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Building your own stompbox / Re: Are BBD chips considered Analog or Digital, or even neither or both?
« Last post by Rob Strand on Today at 07:39:14 PM »
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I'm a programming kind of guy. I don't think there's anything magical about analog. There's nothing that you *can't* duplicate with a DSP. The question is only whether we have decent algorithms for it, how much effort it takes, and whether it's worth the computing power or cost
100% agree.    I'm fundamentally an analog person but I do DSP.   I much prefer DSP processing to analog.   A few lines of code is like a whole messy circuit.   You can change the whole design in a few short space of time.   Even switch between two designs.

There's plenty of traps in DSP.   You might think you are getting the same result as analog but you aren't.    The thread Mark Hammer started a year or so ago about sample rates and signal processing (especially clipping) exposes quite a few areas when evil can sneak in.
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Building your own stompbox / Re: Harmonic Percolator - Perfecting the Circuit
« Last post by ManicStrat1982 on Today at 07:27:16 PM »
Quote from: garcho on Today at 05:54:01 PM
and never with clipping diodes.
I'll have to try the one on my breadboard without clipping diodes. I've read a lot about that, and people seem to like it.  Also, I tried a couple 2n404 in mine, but I didn't have any luck....even with the 2n3565. it has some different specs than the 2n404a (which I'll have to order)
Right now I've got good results with a MP16b with hfe of 63 and 110ua of leakage, and a 2n2222a with hfe of 256. I haven't tried my 2n3565's in my bread boarded circuit yet...that will be next.
Have you ever tried adding a diode to ground on your input after the 100pf capacitor... like on version 2 of the Hermida  schematic?
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Building your own stompbox / Re: Are BBD chips considered Analog or Digital, or even neither or both?
« Last post by ElectricDruid on Today at 07:15:55 PM »
Ok, ok, you asked for it. I'm a fish, and when I see a fat juicy worm on the hook, I can't help but take the bait ;)

I'm a programming kind of guy. I don't think there's anything magical about analog. There's nothing that you *can't* duplicate with a DSP. The question is only whether we have decent algorithms for it, how much effort it takes, and whether it's worth the computing power or cost. In these days of cheap 32-bit chips, there's a ton of evidence already arrived in the market that all of these things are possible. Ask Strymon and TC Electronic about their sales and you'll get your answer. You can get digital versions of tape delays, BBDs, spring reverbs, plate reverbs, reverb rooms, etc etc etc. Obviously, it can be done well or done badly, but I think it's pretty clear by now that it's all *possible*, and there are plenty of examples on the market that not only get the sound, but lower the noise floor into the bargain.

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Building your own stompbox / Re: Amplifier Design - A Documentation
« Last post by Rob Strand on Today at 06:56:50 PM »
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What would you expect this to do Rob?

I imagined nothing (all things being well) besides dropping the diode fv from the pre-amp supply but adding it as shown caused the amp to oscillate independent of the volume control and made an almighty racket until the power was cut.
You might need to add the 100uF across the power rail on the preamp side.   You can also change the diode to a 100ohm resistor (no diode at all).   The resistor is better as you can keep increasing the value to reduce the preamp supply changes.

The idea is to prevent or at least reduce motorboating.

Suppose you have a preamp with a 12V supply and the transistor collectors a biased mid-supply to 6V.  Now you change the supply to 10V.   The collectors will bias to a lower voltage say 5V (just for arguments sake).  Now imagine continually and rapidly adjusting the power back and forth between 10V and 12V  the change in the bias point on the transistor collectors looks like signal.   That signal will be amplified by the power amp.

When the power amp clips the regulator current-limits and that causes the output voltage of the regulator to drop.    The drop in supply changes the biasing of the transistor preamp.   That drop in supply looks like a signal.  The power amp amplifies the signal but the signal causes the supply to drop or rises.   So you end up with a feedback loop where the power amp feeds back signal to the preamp via the power supply and it oscillates.

By putting a diode and cap, or a resistor and cap on the power supply the power supply changes are reduced.  Hopefully to the point where it cannot sustain oscillations.

