Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 9:28:27 GMT
Well Mike, the amp has a lot of headroom by the looks of it so the offset wandering a few milli volts either side ain't going to do too much damage to the sound. I checked once you asked and the room wanders from 19 - 22. Once I get the triple glazing and plastic sealing in place, it may go up a tad but I'm considering a great big fan in the ceiling now as well.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 10:47:12 GMT
DC is not going to damage the sound. higher DC's (way above 100mV) can damage the driver due to the constant power that is dissipated heating up the voicecoils without any audible effects. If there is a lot of DC (say over 1V) the diaphragm would not be vibrating linear resulting in distortion at higher levels and failure of the driver because of the dissipated heat caused by the DC.
Here is some rather useless facts about the Panda K701 combo.
The Panda has a maximum ouput voltage of 10V eff (30V peak-peak). Your K701 will be putting out 118dB SPL at full undistorted power. With a hearing treshold of about 10dB (male 40 years old around 1kHz) you will be enjoying a 108dB headroom. This is about 5dB more as a G2 puts out. Ofcoarse the distortion of the Panda will be SIGNIFICANTLY less and sound much cleaner at high volumes.
You should not put a continuous sinewave in full power on the K701 as it is specified to max 200mW and this amp can drive it to 325mW with the 75 Ohm output resistors. With the average power levels present in musical signals this should not be any problem. If the amp had 120 Ohm output resistors the maximum power would remain just below 200mW.
Knowing you like to listen at low levels (90dB, giving 80dB sonic headroom) you will not ever reach these powers unless you were almost deaf which is not the case!
Without the 75 Ohm output resistors the 1.6W the Panda would deliver could potentially destroy your K701 (and other low Ohmic headphones) This (plus all important matching) is why I mentioned mounting these output resistors. Your K701 might be better of with 120 Ohm output resistors as it was designed to be driven by this. With 75 Ohms you will have a tad more treble then if 120 Ohms were fitted.
I do agree with Mike that an output resistance of about 75 Ohm (60 to 90 Ohms) is quite 'universal.
This is the reason I fitted your (obsolete) Bravo with 68 Ohms output resistors instead of the 47 Ohms it came with.
|
|
|
Post by PinkFloyd on Oct 9, 2010 10:56:41 GMT
I have been in touch with Candy at HiFiDIY regarding a "group buy" of these kits... if anyone is interested please let me know, it will give me an idea of how many to order and what the price (per unit) will work out at. They also do a complete Panda kit which comes with everything for $190 USD (about £119 GBP) here it is It says "need your own drilling", I will confirm if the front panel / rear panel comes pre-drilled.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 11:23:57 GMT
I have been in touch with Candy at HiFiDIY regarding a "group buy" of these kits... if anyone is interested please let me know, it will give me an idea of how many to order and what the price (per unit) will work out at. They also do a complete Panda kit which comes with everything for $190 USD (about £119 GBP) here it is It says "need your own drilling", I will confirm if the front panel / rear panel comes pre-drilled. I have contacted him regarding the saving of one postage price if both items Amp kit and enclosure are sent together, as there is plenty of room inside enclosure to to place the Amp kit parts, which weigh very little. Bottom line is NO, cracked on about the weight issue, but me thinks he probably makes his profit from the postage, so he will not send the two items packaged together. Mick.
