Fender Custom Vibrolux Reverb Mods?

[doveman]

My son has a CVR that breaks up a little early and needs a bit more headroom. Internet searches turned up a Mark Moyer set of mods that adjust several things to help this. Some links seem to be dead that might have schematics describing the specific changes.

I figured the guys at the amp garage might know where these might be available.

Just wanting to help tune in my son's amp. Thanks in advance for any help.

[billyz]

If you need more headroom out of the Custom Vibrolux put the original Blackface style NFB loop back in it.

[CapnCrunch]

Hey Doveman.....

I just checked out your sites. Whoa, some really cool stuff there. You've got a great sound, and I thought it was pretty cool that your MySpace friends included Johnny Lang, Eric Clapton, Satriani, and the man David Gilmour, among other greats. That's really cool!

[doveman]

On the websites: Thanks ... Our bass player set up the myspace site ... I have no idea how it has all those guys on it. I'm the newest member to the band. The soundclick site is mine ... the myspace site is the bands. Having fun with both.

On the Fender amp: I've only built the one D'Lite amp I mentioned here from a kit. So I'm not the expert that the rest of you are ... any chance there are some layouts detailing these changes (like the NFB addition) somewhere?

[collinsamps]

I've seen some extensive mods done to the CVR for headroom. Most could be avoided just by changing the P10R's to higher powered ceramics (Weber 10F150, C10N, eminence patriot series etc) and V1 or 2 (depending on which channel you play) to a 5751, 12ay7, 12at7. It'll be a completely different amp and no solder joints touched.

[billyz]

Doveman,

To add the NFB loop look at a Vibrolux reverb schematic and layout. You'll need two resistors. an 820 ohm from the speaker out jack tip lug to the r37 tail resistor of the PI. Then you would lift the ground from the c19 capacitor and the r 37 resistor and series a 100 ohm resistor to ground. in other words , find which end of r37 and c19 are grounded. Lift that end of the components from the circuit. Tie them together add a 100 ohm and a 820 ohm resistor . the 820 ohm goes to the speaker jack ,the 100 ohm goes to ground , solder it back to either of the previous ground points.

I hope I explained it right . Maybe some one better can detail it for you.

Yes , tubes can be changed to lower amplification types . In Fact you may want to replace V6 with a 12at7 to get closer to the Blackface sound. and to get the same volume you would turn up a little bit more. Speakers could be more efficient and you would need less gain to achieve the same volume. Having worked on a few of these I think the sound you are after is to be found in the NFB addition though.

Here are the schematics you need.

[collinsamps]

deleted

[doveman]

Now we're talking ... all of this is very helpful.

[tweedeluxe]

I converted one into a Brownface Vibroverb. Kept the SS recto though. It is a pretty easy switch:

http://www.mojomusicalsupply.com/ampgui ... _schem.pdf

It tamed the amp quite a bit, and gave it a smoother sound. For substantially more headroom, I would suggest more powerful speakers.

Is your CVR really noisy? The two that I've played both had an obnoxious hiss. Playing with lead dress (what you can) will help a little as will negative feedback, but ditching the crimp-on connectors and soldering the speaker wires directly to the speaker tabs killed almost all the noise for me with both amps. Definitely worth a try.

[doveman]

Been following the threads on 5K linear pot for the NFB circuit. Also the idea about the on-off-on miniswitch for two separate resistor values. I'm assuming these are just options on the NFB mod explained above.

Any downsides to doing these other than the extra hole for a switch or pot?

Also ... yeah it's got a permanent hiss sound that would be nice to remove ... sounds like the NFB mod would help that too.

Might like to try other speakers ... it runs a 4 ohm load ... would it be OK with and 8 ohm load to test some other 10" speakers that I have?

[doveman]

To add the NFB loop look at a Vibrolux reverb schematic and layout. You'll need two resistors. an 820 ohm from the speaker out jack tip lug to the r37 tail resistor of the PI. Then you would lift the ground from the c19 capacitor and the r 37 resistor and series a 100 ohm resistor to ground. in other words , find which end of r37 and c19 are grounded. Lift that end of the components from the circuit. Tie them together add a 100 ohm and a 820 ohm resistor . the 820 ohm goes to the speaker jack ,the 100 ohm goes to ground , solder it back to either of the previous ground points.

What wattage should the 820 ohm and 100 ohm resistors be.

[billyz]

1/2 watt is what the originals are.

[doveman]

Thanks ... going to give this a try on my son's CVR.