[bcg27]

I actually saw a really fantastic video of a guy making his own vacuum tubes. It is in french but I thought it was fascinating and really, reallly impressive. Supposedly the guy made all of the jigs and stuff that you see in the video. Here is the link: http://www.dailymotion.com/video/x3wrzo_fabrication-d-une-lampe-triode_tech

 

[spritzer]

The tubes we need are very particular so high plate voltage but not a whole lot of power.  The old TV tubes were many like this given the very high voltage inside the ol'box but tube TV's died out in the 70's.  This is also the reason why we are running out of good high voltage transistors since CRT's are dead... 

 

[Maxvla]

I really don't think the situation is all that bad. You have what, seven Stax headphones that aren't portables, plus the Koss headphones and I guess the Jades. How many amps do you need to serve such a small market? Sennheiser alone makes WAY more headphones than that. Combine that with hundreds of other dynamics and you can see why there might be a few more amps on that side. For most of the available models, the 323S, the 006TS, and the GES should all be perfectly fine.

The Omega 2 can be driven by the 727II or any of three currently available ultra high-end tube amps, plus the upcoming LL, and possibly the Electra, I don't know what the voltage swing is going to be on that amp. Do you need more than 7 choices including the KGSSHV for one headphone?

I guess the problem for me with the Stax amps is that I have no idea what they are. They are just numbers, and a ton of different models. They don't seem to go in any sort of order, like higher model number is better, etc. And of course all the versions of the same model number.

 

[DaveBSC]

Quote:

I guess the problem for me with the Stax amps is that I have no idea what they are. They are just numbers, and a ton of different models. They don't seem to go in any sort of order, like higher model number is better, etc. And of course all the versions of the same model number.

There are a lot of discontinued Stax amps that can be tough to keep track of, but there are only 5 current production Stax amps for the American market as far as I know. On the solid state front you have the entry 252S, mid 323S (the S models replaced the "II" models for 2010) and the top 727II. No 727S as of yet. For tubes, you have the mid-level 006TS (again replacing the older 006TII) and the top 007TII. Despite being a top model the 007TII swings significantly less voltage than the 323S, which makes it not particularly well suited to drive the Omega 2. 
 
Japanese market amps are called "A" instead of II.
 

 

[sphinxvc]

Is the 727 an improved version of the 717?  Or did they move backwards the way they did with the O2 MKI/MKII?

 

[DaveBSC]

Quote:

Is the 727 an improved version of the 717?  Or did they move backwards the way they did with the O2 MKI/MKII?

It's a different design. IIRC, the 717 is a modified KGSS. The 727 is kind of like the O2 MkII actually, not so great stock, but there's a Spritzer mod to fix it. With the mod in place, it's better than the 717.

 

[TMoney]

EDIT: Removed in light of Kevin's post below.

 

[kevin gilmore]

The 727 is a local feedback version of the 717. The 727 has a current source, the 717 has a resistor. Otherwise virtually identical.
The 727 runs the output stage at higher power.
 
The kgss and the 717 are similar amplifiers. (4 stage amplifiers)
 
The kgsshv and the 727 are similar amplifiers except the kgsshv uses global feedback. (4 stage amplifiers)
 
If people want it, the next revision of the kgsshv boards will have the local/global feedback option.
 
Personally i like the sound of the global feedback version better.
 
The 313 and 323 are 3 stage amplifiers. Same or similar to all the transportables (srmXh,srm151,srm252)
 
There are the 2 ac coupled single power supply amps, sr-001 and srm300
 
the srm-t1, t1s and 006t are virtually identical. (solid state/tube hybrid)
 
the 007 has twice the number of output tubes and runs the output stage at twice the power. (solid state/tube hybrid)
 
The T2 is a tube/solid state/tube hybrid.
 
The BH and BHSE are essentially the T2 output stage with the kgss input stage configured for 800 volts.
 
For stuff older than the srm-t1, things get complicated. spritzer has more of the really old schematics.

 

[DarknightDK]

Quote:

That was my experience at the Bay Area Meet as well.  I preferred the Liquid Lightning over the BHSE with the 009.  And the Stax SRM-727II over both the LL and the BHSE. 
 
 

Did you say the SRM-727II sounds better than the LL or the BHSE?? Is this in relation to using these amps with the 009?
 
Could you post your impressions of the sound of the SRM-727II's as compared with the LL?
 
 
 
I've read some mixed impressions of the SRM-727II and not many seem to recommend it. I'm considering getting the 009 in future and wonder if the SRM-727II is a good match for the 009. So far, the LL seems to be a great match but its way over budget. Are the differences in sound between the SRM-727II and LL subtile?
 

