QUAD PA-One Valve Headphone Amplifier and DAC
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Thanks for bumping the thread, appreciate your input a lot !

I was thinking about the tubes (down the road). I guess Sophia tubes you mention carry the same mark - model designation - 6SL7 and 6SN7, and I am presuming the same applies for the rectifier, disregarding the manufacturer. Just wanting to avoid any mishaps and confusion, tubes of course have to be always properly matched within the range of el. specs. of the amp in question; hereby I presume that there are range of compatible tubes (and rectifiers).

I would be curious to hear how these particular tube change (or well, rather affect) the sound signature compared to stock tubes.

In case I have missed; I have not seen what headphones are you driving with the Quad Pa One ?
I went through about $2k in tubes before I landed on the Sophia. RCA Red Base are very nice, but the Sophias are beyond glorious. And they're current production. Go for the top grade. A shop in San Antonio got them for me for $95 each. My headphones... HiFiMan HE-1000 V2
 
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Thanks for bumping the thread, appreciate your input a lot !

I was thinking about the tubes (down the road). I guess Sophia tubes you mention carry the same mark - model designation - 6SL7 and 6SN7, and I am presuming the same applies for the rectifier, disregarding the manufacturer. Just wanting to avoid any mishaps and confusion, tubes of course have to be always properly matched within the range of el. specs. of the amp in question; hereby I presume that there are range of compatible tubes (and rectifiers).

I would be curious to hear how these particular tube change (or well, rather affect) the sound signature compared to stock tubes.

In case I have missed; I have not seen what headphones are you driving with the Quad Pa One ?
Don't overlook the rectifier. Some folks say it has no effect... it does... big time. Tubes supplied with the Quad are low-end stuff. Also... although the Quad accepts XLR cabling, the internals are not truly balanced. I'm using Cardas Clear RCA into the box, and Cardas Clear Headphone out to the phones.
 
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I went through about $2k in tubes before I landed on the Sophia. RCA Red Base are very nice, but the Sophias are beyond glorious. And they're current production. Go for the top grade. A shop in San Antonio got them for me for $95 each. My headphones... HiFiMan HE-1000 V2
Your headphones were mentioned in superlatives in one review of the Quad Pa One in the local press. It has been said that the holographic feeling produced by this combination (Quad Pa One + HE-1000) is eery and sublime.
I am listening at the moment one of the Nora en Pure podcasts, and although we are talking about the tracks that are not of the highest bit and sampling rate (I presume) some of the tracks (all of them, but some in particular) are unreal - the control and the grip the amp exerts on the K701 driver is just beyond excellent.
 
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Don't overlook the rectifier. Some folks say it has no effect... it does... big time. Tubes supplied with the Quad are low-end stuff. Also... although the Quad accepts XLR cabling, the internals are not truly balanced. I'm using Cardas Clear RCA into the box, and Cardas Clear Headphone out to the phones.
From what I have read about the rectifiers across the web and here at headfi, if memory serves me right, the rectifiers do matter; I would be always careful to match their electric characteristics properly to the amp in question.
I have no idea what tubes I got with my Quad, but at the moment I am floored with the sound quality.
On the matter of XLR, I have sold of (together with the solid state amp) the RCA-XLR cables, since they were (the XLR) the only inputs to that amp. Neither that amp was truly balanced (I presume), since the output was SE, and the innards probably confirm the similar to that regard as about the Quad.
Yet, I am using the USB A-B into the Quad of the MacBook Pro Retina, and of the Yamaha CDR-HD1500 will be soon using the coaxial out digital cable (hanging onto the ordinary RCA from that source, for few days more), so I am not sure if the need for the XLR will ever occur, it will be source depending.

Interesting you say "big time" in regard to the rectifier, it will be interesting to feel how it changes the sound (improves it). Feel free to describe, if you ever find the time.
 
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Your headphones got were mentioned in superlatives in one review of the Quad Pa One in the local press. It has been said that the holographic feeling produced by this combination (Quad Pa One + HE-1000) is eery and sublime.
I am listening at the moment one of the Nora en Pure podcasts, and although we are talking about the tracks that are not of the highest bit and sampling rate (I presume) some of the tracks (all of them, but some in particular) are unreal - the control and the grip the amp exerts on the K701 driver is just beyond excellent.
 
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From what I have read about the rectifiers across the web and here at headfi, if memory serves me right, the rectifiers do matter; I would be always careful to match their electric characteristics properly to the amp in question.
I have no idea what tubes I got with my Quad, but at the moment I am floored with the sound quality.
On the matter of XLR, I have sold of (together with the solid state amp) the RCA-XLR cables, since they were (the XLR) the only inputs to that amp. Neither that amp was truly balanced (I presume), since the output was SE, and the innards probably confirm the similar to that regard as about the Quad.
Yet, I am using the USB A-B into the Quad of the MacBook Pro Retina, and of the Yamaha CDR-HD1500 will be soon using the coaxial out digital cable (hanging onto the ordinary RCA from that source, for few days more), so I am not sure if the need for the XLR will ever occur, it will be source depending.

Interesting you say "big time" in regard to the rectifier, it will be interesting to feel how it changes the sound (improves it). Feel free to describe, if you ever find the time.
I'm very critical of the spatial properties of music. What I was chasing, and I'm satisfied I've found it, is to have a private audition inside the sound studio. The rectifier was my first upgrade to the Quad. But the crowning moments were the Sophias and the HE-1000 V2. I recently added a BDR Source Board under my SACD player. That was a nice upgrade. Will do the same for the Quad.
 
