[Muffinhead]

I didn't mean to suggest you shouldn't be. But maybe taking a step back and completing something easier first would be a smarter idea? The o2 won't take but an afternoon, for example, and it can't do anything but help with this project

Could you link me a cheap O2 kit with a chassis? Thanks

 

[SeaWo|f]

Literally googled "o2 amp kit" third option under shopping..

https://www.ebay.com/i/282756370081...3D711-117182-37290-0%26rvr_id%3D1418631428629

 

[JimL11]

I also suggest that you get someone local who is experienced in DIY and can look over your shoulder to catch mistakes before they happen.

 

[Muffinhead]

Cap replacement was finished today without a hitch. Amp sounds OK from the first few minutes of listening. I think I'm gonna order the O2 and do some more research before I proceed with the actual mod. Are there any resources anyone would suggest for a beginner like myself?
Thanks again for the help and patience, guys.

 

[astrostar59]

Selling my Stax 007As 2015. Anyone interested PM me.


https://www.head-fi.org/threads/stax-007a-2015-as-new.870062/#post-13981948

 

[DJ The Rocket]

Triple Staxenrainbow

L to R: SR-Lambda Professional, SR-407, L300​

The L300 is going to be for sale again soon. Not my cuppa, though I think they would shine on a tube amp, which I don't have. I've been thinking about a KGST more and more, but it isn't like I have any complaints about my feedback modded 727.

The Lambda Pro and 407 are keepers!

 

[DJ The Rocket]

Could you link me a cheap O2 kit with a chassis? Thanks

I hope this helps you as much as it helped me! You'll have a killer headphone amp for dynamic drivers at the end, and I bet you enjoy it too.

JDS Labs sells kits with the PCBs and all components for $60, which is a good price. You can save $10 uploading the BOM to Mouser and ordering from them, which I recommend for reasons beyond the $10.

It seems like the kit would be easier, but I entered each part's location on the board in the "customer number" field, which Mouser prints on every component package. This organization made filling the board so much easier!

Anyway the PCB is $6 from JDS, components were $45 from Mouser. The standard aluminum enclosure was $15 (I got one from Granger, because they had the silver finish I wanted), but you can make your own enclosure out of anything, if you want to save that $15. I drilled out the faceplate myself, but JDS sells prefabricated faceplates if you prefer that route. JDS is a good resource for this in general, I got a set of plasic screws in case I decide to install the ODAC in the o2 enclosure.

 

[hpeter]

With due respect, I see the words “virtually” and the expression “however the amplifier definitely sees the power as real” as a similar way to state your explanation.

Dr. Gilmore saw a misconception that was not explained in your post, that the 580V is usually associated to the bias voltage and is not the theoretical maximum voltage the stators can be driven, that, AFAIK, is a little lower than the power supply voltages.

It is so rare to see engineers helping consumers to see the technical side of products and I feel, as a layman who has been reading what Dr. Gilmore posted in the last decade, that such help is utterly important, so I just wanted to politely say, JimL11, that your post may be interpreted - by those that are not used to read what both of you brilliantly explain - as fire. And that feeling could be detrimental to the community, even if those who are used to read such explanations, can identify such post as friendly fire.

That said, there is still an underlying doubt/mistery to me. I have read your brilliant explanation about the energy content and how much that energy is spread over frequencies, particularly over bass frequencies:



Dr. Gilmore says that, at 20khz, the headphones can pull the equivalent of more than 1 watt per channel.

How much the headphones can pull at say from 50 to 500 Hz?

I am still having difficulties to understand loads that are predominantly inductive/resistive loads versus predominantly capacitive.

I thought that predominantly capacitive loads demanded more energy in high frequencies (20khz) and that predominantly inductive/resistive demanded more energy at low frequencies (say from 50 to 500 hz).

Would you please help me to understand where I am failing?

sr l 300
110pF
0,14mW@100V 20Hz
0,14W@100V 20kHz

ohms law+ reactance calculator

 

[Muffinhead]

I hope this helps you as much as it helped me! You'll have a killer headphone amp for dynamic drivers at the end, and I bet you enjoy it too.

JDS Labs sells kits with the PCBs and all components for $60, which is a good price. You can save $10 uploading the BOM to Mouser and ordering from them, which I recommend for reasons beyond the $10.

It seems like the kit would be easier, but I entered each part's location on the board in the "customer number" field, which Mouser prints on every component package. This organization made filling the board so much easier!

