I swear baby, this has never happened before (please help me, Crack won't work)

[jrebman]

Dr. Tubes,

The Cambridge is indeed a very harsh sounding dac.  I had one on loan here for a bit and couldn't stand to listen to it.

Check out the HRT MusicStreamer II and II+ dacs for $150 and $350 respectively.  I have the original MusicStreamer+ that I paid $200 for, and it's incredibly good for the money.

The II version has some upgraded parts, an improved design, async usb connectivity, and handles up to 24/96 sample rates.

If your budget allows, and like me, you prefer the sound of a NOS dac, the db Audio Labs Tranquility dac at $1500 is the best 16/44.1 khz dac I've ever heard, including a lot in the $10k price range.  It is a superb dac that sounds so close to vinyl it's scary, but also with the best that digital has to offer.

Of course we're all waiting for the BH dac, but until then...

HTH,

Jim

 

[Paul Joppa]

Some folks are sensitive to inverted absolute polarity and some are not.  Second verse, some albums preserve absolute polarity and some do not.  ...

Third verse, some albums preserve phase on some songs, invert it on other songs.

Fourth verse, some albums preserve phase on some instruments (i.e. some recording tracks) and invert it on others. You want that trumpet in phase, or the guitar?

 

[Grainger49]

Yup, those are albums that drive me crazy.  And maybe that's why I'm so crazy.  I hear it and want music to be "right."

I have found that Rounder is good at recording and mastering a believable soundstage and preserving the absolute phase together.  Sometimes positive, sometimes negative, but the whole album and all the instruments preserved the same.

So I have a lot of Alison Krasuss, Jerry Douglas, Etc.

 

[Todd R]

Well darn it, the Crack is not working again!
I stained the base, brought it back into the house and hooked it up, but the fuse blew. Thought maybe I accidentally had the switch on when I plugged it in, so I tried another fuse & it blew too.
The AC socket did feel a little funny and made a clicking sound if I rocked the cable, but other than that I can't see anything wrong anywhere.

 

[Doc B]

Plugging the power cord with the power switch on probably won't hurt the fuse. I would look first for some errant, untrimmed lead that might have been moved to where it is touching something it shouldn't, and also check to see if maybe something metal in either the IEC socket socket or power switch got loose from the plastic deforming a bit under soldering.

 

[Grainger49]

Since it worked you can be certain that it was wired correctly.  Because it stopped working you should look through the power supply.  Blowing the fuse really indicates some kind of short.  If it were on the IEC socket it would trip your breaker on the circuit feeding it.  But the clicking sound in the IEC socket is odd.

 

[Todd R]

Guys,
I just don't know.
I've been looking at it under the magnifying glass, blowing it all out with compressed air, tapping & shaking to see if any loose bits fall out.
Nothing....
Is it possible that a bad tube could cause this? Maybe shorted heaters?

 

[Dr. Toobz]

FWIW, I also blew a fuse shortly after getting things up and running. I had also made the manual's mistake of wiring the first resistor off terminal 22U (ground) instead of after the first capacitor in the filter network for the B+ (21U). The amp played fine for an hour; then, I turned it off. When I turned it on again, nothing happened. The fuse had blown. After checking everything and not finding any shorts or errors, I put in a new fuse and have used the amp for at least 10 hours now without a single problem.

 

[Todd R]

weird....
But, just had a thought.
What size fuse should we be using? I've got a 500ma in there as per the manual.

 

[Doc B]

You guys might want to measure the resistance value of that first 270 ohm resistor to make sure it didn't drift when it was connected wrong. I would think it would hold up OK, but it's easy to check. The two different fuse problems could be from different causes, e.g, the fuse blowing when the amp isn't even turned on indicates a problem in the IEC socket or power switch wiring, while a fuse that blows after an hour usually indicates that it was previously stressed and just finally let go.

 

[Todd R]

You guys might want to measure the resistance value of that first 270 ohm resistor to make sure it didn't drift when it was connected wrong. I would think it would hold up OK, but it's easy to check. The two different fuse problems could be from different causes, e.g, the fuse blowing when the amp isn't even turned on indicates a problem in the IEC socket or power switch wiring, while a fuse that blows after an hour usually indicates that it was previously stressed and just finally let go.

FYI, I checked and it did not blow when plugged in but amp left off, so it's not an IEC problem.

Resistor checks fine at 270 ohms.

 

[Doc B]

It's possible that the 1/2A Slo Blo fuse could be marginal. If all the resistance checks are still good you could maybe try a 1A. I've seen the situation happen in the past where we spec the smallest fuse that holds OK on the prototypes, and then end up going up one size because we see the occasional failure in the field during the startup current surge. It could be that there are variations in how much and how fast various tube heaters pull current when they start up.

 

[Dr. Toobz]

You guys might want to measure the resistance value of that first 270 ohm resistor to make sure it didn't drift when it was connected wrong. I would think it would hold up OK, but it's easy to check. The two different fuse problems could be from different causes, e.g, the fuse blowing when the amp isn't even turned on indicates a problem in the IEC socket or power switch wiring, while a fuse that blows after an hour usually indicates that it was previously stressed and just finally let go.

Doc,

I get a reading of ~320 ohms on that resistor as opposed to 270. My meter is really old and cheap, so it's possible that could be part of it, but usually, the resistances are within 5%. That would be 18.5% off. Are these 20% tolerance or something?

I visually checked my new 500mA fuse, and it looks like new. So I think that the last one indeed became stressed and just "let go." The local Rat Shack has a bag of .5A ceramic fuses for something like $1.99, so this was easily fixed.

EDIT: Just to clarify, I cannibalized the .5A glass fuse that came with my Seduction for the Crack, and replaced that with a ceramic fuse in the Seduction. Can't really "visually inspect" a ceramic fuse.....

 

[Todd R]

It's possible that the 1/2A Slo Blo fuse could be marginal. If all the resistance checks are still good you could maybe try a 1A. I've seen the situation happen in the past where we spec the smallest fuse that holds OK on the prototypes, and then end up going up one size because we see the occasional failure in the field during the startup current surge. It could be that there are variations in how much and how fast various tube heaters pull current when they start up.

Slo Blo? The one it came with & the ones I've been blowing are fast blow. Ok, will go up to 1A if I can't find 1/2 amp slo and let you know here in a couple min.

 

[Todd R]

Alright, found a 1.6A fuse in my arsenal and gave it a try.
The amp is on now. I'm going to leave it running with an iPod on repeat while I work on my kitchen floor project and check it periodically.
What would be the maximum fuse size that would be safe to put in this amp?
Thanks,
TR

 

[Doc B]

I would first try a 1/2 A slo blo (I thought that was what we had in stock here) and if that doesn't hold try a 1A slo blo. We can mail some to you if you like.

 

[Todd R]

I would first try a 1/2 A slo blo (I thought that was what we had in stock here) and if that doesn't hold try a 1A slo blo. We can mail some to you if you like.

That would be cool if you could since I've already made 2 trips to the "shack" today.

 

[Todd R]

Got the fuses, thanks.
TR