nuvistors

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Nick
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#46

Post by Nick »

Yep, matching the filter comps make a huge difference in my experence. I like to use 0.1% resistors and 1% caps, buy a bag of 10 of them and then hand match to find the closest pair. I dont know how accurate my meter is in terms of absolute measurement, but I know I can match caps to within 0.1% of each other.
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cressy
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#47

Post by cressy »

i can match the resistors easily enough as they all came in bags of 50 (although i didnt bother :roll: ) i'll do that when i start the new casework

im not sure my meter measures capacitance but i think mi old mans meter does. i'll need to buy more caps to match them up so i'll do that too

cheers ant
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Nick
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#48

Post by Nick »

cressy wrote:i can match the resistors easily enough as they all came in bags of 50 (although i didnt bother :roll: ) i'll do that when i start the new casework

im not sure my meter measures capacitance but i think mi old mans meter does. i'll need to buy more caps to match them up so i'll do that too

cheers ant
I find it a lot less pain just using 0.1% resistors from Rapid.
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#49

Post by cressy »

ive started the new casework for the phono stage and am wondering about sheilding.

the new casework is made of solid beech strips and divided in to two compartments. one will have a solid top housing the psu above and below, and the other a mesh top with the circuitboard underneath. the other half has some copper tape to stop slugs eating her plants, so i got round to thinking the tape could be used to line the inside of each section.

would this provide a reasonable amount of sheilding? i assume i can solder an earth to the tape or if this is a reaonable idea would it be better to put a bolt throught the case with a ring connector tightened up against the tape?

incedentally i also have a large brass kick plate off a door that i can cut about to act as sheilding.
im still getting to grips with noise reduction, this is the first phono ive built
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Mike H
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#50

Post by Mike H »

I'd have a go with the copper tape.

This 50W resistor that's getting hot, what's it screwed onto, metal or what?
 
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#51

Post by cressy »

i got the new case built and everything fitted up. took abit of lateral thinking to get it all to fit due to the fact that as usual i built the case for looks and didnt consider how to make it work :roll:

all the transformers are in the right hand section behind the rectifier and the board itsself is in the left.

better reconnect it all..........

Image

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Toppsy
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#52

Post by Toppsy »

Very nice there young Ant.

As DTB would say VERY SHODDY!
Max N
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#53

Post by Max N »

Wow! Lovely job! I like the way it continues the lines of the CD player.
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Paul Barker
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#54

Post by Paul Barker »

I recall from the past there was a nuvistor phono stage article was it Eric Barbour? Or was it a line stage? I forget. I would have no hope of finding it.
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cressy
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#55

Post by cressy »

conrad johnson sold one in the 80s using 6cw4s but i couldnt find much info in terms of diy circuits. there are some references here and there to an eric barbour designed one but i couldnt be bothered to spend the time finding it :)

re the design for the box, i wanted to tie the amp and the cd player features together in one unit, the most defining of the cd is the shape and the most defining of the amp is the acres of beech with the gloss black acrylic. it isnt quite right as the feet are too short by about 5mm. with the taller feet on it you should be able to lay a ruler on the side of the cd player and it should rest on the side of the phono. i wanted a continuous line straight up.

i put too much consideration into boxes and not enough into whats inside :)
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#56

Post by Mike H »

Max N wrote:Wow! Lovely job! I like the way it continues the lines of the CD player.
Yes, all pyramid like innit. Very impressive. :D
 
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Paul Barker
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#57

Post by Paul Barker »

cressy wrote: there are some references here and there to an eric barbour designed one but i couldnt be bothered to spend the time finding it :) :)
somewhere in one of my "glass audio" mags I expect the article lurks. I would be happy to bring them all to a meeting but they will go back home with me. Anyone who wants to find interesting articles and glean them on the day is welcome. But i wouldn't part with the material which was key along with profucely studying the websites of Steve Bench and Sukuma San to my upbringing. I don't have time to scour them myself right now.
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cressy
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#58

Post by cressy »

ive finished rebuilding the thing and hit a snag. on checking the heaters, voltages ect before connecting anything i checked the ht on the supply rail on the board. i measured just short of 500v.
it should be 224v
first thought was that the c/t on the ht winding wasnt connected but checking continuity i found it was. i checked every earth in the amp and theres continuity on all of them. i checked what was coming out of the psu before the 5k resistor and measured nearly 700v.

im errr baffled. any ideas?
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pre65
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#59

Post by pre65 »

Oh dear. :shock:

Have you posted the psu details ?

PS is the transformer primary wired for 240V ie have you got the two 120v secs mixed up ?
Last edited by pre65 on Tue Sep 20, 2011 7:09 pm, edited 1 time in total.
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Ali Tait
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#60

Post by Ali Tait »

Your meter ok?
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