|
|
|
Post by PinkFloyd on Oct 9, 2010 11:37:02 GMT
DC is not going to damage the sound. higher DC's (way above 100mV) can damage the driver due to the constant power that is dissipated heating up the voicecoils without any audible effects. If there is a lot of DC (say over 1V) the diaphragm would not be vibrating linear resulting in distortion at higher levels and failure of the driver because of the dissipated heat caused by the DC. Here is some rather useless facts about the Panda K701 combo. The Panda has a maximum ouput voltage of 10V eff (30V peak-peak). Your K701 will be putting out 118dB SPL at full undistorted power. With a hearing treshold of about 10dB (male 40 years old around 1kHz) you will be enjoying a 108dB headroom. This is about 5dB more as a G2 puts out. Ofcoarse the distortion of the Panda will be SIGNIFICANTLY less and sound much cleaner at high volumes. You should not put a continuous sinewave in full power on the K701 as it is specified to max 200mW and this amp can drive it to 325mW with the 75 Ohm output resistors. With the average power levels present in musical signals this should not be any problem. If the amp had 120 Ohm output resistors the maximum power would remain just below 200mW. Knowing you like to listen at low levels (90dB, giving 80dB sonic headroom) you will not ever reach these powers unless you were almost deaf which is not the case! Without the 75 Ohm output resistors the 1.6W the Panda would deliver could potentially destroy your K701 (and other low Ohmic headphones) This (plus all important matching) is why I mentioned mounting these output resistors. Your K701 might be better of with 120 Ohm output resistors as it was designed to be driven by this. With 75 Ohms you will have a tad more treble then if 120 Ohms were fitted. I do agree with Mike that an output resistance of about 75 Ohm (60 to 90 Ohms) is quite 'universal. This is the reason I fitted your (obsolete) Bravo with 68 Ohms output resistors instead of the 47 Ohms it came with. Frans.... I'll make up a 40 ohm adaptor for Ian so he can try both 82 and 122 ohm.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 12:34:50 GMT
It sounds quite a powerful amp then. Yes Frans, you're right, normally, I do tend to listen fairly low. I turn the volume up to where the bass just starts to kick in for my ears and that's about it. If I'm listening really critically, I turn up but for general purposes I try to avoid too high, although it's tempting when you get such a clean sound. The K701 is a funny story for me. I didn't write about it for fear of getting people upset/annoyed, but my original one sounded OK at the start and then it kind of went 'unfocussed'. The sound stage seemed way too wide and it felt as though something was wrong, so I did a massive 'burn in' but I didn't notice too much. Just by chance, I mentioned it to the dealer I got them from (a private dealer) and he instantly changed them after contacting AKG. They returned a fault on them so I kept the second pair which were new anyway. However, this pair are much more weighty sounding than the first and they focus like a razor. They are ruthless with amps and when the bass is there, they give quite a kick. I noticed much more recently when I changed my amp set up at home when the bass really started to punch in big time. The fantastic thing is that the initial bass slam clears on them very quickly leaving them open for the rest of the sound to come through, rather than cloud the sound up. (If that makes sense?) With lesser headphones, you often get a good bass clout, but it doesn't go quickly enough to let the rest come through. It kind of hangs around!! I've become very fond of the K701 since I changed them. I'm thinking K702 now, but not sure if the difference is worth it.
|
|
|
Post by PinkFloyd on Oct 9, 2010 14:23:23 GMT
The output impedance of Ian's Panda is 82ohms Frans.... I got a reel of 39R metal film resistors and managed to get a couple close to 38R. I then made up an adaptor so Ian can try both 82 ohm and 120ohm. Ian, when you plug this adaptor in the output impedance will be 120ohms (82 + 38 = 120).... I will have a listen tonight to see how much impact this has. I don't have K-701 anymore but I do have K-501 which are pretty much along the same lines. Will you be trying the HD-250ll with the Panda?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 14:42:25 GMT
I have been in touch with Candy at HiFiDIY regarding a "group buy" of these kits... if anyone is interested please let me know, it will give me an idea of how many to order and what the price (per unit) will work out at. They also do a complete Panda kit which comes with everything for $190 USD (about £119 GBP) here it is It says " need your own drilling", I will confirm if the front panel / rear panel comes pre-drilled. Possibly safe to assume it's just the base plate that will need drilling for the stand-offs, transformer etc. Quote from site= The kit included:
1) Panda headphone amp kit -------------one
2)110-240V universal A type transformer
3) PANDA amp special extension rod
4) a set of headphone amp chassis
5) import RCA4 and all chassis parts
it Can form a whole amp, floor need your own drilling
|
|
|
Post by PinkFloyd on Oct 9, 2010 14:49:07 GMT
I have been in touch with Candy at HiFiDIY regarding a "group buy" of these kits... if anyone is interested please let me know, it will give me an idea of how many to order and what the price (per unit) will work out at. They also do a complete Panda kit which comes with everything for $190 USD (about £119 GBP) here it is It says " need your own drilling", I will confirm if the front panel / rear panel comes pre-drilled. Possibly safe to assume it's just the base plate that will need drilling for the stand-offs, transformer etc. Quote from site= The kit included:
1) Panda headphone amp kit -------------one
2)110-240V universal A type transformer
3) PANDA amp special extension rod
4) a set of headphone amp chassis
5) import RCA4 and all chassis parts
it Can form a whole amp, floor need your own drillingBreaking it all down if you were buying the parts seperately.... Panda kit amp - £50 shipped Enclosure - £50 shipped Transformer - £15 Phono sockets - £4 Total - £119 So..... it's actually cheaper to buy the bits yourself.
