From Brian Willoughby Sent Thu, Feb 15th 2018, 23:58
From Brian Willoughby Sent Thu, Feb 15th 2018, 23:58
Very interesting! It=E2=80=99s an all-too-common design error to plug a 5 V DAC into a = system that can=E2=80=99t actually deliver 5 V because the supply rails = are running at exactly 5 V, too. There needs to be some headroom. You might be able to fix this by replacing the op-amps in the Avalon = Bassline with a pin-compatible alternative that has better Rail-to-Rail = performance. This might be tricky for a couple of reasons. First, there = are many op-amp parameters that might change, so getting higher Voltages = may come at a sacrifice of some other performance. Second, this thing is = probably SMD, and you might not have heated tweezers. I still haven=E2=80=99t looked at the TB303 schematic, but does anyone = know whether its supply runs at more than 5 V? The 85 mV limit you=E2=80=99re seeing with the Avalon Bassline looks = suspiciously like an op-amp chip limit. But be warned that even the best = RR op-amps have a non-zero limit. Brian On Feb 15, 2018, at 3:37 PM, skkatter <xxxxxxxx@xxxxx.xxx> wrote: > I checked the Avalon Bassline CV out, 4.915 volts is the highest it = will go. The TT303's highest is 5 volts. >=20 > And here's a short jam with it for good measure: = https://youtu.be/Hcf4eY5klf8 >=20 > -Stephen >=20 > On 14 February 2018 at 08:29, Brian Willoughby = <xxxxxx@xxxxxxxxxxxx.xxx> wrote: >> I guess that explains it, then. If it can=E2=80=99t produce as high a = CV as the TB303, then it can=E2=80=99t sequence the same high notes. >>=20 >> I=E2=80=99ll be curious to see whether you find that 5 V is the = limit. This sort of thing is the reason why I=E2=80=99ve passed over = many MIDI-to-CV products that were limited to 5 V. Sure, not every VCO = has more than 5 octaves of range, but those that do deserve to flex = their muscles. >>=20 >> My new question is why the software emulations had the same limit. = Maybe there=E2=80=99s a completely separate reason and it=E2=80=99s just = a coincidence. >>=20 >> Next time I have a minute, I hope to look over the TB303 schematics = to see how they handle CV generation from the sequencer. >>=20 >> Brian >>=20 >>=20 >> On Feb 14, 2018, at 12:14 AM, skkatter <xxxxxxxx@xxxxx.xxx> wrote: >> > Heya Brian, >> > >> > Yes the Avalon does have CV and gate output from its internal >> > sequencer. I plugged it into one of the SEMs I happened to have = lying >> > around and its CV out also can't output the highest note. I'll be = able >> > to check the actual voltage coming out of it with a multimeter this >> > evening after work, mine is currently hidden in a box somewhere = under >> > five hundred other boxes as I just moved house. :/ >> > >> > -Stephen >> > >> > On 14 February 2018 at 01:15, Brian Willoughby = <xxxxxx@xxxxxxxxxxxx.xxx> wrote: >> >> Does the Avalon have CV output from its internal sequencer? >> >> >> >> If so, measure the CV output to see if it matches the TB303 output = or if the Avalon CV generator is limited. You could either use a Volt = meter or just plug it into a known, good VCO (other than the Avalon, = which is clearly suspect). >> >> >> >> My untested hunch is that the Avalon VCO is totally analog and can = handle the high CV and reproduce the pitch, but the internal CV = generation can=E2=80=99t actually recreate the same voltages that the = TB303 is generating. Not sure why unless it=E2=80=99s going above 5 V, = which is a typical limit for a DAC without calibrated gain. A VCO = wouldn=E2=80=99t necessarily have a 5 V limit on its 1V/oct CV input, = especially not if it=E2=80=99s running on +/-10 V or higher rails. >> >> >> >> Brian >> >> >> >> On Feb 13, 2018, at 1:33 PM, skkatter <xxxxxxxx@xxxxx.xxx> wrote: >> >>> TB303 and TT303 can play the highest C transposed up fine with = their >> >>> internal sequencers, Avalon cannot, however Avalon *can* play the = note >> >>> when you bypass it's internal sequencer and play it via CV/Gate = from >> >>> the TB303. Can anybody else re-create this behaviour? I recorded = a >> >>> little video to demonstrate: >> >>> >> >>> https://youtu.be/0Gbm-U1PZ7A >> >>> >> >>> -Stephen >> >>> >> >>> On 13 February 2018 at 21:31, DJ Maytag <xxxxxxxx@xxxxxxxx.xxx> = wrote: >> >>>> Even some software emulations had that limit, and it would = transpose an >> >>>> attempt at transposing E3 to E4 into C4 (its upper limit) = instead. >> >>>> >> >>>> On Tue, Feb 13, 2018 at 3:06 PM Computer Controlled = <xxxxxxx@xxxxx.xxx> wrote: >> >>>>> >> >>>>> Your past the limits of what it will play. I believe it=E2=80=99= s a 3 octave >> >>>>> limit. >> >>>>> >> >>>>> On Tue, Feb 13, 2018 at 10:12 AM, skkatter <xxxxxxxx@xxxxx.xxx> = wrote: >> >>>>>> Avalon users! Sorry for the spam, have a quick technical = question. >> >>>>>> >> >>>>>> On my Avalon if I program a pattern with the upper C, and have = that >> >>>>>> upper C up one octave (or lower C up two octaves) it plays = fine. >> >>>>>> However, if I then transpose that pattern up, the upper C cuts = out, >> >>>>>> all the other notes will play fine however. >> >>>>>> >> >>>>>> Is this normal Avalon Bassline behaviour? Because it isn't = normal >> >>>>>> TB303 behaviour. >> >>>>>> >> >>>>>> Thanks, >> >>>>>> Stephen 303 problems today.