kevin gilmore

the dht version is for the emission labs directly heated triodes. Expensive and requires 4 separate 5v filament windings on the transformer.

power supply is version 1.8 copyright 2015 however it shows both boards the same, and that is definitely not the case. although you can do it that way, but then you need a grlv power supply in addition one board has the bias voltage, the other board has the low voltage regulators amp is version .6 copyright 2015 I think this is the latest I released. There is a .61 version which I may or may not have released, don't know the differences

that one is indeed 3 layers, extra complete ground layer in the middle. forgot about that one.

its a 2 layer board. not sure why it is being detected as 3 layers

easy, low cost, no adjustments, only hv supplies etc.

thermal grease lasts forever. I have a jar with original Newark part number on it, and its 50 years old. Still good. the stuff contains aluminum oxide or silicon oxide, or various other compounds in silicone and for voltages less than about 2.5kv its an insulator. Although it can have more capacitance than you might think.

v- is actually -370v and vref3 is -350v take a closer look at the original schematic

history lesson (unless birgir says otherwise) As far as I can tell the first stax amplifier to use differential cascode circuit is the srm-1 first introduced in 1979 long before hifiman was even a company

The srm-001 is an opamp driving a fet that drives a transistor (cascode) into a load resistor and is cap coupled to the output. (cascode differential) The jade2 is an opamp driving a transistor that drives a mosfet (cascode) into a load resistor and is cap coupled to the output. The calculation of output capacitance is flat out wrong as the middle of the cascode is AC ground. (cascode differential) Just about identical. Obviously the jade2 consumes a bunch more power and puts out a bunch more power. I own 2 hifiman products. Both are built like shit. I'm unlikely to buy hifiman products ever again.

uberamp2 in single ended form. then you don't need the resistor box.

The circuit is more like the srm-001 blown up by a bunch. So opamps input, solid state version of grounded grid output stage, resistor loaded, and capacitor coupled output. Positively ancient design by any standard. Did not even replace the power resistors with current sources. Saying that the output capacitance is that low because the two devices are in series clearly shows no understanding on how that design works. And the series output inductors are not a great idea either. The headphones may be decent, I don't know because I have not heard them, but there are so many decent headphone amps out there that buying the hifiman version seems like a waste of money.

2 grhv, 2 grlv78xx,2 grlv79xx, 1 main board, 1 mini t2 please

it may have something to do with the minimum voltage. But I have not tested it.

someone needs to check this, works as single rectifier with center tapped transformer, or a pair with dual secondaries. Up to 72vdc, perfect for GRLV caps are 100v rated, 1uf is 0805 size, 10uf is 2220 size I can certainly do a bigger version with different fets for higher currents and lower voltages. .9 x 1.1 inches syncrectifier.zip

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.