Speedball started!

[hasafraker]

the wait is almost over! I broke out into a cold sweat when I saw the little package from Bottlehead sitting on my desk when I got home Thursday night... I am actually caught up on my homework and other random shenanigans and my wife told me I could continue working on it if I wanted to.

I just got done stuffing the boards for the upgrade, so I'm ready for part two. oh yeah... my OCD wouldn't allow me to put the LED's stripe-side up on the boards, I just couldn't do it, every time I saw the amp I would know they were backwards and it would drive me insane till I turned them the other way, so I marked them with a sharpie, tripple checked their orientation and put them in nipple side up.

gonna let the dogs out and then I'm going back down to my bench to start on the second part, and with luck I'll get to listen to my upgraded crack this evening!

[hasafraker]

wow...

Doc... thanks for such an awesome kit. aside from the improvements, sweet christmas this thing sounds insane. Doubt you remember initially that some of my voltages were a bit low, outside the "standard" tolerance but it still sounded great so I wasn't worried, now... my voltage checks were VERY close, even the ones that were outside the 10% deviance are within 5%, most are within 2%.

talk about a black background... wow it's just emptiness, during quiet passages unless it's in the recording, there is just nothing there, awesome. I think the sound stage has improved as well, have a better sense of space now. Bass is for lack of a better word, perfect. Natural, tighter, more controlled. I'm thrilled with the results!

a few shots just for fun
http://www.flickr.com/photos/28861421@N02/

[hasafraker]

I have a question,

I picked up a (what appears to be) nice Amperex 6as7g and put it in this afternoon, I was intending to burn it in for a week and see what I thought. Initial impressions were good but I sat down tonight to listen some more and discovered no sound coming from the amp.   there was a moment there where I was very sad that my Crack had failed in some way. Closer inspection revealed that the Pinacle Audio 12au7 appeared to be dead. Very odd... I ran that tube in for a couple days initially when I got it. I swapped it out for a CONN 12au7 that I picked up for pennies from a guy who refurbished a couple organs. I pulled the new Amperex 6as7 and put the original 6080 included in my kit and fired it back up. All LED's in the speedball lit up just like Christmas, I plugged everything back in and I have music. No noise, or odd sounds beyond the tubes warming up.

Anyone have ideas what might have killed the Pinacle 12au7? This was supposedly a new tube, it had at least 50 hours on it before putting it back in today. I am going to take the amp down to my bench tomorrow and check voltages again, after the speedball upgrade all my voltages checked out and if anything were closer to spec than before. Assuming that voltages check out should I just chalk it up to a faulty tube?

[Grainger49]

Do your voltage checks with Conn 12AU7.  Remember, that the voltages can be off by 15% and be good.  If they are right your problem was the Pinacle tube. 

If the voltage is right with the Conn, then all is right with the Crack.  The resistors are right, the power supply is right and with a good tube the voltages are where they should be then there is nothing wrong with your Bottlehead equipment.  That only leaves a tube that was going to die young whenever it got used.  It just waited years to get used for the first 50 hours.  There are tubed equipment manufacturers who burn in new equipment for 100-200 hours before shipping to weed out infantile failures.

[hasafraker]

Grainger,

thanks for the feedback, it seems my readings are a little hotter than they were before, some are a bit higher than 10%, I think I'll check it with a couple different tubes just to see if there is much variance. I'd been running a 7802 for the last week or so. At this point I guess I'll chock it up to a defective tube.

voltage checks were as follows with the 6080 included in the kit and the CONN 12au7

contacts 1-20
88
179
0
179
86.5
0
118
0
115
0
0
0
179
0
198
0
0
0
217

A1-A9
86
0
1.52
0
0
88.7
0
1.53

B1-B8
88.8
178
118
86
179
115
0
0

[hasafraker]

ok interesting development...

I pulled the sylvania and put the new amperex 6as7 back in there and I think I've got the problem, it's the amperex. The LED's on the big speedball board don't light up with the 6as7 in there, if I switch back to the other 6080 we get lights. The Pinacle has short plates and the heaters are not very bright, so that tube will go back in for a recheck.

voltages from the new 6as7g yeah it's hosed;
66
189
2.1
57
189
2.3
0
0

[hasafraker]

hah the Pinacle 12au7 is fried too... awesome! At least I didn't have one of my nice ones in there, granted the Pinacle sounded fine while it worked but I'd much rather sacrifice that one over any of the nicer ones I have. Not a good day for tubes at my house

[Grainger49]

With your voltages changing with each tube, and it seems you have one or two bad tubes, it is hard to say what area is causing the problem. 

From your readings in Reply #4, terminal 1 (T1) is jumpered with B1 (which shows the right voltage) but T1 reads 2V less, you might touch up both solder joints on that wire.  T5 is jumpered with B4 (which shows the right voltage) but T5 is 3.5V low, again touch up both ends of the wire.

The readings on T7 and T9 are higher than expected.  Verify that the resistors between T1& T2 and T4 & T5 are 22.1k ohm resistors (Page 25).  Also, if they are right then the triode you are using is at fault.  This both is the plate load of the driver and sets a grid voltage and is the input on the 6080.