[MaskdBagel]

I'm building a Cornet2 right now, and it's my first DIY project of this scope. It's going well so far, but I keep wishing I had a masterfully assembled one to refer to from time to time. Does anyone have a nice large photo of a finished board or a few minutes to take one for me? (With the transformer wires pulled out of the way would be REALLY nice, but now I'm just being obnoxious.) Also, looking ahead, I'm not sure exactly how to install the RCA jacks (I'm kind of a noob, if you can't tell), so I'd love some guidance/photos for that bit as well. I'm using the S-H267s from AES.
Thanks very, very much.

Kent

[analog97]

This is the best I can do for you.   It works jes' fine and dandy!!!!

[WGH]

Here is a view from the rear. The  6 big silver tubes are the Russian FT-3 caps, they enhance the air and sparkle factor when used with Mundorf caps.



Notice the two parallel resistors at R223, these adjust your heater voltage (H+). The goal is to adjust H+ to get close to 6.3 V. More information and a calculator can be found here:
http://www.audiocircle.com/index.php?topic=41430.0

You are going to love this pre-amp.

Wayne

[PatOMalley]

since you ask ...




http://home.comcast.net/~omaille/audio/cornet2/cornet2.html

[Theo]

Hi Pat,

I'm trying to hunt down the source of excessive hum on my Cornet2.  I would like some detail on the measures taken to reduce hum.  I see you have a ground wire going to the transformer and a grounded shield.  Would you please detail a bit on these mods?  Thanks in advance.

[PatOMalley]

Theo,

The ground wire from the transformer shield made a big difference.
the copper didn't make any difference I could hear. I think the Ferrite lowered the noise level a small bit. Biggest difference was using 5751 tubes instead of 12AX7.

Best so far have been the RCA black plates. Wide open, clean, extended, etc.
Got a GE and another one in the mail. Those sound thicker but have some kind of spooky 3Dism thing. I will know for sure once I get the second one in there.

Using the 5751 I can turn it up enough to not notice the hum.

[WyldRage]

Hi Pat,

I'm trying to hunt down the source of excessive hum on my Cornet2.  I would like some detail on the measures taken to reduce hum.  I see you have a ground wire going to the transformer and a grounded shield.  Would you please detail a bit on these mods?  Thanks in advance.

I have just finished building my Cornet 2, and had a problem with humming as well. Here are the steps that I took to solve it:

1. Put a wire between the transformer and the grounding post. Looking from the back, I put it in the lower left screw, since it looked like it had a metal washer. Before I had done this, when the Cornet 2 was running, I coud sense the static electricity when running a finger on the top plate; now there's none.

2. "Float" the RCA connectors, meaning that they should not touch the chassis.

3. Connect the grounding post to the ground of the turntable (don't know if this helps or not, but it didn't hurt).

These removed any audible hum. I have to put my headphone amps at maximum to hear anything now.

[PatOMalley]

1. Put a wire between the transformer and the grounding post. Looking from the back, I put it in the lower left screw, since it looked like it had a metal washer. Before I had done this, when the Cornet 2 was running, I coud sense the static electricity when running a finger on the top plate; now there's none.

my wire goes to the internal ground. Do you mean you ran your ground from the outside down to the ground post? - on the outside of the chassis?

[Theo]

my wire goes to the internal ground. Do you mean you ran your ground from the outside down to the ground post? - on the outside of the chassis?

Thanks Pat and WyldRage.  I tested grounding the transformer screw by touching it with a wire and the other end to the ground post, which is connecting to IEC ground pin.  Also made sure that my RCA ground are floating.  No luck with reducing hum at all.  One thing I'm wondering is whether the ground post should float as well?  Now the post is touching the chassis.

[WyldRage]

my wire goes to the internal ground. Do you mean you ran your ground from the outside down to the ground post? - on the outside of the chassis?

Yes. I had already finished building my Cornet 2 and it was a simpler way to ground the transformer than going back in.

[WyldRage]

Thanks Pat and WyldRage.  I tested grounding the transformer screw by touching it with a wire and the other end to the ground post, which is connecting to IEC ground pin.  Also made sure that my RCA ground are floating.  No luck with reducing hum at all.  One thing I'm wondering is whether the ground post should float as well?  Now the post is touching the chassis.

Check where your Cornet 2 is plugged. If it's in a power strip, it may be possible that the strip itself is not connected to the earth (it would have 2 pins instead of 3 going into the wall socket). Are your interconnects shielded? If not there could be interference, as the signal from the TT is quite weak. Or there could be a magnetic field affecting your transformer, you could try moving the Cornet around a bit.

If that's still not it, than I am afraid I can't help you with my limited electrical knowledge.

[PatOMalley]

i was thinking of getting an isolation transformer for the cornet2 as well.
the go for bout $100

[Theo]

Check where your Cornet 2 is plugged. If it's in a power strip, it may be possible that the strip itself is not connected to the earth (it would have 2 pins instead of 3 going into the wall socket). Are your interconnects shielded? If not there could be interference, as the signal from the TT is quite weak. Or there could be a magnetic field affecting your transformer, you could try moving the Cornet around a bit.

If that's still not it, than I am afraid I can't help you with my limited electrical knowledge.

Thanks for all the suggestions.  I've tested my interconnects with my Bugle; has no hum at all, so it's not the cables.  I am down to experimenting with floating the ground post and repositioning my equipments.

[PatOMalley]

don' forget that you may have to live with hum.
and if so the best way to reduce it is to use 5751 tubes as they reduce gain.

[Theo]

don' forget that you may have to live with hum.
and if so the best way to reduce it is to use 5751 tubes as they reduce gain.

Cornet2 does sound a lot better than Bugle in my system but I wish for Bugle's lack of hum.

Tube rolling?  Haven't started on it yet.  I'm running JJ tubes for over a year.  Ordered a pair of Sovtek 12AX7LPS last month but have yet tried.