Affordable but good MM phono stage.

pre65 · Post by **pre65** » Fri Dec 09, 2011 8:04 pm

Nick wrote:It all depends on the "noise", I think you are describing white noise through the RIAA curve,

What might cause that ?

Post by **Nick** » Fri Dec 09, 2011 9:57 pm

Noisy valves in most cases.

pre65 · Post by **pre65** » Fri Dec 09, 2011 10:05 pm

Nick wrote:Noisy valves in most cases.

Hmm.

I was bidding on some ECC803s but I lost out.

Ideally I'd like to "borrow" a couple of low noise ECC83 type valves just to see if it is my valves that are the problem.

Or, perhaps I need to get a couple of these, I already have one 5751.

http://www.hotroxuk.com/electro-harmoni ... -gold.html

or these ?

http://www.hotroxuk.com/jj-valve-ecc803s.html

Post by **Nick** » Sat Dec 10, 2011 1:43 am

Just try the one, you will see if the noise alters in that channel. (assuming its equal at the moment.

pre65 · Post by **pre65** » Sat Dec 10, 2011 10:20 am

Right so, off with the Phono3 cover and experiment with different valves.

1) remove 5751 from CF position and replace with ECC83 - no change.

2) replace the other two ECC83 with ECC82 - less noise and less gain

3) Take out ECC82 and replace with 1 ECC83 and 1 5751 - fair bit quieter on 5751 side.

So, another two 5751 should do me as a first step.

Post by **Nick** » Sat Dec 10, 2011 11:34 am

The cathode follower will not matter it ha no gain. Its the other two that matter. ecc82 will not work in this circuit, they are far from a equivilant.

pre65 · Post by **pre65** » Sat Dec 10, 2011 11:46 am

[quote="Nick" ecc82 will not work in this circuit, they are far from a equivilant.[/quote]

I appreciate that, they were "to hand" to use just to see what effect they might have on background noise.

Mike H · Post by **Mike H** » Sat Dec 10, 2011 3:06 pm

How is the heater supply organised?

pre65 · Post by **pre65** » Sat Dec 10, 2011 3:20 pm

Mike H wrote:How is the heater supply organised?

Regulated DC from the PSU3.

Mike H · Post by **Mike H** » Sat Dec 10, 2011 3:43 pm

More details? What's the regulator? I'm wondering if the "hash" is coming from the heater supply or wiring

pre65 · Post by **pre65** » Sat Dec 10, 2011 3:47 pm

Mike H wrote:More details? What's the regulator? I'm wondering if the "hash" is coming from the heater supply or wiring

Not sure cos the original reg was dropping out and John Caswell fitted a "different" one under warranty.

Mike H · Post by **Mike H** » Sat Dec 10, 2011 3:52 pm

AH!!! Maybe the new one is still only just managing?

pre65 · Post by **pre65** » Sat Dec 10, 2011 3:55 pm

Mike H wrote:AH!!! Maybe the new one is still only just managing?

I will find out what the current crop of PSU3 use for that part.

Mike H · Post by **Mike H** » Sat Dec 10, 2011 3:58 pm

Question #1 - what is the DC heater Voltage

Question #2 - what is the mains transformer heater winding AC Voltage

pre65 · Post by **pre65** » Sat Dec 10, 2011 4:04 pm

Mike H wrote:Question #1 - what is the DC heater Voltage

Question #2 - what is the mains transformer heater winding AC Voltage

It's difficult to measure with the units in situ, so they will have to go on the test bench.

Not today Josephine.

audio-talk

Affordable but good MM phono stage.

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