The Entry Level Stax Thread

[ludoo]

The Lambda 1.5khz peak is easily tamed with a thin sheet of foam. I used 0.3mm in my 207. Like this, just a lot thinner

 

[Philimon]

^ Interesting. Ill give it a shot.
In the past Ive used alternate pads to tame the 1.5kHz peak.

edit: because stupid anti double post feature

@ludoo @gammi

252s vs SRD-7

^ averaged frequency response measurements

Did I notice a difference subjectively? No.

I did notice that the 252s (uprated power supply) could seemingly get louder than my SRD7mk2 (modded and paired with Schitt Rekkr 2W @ 8ohm) based on how much pre-amp (Saga2) volume was needed to reach 90dB. May sell SRD7mk2 and save on desk space.

I could easily squeeze more bass extension out of SR-X1 (modded) by using less front-side venting but Im not too concerned atm. As modded, SR-X1 is slightly too bright but nothing Lokius cant fix. Preferable to stock because comfort...

SR-207, fwiw:

^ various levels of pad seal and never quite full seal on EARS coupler

I feel that I get a decent seal on my personal head but who knows. I will 3DPrint a pad adapter to padroll.

207 reminds me of 507 in that I perceive these as slightly warmer and bassier than prior generation Lambdas. Part of that perception is definitely pad seal related as the pads harden over time causing reduced seal. 07 series is still new enough to have decent condition pads still. L-series are tuned quite differently from prior gens with a purposefully vented front-side so difficult to compare. If interested Ive measured and modded a few different Lambdas for which you can find impressions scattered in the other Stax thread.

 

[Rob80b]

Here's a question for those who may have added a more robust power supply to their SRM252S, does it allow the 252 to be played louder, I'm thinking no as reading that this is inherent in the design where the circuit could only be driven so hard , but could be mistaken.
Reason I ask is that I was quite annoyed to find that the 252S powering my L300 would hit a wall and start causing the sound to distort quite badly is wishes to play louder once in awhile.
So recently I added the SRM400S and couldn't be happier, no distortion what so ever but if a beefier power supply may help the little 252 I might hold onto it as it is a decent driver but has its limits.



My 252 came with an adapter configured for 120

 

[Precaud]

Here's a question for those who may have added a more robust power supply to their SRM252S, does it allow the 252 to be played louder,

If by 'power supply' you mean the AC adapter, the answer is no.
But you can change the gain structure internally and stop it from distorting so early. Some details are here:
https://www.linearz.com/stuff/upgrading-the-stax-srm-252s/

 

[Rob80b]

If by 'power supply' you mean the AC adapter, the answer is no.

That is what I assumed.

But you can change the gain structure internally and stop it from distorting so early. Some details are here:
https://www.linearz.com/stuff/upgrading-the-stax-srm-252s/

Excellent, thanks.

 

[Philimon]

SR-207 plus hybrid oval pads sounds niiice.

 

[Rob80b]

SR-207 plus hybrid oval pads sounds niiice.

I'm very content with L300 (thicker leather pads and MKII headband assembly) now that I've added the SRM400, have a request out looking for a L700 but not too sure how much it will improve the overall listening experience.

 

[catscratch]

SR-207 plus hybrid oval pads sounds niiice.

Those are some nice squiggles.

It's close to how I EQ my stats in general, vaguely similar to HD600/650 but with a few db less upper mid and a small notch at 7-7.5k to take the edge off. I can confirm that stats with that kind of FR sound pretty freaking great.

 

[Philimon]

Those are some nice squiggles.

It's close to how I EQ my stats in general, vaguely similar to HD600/650 but with a few db less upper mid and a small notch at 7-7.5k to take the edge off. I can confirm that stats with that kind of FR sound pretty freaking great.

The 207 with padroll is lovely and reminds me of a higher fidelity HD6X0. The oval pads however I ended up not enjoying as the depth and narrowness of the ear chamber kindve constricted the soundstage. Switching back to the round pads is preferable as they are shallower with larger ear chambers. Ive settled on Harmonicdyne (Athena) pads on both 207 and SRX1. edit: I agree with your assessment of 6X0 sound and that 7k-8Hz peak is present on 207-Athena as well but the upper mids are not an issue.

Spoiler: mehsurements

Minidsp EARS, Stax 252s

I'm very content with L300 (thicker leather pads and MKII headband assembly) now that I've added the SRM400, have a request out looking for a L700 but not too sure how much it will improve the overall listening experience.

I preferred the tuning of current gen L500 over prior gen Lambda but the build quality haunted me with its creakiness. Modding 207-507 gave me the best of both worlds. Stax's SR-X1 makes me hopeful for the next gen Lambda. I think Stax's SRX1 is built well and tuned well relatively but has a fatal flaw in that the stock ear pads are too tiny for average people. SRX1 shouldve went with more standard sized pads or gone full supraaural like prior gen SR-X.

edit: for context my 6X0 mehsures

Spoiler: 6X0

 

[ericj]

After dithering for much longer than should have been necessary, I ordered a batch of 5 prototypes of my universal SRD-4/5/6/7 upgrade board from jlcpcb today. Hopefully it works properly!

