QUAD PA-One Valve Headphone Amplifier and DAC
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I think I got this right.
Since the manual states what it does, (about the conversion of the unit to the voltage at the place) - it is probably meant that the fuse has to be swapped for the one appropriate for the 110V voltage and vice versa - accordingly.

Other than that, these fuses are mentioned as the means of the sonic improvement, from what I have read thus far - some claim, by using other materials than copper, that the oxidation is eliminated - reduced, as well as significant improvement in the sound quality. Some german manufactured are around at very affordable prices, considered what they claim in term of materials used in them.
One more thing... Although the Quad accepts XLR or balanced cabling, the internal circuitry isn't balanced, and I believe the Quad's XLR input is grounded. A friend had a major problem with this. He picked up a hum in his system when he used the Quad's balanced inputs. My integrated amp (Ayre AX7-e Evolution) has a prominent warning on the back saying not to connect its XLR to a grounded connection. My friend has Classe equipment, and the Quad's grounded XLR really caused some problems. I just want to put this out as a warning. I don't want you to hurt your components.
 
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One more thing... Although the Quad accepts XLR or balanced cabling, the internal circuitry isn't balanced, and I believe the Quad's XLR input is grounded. A friend had a major problem with this. He picked up a hum in his system when he used the Quad's balanced inputs. My integrated amp (Ayre AX7-e Evolution) has a prominent warning on the back saying not to connect its XLR to a grounded connection. My friend has Classe equipment, and the Quad's grounded XLR really caused some problems. I just want to put this out as a warning. I don't want you to hurt your components.
I found the Phillips/Mullard 6CA4 / EZ81 rectifier at a shop in California. They're $75 now. I bought four or five of them when they were $50... from the same shop. The price increase suggests they're becoming rare. https://www.upscaleaudio.com/products/philips-miniwatt-6ca4-ez81

"Philips Miniwatt EZ81 - These are "da bomb" as the kids say... do they still say that? Branded Philips Miniwatt, but made in the Mullard factory in Great Britain. Philips owned Mullard, so it was quite common to see Mullard tubes branded this way.

These were in bulk packs, so they'll come to you in generic white boxes. We do not match rectifiers, but rest assured they are tested and screened to the highest standards."
 
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I think I got this right.
Since the manual states what it does, (about the conversion of the unit to the voltage at the place) - it is probably meant that the fuse has to be swapped for the one appropriate for the 110V voltage and vice versa - accordingly.

Other than that, these fuses are mentioned as the means of the sonic improvement, from what I have read thus far - some claim, by using other materials than copper, that the oxidation is eliminated - reduced, as well as significant improvement in the sound quality. Some german manufactured are around at very affordable prices, considered what they claim in term of materials used in them.
One more trick to help the sound, and this one shouldn't cost you anything ! This often helps, particularly if you have an older home. Tighten all the wire connections at your power panel. Jacketed wires come into the panel, and the last half-inch or so is stripped and pinch-connected with a bolt. Tighten that connection. If you're not sure what you're doing, please call an electrician. I've also heard of people using high-end circuit breakers for the circuit that supplies their sound system. But I've never heard any amazing results from doing this. Good luck. Take care.
 
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sejsel

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I found the Phillips/Mullard 6CA4 / EZ81 rectifier at a shop in California. They're $75 now. I bought four or five of them when they were $50... from the same shop. The price increase suggests they're becoming rare. https://www.upscaleaudio.com/products/philips-miniwatt-6ca4-ez81

"Philips Miniwatt EZ81 - These are "da bomb" as the kids say... do they still say that? Branded Philips Miniwatt, but made in the Mullard factory in Great Britain. Philips owned Mullard, so it was quite common to see Mullard tubes branded this way.

These were in bulk packs, so they'll come to you in generic white boxes. We do not match rectifiers, but rest assured they are tested and screened to the highest standards."
tubes - valves are endlessly (tube rolling) interesting subject. Holland is not far from here; interesting that the Philips still has the tube production subsidized to the smaller factory - wonder if the Philips themselves are going to pick up on this audio trend of the return of the tubes (have we yet become a big enough segment of the market to become interesting ? ).
Tubes are something that has limited life, they need to be replaced often enough in order to allow the need for continuous production...

I have not entered the tube rolling world... yet...
 