Anyway the PCB is $6 from JDS, components were $45 from Mouser. The standard aluminum enclosure was $15 (I got one from Granger, because they had the silver finish I wanted), but you can make your own enclosure out of anything, if you want to save that $15. I drilled out the faceplate myself, but JDS sells prefabricated faceplates if you prefer that route. JDS is a good resource for this in general, I got a set of plasic screws in case I decide to install the ODAC in the o2 enclosure.

Just ordered the kit with chassis from ebay, so that'll be here soonish. TBH, I'm pretty excited to build an entire amp from just parts. If I don't end up keeping it, is the resale value on the DIY O2 good?

 

[JimL11]

sr l 300
110pF
0,14mW@100V 20Hz
0,14W@100V 20kHz

ohms law+ reactance calculator

Yes and no. That may be what Kevin Gilmore was referring to, but as I have said before, an ideal capacitor does not burn up energy, whereas a headphone does, in producing sound and heat. In an ideal capacitor, voltage and current are 90 degrees out of phase, so what energy gets dumped into the cap during one part of the cycle gets dumped back into the amp in the other part of the cycle, so theoretically, no energy is burned up. However, an ideal capacitor also makes no sound. The process of making sound uses up energy, so in fact a headphone has a resistive part of its impedance where current and voltage are in phase, and which is NOT stated in Stax's specified impedance. Hard to know what that part of the impedance is.

The reason I say that that is what Gilmore was referring to is that although there is no energy loss, hence his use of the term "virtual" (I assume this is what he meant), the current demand on the amplifier is very real. So I think that is what he meant, hopefully he will clarify.

 

[tigon_ridge]

You know, in physics class, they always assume that a charge (usually an electron) between two plates of a capacitor is always subject to a perfectly constant electric field. The students never question, "But newton's third law dictates that the charges on the plates are pushed by the single charge just as much as they're pushing the charge. That would push them out of the plates, and therefore lower the the E field, and therefore the voltage, right?" We assume that it's negligible because a single electron makes little difference.

Well in our case, instead of a single nearly massless electron, there are bajillions of particles that constitute the diaphragm and air. Think of the e-stat driver unit as a capacitor with really high ESR (equivalent series resistance), because that's exactly what it is.

Now, the efficiency is a separate matter. Theoretically, the further the plates are placed from each other, the higher the voltage has to be to maintain the same E field. That's more of an amplifier problem than a driver problem. I don't think it's a matter of e-stat headphones being inherently inefficient as it is that it is just difficult of designing a high voltage amp.

 

[Darbosa]

Stax SR-L700: is it channel imbalance?

Recently bought SR-L700.
First impressions are good: comparing side-by-side to SR-303 and Stax SR-5N (Gold) on the same tracks and on the same amp (with SR-303 on SRM-310) I found the sound of L700 as softer in the mids, the whole picture is moved a little bit away and overall sound stage expanded. Voices (especially female ones) sound a little bit different, would say... refined, not so "in the face" as on SR-5N... and so also some instruments with emphasis in the mids - maybe because of L700's slight drop in 2,5 - 3 kHz region.
Would say also that L700 has slightly deeper going, more "juicy" bass - but only in the region lower than one from e.g. percussions - here I heard no difference with SR-303 and SR-5N.
The highs are more present and at the same time more "airy" than on both SR-303 and SR-5N.
Overall impression - not bad and improvement over SR-303 and SR-5N in all respect...

BUT. I have noticed at once that the main focus of the sound picture, in most cases it is the lead vocal is moved slightly to the left - about to the 11 o'clock position. When I put on SR-303 and SR-5N back again - the focus moved back on both to 12 o'clock. Litstening to both cups separately did not reveal loudness difference, but I guess it is not the right way to find the channel imbalance unless it is in the extreme extend.

Is it really ill-famed channel imbalance. And what are better ways to measure it (without professional gears)?
If I replace SRM-310 with any amp with has separate channel level adjustment on the fron panel (actually almost all Stax amps) - will it remedy the issue by just raising a little bit the volume of right channel.
Of course it will change the the track's original picture, but maybe it will bring the main voices and focus on the 12 o'clock spot back?

 

[pegasus21]

I have a SRM-353X 100V and I don't think it can be converted to a 230 or 240V based on the primary only having 2 wires. Is anybody able to confirm this?

 

[kevin gilmore]

sure looks like that is 100V only, Not sure whether there are pins under the plastic.

you might be able to find a friendly stax dealer that can order you a new universal transformer.

 

[wink]

... or, just get a stepdown transformer....
120v/100v or 230v/100v......