[Paladin79]

I'm actually talking about the ground that comes in with the inputs. I've always seen it soldered onto the pot's ground pins, but I've got my ground pins connected to each other and then via the green wires in my pic to the ground bus. Could I just bypass the pot entirely and ground the inputs at the ground bus where it attaches to the headphone jack ground?

I would say yes, see they are going to the same point anyway I would think.

 

[bcowen]

Great meters and they have a built in continuity tester. That is a quick and easy way to test for proper ground connections. I used it to troubleshoot something for @bcowen, the underside of some chassis are painted and manufacturers sometimes rely on washers like this to cut through the paint and make proper contact.



It is much better to scrape the paint away to insure better contact. It is also a great way to test for issues with headphone cables and the like. The tester gives off an audible beep when you have continuity. It can also tell you quickly if you have a short circuit or open circuit.

Glad you brought this up. In @DeweyCH 's continued hum war, two things I see.

1) Remove the IEC socket's ground lug screw from the chassis and scrape away the powder coat paint there and then re-attach. The paint was not scraped off at the factory, and the only (good) earth ground connection is whatever paint might have sheared off the screw threads when they put it in. Pretty much the same grounding issue you described above with the Cary preamp, just at a different point in the DV. My DV had a slight hum when I first got it (it was only slight, so I guess I was one of the lucky ones), but once I'd scraped the paint and provided a much cleaner ground path that hum went away.

Mine after scraping:

2) @DeweyCH needs to get rid of the herculean bus bar heater rods and get some twisted pair wiring in there. That's an AC signal, and those wires should be twisted for best noise rejection. Below is @L0rdGwyn 's photo of how the heater wiring (green wire) should be done. That should solve a good bit of hum issues in and of itself.

 

[Paladin79]

Glad you brought this up. In @DeweyCH 's continued hum war, two things I see.

1) Remove the IEC socket's ground lug screw from the chassis and scrape away the powder coat paint there and then re-attach. The paint was not scraped off at the factory, and the only (good) earth ground connection is whatever paint might have sheared off the screw threads when they put it in. Pretty much the same grounding issue you described above with the Cary preamp, just at a different point in the DV. My DV had a slight hum when I first got it (it was only slight, so I guess I was one of the lucky ones), but once I'd scraped the paint and provided a much cleaner ground path that hum went away.

Mine after scraping:


2) @DeweyCH needs to get rid of the herculean bus bar heater rods and get some twisted pair wiring in there. That's an AC signal, and those wires should be twisted for best noise rejection. Below is @L0rdGwyn 's photo of how the heater wiring (green wire) should be done. That should solve a good bit of hum issues in and of itself.

Two good points. I cringed when I looked inside mine and saw those filament lines lol. I have been thinking through a cabinet extension for some Cowen guy and have spent little time dismantling mine. Oh and I have a preference for soldering to the IEC lugs.

The ground screw from the IEC was not very tight in mine, threads were stripped and it appeared to have a coating of rosin on the top of the lug, I will scrape away the paint change to a better screw and do this right.

 

[DeweyCH]

Glad you brought this up. In @DeweyCH 's continued hum war, two things I see.

1) Remove the IEC socket's ground lug screw from the chassis and scrape away the powder coat paint there and then re-attach. The paint was not scraped off at the factory, and the only (good) earth ground connection is whatever paint might have sheared off the screw threads when they put it in. Pretty much the same grounding issue you described above with the Cary preamp, just at a different point in the DV. My DV had a slight hum when I first got it (it was only slight, so I guess I was one of the lucky ones), but once I'd scraped the paint and provided a much cleaner ground path that hum went away.

Mine after scraping:


2) @DeweyCH needs to get rid of the herculean bus bar heater rods and get some twisted pair wiring in there. That's an AC signal, and those wires should be twisted for best noise rejection. Below is @L0rdGwyn 's photo of how the heater wiring (green wire) should be done. That should solve a good bit of hum issues in and of itself.

So, I was somewhat under the impression that the heater bars were tungsten and special. Is that just regular copper wire?

 

[Paladin79]

So, I was somewhat under the impression that the heater bars were tungsten and special. Is that just regular copper wire?

Read about twisted pair sometime, I prefer bonded twisted pair. The material has little to do with noise rejection.

 

[DeweyCH]

Read about twisted pair sometime, I prefer bonded twisted pair. The material has little to do with noise rejection.

I'll read up on them. Can I use twisted solid-core copper wires to replace the heater rods then?

 

[bcowen]

I'll read up on them. Can I use twisted solid-core copper wires to replace the heater rods then?

Absolutely. 20 gauge is sufficient. A heavier gauge is fine too, but I wouldn't go smaller than 20 gauge. The important thing is the twisting. I seriously doubt those are tungsten rods or wires or whatever in the stock DV. They are just a heavy gauge wire that's probably no different than any of the other wiring in there.

 

[bcowen]

Two good points. I cringed when I looked inside mine and saw those filament lines lol. I have been thinking through a cabinet extension for some Cowen guy and have spent little time dismantling mine.

Thinking about? You mean I shouldn't continue waiting by the mailbox right now?

 

[DeweyCH]

Absolutely. 20 gauge is sufficient. A heavier gauge is fine too, but I wouldn't go smaller than 20 gauge. The important thing is the twisting. I seriously doubt those are tungsten rods or wires or whatever in the stock DV. They are just a heavy gauge wire that's probably no different than any of the other wiring in there.

Good to know! I’ve got some 18 gauge solid core wire arriving this afternoon I’ll use

 

[Paladin79]

Thinking about? You mean I shouldn't continue waiting by the mailbox right now?

Oh yeah, do you plan to keep the bottom plate on your amp? If not I will need to notch the front and back a bit so to avoid a gap.

 

[bcowen]

Good to know! I’ve got some 18 gauge solid core wire arriving this afternoon I’ll use

That will work nicely.

 

[bcowen]

Oh yeah, do you plan to keep the bottom plate on your amp? If not I will need to notch the front and back a bit so to avoid a gap.

No, the stock bottom plate will be disappeared. The extension will allow me to parallel a pair of 47uf Mundorfs (per channel) for the coupling caps, but will stick out below the bottom plane of the chassis by about an inch.

 

[Paladin79]

No, the stock bottom plate will be disappeared. The extension will allow me to parallel a pair of 47uf Mundorfs (per channel) for the coupling caps, but will stick out below the bottom plane of the chassis by about an inch.

Ok I will go to the extra trouble, if I have to, I guess.

 

[qingcai]

If someone could give me the dimensions of the top plate and front plate I can do some preliminary work on a cabinet build. It looks like @bcowen will use his front plate so it is easy enough to do a drop in design for his. In the event I give mine away I could do something similar. If I were to keep it I would use dual volume pots and these little guys would not fit the normal front plate. They are 1.5 inches square and .75 inches deep. If I keep it I would have to do copper plate along the lines of something I made for a buddy in Maryland. Such a plate would accommodate the Alps pots as well as VU meters. The electronics is the easy part, the cabinet build is the fun part for me at least.











.

top 10 3/4 x 6 "
front 2 1/8 x 5 7/8 "

 

[DeweyCH]

Coolio. Took the heater bars out, and man, changing to this different tip has made a ton of difference. Solder wick? Sucking solder out like nothing. I'm going back and cleaning up all the spots that look nasty, and I'll put in the twisty wires this evening. After shoring up a few connections the hum was gone (but right channel was out). It'll be done soon, I think.