Fuzz/Phase shifting effect (muskito flying by) in the mids

[JamesHealey]

well you're not alone my 69 Super Bass does this, I just thought it was part of the idiosyncratic tone somewhat unstable and untamable.

[5150loveeddie]

well you're not alone my 69 Super Bass does this, I just thought it was part of the idiosyncratic tone somewhat unstable and untamable.

HEy James welcome here bro....

The swril is a common snag in most Marshalls, it is part of the MArshall sound, some has it more some less, actually just a little swril will kinda make it sound fuller in my opinion but just a little, more of it and then it gets in the way and can be so annoying. THe Zenner clipper will help alot, it did for me...

[5150loveeddie]

So anyone tried the zinner clipper yet?? Allo!!!!

[Ricky Lee]

Here's a photo of Zeners in my 68

[5150loveeddie]

Here's a photo of Zeners in my 68

Nice red dye there, where can we have some of that???

You removed the 220k?? Should you piggy back the clipper on top of them instead?? That is what I did!!

[Ricky Lee]

220k bias resistors removed for the LAR/MAR PPIMV - The red stuff is a Sharpie marker, it's real close looking for the old Marshall dye.

[RagnarMarGunn]

I had this same problem in my '67 Marshall JMP 50W and it was driving me crazy, especially because I use THD Hotplate to keep the peace at home, it's worse with Hotplate. I've read through all of the 12 pages and finally I understood what you guys, that have some knowledge of how these amps actually work, are saying. My problem is fixed. I used 39V Zener diode and a small signal diode (1N914), 39 was the highest value I could find in Iceland. I biased the amp the closest to 39V as I could and it totall worked. There is still a small residual of mosquitoes, but they have stopped flying around the room, they stay in one place and keep to them selfs. Exellent thread ... even for newbies like me.

[5150loveeddie]

I had this same problem in my '67 Marshall JMP 50W and it was driving me crazy, especially because I use THD Hotplate to keep the peace at home, it's worse with Hotplate. I've read through all of the 12 pages and finally I understood what you guys, that have some knowledge of how these amps actually work, are saying. My problem is fixed. I used 39V Zener diode and a small signal diode (1N914), 39 was the highest value I could find in Iceland. I biased the amp the closest to 39V as I could and it totall worked. There is still a small residual of mosquitoes, but they have stopped flying around the room, they stay in one place and keep to them selfs. Exellent thread ... even for newbies like me.

Hey man thx for the reply, it does work super great, your description is dead on, I still a have a mini leftover that you can live with, same as you described it .....

Thx to M. Aikman, he is the guy who deliver the goods on that zener trimmer mod..

I can hear the zener kicking out in the speakers when I stop playing the amp abruptly (in the hiss), do you? Anyway it is irrelevant, no big deal, just confirms that the Zeners are working I guess...

[Froumy]

Ragnarmargunn-
Glad you found this thread. This thing has been kicking around for a while. Hope it works for you. Big thanks to Mr. Aiken for sharing his knowledge.

5150/Rickylee,
Are you guys happy with it? Are the trade offs worth it? I could see it on my scope but have never heard it.... Also, Did you guys up your plate resistors like Dan? Just curious if it's related to total gain factor of the preamp(and how that's accomplished) , or some other voodoo factor....

Nice work on the new release 5150 !!!

[5150loveeddie]

Ragnarmargunn-
Glad you found this thread. This thing has been kicking around for a while. Hope it works for you. Big thanks to Mr. Aiken for sharing his knowledge.

5150/Rickylee,
Are you guys happy with it? Are the trade offs worth it? I could see it on my scope but have never heard it.... Also, Did you guys up your plate resistors like Dan? Just curious if it's related to total gain factor of the preamp(and how that's accomplished) , or some other voodoo factor....

Nice work on the new release 5150 !!!

1000% worth it YES. Day and night difference and you can play with it, I think a hair of swril is "good" make the amp hairy, you can't really heard it now unless you are very attentive to it, before it was insanely annoying, muskito country, or electric shaver shoop running at full blast...

You guys must try it, il only cost a few pennies to do..

As a recap here's what you have to do:

1)BIAS your tubes at your liking (you must be properly BIAS before anything else)
2)Once your tubes are perfectly BIASED, mesure your BIAS VOLTAGE (at the pin5's or junction of 220k/output coupling cap .1ufand/or.022uf)
3)you should have anything around minus 25-45vdc
4)choose your Zeners 2-3volts above that value (you can try 1v above or 4-5v above whatever you want, it is a try and see thing here, I use around 1-2v above my bias voltage)
The closer the more effective I beleive BUT I don't really heard a big difference at 2-3v, maybe 4 or more you will heard more swrirling...
remember that when you will REBIAS your amp later you will suck up more BIAS voltage so the gap will increase from now and later, so you maybe want to install a Zener closer to 1-2v so you still are closer the next time you reBIAS, or you will need to redo your clippers, no big deal...
5)fabricate your clipper and install it, your done...

[danielesindaco]

Hi guys,
Could somebody re-attach a pic of the schematic of the zener+diode solution in fixed-bias marshall style amps?
Mr. Aiken and other members did attach pics at the time but all links pics are dead seen it is a old thread....
Many thanks
Dani