The Headcase Stax thread

[mypasswordis]

[KrypticMind]

It has nothing to do with age, iirc it's around the 2-3kHz range so no way a part of age-induced hearing loss of HF.

Thanks for the clarification.

I don't think it's hearing loss, I think it's psychological. So I guess the correct retort would have been, "can't wait until I'm that mentally challenged"...No, wait, forget I said that.

[Ridleyguy]

delete

[Ridleyguy]

Birigr, can you think of any significance to the model number? Does Stax follow any specific naming convention?

'5' comes after '4'. Yes, I am one of those douchenozzles.

[bobkatz]

These bridge the two stators and protect them for voltage over 450V so you can damage the diaphragm

Thanks, Spritzer! By the way, I just finished replacing all the Electrolytics in my SRA-12 with Panasonic LOW ESR types. It's amazing how much smaller and compact electrolytics have gotten in the years. But what really was amazing was that the power transformer went from too hot to touch to practically stone cold! So the old electrolytics must have had considerable internal leakage. Just that fact alone made it worth replacing the caps. I had done a replacement sometime in the 80s or 90s and it was clearly due again.

I think it sounds better, too ).

BIAS on the normal phones. I had replaced the series R in the L pad (****NOT**** THE 4.7 MEG BUILD OUT R) with a 100k ohm rheostat many years ago so I could goose the bias. Now that the electrolytics are so much more efficient, I'm getting 233 volts in FRONT of the 4.7 Meg resistor. But even with no load I see about 160 volts on the load side of the 4.7 meg. But I don't think there is any leakage to ground on the load side. Is this normal? Must be because the DC is coming from such a high impedance source that even a length of wire load on the resistor will drop the voltage. Is this normal? Does this make any sense? Plugging in the cans the 160 volts barely drops so the cans load the resistor negligibly.

[Currawong]

Crap, crap, crap!!!! Most certainly a new driver design so I have to buy one...

I bags first listen. I'll take some high-res shots too.

I regret not getting the 4070s when I had the chance. I did get the 404LEs for 50k yen though so I can't really complain.

[Cynric]

I'm getting 233 volts in FRONT of the 4.7 Meg resistor. But even with no load I see about 160 volts on the load side of the 4.7 meg. But I don't think there is any leakage to ground on the load side. Is this normal? Must be because the DC is coming from such a high impedance source that even a length of wire load on the resistor will drop the voltage. Is this normal? Does this make any sense? Plugging in the cans the 160 volts barely drops so the cans load the resistor negligibly.

Yes, thats normal. Your Meter has an input impedance (probably 10Meg in your case), so are building a voltage divider with the output resistor thus measuring only about 2/3 of the voltage..

[spritzer]

Since the bias is essentially an open circuit then 233v before the ballast resistor is correct.

Glad to hear the new caps worked well for you. They certainly are smaller too...

[faust3d]

Cool news, I'll be interested in impressions from Birgir/whoever gets one. IMO this is the ugliest black Lambda to date, though.

I like the look of black Lambdas so what's ugly to one man, lol.

[bobkatz]

I spoke too soon. After about 1/2 an hour the power transformer heated up to its old splendor, can fry an egg on it. I still think it sounds better.

As for the bias, I thought my Fluke meter had an extremely high input R (Z) but I guess not, it must load down that voltage, so (as people have mentioned) it's important to adjust the bias measuring in front of the 4.7 Meg build-out resistor.

My next question goes to hotrodding that old SRA-12S. First is on the bias on the old SRD-5 diaphragm. How much is a risk? I used to adjust the bias until the short hairs on my arms stood up on end and then back it off a bit ). (Seriously). Now it's back to 230 volts as I'm getting nervous. The higher bias increased the sensitivity and headroom considerably and I did get (I felt) better, sweeter sound, less transistor harshness. The next thing I've been doing is adjusting the collectors of the output transistors 10 volts higher than recommended (for what it's worth). Of course, this is contributing to the current drain on the little power transformer (. So the collectors are running at 310 volts and again I feel the sound is improved. It sounds a lot more like a class A amp. I have not looked at waveforms with a scope or measured the distortion. It's possible to push those collectors into the stratosphere, but how hot is too hot?! It's definitely "fry an egg" time at the power transformer and V+ resistors and output transistors so basically I've stopped pushing the voltage.

Next thought is to replace the 4700 pf silver mica output coupling caps with something bigger in hopes of getting deeper bass?

