[CButterworth]

I have already sourced most of the parts for the Cornet2, and I'll try it first without changing my l-pad.

The manual for the Cornet2 says that the LED goes from red to green after 20 seconds.  I guess that this is due to "switch-on" of HT?

Anyway, I am using a Belkin PureAv to delay switch-on of my main amp by 15 seconds, with my preamp applying HT after 10 seconds of tube heating.  This means that I only use the power conditioner to switch on my entire system.

So, how can I reduce the Cornet LED red to green to about 10 seconds?

Charlie

[WGH]

Indirectly heated tubes like the Sovtek 5Y3 may take 20 seconds for the light to turn green. A directly heated rectifier like a RCA 5Y3GT will turn the light green in a second or two.

The Cornet2 makes a slight noise when it is first turned on (got to remember to turn down the volume), there is no noticeable change from red to green, it is completely silent. As long as the Cornet2 is turned on before your amp I would not worry about the red/green delay.

[CButterworth]

Great, so I guess that I'll go with a directly heated rectifier like the RCA.  My main amp is automatically switched on after 15 seconds, which is why, I'd prefer a Cornet2 with a quicker change in spite of the complete silence when LED goes from red to green (isn't this simply indicating full HT power?).

According to John Broskie (designer of the Aikido), the tube configuration should prevent turn-on/off thumps.  In my system this is not the case, so I am going to go the more paranoid route with the Cornet2.

Thanks,

Charlie

[samplesj]

Ummm..... Doesn't it take you more than 20 seconds to get a record out, put it on the platter, clamp, brush, and cue it up?

Direct heated rectifiers may "hurt" (cathode stripping) the 12*7 tubes because they will see B+/HT too fast.  With Sovteks there it may not be a big deal, but that would be aweful to lose a nice pair of (N)OS tubes (or even good current production).

Why the rush?

[CButterworth]

Of course it takes more than 20 seconds to get out a record,  BUT.... my system is set-up so that a single flick of the switch allows all gear to be switched on.  The switching is done entirely via the PureAv console:

1.  I switch on the PureAv
2.  Immediately, the Aikido preamp is powered-up, as is all other gear except for power amp.
3. An amperite delay relay in the Aikido heats the heaters for 10 seconds before automatically switching on the HT.
4. After 15 seconds (from 1 above), the PureAv switches on my main amp.

In other words, the application of HT in the Aikido is done before the main amp is on.  This means no scary bumps or thumps. Switch off is in reverse (with the exception of the delay in the Aikido) - no scary bumps or thumps.

This means that my wife, myself and house guests can play music without having to worry about switching on the main amp last, and switching off the main amp first, etc.

The crunch is that the PureAv can only delay for 15 seconds.  So, if I have 20 seconds of heating in the Cornet2, it's B+ will be applied 5 seconds after the main amp is on leading to possible scary bumps and thumps.

As for cathode stripping, I read that it isn't really a problem with the lower voltages seen in audio equipment (less than 1kV), and that cathode poisoning was more of a problem if the B+ is delayed for too long!  I also believe that many tubes are sufficiently heated after only a few seconds.

Charlie

[GRD]

Very sensible.  I'm always a bit paranoid about turn-on transients with my tube preamp feeding the SS amp.  The 5Y3 will deliver voltage in a few seconds.  I've used an RCA 5Y3 in the Cornet with no ill effects to my preamp tubes I could find. 

You may also find the gentle voltage ramp-up of an indirectly heated rectifier doesn't  cause any problems either, as the downstream tubes are hot and conducting when the voltage starts to come up.  You can always put a meter on the pre-amp output and see if there is any voltage swing during the turn-on cycle.  But then, that just leads to more tube madness - rectifier rolling.

[Eric H]

Hi Charlie,

I've got a NOS JAN Philips 5Y3WGTA (maybe two of them?) that you can have.  I bought it from angela.com, I think, and didn't use it because it's directly heated.  If you want it I'll send it to you - it's not an expensive tube and I don't have any use for it...

Eric

[hagtech]

As for cathode stripping...

Indeed, the more had I read on this subject the more I found out it was an issue with higher powered output tubes, not the little preamp tubes.  I think it was discovered in radio transmitters.  Tubes like a 211 or 845.  They call it poisoning but it might actually be more of a stripping (as Charlie said), where the delicate cathode coatings get damaged (in small hot spots?).  Not enough electrons supplied at the lower (room) temperatures.  Application of this effect onto 12AX7 and other baby tubes was probably an urban myth back in the day.  But hey, you know how we audiophiles are, we worry about everything.

jh

[CButterworth]

I fully appreciate the "audiophile" bug.  I am continuously wondering whether I am able to squeeze more out of my system (I really do need new speakers, but they'll have to wait until we build a new house!).  However, I am willing to undergo the minor worry of possible (but very unlikely) issue of cathode stripping in order to have the peace-of-mind that comes from knowing that my amp and speakers are protected from switch-on transients 

Charlie