King of Tone Clone - MA856 vs. MA858 Diodes

[natron_mn]

I've built a few King of Tone Clones using the Rullywow Queen of Bone 2 circuit board, and have thus far only used 1N1418 diodes, as I've read that it's hard to hear any difference between those and the 1S1588s and MA856s.

However, now I'd like to build one as close to "spec" as possible, so I've ordered some 1S1588 and MA858 diodes. Wondering if those are similar enough to the MA856s, or if they are something different entirely?

I compared the two datasheets, though I'm not exactly sure what to look for. They looked similar for the most part, but some of the graphs were slightly different.

Anyone have any experience with these diodes, or be able to surmise these two are nearly the same?

[Mark Hammer]

There can be unit-to-unit variation in the forward voltage of diodes from within the same "family" and also the same part number.  So, not all 1N4148s have the exact same forward voltage, which can impact on what period of a note's duration is at or above the clipping threshold.

Ultimately, that tends to matter a lot more than nominal selection of diodes (e.g., MA856 vs MA858).  A pair of 1N914s with a Vf of 640mv will sound different than another pair with a Vf of 530mv, or another pair where one conducts at 517mv and the other doesn't conduct until 672mv.

Do Analog Tom and Mike select for Vf to have a consistent clipping threshold?  I have no idea.

[Magnus]

Hello,
I can say that the difference between 1S1588's and 1N914's is really small but you can hear it...

Didn't make a direct comparison between 1N4148's and 1S1588's but I think it won't be very huge 


Greetings
Magnus

[smallbearelec]

One of the features of the MA856 is low junction capacitance. I fished for an alternate and one of my surplus sources had these:

http://smallbear-electronics.mybigcommerce.com/diode-fairchild-fdh900/

I have sold some, have not had any feedback one way or the other yet.

[natron_mn]

Thanks folks. So it sounds like the difference in "model" of MA856 vs. MA858 isn't necessarily the issue, but rather it's a tolerance type issue that varies component to component?

And thanks Small Bear - I ordered 10 of those just now, so I'll play around with diodes and see what sounds good!

[Mark Hammer]

One of the features of the MA856 is low junction capacitance. I fished for an alternate and one of my surplus sources had these:

http://smallbear-electronics.mybigcommerce.com/diode-fairchild-fdh900/

I have sold some, have not had any feedback one way or the other yet.

Is the difference in junction capacitance anything that would matter in the frequency range of guitars?  I'm not disputing that there is a real and functional difference in specs.  It's just that sometimes those differences don't really matter all that much in our little 6-string 6khz-bandwidth universe.