|
|
mrarroyo
Been here a while!
Our man in Miami!
Posts: 1,003
|
Post by mrarroyo on Oct 9, 2010 14:54:40 GMT
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 14:57:03 GMT
Mike, I'll be trying everything decent that I have with it. Primarily, I have been using K701 but will happily use HD600, HD650, HD250, AT AD700, AD ES7 and I'll get a Beyer DT150 from work. DT770 has gone now. My HD250 is knackered though 'cos I sent you the better one. I wouldn't mind another one of those too!! Again, it's cost for yet another headphone. ooh - also, the Superlux 681's. If anyone wants me to try them with any headphone, just send the headphone and I can get back. I have been toying with HD800 but it's a lot of dosh and I wouldn't consider it unless I had a top notch amp to drive it with. This may be the one that pushes me. K702 has been on my mind but again, may be copy of 701 in most respects. To some people, seeing a blue headphone instead of white makes them hear a difference. Generally, I find the same characteristics run through the lot tbh, so if there is say a bass lift, they all show it. I think the biggest differences show between high/low impedance headphones - especially in noise department which as you know Mike, I seem to tune into with ease!! Actually, I'm very interested what it'll do with ATH AD700. An interesting headphone imo. Criticised for its lack of bass which I don't have a huge problem with actually. It may be to do with ear shape and where it fits on your head and I do wonder whether it demands lots of current to make it shine. So many headphone people listen to it with no amplification because of what they're told and I find that it reacts rather well to good amping. To be honest, I'm not sure that the output impedance will have a massive effect - we'll see. I have adapters here for different purposes and one that I have in line sometimes with earbuds into amps just suck the bejaysus out of the attack. They lose some of their liveliness which is not actually that flattering if I'm honest. The added impedance may add flatness to them, but to me, they lose their mojo!! I have a feeling that I'm in for a surprise with this amp given its output power - especially in to K701, the weight that you hear from it, Mike, and finally, it looks bloody gorgeous if I'm honest!! And let's face it, it's been put together by someone who knows what he's doing which means reliability and fine tuning to the n'th degree. I know you get really intense about tuning/getting it right Mike as the X-Cans that I have show without a doubt. All with you guys out there looking over his shoulder. (No pressure eh?) Takes a lot for someone to stick their neck out like that in front of people with knowledge. A bit like playing in front of a load of music critics. Talk about open policy? I'm very jealous of myself.
|
|
elysion
Been here a while!
