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 slightly 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.  The trem still isn't perfect, slight tick when the amp is cranked.

• A couple of filter caps were replaced.

GOLDENTONE: Vintage Goldentone Guitar Amplifier, Model 1774

Picked this up today - it’s a Goldentone guitar amp from the early sixties.  Goldentones were made in Melbourne, Australia when imported amps were a rare and expensive sight due to import tariffs.

Like a few early Goldentones, this amp does not have a name or model number marked on the amp itself.  It's a 1774 model ~1960/1961 from the 1770 - 1780 series.  I also have a post about a 1776 here.

Thanks to Peter Field from the Goldentone facebook group for most of the information in this post - basically anything related to dates, the model and confirming speaker details. 

GOLDENTONE 1774 AMPLIFIER SPECS

• Blue canvas covering

• Volume and tone controls

• 2 x inputs, single channel

• 1 x Mullard 6CA7 (EL34)

• 1 x Ten 12AX7

• Silicon rectifier

• A&R transformers

• M.S.P. 12PS speaker 12” 16 ohms

• 10 watts

• Serial number 1189

I've not completely opened it up to look at how it's constructed, but one odd thing to note is that the volume and tone control is at the front end of the amp, before the 12AX7, and they appear to be configured the same way as a guitar volume and tone pot.

To the right of the volume and tone pots, additional holes for pots can be seen.  Looks like this model shared the same base plate as the tremolo model.  

M.S.P. 12PS speaker is dated September 1958.  Goldentone did use M.S.P. in addition to Rola speakers.  The 12PS was discontinued in 1960, the 12PQ is more commonly found in Goldentones - at least when Rola's are not installed.

A&R Transformers were made in Melbourne at the time and were common across most Goldentone amplifiers.

It has a fairly early serial number, as I've read that they started at 1000

It has a Mullard 6CA7 that was made in Holland, dated December 1959, in the power section and a Ten 12AX7 for the preamp 

ROSE MORRIS 61 - 62 CATALOG

GOLDENTONE 1774 SCHEMATIC

I haven't had this amp for a while, so this trace is based on the previous photos and the 1776 that I currently have, which is the same amp with trem.  There are a couple of very minor differences, such as 2k2 cathode resistors on one and 3k3 on the other.  But fundamentally, this is the amp.