kevin gilmore

The new dynahi power supply seems simple enough. Most of the size is due to the electrolytics anyway. If you really want to use this as an integrated amp, a much more massive power supply is going to be required. And then the size is mostly capacitors and the transformer anyway. This thing actually works just fine on a completely unregulated power supply which is what i'm testing it on now, because i don't have a regulated supply that puts out 5 amps.

So it turns out that the lme49830 is pretty much a dynafet on a chip, with diamond buffers driving the fets. SO... combine with the semelab-tt lateral audio mosfets, and the result is something super sweet, and easy to build, about $50 in parts per channel. Combine 4 channels with my balanced preamp, and have one serious kickass thing guaranteed to drive anything, he6's and k1000's included. At about 2 orders of magnitude less distortion than that other thing. And more than 10 times the available output current. at... 20hz to 20khz... .1mw .05% thd (most of which is noise) 1mw .01% thd 100mw .005% thd 1w .0003% thd many watts <.0001% thd http://gilmore.chem....u/blackhole.jpg Works great at +/- 30 volt supplies, But also works all the way up to +/-100 volt supplies. 30 volt supplies highly recommended especially balanced, because lets face it, enough is enough. Suitable for driving say ten thousand pairs of sr-009 at the same time (400 volts peak to peak) A bit more work to do, but getting close now. 3.2 x 3.6 inches plus required external heatsinks.

Great. then post your impressions of the 3 amplifiers over there for the poor sap that evidently does not understand.

Alex told me he was a physics professor at a california university at CJ010. I had no reason not to believe him. But the current stuff certainly makes more sense given what he is doing, and i have a lot less respect for him now. Also makes sense because alex has said that he designs strictly with a voltmeter and does not have any of the standard test equipment one would expect a decent audio designer to have access to.

The sacd of dark side of the moon, as good as it is, should not be used as a reference disc. Wish you were here is much better, but still there are all sorts of flaws that are evident when you listen on good gear. All of the analog productions discs (verve et all) are way better for use as reference discs, as well as the recently recorded beethoven piano sonatas discs.

Worse, much worse. Alex is a senior tenured theoretical physist. You know... big bang, quantum mechanics, and string theory

Actually for the same amount of flux i think the r-core is both bigger (longer path) and therefore slightly heavier. But it is very close in any case. The primary to secondary isolation probably makes no real difference in this case.

Got an email back from toshiba (and subject to translation) the 2sc4686a part was introduced march of 2010 with a planned production run of at least 5 years. No plans to discontinue. So i don't know what is going on yet.

I can't seem to find the end of life date, but back order is 6 weeks, i suggest people buy them now.

justin just pointed out to me that at least according to the mouser website, the 2sc4686a part has been end of lifed by toshiba. This is not what i was told by toshiba, but who the fuck knows. People should put in lifetime buys now just in case. I just did.

The headphones are nominally 60 ohms. Most of those old classic amps had at most 16 ohm taps. So to get enough voltage to match the current needed, you have to bump the theoretical power. So say 5 watts into 16 ohms turns into the equivalent of 15 watts into 48 ohms. I have a couple of quad II's in the basement i should dig them up and see if they still work, they definitely had 16 ohm taps, maybe 32 ohms ?? (nah) The radford, i know nothing about. For those hooking up to MC240's and MC275's do it in 4 wire mode, or remember that the 4 ohm tap is actually ground, so you would tie the 2 x 4 ohm taps together and that is headphone ground, then use the 16 ohm taps. Otherwise the amp is going to get mighty pissed off.

OH boy was this not the way to handle things. I have given lil-knight over $1k for circuit boards. Got absolutely every single thing i ordered. So have many other people here.

The sun never sets on the Stax Mafia!

Looks similar to the krell master reference. Also an older boulder amplifier i think. I really do want to build a second T2, so if you can have more of those chassis made, i'm definitely interested.

The world seems to be going lower impedance which i think is a really good thing for noise. Rays darkstar and sr71B have a 1k input impedance.

