The Stax thread (New) - Page 560

Aha, I see. Interesting.
Hope all goes well.

First I've ever heard of anyone dreaming about headphones.

This type of assessment is a tall order. You will see a number of discusssions of specfic phone/amp combo's but full scale comparisons of several amps and several phones are rare, if not non-existent.

I can give you my impressions of a number of my Stax phone/amp combinations and something about the Koss 950 as well, since it is increasingly being used with Stax amps.

Stax phones go back to 1960 and Stax immediately began offering both amplifiers and transformer-based adapters for their phones. The adapters require use of an existing power amp to drive. The amps by comparison are connected to a line level source. Stax stopped making adapters about 10 years ago and now only offer amps. Ther are also a number of other makers of small numbers of amps for Stax phones. These are generally more expensive than Stax products.

The Stax phones vary quite a bit in their efficiency and I find that I can run the more efficient ones such as the SR003 quite nicely with the cheaper amps whereas you need a bigger amp for the less efficient O2's and Sigmas.

It's been years since I had a transformer adapter and I can't say much about them. There is some agreement that they can give good dynamics with Stax phones, but lack detail. They are also more likely to damage your phones than amps because they can be overdriven by power amps. It is hard finding transformers with high (pro) bias and most of what is sold are the older low bias units for the older low bias phones.

My oldest Stax amp is low bias, a SRA12S which is actually a pre-amp, which I still use in that role. It sounds pretty good with a low bias Sigma and SRX3.

I have an SRDP which is an older portable amp, with 2 high bias outputs. It is decent with the Stax phones that are easier to drive such as the SR003 and various Lambdas. They struggle somewhat with the Koss 950 and even more with high bias Sigmas but are ok for limited or portable use. They will drive the O2 but not to anything like its potential.

I also have an SRDX which is a low bias portable amp like the SRDP, specifically set up for use with existing headphone sockets. As an amp my understanding is that it has some cheap power amp chips driving transformers so it is kind of a hybrid amp/transformer system. I find it suprisingly good with the SRX3, but the SRA12S is better with these phones.

You can actually run high bias Stax phones on low bias amps, with some loss of volume and dynamics. I would say that only the SR003 runs very well from a low bias source.

I run 2 SRM3 amps. They are pretty good with Lambdas (Nova and 404) and SR003's. They sometimes run out of steam with the Sigmas and the O2 doesn't sound too clear on them but is serviceable.

My top amp is the Stax 717 (now 727A?). It runs every high bias phone well and really allows the O2 and high bias Sigmas to shine, although it also somewhat improves the Lambdas compared to the SRM3.

I don't think that the shape of the drivers has much to do with it. Spritzer would be able to tell you better in terms of what actually makes the O2 and 003 have such outstanding slam. From what I've read the ESP950, the 4070 (which uses the same driver as the 404), and the SR-X MkIII also have very good slam. I can somewhat attest to the latter since I have a custom headphone on loan that uses Gamma Pro drivers, which are also in the SR-X MkIII Pro, and it has serious slam. Better than my O2 from the 717, but the 717 is hardly doing the O2 any favors in the slam department.

If you do have a chance to listen to the O2, make sure it's the Mk1 model to relate to what I'm talking about. I had both the Mk1 and Mk2 in my hands at one point and they're quite different. I prefer the Mk1 by a long margin. The Mk2 does have serious slam as well.

I don't have dreams about headphones, but that's mostly because I'm too busy dreaming about geometric abstract representations of the concept of free will, zeppelins made out of genetically modified dogs, future dystopias filled with giant robots, and cannibal crabs eating the fabric of reality from which my dreams are made.

But maybe your dream is a sign to get some Sigmas?

I am trying out different methods of amping my new O2 Mk2 (about 75 hours of burn-in so far). I want to be able to use my O2 in more places around the house than just in my main rig with the Woo GES.

It's been mentioned here previously that the SRD transformer boxes have a power handling rating of about 7 watt per channel from a speaker amp. I have an SRD-7 Pro hooked up to a 12 watt per channel Nuforce Icon speaker amp. With my HE60 and Lambda Sig I usually don't have to go past 12 o'clock on the volume for loud music. The ESP 950 need a little bit more power up to 1 o'clock. But with the O2 if I want get nice loud clean punchy dynamic music reproduction, then sometimes I need to crank the amp up to 3 o'clock or more (very high power but still below the point of clipping). I only tried this briefly, like for 30 seconds but got scared of damaging the SRD-7 Pro.

