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Old 29th August 2006, 12:01 PM   #51
Gorilla is offline Gorilla  United Kingdom
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I like the aforemensioned idea of using a logic buffer/driver as the output stage. If you look at a chip such as the 74LCX244 or 74LCX16244, octal buffers capable of sourcing/sinking 24mA per pin. Parallel a few pins and you have decent current drive.

Furthermore, if you use a comparator with complementary outputs you could easily form a full bridge, giving benifits of both not needing a split supply, and doubling your output swing from a lower battery supply voltage.

The only cavet on my mind, is that a logic IC isn't designed for such operation and may not perform as expected.


In my mind, simply and cheap. Just my two cents however.
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Old 29th August 2006, 05:40 PM   #52
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Default Power?

For driving headphones cleanly you don't need much power. In fact generally higher power means higher noise so is counterproductive. An amp capable of a couple of watts into 8 ohms is overkill. Doing a bridge design means you must modify the phones for separate right and left circuits to disconnect the common ground. Using a single ended design you could boost the voltage a bit to get the same effect and not have to deal with the ground issue or greatly increased noise.
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Old 14th September 2006, 01:07 AM   #53
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Default Re: UCD type headphone amplifier

Quote:
Originally posted by BWRX
This is a continuation of the idea that originally formed in this thread: http://www.diyaudio.com/forums/showt...463#post945463

After a little thought, the design could be quite simple. The high side would have a pnp connected to the rail and the inductor, its base connected to the collector of an npn through a resistor. The emitter of the npn would be grounded, and the comparator would drive the base through a resistor. Mirror that for low side (using npn's instead of pnp's and pnp's instead of npn's) and it should be very simple to build. The output stage parts would include 2 pnp's, 2 npn's, and 4 resistors. The comparator would be an IC, and the feedback loop/input parts would include 3 resistors and a capacitor. That could be a bare bones implementation. I'll try to draw up a schematic and maybe come up with some part values a little later tonight.

Everyone feel free to list what they'd like to see from a class d headphone amp!

I would love to see enough juice to drive 300ohm cans, balanced inputs with a balanced output to the cans, no shared ground.
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Old 14th September 2006, 01:07 AM   #54
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Quote:
Originally posted by mourip


I built a UCD180-AD amp specifically to power my AKG K1000 headphones after having such good luck with my Audiodigit 2020 amp. The Audiodigit was powered by SLA batteries. It was absolutely silent and had amazing detail.

The UCD is better. It has a much more relaxed upper end, way better bass, and there is no comparison in complex choral or orchestral passages. Of course the UCD costs 4 times what the Tripath 2020 did to build and has 180 watts instead of 8.

I tried my Sennheiser HD650's with both amps and was disappointed but mainly because the K1000s are so much better sounding to begin with.

AKG K1000s with the UCD are the best sound I have gotten so far as a primarily headphone user. My front end is "PC Audio" (Foobar and iTunes) to Scott Nixon USB DAC to Sowter TVA to Hypex UCD180-AD.

I have the T-amp for sale on EBAY right now and am keeping the UCD.

Hope this helps...



This is what I am interested in. My question now would be whether or not the HD650 sounded great and your K1000s are that much nicer sounding, or did that margin widen when driven by the UcD? I mean, if the HD650 are say, 80% as satifying on a normal head amp as the K1000, would you say that they are 80% as good on the UcD? Also, what did you use as a power supply and what was the rail voltage? Did you use two amp modules to run a balanced signal to your cans? How many watts do you think it was putting out at 8ohms?

Got any pictures to send me?
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Old 14th September 2006, 01:07 AM   #55
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Judging by the length of this thread, my lack of knowledge about electronic design, and the debate of whether or not it is possible, I would love to take a poll of who wants a UcD headphone amp? Then, after generating enough interest, Jan from Hypex may help us out and design one for us. This would end the debate and allow me to get my hands on one instead of just reading about it and not understanding half of what is being said! Those of you here who are religious headphone guys should pipe up about the belief that headphones do not need lots of power. I have read many posts on headfi about people driving Stax and AKG cans off of home amps including Nuforce switching amps and had amazing succes! What I want is not to have to go out and buy new cans just to do it. Senn HD650(and its fore fathers) are arguably the most widely used high end can in the world so the design should keep that in mind. My previous amp had 2 watts/ch of SET power at 30ohms and that was just enough to drive the HD650 from some sources.

Maybe I am barking up the wrong tree, but one dude here is already running his AKG K1000's off of a UcD180 amp with great success. Why not take that ball and run with it. I know most of you guys love to tinker, but I would much rather Hypex tinker for me and I put it together. Opinions?
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Old 14th September 2006, 01:40 AM   #56
Tim__x is offline Tim__x  Canada
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"...from some sources."

That implies that the amp was more than fully capable with other sources. That means your problem was not power, but gain. Unless your amp is clipping, you have enough power. If it is not loud enough, and it isn't clipping, that means you need more gain somewhere in the signal chain.
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Old 16th September 2006, 02:23 AM   #57
mourip is offline mourip  United States
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Quote:
Originally posted by khundude2012

This is what I am interested in. My question now would be whether or not the HD650 sounded great and your K1000s are that much nicer sounding, or did that margin widen when driven by the UcD? I mean, if the HD650 are say, 80% as satifying on a normal head amp as the K1000, would you say that they are 80% as good on the UcD? Also, what did you use as a power supply and what was the rail voltage? Did you use two amp modules to run a balanced signal to your cans? How many watts do you think it was putting out at 8ohms?

Got any pictures to send me?
I think that it might boil down to comparing apples and oranges. I use the HD650s with my gainclone amp for watching DVDs and love them. Nice full clear satifying sound. When I have used the K1000s with the Gainclone amp I did not like it. Ironically, with the UCD the HD650s sound muffled compared to the clear and wonderfully open K1000s.

Using the K1000s with the UCD is basically the best sound I have gotten so far in headphone audio. The detail is remarkable with good bass and a very balanced tonal presentation. If I were to search for any improvement at all it would be to tilt the sound a bit toward the "romantic" side. I would probably do this by adding a tube buffer after the DAC however I am concerned about loosing detail. Right now I am just enjoying the music. Might try the buffer this winter.

I would say that if I had never heard the K1000s I might be happy with the HD650s but for me they just did not seem to be a good fit with my UCD. I love them with the Gainclone.

Sorry I have not taken any photos yet. Might try this weekend...

On another note. I have never understood why folks are concerned about driving phones from a high(er) powered amp. The phones will only draw the power they need. You will never be putting full power into the phones. I think that many good choices for headphone listening are overlooked because of this odd idea off "overpowering" phones. My two cents :-)

Best,

Paul
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