GOLDENTONE: Model 1776 Guitar Amplifier

This is a Goldentone 1776, which is essentially a Goldentone 1774 with trem.   It had been reshoused in a 2 x 10 cab with Oxford speakers (one ceramic, one alnico), with the amp chassis mounted on the bottom, with the control panel up the top.  The amp would have been mounted the same way in its original 1 x 12" cab.

Based on the fact that it's made by Rose Morris, this would have been made before 1965.  Serial number 1375.  The 1776 models are listed as being made in 1961 - 1962

Apart from a DIY cab, I think it has had a little bit of work done on it.  There appeared to be an extra resistor in the power section - the rest looks stock, and I'd say there's a good chance that these are the original valves.  

Like its sibling, this amp has volume and tone controls before the first triode - which is kind of pointless.  It's low impedance, and it only really sounds good turned all the way up.  It basically puts another set of volume and tone controls before the amp, which you already have on your guitar.

GOLDENTONE MODEL 1776 GUITAR AMPLIFIER

• Single-ended 10w valve amp

• Volume 250k, Tone 250k, Depth 250k, Speed 2meg

• Silicon rectifier - looks like a voltage doubler

• 1 x 12AX7 preamp

• NFB to the first triode

• 1 x 6AU6 pentode driven tre, with Bakelite trem foot switch

• 1 x EL34 for the output

• Ducon caps

• OT  A&R 2584.  2k5 @ 16ohm

• PT A&R type 1971

Trem oscillator

POWER SUPPLY

• A&R type 1971 power transformer.

• Silicon rectifier, voltage doubler. 

• B+ 285v

SINGLE-ENDED OUTPUT TRANSFORMER

• A&R Type 2584

• Turns ratio 12.4

• 16 Ω speaker reflects 2.5 kΩ to the primary

COUPLING CAPS

These wax coupling caps had to come out - they didn't measure well at all - they never do.  When I tested the amp, it was sounding weak and thin.  Caps have been replaced.

GOLDENTONE 1776 - DRAFT SCHEMATIC

I've roughed out the main amplifier stage, and I'm nearly finished with the tremolo circuit. 

TREMOLO CIRCUIT

The 1776 uses a small 6AU6 pentode for the tremolo - the circuit is similar to the Silvertone 1482. 

I had to replace all of the caps, as they were well out of spec and a little leaky.

MODS

Modding a vintage amp is a little controversial, but this one was barely working when I got it, and it can easily be changed back. 

• Volume and tone moved to after the first triode

• Leaky wax paper coupling caps were replaced with larger values, as while the amp sounded great when cranked with the smaller caps, they didn't do it any favours running clean.

• The tremolo had to be rebuilt to get it working, and as I had changed the volume and tone controls, I had to move the point where it was inserted into amp.  

• A couple of filter caps were replaced.