Would you experts reassure me that as long as I keep the amp out of clipping, that I can give the SRD-7 up to the 12 watts of clean power that I have on tap and still be safe? Is there maybe a time limit where 12 watts is fine for an hour or two, but then over-heating could be an issue?

Thanks!

Also, I remember there being a nice up-market Transformer that was not built by Stax on some long-gone thread. Anyone else share this delusion with me?

The Illusion I think it was called, not delusion.

Well there's a happy accident for you.

So be it, although I'd be looking at other assets first as the bass is not the main selling point for me. Of course, nice slam is always nice, no questions about it!

Now that's how I want to interpret it.

I've heard of many people driving a SRD with high power (over 50 watts) without any trouble. The real problem is overdriving the headphones and arcing the driver. Replacing a driver can be expensive. The low bias phones have closer stator spacing and are even easier to arc.

A transformer needs sustained over current over time to be destroyed. The drivers just need a voltage transient over the breakdown voltage. Totally different conditions for damage. For you to heat the transformers you will probably have transients over the breakdown voltage of the drivers.

A low power amp clipping has a lot of high frequency energy that can have voltages high enough to arc the driver but not hurt the transformer. I would much rather have a bigger amp that has no chance of clipping and just be careful of the volumes that you listen.

In almost all cases the phones will go before the transformer. Be careful.

The most common reason for the lack of slam in ES transducers is the chassis design and that so much of the energy is wasted on vibrations. The ultimate test for this is comparing the excellent SR-Omega chassis to the SR-007, both fitted with the same drivers. Very similar sound but the older chassis can't handle the same amount of bass information and smears them, creating a slight boom. The SR-003 might be made out of plastic but the chassis is tiny and in direct contact to the head so all vibrations are soaked up by the head.

I'm currently driving my SR-007 with the Cambridge 840A which has 120W per channel and I'm kind of worried too about blowing off the drivers. I've been told that as long as I don't overdrive the Stax, everything should work fine, but is there anything else that can damage the drivers? Like a resistor frying in the transformer box or something like that? There's not a lot of documentation about driving the Stax with amps that have a lot of power. It sounds excellent by the way, punchy sound with very good dynamics. Not on the same level as a KGSS, but it does justice to the SR-007 a lot better than the Stax amps I have heard.

So, if I have an SPL meter available, what max db of playback volume would be safe with the SR-007 Mk2 if driven with clean non-clipping power?? (i.e. with HD600 it is about 1/5 watt and 118 db output level).

Transient spikes are what usually arc a stat. Most sound level meters are average responding and can’t measure a transient very well (unless you have a expensive impulse meter like a B&K). If you listened to a lot of compressed music (most pop/rock) you could listen overall louder than music with wide dynamic range with a lot of transients (Jazz & Classical). A loud drum rim shot, a cymbal crash, a snare drum hit, a trumpet blast, a loud bass guitar can put you over the top and a averge SPL meter would not respond fast enough.

You could contact Stax USA and try to find out what is the breakdown voltage of the driver. Then you would have to connect the high voltage output of the amp to a oscilloscope that is calibrated to a output of a high voltage probe. Look at the scope when playing music and do not let the waveform go above the breakdown voltage. Way to much trouble. What you need is a device that would go between the amp and phone that would have a LED that would light when you are getting near the limit.

When I was a Stax dealer in the seventies we used to replace SR-X and SR-5 drivers all the time. We would tell our customers to turn down the volume or switch to a dynamic headphone. This applies to stat speakers also!

Bottom Line, If you want to listen to headphones at extremely loud levels I would stick to dynamics.

Hello there,

I searched and could not find anything on cleaning out old Stax.
The pair of Lambdas I recently got have some tiny pieces of foam stuck between the grill and driver causing what sounds like static. There is also a bit of noise when I moved the right cable lead.

Any help would be appreciated.

Thanks.