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01-07-2019 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 456
Joined on 01-07-2006

Post #: 151
Post ID: 25231
Reply to: 25230
EI vs toroids
Congratulations on the build!

 anthony wrote:
  Yours uses all toroids, or mostly so, which are more efficient than the EI that I use.

Why have you chosen EI vs toroids? The latter emit less.

Cheers, Jarek



Cheers,
Jarek
01-08-2019 Post does not mapped to Knowledge Tree
anthony
Posts 206
Joined on 08-18-2014

Post #: 152
Post ID: 25232
Reply to: 25231
Its about noise
 N-set wrote:
Congratulations on the build!

 anthony wrote:
  Yours uses all toroids, or mostly so, which are more efficient than the EI that I use.

Why have you chosen EI vs toroids? The latter emit less.

Cheers, Jarek

Hi Jarek,

Yes, toroids can leak less magnetic flux than EI if they are wound such that the entire core is covered, but is flux leakage a problem if you are able to keep the transformers away from sensitive circuits?  Toroids come into their own when you are forced to mount the transformer near the circuits, but otherwise EI have them covered on most fronts.

Toiroids
  • are smaller for the same power rating
  • are more efficient transformers of power than EI
  • if carefully made can have low flux leakage
  • are high bandwidth devices so more noise on the power line is transferred into the circuit
  • have no gap and will hum when there is DC on the mains


EI
  • are larger for the same power rating
  • have a gap and do not hum when you have DC on your mains (unless there is so much that the core becomes saturated)
  • are lower bandwidth devices so act as a low pass filter for mains noise (we really only need to pass 50/60Hz - the rest is unwanted)
  • leak some flux so they should be kept further separated from the sensitive circuits


Personally, I would use EI in just about every situation for audio...unless I had no option but to tuck the transformer in tight to a sensitive circuit.


Cheers,

Anthony
01-08-2019 Post does not mapped to Knowledge Tree
anthony
Posts 206
Joined on 08-18-2014

Post #: 153
Post ID: 25233
Reply to: 25232
The pin 8 question
Hi Romy,

I've been reading the 6e6p-dr datasheet and it seems as though pin 8 (a shield) is recommended to be tied to a lower negative voltage than the tube cathode.  Have you bothered or experimented with this?  This is no problem in the DHT Channel because of the cathode resistor, but in Channel D the cathode pin is connected directly to ground and I don't know how to get a potential lower than ground.
Regards.
Anthony
01-08-2019 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 456
Joined on 01-07-2006

Post #: 154
Post ID: 25234
Reply to: 25232
Cont'ed
Anthony, thank you for the explanations. For some reasons you mention, I use C-cores. Loose coupling (pri and sec on the different legs), controlled gap and low emission. BTW toroids do have some "distributed gap" but it's small and uncontrollable.

Cheers, Jarek



Cheers,
Jarek
01-09-2019 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,560
Joined on 05-28-2004

Post #: 155
Post ID: 25235
Reply to: 25233
A good question.
Anthony, I grounded in my amp it in order the shield was not hanging there free. You certainly must NOT leave it disconnected and you do need to tie to something. Generally biasing of these electrostatic fields shields is very murky territory. There is a community of people out there who insist that it makes difference and I have seen even some gizmos that introduce bias to external shields. The shields in 6E6P is much closer to anything, so a positive or negative bias might be effective. I did not experiment with it and I have no way to predict how it might impact sound. Do not take it too far as I can see you running an active feedback loop over the 6E6P shield… :-) 
 
Let me know if you do experiment with it and what you find. I would be looking for noise and sound impact. Do not forget to burn a used tube at least 1Hr before you make any judgments. It might be hard for you as you do not have 6E6P in a full bandwidth channel and to make any concussion within a narrow bandwidth channel you need the whole system to be setup, calibrated and it sound to matured in your own perception.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
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