[deerinheadlights]

What about the CRDs. My glass jar kit came with the J508 and J511 CRDs. I changed to the 1N5307 and 1N5314 CRDs because they have better specs but I have no idea if it really changed anything for the better.

 

[johnwmclean]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif surely one cannot make this statement categorically? Perhaps the builder plans on stacking the PSU on top of a low-output moving coil phono stage?

Shoot the builder

otherwise I stand firmly by what I’ve stated, categorically. A shielded transformer is not necessary for a two chassis build.

 

[amb]

Quote:

Originally Posted by deerinheadlights /img/forum/go_quote.gif What about the CRDs. My glass jar kit came with the J508 and J511 CRDs. I changed to the 1N5307 and 1N5314 CRDs because they have better specs but I have no idea if it really changed anything for the better.

The benefit of the 1N5xxx CRDs is tighter tolerance and higher voltage rating. Neither of these would result in sound quality differences, but some applications (i.e., 36V output σ22 and σ11) require the higher voltage rating for adequate safety margin. Also, Vishay-Siliconix has stopped manufacturing the J5xx CRDs, so the 1N5xxx series may sometimes be the only option.

Quote:

Originally Posted by fsrick If I use a separate chassis for the power unit, is it still necessary to do the shielding? I heard the interference will go away if we place the transformer in a different chassis (it is steel/aluminum, not wood).

The whole point is to reduce magnetic field interference from the transformer to the amplifier. If you use a separate chassis to house the transformer(s), then it allows you to put them some distance away from the amp chassis. In that case shielded transformers are not necessary. If you cannot put the transformer far away (i.e., single chassis, or if you must stack one on top of another). then shielded transformers may be needed to prevent hum and noise. A steel chassis (or some other ferrous metal, or mu-metal) might help provide some shielding, but aluminum does not.

 

[n_maher]

Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif Shoot the builder otherwise I stand firmly by what I’ve stated, categorically. A shielded transformer is not necessary for a two chassis build.

And I disagree categorically. There are plenty of situations where shielding would still be beneficial if not necessary.

 

[johnwmclean]

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif And I disagree categorically. There are plenty of situations where shielding would still be beneficial if not necessary.

And what situations would they be?

 

[Pars]

Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif And what situations would they be?

Obviously single chassis, which I still feel has some advantages if you can do it. Stacking the amp and PSU would also be one. Also, any situation where the PSU is near anything else that might pick up EMI, such as sources, etc.

 

[Beefy]

Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif And what situations would they be?

To my understanding, the benefit of using two cases isn't the shielding the case provides, but the benefit of increasing the distance. So if you had aluminium cases, a shielded transformer might still be very desirable.

And as mentioned, proximity to sources etc. might cause interference.

 

[johnwmclean]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif To my understanding, the benefit of using two cases isn't the shielding the case provides, but the benefit of increasing the distance. So if you had aluminium cases, a shielded transformer might still be very desirable. And as mentioned, proximity to sources etc. might cause interference.

In that case I stand corrected, I actually thought the chassis formed the basis for the shielding within a two case build.

Problems with one enclosure builds are clearly documented within these forums where the use of a shielded transformer was necessary, but I have never come across a scenario where a builder has had problems with noise from an unshielded transformer in a two case build.

Case in point would be the group build, Krmathis stacks his amp and I believe the amp preforms flawlessly, my own amp is another case.

 

[Beefy]

Well according to this first hit from a google search, the magnetic permeability of aluminium is the same as air, and thus no more effective than air for shielding.

 

[johnwmclean]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif Well according to this first hit from a google search, the magnetic permeability of aluminium is the same as air, and thus no more effective than air for shielding.

you got in before my edit, see my above post.

 

[amb]

Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif ... Case in point would be the group build, Krmathis stacks his amp and I believe the amp preforms flawlessly, my own amp is another case.

Don't forget that krmathis uses high-impedance or low-efficiency headphones (e.g., AKG K1000) with that amp, so any magnetic interference will be rather inaudible. I tested the amp with my HD600s and it's dead silent when the two cases are stacked, but try a low-Z can and see...

Of course, move the two cases apart and the slight noise disappears for just about any headphone (except perhaps IEMs, which will exhibit a little hiss due to the high amp gain).

 

[johnwmclean]

Thank you for the clarification, I was under the wrong assumption - and I’ve learnt something new - cheers guys

 

[luvdunhill]

Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif Thank you for the clarification, I was under the wrong assumption - and I’ve learnt something new - cheers guys

assumptions make poor categorical statements... categorically speaking, of course

 

[Possede]

I'm thinking of putting one of these on the front panel of my β22 chassis via the ε22 backplane. Their operating current is 6-16mA, so using a 24V σ22, I'd be looking to use ~2kΩ resistor, right? (I = V/R)

 

[cfcubed]

Found myself short a couple 33pf for C1 with 100pfs available... Would be detrimental to use the 100pf for C1s (perhaps until a future parts order)?

BTW I do have the proper C2 - C5 for my target gain.

TIA for any advice.