Golborne Vintage Radio

All
I have being planning to build a small guitar amp and have selected to clone my version of a very rare 10 watt Marshall amp from the late 60s, the 1930 popular combo. This was a 2 x 10 or 1 x12 unit based on a 1 x Ecc83 and 2 x ECL86 valve combination. Having undertaken some research, their is mixed views on using ECL86 valves as they are considered acoustically 'anaemic' and also can be very noisy. However, the reason for this selection is to able to get a rich tone without ear splitting volume levels such as circuits that utilise 2 x EL84 valves (I already have one at home and I have never been able to push it hard as it is far too loud).

I have attached a couple of schematics.

I have virtually all of the components for the build too including vintage mustard caps etc.

Regards

Rob 
[attachment=16020][attachment=16021][attachment=16022][attachment=16023][attachment=16024]

Would the Radiospares transformer in the other thread be enough for 10 watts?

Lawrence.

It was in a an old radio chassis powering 3 top cap valves, a rectifier valve and a 6v6gt output valve. I believe it to be powerful enough but will take advice from more knowledgeable forum members.

Regards

Rob

I might be wrong but I have a feeling it will struggle.

Lawrence.

Lawrence
You are bursting my bubble, but you may be correct. Is there any easy way to find out??

Regards

I would be tempted to use a slightly higher value cathode resistor in the output pair to reduce the overall current.
Perhaps a switched resistor to give the distortion effect at lower volume.

(06-04-2017, 02:55 PM)Bushbaby Wrote: [ -> ]Lawrence
You are bursting my bubble, but you may be correct. Is there any easy way to find out??

Regards

Ideally you need to know the specs of the original transformer in that design or at least what the main HT voltage was.

Check out the operating characteristics for Class AB push pull for the ECL86, your transformer would be at it's rated current limit at quiescent if I'm reading it right....4th page of this:

http://www.r-type.org/pdfs/ecl86.pdf

Lawrence.

Just another thought, what output transformer will you be using?

Lawrence.

Oh dear. Both transformers I had considered are too small. I am going to have to source suitable ones!!!

This lot do a 10 watt push pull for ECL86's (VTP 13186):

http://www.vvttransformers.co.uk/output_pp_tx.htm

They also do a mains transformer for the Mullard 5-10, that would probably do (VTH 12480):

http://www.vvttransformers.co.uk/ht_tx.htm

Lawrence.