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Problem faced with Valhalla2 as pre with Audiolab 8200A as power amp - Help needed

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SachinChavan

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Friends, I am facing a problem which I believe you might be able to help me think through and solve.

I have a Schiit Valhalla 2 (tube headphone amp used as preamp) connected to my Audiolab 8200A integrated amplifier which drives my speakers (Castle Knight 2). I play CDs on my Cambridge CXC transport connected to Schiit Bifrost DAC which feeds into the Valhalla 2. I’ve confirmed from both the manual and Schiit Helpdesk that Valhalla 2 can be used as a preamp in the chain as above.

The Audiolab 8200A has a pre and power section inside and one can choose to use either or both through the selection knob. There are two ways therefore for me to connect the Valhalla 2 with the 8200A:

Option 1: Valhalla 2 as preamp feeding to the power amp section of 8200A - therefore bypassing the pre section of 8200A.

Option 2: Valhalla 2 A’s preamp feeding to pre of 8200A which in turn feeds to the power amp section of 8200A (I.e. using the 8200A in integrated amp mode after the Valhalla 2 as preamp). Note that this means I have two preamps in series before the power amp.

Now let me tell you that it is clear that the sound quality of option 1 is much better and the one I prefer/love. However, there’s a problem.

When I use this configuration in Option 1 (i.e. Valhalla2 feeding straight to 8200A power amp), the 8200A’s protection mechanism keeps cutting in. Now, this doesn’t happen immediately or with a predictable interval. It can sometimes happen almost once per twice a song, at other times I am able to play two or three CDs before this happens. But whenever this happens, the 8200A mutes itself for about 5-8 seconds and then comes on again playing the music further as if nothing happened.

So, currently I am compelled to use the configuration in option 2 above (Valhalla2 to 8200A preamp to 8200A power amp) in which I don’t face the above problem. However the sound in this mode has a pronounced holographic (record like) effect and sounds more like an arena performance in comparison with the intimate studio like performance sound that I love in option 1. The focus, transparency and microtones of sound in option 1 are so good that I clearly prefer it over the sound of option 2 for my listening.

I am at a loss to solve this problem (mentioned above) of the 8200A’s protection mechanism cutting in when I use the configuration in option 1. Can you think of why this may be happening? And why it doesn’t happen when I use the configuration in option 2? And how I could solve the problem and enjoy listening to my music as per option 1 without the above problem? I look forward to any thoughts, analysis, ideas and suggestions on the same.


Many thanks.
 
Last edited:

jls001

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What is your volume setting on Valhalla in Option 1? It's possible that you're over driving the 8200 in power amp mode to force it to go to protection mode.

Also, in Option 2, what are volume settings on Valhalla and 8200? Are you using both knobs, or putting one at full land controlling through only the second?
 

rikhav

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Exactly my thoughts as what @jls001 has posted
Check if you can adjust gain in schiit headphone amp or try to go for a schiit freya
 

SachinChavan

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What is your volume setting on Valhalla in Option 1? It's possible that you're over driving the 8200 in power amp mode to force it to go to protection mode.

Also, in Option 2, what are volume settings on Valhalla and 8200? Are you using both knobs, or putting one at full land controlling through only the second?


In option 1 (in which I face the problem), my volume level on the Valhalla 2 is just about at 9 o clock or so, I don’t enjoy too loud volumes personally and this is sufficient. In this option, the volume knob on the Audiolab 8200A is deactivated. I doubt if at 9 o clock I am over driving the 8200 power mode unless they are horrible mismatched (How to determine that?)

In option 2 (in which I don’t face the oroblem), I keep the the volume knob on Valhalla 2 around 11-12 o clock. And the 8200A is anywhere between the 9 o clock to 1 o clock position as I control the volume with it. I have also tried keeping the Valahalla2’s knob at different levels (even full), but I get the best range (on 8200 knob) in this setting. I haven’t faced the above said problem at any volume setting in Optiom 2.
 

yogibear

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You will need to replace the volume control in your tube pre to a higher value, to attenuate gain being fed in option 1.

No point using two preamps in the chain.
 

SachinChavan

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Exactly my thoughts as what @jls001 has posted
Check if you can adjust gain in schiit headphone amp or try to go for a schiit freya

I have toyed that (Freya) I’m my mind. But his can I be certain the same problem womt happen with the Freya as with the Valhalla 2 in the option 1? Anything that’s you can help me evaluate with the technical parameters (such as impedance)?

For information, I am posting snapshots of the specs on Valhalla 2 and Audiolab 8200A below.
 

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SachinChavan

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You will need to replace the volume control in your tube pre to a higher value, to attenuate gain being fed in option 1.

No point using two preamps in the chain.

Yogibear, any ideas on what exactly I can do to attenuate the gain? Is it possible to replace the volume control on the tube preamp? Where could I get the same?

Also, before I can attempt that, is there some calculation I can attempt to establish that the current gain Is the limiting factor?

Please note that in option the volume on Valhalla2 even at 9 o clock position is quite a lot. So why would the gain below?
 
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rikhav

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I am not an expert but specs say the power amp section has high gain so ideally it can be used with pre amp with no gain which is more of a impedance matching buffer

I use the same with my power amp
So as far I understand things using the freya should not give you such problem
Moreover it can he used with tube outputs, jfet and passive which will be with xeeo again
So you can use either of it unless you intend to use only the tube output
 

yogibear

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Plug off your tube pre and unscrew the panel to inspect if you can find any reading / specs on the volume contro pot.

