The Headcase Stax thread

[kevin gilmore]

I'm pretty sure the transformer I have says 230v primary, will look tonight.

[spritzer]

Not sure about the low voltage caps but the high voltage supply should have no problem with higher AC input voltage.  The PSU is regulated so the output is fixed, the only issue being the prereg DC voltage not being excessively high for the filter caps. 

 

Any transformer hum from the "MT-F1"? That's actually one of my issues from the SumR transformers I've been using for my builds, lamination hum which gets to be audible from about a foot away. I'm getting quoted at 740 from cart100, that's a pretty good price for THE MUSICAL JOURNEY

 

Try to ask SumR to use a larger core.  That seemed to help when I was working on this with him. 

 

I know this is a terrible question to ask, but how much colouration is there or tube distortion in the BHSE?

I've only heard 2 tube amps, one hybrid, and all had some sort of tube colouration, usually affecting details in the bass end etc.
The Tube DAC also suffered from this, but that could have been older tubes.
Also the amps were a  Darkvoice and a Cayin HA-1A, relatively cheap amps.

I have 2 Universal Audio mono tube pre-amps, and a stereo tube pre-amp that really don't suck.
But they're mostly used on bass and drum tracks, and although you can hear a slight distortion, it doesn't seem to transfer to the final mix.
Overall, they help instruments sound much more organic. Can't honestly say it's entirely neutral though.

Are there any tradeoffs like this in the BHSE?
Are the higher end tubes free from impurities and/or colouration?
 

 

As others have said, tubes aren't just tubes in the same sense that not all transistor devices are equal.  To think of tubes being different to transistors would be a fallacy as they both do the same job and can often be used in very similar circuits.  There are differences in the same sense that bipolar transistors and mosfets aren't the same thing but the key difference is how any component is used.  The Stax 007t and the BHSE are both hybrids with similar rail voltages and many parts of the solid state circuit are similar.  How the tubes are used couldn't be more different though.  The 007t tube stage could just as well have been designed in the 50's and is just about as simple as they come.  The later version have added bits here and there but the final design is always the same.  The BHSE on the other hand is radically different.  Active circuits set the correct operational area for the tubes so they don't rely on the massive drift found in passive devices.  The tubes are also wired differently for even lower distortion so this is far from a normal tube amp. 

 

Moar expensive doesn't mean better tubes.  Shuguang is a good example of that and I for one would never use anything they make, in any of my amps.  The old Mullards were simply better made than anything today so that is the biggest factor. 

[kevin gilmore]

the heatsinks on the regulator transistors limit the energy to about 2 watts each.

So what they do is limit the pre-reg voltage, on my line voltage, its about 380v

not a lot of headroom.

 

this is one of the many differences between this thing built well, but on a limited

parts budget, and the massive overkill we typically do.

[spritzer]

I forgot about the tiny heatsinks.   

[n_maher]

I was going to say something about turning these things into little toasters but Kevin beat me to it.  You could always add a fan...

[Ali-Pacha]

the heatsinks on the regulator transistors limit the energy to about 2 watts each.

So what they do is limit the pre-reg voltage, on my line voltage, its about 380v

not a lot of headroom.

 

this is one of the many differences between this thing built well, but on a limited

parts budget, and the massive overkill we typically do.

Moaaar is better 

 

Ali

[jgazal]

(...) Active circuits set the correct operational area for the tubes so they don't rely on the massive drift found in passive devices. (...)

 

Suppose there is no solar energy, thus no high voltage transistors. Can tubes be used as active devices in such auxiliary circuits? 

 

I have read about "tube current sources" in Millet article: http://www.pmillett.com/current_source.htm and http://www.pmillett.com/el34_active-load_(srpp)_amp.htm.

[DefQon]

I'm very tempted - but I live in Perth.

You know you want to, you have the bhse too.

[kevin gilmore]

that is what the megatron is. All tubes.

 

does keep the room warm in winter.

[The Expanding Man]

You know you want to, you have the bhse too.

That I do, I've had some KGSS boards for a while, but this looks cheaper than DIY to me.

[eggil]

But without the fun of building it!

[spritzer]

That I do, I've had some KGSS boards for a while, but this looks cheaper than DIY to me.

 

This one does have to be fixed as there are a number of issues.  Heatsinks should be soldered down and grounded, the ground plane in a mess so not working properly and one resistor per side is running right on its limit.   There are also some small changes to part values and ideally they should be put right plus the transistor mounting to the heatsinks needs work. 