Yes, DHT push pull is great. What would be even better is to find a way to get someone to wind an output transformer with the mcintosh cross coupled cathode winding. A pair of 300B's done that way would be a great headphone amp. Here is my opinion on power levels. The amp needs to be able to put 5 watts into 50 ohms. So on amps with 16 ohm taps, it needs to be at least a 15 watt amp. On amps with only 8 ohm taps, it needs to be 30. So an old tube dynaco if you can find one that works probably sounds very good. The atmasphere is in fact push pull OTL tube. scott... you know that sand and tubes is verboten

that would have to be on an amplifer to amplifier basis. Way too much trouble. you would have though that. But with a low impedance coil and a large magnet structure, the thing has quite a kick. blubliss wants me to find a push pull tube amp. I thought this would be easy, someone had to have a low power push pull tube amp for headphones. Evidently not so easy. The smallest of the atmaspheres might work, There is a cary that would probably work, and a vtl. All 3 of which have stupid pricing for what they are. i'm betting that classic old marantz and mcintosh tube amps are going to sound very nice, especially the mcintosh.

So i have birgir's pair of LCD2's here for extended listening while the transistors are on their way back from england. They sound so dramatically different on all the amps i have tried, And measurements show that these things generate signifant amounts of back EMF, and therefore require an amplifier with a very low output impedance to sound right. OTL tube amps, even the SP extreme perform very poorly on these headphones. The only single ended transformer based amp i have, also sounds pretty grim. Only push pull high bias amps seem to work right. And push pull tube amps also sound really good. Good enough that i will be buying my own pair on monday, and i'll skip the lcd3's for now and get lcd4's later. half an amp at reasonably loud listening levels has been measured with my hall probe. I think that tyll needs a high current buffer amp for his measuring system, because the built in amplifier really cannot drive these kind of headphones correctly. The waterfall and decay plots will change a bunch when done this way.

Yep, according to 6 moons, T amps. On batteries. The batteries are great for high current peaks, but are definitely not as quiet as a good quality regulated power supply. At least the stuff is built better than the rudistor crap, but definitely way overpriced. I've looked into this a bit more, and much of what is inside is actually built by someone else. Both attenuators used are from bentaudio, i recognize the single tube input board, and the T amp board also seems to be one of the standard vendors selling those boards for about $25. Looks like the only thing they actually make is the headphone only output which is one of the national semiconductor lower power gain clone style chips.

And here i thought it was "ERECTOSTATIC"

I can't find the schematic. Seriously. I must have left it at home. Will draw it up again and post soon. here is a fresh version http://gilmore.chem....u/protector.pdf For DC, it triggers on anything over +.5VDC and -.5 VDC Detect time is 75 milliseconds. For AC, at 20hz, it triggers on 5 VRMS.

oops, so i can't spell. I'll fix it later. Its not like its already etched into a front panel. We can adjust the comparator window as necessary, as well as the filter. Ceramic caps up to 4.7uf in that lead spacing i believe. Putting the thing in a small box with a female and male 4 pin xlr's on tails plus a cheap wall brick should take care of those pesky massively overpowered things from my friend in skokie that seems unable to comprehend DC servo's.

Yep, works fine with the dual coil latching 5 volt versions.

This has been needed for a while. For those with problematic DAC's that put out a bit of DC, and balanced headphone amplifiers happy to amplify said DC and produce differential DC on the output... http://gilmore.chem.northwestern.edu/protector.jpg This is the one case where ti kan's protection board does not work, unless you want to use 2 of them.

The test setup already does distortion levels way lower than my 30+ year old measurement system. That is not the point, i can take an lm741 and put oodles of feedback around it and measure .001%. Still sounds like crap. Its the rise time, symetrical slew rates, overshoot, and all those other things that make something sound good or not. These newer chips with real complementary silicon processses really do sound great. The quality of the resistors in the audio path is going to need to be of very high quality. I see that Susumu .1% resistors are now available cheap, i'm going to have to listen to those. To maintain the CMRR on the input stage is going to require very close matching of the resistors. Probably a couple of months away from circuit boards. Then again, maybe sooner. Lil-knight is going to have to do the boards, locally, the prices are way out of line, and the sales tax is also way out of line. As far as i know there are no better board mount xlr connectors made, regardless of price. Everyone uses the neutrik.