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Morgan Jones's Bevois Valley amp...

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nickds1

nickds1

Member
Joined 2005
nick.desmith.net/
Morgan Jones' Bevois Valley amp...

Hi,

I was considering building this amp as my first PP project. Anything I should be aware of (gotchas?), and any recommendations for component suppliers in the UK/Europe would be appreciated. I know a few, e.g. Jan Wüsten & Sowter, but I'm a bit new to valves, and would appreciate any pointers...

Thanks

Nicko
Nick de Smith Electronics homepage
 
Tubes4e4

Tubes4e4

Member
Joined 2005
Hi Nicko,

since you are from the UK, Sowter would be a very obvious and surely excellent choice for the OPTs.

Other makers of OPTs in Europe you can consider:

Lundahl (Sweden) - www.lundahl.se
Reinhöfer (Germany) - www.roehrentechnik.de
Automatic Electric Europe (Netherlands) - don´t remember
VVT Transformers (UK) - www.vvttramsformers.co.uk
Welter (Germany) - www.welter-electronic.de

And probably lots of others :)

Tom
 
Brian Beck

Brian Beck

Member
Joined 2004
In Jones’ book he says he bought a pair of mono tube amps from a junk store in Bevois Valley for 15 pounds. These became the basis for his new prototype amps (I assumed he reused the transformers and chassis or something similar). The resultant design subsequently became known as the Bevois Valley amp.
 
nickds1

nickds1

Member
Joined 2005
nick.desmith.net/
I did my EE degree at Southampton. ISTR Bevois (pronounced "beavers") Valley was a very cheap residential area popular with students. Rumour had it (though I wouldn't know!) that nominative determinism had played its part and that part of the "red light" area was there too...:rolleyes:

I too went to the electronics junk shop, and bought an IBM keyboard amomgst other rubbish - I don't remember seeing any valves in there, but that was 25 years ago. Most of my valves etc. came from HL Smiths in Edgware Rd or Proops in TCR.

Nicko
 
andyjevans

andyjevans

Member
Joined 2003
artsandmedia.com
Most of my valves etc. came from HL Smiths in Edgware Rd or Proops in TCR.>

I live in W.Kensington and my valves came from Colomor (the original Polish guys) and the MO valve Co. in Brook Green. To think I used to walk up to the counter and get new KT66, Mullard EL34 and ECC83 etc. as many as you could want for peanuts, and within easy walking distance of my appartment...... If only we had time machines.
 
A

Alex M

Member
Joined 2001
soundmovements.co.uk/diyaudio/index.html
Brian Beck said:
In Jones’ book he says he bought a pair of mono tube amps from a junk store in Bevois Valley for 15 pounds. These became the basis for his new prototype amps (I assumed he reused the transformers and chassis or something similar). The resultant design subsequently became known as the Bevois Valley amp.
Click to expand...

Bevois Valley has really gone to the dogs in the last few years - first Aldi arrived (though the car park is handy for Maplin), then S&L TV closed down...

Alex
 
nickds1

nickds1

Member
Joined 2005
nick.desmith.net/
Alex M said:
Bevois Valley has really gone to the dogs in the last few years...
Click to expand...
Is this another reference to "the oldest profession"? When I lived there, it was a rough as ****, i.e. well rough (as my kids would say).
There used to be a pub called the "Honest Lawyer". Cheap beer, ISTR. Had a bad experience during a three-legged pub-crawl... I suspect that has closed too...
 
A

Alex M

Member
Joined 2001
soundmovements.co.uk/diyaudio/index.html
nickds1 said:

Is this another reference to "the oldest profession"? When I lived there, it was a rough as ****, i.e. well rough (as my kids would say).
There used to be a pub called the "Honest Lawyer". Cheap beer, ISTR. Had a bad experience during a three-legged pub-crawl... I suspect that has closed too...
Click to expand...

There are definitely rougher areas in Southampton, but evidence of "the oldest profession" is still visible - I remember being in the New Inn for a drink on the odd occasion, and watching certain "ladies" coming into the pub for "a light". Most of the red light area is more discreetly hidden away towards Derby Road, though.

The Honest Lawyer is now called the Bent Brief (no kidding).

Alex
 
albertli

albertli

Member
Joined 2004
Hi guys.

I've just finished my Bevois Valley amp with all the old parts sitting on my shelf for a long time. The ptx doesn't come with any low voltage for filament and I put another 6.3v 5A for that purpose.
Rectifier are 4 UF4007 to 200uf murdorf condenser, to 10H 200mA choke, to 200uf murdorf condenser then to regulator. Everything 100% with the schematic, square waveforms are good on bench from 20 to 15K with just minor spide from 15K up. I then put on some music and found that I heard the radio???
I lifted the ground up with a ' box rectifier, 10R and 0.1uf ' to ground with no avail and the voltage on each cathode with big different. But I found everything seems normal when I put the positive probe of my multi meter on the first 6dj8 anode.
Would somebody give me a hand on this.
Thanks in advance

Albert
 
EC8010

EC8010

Ex-Moderator
Joined 2003
albertli said:
I then put on some music and found that I heard the radio???
Click to expand...

Do you mean you're hearing a radio station with no input to the amplifier? If so, I'd start looking at layout around that ECC88.

Edit: I just saw your other point about the meter on the anode. Yes, that sounds like RF oscillation in the first stage. Check your earthing, your power supply RF decoupling, and grid-stopper resistors. Long loops around the grid/cathode circuit can cause problems. Another possible cure is 10n capacitors from each heater pin to chassis with really short wires. "Really short" means that if you could remove 2mm from the wire it's too long.
 
albertli

albertli

Member
Joined 2004
EC8010,

'Do you mean you're hearing a radio station with no input to the amplifier? If so, I'd start looking at layout around that ECC88.'

I certainly would look deeply into this and otherwise I'd take it down and redo it.

' I just saw your other point about the meter on the anode. Yes, that sounds like RF oscillation in the first stage. Check your earthing,'

I hanged a copper wire (with the support) in the middle of tube socket, then I run a single wire back to star.

'your power supply RF decoupling,' Would take a look

'and grid-stopper resistors.' I have a 1K on (there is a 300R as of schematic )

'Long loops around the grid/cathode circuit can cause problems'
Sorry I don't understand this one.

'Another possible cure is 10n capacitors from each heater pin to chassis with really short wires. "Really short" means that if you could remove 2mm from the wire it's too long.

I have (2) 0.01uf to ground.

Thanks

Albert
 
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