Of course this is all academic now. It's funny I'm concentrating on my old SRA when Justin is building me a KGSS and I'll be buying an Omega II shortly. I have a converted SR5NB (Gold pro) made from an Alpha (Gamma) coming to me also. So maybe I'll let that hotrodded SRA-12S and 3 beautiful SR-5's go, eh?

[spritzer]

The Fluke's all have 10M input Z which isn't enough for measuring after the ballast resistor. A VTVM will do the trick though...

The diaphragm to stator distance on any of the normal bias Stax models is 0.3mm which means the phones could handle at least 400-500V of bias if the drive voltages stay low enough and the air isn't excessively humid. I've run normal bias phones at Pro bias (580V) and it is fine as long as you don't push the volume to high. Now the Pro's will handle a lot more voltage, the SR-007 doesn't care at all about 900V bias...

The thermal spec for any SS component is the junction temp which is impossible to measure properly. I for one wouldn't push any transistor much past 90

[Salt Peanuts]

[url=http://www.stax.co.jp/Japan/SR507_1_JP.html]

[bobkatz]

Dear Spritzer: You're a gentleman and a scholar! I have a Fluke temperature probe, I'll see what's cooking ).

I've got FOUR Siderealkaps left over from a tube project. 3.3 uF 200V "premium audio grade capacitors". These caps are so beautiful. Nice yellow cover over polypropylene I assume. The question is whether 200V is safe. The silver micas that are in the SRA are rated at 500 v. Can I get away with a 200 volt cap? Legally no, but it's so little current... but the cap will be charged to 310 volts or so. There's a bleeder resistor to ground on each stator of 10M. Would you risk it or start looking for a higher voltage cap?

[spritzer]

When I had the SRM-T2 project I looked up how much heat it would take to cook an egg. Turns out to be 60

[mypasswordis]

I like the look of black Lambdas so what's ugly to one man, lol.

No, I like the look of black Lambdas, as opposed to vomit grey or shit brown. I'm just saying this one is the ugliest of the black Lambdas, as in I prefer the look of the NB Lambda, Lambda Pro, Lambda Sig (partially brown, but meh still prefer), Lambda Nova Basic, SR-202, SR-404LE, Lambda Spirit, and whatever else I'm missing. That's just looks, not saying anything about sound.

[manaox2]

[url=http://www.stax.co.jp/Japan/SR507_1_JP.html]ƒCƒ„

[padam]

All Lambdas look hideous (when worn anyway) so on that basis, a Sigma is better offers moar of the same

Stax, bring it back with new housing and these drivers, do you hear me??

[spritzer]

Reading between the vague marketing speak, the drivers are the same size but now everything inside them is smaller to accommodate the external frame. Less panel area which wouldn't be a bad thing but I can't wait to get my grubby hands on one of these...

[bobkatz]

In English: Open air type Earspeaker : SR-507---New products

Whole new driver film and case material. Interesting.

Just supposition, but how do you think these 507 will compare with the Omega II? Which will sound "more neutral"? I never liked the sound of the Lambda-type and Sigma-type enclosures before (too resonant and boxey), but these appear to be "square Omegas" to my thinking as they appear to sit directly on the ears and not have a large resonant cavity.

[spritzer]

I'm pretty sure they are better then a standard Lambda but I don't think they took the design far enough. What makes the SR-007 so good is the utter overkill in terms of chassis design and how the earpieces are coupled to the head. Put the same drivers in an SR-Omega chassis and the superiority of the SR-007 frame becomes quite clear.

With the SR-507 the big question is really how different is the new driver design and how are the drivers attached to the baffle. The Lambda/Sigma drivers have always been mounted with double sided tape to the baffle which is far from optimal imho. Some form of clamping mechanism would be far superior and provide the mechanical coupling the drivers need to get rid of any resonance. My ideal Lambda would really be an open version of the 4070, same arc assembly but the drivers mounted in an aluminum/resin sandwich.

[Nebby]

I was tempted to say the 507 will probably sound "blacker" while the Omega has more of a "rounder" sound.

[manaox2]

As long as they keep the forward sound signature of most of the lambdas with some real improvements, I suspect they will be very popular. At roughly the same price about as a used O2, I would jump on the O2 first, although I love how musical sounding most of the lambda series are. Like Spritzer said, not sure they took the design far enough, so I suspect a bit of that same sound signature as that in the Nova series may stick around.

[Tachikoma]

If only they'd make something like a smaller, easier to drive O2 instead :/

[morphsci]

^^^ But then it would not be an O2.

[Tachikoma]

I prefer the SR-5/X/3 and O2 to the lambdas I've heard (pro, sig, nova sig, 303), so that's perfectly fine.