I don't have an SRD-6 so i am unsure of fitment in that energizer but there's a good chance i guess? I can move the mounting holes if need be. I had assumed that the SRD-4 and SRD-6, sharing the same chassis, had the same mounting, but they do not. The 5 and 7 have similar fitment except that the 5 is much smaller and mirrored so the board will have to be filled front to back, which is NBD other than making it awkward to pre-stuff boards.

It's about 100mm by 44mm. A position for a fuse has been added for the 4 and 5 (lacking any other fuse) that can be jumpered. The current design will accept PTCs or 4.7R resistors, and has positions for MOVs that are optional. Self-bias is theoretically just an "air-wired" resistor away (adding a position for this resistor on the board seems awkward at this juncture). For cheap b*stard DIYers like myself it may be possible to reuse some components from the original board. Accessing the center taps on SRD-4 transformers is of course a delicate surgery but I 100% plan to convert my SRD-4 into a self-pro-bias energizer and have an SR-L300 to test that with.

Edit: Received my boards from jlcpcb over the weekend and found out what happens when you forget to generate a file for the back-side solder mask. Whoops! still fine for SRD-5 upgrades i guess.

Edit: This no double posting configuration is stupid. Anyway, after ordering more capacitors that i had assumed i already had on hand, i got one built up. I loathe my design for various reasons but it seems to work. Ish. A pair of 100v zeners (or a p6ke100 TVS, I checked) gives 90 vac, and the bias voltage isn't where it should be because of that. Ordering more zeners. Final design will probably use the TVS diode. It's a common enough commodity. I will be deleting the positions for MOVs or PTC thermistors from the next revision as well, which might make the board even smaller. Then again i might space out the power resistor footprints so that srd-5 resistors can be reused.

 

[ericj]

smacked my forehead and reminded myself that i have an unmolested srd-7 as well. Measuring the AC across the Z1082 that are in these (as opposed to the z1100 in the Pro and Mk2 schematics) shows 86vac, confirming that the old parts were marked with their clamping voltage, rather than the zener voltage that modern parts are marked with. These are two different voltages. Switching to the P6KE110 gives 100vac in the new board, and 220vdc at the output resistor for normal bias. The pro bias resistor shows about 500vdc, but it could be that my DVM is loading it down too far. I'll build up another board to try self-bias. The next revision will just take the P6KE110 rather than two zeners, and i think will have a separate through-hole for fused vs. unfused power instead of requiring a jumper across the fuse position when not needed.

 

[icnaiwhimor1975]

The topic name is strange, stax doesn't have a "Entry Level")

 

[ludoo]

The topic name is strange, stax doesn't have a "Entry Level")

I beg to differ: old Staxes, especially the SR-X and SR-5 (round drivers FTW!) can be had for very little money. I don't think I ever paid more than 120 euros for an SR-X pair and several cost less than 50, and I think I have 10 or so around (mk1, mk2, mk3), And to my ears they sound better than any Lambda model I have or have had.

Used energizers are also cheap, with some patience and perseverance you could set up a very nice system for 250-300 euros.

 

[ericj]

The topic name is strange, stax doesn't have a "Entry Level")

It does if you're buying vintage.

And my current project will help people put off the expense of a dedicated amp if they're interested in a little diy and have a speaker amp - even a weaksauce speaker amp - that they like. The energizer transformers don't need much current. normal bias SRD-7s are plentiful and can be had around $100. SRD-4 for as little as $50 shipped, though accessing the center taps on the transformers in the 4 is delicate surgery. Granted it only has a single output jack and it's a 5-pin, and there's no AC inlet. But you can add your own AC, or run it self-biased. I suspect that nearly all normal-bias stax don't actually need the center pin connected, i will probably design a 3d printable drill guide.

There's an SR-X (possibly Mk1?) bundled with an SRD-5 at that foreign auction site right now, in kinda rough shape, that may or may not work, but will probably go cheap. Probably cost $50 to import it though.

I got my SRM-1/Mk-2 w/ an NB lambda for about $300 all in. Did need minor rewiring for US power. Spent $20 or so replacing capacitors.

 

[ericj]

Revised my layout, accidentally made it single-sided again so home etch and drill is a possibility i guess. and made it a little smaller than my recent prototype.

The line of hookup points at the top is designed to follow what Stax did in the SRD-7 mk1. So that you can mostly just move a wire from the original board to the new one. SRD-4, 5, and 6 of course will be a little different.

Cap footprints are for Wima MKS4 which turn out to be the most economical film cap for the job, at least from mouser and similar. These must be rated at least 160v. There are some ceramic caps that probably work just as well but if you are buying them from mouser or similar you save about a dollar by using them.

Should be possible to reuse resistors from OG boards (though be aware that the ballast resistors for bias used to be 2.2M and are now 4.7M). The OG resistors *may be less magnetic than new, so it's not necessarily just an option to be cheap.

I'll probably change the silkscreen for the P6KE110 because the package sure doesn't have a stripe on it, because it works the same either way.

The odd spacing between the power resistors is because the mounting brackets in the SRD-5 are really tall for some reason. In fact, how the board gets mounted is the one thing i don't like about the SRD-5. Well, it also has smaller iron than the 7, bigger than the 4. But this is not a big deal if it's between throwing a board into a $50 SRD-4 or trying to track down a real SRD-7 Mk2 or Pro, or buying an amplifier.

I want to do some more testing with the prototype (i haven't actually listened to music through it yet lol) but i will probably send this out for a small batch soon.