Zener clipping thoughts? 2204 build

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ledvedder

ledvedder

Well-known member
I'm thinking about adding switchable zener clipping to my 2204 build. I don't want anything too overly clamping and compressed. My initial thought is a 3 way switch with 20v and mpsa06. But I figured I'd ask for some opinions. I know this can go deep down the rabbit hole.
 
If there is a separate switch for clipping ON/OFF it would be cool if it adjusted the MV simultaneously* so there is no volume change. I've always used a 3-way with center position as no clipping and don't know how to do it there.

* - probably either by adding a resistor across it or 'lifting' it from ground a little.
 
ledvedder said:
Between the zeners and ground?
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I like to put it on the signal side of the zeners but still on the path to ground. You could temporarily wire up a 25k trim pot as a variable resistor so that you can hear what it does.
 
I put a 6-position rotary in my build. But 18v is the highest I like. Anything higher than that and it's a bit silly because you can get the same amount of clipping with just the amp if it has enough gain. 20v on a typical 800 circuit can be had with just the gain control on its own, albeit at a higher volume. 18v, 12v, MPSA06, and 2N5401 work well. But it's all personal taste.
 
I have 24v ,20v, 12v, 5v, mpsa06, and 2n5400 diodes on hand. Just trying to decide on the best 2 combinations to put on an on-off-on switch.
 
ledvedder said:
I have 24v ,20v, 12v, 5v, mpsa06, and 2n5400 diodes on hand. Just trying to decide on the best 2 combinations to put on an on-off-on switch.
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In my experience it depends on how you have your master configured. Pre tone stack Jose master and you can go more aggressive with the clamping, whereas with keeping the traditional MV placement less aggressive clamping is better. Only you can tell what you like, I'd suggest playing with a range of values to see what you prefer.
 
Using the headfirst style setup from one of Jason’s schematics I found 20v 1n4747a’s to be way too compressed. I’d start with 12’s or tinker with the other values on a switch. I love gain but less is more when it comes to diodes.
 
Chubbs said:
Using the headfirst style setup from one of Jason’s schematics I found 20v 1n4747a’s to be way too compressed. I’d start with 12’s or tinker with the other values on a switch. I love gain but less is more when it comes to diodes.
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But the lower the voltage, the more compression there is. 12v is more compressed than 20v.
 
It’s kind of redundant to do MPSA06, 2N5400 and 5V zener in the same setup. At that point you’re splitting hairs because the clipping threshold is within 1V of each other.
 
scottosan said:
It’s kind of redundant to do MPSA06, 2N5400 and 5V zener in the same setup. At that point you’re splitting hairs because the clipping threshold is within 1V of each other.
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If I had to choose only two, it would be 18v zeners and 2N5401.

MPSA06 and 2N5401 (not 400) do sound slightly different though. Not so much in the amount of clipping, but in the character of the clipping. No idea what the clamping voltage actually is. Haven't measured it. But you can't go off the data sheet as their behavior when wired up like zeners isn't the same as their listed voltage.

One thing I have't played with yet is asymmetric clipping.
 
I went with 20v and 12v, since that's what I had available. I'm not too crazy about the 12v, so I may change them.
 
I have 20v and MPSA06 in my Atomica style amp...
I always use the 20v though...
 
ledvedder said:
I went with 20v and 12v, since that's what I had available. I'm not too crazy about the 12v, so I may change them.
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I had a V2 Caldera and it was like the perfect JCM800. I think he has or had some mod PCB's that are worth a look. I know you already used the HF Fet boost so if you want to try some other stuff give V2 amplification's site a look.
 
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