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sejsel

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One more trick to help the sound, and this one shouldn't cost you anything ! This often helps, particularly if you have an older home. Tighten all the wire connections at your power panel. Jacketed wires come into the panel, and the last half-inch or so is stripped and pinch-connected with a bolt. Tighten that connection. If you're not sure what you're doing, please call an electrician. I've also heard of people using high-end circuit breakers for the circuit that supplies their sound system. But I've never heard any amazing results from doing this. Good luck. Take care.
I have started to look into this subject.
Really nice of you to provide all this advice. There is some material at the web regarding the latter advice (with circuit breakers) and power conditioner, for ex. , was a big recommendation to me personally in combination with the Quad Pa One, the source was someone well involved into the headphone amp world.

Still, even only on its own, I know that this amp does a really terrific job with 3 headphones - Sennheiser HD800 (this by many accounts from users and reviewers), AKG K701 and also terrific with the Grado GS1000, should be great with all other Grados as well. I am really thoroughly enjoying it.
What is really interesting here that the Sennheiser HD600 and 650 are named to be favorites of the users in Greece (at some local audio forum) - a headphones really not all that similar in sound signature to these first three mentioned... then again, reviewers have said that the amp works well with wide range of headphones.
 
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tubes - valves are endlessly (tube rolling) interesting subject. Holland is not far from here; interesting that the Philips still has the tube production subsidized to the smaller factory - wonder if the Philips themselves are going to pick up on this audio trend of the return of the tubes (have we yet become a big enough segment of the market to become interesting ? ).
Tubes are something that has limited life, they need to be replaced often enough in order to allow the need for continuous production...

I have not entered the tube rolling world... yet...
If you want to play 'tube rolling' I have a collection I'm willing to part with. RCA Red-base, Heintz-Kaufman (essentially a red-base RCA... in fact they had a patent encroachment suit in 1942, I think), ADZAM (Mazda spelled backwards), Sylvania's , etc... Think the Adzam (or Sylvania) were Holland made. But I told you earlier... go straight for the Sophias.
 
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I have started to look into this subject.
Really nice of you to provide all this advice. There is some material at the web regarding the latter advice (with circuit breakers) and power conditioner, for ex. , was a big recommendation to me personally in combination with the Quad Pa One, the source was someone well involved into the headphone amp world.

Still, even only on its own, I know that this amp does a really terrific job with 3 headphones - Sennheiser HD800 (this by many accounts from users and reviewers), AKG K701 and also terrific with the Grado GS1000, should be great with all other Grados as well. I am really thoroughly enjoying it.
I'm using an IsoTek Sirius power conditioner. Nice improvement.
 
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If you want to play 'tube rolling' I have a collection I'm willing to part with. RCA Red-base, Heintz-Kaufman (essentially a red-base RCA... in fact they had a patent encroachment suit in 1942, I think), ADZAM (Mazda spelled backwards), Sylvania's , etc... Think the Adzam (or Sylvania) were Holland made. But I told you earlier... go straight for the Sophias.
Have some other expenses to take care of at the moment. Will keep you posted very soon via pm here on the proposal. Much appreciated !
 
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Massdrop is selling this amp for a considerable discount.
Has anyone else had experience with the Quad?
Looking at the ongoing discussion for the package sold on Massdrop at this time, it is not Quad Pa One that is sold there, but Quad Va One.
There are enough comments there for making an informed decision regarding whether to buy it or not.
I would say that it eventually depends on the synergy between the intended headphone (of one's choice) with the Va One.
There is at least one comment from someone owning the amp, who states that it works well with the Quad Era-1 headphone, if memory serves me right.
 
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sejsel

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Didn't even notice the difference in labeling PA vs VA. Duh!
Hey, no big deal.
As I have said, it might turn out to work very well with some (or many ? ) headphones, as any amp.
From my experience with Quad Pa One, it might be (Va One) a good purchase (to say the least) and work well with even more demanding (power hungry) cans, who knows...
It would do you a world of good if you had any chance to demo the thing for yourself; however, I know this can be easier said than done...
Don't trust anyone's opinion, not mine either, but for what is worth, the Pa One is really (to me) an exceptional headphone amp, and Va One is not all that unlike Pa One.
Question is how much do they differ.
From what I remember, the Va One does not have the impedance (low-high) switch at the front (or at all), whereas the output transformers on Va One, on the other hand are bigger and can handle more than on Pa One. Having in mind that the Va One is made more as a preamp or amp and not only as a headphone amp, well, yes, it might be a dilemma only solved by demoing.
The price offered at Massdrop for whole package looks attractive.
 
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