STAX: To charge or not to charge

[DannyB]

I have a KGSS and SR007 Mk2. I usually leave my KGSS on all the time. Is it best to leave the headphones plugged into the KGSS all the time to allow full charge or to just plug them in a little while before a listening session?

[catscratch]

AFAIK, the O2 charges up just about instantly. The sonic difference that is usually attributed to charge-up is mostly from components in the signal path warming up. The O2 is revealing enough that you'll hear warm-up clear as day.

I keep the 717 on almost all the time, but if you do that be careful with dust, and keep the phones well away from any possible dust contamination. The 717 needs to be well ventilated as it tends to get rather hot, but I have no idea how hot the KGSS runs.

[GPH]

My KGSS had always-on bias and I left the O2 plugged in all the time, so warm-up didn't apply, but when I had a T1S, the warming up of the tubes made a pretty big difference. Also, at a meet, I compared two O2, both plugged in a SRD-7 Pro and using a Quad II amp, one that was in there for quite a while and one that was just plugged in and I noticed a slight difference. Slight difference in meet conditions means probably no difference in real life.

Edited January 18, 2009 by GPH

[spritzer]

There is really no reason to keep the phones charged as they will be recharged in a fraction of a second.

[DannyB]

OK, then how about the KGSS? I usually keep solid state stuff on all the time and turn tube stuff off at the end of the day (amps not small tube equipment which I usually leave on most of the time).

So, is it wise or not to keep the KGSS on 24/7?

Thanks in advance Spritzer.

[Duggeh]

I've had problems in the past with the O2s taking many hours to come up to full efficiency after a period of non-use (been on holiday or such). The problem has gone since shorting out the pins before such periods, I now get full efficiency on a cold 717 and cold O2 right from hitting the power button, although it takes a bit for everything to warm up.

[spritzer]

If the change in sound from a cold to the amp being at regular running temperature is large enough then I'd run it 24/7 but you are eating up a lot of juice and shorting the life of the capacitors dramatically.

Like Doug said it is always a good idea to discharge the phones if you are storing them for any long period of time.

[tkam]

OK, then how about the KGSS? I usually keep solid state stuff on all the time and turn tube stuff off at the end of the day (amps not small tube equipment which I usually leave on most of the time).

So, is it wise or not to keep the KGSS on 24/7?

Thanks in advance Spritzer.

One thing to remember about the KGSS is with it being Class A even at idle it's using roughly 80W of power. So it will add to your monthly electric bill if you leave it on 24/7.

[Dusty Chalk]

I have heard varying reports of "wake-up time", and do not know if it is a result of the headphone charging up, or the amp warming up. I have heard reports of instant charging, and I have personally heard one pair of headphones not wake up until 7:30 (I actually didn't hear them wake up until days later). Anyone at one of Hirsch's early Rockville meets can attest to this (I believe Justin was there, as were canman and taylor). In hindsight, I'd say they were defective, but they sounded fine once they woke up.

So I say: suit yourself. Experiment. Listen to them cold (E.G. after being off all night), listen to them half an hour in, listen to them after being on for four hours. If they really don't sound any different, then I wouldn't leave them on all the time. If they take more than four hours, I'd get another pair. I just don't have that kind of patience (or the desire to pay those kind of electric bills and replacement parts bills -- because you will "use up" that amp faster as a result of keeping it on all the time).

[spritzer]

What does happen with electrostatics is that a charge of the opposite polarity sits on the diaphragm, impedes it movements and it takes the high impedance bias supply a while to get rid of it. This has happened to my O2's once and took a few hours to get rid of it but the effect was very strange indeed. The best way to prevent it is to always discharge the diaphragm when unplugging the phones. This is also the main reason for the dreaded channel imbalance and can be a PITA to get rid of.

[Dusty Chalk]

But why would it repeat? One would think that once one got rid of the contradicting charge, that it would be gone.

Unless it's a static parasitic charge that isn't so much "gotten rid of" as "sufficiently counter-balanced with the appropriate electrical charge"...that was supposed to be a question.

[spritzer]

It is indeed a static parasitic charge that builds up and the bias supply has to get rid off. The bias supplies are by design very weak so it can take them a while to overcome the charge. It's enough of an issue that Sony designed a semi conductive housing for their electret drivers as with them there is no way to reach the membranes from the outside.

I have no idea what causes it but there seem to be a lot of this going in in the last month or so with all manner of Stax phones.

[peanutbutterjam]

What does happen with electrostatics is that a charge of the opposite polarity sits on the diaphragm

How does an opposite charged gets "stuck" there? Wouldn't the charge be neutralised by the biasing charge instantly?

it takes the high impedance bias supply a while to get rid of it.

Erm how is that so? I mean the biasing supply can charge up the membrane from 0V to the biasing voltage in split seconds when you plug in your phones. Removing the stray charge should not require anywhere as much current right Unless there are so much opposite charges on the membrane that the membrane holds a net opposite charge, but that seems impossible given the potential energy.

[spritzer]

You are aware how electrostatic membranes function, right? On traditional constant charge drivers such as the ones Stax builds, the membrane is highly resistive and single ended. The bias supply is high impedance (as in it has little to no current to give) so the bias is just "pushed" onto the diaphragm. There is no flow as it is an open circuit so it's hard for it to get rid of a large charge that just sits there in one of the isolated "hot spots" which appear, mostly due to the uneven resistivity of the diaphragm.