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  1. Old Comment
    mlloyd1's Avatar

    Which is better, Sennheiser HD600 or AKG K702?

    thanks for sharing.

    interestingly, my conclusions actually coincides with yours, but probably for different reasons . i describe my headphones sound preference as "airy, natural and real". HD600 fits this sound to me better than any headphones i've heard (but i haven't listened to any of the planar designs nor any electrostatics yet). the AKG sounds too "live" or too "forward" or "in your face" to me; sounding "more like listening to speakers" is a good way to describe it.

    my musical tastes are pretty wide: i listen to jazz, fusion, big band, classic rock, folk, classical, electronic, latin/brazilian and audiobooks. i used to have the older (original?) version of Beyer DT990 and they really worked well for me for many years. i heard the HD600 at a CES show and decided immediately they would be next when my Beyers died. that time came and i went shopping. i listened to several models including the HD600, HD650, AKG701/702 and others. several people who's opinions i value about such things said "get the AKG's; you'll be happier". But from my tests, i wasn't. unfortunately, all this effort was made moot - during this process, i got married and my wife bought me the Sennheiser HD598 as a surprise for Christmas. After building a stronger amp (HD598 are low impedance), i find i prefer the HD598 over the AKG but they don't quite sound as good as the HD600 (or even my old Beyers if i trust my memory ).

    I'm hoping Sennheiser keeps making the HD600 because I will eventually get a pair. I'm one of those that even prefers the HD600 over the HD650. I have my hearing tested/measured periodically since I'm older (56) and for years have had a dip in both ears from about 1KHz to 5KHz. Plus, the "old age" roll-off starts kicking in about 15KHz now. I suspect my hearing significantly contributes to my sound preferences compared to my friends. I must admit I am often amused by some of the threads I read on DIYAudio and other groups that suggest some of the similarly elder members have high-end hearing comparable to bats; I'd really like to see their hearing measurement results

    Posted Yesterday at 08:19 PM by mlloyd1 mlloyd1 is offline
  2. Old Comment
    rjm's Avatar

    Supercapacitor b*ll*cks

    If the capacitors are in series then the capacitance is no longer the algebraic sum of the values printed on the can. Just as the "total resistance" of two 100 kohm resistors in parallel isn't 200 kohms.

    I suppose they can wiggle out of that by saying the capacitance reflects the physical parts count, and I doubt the intended market for those gadgets is savvy enough to appreciate the distinction anyway.
    Posted 25th February 2015 at 05:26 AM by rjm rjm is offline
  3. Old Comment
    abraxalito's Avatar

    Supercapacitor b*ll*cks

    Very good points. I was picturing a ripple waveform as I was reading your writing - this supercapacitor powered unit is just like a vastly slowed down version of a direct mains powered unit. The ripple voltage is still there - I wonder how much ripple they accept on their 24V rails? That's obviously rail noise and with 9 supercaps in series the impedance isn't particularly low.
    Posted 24th February 2015 at 04:24 AM by abraxalito abraxalito is online now
  4. Old Comment

    Supercapacitor b*ll*cks

    I sense some new math in the first comment here by Mr Johnson. He is correct in that 1A = 1C/s but he forgets that any old current can not be delivered into a load unless there is sufficient potential to do so. To state that 5A can drive a 4 ohm load to 50W is a bit misleading when not also stating that the potential must be maintained at or above a voltage equal to V = P/R. Assuming he is talking about clean peak power, then V = 50/4 or 12.5 Vpk. Now think about how the charge reaches the load - it starts in a capacitor bank and then goes through an amplifier with some efficiency before reaching the load. A capacitor discharges according to an exponential law - that is the voltage across the terminals falls exponentially as charge is removed.

    Because of the need to maintain a certain voltage to power the load, and because of the exponential decay of the capacitor's potential, it would seem that the duration that the isolated cap bank can support the load is much less than what one might think using Mr Johnson's argument. I would guess that the limiting factor is actually the voltage that the cap bank can support at any given instant that determined when the re-charging cycle must begin. Even when the average playback level is low, you need voltage headroom for short duration music transients if you want to claim "high fidelity" reproduction that is true to the source. Thus the caps must remain highly charged to retain a high potential that can serve the amplifier as needed by program demand.
    Posted 23rd February 2015 at 04:53 PM by CharlieLaub CharlieLaub is offline
  5. Old Comment
    rjm's Avatar

