Gretsch Amps

Gretsch “Super Bass 6157” circa 1967


The "spaghetti" is less than I would have expected.

Component datecodes are 1966 and 1967.

Transformers could use heavier tie-down straps, ... signs of past movement from shock and transport.


A pair of Heavy Duty Jensen C12N OEM-ed to Valco...

I received my order of 1/2" Acoustic Foam, half the old batting is missing and the rest shall be replaced.


I don't know that the original damping material is missing. As it only needs three sides of the box covered, it's likely that they only did the minimum. Adding more can only help. Amp looks surprisingly good for its age.


When you read this Advert it highlights the proprietary "Hi-Fi" method for making a better sounding enclosure...

The center panel is shorter than the sides, batting only on back and one side. I thought it to be a "field modification"... Ha!

However, whatever, the left speaker was somewhat louder than the right. Knowing the plan for the original circuit, the design is two equal 35W amps driving separately two equal 12" speakers...

My thought was the left side of the enclosure is resonating more sans batting...


As mentioned on an earlier thread, the schematic could be substantially more complicated.

It made me more comfortable given the 50+ year age that it could be refurbed either back to original, or onto a dueling pair of Supro Thunderbolts.


Next round of looking at the "spaghetti" suggests the two separate 35W circuits have been combined...

Output Trannies now in parallel and jumpered to be Mono.


"However, whatever, the left speaker was somewhat louder than the right."

Maybe the mystery lies with that 'wire to nowhere'?


There will be more surprises...

But, this first round is the fact finding and obvious needs oriented....hopefully put back to original intent. A ready and able "Super Bass".

The next round will be for grooming the innerds for Sound and Tone!

And Tavo's Mystery's a rather plain amp in and of itself.


Well, my amp is finally getting it's due...been in the repair queue for quite some time. There were 20+ amps ahead of me, and the Tech works part-time.

Should have a complete Inspection Report Card next week, then the components put on order, etc.

With all others things going on since last Fall, I wasn't really missing it nor in a hurry. It will be nice to get it back, get the music room all rearranged, etc.


Progress being made...

Cap can values incorrect and not wired per the schematic, the new ones will be.


Old carbon comp grid stoppers still in good shape...


Cracked Standby Switch

The Main Power switch is showing similar fractures and will be changed as well.

Added to replacement parts list...


Several missing grommets added where wires pass through the chassis.


Mystery 500uF capacitor to ground...thought to knock down some Treble and any "shrill".

Added at the Factory, not on the schematic...Valco-style!

Just like the Filter Cap values...


So far, so good...

I stopped in today at the shop to review the progress, and refresh our conversations. Things appear well thought out and organized. Where possible, little improvements are being made to isolate, secure, and protect components where Valco cut a corner.

Parts order will be let this week.

The video made by Brad Linzy "The Guitologist" regarding the same Amp had a few curiosities. Same mystery 500uF cap, same piece of masking tape in the corner with "67" written in pencil, etc.

Brad went so far as to scrap out a lot of the Tone circuit for simplicity in the direction of a Supro Thunderbolt. The plan is still to start with a fully refurbed, correct to the schematic, Super Bass.


Interesting way to shared Cathode Bias on each 6L6 pair...fine tuning with a second trimming resistor in parallel.

Another curiosity found is that the Standby Switch is wired as a "Mute" and does not shutdown any B+ Voltage...unlike the Advert description...

The Advert also says 8 Tubes, but there are only 6!

And at this point, nearly done testing and mapping, other than Electrolytics and a couple switches, most of the remaining Components are testing well in Spec.


Parts now arriving...

60, 2*30, and a 20 uF Cap Cans


Having had good time now to play around with Tavo's "Mystery Brain" pedal, I kinda figure the Super Bass Amp when complete is going to have a really, good raw sound to go along with it...a great match.

At least I think I can hone in on that tone.


Cap Cans now being wired up...old wire replaced for tinned copper with plastic insulation and woven cotton sleeve.


New Cans positioned with labels turned inward so as to appear original when looking into the back of the amp.


Cap Cans now all wired up.

The original Terminal Strip had cracked in the middle, apparently from the Power Cord missing strain relief.

New 3-Prong cord installed, "Death Cap" removed.

New Power and Mute switches installed, yet to be wired.

Register Sign in to join the conversation