[The Expanding Man]

This one does have to be fixed as there are a number of issues.  Heatsinks should be soldered down and grounded, the ground plane in a mess so not working properly and one resistor per side is running right on its limit.   There are also some small changes to part values and ideally they should be put right plus the transistor mounting to the heatsinks needs work. 

Thanks for that - very helpful.

 

What's the enclosure like?

[spritzer]

Same Chinese stuff as you can buy on ebay.  It's normally pretty nice if the seller can be bothered to package it properly...

[Tyll Hertsens]

Hi guys!

 

Birgir and Kevin have done us all a solid, and I'm gonna need some help getting electrostatic cans in for measurement.

 

Really the easiest way to tell you about it is just to point you here:

 

http://www.innerfidelity.com/content/stax-mafia-makes-unrefusable-offer-and-i-begin-electrostatic-headphone-measurement-program

 

Looking forward to a bunch of new estate measurements! 

 

 

Thanks Birgir and Kevin! Imma make good use out of the KGSSSRE.

[Voltron]

Do you know what you have lined up and what you are missing?  I could conceivably send the following:

 

SR-Omega

SR-007BL

SR-4070

SR-X Mk3 Pro

[justin]

Can you measure the stax in-ears ?

Sent from my iPhone using Tapatalk

[Dusty Chalk]

I'd be curious how even the Koss and the 2020 measure.  I bet the 2020's at least measure really well.

[DefQon]

Can you measure the stax in-ears ?

Sent from my iPhone using Tapatalk

 

This would be very interesting. Tyll would need the desktop amp versions with the pro-bias plug rather than the SRM unit proprietary plug. Something I still want to try with my SR-002's. The original SRM-001 unit just doesn't really cut the cake.

[HeadphoneAddict]

This would be very interesting. Tyll would need the desktop amp versions with the pro-bias plug rather than the SRM unit proprietary plug. Something I still want to try with my SR-002's. The original SRM-001 unit just doesn't really cut the cake.

 

Yeah, I had to get Audiocats to mod my SR-001 Mk2 about 5 years ago, and it ended up sounding like an SR-003 plugged into an SRM-1 Mk2 Pro, but in a portable footprint.

[DefQon]

Yeah, I had to get Audiocats to mod my SR-001 Mk2 about 5 years ago, and it ended up sounding like an SR-003 plugged into an SRM-1 Mk2 Pro, but in a portable footprint.

 

Yeah I've followed that thread over on the other site, some crazy mods that Audiocats did with your SRM amp. The problem with the SRM-001 amp is that there is too much overpowering mid-bass. The laid back signature does remind me of the O2 mk1's but a far cry from actually sounding anywhere near it in terms of quality. I was going to order the 003 pro-bias cable for $90 here from a Stax distributor and try it out on one of my Stax amp's, not sure if it will sound that much better?

[kevin gilmore]

sr-003 are the in ears with the standard pro-bias plug

[nemomec]

Hello,

 

my chinese KGSS is now received.

 

Some positive things:

 

- it has a voltage selector for 230V and 115V

- it has a teflon stax plug

- the bias voltage is adjustable over the pot TVR1 (you need a voltmeter with high impedance)

- well built

 

But I have one big problem, the gain is extremly high and i can´t adjust the volume pot over 8 hour without distortion on different sources. Where i can adjust the gain or which resitors must be checked?

 

Edit: I think the cheap volume pot is defective

[kevin gilmore]

the gain is way high. I don't know why.  The 100k feedback resistors are actually 154k.

So its about 3.7db high in gain (unbalanced), 7.4db high (balanced)

There are resistors across the pot on the bottom of the

board, I never looked into the way they were wired.

 

NO reason why those resistors would be changed, the output bias is normal, so they

could be changed back to what they are supposed to be, then readjust the balance.

http://gilmore.chem.northwestern.edu/chinesekgss.pdf

 

birgir thinks its a linear pot that was converted to log via the resisistors soldered to it

on the bottom.

Edited May 26, 2014 by kevin gilmore

[nemomec]

Hello Kevin,

 

thanks for the infos! I have measured the resitors R73-R76 and there with 152K are ok, the bias and balance was also set to correct values. I think the volume pot ist the problem and ordered a new one. The pot has in the first quarter a very quick increasing of the volume but at the half to end there is nothing!? The design of my China KGSS is a little different from yours i post some pictures later, the Board has a new number F1a-1413.