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Post by Deleted on Sept 19, 2015 4:33:55 GMT
Try high input gain and low output gain with low impedance headphones. You'll lose the hiss. I sometimes connect a Momentum which will hiss at high output. The K550 also needs low output. Shouldn't that be the other way around? Low input gain & high output resistance will surely reduce the hiss better. What am I missing? |
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Rabbit
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Post by Rabbit on Sept 19, 2015 6:47:01 GMT
High input gain would ensure low signal to noise and low output gain reduces the power. Then if it's still too loud, low input is what I'd do. I'd try high input first. The noise floor doesn't change if you alter the input gain so it's worth trying the higher input first and checking the vol pot travel. Interestingly, some low impedance headphones still need lots of current to be available but they're still quite sensitive to noise, like hiss. So it's surprising how much gain is needed. It doesn't necessarily mean that they're that sensitive but I find that most are prone to pick up noise, even with vol pot off on some amps. I've found that OK with my Denon and TH900. If you still want it lower in volume, then the output inpedance can be raised. That might alter the sound though. The Polaris has output gain as well as output impedance. (Also bandwidrh adjustment) TBH, I prefer higher impedance headphones on the whole. Using a 600 ohm Senn Pcx headphone yesterday, and it seems like grease lightening on attack compared to my low impedance ones. If there was a 600 ohm hd650, I'd be tempted. The output impedance should be used as a kind of frequency response 'adjuster' rather than gain I would have thought although raising the output impedance would also lower the volume. You could shut it right down if you wanted .... Low input gain, low output gain, high output impedance. That might even work with iem's!!! I just thought ... The Ember doesn't have output gain does it? I'm up in bed atm, so I can't check without getting up. In that case, the output impedance WOULD have to be raised, but not always best for sound, depending on the headphone!!  |
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Rabbit
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Post by Rabbit on Sept 19, 2015 7:21:17 GMT
I just checked the manuals.... The Ember doesn't have output gain, but the Polaris does. So ignore my rambles above for the Ember. It' has to be low input gain, high output resistance, which might alter the sound. I guess that's an advantage with the Polaris.... You can take the gain right down as well as raise output impedance. So many choices!!!!!  |
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Post by tunkejazz on Sept 19, 2015 7:21:22 GMT
High input gain would ensure low signal to noise and low output gain reduces the power. Then if it's still too loud, low input is what I'd do. I'd try high input first. The noise floor doesn't change if you alter the input gain so it's worth trying the higher input first and checking the vol pot travel. Interestingly, some low impedance headphones still need lots of current to be available but they're still quite sensitive to noise, like hiss. So it's surprising how much gain is needed. It doesn't necessarily mean that they're that sensitive but I find that most are prone to pick up noise, even with vol pot off on some amps. I've found that OK with my Denon and TH900. If you still want it lower in volume, then the output inpedance can be raised. That might alter the sound though. The Polaris has output gain as well as output impedance. (Also bandwidrh adjustment) TBH, I prefer higher impedance headphones on the whole. Using a 600 ohm Senn Pcx headphone yesterday, and it seems like grease lightening on attack compared to my low impedance ones. If there was a 600 ohm hd650, I'd be tempted. The output impedance should be used as a kind of frequency response 'adjuster' rather than gain I would have thought although raising the output impedance would also lower the volume. You could shut it right down if you wanted .... Low input gain, low output gain, high output impedance. That might even work with iem's!!! I just thought ... The Ember doesn't have output gain does it? I'm up in bed atm, so I can't check without getting up. In that case, the output impedance WOULD have to be raised, but not always best for sound, depending on the headphone!! Yes you are right, I guess it is easy to confuse "low output gain" with "low output resistance" which is the opposite :-) Edit: Mehh, I just saw your last post, please forget what I just wrote :-P |
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Rabbit
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Post by Rabbit on Sept 19, 2015 7:24:50 GMT
Exactly. Resistance might alter the sound, but gain alters volume but not the sound!! I just had a look at the handbook and the Polaris has a bit more choice in this respect. I'd forgotten that the Ember doesn't have output gain on it. Must have had a rough night last night!!!  |
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solderdude
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Post by solderdude on Sept 19, 2015 7:26:16 GMT
Try high input gain and low output gain with low impedance headphones. You'll lose the hiss. I sometimes connect a Momentum which will hiss at high output. The K550 also needs low output. Shouldn't that be the other way around? Low input gain & high output resistance will surely reduce the hiss better. What am I missing? Yes, to reduce noise a High output R will reduce noise levels and indeed CAN influence tonal response but this depends on the used headphone. So does the noise attenuation depend on the impedance of the headphone. Noise levels are also tube dependent, even more so in Ember1 another way to reduce noise levels is to bypass the input capacitor in Ember 1 but the pot will be scratchy when you adjust the volume. I have talked to Jeremy about output attenuators which would be very beneficial but so far he has not made them. A small 'extension cord' with 2 resistors in the plug and the G1217 amps set to 'medium output R' would be perfect IF you have some background his in your favorite tubes. Perhaps I should start making them myself..... |
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Rabbit
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Post by Rabbit on Sept 19, 2015 7:28:29 GMT
Frans, is it not possible to do have what the Polaris has on the next version and offer lower gain on the output with a jumper?
I find that one of the Polaris' real strengths since it'll match anything.
For me, that was the decider between the two of them way back, since sound differences are pretty small. Also, many tubes can be pretty noisy.
I often find high input gain but low output gain works really well for some low impedance headphones, with low output impedance. No noise and lots of life in the power like that.
The Ember offers just low input gain and high output impedance to bring gain right down. Lowering input gain changes s/n and impedance can alter sound and attenuate internal noise with the volume, so s/n isn't that massively altered, just gain.