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I'm very critical of the spatial properties of music. What I was chasing, and I'm satisfied I've found it, is to have a private audition inside the sound studio. The rectifier was my first upgrade to the Quad. But the crowning moments were the Sophias and the HE-1000 V2. I recently added a BDR Source Board under my SACD player. That was a nice upgrade. Will do the same for the Quad.
Just to tease you.... my Quad is serial number xxxxxx0002. Got it before there was an authorized US dealer.
 
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I'm very critical of the spatial properties of music. What I was chasing, and I'm satisfied I've found it, is to have a private audition inside the sound studio. The rectifier was my first upgrade to the Quad. But the crowning moments were the Sophias and the HE-1000 V2. I recently added a BDR Source Board under my SACD player. That was a nice upgrade. Will do the same for the Quad.
Yeah, that BDR staff is really... well, massive... :D always lends itself well to the tube equipment, I suppose...
 
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Just to tease you.... my Quad is serial number xxxxxx0002. Got it before there was an authorized US dealer.
So you have been about the earliest adopter... how much comparison to other headphone amps went before making a decision ? Even more fascinating decision, from my perspective, since the US market (and Canada) are not lacking in - well - affordable tube headphone amp, that are well known entities, so going for the brittish (albeit famous) manufacturer is interesting. Again, never had the oportunity here to audition neither Woo or Mapletree (althougt people here have imported Woo tube headphone amps, but not in stores), so I do not have the frame of reference towards the US market products.
 
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So you have been about the earliest adopter... how much comparison to other headphone amps went before making a decision ?
I didn't look at any other headphone amps. My soundshop guy saw and heard it at a CES convention and recommended it. I told him to get it. I had to wait a little while, but one day it arrived. A good friend had a top-of-the-line Sennheiser. I shared the Quad... installed in his system. He yanked out the Sennheiser, gave it to his wife and said put it on eBay... and then he ordered a Quad.
 
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I didn't look at any other headphone amps. My soundshop guy saw and heard it at a CES convention and recommended it. I told him to get it. I had to wait a little while, but one day it arrived. A good friend had a top-of-the-line Sennheiser. I shared the Quad... installed in his system. He yanked out the Sennheiser, gave it to his wife and said put it on eBay... and then he ordered a Quad.
I guess that Quad Pa One can be adjusted for the 110V supply by the means of changing something internally (the user manual says something about it) or there is a series produced for the US ?

Yes, the local magazine review here said that they have never experienced the synergy like Quad's with the HD800, and they have reviewed the Senns amps and many other headphone amps prior to that.
 
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I guess that Quad Pa One can be adjusted for the 110V supply by the means of changing something internally (the user manual says something about it) or there is a series produced for the US ?

Yes, the local magazine review here said that they have never experienced the synergy like Quad's with the HD800, and they have reviewed the Senns amps and many other headphone amps prior to that.
Mine came set-up for USA power. Hey, there's another trick you can do for the Quad... I installed a HiFiTuning fuse. It was about $60 from Amazon. There's a little drawer on back of the Quad. Pull that out and swap fuses. I think there's a spare in there... which I thought was a pretty neat feature. Think friend has Senn HD800... or whatever is their top-of-the-line. The HE-1000 V2 are much more spacious and better imaged.
 
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Mine came set-up for USA power. Hey, there's another trick you can do for the Quad... I installed a HiFiTuning fuse. It was about $60 from Amazon. There's a little drawer on back of the Quad. Pull that out and swap fuses. I think there's a spare in there... which I thought was a pretty neat feature. Think friend has Senn HD800... or whatever is their top-of-the-line. The HE-1000 V2 are much more spacious and better imaged.
Quoting the user manual : "

  1. The mains operating voltage the unit is indicated on the rating plate attached to the unit. If this voltage does not match the mains voltage in your area, consult your QUAD dealer about converting the unit. The fuse rating should be:
220-240V T500mA 20mm
100-120V T1 A 20mm "

I have no idea what is the fuse you are referring to, but thanks for the tip, I will check it out now. If ever moving to the US, I would still want to have this amp with me...
 
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Quoting the user manual : "

  1. The mains operating voltage the unit is indicated on the rating plate attached to the unit. If this voltage does not match the mains voltage in your area, consult your QUAD dealer about converting the unit. The fuse rating should be:
220-240V T500mA 20mm
100-120V T1 A 20mm "

I have no idea what is the fuse you are referring to, but thanks for the tip, I will check it out now. If ever moving to the US, I would still want to have this amp with me...
My Quad has a sticker above the on/off switch and tells voltage, fuse, etc. Mine is set-up for US power. MusicDirect had the fuse, but Amazon had it for a lower price. If you do some searching you can probably sink a couple hundred bucks in the fuse. As with any of this stuff, you'll need to give it some 'burn-in' hours. The Sophias took about 50 hours to settle down, but continued to improve after that. Same with the fuse, cables, etc.
 
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My Quad has a sticker above the on/off switch and tells voltage, fuse, etc. Mine is set-up for US power. MusicDirect had the fuse, but Amazon had it for a lower price. If you do some searching you can probably sink a couple hundred bucks in the fuse. As with any of this stuff, you'll need to give it some 'burn-in' hours. The Sophias took about 50 hours to settle down, but continued to improve after that. Same with the fuse, cables, etc.
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.
 
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