kevin gilmore

So a person accused me of faking my scope picture, because it had to be my signal generator. And that the amp performed better at the higher gain setting. I completely disagree. Q15 has no emitter resistor and the resulting gain of just this transistor is 30db. which makes the miller capacitance absolutely huge. which is why you see two different slew rates. the first bit is due to the output amp (everything left of r12 which is a diamond buffer driving a pair of current mirrors driving another diamond buffer). The second bit is due to Q15. edit: shenzen audio is now selling these things brand new in the box on ebay for $50 off. soon it will be $100 off.

acually that is 10 boards total for 2 balanced channels.

done.

nope, you cannot use this. reverse bias and the diaphram accumulates all the dust particles. a month later and your headphones are trash.

its easier to do the board, then let the software turn it back into a schematic update: should be final schematic. that is a 3 pole (18db) low pass filter at 18khz. part of schematic now. nfca3.PDF

sure, +/-24v at 5 amps each rail balanced drive large heatsinks custom hand wound bifilar transformer with a really large cross section to keep the flux as low as possible and magic hybrid core ferrite materials. $$$

success soon yep, 39 transistors including 2 dual matched npn.

so you say you should be able to measure why it sounds like it does... first 2 are 1khz into 50 ohm non-inductive load. notice that the rise time and fall time are not identical. also notice severe slew rate limiting in both directions and kink on the positive slope. 3rd picture is 10khz. kind of what you would expect from an amplifier with an open loop gain of around 120db and a group delay of 10us or more. i don't have the transformers, but i'll bet it looks even worse driving that transformer. pretty sure the a90d will perform exactly the same. edit: see pictures in next post. definitely same as a90d

So, after a few hours in my favorite combination of methylene chloride, acetone, toluene, benzene, and 2 other magic ingredients (basically miller-stephenson ms111 only way cheaper) Warning kids: don't try this at home. highly flammable, highly toxic, low flash point... Let the professional morons do this the eha5 discrete module in the process of giving up its secrets. every single part of the eha5 is a massive pile of crap. it takes a whole room full of highly competent engineers to produce something this fucked up. i did take the other module, hooked it up to a bench supply and hd800 headphones and got a good listen. wow is this bad. proof that obviously the lowest distortion possible in amir's s/n test is the one and only measurement that they think matters. the rest of the specs, not even close. for those that don't know, the external power brick is a single 15v switching supply at 3 amps. internally it makes -15 from the +15. except for the fact that the -15 supply seems limited to about 750ma, and it runs 4 amps from this. So maybe if you are lucky you get about 175ma max current per amplifier. No way this is enough to drive those crap transformers. transistors are 2L, G1 and the dual is k4r

the phase is going to mess with the feedback in a serious way. going to be very tricky to get right. and then there is the problem of disconnecting the headphones with audio playing. might turn into a high power oscillator.lots of magic smoke.

worse than expected. would like to see the lundhall transformer.

+/-24v is recommended mininum for lowest distortion

first make sure the bertan is positive voltage output!!!!. because they make both. edit, because its a 24vdc input. the chassis of the power supply needs to be wired to ac input ground. make sure the bertan ground goes the center tap of the transformers.

you definitely want to use the lundahl transformers, they are going to be better than anything else you can buy.

pic?

actually by increasing the gain on the apex part you seriously compromise the high frequency response and increase distortion. which may be intentional.

absolutely not. topping has potted modules including the bias module that are not available as spare parts. topping has a custom switching supply that may not easily be substituted. every one of these is likely to be dead in less than 5 years. where 40 year old stax amps continue to function even though all the silicon is obsolete. topping is flavor of the month throw away garbage.

2 part epoy glue should fix that.

add on external module. much better idea. don't want to void the warranty.

only 2 with dead bias supplys that i am aware of. both died in less than 1 hour.

fact is that the warwick headphones are single ended and not stax compatible. basically a beveridge speaker done by someone with no brain. this and the high end sennheiser are proprietary technology.

in other news, significant amounts of topping la90discretes are overheating and burning up. the eha5 is based in part of the la90d. so expect those to be burning up soon.

actually a krell master reference pair of monoblocks will drive any headphone electrostatic or dynamic. just need to add a bias supply. 800 volts peak to peak.

i'm sure ray would be happy to sell you one of his new amps, only $10k.

there are a few units with the tube front end that have been built. less than 5 i think. boosting the front end high voltage will increase the power in the current mirror that follows the tube. so you might have to change some of those parts.