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solderdude
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Post by solderdude on Sept 19, 2015 7:44:26 GMT
The Polaris works differently indeed.
the noise of the FET is lower, there is no 'grid' leakage issue (in this case gate leakage) and the amplification factor can esily be changed on the FET input stage without resorting to overall feedack.
The G1217 amps have input attenuators and this differs from gain but has a similar 'overall' effect in that you can get a better volpot adjustment range on a wider array of headphones and sources.
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Rabbit
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Post by Rabbit on Sept 19, 2015 7:50:48 GMT
Yes, I just checked the manuals. It is something that crops up quite a lot with the Ember on HF. Given that so many headphones are coming out at lower impedance thanks to Ipods and IPhones there's quite a call for lowering the gain.
I find the Ember a bit difficult with the th900 which is very sensitive and also quite revealing. The only option is to raise the output impedance in order to reduce hiss from amp and tube. The Polaris is another thing altogether in this respect. In fact, it's the lowest noise amp I'm using (subjectively) via prudent use of gains. That's one reason why I like it so much.
The Ember is more prone to noise issues as well due to the tubes that some are using. They're not the quietest of things at the best of times and lowering the output gain could disguise this; especially if the input gain is higher. S/n might be improved even with a relatively noisy tube.
The Polaris is dead silent, even with the Th900 and if anything will dig out noise, that headphone will!!!
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Deleted
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Post by Deleted on Sept 19, 2015 9:41:30 GMT
With my Ember 1 I've been able to use some low impedance headphones and IEMs using an iFI audio (aka Yongsheng) -24db attenuating adapter. As recommended by Frans I use it with the amp set to Low R, which gives the same volume attenuation as you'd get from High R but without the resultant increase in output impedance (it might go up marginally but still 1 ohm or less I think). Even with my most sensitive headphone (8 ohms / 104db) this gives me plenty of play on the volume pot and seems to more or less eradicate any noise floor. Do the headphones sound as good as they do straight from the Ember (ignoring hiss & lack of vol adjustment)? Hmmmm, I'm not sure as I haven't really spent enough time with it hto really draw a conclusion. Sounds perfectly acceptable though. I do suspect that any attenuator made by Frans & Jeremy (fingers crossed) will be better conceived than this one as I do have a few gripes / concerns that make the iFI attenuator hard to recommend at present: - price. Approx. £30 delivered. Appreciate in the hi-fi world that might not be a bad deal but these adapters (or the one I got) were originally knocked up for internal use and 'escaped' into the wild. As a result it feels a little steep imho. - durability?...questionable at best right now based on my experience thus far. The cable is quite thin and the attenuation module that hangs from one end is reasonably weighty which may put some strain on the connections, esp. if it hangs off a desk rather than rest on something. The first one I received lasted 3-4 uses before the sound started going 'wonky' (suspect a loose connection internally as bending the cable or turning my headphone jack would resolve it). May just have been unlucky but it was handled with care so not a result of 'stress testing'. A couple of days back I finally received my replacement which is from the latest batch and apparently has been 'revised' in some way - can't see any difference whatsoever outwardly aside from some slightly messy clear glue / sealant residue at the points were the cable enters the output jack and attenuating module. Some glue was evident on the first one too (they use it to pack any gaps I think) but perhaps they've used a bit more on this one...hope they revised more than that lol. - terminated with a 3.5mm jack plug ...really? Not a deal breaker but it really puzzles me why iFI would use one when you consider that all their products have 6.35mm inputs. - (take with a pinch of salt) I do wonder if the resistors used are the same ones the guys would pick for their amps? Perhaps they would, perhaps they wouldn't. I just know they know their amps better than anyone else which gives me comfort they'd pick the ones for 'optimal' performance. I may have a buyer lined up for my Ember so not sure how much time I'll really have to put the attenuating cable through it's paces but will post an update if there are any developments. If the Ember sells then I'd be happy to put this on a wee DIYAH tour if there is interest* (first dibs Ian?)? * purely to let people try their low impedance phones with their Embers and get an idea of the benefits using one may bring. Then you can nag Frans / Jeremy to make one |
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Post by Deleted on Sept 19, 2015 9:46:23 GMT
I just checked the manuals.... The Ember doesn't have output gain, but the Polaris does. So ignore my rambles above for the Ember.
It' has to be low input gain, high output resistance, which might alter the sound. I guess that's an advantage with the Polaris.... You can take the gain right down as well as raise output impedance. So many choices!!!!! Funnily enough, I did exactly that  |
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Rabbit
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Post by Rabbit on Sept 19, 2015 10:09:05 GMT
Mark, with something really sensitive, if I want the tubey sound, I put an adjustable resistor on the output, turn the volume off and adjust the attenuation to get rid of any hiss there, before I turn up. Just a cheap thing but it works as well for those portable radios that hiss with no volume. Gordon, it's amazing what reading the instruction book does, isn't it? The Polaris is actually a lot quieter than the Ember but that might also be my reluctance to play around with tubes and hear these enormous differences!! |
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Post by Deleted on Sept 19, 2015 10:27:11 GMT
Sounds interesting Ian. You don't happen to know who makes it do you or have a link?
Curious to take a look.
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Rabbit
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Post by Rabbit on Sept 19, 2015 10:51:12 GMT
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howie
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Post by howie on Sept 19, 2015 11:26:27 GMT
I do exactly the same with a Sennheiser HZR- 62 volume control. It's a good balance control too. There is a slight reduction in brightness in the treble but this is sometimes welcome and always better than hiss. That may well be because of what Frans is saying. The output impedance has been raised. You won't get hiss with an hd650 Gordon. It's the very low impedance types. I think my Denon is only about 20 ohms and the th900 is also quite low. Some tubes are also comparatively noisy as well. If you're using higher impedance headphones, you'll get no noise coming through. |
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