Problem faced with Valhalla2 as pre with Audiolab 8200A as power amp - Help needed
D
Deleted member 15865
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D
Deleted member 15865
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Agree that I need to place them separately. But this isn’t the reason for the problem I am seeking solution to. As posted in a comment earlier, I tried with another (SS) preamp and the problem doesn’t exist. So this isn’t due to lack of ventilation. Also the two components don’t run even warm.
rikhav
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Absolutely agree that it's not the issue now but just suggesting for the equipment in the long run
29 dB gain on the power amp section of the Audiolab, plus 9 dB gain from the preamp section of Audiolab.
Your power amp section will work with an unity gain buffer too as 28-29 dB is a very standard power amp gain.
Also, I noticed that the preamp section of the Audiolab is capable of pumping out about 7V. This is a lot of voltage so I don't see a reason why the voltage from your tube preamp would over drive your power amp section as the Audiolab power amp section is designed to handle as much as 7V from its preamp section.
Also the Audiolab preamp section has an output impedance of 100 Ohms which is fairly standard for a preamp. Using the usual formula of having input impedance of 10X the output impedance of the source, your power amp section must have input impedance of at least 10 x 100 Ohms, but in practice I'm guessing it will be much higher than just 1 kOhms. 47KOhms used to be a fairly standard input impedance value in older amps. In any case, the power amp section won't be a mismatch for the 14 Ohm output of your tube headphone amp.
If gain is too much (as you suspected), you will get distortion.
If impedance is mismatched, you'll not hear optimal sound.
But neither is a catastrophic condition that will shut down the power amp.
You need to look elsewhere for the problem. Someone suggested voltage leak.
Your power amp section will work with an unity gain buffer too as 28-29 dB is a very standard power amp gain.
Also, I noticed that the preamp section of the Audiolab is capable of pumping out about 7V. This is a lot of voltage so I don't see a reason why the voltage from your tube preamp would over drive your power amp section as the Audiolab power amp section is designed to handle as much as 7V from its preamp section.
Also the Audiolab preamp section has an output impedance of 100 Ohms which is fairly standard for a preamp. Using the usual formula of having input impedance of 10X the output impedance of the source, your power amp section must have input impedance of at least 10 x 100 Ohms, but in practice I'm guessing it will be much higher than just 1 kOhms. 47KOhms used to be a fairly standard input impedance value in older amps. In any case, the power amp section won't be a mismatch for the 14 Ohm output of your tube headphone amp.
If gain is too much (as you suspected), you will get distortion.
If impedance is mismatched, you'll not hear optimal sound.
But neither is a catastrophic condition that will shut down the power amp.
You need to look elsewhere for the problem. Someone suggested voltage leak.
D
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No, it was a two pin power cord that came with the Valhalla 2. But now tha you mentioned it, I tried changing over to a three pin power chord. But sad to report that the protection cut off problem still persists.
Does that indicate that DC voltage leakage may not be a problem?
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M
mpw
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Why don't u write to audiolab ?
D
Deleted member 15865
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Also, I notice that the Valhalla 2 does not have an output relay. Does that mean it will pass on any DC leak to the power amp? In that case, what solutions do I have to take care of the problem if it’s happening?
I checked the Valhalla2 on the Schiit site.
It is essentially designed for headphones of all grade or to drive dedicated headphone amps.
Though it says you can use with active speakers, this pre has design constrains in driving power amps due to its low output sensitivity. It will definitely harm your audiolab power if you continue using it.
Look at a dedicated preamp
It is essentially designed for headphones of all grade or to drive dedicated headphone amps.
Though it says you can use with active speakers, this pre has design constrains in driving power amps due to its low output sensitivity. It will definitely harm your audiolab power if you continue using it.
Look at a dedicated preamp
M
mpw
Guest
Put back the Valhalla for headphone duties only.
look for a dedicated pre for the audiolab.
( maybe a preamp for a head amp and preamp for stereo amp can have different design implications - i am speculating )
a good place to start will be Lyrita Audio Delhi.
regards
M
mpw
Guest
yogibear,
a request - dont ask anyone to measure or use any DiY / testing instrument - till you are sure that the person can do it.
Just out of concern for safety.
regards
a request - dont ask anyone to measure or use any DiY / testing instrument - till you are sure that the person can do it.
Just out of concern for safety.
regards
dheerajin
Well-Known Member
Fully agree on this...use a tube buffer like IFI ITUB2...it is an excellent product...you can use it as buffer or preamp(settings are there)...i am using its earlier version and happy with it. Your purpose of tube sound would be solved as well as built is super and you dont have to experiment with tedious tube rolling...
The Yaqin SD-CD2 around 150 USD and the SD-CD3 around 200 USD including shipping.
