Headfirst Amps, At The Bench - José Zener Diode clipping....explained!!

[@bhosterman]

This is exactly what kind of information I’ve been looking for! So stoked I found your channel.

[@Francisco17Berrios]

Thank you!!! Finally someone that will explain mods in a video in a very detailed way! :)

[@robertherndon514]

Thank you, Jason Tong, for your help and dedication to the craft...

[@RozsaAmplificationLLC]

Great video as always Jason and explaining what the zener diodes and Volatge Clamp are doing! What you should also communicate is the 10k resistor and .22uF cap are doing. What they are in there. What compliance is and what they are doing to the signal with and without being in the circuit! All you needed to do was put a switch in between C? and Z1. Show the voltage at V2 pin 8 (CF) with full signal, then thru the 10k and 22u compliance with Zeners off....then Zeners on! This would show the effect, but also the reason for them (unless I missed it somewhere in your video (didnt watch in entirety)!!

[@HeadfirstAmps]

It's a good idea this - to show the signal all the way through. I was pretty focused on just the zener breakdown effect....I'll try and remember to add this idea for a future one!

[@RozsaAmplificationLLC]

@@HeadfirstAmps yep, exactly. Folks just focus on the end results...100V in...clamp at 20V (or whatever)...but there is a little more going on. If you clip a 100V signal to 5V, it's going to sound like a beehive and pretty dramatic. The compliance helps support how dramatic the clip. The threshold also needs to be considered and symmetric and asymmetric. Someone in the forum posted asymmetric, but at more wider levels....say 5V and 20V instead of say 16V/20V. In that, it looks like they are looking for a mixture of tone 180 degrees out of phase. One will be very squashed and compressed and the other half more open!!! :) All kinds of fun in tuning an amp and getting Grail Tone!! :)

[@HeadfirstAmps]

Yeah man exactly. I tried a 24V/5.1V combo and was pretty impressed with the end tone!

[@clintn6677]

Thanks so much for these man. I'm spending my Sunday watch your vids and trying to learn something new.

[@HeadfirstAmps]

Glad you like them Clint!

[@perco754]

Love your videos with theory. Would you consider adding a frequency analysis as well? It would be really interesting to see the difference in the overtone series.

[@qddk9545]

That is a very interesting idea. Which application do you use yourself? You can measure on the amps speaker output, or on the speaker with a mic.

[@rflessati]

Thats a really good video on Zener mods. Its clear for me now. Thanks

[@mookytc]

As always great information being passed along!

[@IhabIAmer]

Magnificent! Keep it up.

[@qddk9545]

Marshall often uses standard diodes in parallel reverse mode, earlier in the circuit. That will limit the signal at that point to around 1.4v P/P, and I find it sounds horrible. Recently I clipped those diodes out on a DSL60 amp, and for the first time in my life I got severe blocking distortion - the following tube stage simply locks down, until the transfer cap is discharged enough to pass sound. I should have hooked a scope up, to look at it. Often I try to mod things without removing the PCB(s), which gives me less possibilities, so right now I have lowered the incoming signal to 1/3, but if that is not enough I might try different values of zener diodes. Thank you for all your valuable videos 🙂

[@azzazelo]

Such a great vid, thanks!

[@RDamps]

Superb stuff!

[@JosipAngeloBorovac]

Great video and explanation of different clipping schemes! Very educational! You just hit a spot with this video because just recently I acquired a Marshall 9001 tube preamp with so-called SRPP circuit and diodes used in the gain staging? Could you briefly comment on that design and if you would remove diodes from such circuit? I have wondered about doing it to possibly to get only tube clipping but was wondering if it is worth of hassle! Thanks for the vid!!!👍🏻

[@HeadfirstAmps]

I'll check out that circuit and report back!

[@JosipAngeloBorovac]

@@HeadfirstAmps thank you sir! :-)

[@qddk9545]

I would be VERY surprised if Marshall have ever used a SRPP circuit. And they did certainly not on the 9001 pre amp. It has 3 standard amplification stages in series. SRPP are kind of stacked on top of each other.

[@kirkgreenman1386]

I can’t wait to try that . Does the A-symmetric sound the same when the 5 volt clamping is on the positive half of the sign wave?

[@HeadfirstAmps]

Yes, for AC it doesn’t matter positive or negative

[@TheSwanage]

Can I just hook two zeners to the stock MV position as an always on clipper, or is moving the MV a must?

[@gbass7328]

Who would watch and put a thumbs down wtf lol

[@HeadfirstAmps]

The haters gotta hate!

[@voxpathfinder15r]

So is it fair to say zener diodes are trying to mimic power tube clipping, but at a far lower volume?

[@HeadfirstAmps]

Yes, this is a pretty good description actually.

[@MAURIIIII2009]

Excelent Class of mods

[@chrisstevens4680]

Why is the JCM800 logo upside down on your amp? Is it because it is an Australian issue?! 🤣 (Comment from the UK!) PS great video’s thanks!

[@patrickwilliams2530]

It is weird because compared to what some people tell the diodes are in opposite directions in your schematic look for : My Real Jose Modded 1979 Marshall 100 watt head- An in depth Look at the Build and Circuit by Ossie Ahsen. In his the diodes are inverted.

[@HeadfirstAmps]

Makes no difference, as long as they are in opposing directions

[@patrickwilliams2530]

@@HeadfirstAmps okay thank you for the info ^^!

[@errtrainer]

Wonderful series! Now i have a question. Krep in mind im a musician, noy an engineer. Ok, the zener mod can be made in other preamp stage? Not after the cathode follower of V2b but after the coupling cap in any of V1 triodes. Keep the good job!

[@HeadfirstAmps]

In theory yes. Take a look at the 2205, the Jubilee, the Carvin MTS, Wizards and so on. All have diode arrangements that come straight off the plate of a triode.

[@onewireman]

Thank you for all of your wonderful videos. Will this work the same if the master volume is after the tone stack?

[@jasonktong1]

Absolutely yes. Check out my recent mod videos for both the 1987x and the 2204 for how to wire these in properly whilst keeping a post tone stack master.

[@onewireman]

Thank you so much, I will give this a try this weekend. Any tips on how to get rid of the flubby low end of a JCA20H? I've tried everything I can think of:(

[@jasonktong1]

@@onewireman ah yep! Have you seen my JCA50H mod video?

[@onewireman]

@@jasonktong1 I will have to check it out...

[@onewireman]

Thank you for the hot tip. I replaced C26 with a 2n2, and it sounds much better. Now to implement the rest of your mods!!

[@kirkgreenman1386]

What is a good zener impedance and wattage?

[@HeadfirstAmps]

1N4747 is a good starting point. 20V 1W

[@Brosefmcjoeseph]

What would be the difference between the diodes in series vs parallel?

[@HeadfirstAmps]

Parallel is not a voltage clamping circuit, that’s more a noise gate coring circuit.

[@Brosefmcjoeseph]

Thank you!

[@voxpathfinder15r]

Isn’t it easier just to hook up an effects pedal?

[@HeadfirstAmps]

Not for me