Valve Itch phono

[Salas]

Salas, do I remember correctly that that you pointed out that there will be DC at the input and a blocking cap should be used in the absence of a transformer to protect the cart coil?

Edit: Yep, in post 4.

Usually innocuous, but its advised to check with a DMM on mV DC that there is no appreciable voltage on the input from a leaky valve before hooking up an MM cart straight. Although rare, it could be.

 

[merlin el mago]

1578 tube can be used instead 6SN7? hole plate is better, why?

 

[Salas]

Haven't used it ever. There was a thread: http://www.diyaudio.com/forums/tubes-valves/63574-russian-6n8s-1578-a.html

 

[merlin el mago]

Can I buy 2 MELZ 6N8S / 6SN7 tube metal base (hole plate) for $100.00, it's a good price?

 

[bobrown14]

Can I buy 2 MELZ 6N8S / 6SN7 tube metal base (hole plate) for $100.00, it's a good price?

$50 per tube - you probably wont see them any cheaper these days. Bought a bunch a few years ago for around $40 per but that was a good deal and I was patient and looked for a while. They are the best 6SN7 tubes I've heard and are at least as good as the RCA 5692 rugedized version. As good as they sound, my results varied, a few were microphonic. I stoped looking for them after 2 went microphonic. So I suspect some on the market were rejects from the factory even tho they have the OKT stamp on them. I started buying the 5692 RCAs as they are much more reliable and last virtually forever in audio and sound almost as good, very close 2nd in my gear.


Cheers,
Bob

 

[merlin el mago]

On ebay a couple starting from $100 to $174 all metal base but not hole plate, I see a couple very interesting but a little expensive circa $140 but measurement is very good

Thanks,
Felipe

 

[woodturner-fran]

Maybe don't get too caught up in the tube rolling yet - save it for later after you have it up and running and when you're finished with caps etc....

The $100 will bu a lot of the rest of the parts...

 

[bobrown14]

On ebay a couple starting from $100 to $174 all metal base but not hole plate, I see a couple very interesting but a little expensive circa $140 but measurement is very good

Thanks,
Felipe

Pass on them - THE only 6N8S worthy of that price are the round hole versions.

Cheers,
Bob

 

[merlin el mago]

Maybe don't get too caught up in the tube rolling yet - save it for later after you have it up and running and when you're finished with caps etc....

The $100 will bu a lot of the rest of the parts...

Pass on them - THE only 6N8S worthy of that price are the round hole versions.

Cheers,
Bob

Hey guys,

Thank you very much for your good advices.

Felipe

 

[merlin el mago]

Partridge 977

Just arrived the couple of partridge 977 for the Itch could you help me to wire up, there is 1 red pin, 1 yellow pin & 2 green pins connected, attached pic:

 

[RCruz]

Look here: http://www.diyaudio.com/forums/analogue-source/192302-how-wire-up-mc-step-up-transformers.html

 

[merlin el mago]

Thanks Ricardo, still not clear wich one is the input or output?

Felipe

 

[merlin el mago]

Partridge 977

kevinkr give me the answer: the red pin is the output and the gold/yellow is the input

 

[merlin el mago]

DL103R (0.29mV output) + Partridge 977 1:6 + Valve Itch 48 dBs will be enough gain?

 

[Salas]

Yes.

 

[merlin el mago]

Ufff, thanks Salas now I am calm.

 

[woodturner-fran]

For anyone else - the linked pins are the grounds. If you measure the resistances, the input side has a resistance of about 25-30R and the output side is higher, can't remember, but significantly higher.

BTW, I broke the link between the grounds - there was some discussion on this back earlier in the thread, about pg 10-15 something like that


Fran

EDIT: my cart is 0.35 and its plenty loud enough with the partridge 977....

 

[merlin el mago]

See the sch in the pic below:

An externally hosted image should be here but it was not working when we last tested it.

He ties gnd on the primary side to gnd on the secondary. Salas, I note you didn't do this in your schematics, although there was some discussion about it back a little. Both version of yours are working fine? No need to follow that common gnd?


Made more progress tonight. The transformer box is done, next up is the umbilical from phono box to transformer box. Then I can start on the circuit itself - thanks to the arrival of some nice matched caps from Poros Island......

We will see which is most IMF-affected postal service... I'm already guessing it is the Irish one!


Fran

It worked better for hum with the primary floating for ''balanced'' transfer, but it worked both ways.

So better don't have connected both gounds & left floating as per Salas advice.

Did you connect the step-up tx to chassis gnd as pic to avoid hum?

 

[Salas]

You are quoting my findings from another SUT model. You will see when you will have a properly working phono as for what is best with the 977 and your TT grounding.

 

[merlin el mago]

That's a good advice as always, I will follow experimenting with my own Itch.