New Oscilloscope Day!

[jubal81]

Alright, lads. I got a Rigol DS1 102E for my birthday. And a function generator coming my way very soon.

Gonna get this shite sorted oot, good n' proper, like. 

Shazam! It's like getting glasses fir the first time. I'm kicking myself that I didn't get one years ago. Makes me want to go back and rebuild some effects that frustrated the crap out of me.

[culturejam]

Okay, so I can figure out how to export the wave as a WFM file, but I'm not seeing an option for an image format. Any ideas, Jason?


EDIT: I found it. Duh. Takes some time to get used to the UI.

[culturejam]

Here's the DuoVibe's LFO when set to the least square / most triangle sweep on the Wave pot. Neat.

[alanp]

There are normal voltage controlled oscillators, in Eurorack, and there are also complex oscillators, with all kindsa crazy modulation.

It's fun to mess around with these and not listen to a note, but just watch the waveform change endlessly.

[sturgeo]

I want to get a scope primarily for help with car projects and diagnosing sensor & PWM signals. As it needs to be relatively portable I had a look at the DSO Nano, has anyone got any experience with these? Obviously it'll need to be suitable for pedals as well, setting up delays and checking the output of TAPLFOs for example.

[Leevibe]

This will kind of explode your brain if you haven't seen it before. You should be able to get this to display on any scope with an X/Y mode. It works best with the older CRT scopes. You can learn more about it at the Jerobeam Fenderson website.

[jubal81]

Got a BTMB Maggie pedal today and right off noticed the LFO shape sounded wonky - bunched up and out of balance like a wobbly tire.


Turns out it's feeding a sharp sawtooth to the JFETs. Evens out to more of a triangle at higher speeds.

[jubal81]

Having some fun with JFET booster stage.
BF862 JFET, 17.5v supply, 11V on the drain, 1.2V bias voltage on the gate


Going up to 3.7V p-p on the input with no distortion (13.6V p-p on the output at that voltage)


When it does distort, the corners are very soft and rather unsymmetrical -- when using a cathode bypass cap. Without that cap, it's very abrupt hard clipping. Interesting!





With cathode bypass cap



No cap

[culturejam]

Cool!

[selfdestroyer]

I love this tread Jason!

[jubal81]

I love this tread Jason!

Having a blast. Breadboarding is a whole new experience - being able to see and measure things immediately vs. Do math, cross fingers, listen.


Working on an input stage for BBull mk2 and getting the headroom and gain I'm looking for while swapping in JFETs is so simple now - with no biasing necessary. I think most of the headaches we associate with JFET gain stages are from using through-hole parts with only a 9V supply. With 18V and SMD trannies it's no trouble making a VERY consistent gain stage with no need to measure drain voltages or adjust bias. I completely ditched the ROG Fetzer Valve method, since I could never hear the magic anyway.


Also getting a lot of new ideas from all this. Looked at the output of my modded G2 and saw that at low gain settings, and saw it's very soft, rounded clipping. Down the road I want to try limiting the input gain and adding a third stage to see if i can get a larger gain range with that clipping signature.

[midwayfair]

Working on an input stage for BBull mk2 and getting the headroom and gain I'm looking for while swapping in JFETs is so simple now - with no biasing necessary. I think most of the headaches we associate with JFET gain stages are from using through-hole parts with only a 9V supply.

Are the SMD JFETs more consistent than the through-hole ones? The datasheets don't seem to indicate that and as far as I know the manufacturing process is the same.

Are you just relying on the higher supply voltage to make the bias point less wiggly? The 48V stuff I've been doing still needed gate biasing, but that was to allow for really really exact stuff (particularly in microphones).

[playpunk]

Working on an input stage for BBull mk2 and getting the headroom and gain I'm looking for while swapping in JFETs is so simple now - with no biasing necessary. I think most of the headaches we associate with JFET gain stages are from using through-hole parts with only a 9V supply.

Are the SMD JFETs more consistent than the through-hole ones? The datasheets don't seem to indicate that and as far as I know the manufacturing process is the same.

Are you just relying on the higher supply voltage to make the bias point less wiggly? The 48V stuff I've been doing still needed gate biasing, but that was to allow for really really exact stuff (particularly in microphones).

I have found SMD Jfets more consistent and higher gain than the through hole JFets I have used.

[jubal81]

Working on an input stage for BBull mk2 and getting the headroom and gain I'm looking for while swapping in JFETs is so simple now - with no biasing necessary. I think most of the headaches we associate with JFET gain stages are from using through-hole parts with only a 9V supply.

Are the SMD JFETs more consistent than the through-hole ones? The datasheets don't seem to indicate that and as far as I know the manufacturing process is the same.

Are you just relying on the higher supply voltage to make the bias point less wiggly? The 48V stuff I've been doing still needed gate biasing, but that was to allow for really really exact stuff (particularly in microphones).

They're not perfectly matched, but they're far more consistent than the TH I've worked with. Part of that might be that the SMDs come on tape together (same manufacturing run?) and the TH I've always gotten were 'loosies.'


Should have explained more clearly about the biasing. I still use a bias voltage on the gate to maximize the headroom, but the device variances don't in any way necessitate adjusting the bias voltage to compensate. Actually, I've gotten very good results with GND bias on the gate, but it does sacrifice some headroom. This is where it's sweet having the scope - I can turn up the input signal until i see clipping, then adjust the gate voltage until it smooths out.


What I really liked to see was swapping out different JFETs of the same model and getting VERY consistent output and headroom.


I also experimented with parallel JFETs with good results. each one got its own source resistor, with the gates and drains tied. Saw appreciable boost in gain and supposedly it reduces noise by 3db each time you double the amount of JFETs, though I didn't test for noise. Interesting to me because I want to avoid using bypass caps on the source because I do notice the added white noise when they're present.

[galaxiex]

Awesome stuff!

Thanks so much for sharing. 

I'm gonna hafta fire up my ancient vacuum tube Telequipment CRO and do some testing....
'course its not dual trace and the accuracy is questionable.... but it's what I got....