8x 1N60, give to low clipping on TS 808

[sebarb]

Hi all, I use rotary switch for the diode clipping on my TS808,
symetric, asymetric silicone and red LED work perfectly

But germanium, 8 x 1N60 in serie (1.8v same as my red LED) give realy low clipping! low volume and low gain, just realy small crunch! (max gain & max level)
I try 1,2,3.....8 1N60 in serie for the same result! ??

I look around and i didn't find a way to understang it!?

[MaxPower]

I don't know about the lower volume/gain but germanium diodes give a softer distortion than silicon diodes. Germaniums also drop about .3 volts whereas silicon diodes drop about .7 volts, while LEDs vary depending on color (or am I thinking of something else?). Hope that helps.

[GibsonGM]

Max is correct. They are simply different diodes, and you're using them in a feedback loop as opposed to on the output, so their behavior is different.   There is more to this and I hope someone comes along to explain - such as why you adding more in series doesn't raise your output (?)...can't really see what you're doing and all...

[Digital Larry]

I have not experimented with any Germanium diodes, so I just ask the question - is it possible that reverse leakage current is bringing your overall gain down?

http://www.americanmicrosemi.com/information/tutorial/index.php?t_id=7

Shows that at 10 volts, a 1N34A could have 30 mA reverse current.  So that's an impedance of, err, (cough)... about 333 ohms?  No idea if the leakage is linear with voltage (probably not) but that is a very low impedance, assuming that your feedback resistors are in the typical tens-of-K range.

[karbomusic]

I have not experimented with any Germanium diodes, so I just ask the question - is it possible that reverse leakage current is bringing your overall gain down?

Based on a TS style circuit I've been designing/testing lately the above gets my vote.

[midwayfair]

Germanium diodes also have a very low resistance across them -- I have some as low as 10K. This resistance is in parallel with your gain control -- and the other diodes. Regardless of how the diodes are clipping, they are ALWAYS presenting this resistance and lowering the gain.

Try Schottky diodes instead if you want to avoid this issue.

[sebarb]

I just try some clipping diode and on this germanium position I am looking for germanium musical tone and texture.

And I find this from dirk wacker, premierguitar http://blog-imgs-38.fc2.com/m/y/k/mykeita/200701_tubescreamer_2.jpg
Same, few 1N60 in serie but also in serie with original D2, 1N4148! and now it's working, output, overdrive.... but about germanium tone it's subtil, not day and night!

[duck_arse]

you could try replace the high Vf 1N4148 with a low Vf schottky, then add some more Ge's.

[PRR]

> 1N34A could have 30 mA reverse current.

That would be a "dud". Most small-diode circuits would not work if leakage were that high.

Ah, it seems the guy who wrote that page for American Microsemiconductor can't read the company's own datasheet. 30 micro Amps, not milli-Amps.

So hundreds of K Ohms, not hundreds of Ohms.

Makes a difference in a 100K-500K circuit, but not a huge one. Reduces the Max gain a bit.

[Digital Larry]

Thanks for clearing that up PRR.

[sebarb]

Thank all, for your replys, difficult to find schottky in my place, need order but I will try it soon as possible,
schottky BAT41 or 1N5817, can do the work? to add more Ge's!