Team Anti M$ AND Facebook.
contra torrentem
Posts: 2,375
|
Post by elysion on Oct 9, 2010 16:56:15 GMT
It sounds quite a powerful amp then. Yes Frans, you're right, normally, I do tend to listen fairly low. I turn the volume up to where the bass just starts to kick in for my ears and that's about it. If I'm listening really critically, I turn up but for general purposes I try to avoid too high, although it's tempting when you get such a clean sound. The K701 is a funny story for me. I didn't write about it for fear of getting people upset/annoyed, but my original one sounded OK at the start and then it kind of went 'unfocussed'. The sound stage seemed way too wide and it felt as though something was wrong, so I did a massive 'burn in' but I didn't notice too much. Just by chance, I mentioned it to the dealer I got them from (a private dealer) and he instantly changed them after contacting AKG. They returned a fault on them so I kept the second pair which were new anyway. However, this pair are much more weighty sounding than the first and they focus like a razor. They are ruthless with amps and when the bass is there, they give quite a kick. I noticed much more recently when I changed my amp set up at home when the bass really started to punch in big time. The fantastic thing is that the initial bass slam clears on them very quickly leaving them open for the rest of the sound to come through, rather than cloud the sound up. (If that makes sense?) With lesser headphones, you often get a good bass clout, but it doesn't go quickly enough to let the rest come through. It kind of hangs around!! I've become very fond of the K701 since I changed them. I'm thinking K702 now, but not sure if the difference is worth it. FritzS had both and beside the colour, detachable cable and different wiring they are absolutely the same (many of their parts have the same part number). I'm not sure how I should rate my K702 at the moment. I've had very pleasant hours listening to it, especially with the Neco Mosfet V2 and the PreSonus HP4. The soundstage is really very wide compared to other 'phones. But I'm not sure if they have the same issue as your first K701. My problem is more the treble of the K702. The treble isn't that bad overall, but I find it a bit annoying if I listen over longer periods (I have not problems with ear fatigue though). I still like them but I use mostly other 'phones at the moment (SR850 with AKG velours pads, HD650 and K501). I really like the overall build quality of the K702 though and for me it is very comfortable to wear (I know that others had problems with the headband). I've noticed that my K702 shows very different results with differnt music styles. Some music sounds absolutely great, some does not. I'm almost sure the K702's aren't the best headphones for listening at very low volumes since they need some power to really deliver what they can. I hear really a kind of "loudness barrier". Below this barrier they sound rather boring. Above that barrier they are not the same anymore. Rabbit, I'm almost sure that this is what you call "where the bass just starts to kick in". IMO it's not only the bass that is improved above that barrier, it's also the treble. I'm beginning to realize that perhaps I have listened with too low volume for some time. The discussion about the output impedance and the adaptors is very interesting. I'm very curious about the results. I have not much knowledge about this, but the impedance of the available headphones is very varied (just as is the output impedance of amps). Maybe a stupid question: Could this be why some headphone/amp combination don't sound as good as others? I must admit that I don't know the output impedance of my amps and that I do unterstand the topic only partially (from a technical side). Are there any standards for the output impedance of headphone amps? Since the impedance of headphone is very varied, I could imagine that there are similar difference with the amps.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 18:04:00 GMT
Hi Christian,
What you're describing is exactly what I was getting; especially on the first pair. There was something just 'wrong' with the sound. AKG admitted nothing. They just confirmed a fault and because I tend to go to a private dealer, more notice was taken. (Also because of my job)
The second pair still need to be turned up to a point where the focus 'snaps' and then stop there!! However, as you say, it also depends on the music.
Alex kindly sent me some wavs to compare though and it has made me realise that I need to look more at my source. I'm not kidding, but any more bass would have been too much on these files. They are outstanding and I compared one to the original CD.
It made me realise that the headphones are like lasers and point out very tiny nuances and differences in sound. Much more so than the Sennheisers which tend to print their own sound sig on top of whatever you put through them. I suspect that's why some people don't like the senns - the planting of another sound sig on top of the original set up!!
The K701 seems really flat and analytical so it tends to show everything.
Now I'm really curious about the Panda with it because of all the headphones I have had, the K701 has been the most problematic with matching. Also, they do seem to need a lot of power behind them to sound good and deliver good bass slam in particular. The Panda sounds like it has some real power which may well kick the bass on the 701 into life with all the headroom available. That's what I'm really curious about.
