Bias Current Mythbuster?

[Audio_idiot]

Originally posted by Shoog


Hope that clarifies why perfect DC balance in the right type of PP transformers is important. In the wrong type of PP transformer it will tend to worsen the low level signal smearing.

Shoog

Originally posted by Jeb-D.


Yeah. E-I, by nature have a small gap since it is two pieces. Eventhough no gap is intentionally put there.

Hi guys,

Thanks for your elaborated explinations, your language is sooooo idiot friendly! Thousands thanks!!


Shoog,

Do your mean there is no point in current balance EI trafo to the dot? Or just attempt to achieve fair balance will do?

I'm soo tempted to try out toroaid power trans. Unfortunately its not freely available here. Maybe I can wind a simple pair me self.

Cheers

Ken

[Shoog]

I just messed about with the CCS on my amp and got them slightly better matched. One side went down from 2mA mismatch to 1mA mismatch and the other went down from 1mA to less than 0.5mA mismatch. The hum has all but gone from the one side and has about halved in the other. Heres the surprising thing - the bass has come up quite a bit and it sounds a lot tighter. It just shows how only a tiny amount of mismatch can bleed your inductance away. Also there is scary amounts of low level detail.

In answer to you question, I would avoid perfect matching with EI's it will probably lessen low level clarity. Winding your own toroids is not an easy job, it takes special machines. You cannot wind them onto a bobbin and then slip them on the core, they have to be wound onto the core. In order to get the primary inductance you would be wanting thousands of turns - not easy at all.

All of this has been something of a diversion from your original question. My experience is that quantity of bias current has a significant effect on the sound of the amp. Running the tubes current light creates a thin but detailed sound, running them hot- current wise- produces a much fuller fatter sound. Fortunately most of the benefit can be achieved by running your preamp stages hot and sparing the finals, this is because the benefit is generated by the preamp and then amplified by the finals. My experience is that the applied voltage is much less critical than the applied current. The starting point would generally be the recommended operating points to be found on the datasheets.

Shoog

[Audio_idiot]

Hi Shoog,

Ha3! Its so easy to go off track! even on one's own thread... it too darn interesting. Would you mind to point me to power OT as OPT related threads?

So back on track.

So DC bias cureent does have effect on sonic characteristic and current imbalance in the opt is a big no no.

What about AC balancing, doesn't it have close relation to the bias current?

Cheers

Ken