justin

as Al would probably say, better sooner than later

First 2 chassis just arrived. Getting it tested!

the flip side is you lose usable range on the volume control and add noise floor, which could still be below the threshold of audibility with e-stats. adding pre-amps in front of e-stat amps, especially with gain switches, may become more of a thing could even have multiple inputs on the back -- ones that go through the vol ctrl/pre-amp and ones that are a bypass direct to the e-stat amp @ full volume

I tried the amp @ CanJam and thought, hmm wait a minute, the knob is only at 11 and I'm listening THIS LOUD to STAX? That's when I realized.. the gain is ~2400x, which is the highest I have heard of for an electrostatic amp (STAX amps typically 500x to 1000x) but makes perfect sense for demonstrations in a loud room. I changed the gain tube in the Grand Cayman (720x gain) from 12SN7 to 12SL7, which did the trick But that was the end of the show, so...next time

Its just more heat

Has anyone heard from mikhail or rudistor lately? Possibly a collaborative effort?

Yes

Been working on this for a looong time. CFA3 from scratch mixed smd/thru-hole design. Currently assembled with NOS Toshiba 2SC3381/2SA1349 inputs, NOS MPSW TO-92L thru-hole transistors and bcxxx for the smd. Power consumption 75W no fan. Linear PSU with 20,000uf/63V filter capacitance — custom golden reference regulators. Final dimensions are 12x9x4.5” / 22lb+ the motorized 48 step attenuator w/ remote and display was a last minute addition. definitely interested in finding out the feedback for that, but would want it built backwards for a final design, I think.

I bet I have the parts. they are probably available through head-case

soon or already have

This amp is already costing us money ...but it's not what you think. People are buying entry level STAX headphones, thinking they've got a hot new affordable amp to use them with. Then it turns out to be a piece of garbage and we get a returned headphone to deal with. My recommendation would be to look for a used STAX amp in a similar price range. They work great for many decades.

sadly the amount of people who search for these things, compared to every other high-end headphone combined, is huge had several hundred clicks on google ads before blocking the keywords

this is why it's basically pointless to advertise specs anymore

Here is 1 channel of a blue hawaii running on +/-100v instead of +/-400v, with a single 6as7 dual triode for balanced output instead of a pair of EL34. The tube current sources have been increased from 20mA to 75mA, resulting in a grid voltage of about -30 or similar to the original design Feedback resistors reduced to drop gain from 500-1000x to about 20x into a high impedance load i tested 1khz/50Vpp out at .008% thd in order to meet "today's standard" of 15W into 50 ohms balanced, I'm estimating 16x 6AS7G tubes per amp?? Sennheisers would work nicely with a baby blue Hawaii but IDK of any protection circuit that could be trusted to run no transformer or capacitor coupling into a dynamic or planar headphone!! That's why I think this may be a better project for the purpose of phase splitting/inversion, voltage gain, and buffer driver. For example, Kevin's 'tube input unbal/bal' board with the 6922 is basically the first 2 stages of all of the SS/Hybrid e-stat designs at lower voltage but a 6922 itself can't do the job completely if the job is to get to a low distortion 100Vpp balanced output to feed Uber-buffers to get the 15W into 50-ohms but you could use this baby BH type design, such as this with a single 6AS7 per channel or maybe 2x with the sections paralleled for more power, if wanting to have the ability to drive "Hi-Z" headphones directly with a very very good protection circuit, or maybe more realistically, a large film cap

I can send you some or try this? http://www.exicon.info/PDFs/ecx10p20.pdf

grind size

a couple mistakes that I know of in the output stage: the pot is 100 to 1K the CCS transistors must be paralleled as 30W from a single TO-220 is a bad idea

Colors Sovietized for effect * this should be in DIY forum

no RK50 option? that is for the EML-only version 🥰

happy birthday!

Kevin is now working on a new amp that uses 2 car batteries and a coat hanger as the load

I found a Grado HP-2 and now I wonder if anyone would want an updated SHA-1 😄 but also, could it be considered an update if it DID NOT use the tube filament as a load??

it was great!