attack - but to me it seems more noticable that there is a missing 'body' (which in turn may emphasize the attack phase). That's why I came up with the proposition that some signal is missing.
Do you have a scope at hand? or did you check with a voltagemeter?
If you got a scope at hand, you should check the outputs of IC15B, IC19B and IC17B. They are marked 'VCO1..3' on the board. Then ENV1..3 also marked on the board. At the end check the output of IC18A for the mix of all the former signals.
If you dont have a scope, it's very difficult to analyse... you could tune low and mid tom similarly and compare voltages between them. They use the same circuit. (However I'd advice to get a cheap USB scope!!! it's very helpful!)
In your audio sample you point to a very strong attack - but to me it seems more noticable that there is a missing 'body' (which in turn may emphasize the attack phase). That's why I came up with the proposition that some signal is missing.
Do you have a scope at hand? or did you check with a voltagemeter?
If you got a scope at hand, you should check the outputs of IC15B, IC19B and IC17B. They are marked 'VCO1..3' on the board. Then ENV1..3 also marked on the board. At the end check the output of IC18A for the mix of all the former signals.
If you dont have a scope, it's very difficult to analyse... you could tune low and mid tom similarly and compare voltages between them. They use the same circuit. (However I'd advice to get a cheap USB scope!!! it's very helpful!)
Awesome - that is so helpful, I really appreciate the information! I'm going to hunt down a scope and give it a shot and report back so others know what the issue is.
Thanks again!
Thanks again!
Just a followup in case this might help future readers.
Turned out NON_INVERTED INPUT 2 on IC15B was not connected to GND. I used machined sockets for all ICs, and there was continuity between the top of the socket and the pin on the underside. It must not have been connected to the gnd plane? I think I read there are a multiple layers to this PCB. Anyway I soldered a jumper between a GND point and PIN 5 on IC15B and that did the trick.
Unfortunately, since I was working on the board and turning it on and off during testing, I must have bumped into bootloader mode or did something to mess the atmega chip up..as now it's just a constant tone+noise, and almost all LEDs are lit. Reset doesn't work, nor does 1+3+5 bootloader mode. Nothing on the screen but solid blocks. I'll probably post a separate thread asking for tips on reprogramming it in place
Turned out NON_INVERTED INPUT 2 on IC15B was not connected to GND. I used machined sockets for all ICs, and there was continuity between the top of the socket and the pin on the underside. It must not have been connected to the gnd plane? I think I read there are a multiple layers to this PCB. Anyway I soldered a jumper between a GND point and PIN 5 on IC15B and that did the trick.
Unfortunately, since I was working on the board and turning it on and off during testing, I must have bumped into bootloader mode or did something to mess the atmega chip up..as now it's just a constant tone+noise, and almost all LEDs are lit. Reset doesn't work, nor does 1+3+5 bootloader mode. Nothing on the screen but solid blocks. I'll probably post a separate thread asking for tips on reprogramming it in place