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New Leckerton UHA-6S MKII Portable Headphone Amplifier Announced (Update User Impressions Added... - Page 81

post #1201 of 2197

I think that is a feature of the arrow :). Would be a nice selling point for sure.
 

post #1202 of 2197
Quote:
Originally Posted by ardgedee View Post

Quote:
Originally Posted by lee730 View Post

That is channel imbalance due to the volume pot on the Leckerton. Most amps suffer this having volume pots instead of digital pots. But with digital pots you do sacrifice some transparency so its a give and take sort of thing. By far my Triad L3 is the best portable amp (more transportable TBH) in terms of near to no channel imbalance at very low volume listening. In fact I think it is so good I'd be more apt to think it's a digital pot. cool.gif

 

The reason why volume pots have noticeable imbalance at low volume is because that's where minor variations in manufacture become more noticeable.

 

Volume pots mostly work by having a conductive resistive surface that a wiper slides along. At the near point (where volume is highest), electricity travels a very short distance along the surface; minor differences between two surfaces don't add up to much. At the far point (where volume is lowest), electricity is traveling the full length of that resistive surface, and minor differences add up.

 

Higher quality pots are more expensive in part because they require either (or both) closer attention to manufacturing tolerance or higher rates of rejection. Buy a couple dozen identical volume pots of good-not-fabulous quality and test them all at the quietest position. Some will have louder left channels, some will have louder right channels; out of the batch, maybe a couple will have a channel difference subtle enough to be tolerable or maybe imperceptible.

 

Leckerton could spec higher quality pots, but that'd drive the price of the amp up noticeably. Really good pots for non-portable devices can easily go for $50 a pop -- without having to get into the audiophile stratosphere of exotic materials and proprietary designs. You're paying the manufacturer to either spend more time making and testing each one, or for covering the cost of the greater number of rejects they have to make for each one they can sell.

 

Stepped attenuators can get around this by using actual resistor networks rather than a sweeper over a surface, but since that's literally a cluster of tolerance-matched resistors, it's going to be expensive and bulky. Expensive can be tolerated, bulky's kind of a dealbreaker. Digital attenuators have a lot of advantages (compactness, consistency) but aren't necessarily audiophile-approved.

 

I have a SR-71B. Like the Triad, it has uniform channel balance pretty nearly all the way to ∞. Like the Triad, it also costs some multiple of the price of the UHA-6, and part of that markup is to cover the cost of the higher-quality volume pot. Save some money, accept some compromises.

 

I gather Ray buys a heap of pots and reject all the ones with noticeable channel imbalance. I think the main issue with the pots is that at the very beginning of travel where the wipes touch the resistant surface, the exact start isn't perfectly aligned in most.

 

The other option, which you missed, is in the Pico Slim, which uses a volume pot that controls an attenuation chip, avoiding the issue altogether. 

post #1203 of 2197

Isn't the Pico Slim a digital pot? I had mentioned Digital pots but you also sacrifice some transparency with that. But it just depends on what your needs are :).
 

post #1204 of 2197

Yeah, that's actually why I hedged myself with "not audiophile approved" -- I hear complaints about them but I haven't really seen much that proves that they're actually sonically inferior. What I don't really know (and am curious about) is how they compare price/performance-wise with conventional high-quality volume pots.

post #1205 of 2197
Quote:
Originally Posted by ardgedee View Post

Yeah, that's actually why I hedged myself with "not audiophile approved" -- I hear complaints about them but I haven't really seen much that proves that they're actually sonically inferior. What I don't really know (and am curious about) is how they compare price/performance-wise with conventional high-quality volume pots.

 

Well to be honest I still very much enjoyed my Uha4 when I had it and the volume pot in terms of channel balance was better than any conventional pot I've used in term of volume control (multiple steps) and low volume listening without channel imbalance. I mean you have a lot of headroom to tune the volume to your preference. I felt the DX100 also had an advantage with its digital pot. So YMWV.
post #1206 of 2197
Quote:
Originally Posted by ardgedee View Post

Yeah, that's actually why I hedged myself with "not audiophile approved" -- I hear complaints about them but I haven't really seen much that proves that they're actually sonically inferior. What I don't really know (and am curious about) is how they compare price/performance-wise with conventional high-quality volume pots.

 

Well to be honest I still very much enjoyed my Uha4 when I had it. The volume pot in terms of channel balance (for low volume listening without any channel imbalance) was better than any conventional pot I've used. I felt the same in regards to volume control (multiple steps). I mean you have a lot of headroom to tune the volume to your preference. I felt the DX100 also had an advantage with its digital pot as well. So YMWV.
Edited by lee730 - 1/7/13 at 6:28pm
post #1207 of 2197
Quote:
Originally Posted by ardgedee View Post

 

I wonder how it differs from the LME49713. I have a set but haven't had time to try them yet.

49713 is a current feedback opamp -  i would not use it- it has very strict requirements !!!!

post #1208 of 2197
I bought the 49713 from Leckerton after consulting with Nick about it. Nick confirmed that the UHA-6S is capable of keeping it stable.

My interest in the 49713 stems from its use in the Cary XCiter DAC. (Which sounds very good, fwiw.)
post #1209 of 2197

the 49713 is a very good chip, and i have a headphone amp that uses it to directly drive headphones - it'll do 150ma iirc.  it also slews at 1200v/usec and will sprout legs and walk off the board if you are not careful.  I am also told by a member of its design team that it sounds best used in inverting mode, and with a narrow range of feedback r choices.

 

 

how do it sound with the 49713, btw - i am thinking of getting one used and have a huge supply of opamps to chose from at home.

post #1210 of 2197
Don't know, to be honest. I've had a half-dozen opamps sitting around for a few months and only got around to trying one of them this morning. (The OPA627, which is fantastic in the UHA-6S, btw.)
post #1211 of 2197
Quote:
Originally Posted by ardgedee View Post

Don't know, to be honest. I've had a half-dozen opamps sitting around for a few months and only got around to trying one of them this morning. (The OPA627, which is fantastic in the UHA-6S, btw.)


Yep it's one of the most musical Amps I've heard with that Op Amp in it. But it got quite a bit better after running it in for a few days. The sound stage expands and the sound is less aggressive. More euphoric :). Bass and mids are really something on this pairing. Treble takes a back seat but is still quite good (smooth).

post #1212 of 2197
Quote:
Originally Posted by lee730 View Post


Yep it's one of the most musical Amps I've heard with that Op Amp in it. But it got quite a bit better after running it in for a few days. The sound stage expands and the sound is less aggressive. More euphoric smily_headphones1.gif. Bass and mids are really something on this pairing. Treble takes a back seat but is still quite good (smooth).
Can't wait to give those a try...!
post #1213 of 2197
Quote:
Originally Posted by thegrobe View Post


Can't wait to give those a try...!


They got sent out today :).

post #1214 of 2197
I finally got around to ordering a pair of opa627ap recently. Should be arriving later this week. Looking forward to seeing how it changes the tg334 pairing.
post #1215 of 2197

I'd think it would give them a bigger sound stage but also the treble is gonna take more of a back seat. Then again it is already that way on the 334s ;). Bass and mids are very nice though on 627AP.
 

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Head-Fi.org › Forums › Equipment Forums › Portable Headphone Amps › New Leckerton UHA-6S MKII Portable Headphone Amplifier Announced (Update User Impressions Added July 20th 2012)