If this is the case, then these kits are a fantastic buy if you're up to making them. I know my limitations and lack the confidence to do this type of thing and when you see what Mike has done, you can see why i feel like that!!! I'm OCD with sound and if I become aware of something that I've done inside that's not quite right, I can't let it rest. Mike is also slightly OCD in the way that he works so it gives me massive confidence in his work. This group buy may be really worth a go.
I think Alex has now cost me a fortune since I feel that I need to update my front end and my current front end isn't that cheap either!!
The other thing that altered them for me (Although I don't think Frans is that convinced by it) was the addition of a buffer. That suggests to me that there is something wrong at the front and the buffer helps. (Or it has a sound sig of its own) All I know is that my headphone started to sound fatter and more convincing with the buffer in line.
I now wonder whether the input impedance has more of an effect than the output impedance which I find more subtle. Or simply taking the load away from the output device just ames everything work better - I don't know. opinions vary with these devices, but I was really lucky when one became available for me to have a go with.
|
|
|
Post by PinkFloyd on Oct 9, 2010 19:10:00 GMT
Christian,
Off topic but has your V3 arrived yet? I posted it on 28th September.... should be there by now?
Mike.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 19:47:15 GMT
The output impedance of Ian's Panda is 82ohms Frans.... I got a reel of 39R metal film resistors and managed to get a couple close to 38R. I then made up an adaptor so Ian can try both 82 ohm and 120ohm. Ian, when you plug this adaptor in the output impedance will be 120ohms (82 + 38 = 120).... I will have a listen tonight to see how much impact this has. I don't have K-701 anymore but I do have K-501 which are pretty much along the same lines. Will you be trying the HD-250ll with the Panda? Excellent Mike ! I think Ian will be able to hear the difference between the 2 resistance, small they may seem though in resistance the impact of changing the output resistance of amps (varying greatly in effect with different cans) mostly is bigger then the change of amps themselves (provided they have the same output resistance, otherwise a different story) There is another option that (given Ian's armory) might be interesting for Ian. Make the output resistance 39 Ohm (or something like that) and make one more adapter. This way he has 3 output impedances to play with. and yes, the Panda will certainly drive the HD800, but this MIGHT be driven better with even lower Ohmic output resistances of say 10 Ohms (all my amps are 10 Ohms and 120 Ohms selectable). You DO have to be carefull with 10 Ohms output and 32 or 64 Ohm cans though. My biggest fear of destroying cans (except the cheap ones that are inexpensive to replace) comes from those horrible RCA's Why Well there is nothing wrong with the mechanics or contacts when they are plugged in. The problem (I've blown speakers because of this) is simply when you left the power amp on accidentally and plug in an RCA (or unplug too slowly). The problem is the signal pin makes contact BEFRORE the ground does (there are special plugs that prevent this) resulting in a HUGE hum or even oscilations alike 'screams' destroying tweeters. If only they had made the sheath (ground) longer so it would make contact before the centre pin (signal) made contact this plug would have gotten my vote. Alas it's 'standard' now. Most amps on the market DO have different output resistances.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 19:58:28 GMT
Do they end to vary by much Frans? Makes you wonder what goes with what really.
It's the extremes that feel out of kilter with headphones. You seem to either get a fat bass or too much top with a thin bass.
