Let's have a chat about Silicon clipping diodes

JakeAC5253 · Post by **JakeAC5253** » 08 Feb 2011, 04:45

I'm tone chasing as a few of you may know, and I've tried a number of different diodes in a few builds, but I thought it would be interesting to get a few recommendations. Here's what I've found.

1N4148 - Great for when lots of 'crunch' is desired, high gain.
1N4150 - Like the 4148, but less top end it seems, a bit darker.
1N916 - Supposedly* the stock SD-1 diodes. Pretty smooth and dynamic (it's the rest of the circuit that sounds like junk)
1N914 - Supposedly the clipping diodes of the Maxon OD808, but I've never tried swapped them. My inclination is to say smooth sounding like the 1N916.

* - Not sure really what the stock SD-1's clipping diodes are. I've searched high and low and found one reference to 1N916's, but nothing further to confirm or deny.

Anything else worth mentioning? Other types? Conflicting experiences? Anything you have, post it up and I'll refer back to this thread later.

Tonetweaker · Post by **Tonetweaker** » 08 Feb 2011, 05:11

JakeAC5253 wrote:1N916 - Supposedly* the stock SD-1 diodes. Pretty smooth and dynamic (it's the rest of the circuit that sounds like junk)

Here's a schematic I had for the SD-1. Not sure where I got it, though, so I can't say for sure it's 100% accurate... It has some 1N916s in the drive section of the circuit.

Hope this helps...

Cheers...
Steve

Hides-His-Eyes · Post by **Hides-His-Eyes** » 08 Feb 2011, 09:35

I do not think a diode can sound "smooth and dynamic".

1n914 and 1n4148 are the same part I believe.

fosnal1950 · Post by **fosnal1950** » 08 Feb 2011, 16:58

I do not think a diode can sound "smooth and dynamic".

+1

I wouldn't call a voltage swing between 0 and 0.5 volts dynamic.

JakeAC5253 · Post by **JakeAC5253** » 08 Feb 2011, 17:04

Tonetweaker wrote:
JakeAC5253 wrote:1N916 - Supposedly* the stock SD-1 diodes. Pretty smooth and dynamic (it's the rest of the circuit that sounds like junk)
Here's a schematic I had for the SD-1. Not sure where I got it, though, so I can't say for sure it's 100% accurate... It has some 1N916s in the drive section of the circuit.

Boss-SD1SuperDistorsion.gif
Hope this helps...

Cheers...
Steve

Yeah, that's the one lead that I have. Nobody else seems to be talking about it

Hides-His-Eyes wrote:I do not think a diode can sound "smooth and dynamic".

1n914 and 1n4148 are the same part I believe.

Well, the compression curve matters as well, which means that relatively speaking, one diode could be more dynamic than another diode with the same Vf. But in this case, it's my bad because I forgot that I had the diodes stacked and was using that as a basis for comparison.

billonious · Post by **billonious** » 08 Feb 2011, 17:24

I am not 100% sure, but all these small-signal silicon diodes have the same technology, the same effect on clipping audio and almost the same I/Vf curves. If there is difference between them, I don't think it would be audible. To get a softer clipping (or compression), you need diodes slower than the silicon ones (such as germaniums). But you can emulate soft-clipping with Si, when adding a resistor in series with the diode.

JakeAC5253 · Post by **JakeAC5253** » 08 Feb 2011, 17:34

billonious wrote:I am not 100% sure, but these small-signal silicon diodes have almost the same outcome on clipping audio signals.

My experience has been different. I took one of the stock diodes out of the SD-1 and put a 1N4148 in its place and the resulting sound was awkward sounding. Put the stock diode back in and it's smooth again. (I also just remembered that this was one of the reasons for saying that the 1N916's were smooth and dynamic)

billonious · Post by **billonious** » 08 Feb 2011, 17:47

JakeAC5253 wrote: My experience has been different. I took one of the stock diodes out of the SD-1 and put a 1N4148 in its place and the resulting sound was awkward sounding. Put the stock diode back in and it's smooth again. (I also just remembered that this was one of the reasons for saying that the 1N916's were smooth and dynamic)

