The Stax Thread III

[Gradostax fan]

its the 10th anniversary edition of the Lambda Pro, circa 1982.

Worth a try? Its on ebay for USD600.

 

[Kiats]

Worth a try? Its on ebay for USD600.

a bit on the high side.

check this one out: https://buyee.jp/item/yahoo/auction/u1141641473

 

[bobkatz]

Progress report on terminating the 15 watt transformer. I got some 5k 100 watt resistors from Digikey. These are designed to go on heatsinks. But jeez, they get VERY hot with sine wave testing. I burned one out (down to about 300 ohms) with testing at "only" about 500 volts RMS at 1 kHz sine --- which is 50 watts. So if you are going to try linearizing a transformer, prepare to find some BIG ass resistors.

Here are some results, very very promising, with the 5k. I'm assuming that I will never heat up these resistors too much in normal musical playback. The square wave overshoot is slightly improved with the 5k load. Frequency response is greatly improved (flatter) at the high end, low frequency response remains the same: Response is 1 dB down at about 15 Hz, 0.3 dB down at 20 Hz, 0.1 dB up at 20 kHz, and instead of rising above 20k it rolls off pretty sharply at about 40 kHz.

Harmonic distortion (THD without noise) at 1 kHz at 100 volts is 0.002%.

 

[bobkatz]

Good point about the lack of overvoltage protection in these modules. What would be a good overvoltage protection circuit for 580 V DC? If anyone has one I'd be grateful. Thanks.

Bump. If anyone has a 600 V overvoltage protection circuit for bias I would love to see it.

 

[bobkatz]

Progress report on terminating the 15 watt transformer. I got some 5k 100 watt resistors from Digikey. These are designed to go on heatsinks. But jeez, they get VERY hot with sine wave testing. I burned one out (down to about 300 ohms) with testing at "only" about 500 volts RMS at 1 kHz sine --- which is 50 watts. So if you are going to try linearizing a transformer, prepare to find some BIG ass resistors.

Here are some results, very very promising, with the 5k. I'm assuming that I will never heat up these resistors too much in normal musical playback. The square wave overshoot is slightly improved with the 5k load. Frequency response is greatly improved (flatter) at the high end, low frequency response remains the same: Response is 1 dB down at about 15 Hz, 0.3 dB down at 20 Hz, 0.1 dB up at 20 kHz, and instead of rising above 20k it rolls off pretty sharply at about 40 kHz.

Harmonic distortion (THD without noise) at 1 kHz at 100 volts is 0.002%.

Now for the sonics! With the 5k load, the sound is much less "transformery" and more transparent. It's a win win for me, the transformer has begun to disappear. Most people would not be able to tell anymore that this is a transforrmer-based energizer. This thing can be built with $500 in parts! And sounds fantastic, it clips near 1000 V RMS at 1 kHz so it has tremendous headroom. And definitely does not sound like a wimpy energizer nor does it sound harsh.

 

[etc6849]

Did you see this video by @aokman ?:


I haven't built it yet, but the parts list and schematic are in the video.

Bump. If anyone has a 600 V overvoltage protection circuit for bias I would love to see it.

 

[kevin gilmore]

i'm coming up with something more complicated, but for the moment a zener string of 600v in series with a 10k resistor tied to the bias after the 5M resistor should work fine.

 

[Svperstar]

i'm coming up with something more complicated, but for the moment a zener string of 600v in series with a 10k resistor tied to the bias after the 5M resistor should work fine.

Kevin, is there a single estat on the market that the KGSSHV (non-Carbon) won't drive? Just curious of your opinion since its your design.

 

[kevin gilmore]

if you are buying used then buy whatever you can afford.

if you are buying new then why would you buy something that is filled with obsolete parts.
the carbon is better and if you are building yourself, cheaper. and higher output stage current.

the carbon is class A. the 2 available (or soon to be) cfa electrostat amps are class AB. definitely slightly different sound.

 

[Svperstar]

if you are buying used then buy whatever you can afford.

if you are buying new then why would you buy something that is filled with obsolete parts.

Its not for me. Someone reached out to me in DMs asking to buy either my Blue Hawaii or Carbon. I pointed out there is a KGSSHV for sale at a solid price and he replied he was afraid the KGSSHV "didn't have as much power" as the BH/Carbon. Hence me asking if there is a single estat on the market that isn't properly driven by the KGSSHV.

 

[kevin gilmore]

who built it. what are the power supply rail voltages. how much output stage current. how loud does the person listen.....

here is one for sure that NONE of my amps can drive without modifications.
https://headphones.com/products/warwick-acoustics-aperio-open-box?variant=40369799364679
the sennheiser he1 is another.
and the jeklin is problematic.

 

[Aspirant Audiophile]

who built it. what are the power supply rail voltages. how much output stage current. how loud does the person listen.....

here is one for sure that NONE of my amps can drive without modifications.
https://headphones.com/products/warwick-acoustics-aperio-open-box?variant=40369799364679
the sennheiser he1 is another.
and the jeklin is problematic.

...was really hoping you'd be Jecklin-friendly...Warwick does an amazing job making an expensive thing look cheap btw, does it take Duracell?

 

[Svperstar]

who built it. what are the power supply rail voltages. how much output stage current. how loud does the person listen

Mjolnir.

 

[bobkatz]

Well, I do enjoy the 007 off the refurbished and modded (with CCS) 007t from @spritzer . But, yes, it does scale up with the Carbon. Does not mean you cannot enjoy it nonetheless.

I'm a big fan of using equalization to finalize or polish even an already-excellent headphone. I use the RME ADI-2 FS to accomplish this... it has like 20 equalization slots that you can use for each of your headphones. I have both the 007 Mk2 and two Audeze CRBNs. The 007 is modded with Spritzer's port mod, I filled the little port with blu-tack. The larger circumaural diameter and oval shape of the CRBN give it an immediate soundstage advantage and reduces comb filtering. That does not mean that the 007 can't be excellent, as it already is a great phone. With EQ you can up the 007's bass a bit and yes, I found that it can take the bass boost without an issue. It brings the 007 up from my subjective B+ to an A- and the CRBN EQ brings it up from an A to an A+. If any of you would like to see my 007 and CRBN Eq's just send me a message on the contact page at digido.com.

 

[Svperstar]

I'm a big fan of using equalization to finalize or polish even an already-excellent headphone. I use the RME ADI-2 FS to accomplish this... it has like 20 equalization slots that you can use for each of your headphones. I have both the 007 Mk2 and two Audeze CRBNs. The 007 is modded with Spritzer's port mod, I filled the little port with blu-tack.

Love my RME and CRBN, also I bought my 007mk2 direct from Mjolnir so that the port mod would be done properly