If it's headphone output on amps, then there's a real case for proper matching and it would be useful if headphone manufacturers and headphone amp people to give out the figures so that proper matching can take place since there seems to be no standard configuration that's accepted by all. (Although Beyer and AKG went for 120 ohms I believe)
|
|
|
Post by PinkFloyd on Oct 9, 2010 20:02:07 GMT
The output impedance of Ian's Panda is 82ohms Frans.... I got a reel of 39R metal film resistors and managed to get a couple close to 38R. I then made up an adaptor so Ian can try both 82 ohm and 120ohm. Ian, when you plug this adaptor in the output impedance will be 120ohms (82 + 38 = 120).... I will have a listen tonight to see how much impact this has. I don't have K-701 anymore but I do have K-501 which are pretty much along the same lines. Will you be trying the HD-250ll with the Panda? Excellent Mike ! I think Ian will be able to hear the difference between the 2 resistance, small they may seem though in resistance the impact of changing the output resistance of amps (varying greatly in effect with different cans) mostly is bigger then the change of amps themselves (provided they have the same output resistance, otherwise a different story) Most amps on the market DO have different output resistances. Still something I haven't had time to experiment with (yet) on the Panda Frans. Thing is, with me, I listen to a wide range of headphones so would prefer a "jack of all trades" output impedance rather than a selector switch with 100 different settings .... I have always been pretty happy running @ 75R.... it seems to fit most 'phones quite well.... I'm not too keen on the "zero ohm" idea, maybe good for a few 'phones but the majority of the headphones I have appreciate a few ohms on the output. Why don't they design a headphone with an inline variable resistor and call it something dumb like a "mood control"? Seems so daft that we are messing about at the amp end when all it needs is something simple like a dual variable resistor fitted somewhere on the headphone itself. Inline volume controls are a waste of space (IMO) much better to have a high quality dual inline variable resistor, say 3 to 120 ohm.
|
|
|
Post by PinkFloyd on Oct 9, 2010 20:08:08 GMT
Good idea actually.... a precision variable impedance filter box (PVIF).... let your ears judge what sounds best.... no markings or indications on the filter just a dial.... 3 to 120 ohms..... turn the dial until your ears are happy.... We could make a FORTUNE from such a device
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 20:09:23 GMT
>> Do they end to vary by much Frans? Makes you wonder what goes with what really. <<
They vary from 10 Ohms to 120 Ohms. Some DAP's have output resistances nearing 0 Ohms (but these do not deliver high voltages and thus is not harmfull but DOES change the SQ. If you connect such an output to an amp that has a higher output resistance (most of the amps that can power 32 to 600 Ohms HAVE (they must have)) there can be a substantial improvement. For a BIG portion this is coming from the output resistance but also because of the drive capabilities of these amps that are far better from amps (especially driving low Ohmic headphones in the bass department)
Like Alex already described.. the higher the resistance the less treble (usually) and the more 'bass heavy' it will sound. The effect of these output resistances might be bigger for certain cans and smaller for other cans, so very can dependant. On some it even has very little if even unnoticeable effect (apart from the obvious drop in volume) effect.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 20:17:04 GMT
I've done that! (Trust me) It's an appealing idea to have variable output tuned by 'ear' for the highly discerning!! This is an issue that comes up quite a lot in hi fi forums and people are always asking for adapters. Meier Audio used to sell little portable ones too. (75 ohm) He's stopped now though. variable on an amp sounds like a killer selling point to me.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 20:19:37 GMT
The variable output resistance is a good idea IF you know what you are doing. a 1W (wirewound ?) 100 Ohm potmeter would already do the trick in series with a 10 Ohm resistor. Problem I have with it is IF you are clueless about it's effects and want to use it because you have a big armory you might have set the output resistance to a very low value while listening to 600 Ohms cans. change them to 32 Ohm cans and still have it on a higher volume (600 Ohms need a higher voltage to reach the same SPL as a low Ohmic can) and damage your HP or even ears when accidentally turned to full power. This potmeter MIGHT be misused by people. Also when you would use a pot and dila in to a certain value the SPL would go down too (like the cheap inline volume controls, which alter more then just the volume). This lowering in volume also has it's impact on the SQ ( as Ian correctly describes by his turning up the volume till the bass is 'right') In this case lowering the volume seems to drop the overall sound signature too together with the resistance and the effect it has on the SQ. This will be hard to tell apart for most I reckon. You're initial thought of the 'universal' output resistance is not a bad idea.. The thing Chris? mentioned before with a 3 or 4 way switch is already sufficient for most 'tweakers'. What can be made (even cheaply ?) is a box that connects to an amp that simply has a 3 to 6 way switch or above mentioned potmeter and a output socket. Problem with this solution is the amp MUST have a low Ohmic output resistance of max 10 Ohm for it to work properly as it is connected in series AND the amp must be able to deliver enough voltage.. Funny thing is even über amps like the Phonitor only have 1 output resistance (9 Ohm actually). It does, however, know what impedance is connected and limits it's output voltage accordingly. Don't know how they do it, but if I neede to build something that has this feature I would make an amp that could deliver a high voltage connect it to a 300Ohm output reistance, from this point I would do the overall feedback and after that point mount a 10 Ohm resistor. Resulting in a 10 Ohm output resistance that cannot burn out cans and easily drive any type of headphone. Maybe they made something in a similar way... The 120 Ohm output some cans prefer however cannot be made this way.
