[hodgjy]

Thanks for your input.  It has to be the case, but in my other OTL amp, the 6992 tubes seem matched, but there is a night and day difference in the Valhalla.  Weird.
Quote:

Yes! And I think this is the case with any OTL tube amp. I had the same thing and reversed the power tubes to offset the different levels. I guess if the amp used one tube(or 10 tubes)it would be less off an issue.

 

[schaaf]

Well, the delivery notification came in so I raced home to plug the Valhalla in and get some impressions. 
 
It's making a huge difference already. 
 
Lossless/various mix of 320kbps > iMac > crappy cables > Valhalla > HD650
 
The soundstage actually seems to have decreased slightly. The separation is still there and great. The impact is the biggest thing. Drums sound like drums, not muffled bangs. Cymbals are crisp. The bass is finally there. It's enough for me. Vocals are sweet and sound exactly like I want them to. The highs seem a little shrill at this point, but again this is only after about 25 min of run time. I'll let the amp burn in for a while and come back to see what (if anything) has happened. 
 
Question that may be dumb:
Do the headphones actually have to be plugged in to the amp while it burns in or can the amp just run some music at the listening volume without actually playing through anything?
 
So far it's pretty sweet. I wish the tubes would glow more, but I think I was expecting them to be brighter than they actually are!
 
 
S-

 

[hodgjy]

You will always want to have a load on the tubes, so best to keep headphones plugged in.  But, don't just burn it in while not listening.  Listen while it burns in.  Changes are subtle at most.
Quote:

Question that may be dumb:
Do the headphones actually have to be plugged in to the amp while it burns in or can the amp just run some music at the listening volume without actually playing through anything?

 

[Mr.Tom]

Quote:

The highs seem a little shrill at this point, but again this is only after about 25 min of run time. S-

 
Mine came to life and started to bloom on the third day.

 

[schaaf]

Alright - what's the accepted or safe practice for plugging headphones in / turning on the amp. 
 
I thought I did it correctly last night. Source was off. Turned amp on with the volume knob all the way down. Let it warm up for about 1 min, plugged 650's in *POP* *CRACKLE*    Schiit! What? I listened to them for a while, and while they don't appear to be damaged, I'm a little worried about it. I wasn't wearing them when I plugged them in, but I could hear it from where they were sitting. It was LOUD. 
 
So, what did I do wrong?  

 

[hodgjy]

I don't think you did anything wrong.  It was probably one of the tubes settling in.  Tubes have been known to pop and ping while they warm up.  Usually, it's not too loud through the headphones, but sometimes it can be.
 
However, it's usually best to turn on source, plug in headphones, then turn on tube amp.  But, what you did should not have caused any problems.
 
Quote:

Alright - what's the accepted or safe practice for plugging headphones in / turning on the amp. 
 
I thought I did it correctly last night. Source was off. Turned amp on with the volume knob all the way down. Let it warm up for about 1 min, plugged 650's in *POP* *CRACKLE*    Schiit! What? I listened to them for a while, and while they don't appear to be damaged, I'm a little worried about it. I wasn't wearing them when I plugged them in, but I could hear it from where they were sitting. It was LOUD. 
 
So, what did I do wrong?  

 

[hodgjy]

Unfortunately, all is not well in my Valhalla land.  I seem to have a persistent channel imbalance.  I've tried four sets of matched pre-amp tubes, and they all show a pretty noticeable imbalance.  Sometimes the imbalance follows the tubes, sometimes it does not.  It is absolutely mind blowing.  If the Valhalla is this sensitive to even the most minor tube differences, this is really going to mess with my head.
 
I have been emailing Jason, and he said the only active devices in the amp are the tubes. 
 
Sadly, I'm going to be asking for an RMA.

 

[paradoxper]

Quote:

I don't think you did anything wrong.  It was probably one of the tubes settling in.  Tubes have been known to pop and ping while they warm up.  Usually, it's not too loud through the headphones, but sometimes it can be.
 
However, it's usually best to turn on source, plug in headphones, then turn on tube amp.  But, what you did should not have caused any problems.
 

That's pretty wrong. You need to turn the Lyr/Valhalla/Asgard (if you ever turn it off) on and wait 20 seconds for the relay, then plug your headphones in.

 

[hodgjy]

Solid state and hybrid amps it is often recommended to turn on and then plug the headphones in, but for pure tube amps (OTL and transformer-coupled amps), it's very bad to run the amps without a load, and this includes during power on and power off.
 
The Valhalla has no relay.  You are wrong.  The Asgard and Lyr have the relay.  Plus, the whole point of the relay is to protect your headphones in the first place, thus negating the need to power on and the plug in.
 
Quote:

That's pretty wrong. You need to turn the Lyr/Valhalla/Asgard (if you ever turn it off) on and wait 20 seconds for the relay, then plug your headphones in.

 

[paradoxper]

Quote:

Solid state and hybrid amps it is often recommended to turn on and then plug the headphones in, but for pure tube amps (OTL and transformer-coupled amps), it's very bad to run the amps without a load, and this includes during power on and power off.
 
The Valhalla has no relay.  You are wrong.  The Asgard and Lyr have the relay.  Plus, the whole point of the relay is to protect your headphones in the first place, thus negating the need to power on and the plug in.
 

Yep, that's specifically what I was focusing on. And you're right, I stand corrected. OTL's are fine, in fact, you probably shouldn't unplug the
headphones while amp is on. 

 

[karlsonklam]

does the Asgard's relay work fast enough to deal with mains power glitches which can occur during storms?  Where I live the power can go off then come back on several times before the grid crashes.   A good relay system should never let a damaging transient occur.  What's the story on the Asgard's turnon-off behavior?  did early models include a relay?  What is the lowest safe impedance the Asgard "likes"?

 

[grokit]

Always use a surge protector

 

[karlsonklam]

fwiw I don't believe a surge protector would affect the inherent time characteristics of a charging/discharging supply.  Some power supplies such as the simple RC unregulated
Van Alstine mod of Dynaco's PAS tube preamp could be switched on and off when hooked to a solid state amp without hurting the speakers or amp.   I will consider a Zerosurge or Brickwall unit.
 

 

[eddiek997]

Quote:

Always use a surge protector

Preferably use a power conditioner. Super preferred is one with built in battery backup.

 

[grokit]

I have a whole-house surge protector right at the breaker box, then power line conditioners/UPSs where appropriate.