kevin gilmore

a number of people are complaining that there is no gain switch and the default gain is too high. kind of what you would expect from a current mirror feeding a tube. evidently its dc coupled but no pictures good enough to reverse engineer. If you go by the price of the cth x 2, this should be about $450 max.

lets see jds atom $99 opamp and output buffer, lots of feedback, dual power supply, probably the lowest thd of the bunch. made in usa schiit magni3 $99 discrete current feedback amp, minimal feedback, dual power supply, probably the highest thd of the bunch. made in usa monoprice liquid spark $99.99 voltage feedback amp, fair bit of feedback, rail splitter power supply, in the middle for thd.made in china sounds like a big pile of same same

yep, pretty much that schematic. pull up resistor is 1 meg. false advertising, shows a rca to mini, not supplied, shows 1/4 jack not supplied. comes with usb cable. bias resistor is 20 meg. power supply is fully regulated, something the sr-001 was certainly not.output stage bias is 200 microamps. I think that this needs a lot more input voltage than it should. also no volume control, so designed to hook to something with a volume knob. made in Taiwan. no names anywhere. after a few hours of warmup, still sounds like absolute crap. No way is this worth $700. or the $1k+ the guy on ebay is selling it for.

it has arrived, going to wait for it to warm up before listening N1,N2,N3,N4 are labeled XG (2sk209) q1,q2,q3,q4 are labeled lkw (pmbta45) opamps are jrc401f single high voltage of +440V. opamps get +/-17 this is very similar to the original stax sr-001 amp

so it turns out this one is a bit different than the rest of them. Input is 2sk2145 dual n-channel jfet, driven by current mirror on top, and current sink on bottom. Definitely a voltage feedback amp, lots of feedback. liquid gold, liquid carbon,massdrop liquid carbon, massdrop cth are all current feedback amplifiers.

If there is a diaphram arc due to very large excursion, the extra stored energy will cause damage to the diaphram

its like that monster 2 box singlepower thing I have. keep the case and front panel, and gut the insides.

cavalli liquid carbon massdrop version rail splitter cth and spark are similar railsplitter.PDF

you use either of the 2 references not both, and you have to adjust the resistor string for desired voltage jp1 jumpers pin 8 of ic2 to ground. definitely not for the lt1021 or ref01/02.

ic2 is replacement for ic1, ref01,ref02,lt1021 etc lps200.PDF

this is already very similar to the grlv. missing the double noise inverting current source, but that is about it. ic2 is an optional and higher quality alternate reference.

these headphones stopped by in Chicago on their way to Iceland, I listened for a couple of hours. My initial comments was that they were very sterile, but really I think it was the complete lack of imaging that is the problem. removing the foam probably fixed a bunch of that. The stax plug is a major fuckup. And I don't see why. Everyone else including stax,hifiman,kingsound,chinsettawong,birgir and Justin are capable of making plugs that are the right dimensions, no reason why this has to be a piece of crap. Yes they are about 6db less efficient. And the case is some kind stupid. I did not measure the capacitance of the cable, but i'm going to bet that its twice that of the stax made cables. birgir will hopefully do that. Next up the monoprice things once they actually start shipping.

Mismatched very high cacitance vishay siliconix output mosfets. And ground splitter. Otherwise identical current feedback amplifier same as liquid gold,liquid carbon,Cth, liquid platinum etc. at least it's better assembled than schiit.

that was ray's darkstar amp. the blackhole is something different. the blackhole uses a national semiconductor driver chip lme49830 and a pair of alf16P/alf16N semisouth fets for the outputs. You can probably substitute something else for those parts, including bipolars, as the board has options for that too, but I never tested that way. the darkstar sounds absolutely miserable, and these days has stupidly large voltage swings guaranteed to set just about anything on fire. the blackhole is suitable as a small speaker amp.

The company that made the output transistors went out of business

The problem with the D10 is that the power supply voltages are +/-175v so it clips pretty easy into standard sized headphones. The shure is very nice but power supply voltages are +/-200. Which works great on the supplied earbuds but would have trouble with standard sized headphones.

something screams kingsound to me for both the amp and the headphones. built in battery pack, usb charging, 1/8 input jack.

does not look like a stax plug to me, it has a shield around it. definitely really cheap for headphones and amplifier.

guess you did not look at the schematics. i'm talking about the current sources at the top of the gain stage before the output stage. main difference between 717 and 727 was 2sa1968 current sources (and local vs global feedback) srm353, T8000,D50 are back to being all resistors. and the german copy of the srm323 also uses resistors because of the 400v power supplies.

The 323 had a p-channel jfet as the input, +/-350v power supplies, 2sa1968 as the current source for the drivers etc. The 353 is a srm717 with all of the extra transistors removed. Very similar to kgss. D50 is identical to 353 running at slightly lower power and lower voltage. Current source is resistors on both. T8000 also uses resistors for the current source. seems that stax has run out of 2sa1968. d10 uses apex opamps with a power supply of +/-175, not great for large voltage swings. stax may be forced into using parts in the future that it does not want to use for some reason.

probably not worth making a balanced version, the output impedance is not super low.

sure

Mikhail rebuilt an original with black gates. Probably not possible these days. A few were the wrong voltage.

in theory with appropriate adapters or the right circuit board layout it would work. Lots more filament power. Lots more heat.

Yep that is the idea