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justin

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Posts posted by justin

  3. The Headcase Stax thread

    in Headphones

    Posted · Edited by justin

    1 hour ago, Kung said:

    damn, 2400x the gain, that must be loud enough to explode... 

    there are audiophiles who judge the power of the amplifier by the position of the potentiometer knob, i guess ray samuels should have a good knowledge of this.

    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

  4. The Headcase Stax thread

    in Headphones

    Posted · Edited by justin

    On 4/14/2023 at 11:46 PM, Kung said:

    ::)Ray samuels the old friend of stax mafia just released a new amplifier B-21, the electrostatic part claimed 1800Vpp voltage swing with 200mA continuous current output performance just shocked me. . . Reminds me of the horribly weak output performance of the A10 he designed before, this new amp is also questionable...

     

    B21.jpg

    B211.jpg

    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..

    spacer.png

    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

    • Like 1
    • Thanks 1
    • Haha 8

  7. Viva Egoista STX

    in Headphone Amplification

    Posted

    On 4/2/2023 at 12:11 PM, udurbalanced said:

    I don't get the fuss. It takes exceptional skill to put a circuit components in a box, throw it off a cliff and then solder everything to make a working amp.  They're succeeding where Mikhail failed, if you ask me.

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

  9. and now for something completely different part 3

    in Do It Yourself

    Posted · Edited by justin

    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+

    IMG_0363.jpeg

     

    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.

    • Like 19
    • Thanks 1

  10. Topping EHA-5

    in Headphone Amplification

    Posted · Edited by justin

    3 hours ago, Timb5881 said:

    Yes the older Stax amps do offer a way into the Stax world.  But be weary that many have parts that are no longer available.  I have a

    Buyer beware on older Stax amps.  Many have parts that are no longer available.  I have a SRM 1/ MK2 that I tried to refurbish but some of the transistors are not to be found at any price.   I know the Stax SRM1 is loaded with obsolete discontinued parts.     If you were to look at this point of view, Topping at least has modern and available parts.  Design wise the topping is iffy at best.

    Maybe Birger and Mr Gilmore can give us a list of Stax amps that have replacement parts issues so others can make better informed decisions.

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

    • Thanks 1

  12. Topping EHA-5

    in Headphone Amplification

    Posted · Edited by justin

    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.

    • Like 1
    • Sad 2

  13. Dyson Zones

    in Headphones

    Posted

    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

  15. Yes, no, may be? Who remembers this?

    in Do It Yourself

    Posted · Edited by justin

    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

     

    800E8ABE-5E8A-4EFB-90EB-C744327A4902.jpeg
     

     

    EAFA35CD-CDCE-4B0F-B028-23224D0535A8.jpeg

    • Like 9

  18. Yes, no, may be? Who remembers this?

    in Do It Yourself

    Posted · Edited by justin

    14 minutes ago, jose said:

    @justin bad boy.... I've been looking for the schematic and the sand for an hour 😁

    I couldn't find the schematic (KGDT only) but I find it: 

    Kevin sayd: 

    schematics for mig here.

    http://gilmore.chem.northwestern.edu/kgdt1.gif
    http://gilmore.chem.northwestern.edu/kgdt2.gif


    mig amp can be built balanced or unbalanced, uses grounded
    grid 6c33 output tube and solid state current source.
    (4 tubes balanced)

    mig2 amp can be built balanced or unbalanced uses grounded
    grid 6c33 output tube with a 6c33 as the current source.
    (8 tubes balanced)

     

     

    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

    kgdt1.gif

    kgdt2.gif

    • Like 1

  20. Megatron Electrostatic Headphone Amplifier

    in Do It Yourself

    Posted

    no RK50 option?

    On 3/25/2023 at 5:44 AM, kevin gilmore said:

    that section runs on 300 volts.  ksa1156 is in stock at mouser now. would work fine. i think the pinout is backwards from 2sa1968 so just rotate it around.

    the emission labs tube with the octal base and the center tap filament would make things much easier but would limit the amp to those tubes. so its the standard 4 pin socket.

    that is for the EML-only version 🥰

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