    Gustard H10 Headphone Amplifier

    I doubt it would make much of a difference replacing either the NE5532s or the OPA134s. Both are pretty solid choices.
    Posted 23rd February 2015 at 12:18 PM by rjm rjm is offline
  6. Old Comment

    Gustard H10 Headphone Amplifier

    Thanks for replying. My knowledge of all this is absolutely minimal. But that raises two questions, if you don't mind. First, would sticking the NE5532 in the balanced-to-single-ended conversion for the input XLR make a difference to the sound--assuming you would then use XLR imput?
    Second, can you see any easy ways of upgrading the H10, for example by replacing the OPA134s with better ones?
    Thanks again...
    Posted 23rd February 2015 at 08:59 AM by asaifa asaifa is offline
  7. Old Comment
    rjm's Avatar

    Gustard H10 Headphone Amplifier

    The NE5532 are dual op amps, they won't replace the main OPA134s, only the NE5532 already used in the balanced-to-single-ended conversion for the input XLR.
    Posted 22nd February 2015 at 11:32 PM by rjm rjm is offline
  8. Old Comment

    Gustard H10 Headphone Amplifier

    Hi. Thanks for writing down your impressions. I've been looking at the H10 for some time, as it is quite affordable. I have a pair of Dexa NE5532s which I used in an Eastern Electric Minimax Dac. But I sold the dac and would like to use the Dexa opamps elsewhere. Do you think it would be an improvement putting them in the H10?
    Posted 22nd February 2015 at 02:24 PM by asaifa asaifa is offline
  9. Old Comment
    rjm's Avatar

    Z-reg II improved simple Zener voltage regulator

    Food for thought. I'll look into it!
    Posted 22nd February 2015 at 01:32 PM by rjm rjm is offline
  10. Old Comment
    dimkasta's Avatar

    Z-reg II improved simple Zener voltage regulator

    You can also try a small film cap near the gate to eliminate higher frequency switching stuff

    Salas on his BiB for example is filtering his led reference with 0.22uF

    A gyrator is also an interesting idea used by Matrin from acoustica

    He uses it on the raw supply though to fix the high frequency limitations of the LM series, but it would be interesting to see it filtering the reference too...

    Using 3-pin regulators off-piste: part 2
    Posted 22nd February 2015 at 11:44 AM by dimkasta dimkasta is offline
  11. Old Comment
    6L6's Avatar

    Where I'm standing today, DIY F4's to begin soon.

    You need to use (8) 22,000uf caps per PSU board, not (4). Or (8) 15,000uf. Whatever get you to approximately 120,000uf or more per board.
    Posted 21st February 2015 at 03:59 PM by 6L6 6L6 is offline
  12. Old Comment

    Superregs for your line-level projects

    Hi Jan

    Thank you for sharing this great circuit.

    In your view is it suitable to provide the 12vdc I need to power my PicoPSU (DC to DC ATX) which is plugged into my audio PC? At the moment I use an old TTI bench supply to provide a low ripple/low noise 12v to the Pico PSU. The bench supply disply shows the computer is drawing about 1.2amps while playing music.

    Would I need to upgrade the capacitors and diodes to cope with the 18vdc input to give me 12v out?

    Is there a higher power alternative to the amp AD825 please? can't see one on Mouser or RS
    Posted 18th February 2015 at 11:05 AM by SteveHolt SteveHolt is offline
    Updated 18th February 2015 at 11:10 AM by SteveHolt
  13. Old Comment
    abraxalito's Avatar

    Supercapacitor b*ll*cks

    Right - so what problem is being solved here by having the two banks of supercaps and switching between them? I rather suspect its all down to marketing narrative - once a company has established its story (which for Red Wine was in a major part the isolation from mains power) then it can't go back on that. Even though sufficient isolation from mains power is possible without resorting to the complexities of supercap charging/switching.
    Posted 17th February 2015 at 12:27 AM by abraxalito abraxalito is online now
  14. Old Comment
    fas42's Avatar

    Supercapacitor b*ll*cks

    Hmmm, I've thought of trying something like this concept - the trick is to completely isolate the charging circuitry from the playback area - unless there is zero, audible cross interference there is no point ...

