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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 23rd Jun 2021, 11:16 am   #1
Welsh Anorak
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Default Noname two-valve record player query

Hi
I'm involved doing a UY85/UL84 record player using a BSR TC8 turnover cartridge.
It's similar to the Dansette Viva using as few components as you could get away with.
My slightly unusual problem is that there seems to be too much gain! It works, but if the volume is high with no record playing it has a lot of 'here I am' background hiss - not really hum. Also it's loud enough at around a third of the control. I've changed the cathode decoupler and the resistor's OK but there's not much else to go wrong. The voltages are what I'd expect and the smoother's OK. Any ideas, other than to keep the volume low?
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Old 23rd Jun 2021, 11:25 am   #2
Edward Huggins
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Default Re: Noname two-valve record player query

That's strange - a distinct lack of gain on these single-stage amps is ususally the problem.
Is this apparent on touching the volume control sider or with the cartirdge in use? It should be a BSR TC8H orange bodied type.
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Old 23rd Jun 2021, 1:37 pm   #3
Welsh Anorak
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Default Re: Noname two-valve record player query

Yes - that's the one. I might just be a little too critical. If I disconnect the input the hum is still there, though as I said it's more an earth loop noise than a mains hum if that makes sense, and at zero volume the amplifier is quiet.
The difference between this one and the Dansette is that the cartridge is coupled (and decoupled) by low vaue capacitors. Possibly an attempt to introduce a slight safety aspect - especially as the original mains lead was non-polarised with one core going to chassis!
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Old 23rd Jun 2021, 4:39 pm   #4
Herald1360
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Default Re: Noname two-valve record player query

Capacitors in both leads to the cartridge is usually a recipe for more hum and noise. You could try (temporarily and carefully with chassis definitely at neutral) shorting out the cap in the signal 0V line to see if it makes any difference. Not that there's much you can do if it does .
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Old 23rd Jun 2021, 4:49 pm   #5
Edward Huggins
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Default Re: Noname two-valve record player query

They will be there for no other reason than safety as the amplifier is a live chassis type. Replacement "Y" class caps of a similar value are recommended. Regarding hum, do not attempt any earthing on this player and ensure that the mains Neutral goes to the chassis. Please advise how loud is is when playing a MONO LP - definately not Stereo! That is the acid test for volume levels on a player of this type.
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Old 24th Jun 2021, 9:16 am   #6
Welsh Anorak
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Default Re: Noname two-valve record player query

I am actually using a mono single to test it. It's surprisingly loud! I think I'll just advise the owner to play it at a reasonable level. Would you believe she likes it so much she bought a new sofa to match?!
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Old 24th Jun 2021, 1:20 pm   #7
Edward Huggins
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Default Re: Noname two-valve record player query

It will sound "loud" on a single and even louder on a 78.
But as I suggested, the real test to is try this on an LP - and on this player a Mono LP.
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