Idea would be use higher value pot and that can be easily sourced.

Voltages inside should not be high as compared to tube amps.
 

SachinChavan

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I am not an expert but specs say the power amp section has high gain so ideally it can be used with pre amp with no gain which is more of a impedance matching buffer

I use the same with my power amp
So as far I understand things using the freya should not give you such problem
Moreover it can he used with tube outputs, jfet and passive which will be with xeeo again
So you can use either of it unless you intend to use only the tube output

Thanks Rikhav. If I go for Freya, I’d like to use it in the tube output mode. I quite like the sweetness and microtones improved by the tubes. By the way, which Power amp do you use with the Freya?

Another option for me to consider is to replace the Audiolab 8200a with a proper Tube amplifier that can take input from the Valhalla 2. But that would mean a significant cost and further experimentation with sound. I don’t want to go that route preferably as I am very happy with sound in option 1 today. Just that I need to solve this matching problem.
 

SachinChavan

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Ok, couple of more observations that can perhaps help you help me.

1. Under option 1, the protection cut off invariably happens immediately if I stop the music playback. What could it mean?

2. Once I face a cut off, it keeps repeating frequently.

Also, an interesting experiment I did right now. I kept the configuration under option 2 (with double preamp), but I kept the volume knob on the tube preamp (Valhalla2) to its max possible (5 o clock position). And the integrated amp (8200a) volume at very low level (just about 8 o clock) to compensate. I find that the sound is tad better and closer to the option 1 sound (which I prefer) than when both the Valhalla 2 and 8200 volumes are in the 11-1 o clock range. Perhaps this is because maximum amplification is now done by the tube preamp, leaving little for the integrated amp to do. AM I RIGHT I’m deducting this?
 
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rikhav

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Thanks Rikhav. If I go for Freya, I’d like to use it in the tube output mode. I quite like the sweetness and microtones improved by the tubes. By the way, which Power amp do you use with the Freya?

Another option for me to consider is to replace the Audiolab 8200a with a proper Tube amplifier that can take input from the Valhalla 2. But that would mean a significant cost and further experimentation with sound. I don’t want to go that route preferably as I am very happy with sound in option 1 today. Just that I need to solve this matching problem.

I feel if high gain from pre is issue then it won't change or chances it will be still a problem with any other tube or SS amp you buy
I just saw the product page of Valhalla 2 and on the back side there is a gain switch
Try to keep it on low gain and see if it helps

I don't have a schiit pre, I have a diy pre amp kit based on pass b1 design. It's a buffer and has no gain
 

yogibear

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Ever thought of just using a no gain tube buffer in place of tube pre ?

A headphone pre may have too much gain compared to a line in tube pre.

If you are happy with your SS pre, a Tube buffer can do the magic you are looking for.

Does your tube pre has SS gain stage too or is it pure tube gain stage ?
 

yogibear

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Beware about your experiment, it may cook your SS preamp in extended use and feeding of too much gain from tube pre.

Correct way should be the opposite of what you attempted.
 

SachinChavan

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Ever thought of just using a no gain tube buffer in place of tube pre ?

A headphone pre may have too much gain compared to a line in tube pre.

If you are happy with your SS pre, a Tube buffer can do the magic you are looking for.

Does your tube pre has SS gain stage too or is it pure tube gain stage ?

No, it has only a pure tube gain stage. And that’s what I am interested in. I am not interested in the SS pre sound. I WANT the tube sound! :)

I have tried connecting other preamp, this one from Primare (solid state) in similar configuration as Option 1, feeding to my 8200A’s power amp. And there’s no protection cut off problem with this. This proves that there’s nothing wrong with the 8200A’s power amp circuit. Therefore the problem has to be the matching between the Valhalla 2 preamp (may be because as you say it’s a headphone amp with too much gain).

I have tried putting the Valhalla 2 in low gain setting, but the cut off problem persists.

Do you think it may be leaking some voltage? Can that be a possible cause?
 
M

mpw

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Sachin

Put up a photo of your system.

And what's wrong with the integrated pre Amp ?

Regards
 

SachinChavan

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I feel if high gain from pre is issue then it won't change or chances it will be still a problem with any other tube or SS amp you buy
I just saw the product page of Valhalla 2 and on the back side there is a gain switch
Try to keep it on low gain and see if it helps

I don't have a schiit pre, I have a diy pre amp kit based on pass b1 design. It's a buffer and has no gain

Can you explain this tube buffer option to me? Do you use it along with a tube preamp? If not, where does the buffer come? After another preamp? Or directly after the DAC? And does the buffer output then go to the power amp? What’s your chain? Also, how’s the resulting sound? Is it enough tube like? And which DIY kit is it?

Thanks!
 

SachinChavan

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Sachin

Put up a photo of your system.

And what's wrong with the integrated pre Amp ?

Regards

There’s no problem as such with the preamp in the integrated amplifier. It’s just that it’s sound is too clinical and I don’t like it a bit. But when the tube preamp is connected to the power, it starts singing like a nightingale!

I have currently put another (SS) preamp for testing, and hence the tube preamp has been removed from the chain. I shall post a picture after I add it back.
 
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hifitoaster

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May be the gain provided by the pre is more than what the power can handle. Or a voltage leak.
 
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