 

[spritzer]

While we are on the subject, Stax amp history lesson. 
 
First SRA1-8 amps were all classic tube units of varying complexity made in the 60's. 
 
SRA-3S was the first deviation from this with a transistor front end and AC coupled tube output stage.  Preamp and phono amp on plug in cards similar to the old ISA units used in PC's. 
 
SRA-10S/12S were the first SS amps with a push pull front end and AC coupled outputstage.  Run fully in Class A they get stinking hot and feature a nice regulated PSU for the low voltage circuit and a stacked PSU for the +640VDC B+. Similar plug in system as on the SRA-3S but now everything except the basic PSU is on plug in cards and the build quality is far better. 
 
SRD-X was the first portable Stax amp and features an automotive chip amp driving a pair of transformers.  Think Darkstar but with much better specs done in 1979.... 
 
SRM-1 Mk1 was pretty much the same circuit as the SRA-12S but turned on its head.  Similar AC coupled output stage.  I recently refurbished one of these and it is a nice little amp but the SRA-12S is better over all. 
 
SRM-1 Mk2 is where things get tricky since there are so many variations of it.  The first ones were some weird Mk1/Mk2 hybrid though fully DC coupled but later units are much more similar to the current crop of Stax amps like the 313.  Now the amps are fully balanced from input to output though most only have RCA inputs. 
 
SRA-14S is pretty much the SRM-1 Mk2 circuit but turned on its head.  Better parts and some tweaks but most of the price difference is spent on the preamp capability. 
 
SRM-3 is just a SRM-Xh with a full size power supply.  It even uses the same circuit boards. 
 
SRM-600LTD is the same basic circuit as the T1/006t but modified to take the ECC99 tube. 

 

[milosz]

Quote:

The KGSSHV is not an evolution on the 727 or the 717 for that matter.  What on earth gave you that idea?  The 727 is just the latest version of a long running Stax circuit (around 30 years old now) but the KGSSHV is the ultimate version of the old KGSS.  Kevin even talked about doing these mods in his old KGSS article but the parts were in short supply then.
 
The BHSE being designed for the SR-007 is another baseless statement.  The Blue Hawaii makes all electrostatic headphones perform at their best but that doesn't mean that the end result is better subjectively.  The HE90 s a good example of a transducer needing a sympathetic match and I do think the SR-009 falls into this category.  This is a "fault" of the transducer and not the amp.  The amp I use with the 009's is a bit of an oddball, a fully rebuilt SRA-10S.  I bypassed all of the preamp stuff so the end result is a push-pull driver stage with a single ended output stage fed off a single B+ and thus needs output caps.  The only issue with this amp is the high capacitance of the old TO3 output devices but I've got some parts sitting in customs to try and rectify that. 

>> The amp I use with the 009's is a bit of an oddball, a fully rebuilt SRA-10S<< 
 
What?  Not a T2, DIY or otherwise?
 

 

[Headdie]

Gentlemen,
 
I have an SRD-7. I'd like to take it twenty feet away from my power amplifier, just beside my computer and listening chair. To do that, I wonder if I could run speaker cables from my amplifier to the SRD-7 loud speaker outs (yes the SRD outputs)... And to turn them into inputs, I would also connect the SRD inputs to the SRD loud speaker outs... Hoping that you follow me... Now, I don't understand the electronics inside, but reasoning it as a blackbox, it seems to me that it should work... The front switch would just become an on/off switch... Could someone tell me if I'm gonna fry everything inside or get sweet music if I do it ?
 
Thank so much,

 

[maverickronin]

Just connect the extra speaker wire to the leads on your SRD-7.  Get some twist connectors of you don't have a soldering iron.

 

[tyre]

I'm curious where the idea that the regular Stax amps are insufficient to drive the O2 originates from. Are there any objective measurements around to verify this?

SR-007mk2:

Impedance : 170k (at f = 10 KHz)
Capacitance : 94pF (including cable)
Sensitivity : 100dB / 100V r.m.s. at f = 1 KHz

SR-507:
 
Impedance : 145k (at f = 10 KHz)
Capacitance : 110pF (including cable)
Sensitivity : 100dB / 100V r.m.s. at f = 1 KHz

There doesn't seem to be a great deal of difference here. Sensitivity is identical, and capacitance is actually lower on the O2.

 

[spritzer]

Quote:

>> The amp I use with the 009's is a bit of an oddball, a fully rebuilt SRA-10S<< 
 
What?  Not a T2, DIY or otherwise?
 

Nope and this is with a rack full of electrostatic amps.