[drewd]

Quote:

Originally Posted by shut85 i've gotten all the parts on the board except for the components like the power and inputs and outputs, i assume that s1 and s2 are for the switch but i only see a v_in pad and was wasnt sure how to connect the power exactly. wouldnt there be a v+ and a v- from the power to connect to the board, so where would the two go? also is there a certain way i have to orient the led on the pads next to d2la, like is there a + side and a - side?

S1 and S2 are for the switch.

V+ and GND are the inputs. The amplifier runs on a single voltage, so there is no V+ and V-, only V+ and ground. You do need to orient the LED correctly - there is a flat spot on the silk screen symbol. That marks the cathode, or the "negative" side of the LED. That would correspond to the flat side of the LED and also to the short leg.

-Drew

 

[JWFokker]

I may be the only one to forget this step, but if you're going to test the bias voltage, disconnect your headphones, because they make a loud screeching noise when testing the bias that may or may not be potentially damaging to them. At the very least, take them off your head, as it's quite loud.

 

[n_maher]

For the record, you should perform the bias adjustment before even plugging in your headphones, even worthless test phones.

 

[pabbi1]

And further for the record, 'bias' should be checked / adjusted with every tube change?

 

[mrdon]

Thanks to everyone for the instructions!

Well, I easily adjusted the bias to 12V on the Left Channel old school analog style.

However, the right Channel is still giving me problems.

After turning the screw clockwise and couterclockwise to the "click," the bias is stuck at 24V. Could it be a
1. Bad pot?
2. Bad soldering point?
3. Bad other?

 

[n_maher]

I wouln't say it's 100% necessary but if it were me I'd check it. It takes 2 seconds and could save future trouble. I've periodically checked my prototypes and the bias seems to stay pretty constant.

Also, just one thing of note, there are still a few folks that haven't paid me for the round two shipping bills

. At least one contact me to let me know that they'd be on vacation so that's fine, the others, don't make me come find you...

Nate

 

[pabbi1]

Does the bias change between tube types, say 12ae6a to 12fk6, or are all the most likely tubes fairly similarly spec'd regarding voltage / output?

I'm setting up with the former, but will definitely also check the latter...

And, what are the noticeable burn in breaks? 100 - 200 hours? Anyone guess what the prime useable life of these tubes?

Last, I am using some BG on C7 (if ya got 'em, smoke 'em), so I know I have some extra burn time...

 

[drewd]

Quote:

Originally Posted by pabbi1 Does the bias change between tube types, say 12ae6a to 12fk6, or are all the most likely tubes fairly similarly spec'd regarding voltage / output? I'm setting up with the former, but will definitely also check the latter... And, what are the noticeable burn in breaks? 100 - 200 hours? Anyone guess what the prime useable life of these tubes? Last, I am using some BG on C7 (if ya got 'em, smoke 'em), so I know I have some extra burn time...

I didn't adjust the bias between the 12AE6As or the 12FK6s. The 12FK6s will tolerate higher bias than the 12AE6As. I don't recall off the top of my head at which point the 12AE6As start getting nasty, but it's fairly high. The 12FK6's will go up to something like 22 volts, although there's really no reason to do that.

The tubes are rated at 10,000 hours in the data sheet. They're all NOS, of course, so it probably wouldn't be appropriate to expect that kind of life from them, but I'll bet that they'll last somewhere just short of forever.

Break in? What I've noticed with mine (sans Black Gates, of course

) is that after about 50 hours, the highs started to get a little recessed, just slightly attenuated. At maybe 120 hours, they came back and what I thought was a pretty bloomy midrange eased back a little - from a somewhat overenhanced presence to something still very much there, but in a much more pleasant way - just what I would expect to hear from a tube amp. The bass never changed. It's always been extremely well defined and accurate.

Virtually all of my listening has been with 12FK6s and Beyer DT880s. I've done a tiny bit with Grado SR225s (which match up to this amp extremely well) and none with my HD580s. Well, not none - about two minutes. It just wasn't a good fit with this amplifier at all. I didn't care for the sound of the 12AE6As. I'm not sure if that says anything about my listening taste or hearing...

I suspect that your experience is going to be different - pesky BG burn in (and re-burn in). By the way, I leave my amp on 24/7. Dunno how much of a difference that makes. It's at work, so I figure if my computer and workstation can run 24 hours a day, one l'il ol' headphone amp won't make much of a difference.

Also, you can read Erikzen's post in the Amps forum about the amp that he had for the NYC show. It's got hundreds of hours on it, so what he hears is what there is - it's definitely broken in. It's a prototype board, but all the same parts as the group buy boards.

-Drew

 

[pabbi1]

Yeah, I plan to burn for at least a week before bothering to get too concerned with any impressions - starting tonight.

I'll post some pics as well... and wish you hadn't said that about the 580s, though I'm sure my 600s and the soon to be acquired 650s will sound much better, even before I start the woodie experiments..

 

[drewd]

Quote:

Originally Posted by pabbi1 I'll post some pics as well... and wish you hadn't said that about the 580s, though I'm sure my 600s and the soon to be acquired 650s will sound much better, even before I start the woodie experiments..

Count on it - there's no comparison!

-Drew

 

[dviswa]

Quote:

Originally Posted by n_maher I wouln't say it's 100% necessary but if it were me I'd check it. It takes 2 seconds and could save future trouble. I've periodically checked my prototypes and the bias seems to stay pretty constant.

Unlike your experience, I seem to have a good bit of movement in the bias levels in my amp. When I first powered it up, I had adjusted it to around 12, a day later it had drifted to 19. Even if you discount that first drift to bad initial adjustment, I found that on day 3 it had moved about 0.5 v. All this time the power supply (STEPS) has been pretty steady around 24.5V

 

[rreynol]

Quote:

Originally Posted by dviswa Unlike your experience, I seem to have a good bit of movement in the bias levels in my amp. When I first powered it up, I had adjusted it to around 12, a day later it had drifted to 19. Even if you discount that first drift to bad initial adjustment, I found that on day 3 it had moved about 0.5 v. All this time the power supply (STEPS) has been pretty steady around 24.5V

Based on this post, I went and checked the bias on mine. It was set up at 13.5V bias last Friday. Tonight, 22V on one channel and 17 on another. bleh.

 

[pabbi1]

Ok, I've got a couple of 'Money Shots"...

Amp case
Amp open case
Amp board 1
Amp board 2


Unfortunately, I'm getting 0 bias... on either channel. The LED doesn't power up. I have 27.5v coming out of the STEPS, and have 27.5v coming in (properly) - any ideas? What additional test point(s) can I check to narrow this down?

Of all the things I never expected... I guess this is one way to make sure no caps melt down.

 

[drewd]

Quote:

Originally Posted by pabbi1 Unfortunately, I'm getting 0 bias... on either channel. The LED doesn't power up. I have 27.5v coming out of the STEPS, and have 27.5v coming in (properly) - any ideas? What additional test point(s) can I check to narrow this down? Of all the things I never expected... I guess this is one way to make sure no caps melt down.

You'll want to hook a switch up to S1 and S2 or else jumper across the two pads.

-Drew

 

[pabbi1]

DOH! Yep, makes sense... and I thought using a switched IEC got me away from all that.

Always the simple things...