kevin gilmore

going to make it a replacement for the 4 pin diode bridge, should fit in all boards with that pinout. something like this

coming soon, synchronous diode bridge using lt4320 and power fets lower dropout voltage, much less switching noise

1) go and find complementary parts that work at 900v that are not obsolete 2) the load is more than you think. up to 20ma at 20khz 3) protect the diaphram 4) takes minutes to charge, quality of resistor is meaningless 5) 717 and 727 definitely have emitter follower output stages with current sinks.

the cpu board has a known issue where the display goes blank. only the guy in Greece seems to know how to fix them. The one in the 2465a is different and does not seem to ever die.

I have a 2465A which still works fine. I have a 2465B which I had to send the cpu board to Greece to get it fixed, it works fine. I also have a 2467B which had the same problem with the cpu board. All 3 still work fine. I did get a tek 1GHZ BW digital scope which I use a lot now, and a 300mhz rigol which is much more portable, and I use that a bit too. The next time the 2465's die, I will retire them.

easiest to print out the file 1:1 from the gerbers. If your printer is exact, and virtually all laser printers are, this is the most accurate way. then center punch, drill, then tap.

long time ago there was a Yamaha integrated amp that had an A/AB switch. like about 1978. really nice thing, would make a perfect headphone amp if you can find one that still works. in fact the CFA amp is a A/B amp with the bias between 150 and 200ma. These days that kind of bias into just about any headphone results in pure class A operation. The uberamp2 is also a A/B amp with the bias between 2 and 3 amperes. about 100 watts into 8 ohms balanced.

a number of lab power supplies have an adjustable current limit, so one of those set appropriately would be identical to the smps supply without the extra noise. but it would be easier and a bit cheaper to build a diy version with grlv and grhv supplies, a real transformer, in a standard heatsink chassis, with the outputs transistors on the heatsinks etc. then it would last more than 3 years. Those smps supplies when they get old, the main cap dries out, and usually bad things happen, especially to the output voltage.

Unlikely to be a transient but only Alex knows at this point. Something with the clever way the filament and high voltage power supplies start up. You would think that rudimentary real world testing would have found this before a batch of them were made. then again on the liquid carbon version 1, using balanced and unbalanced headphones at the same time, and the amp blows up, something else that should have been caught before a large batch were made.

so here is a reason not to buy the LP. if you turn off the switching power supply (or a power hit, or unplugging it) with the amplifier power switch on, a mosfet in the amplifier power supply fries. another of the many reasons why rail splitter power supplies are a bad idea.

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