Ok, if it is from your experience, I can't disagree

. Sometimes, such "listening tests" prove that technical specifications have very wide tolerances. You see, effects for musicians are not only electronic equations as far as psychoacoustic factors take over

DrNomis · Post by **DrNomis** » 08 Feb 2011, 19:55

I tried a couple of back to back small-signal Shottky Diodes once,I set them up on my breadboard,and used them to clip the signal from my signal generator,i half-expected to see a squarewave on the Oscilloscope screen,but instead I saw a gently rounded waveform,similar to what you get with two back-to-back germanium small-signal diodes,the Shottky diodes I used had a .3V forward-bias voltage,but they were silicon types....

roseblood11 · Post by **roseblood11** » 08 Feb 2011, 19:58

The tolerances are much bigger than the differences between two types...

JakeAC5253 · Post by **JakeAC5253** » 08 Feb 2011, 20:38

Not to toot my own horn, but I've been a sound engineer for a few years and I've conditioned myself to listen in an unbiased manner. The 1N4148 in line with the 1N916 (or whatever it was) sounded weird. I would have much preferred if it didn't, but it did.

roseblood11 wrote:The tolerances are much bigger than the differences between two types...

I have a bag of 1N4148's. Should I just use them wherever a Silicon diode with ~.6-.7 Vf is acceptable and not worry about playing around with other types?

Hides-His-Eyes · Post by **Hides-His-Eyes** » 08 Feb 2011, 20:42

JakeAC5253 wrote:Not to toot my own horn, but I've been a sound engineer for a few years and I've conditioned myself to listen in an unbiased manner.

Not to be a dick, but what the hell does that mean? How does one 'learn' to listen unbiasedly?

You account for bias by double blinding your test, not by pretending you're immune to inescapable failings of the human response to sound.

JakeAC5253 · Post by **JakeAC5253** » 08 Feb 2011, 20:47

Hides-His-Eyes wrote:
JakeAC5253 wrote:Not to toot my own horn, but I've been a sound engineer for a few years and I've conditioned myself to listen in an unbiased manner.
Not to be a dick, but what the hell does that mean? How does one 'learn' to listen unbiasedly?

You account for bias by double blinding your test, not by pretending you're immune to inescapable failings of the human response to sound.

Practice. Plus another set of ears doesn't hurt.

I'm friends with other sound engineers like me who are willing to lend an ear, and I often make A/B comparisons without telling them anything about them. When what they tell me they heard individually, matches what I already thought that I heard time after time, I am an unbiased listener.

JakeAC5253 · Post by **JakeAC5253** » 08 Feb 2011, 21:00

DrNomis wrote:I tried a couple of back to back small-signal Shottky Diodes once,I set them up on my breadboard,and used them to clip the signal from my signal generator,i half-expected to see a squarewave on the Oscilloscope screen,but instead I saw a gently rounded waveform,similar to what you get with two back-to-back germanium small-signal diodes,the Shottky diodes I used had a .3V forward-bias voltage,but they were silicon types....

That's pretty neat, thanks. IIRC, Schottky diodes are available in a range of different Vf right? Similar to the way Zeners are?

earthtonesaudio · Post by **earthtonesaudio** » 08 Feb 2011, 21:51

If you jellybean various semiconductor diode types into a given circuit, they will sound different.

However, by tweaking the levels (current and voltage) going into the clippers, and adjusting the gain post-clipping, they can be made to sound very much the same.

DrNomis · Post by **DrNomis** » 09 Feb 2011, 01:26

JakeAC5253 wrote:
DrNomis wrote:I tried a couple of back to back small-signal Shottky Diodes once,I set them up on my breadboard,and used them to clip the signal from my signal generator,i half-expected to see a squarewave on the Oscilloscope screen,but instead I saw a gently rounded waveform,similar to what you get with two back-to-back germanium small-signal diodes,the Shottky diodes I used had a .3V forward-bias voltage,but they were silicon types....
That's pretty neat, thanks. IIRC, Schottky diodes are available in a range of different Vf right? Similar to the way Zeners are?

I'd imagine so,you could even try using two back-to-back Zener diodes too....

