L0rdGwyn's DIY Audio

[2359glenn]

Craziness.

 

[L0rdGwyn]

Tuff wire to work with I use it at work to feed power and signals to sensors. High power frequency drives with a 480 volt 50amp square wave to a motor puts out plenty of noise

Yeah, that jacket is THICK. Could stand to be a bit thinner and more flexible, but in every other way it is exactly what I need for this phono stage, so I'll take it!

 

[2359glenn]

Yeah, that jacket is THICK. Could stand to be a bit thinner and more flexible, but in every other way it is exactly what I need for this phono stage, so I'll take it!

Did you buy that short piece? I usually have to buy it in 100ft roles don't matter I use it all.

 

[L0rdGwyn]

Did you buy that short piece? I usually have to buy it in 100ft roles don't matter I use it all.

I found a site that will cut and sell by the foot, I bought 10 ft: https://www.wireandcableyourway.com/.

 

[Zachik]

price on the pair was around $15k (USD). I'm not one of those "a cable is a cable" kind of people, but even I have limits.

Yup - also called "credit card's line of credit"

 

[Tjj226 Angel]

Now there is a cable only a mother can love.

 

[L0rdGwyn]

Got some work in on the phono stage today, finished the power supply.

Heater regulators are dialed in to 6.3V, threw a dummy load on the Maida to set the B+.



The rest should be pretty simple, going to finish it tomorrow barring some unforeseen catastrophe.

 

[bcowen]

Got some work in on the phono stage today, finished the power supply.

Heater regulators are dialed in to 6.3V, threw a dummy load on the Maida to set the B+.



The rest should be pretty simple, going to finish it tomorrow barring some unforeseen catastrophe.

Sweet! That's a righteous looking transformer in there...

 

[L0rdGwyn]

Sweet! That's a righteous looking transformer in there...

Thanks it's actually a cheap Antek toroid, since the supply is regulated the mains traffo doesn't need to be anything fancy-schmancy, the black steel pot helps control leakage of magnetic flux to minimize any magnetic coupling.

 

[L0rdGwyn]

Tube socket wiring done, have to show it now, going to be buried here pretty soon!



Goal is still to finish today, onward!

 

[bcowen]

Tube socket wiring done, have to show it now, going to be buried here pretty soon!



Goal is still to finish today, onward!

You truly know how to do it right. Love those carbon films....was just getting ready to swap out the cheap metal films in the Darkvoice project with these (stashed long ago):

 

[L0rdGwyn]

You truly know how to do it right. Love those carbon films....was just getting ready to swap out the cheap metal films in the Darkvoice project with these (stashed long ago):

Are those Riken Ohm carbon films? Those are my favorites I typically use them on tube cathodes, have them unbypassed on the driver tube cathodes of my 6A5G amplifier and the 6J5 drivers of my 45 amp.

But...sadly...those blue resistors in the phono stage are actually metal films since the goal is lowest possible noise in the phono stage, decided to go with the lowest noise resistor in most places. I have a little stash of Riken carbon films on standby though the grid stoppers in the phono stage are Allen Bradleys.

 

[L0rdGwyn]

Checking bias points with LED bias glow...here they are.

D3a: Va 138V, Vk 1.21V, Ia 19mA
EF86: Va 120V, Vk 1.58V, Ia 4mA



Also measured the input capacitance of the EF86 as it will need to be compensated for in the RIAA filter - that is, it is part of the filter. Measured at 240pF for one of my EF86, 260pF for the other.

 

[bcowen]

Are those Riken Ohm carbon films? Those are my favorites I typically use them on tube cathodes, have them unbypassed on the driver tube cathodes of my 6A5G amplifier and the 6J5 drivers of my 45 amp.

But...sadly...those blue resistors in the phono stage are actually metal films since the goal is lowest possible noise in the phono stage, decided to go with the lowest noise resistor in most places. I have a little stash of Riken carbon films on standby though the grid stoppers in the phono stage are Allen Bradleys.

I was looking at the Allen Bradleys. Those are carbon, yes?

And yes, mine are Riken Ohms. Don't even know how long they've been in the stash -- probably 20 years? Love the sound of them, but the Allen Bradleys are a good runner up (IMO). Plans are to swap out the (cheap) metal film 6SN7 cathode bias resistors with the Rikens in the Darkvoice, but I was also planning on a cap bypass. Perhaps I should try them alone?

 

[L0rdGwyn]

I was looking at the Allen Bradleys. Those are carbon, yes?

And yes, mine are Riken Ohms. Don't even know how long they've been in the stash -- probably 20 years? Love the sound of them, but the Allen Bradleys are a good runner up (IMO). Plans are to swap out the (cheap) metal film 6SN7 cathode bias resistors with the Rikens in the Darkvoice, but I was also planning on a cap bypass. Perhaps I should try them alone?

That's right! They are carbon films, grid stoppers for preventing parasitic oscillations.

The issue with leaving the cathode resistor unbypassed (known as cathode degeneration) is it will increase the internal resistance of the tube and you will lose gain. I don't know a ton about the Darkvoice, but I think it is a cathode follower output. Cathode followers don't suffer from the Miller Effect and have a low input capacitance, so you MIGHT get away with it, but I would probably leave it bypassed. Using a CCS load minimizes the above negative effects of an unbypased cathode, which is what I have done in my amplifiers.

If you really wanted to get crazy, you could CCS load the 6SN7, then leave the cathode unbypassed