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Wednesday, July 25, 2007

An Itinerant in England

The All DHT Amplifier in Early Testing Form

Well, I am finally back in France after an interesting trip.

This of course commenced with my attendance at the three days of the Goodwood Festival of Speed or Mud as some called it especially on the very wet Sunday. I suppose I had better not mention rain any more as I feel that my English readers will be angry!

I have not mentioned so far, another of my other "talents" or at least, abilities. I have warned in the past that this blog will contain articles other than about Fulvias; this is one of them.

I have spent a number of years designing and building Valve ("tube" for Americans) amplfiers for hi-fi. I have even proof-read a couple of books written in the subject (Valve Amplifiers 3rd edition and Building Valve Amplifiers both written by Morgan Jones)

On arriving at a friend's place in London I was offered work building a couple of amplifiers that would use (my friend's predilection) Directly Heated Triodes. For those not in the know, these are very old valves indeed dating from the 1930s and sometimes even earlier. Afficionados of these insist that the resulting sound is more detailed and revealing of the music than that obtained with more "modern" valves. Transistors in these circles I should add, are not considered...

The first of the amplifiers was just a straightforward line stage or pre-amplifier. The second was a more ambitious design. The order from the customer was for two of these - one for each channel. The specification called for an all direct-coupled three-stage design. This necessitated a considerable amount of effort and study of valve data plus many calculations. And then came the labour of planning the layout - that is finding space for all the bits, which is always tough. Here's a picture of the underside:

Experts will notice that there are transistors present, but they are there for "housekeeping" purposes, just to make conditions correct for the all-important valves.

The client came to hear the amplifier and was delighted with the sound and is very keen to know when I can return to England to build the other one!

The experience has rather inspired me to build something for myself, which I may well do when I have the time. Indeed I have already done most of the design and do have the valves I need to build it.

As they say "Watch this space".

Finally watch this space, as I have a report coming up about a 1600 Fulvia belonging to a new client who lives in France and on which I worked last weekend.

A bientôt

1 comment:

Justin said...

you ought really to be making a better living with this as one of your skills - I know how much goes into it, having witnessed the design and manufacture of your 1st examples, and having heard them - Jus

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