Fender Bandmaster Silverface Trem into Drive

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12/4/2003 10:30 PM
Constantin Necrasov	Fender Bandmaster Silverface Trem into Drive I was thinking to remove the tremolo cirquit and replace it with an extra gain stage to be able to overdrive the preamp tubes. Is it safe to do? Will it alter the bias of the power tubes (since a large change in the tube configuration, etc)?   Are there any known succesful mods like this done by anyone or posted anywhere?     Thank you all.

 

12/5/2003 4:42 AM
Mark Lavelle	I was thinking to remove the tremolo cirquit and replace it with an extra gain stage to be able to overdrive the preamp tubes. Is it safe to do?     Yes – but it could sound ugly...     Will it alter the bias of the power tubes (since a large change in the tube configuration, etc)?     No.     Are there any known succesful mods like this done by anyone or posted anywhere?     I have no idea!

 

12/5/2003 5:07 AM
Constantin Necrasov	Thanks for the words of caution. What I was thinking to do is just to add another gain stage after the first half of the preamp tube. The amp has already passed through "blackfaceing" process and souns much better. I just want some very subtle "warmth" to the channel.   Any suggestions are welcome!     Thank you.

 

12/5/2003 5:40 PM

Chuck

If you just want to give it a little warmth, often times just disconnecting the trem circuit at the pot to remove the 50k load from the signal lead will do just that. If you really want to get slick after that you can use the extra 9 pin socket and tube to build a pair of cathode followers to run the power tube grids. That will add a little more warmth. Well I don't really know if warmth is the right description, but both of these mods will not alter the actual tone much and it will put a bit more gain on reserve and likely improve power tube distortion.     Chuck

 

12/6/2003 4:22 AM

Constantin Necrasov

thank you very much, Chuck!     The original sound of this amplifier is clean as the newborn's lungs. And it kinda sounds boooreing.   I don't want an overdrive channel per se, but a slightly different sound, something a little more compressed so to say, but clear.   I already trashed the tremolo cirquit and cleaned the area up. Changed the layout a bit too. Goobye long twisted wires from the tubes to the tone controls. Hello quiet amplifier.     You say a cathode follower...   I saw one in the Matchless Hotbox schematic (the last stage before tone controls), but it operates at different (much higher) voltages. Will it make my oldie Fender sqweal and oscillate? There will be a Master volume control before the phase inverter to get overdrive without getting deaf, but still.     I heard that old fenders are not meant to have high gain due to layout problems. Is a   "triode stage->Gain pot->triode stage->triode cathode follower->tone->Master"   type of cirquit capable of somethiing really high gain?     Still welcoming all inputs!     Thanx!

 

12/6/2003 5:05 AM

Chuck

I've built a few really good sounding "Marshall" amps with the line up you're proposing. But it's too much work to rewire it in your amp. Unless you don't mind alot of work?     The cathode followers I'm suggesting are after the PI and would feed the power tube grids. The low impedance drive helps eliminate "blocking" so you can drive the bejeezus outta your power tubes. So if ear splitting volumes are a problem for you...You don't need this.     What you could do is look at some older Boogie schems. They have some older designs loosley based on the BF type circuit that give some real warm OD tones...Just ask Carlos Santana about that.     I think it's just an extra gain stage AFTER the tone stack.     Chuck

 

12/6/2003 4:13 PM

Constantin Necrasov

Hey Chuck! Thanks for the info.     I don't mind some work, and the amp is already on my bench guts up.   I looked up the schematics for Boogie and found this:     http://www.tubefreak.com/mb1pre.gif     But the problem is that this setup calls for three volume knobs. I can't have three. So I dump one gain stage. Thus a whole half of the tube sits unused inside the amp. Do I need o ground it? Or maybe I can use it like this:     http://www1.korksoft.com/~schem/newamps/pignose_g40.pdf     This pignose has the cathode follower before the tone stack.   Now my question is this. Is it better to drive the master volume or the tone stack with the cathose follower?   What does cathode follower does to the sound in general?   So far I'll just continue cleaning up the insides of the amp.   Hope to read from you soon.   Thanx.

 

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