The ultimate decoupling of the power supplies is to have a separate regulator for the preamp.    *But*  that's only true if the input supply voltage does not drop too low when the power amp clips.   If the input power rail drops too much the preamp regulator will not regulate.   You will get back the same problem you had before where the preamp power rail is dropping because of what is happening at the power amp.

Anyway, the fact you are seeing a change in behaviour is a good indication we are on the right track.

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Building your own stompbox / Re: Are BBD chips considered Analog or Digital, or even neither or both?
« Last post by Rob Strand on Today at 06:30:39 PM »
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The ADC samples an analog voltage that has already been quantized.
My argument is soon as you have an ADC, the process of taking the analog signal and converting it to a number, it becomes digital.

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If we are using a 3v peak-peak audio signal, then each sample taken by the 24-bit converter will be within plus or minus 0.000000089407 volt if we have adjusted it to make max use of the bit depth. An error, but a very tiny one. In fact, because of the degradation in the 2932 remaining BBD stages after the first tap, Out1 (bbd) will be less accurate than Out2 (digital). Does this make a difference? Can you hear the difference? 
That part falls is comparing Analog and Digital processing ...  and we all all know where that leads.

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Building your own stompbox / Re: Needing help understanding filters in Delays Circuits - Rebote Delay 2.5
« Last post by percyhornickel on Today at 06:25:54 PM »
You are right, I have tested my DIY ts808 with TL072 instead 4558, my rats with OP07 and LM308N / 308A...     ....and the conclusion is...   ...we are not Vai or Satriani.

Only one advice, chinese opamps often are the same with different labels, happen to me with opamps, NPN transtistors labeled like Jfets, etc...       .....yes I am talking to you AliExpress!!!!!.


Saludos y gracias!!
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Building your own stompbox / Re: Needing help understanding filters in Delays Circuits - Rebote Delay 2.5
« Last post by ElectricDruid on Today at 06:08:33 PM »
Quote from: percyhornickel on Today at 05:37:27 PM
What do you think about using other opamp (4558) intead TL072 in this circuit?

Makes no practical difference. You *might* see a measurable change with good equipment, but I seriously doubt you'd hear it enough to identify it in a blind test. The times when you *might* hear differences between op-amps (and I'm not convinced that even then they're as big a deal as people make out) is when the op-amps are pushed to their limits. In this situation, for some basic filtering, pretty much any part that can do the job is fine and you won't know.

Use whatever you've got or like the best. People make a lot of fuss about stuff like this, but then you discover they're trying to sell some boutique pedal with "magic" parts in it for three times what a normal build costs! ;)
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Building your own stompbox / Re: Are BBD chips considered Analog or Digital, or even neither or both?
« Last post by amz-fx on Today at 06:04:46 PM »
Quote from: ElectricDruid on Today at 05:56:43 PM
I think you might have opened a can marked "Worms, size: extra large", Jack.

Good luck...;)

Hahahaha...  just some thoughts for discussion. I would like to know what everyone thinks is contributing to the analog nature of BBDs. What makes the sound and can it be duplicated with DSP?

You have used some of them. What do you think?

Best regards, Jack
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Building your own stompbox / Re: Klon Clone Kit - Diagnostics
« Last post by iainpunk on Today at 06:03:10 PM »
Quote from: idy on Today at 01:13:01 PM
welcome to the forum!

People will want to see the build doc, so we can stay things like "R16" or "C12."

The klon mixes a buffered signal with the overdrive signal. Maybe you are getting the OD but it's not reaching the mixer stage. For this you want to signal trace (instrument cable with capacitor attached.)

Also taking voltages for the ICs is a good place to start.
or build and use an audio probe to trace the signal:


cheers
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Building your own stompbox / Re: Q3c Bias Point - RDV Silicon MkII
« Last post by iainpunk on Today at 05:58:25 PM »
Quote from: Gus on Today at 04:53:23 AM
Try Si power transistors
I have built treble booster and fuzz circuits with Si power transistors and posted about using Si power transistors for sometime at this forum
people might be sick of hearing this line coming from me:
"I recommend the BD139/BD140 power transistors", they sound really good to my ears, in most low gain discrete circuits, it has something just magic going on.
they have gains from 25 to 150, so checking the gain is crucial, you can opt for buying a bulk and sorting them in gain ranges yourself

cheers
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