Breadboard a Rat
- Thread starter fig
- Start date
fig
Village Idiot
I'd build out the circuit and see how they sound.My 4 LM308Ns from GuitarPCB read around 2.38KΩ between pins 1 and 5.
My LM308AH metal cans read over 8MΩ.
fig
Village Idiot
I brought out the nice tableware for you folks.
jeffwhitfield
Well-known member
fig
Village Idiot
100Hz sine sounds close on most, but I've been listening to it all day so everything sounds mushy. We'll see how they look to the scope, plus I'll run/record a loop through each and post them. I'll use the production opamp for testing the clipping options and the bass mod.
I'm also going to make a switch bank for the breadboard.
I'm also going to make a switch bank for the breadboard.
vigilante398
Authorized Vendor
When I build for myself I use metal can LM308AH because mojo. When I build for customers I use OP07 because I can get them in SMD package and pick-and-placed. Plus they're cheeeaaaaaap.
fig
Village Idiot
Update - I've done quite a bit more undocumented tinkering and swapping, mostly to get my bearings on how to best demonstrate variations within the option matrix [op-amp/clipping/bass mod]. Rather than audition every possible combination, I'll choose an op-amp, then match the clipping to my personal preference. For the bass mod I will use both my chosen configuration & stock (and any others you'd like me to try Joe). My audio interface died..probably of loneliness since I never used it..so I have a replacement incoming for the comparison samples. I have some cool scope shots to share as well.
Harry Klippton
Well-known member
What interface died and what did you get as a replacement
fig
Village Idiot
I'm still putzing with the comparisons, but hands down the LM308 sounds better than the other dozen or so auditioned [insert subjective harumph]. The circuit on my breadboard as is below is how I'll build it out (minus the zif and superfluous wiring). I'll get some measurements, but the diodes are black glass OA7s and bring quite a punchy growl to the table. Mica and C280s for tone-jo.
Joe, I ran into a delay on your request, but will circle back to it.
There's phaser island in the foreground....which is also the reason for the delay...LOL
Joe, I ran into a delay on your request, but will circle back to it.
There's phaser island in the foreground....which is also the reason for the delay...LOL
Paradox916
Well-known member
Punchy growl?! Phaser island?! You have my attention now.... tell me more about these magical OA7s you speak of. How do they compare to the 1N34As?
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fig
Village Idiot
@Paradox916
Apologies for the delay. To answer your question; the Vf range of the 2 are fairly close in the samples I tested (within 10mV), but the curve response seems quite different.
Using my signal gen. and scope together, I ran a ramp wave into the diode (DUT) and connected channel 1 probe between the input and diode and set the measurement to amperage. Channel 2 was connected between the other pin of the diode and common to make a simple XY curve trace. The sampling memory depth is 7m so it's a thicker, 3D sort of trace.
Here is a 1N34A.
...the waveform distortion..
Now the OA7...
...and it's waveform..
..and a 1N4148..
..you guessed it...
I'm still planning to put together some audio samples but I've been otherwise occupied of late. These visuals are helpful to demonstrate a difference, but for our purposes matching those squiggles to audible recognition would go a long way.
"Phaser Island" is just a MXR 90 I want to use to determine a lower threshold for Vgs-off, no connection to this project. This may already be common knowledge amongst those in the know, but I operate outside that magical bubble so empirical evidence accompanied by input from youse guys is king.
Edit: I uploaded the square wave response images rather than the saw waves...the other waveforms displayed respectively.
Apologies for the delay. To answer your question; the Vf range of the 2 are fairly close in the samples I tested (within 10mV), but the curve response seems quite different.
Using my signal gen. and scope together, I ran a ramp wave into the diode (DUT) and connected channel 1 probe between the input and diode and set the measurement to amperage. Channel 2 was connected between the other pin of the diode and common to make a simple XY curve trace. The sampling memory depth is 7m so it's a thicker, 3D sort of trace.
Here is a 1N34A.
...the waveform distortion..
Now the OA7...
...and it's waveform..
..and a 1N4148..
..you guessed it...
I'm still planning to put together some audio samples but I've been otherwise occupied of late. These visuals are helpful to demonstrate a difference, but for our purposes matching those squiggles to audible recognition would go a long way.
"Phaser Island" is just a MXR 90 I want to use to determine a lower threshold for Vgs-off, no connection to this project. This may already be common knowledge amongst those in the know, but I operate outside that magical bubble so empirical evidence accompanied by input from youse guys is king.
Edit: I uploaded the square wave response images rather than the saw waves...the other waveforms displayed respectively.