    The proof of the pudding is in the ... . Experiments should determine whether there is significant gain in SQ performance using this more complex approach, and whether that gain is worth the money. In my own high energy gainclone, there was no noticeable variation in the tonality while the amplifier was playing off "battery" power, having pulled the mains lead from the wall socket.

    So, solving problems? IME, there are numerous ways of doing "it" -whatever works, and/or floats your boat ...
    Posted 17th February 2015 at 12:00 AM by fas42 fas42 is online now
  15. Old Comment
    wlowes's Avatar

    2013 Holiday Projects - Ridding the system of resistor problems

    Hi Polaron
    Sorry I missed your comment. In my understanding there is absolutely no difference technically/sonically between the $350 assembled unit from Intact Audio and the AVC pair at $200. The assembled version would be very easy, and provides a second fine tuning control. I took th eless expensive route and wired it myself. Took me an afternoon to assemble and wire. I have never needed a finer step in volume than the basic 3db step provided.
    I expect your setup will be very good, but Dave Slagle will happily comment if your system is appropriate for an AVC.
    Posted 16th February 2015 at 06:52 PM by wlowes wlowes is offline
  16. Old Comment
    abraxalito's Avatar

    Supercapacitor b*ll*cks

    Yes I agree it would be a much fairer way to describe the array of supercaps to talk about charge. Or even to talk about energy storage. However it is rather common to flaunt uF in power supplies, meaningless as it is without knowing the working voltage.
    I can't imagine how an amp would be able to use the charge all the way down to 0V so I agree that the caps would only be useful over a relatively small proportion of their working voltage.
    Posted 16th February 2015 at 04:00 PM by abraxalito abraxalito is online now
  17. Old Comment

    Supercapacitor b*ll*cks

    Maybe the best way to describe it is to say the supercapacitors store a total of seventeen thousand Coulombs of charge.

    Since 1 ampere = 1 Coulomb per second, when you've got 17,000 Coulombs you can supply ten amperes DC for 1700 seconds. Let us send 5 amps DC to the Left channel and 5 amps DC to the Right channel. A little calculator exercise will show you that 5 amps DC will drive a 4 ohm loudspeaker to 50 watts RMS (and twice that for an 8 ohm speaker).

    The announced LIO amplifier stages are rated for only 25 watts, so these seem quite manageable.

    HOWEVER it would be dangerous/silly to discharge the supercapacitors all the way from 100% to 0%. Instead assume they discharge from 100% to 90% (giving up 1/10th of their total charge). Now they can supply ten amps DC for "only" 170 seconds before recharging commences.
    Posted 16th February 2015 at 03:00 PM by Mark Johnson Mark Johnson is offline
  18. Old Comment
    rjm's Avatar

    Gustard H10 Headphone Amplifier

    It's a push-pull output, so class AB in principle though its probably biased such that transition out of class A is extremely rare. The exact circuit is a bit of a mystery to me, with four output devices per channel, four smaller transistors, as well as some LEDs and diodes ... the buffer topology does not immediately jump out at me.

    Can't comment about the op amp bias. What you see in the photos is all I know about this amp. There's an unusual level of sophistication to the design compared the usual ebay stuff. I can't even find the rectifiers, let alone decode the voltage regulation! Its troubling resemblance to the Violectric V200 (reverse engineering or ... ?) is no doubt all part of the reason.
    Posted 16th February 2015 at 09:11 AM by rjm rjm is offline
    Updated 16th February 2015 at 09:13 AM by rjm
  19. Old Comment
    abraxalito's Avatar

    Gustard H10 Headphone Amplifier

    Impressive array of caps there - seems to have a loyal following over on Headfi. Is it a pure classA output stage? If so with the opamps I wonder if they remembered to bias them into classA too - if not that could be the reason it falls over with higher crest factors.
    Posted 16th February 2015 at 02:58 AM by abraxalito abraxalito is online now
  20. Old Comment
    wlowes's Avatar

    Why I DIY

    I totally relate to your thoughts. When I was yonger, I always wanted a good sound system. But I am thrifty. I had lugged around a consumer grade stereo which got only occasional use. about 10 years ago, I pulled the speakers out of storage and realized they needed refoaming. That is how it all started. Now I can thoroughly enjoy developing a project. When it finally comes to life, it is like a first born. I would not trade it for the most expensive audiophile device available. It is mine, and the fact that it makes great sound is just all the more rewarding.
    Posted 14th February 2015 at 05:05 PM by wlowes wlowes is offline
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