Blackface Vibrolux Reverb Amp

[Rogerio]

Hi Guys,

I would like to build a Blackface '63 / '64 Vibrolux Reverb Amp, I don't know what circuit to use, AA964, AB763, AB864 or AB964, which one should I copy, can anyone help me.

Regards,
Roger

[Tom Phillips]

I have the AA964 version in my shop manual and use it as my basic refurb reference. I think you will be happy with that version.
I have a note that the AA964 appears to be identical to the AA864. I'd be interested if others have the same opinion or what the subtle difference is.
Tom

[pdf64]

A weird thing with those amps is the power transformer. The schematics (AA964 & AB763) I've see all have a 125P26A, but some show the B+ winding voltage as 315-0-315V, others 345-0-345V. Have you got links to AB864 & AB964 schematics? Pete.

[MWJB]

AA763, or AB763 would be 63/64 BF circuits.

Pete, 125P26A is just a Fender reference for a Vibrolux (& similar) PT, it does not relate to a specific B+ voltage...which rose over time without part no's being changed. AB763 schem shows 410vdc, add 10-15% for what it would run today, so 450-470vdc might be considered ball park.

[Tom Phillips]

I only have a copy of AA964. Schematic heaven has the AA964 too. I have not found copies of the other models yet.
I have seen the same issue with the transformer voltages over several different models / service information too.
Tom

[Rogerio]

Thanks for all your feedback, so I guess the AA964 is the one to copy ?

[greekie]

One detail you should make sure to include, or at least try out, is this:

Twist the wire going from the input with the "return-wire" from the volume pot on both channels. I have seen this in many original BF amps. It gives the amp a certain "special something" IMHO, as the signal coming from the volume-pot is now trying to cancel the signal coming from the input. In reality, it works like a treble-cut, adjustable by how high you turn up your volume. When you dime it, it backs off a little of the treble and gives you that nice, creamy crunchy sound that some people look for in a BF amp.

Tell me if you noticed the effect.

Jake

[Tom Phillips]

Thanks for all your feedback, so I guess the AA964 is the one to copy ?

I think that would be fine.The 964 is, I believe, the last of the original BF versions.I don't have the literature at hand to research the differences between the AA964 and that other model numbers you mentioned. However, the differences would be minor. The upgrades you can add are: Grounded power cord, bias adjustment for each power tube, hum balance control and improved grounding & wire dress. There are many forum discussions on these topics.
Cheers,
Tom

[Rogerio]

I don't like using single wire in the inputs and volumes, I usually use RG174 cable

[Tom Phillips]

I don't like using single wire in the inputs and volumes, I usually use RG174 cable

Agreed. I should have listed that as an upgrade too.

[Rogerio]

Well, thank you all for your help so far, I'll be starting my project within the next few days and I'll keep you posted on my progress. For sure I'll be back with some more questions.

Cheers Guys

[greekie]

I don't like using single wire in the inputs and volumes, I usually use RG174 cable

It's totally a matter of taste yes, but I think people who wants to make "a Blackface amp" should try my suggestion. It makes a subtle, but IMHO important difference.

Jake

[Rogerio]

Hi Jake,
Thank you for your suggestion, I will certainly try your it out.

[greekie]

Hi Jake,
Thank you for your suggestion, I will certainly try your it out.

Be sure to get back to me with feedback, and to the rest of us with pictures and a description of what you've used and so on! That way we can all learn :-)

May thy soldering be perfect and thy tubes light up in greater sonical glory!

Jake

[Rogerio]

Greetings everyone,
Anyone know where I can buy a power transformer with 230V primary for the Vibrolux Reverb ?

Roger