[cgrums]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif I've just about given up suggesting this, seems like no one else has had this trouble. With me, it happened to every one of my 4 Milletts in some degree or other: check the tube sockets/tube pins. All it may take is a little tube wiggling to get the bias voltage to register. Connect your multimeter up so that you can watch the bias voltage on one of the tubes. Wiggle it and see if the voltage drops below your TREAD's supply voltage (by more than 1 or 2 volts). If so, then slightly bend the pin pairs together that correspond to the bias connection (pin 7? I can't remember). Try to bend them slightly out or to the sides in line with the pin circle. It depends on how the socket is loose. As I said, maybe it was just me, but almost every one of my sockets gave me fits (ceramic PCB). Moreover, if the one near the Pot is loose, the entire second tube won't conduct due to the single-ended design. Thankfully, a slight bending of the pins is all that it takes. Long-term, you might try popping the tops of the socket off and squeezing the socket tabs together slightly with a pair of pliers. If they're glued, you may be able to get an Xacto blade in there to separate the halves. BTW, you might try 27V with the TREAD - that's the standard most use. It was confirmed in Amb's tests, too, as the voltage that gave the best all-around results. That would be 13.5V on the bias for each tube.

Thanks! Gonna give this a shot tonight.

 

[cgrums]

I just tried a preliminary debug and found that if I tweaked the tube it would in fact drop the bias voltage. I then found that my socket had some pretty weak connections and in my tweaking I managed to work the whole socket loose. I'm going to fix this tonight and hopefully have something to listen to! Here's another question: the legs on the tube sockets don't seem to want to extend all the way through the holes on the board...they just sit on top of the holes. Is there anything I can do to get a more solid connection? I think this is especially important as I plan on rolling tubes in the future.

 

[tomb]

OK. I forgot you had those plastic sockets - they may be easier to fix if that's the problem. As someone else mentioned, too - you might check those solder joints on the legs. If the legs on those aren't whittled down so that they fit in those PCB holes tightly, or if the solder joint is less than ideal, you might have broken a connection. This could happen just from the normal flexing of plugging/unplugging the tubes.

 

[n_maher]

Cg,

I know this isn't going to be what you want to hear but if I was in your shoes I'd cut those wretched tube sockets off the board and get some new ones. I can't tell you the number of issues that I've had with those over the past two years.

I really prefer these sockets from Parts Connexion.

 

[jbloudg20]

Yeah from the moment I saw your pictures, I thought something would go wrong with those tube sockets.

 

[tomb]

I second Nate's suggestion. Those gold sockets are really nice. The Parts Connexion style of ceramic socket is superior in another respect, too. It's a very detailed difference, but the sockets separate into pretty much equal-thickness halves. Competing sockets at other retailers have a very thin bottom half, making it difficult to pry apart or drill out the center pin without breaking.

 

[cgrums]

Thanks for the info guys...I thought it might be the sockets. I'm going to try and get these to work while I wait for other sockets. I've had not the greatest luck in ordering from parts connexion as you have to download the form and email it, has anyone else had an issue? It was only one order for a handful of blackgates and other caps but I never heard anything about it and my card was never charged. Is there another vendor for the nicer sockets?

 

[dsavitsk]

Quote:

Originally Posted by cgrums /img/forum/go_quote.gif I've had not the greatest luck in ordering from parts connexion as you have to download the form and email it, has anyone else had an issue?

Their form is a pita. I don't even bother anymore -- just send them an email with what you want.

 

[n_maher]

If I'm ordering less than 20 items I call it in. More than that I use the form so they don't waste all day on the phone with me and increase the backlog of orders

. FWIW I sent in a 50 item order (lord, my wallet!) on Friday and it shipped yesterday. Pretty darn good for a boutique shop if you ask me. And Cg, I've got a spare set of those sockets incoming so if you don't want to place an order shoot me a PM.

 

[cgrums]

IT WORKS!!! Tidied up a few loose leads here and there and tweaked the finicky tube socket. Plugged it back in and lo and behold both bias voltages were reading just fine. At the same time. Sweet.

I've got the TREAD set at 27V and each bias voltage at 13.5V and this thing sounds amazing.

I've been listening to Tools 10,000 Days on my SR-60s and instantly noticed two things:

1. This amp does a phenomenal job of taming what I consider to be the borderline harsh highs the Grados exhibit from time to time and

2. This amp is overkill for these cans

Luckily I'm indulging myself with a christmas present of a pair of HD580s...very curious to hear how they pair with this amp.

Thanks again for all the help guys, this amp has resulted in a much more rewarding feeling of accomplishment having had to overcome a few more, albeit slight, hurdles along the way.

 

[cgrums]

Just a few final pictures in its temporarily non-enclosed state:

Now I just need to get back to work on the DB board

 

[jbloudg20]

Nice Job!

 

[nysulli]

looks good man, i think its finally time that i get to building mine now

edit: i see that you went with double stacked buffers, what happened to the DB's?

 

[cgrums]

Quote:

Originally Posted by nysulli /img/forum/go_quote.gif looks good man, i think its finally time that i get to building mine now edit: i see that you went with double stacked buffers, what happened to the DB's?

In progress...just got the last smd resistors I need and am waiting on a cheap multimeter from harbor freight to start matching the transistors.