Author Topic: Alpha Dog Clipping  (Read 303 times)

Aentons

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Alpha Dog Clipping
« on: August 28, 2017, 01:35:29 PM »
I see that in the Alpha Dog there are two clipping sections, "Hard" and "Soft". I understand that the normal Rat clipping is the Soft section. What is the "Hard" clipping section... the output stage? It looks like the options are the BS170 (Mosfet) transistor, no clipping, and the 1n34a(Germanium) diode.

I use to own a Deucetone Rat and it had lots of clipping options but I remember having the option of Germanium diodes in what would be the "Soft" section in the Alpha Dog. I guess I don't understand why the 1n34a is where it is?

The Deucetone clipping options were:

Clean Rat = no clipping
Vintage Rat = silicone diodes
Turbo Rat = LED
Dirty Rat = Germanium diodes


Also, I see the four 1n4148 diodes on one side of the "Soft" clipping section and the center position is no clipping. Is the other side the 2n5458? Isn't that a silicon transistor? Why use two silicon options instead of LEDs for one side?


Thanks folks!

madbean

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Re: Alpha Dog Clipping
« Reply #1 on: August 28, 2017, 06:36:38 PM »
You've actually got the hard and soft backwards. Hard clipping is the default Rat style which are the two 1n4148 that go straight to ground. It's a bit more complicated than the traditional setup since it has two more 1n4148 in parallel with the soft pot to blend additional clipping diodes in series. Soft clipping is in the feedback path of the op-amp. The Soft pot mixes between the two back to back clipping diodes in the op-amp which are the 1n34A and the "body diode" of the BS170. At center it has equal resistance on both sides meaning the least amount of soft clipping from either diode.

The 2n5458 has nothing to do with clipping. It's an output buffer.
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Aentons

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Re: Alpha Dog Clipping
« Reply #2 on: August 28, 2017, 08:54:20 PM »
Wow, Thanks. The Soft knob makes total sense now
Sorry, I guess I remembered the labels on the wrong sides.

So... Is the Hard pot blending between asymmetrical and symmetrical silicone clipping?

Also, you said: "it has two more 1n4148 in parallel with the soft pot to blend additional clipping diodes in series".
Did you mean?... in parallel with the Hard pot

Thanks Again!

WormBoy

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Re: Alpha Dog Clipping
« Reply #3 on: August 29, 2017, 12:18:45 AM »
The 'hard' section is always symmetrical. In the middle of the pot rotation, there will be basically no hard clipping at all. To one side, you blend in standard RAT clipping (two silicons). To the other side, you blend in four silicons plus a cap (which will roll off some highs). The configuration of the four silicons is non-standard as they are connected in the middle (like the Timmy does, but it has it as soft clipping). Rather clever tricks that VFE used to get many clipping options with a single pot.

madbean

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Re: Alpha Dog Clipping
« Reply #4 on: August 29, 2017, 05:44:57 AM »

Did you mean?... in parallel with the Hard pot

Oops yes I did.
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