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Paradox916
Well-known member
That’s interesting... just by the wave form it looks as if the OA7 are some where between the 1n34a and the 1n4148... I don’t know exactly what I’m looking at but now It’s m even more curious. Thanks for doing that!
fig
Village Idiot
Okay Joe, yer up.
I had to redo the switch as I misread the blurb the first time and used an on-on-on-and-on-indefinitely instead of an on again-off again-on again type.
The 4u7 option is the green EC, and the 10u a tantalum.
You might notice the absence of the clipping diodes...I removed them for this demo....btw this damn thing is LOUD without them. I have a little Roland MG-10 at the end of the bench I use for audibles, and had it set for a clipped rat...yikes!
Anyway, so I ran a squiggly line through the circuit - 80Hz 1Vpp sine
The first view is the stock value setting (center off)
Next is the 4u7 option...more pronounced hump..
...and the 10u option...look more like a Fedora..
Once again, sound clips will be even more useful but I hope this gives you an idea...The 10u side begins to clip @ 65Hz as seen here
Thanks for reading! If you spot an error or have feedback I'd love to know!
Edit: The 10u side begins clipping @ ~98Hz...
Second edit (due to duhhhh): The first edit should read the 4u7 side begins clipping @ ~98Hz.
I had to redo the switch as I misread the blurb the first time and used an on-on-on-and-on-indefinitely instead of an on again-off again-on again type.
The 4u7 option is the green EC, and the 10u a tantalum.
You might notice the absence of the clipping diodes...I removed them for this demo....btw this damn thing is LOUD without them. I have a little Roland MG-10 at the end of the bench I use for audibles, and had it set for a clipped rat...yikes!
Anyway, so I ran a squiggly line through the circuit - 80Hz 1Vpp sine
The first view is the stock value setting (center off)
Next is the 4u7 option...more pronounced hump..
...and the 10u option...look more like a Fedora..
Once again, sound clips will be even more useful but I hope this gives you an idea...The 10u side begins to clip @ 65Hz as seen here
Thanks for reading! If you spot an error or have feedback I'd love to know!
Edit: The 10u side begins clipping @ ~98Hz...
Second edit (due to duhhhh): The first edit should read the 4u7 side begins clipping @ ~98Hz.
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peccary
Well-known member
Thanks, Fig. I have to admit that I'm not sure what I'm looking at here but I am now picturing a fedora wearing rat on the front of the enclosure.Okay Joe, yer up.
I had to redo the switch as I misread the blurb the first time and used an on-on-on-and-on-indefinitely instead of an on again-off again-on again type.
The 4u7 option is the green EC, and the 10u a tantalum.
You might notice the absence of the clipping diodes...I removed them for this demo....btw this damn thing is LOUD without them. I have a little Roland MG-10 at the end of the bench I use for audibles, and had it set for a clipped rat...yikes!
Anyway, so I ran a squiggly line through the circuit - 80Hz 1Vpp sine
The first view is the stock value setting (center off)
Next is the 4u7 option...more pronounced hump..
...and the 10u option...look more like a Fedora..
Once again, sound clips will be even more useful but I hope this gives you an idea...The 10u side begins to clip @ 65Hz as seen here
Thanks for reading! If you spot an error or have feedback I'd love to know!
Edit: The 10u side begins clipping @ ~98Hz...
I'm thinking of getting myself a cheapie scope just to be able to see what I'm hearing, I feel like that experience would be really helpful. Being able to see the clipping is pretty cool.
How'd your Ric sound through it?
fig
Village Idiot
I haven't gotten to play through it with the mod yet, but it's on my fig-do list.
How's your vision? If a smaller screen is not an issue I'll send you this Hantek 2D72. It's a 2-channel scope, a signal gen and DMM all in a handheld. The bandwidth is fine for the display but pushing it to an external via the USB port introduces a good bit of lag.
Something that might be a fun/easy mod while on the breadboard. A pair of red led soft clippers changes the feel at higher gain levels. You get less of the woofy fuzz stuff and a tighter clearer sound by avoiding op amp clipping. the op amp clipping is super cool in its own way, this is just a simple way to get a feel for how the op amp clipping (before the hard clipping diodes) is affecting the sound.
Also, in my build a put the ruetz sweep mod, which I almost always back off a bit compared to stock. Just a 1k pot in series with the 47R.
Also, in my build a put the ruetz sweep mod, which I almost always back off a bit compared to stock. Just a 1k pot in series with the 47R.
fig
Village Idiot
I'll give that a shot, thanks!
I played around with the pedal controls and found a nice spot to demonstrate the bass mod a bit clearer...
Unfortunately, sharing the GIF is more difficult than creating it, LOL.