Since the B-E junction of Bipolar Transistors are effectively diodes,you could even use these as well,they happen to have an exponental turn-on characteristic,this was employed in Analog Synthesizer Exponential Converter circuits to convert the linear response of monophonic keyboards to an exponential current change which was used to control Voltage Controlled Oscillators,so that for each 1-Volt increase in control voltage,the VCO frequency doubled.....

I have done some experiments using the B-E junction of bipolar transistors as diodes,the resulting waveforms are rounded rather than sharply clipped....

So,if you are very low,or almost out of small-signal diodes,and you need two for a clipping circuit,and you have lots of bipolar transistors,try using them as diode substitutes....

I'm even wondering if it is possible to use the gate and source of a Fet in a clipping circuit...

JakeAC5253 · Post by **JakeAC5253** » 09 Feb 2011, 02:20

DrNomis wrote:I'm even wondering if it is possible to use the gate and source of a Fet in a clipping circuit...

I'm not sure about FETs, but I know that the Fulltone OCD uses a MOSFET as a clipper

DrNomis · Post by **DrNomis** » 09 Feb 2011, 02:52

I was intregued enough about using back-to-back J-Fets,that I decided to do a quick experiment just to see if it actually worked,and....well,see for yourself,here is the evidence.....

Note that in the Circuit,Q2's Gate is also connected to circuit ground,I just forgot to put a dot where the lines intersect....

blackbunny · Post by **blackbunny** » 09 Feb 2011, 03:17

JakeAC5253 wrote:* - Not sure really what the stock SD-1's clipping diodes are. I've searched high and low and found one reference to 1N916's, but nothing further to confirm or deny.

The stock diodes in the early MIJ SD-1 (and the OD-1 and the early MIJ DS-1) were 1S2473 or 1S1588, which are fast-recovery 35-40V general purpose small signal transistors. Vforward is usually 630-670mV, and they seem to have slightly softer knee charasteristics (slower transistion into clipping). Ideal for an overdrive pedal really.

The 1S2473 is now obsolete and rare.
A 1N4148 or 1N4149 is a fairly close equivalent to 1S2473 (or 1S1588) and is easy to get.

Apparently the 1S1588 is the original Maxon 808 and TS9 clipping diode, and is still available at a reasonable price at Effects Connection online store.

This has very similar spec's and characteristics to the 1S2473 anyway, so it the one to use for a "real" 70's TS or SD-1 circuit.

DrNomis wrote:I was intregued enough about using back-to-back J-Fets,that I decided to do a quick experiment just to see if it actually worked,and....well,see for yourself,here is the evidence.....

Nice work DrNomis.
You could really stir things up by inserting some ge or silicon diodes in series with first one, then both FET Sources, for different clipping waveforms.

DrNomis · Post by **DrNomis** » 09 Feb 2011, 04:21

blackbunny wrote:
JakeAC5253 wrote:* - Not sure really what the stock SD-1's clipping diodes are. I've searched high and low and found one reference to 1N916's, but nothing further to confirm or deny.
The stock diodes in the early MIJ SD-1 (and the OD-1 and the early MIJ DS-1) were 1S2473 or 1S1588, which are fast-recovery 35-40V general purpose small signal transistors. Vforward is usually 630-670mV, and they seem to have slightly softer knee charasteristics (slower transistion into clipping). Ideal for an overdrive pedal really.

The 1S2473 is now obsolete and rare.
A 1N4148 or 1N4149 is a fairly close equivalent to 1S2473 (or 1S1588) and is easy to get.

Apparently the 1S1588 is the original Maxon 808 and TS9 clipping diode, and is still available at a reasonable price at Effects Connection online store.

This has very similar spec's and characteristics to the 1S2473 anyway, so it the one to use for a "real" 70's TS or SD-1 circuit.

DrNomis wrote:I was intregued enough about using back-to-back J-Fets,that I decided to do a quick experiment just to see if it actually worked,and....well,see for yourself,here is the evidence.....
Nice work DrNomis.
You could really stir things up by inserting some ge or silicon diodes in series with first one, then both FET Sources, for different clipping waveforms.

You sure could,I might play around with the circuit a bit and see what I can make it do in terms of clipping,I had the idea of figuring out how to make the clipping adjustable,I'll make sure I post all my findings in this forum thread....

I wonder what putting a resistor from the drains to either the ground or signal will do....