Jose Master Volume question

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MrDan666
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Post by MrDan666 » Sun Sep 30, 2007 10:41 am

In the diagram it shows the 100k resistor moved to the tube socket and the other end to ground..

Where is the best place to ground the resistor?

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Post by bmf5150 » Wed Dec 05, 2007 11:23 pm

found it,need to try it..
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Post by bmf5150 » Wed Dec 05, 2007 11:28 pm

so you need to use TWO back to back 20v Zeners... not 1 Zener + 1N4007...i got this from the other post about it...anyone tried it yet??
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Post by rockstah » Thu Dec 06, 2007 12:08 am

yeah mark told me two zeners - larry said 1 - mark must be busy he still hanst responded.

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Post by rockstah » Thu Dec 06, 2007 12:18 am

MrDan666 wrote:In the diagram it shows the 100k resistor moved to the tube socket and the other end to ground..

Where is the best place to ground the resistor?
put a ground lug on the tube socket screw.
Image


i could have sworn i started a thread where i posted all these but cant find it now.

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Post by Ralle » Thu Dec 06, 2007 1:30 pm

Has anyone tryid this mod? In what way does it effect the sound?

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Post by jerrydyer » Thu Dec 06, 2007 2:19 pm

so here is my take I dont know how it sounds on a non master but with a MV clone I like the diodes but not the circuit and location. Causes it to break up sooner and I like the low settings of the preamp to be cleaner. Also added a bass I didnt like. The two zeners on the back of the regular 1meg MV pot is killer.
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Re: Jose Master Volume question

Post by Kapo_Polenton » Wed Jan 13, 2010 11:50 pm

I'm digging this thread back up as I found it after some extensive searching. There seem to be a few diff ways to do this. I noticed that the Jose modded Superlead in the high gain shootout a while back sounded pretty kick ass. If the Jose master floating around here is anywhere close, I'd like to try it out in my NMV. Any updates or reviews on what you liked or did not like about this?

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Re: Jose Master Volume question

Post by harddriver » Thu Jan 14, 2010 12:33 am

Quite a few techs who have seen alot of Jose amps say the majority of his amps used the master volume 1MEG pot before the tonestack without the diodes more than with the diodes. You can try the master out to see if you like it, it's the way it interacts with the circuit tapping the signal before the tonestack that is Jose's trademark tone IMO.

In a two gain stage plexi/SL circuit at extreme lower volumes it takes away the ability to drive the Phase Inverter to clip, which is every bit a part of the Marshall tone as Power section clipping. The Jose master shines best with 3 or four gainstage amps when you are looking for volume control.

The Jose amp in the shootout probably had his standard three gain stage cascade preamp, 2.7/.68uf V1A, 2.7/.68uf V1B.

Along with the standard pre PI 2203 style master, the Jose is one of my favorites.

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Re: Jose Master Volume question

Post by Kapo_Polenton » Thu Jan 14, 2010 9:35 am

So is the layout in this thread (2nd page) http://forum.metroamp.com/viewtopic.php ... 7&start=15" onclick="window.open(this.href);return false; more or less accurate? I guess the changes would be to drop the diodes and cascade the preamp?

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Re: Jose Master Volume question

Post by harddriver » Thu Jan 14, 2010 10:55 am

Yes, that layout is correct. The Zener Diode that seems to work best is the 1N4747A in the 20V.

The only correction is that usually it is two zener diodes used, but you can mix and match as well as drop the zener values and get them to clip earlier but the headroom of the master is lost then and you.

You are correct VH junkie, the input signal strength controlled by the preamp volume actually will control the amount of clippiing in the above layout not the master itself unless wired as you show in the SDM drawing.

Kevin Conner calls these diodes bounding circuits in TUT.

You could also put the diodes on a switch and switch them out of the circuit if you wish.
Last edited by harddriver on Thu Jan 14, 2010 11:44 am, edited 1 time in total.

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Re: Jose Master Volume question

Post by vh junkie » Thu Jan 14, 2010 11:12 am

You can try the master first without the diodes. Note that this would be a good time to experiment with a tone stack switch because those components are involved here as well.

If you do use the diodes:
1) With the schematic shown previously, the diodes are across the master pot; so the master does NOT control the clipping. You would need to have a gain control earlier in the circuit, that when turned down, would start the diodes clipping. See novosibir's post on the previous page to confirm this.

2) The diodes can be connected to the wiper of the master pot as shown in the following diagram from SDM.
Attachments
SDM Jose diode%20clipping.jpg
SDM Jose diode%20clipping.jpg (38.95 KiB) Viewed 7395 times
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jerrydyer
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Re: Jose Master Volume question

Post by jerrydyer » Thu Jan 14, 2010 11:54 am

its the asymetrical clipping that gives that slightly pissed off tone on top of the smoothmess that it adds.
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Re: Jose Master Volume question

Post by Kapo_Polenton » Thu Jan 14, 2010 1:07 pm

So the consensus here is that this Jose master should be in an amp with a pre phase inverter master volume/ 2203 cascaded preamp type setup and that it probably would not be as effective in a NMV..I'm also understading then that the preamp gain should be kept lower and the Jose 1 meg MV pot can be turned up to taste so that you are essentially blending preap gain + zener gain before the tonestack.In other words, gradual gain rather than concentrated in any one spot.I'm assuming now that this is why we see some of those older 4 input plexis rewired with another vol pot in one of the input holes and then another on the back or beside it.

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Re: Jose Master Volume question

Post by Good Guest » Thu Jan 14, 2010 1:34 pm

Like hard driver pointed out it's a bounding circuit....depending on the voltage rating of the zeners it will clamp the signal to that level and nothing more like a regulator...and zeners are used as r4egulators in plenty of circuits...making it useless for overdriving a phase inverter or even power amp distortion. I can't see Ed using this...if he preferred power amp distortion.

As the zener is a diode it can clip the signal once it hits that voltage threshold selected by you ie: 10 volts..20 volts etc. That's why it would actually do something besides limiting the volume if used with a hot preamp(cascade) designed to increase voltage levels higher than the zener cutoff levels.

Now the other non zener diodes aren't rated or selected for zener cutoff voltages and that's why they are used as clippers, you control the clipping level with resistors or a pot...just like a multitude of distortion boxs do. You may as well have a D+ in the effects loop .... and seeing as the clipping diodes are silicone you may as well use a transistor they are composed of 2 silicone diodes also....for that wonderful transistor tone. :roll:

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