(you can usually bargain and get around 15/20 usd discount).
You can buy from authorised dealers, ebay or aliexpress.
Custom duty will be applicable.
"DC leak" and DC Offset are two different things.
DC Offset is the presence of a DC component in the output signal which is supposed to be pure AC. This may vary from 1-2 mV of DC in a properly tuned circuit to much more in a poorly tuned one. DC blocking capacitors are usually there in the output stage to avoid passing on the unwanted DC to the next stage. If there's no DC blocking cap, it is called a DC coupled circuit.
On the other hand a DC leak is the presence of DC voltage in the circuit, or in the chassis where none should be there.
Both can be tested easily with a decent multimeter.
To measure DC offset, remove any input from your headphone amp, short the +/- of the input, and measure the DC voltage across the +/- leads of the headphone amp output (check separately for left and right channels). You'll need a multimeter that has a range of 200 mV DC.
For DC leak, put negative probe of your multimeter to metallic conducting part of your chassis and probe the positive probe around various parts of the circuit and chassis, input and output connectors.
Yes, the CD2 is very good value for money. I used with 4 different tube iterations and liked the Voshkods most. I still have two pairs of Voshkods with me. I too have not the CD3, but presume must be good aswell
D
Deleted member 15865
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Guys, thanks for the diagnoses and suggestions. Based on it all, I am currently hypothesising that the Valhalla 2 preamp (whose primary purpose is a headphone amp, but also has provisions to be used as a tube preamp) is not suited to be used with my SS Audiolab 8200A in power amp mode because Valhalla2 adds too much gain which the 8200A power amp is not able to handle causing it to frequently get into protection cut off.
So now, I think I have to start looking for a new preamp. I am quite clear that I want the tube sound - close to, or better than the current one. And my choices would be limited in terms of my budget. I need some suggestions on this, I have noted the Yaqin and Lyrita suggestions. But not sure how much they cost. Also, it’d be difficult for me to make the decision without trying how they sound in my system.
Schiit itself has a proper preamp now, the Freya, which has active tube, passive and JFET buffer stage options. The specs (attached below) show an output impedance of 210 ohms and gain of 5. Do you think, as per your analysis, this would match my Audiolab 8200A power amp section? What other factors I need to check to ascertain this compatibility? Would the problem I face with the Valhalla 2 be non-existent with the Freya? How can I ascertain this without an insystem trial (which I shall check with the authorised dealer if I can get - if they have demo piece and I can take my amp to check). I see the cost would be around Rs 70000, but I like the Schiit sound produced by the Bifrost DAC with the Valhalla 2 today, and imagine the Freya would be close to it, if not better (have to read the reviews in detail yet).
Another option for me is to replace both Valhalla 2 and the Audiolab with an integrated tube amplifier. Are there any good suggestions (sound and reliability wise) that come within Rs 100,000? Especially what I can audition in Mumbai. Please advise.
And, thanks!
So now, I think I have to start looking for a new preamp. I am quite clear that I want the tube sound - close to, or better than the current one. And my choices would be limited in terms of my budget. I need some suggestions on this, I have noted the Yaqin and Lyrita suggestions. But not sure how much they cost. Also, it’d be difficult for me to make the decision without trying how they sound in my system.
Schiit itself has a proper preamp now, the Freya, which has active tube, passive and JFET buffer stage options. The specs (attached below) show an output impedance of 210 ohms and gain of 5. Do you think, as per your analysis, this would match my Audiolab 8200A power amp section? What other factors I need to check to ascertain this compatibility? Would the problem I face with the Valhalla 2 be non-existent with the Freya? How can I ascertain this without an insystem trial (which I shall check with the authorised dealer if I can get - if they have demo piece and I can take my amp to check). I see the cost would be around Rs 70000, but I like the Schiit sound produced by the Bifrost DAC with the Valhalla 2 today, and imagine the Freya would be close to it, if not better (have to read the reviews in detail yet).
Another option for me is to replace both Valhalla 2 and the Audiolab with an integrated tube amplifier. Are there any good suggestions (sound and reliability wise) that come within Rs 100,000? Especially what I can audition in Mumbai. Please advise.
And, thanks!
rikhav
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Pairing a integrated tube amp becomes all the more critical and very much the power requirements of your speaker will be a very important factor to decide
Jolida comes in my mind if you want something in excess of 20 to 30 watts
Not sure about pricing and other details
Jolida comes in my mind if you want something in excess of 20 to 30 watts
Not sure about pricing and other details
For excellent sound that won't break the bank, the 5 Star Award Winning Wharfedale Diamond 12.1 Bookshelf Speakers is the one to consider!
