1970 SF SUper Rev chassis project

[daybrow]

Before I begin, I want to express my gratitude to all those who take the time to answer questions posted in this forum. I've been building/repairing tube amplifiers since 2006, and when I come across something I'm unfamiliar with, I usually find what I'm looking for searching throughout these forums.

Thank you very much.


Here we go.
I was given a 1970 SF Super Reverb chassis by a good friend of mine. With no cabinet and speakers, I've decided to use it as a starting point for my first Dumble-style amplifier. I built a cabinet for it as a 210 combo (please see photo).

1. I've heard that one can use two 6v6's resulting in lower output wattage with an output impedance of 4 ohms (hence the two 10" 8 ohm speakers paralleled).

Is this true? Has anybody heard of this? I know I'll have to lower some of the B+ supply to the power tubes. I need to confirm this before I move on with this project.

Here are some of the features I would like to have in this amp:

- good clean channel
- good overdrive channel
- relay switching
- no FET pre amp
- HRM?
- line level out
- possibly an FX loop


I look forward to everyone's suggestions.

[Structo]

Welcome to the forum.

There has been quite a few ODS type amps built from old fender amps.
Some may feel it is taboo to convert a nice vintage fender amp since they are a dying breed but it is your amp.

Is this an AA270 or a Master Volume SR?

JJ 6V6 tubes are known to handle much higher voltages than old or other brand 6V6 tubes.
So most likely you can leave the voltage alone other than the dropping string for the preamp tubes.

May I ask why you want to use 6V6 tubes since they are not the norm for an ODS?

[BobW]

It looks like the older AA270 chassis

[roknroll]

shame to mess it up

[jelle]

Yes, think so too. I's replace the brown turd caps with 6PS and be done with it. Maybe recap if needed. Great amp.

Also building with fresh parts will give a cleaner result.

My 2 cents,
Jelle

[talbany]

Yes, think so too. I's replace the brown turd caps with 6PS and be done with it. Maybe recap if needed. Great amp.

Also building with fresh parts will give a cleaner result.

My 2 cents,
Jelle

+1

Silverface 70 super nice amp..Save it

[phsyconoodler]

Get a Zendrive pedal and leave the amp stock.Don't change the brown turd caps.They sound just fine.

[David Root]

Why not change the brown turds out for the old Blue Molded?

[daybrow]

Thanks to everyone who responded to my post. Here is my reasoning behind what I would like to do with this amp.

- no cabinet/speakers (huge part of why these amps sound so good)
- I do agree that the SR it is a great sounding amp, but it is too big for my needs
- this is a no-master AA270 chassis. At one time it was dropped on one of its corners. I was able to bend it back enough to fit into the cabinet I built.
- I want to use 6v6's because the 40 watts produced by the stock 6L6 power tubes is just too much for my needs.
- I have a set of JJ 6v6's, and I'm aware of their higher power handling. I'm just concerned with the OT impedance. Will it be higher around 4 ohms?
- I'm not sure I want to search for a cabinet and speakers to try and make this amp whole. I'm not sure it would see much use by me. I would probably eventually end up selling it.

As you can see, I'm not yet set on what I will do with this amp. Your comments would be appreciated.

[tubedogsmith]

Running the amp with the stock trannies at the voltages it runs with 6V6's is not going to be much quieter than 6L6's, only rattier sounding. If you want a dumble type amp just use the amp platform as it is. The masters work great on these and with a built in loop you have another master to make it sound even but down low. I don't really see any upside to 2 6V6's.

[analogjunkie]

Why not change the brown turds out for the old Blue Molded?

If you can find the old "Molded" caps let me know

Either way, the caps do make a difference in the overall tone, but not as much as changing some other values around:

100k/82 on the PI plates
1M on the PI cathodes
.01 PI coupling cap
Take the 1200pf/.002uf caps off the 6l6 grids

you should be good to go!

[Structo]

I have to mention that the guts of that amp are very tame when compared to other silverface amps of the era.
Most of them look like a spaghetti factory.

Super Reverbs are very highly regarded amps amps.

Just remember when these amps are gone, they are gone.

[phsyconoodler]

I've worked on numerous Fender amps and unless the brown turd caps are leaky,there is no tonal advantage to changing them to the blue molded ones.The brown turds sound just fine as long as the rest of the amp is in good shape.In fact I've worked on many silver face amps that sound just fantastic and they have all the original brown turd caps.
The caps get a bad rep for no good reason.They sound every bit as good as the sprague blue molded caps do.
Ayone who tells you otherwise is not really understanding the amp.There are so many other things that can make an amp sound bad.Blaming the caps is really kind of a blanket statement.They change the caps and while they are at it change the filter caps,bypass caps and put in new tubes.Then they exclaim "wow,the amp sounds fabulous now.Must have been those 'brown turds',never once thinking that maybe its the rest of the work that was done that made it sound great.

[crbowman]

I'm hip to low powered amps and LOVE 6V6's.
I did build a 20 watt 2X6V6 Dumble style amp along the lines of a DLite.
I must say that with that amp, I do sometimes want for a little more Ooomph. The Dumble PI and power stages are designed to stay clean and can therefore SEEM underpowered for their specified wattage.
Case in point, my Deluxe reverb is almost too much power for the band I play in, yet the 2X6V6 D clone seems underpowered sometimes.
I've also built a 2X6L6 70's style that is just about right for me.
If you are going to build it in that chassis, Please just save the parts you take out someplace safe. That way if you ever want to restore it you can.
Just my 2 cents.
Have fun!

[Structo]

If you are going to build it in that chassis, Please just save the parts you take out someplace safe. That way if you ever want to restore it you can.

True, you could snip the wires at the socket and pots and lift the circuit board out and save it for a rainy day, when you sell it or after you are gone, then the new owner could make the decision whether or not he wants a D amp or a Super Reverb.