|
|
|
Post by PinkFloyd on Oct 9, 2010 20:51:49 GMT
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 21:11:28 GMT
To fit after the headphone socket between amp out and headphone plug?
ie: an external adapter?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 9, 2010 21:14:39 GMT
Yes.. We are certainly not alone in acknowledging the importance of the output imedance. The box described has a 4 value setting which is enough for most cases. Too much choice would puzzle most users and create too small differences between settings making too small audible differences between steps which might be too little audible in this case and cause more confusion because it would only seem to decrease the volume (SPL) in this case. It would be handy for those who know what it is meant for and have the proper amps to drive it. Would consider 4 to 6 steps though but the problem remains... The amp in question must have a low output resistance and be able to deliver a high enough voltage. Problem being not all amps specify their maximum output voltage and also do not spec their output resistance. Mostly they only mention... suitable for 32 to 600 Ohms or something and thus unknow output resistance. An amp with a 120 Ohm output for instance would only become 130 to 240 Ohms and not the also desired 10 Ohms in some cases. I would make a box with 0 Ohm (because 10 Ohm is already in the amp and must be added with all the resistances), 12 Ohm, 33 Ohm, 47 Ohm, 68 Ohm, 110 Ohm . Or perhaps a (wirewound) 100 Ohm potmeter to make it 'gapless'.. Doesn't mean it should discourage anybody making these boxes. Should I ever have the time... First I want to finish a good working transformer amp (low freq is very difficult to get right with higher voltages and a big bandwith, saturation is a b!t@# in small transformers at thes e frequencies) ahhhh time... if only I had enough of that.
|
|
|
Post by PinkFloyd on Oct 9, 2010 21:26:45 GMT
Yes.. We are certainly not alone in acknowledging the importance of the output imedance. The box described has a 4 value setting which is enough for most cases. Too much choice would puzzle most users and create too small differences between settings making too small audible differences between steps which might be too little audible in this case and cause more confusion because it would only seem to decrease the volume (SPL) in this case. It would be handy for those who know what it is meant for and have the proper amps to drive it. Would consider 4 to 6 steps though but the problem remains... The amp in question must have a low output resistance and be able to deliver a high enough voltage. Problem being not all amps specify their maximum output voltage and also do not spec their output resistance. Mostly they only mention... suitable for 32 to 600 Ohms or something and thus unknow output resistance. An amp with a 120 Ohm output for instance would only become 130 to 240 Ohms and not the also desired 10 Ohms in some cases. I would make a box with 0 Ohm (because 10 Ohm is already in the amp and must be added with all the resistances), 12 Ohm, 33 Ohm, 47 Ohm, 68 Ohm, 110 Ohm . Or perhaps a (wirewound) 100 Ohm potmeter to make it 'gapless'.. Doesn't mean it should discourage anybody making these boxes. Should I ever have the time... First I want to finish a good working transformer amp (low freq is very difficult to get right with higher voltages and a big bandwith, saturation is a b!t@# in small transformers at thes e frequencies) ahhhh time... if only I had enough of that. Why I just stick with 75R and be done with it
|
|