Vibrolux or Vibroverb Poll

[plexi50]

I have been looking to build one of these two amplifiers

The Vibrolux had 200VDC on the first preamp stage

The Vibroverb has 280VDC on the first preamp stage

Wouldnt you think that the Vibrolux would have a sweeter tone using a lower preamp voltage?

Which amp is more prefered? I am leaning towards the Vibrolux. Which Vibrolux schematic is more prefered?

[LooseChange]

Had a 63 Vibrolux in my shop last week. Although it has no reverb, it had that tone that made you think it did.  The bias trem is sweet too.

[duke of earl]

Go ahead and build the Vibrolux and post some sound clips. Then build a Brown Vibroverb and you will have a nice arsenal.

[plexi50]

Had a 63 Vibrolux in my shop last week. Although it has no reverb, it had that tone that made you think it did.  The bias trem is sweet too.

You hit the nail right on the head with your comment. I Took the 1969 Bandmaster reverb i have and made a few value changes to the circuit to make the Bandmaster a Vibrolux AA763 with reverb of course

Strange and good thing here is my PT is 355-0-355 VAC even though the Bandmaster schematic says 375VDC primary

I am using a 5U4GB rectifier tube to get me a 420VDC plate. I used the blue molded Fender tone coupling caps of .1 & .047

Long story short: This amp is sweet as a frickin ripe and golden peach. Just put it back in the cab but have not tried hearing it with reverb yet

And here is where your comment striked home. The amp has a beautiful wave and chime to it like it had reverb when it wasnt hook up at the time i was testing it out after the changes were made

It breaks up very nicely as well just above 4-5 on the dial. I super highly recommend this change for any Bandmaster Reverb amplifier

The Super reverb,Deluxe and a few other all have the same  basis to work from. Granted you get lucky as i did with my PT primary being nearly right in the ball park plus having the mid pot really is nice
WOWZA!

[phsyconoodler]

The 6G16 Vibroverb has 135-155v on the preamp and it's way sweeter than the later AB763 vibroverb,which is just a Super Reverb in a different box with no mid control.
 

[plexi50]

Actually i changed and used the  AA964 schematic. So much nicer than a plain ole Bandmaster or Bassman

[worth]

The SMALLER output transformer makes it sound so nice.. and everyone always called the Bandmaster OT "wimpy".

[plexi50]

The SMALLER output transformer makes it sound so nice.. and everyone always called the Bandmaster OT "wimpy".

I have seen comments like that online about the OT being whimpy. It's a great sounding OT to me.

[CircuitButcher]

Hey phsyco, given your experience with V-Verb's, would appreciate your take on 12AX7 vs 12AT7 in the reverb driver & PI positions in the 6G16 vs AA(AB)763 circuits - did Leo just cut a sweet deal on some 12AT7's or is there more to it than that?

Thanks in advance

[topbrent]

The 6G16 Vibroverb has 135-155v on the preamp ...
 

Granted, I have never had a real 6g16 on my bench, but the 6g16 Vibroverb schematic calls for 210v on the preamp plates. 
-  Where are you getting the low voltage figures from? 

http://www.el34world.com/charts/Schematics/files/fender/vibroverb_6g16_schem.pdf

[phsyconoodler]

I was looking in the wrong place when I said 155v.Sorry about that!

I can't speaker for Leo about 12Ax7's vs 12AT7's,but it sure is nice using all 12AX7's.Easy and I like the reverb on the 6G16.Not as sproingy as the AB763 and others.
  The 6G16 circuit is designed for 12AX7's.I prefer it over the AB763 2-1. Everyone has their own opinions.

[pullshocks]

Seems like I remember reading that the earlier vibroverb had a unique setup on the reverb mix

[Fresh_Start]

Seems like I remember reading that the earlier vibroverb had a unique setup on the reverb mix

It does.  Instead of using a BIG 3.3meg resistor as the top half of a voltage divider to knock the dry signal down, the 6G16 uses a split plate resistor on the second gain stage.  Reverb is fed directly off the plate, but the dry signal comes from the intersection of a 82K and a 22K resistor which, in series, form the plate resistor.  That give you only 20% of the original signal for the "dry" signal (22/(22+82)).

This setup also allows the Reverb pot to be wired like a normal volume pot instead of the "backwards" way it's wired in the AB763 circuit.    That means the reverb recovery stage sees a constant load of 100K instead of a variable load.

I think the 6G16 reverb mixing circuit is really interesting.  At the very least, you avoid that big 3.3 meg resistor in the signal path contributing to hisssss...

BTW the plate voltage on the second triode of the Normal channel looks like 155 volts (due to the 220K plate resistor).  That bias point for a 12AX7 does sound sweet IMHO.

Cheers,

Chip

[sluckey]

This setup also allows the Reverb pot to be wired like a normal volume pot instead of the "backwards" way it's wired in the AB763 circuit.  That means the reverb recovery stage sees a constant load of 100K instead of a variable load.

Huh? Reverb pot ain't wired backwards on any AB763. It's wired just like a standard volume pot, ie, signal in (from plate of recovery amp) on the top lug, signal out (to grid of next stage) on the wiper. I only know one person that likes to wire the reverb pot backwards.   

I do like the looks of that 6G16 reverb circuit though. Wonder why it got changed?

[Fresh_Start]

This setup also allows the Reverb pot to be wired like a normal volume pot instead of the "backwards" way it's wired in the AB763 circuit.  That means the reverb recovery stage sees a constant load of 100K instead of a variable load.

Huh? Reverb pot ain't wired backwards on any AB763. It's wired just like a standard volume pot, ie, signal in (from plate of recovery amp) on the top lug, signal out (to grid of next stage) on the wiper. I only know one person that likes to wire the reverb pot backwards.   

I do like the looks of that 6G16 reverb circuit though. Wonder why it got changed?

I wonder if this setup is more sensitive to resistor variances than the AB763 arrangement.  However, I know that switching the actual 3.7meg mixing resistor to a 3.3meg resistor in a vintage Princeton Reverb made a big improvement in the amp's tone and noise level.

Cheers,

Chip

[phsyconoodler]

You mean it 'drifted' up to 3.7 meg.

[plexi50]

Im going to try this now. Get the 220K off ground. Remove 3.3M and add a 470K and with cap to Z. Can you see the cap value? I cant make it out. I sorta looks like it could be .02

[plexi50]

I just changed my AA964 reverb to the 6G16 reverb values and cathode seperation. I love it. It is not overly agressive as it was before. It is what i think reverb should sound like. But we all have different ears. Especially old ones about now. Too many Judas Priest concerts right in front of the speakers. I would describe it as smooth. Much less bright. The reverb pot ramps up slowly and evenly all the way from 2-10 without becoming dominant over the amps tone. The mix is good. I am using a 12AT7 tube now and am going to try a 12AX7 in a minute:

Well i tried a 12AX7 and it brings more presence to the reverb. I have to play with it for a few days to figure out what i am hearing. Overall it sounds much better than the stock AA964 reverb circuit

[plexi50]

Got parts in from Doug today. Real fast shipping! I installed a 50K SPST switch pot to get the Vibrato out of the circuit when not being used

A fairly large increase in gain when the Vibrato is off. Nice!

I also installed a 1Meg audio pull switch pot to get 47pf or147pf for the bright cap

The G616 reverb sounds best with a 12AX7 tube. It is a smoother refined reverb and sounds great from 1-10

This Bandmaster / Vibrolux circuit sure has become one of my favorite all time amplifiers

I am amazed that tweaking and building amps just keeps getting more fun surprising me now and then