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The Headcase Stax thread


thrice
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For the SRD style transformer boxes like the Woo WEE, SRD-7 and of course Spritzer's take on the SRD-7, what determines the current output? The voltage is simple step up operation, but most good electrostatic amps are designed to output large amounts of current, so what holds these transformer boxes back from competing with "real" amplifiers assuming the power amplifier is of high quality? To rephrase, if someone was getting into Stax and already had a great power amp, at which point would it just make more sense to go for a standalone amplifier?

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A perfect transformer doesn't exist and they usually have a lot of capacitance which adds to the load and thus...loss.  Bunch of other issues as well but for a budget setup, transformers work well and are easier than ever to use with all the excellent chip amps out there.  Well not the Wee...all the ones I've seen have a shared negative which will blow up the amps... 

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I’m in a quandary over the next amplifier step. My SRM-1/Mk2 is no younger than 24 years, because I believe production was ended in 1995. (It has two probias sockets, if that helps dating.) It hasn’t hasn’t been recapped & rebiased. I’m considering a 47-step Goldpoint for it & new RCA jackets. If I have the work done, it’ll be over $500. The SRM came out of a studio & cost around $450. It sounds great & has been very reliable for the six months I’ve had it. It drives SR-207 & SR-507 stats.

 

The three options are:

1) Refurb the SRM-1/Mk2;

2) Buy a new SRM-353X; and,

3) Buy a transformer box, buy a Class D Audio brand Mini Amp board (which I’ve used), and use my Goldpoint attenuator.

 

2) seems more reasonable over 1) since the 353X is new- production. Which sounds better? I would have put about $1000 USD into an amp that is at least 24 years old while a new SRM-353X is about $1000 itself. 3) is attractive since I’d be customizing the rig from the ground-up. I would buy one of Spritzer’s SRD-7 boxes. This rig would cost me about $800 to $900. Importantly, I don’t listen to speakers anymore, so the Class D amp would be used exclusively for the Stax.

 

What direction should I pursue?

Edited by Sisterray
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The SRM-353X certainly superior to the SRM-1 Mk2 but it all comes down to value.  The cost in parts of refurbishing the SRM-1 Mk2 is far lower and the difference between the two isn't all that big.  I personally prefer the direct drive amps and with a transformer the cost is really high too due to the stepped attenuator. 

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It is, indeed, a matter of value. Then it comes down to whether an amp that is nearly 25 years old is worth updating. I am concerned about components failing that I am not qualified to troubleshoot & replace. Recapping & rebiasing are things I can do, but I think a new amp is in order.

Thnaks for putting things into perspective.

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What relevant specs distinguish the performance of the SR-507 from that of the SR-207? I recently acquired a 507 pair & did a comparison using the twin sockets on an SRM-1/MK2. The phrase that popped into mind after a few minutes of comparing the two was “dirty windshield”, the dirty windshield being the 207s. Of course, this was obvious when comparing the two. By itself, the 207s are outstanding when placed up against electrodynamics & wipe the floor with the latter. The 507s beat the other pair in clarity & bass definition. Voices are better defined & percussion is more detailed, “wetter”, deeper-sounding. Is the thinner diaphragm responsible? I do want to do more testing before selling the 207s. I have a better amp to buy. ;}

I got the 507s at an outstanding price, brand new. The build quality & comfort are significantly better than those of the 207s. I highly recommend them.

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Personally I found it had absolutely no lower midrange to speak of. So despite having good bass extension it sounded horrifically thin. The top end was also like razor blades to my ears, which was a first for me. I actually tried a high-shelf EQ filter where i took down everything from 2k down by 5dB and it still sounded bright. I feel like there has to be some kind of odd order distortion going on, but measurements by Tyll show none of that. Those measurements also show an ok frequency response though, which was definitely not my experience.

For reference I tried it on 006t, SRD-7 with a speaker amp and my KGSSHV. Sounded bad on all of them.

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I have a large noggin. Use the L500/L700/009S style headband at 7-8/10 clicks. The 507 is the most comfy lambda I've tried honestly. Only shortcoming is the ear opening could stand to be a few millimetres deeper. I also think it feels more sturdy than the advanced lambda series with their McDonalds plastic.

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Question: How does the SR-Lambda (NB) change when the foam in the front and wool stuff in the back is removed? I have a normal bias lambda and I finally got around to fixing some balance issues with it. It has no damping in front of or behind the driver (removed by earlier owner). I'm assuming the stuff in the back of the driver has less of an effect on the response than the foam in the front.

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Damn it, I was reading these posts and I have been wanting to listen to my Lambda Pro.

Everything was correct until I realized that they are starting to make a strange "pop" from time to time. Left or right driver and  I think it happens when my ears brush the drivers.

What do you think it can be? Will you need a pad change?

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On 8/8/2019 at 3:28 AM, kevin gilmore said:

Ok, the stax mafia has spent quite a bit of time with the kse1500

first the headphones are 200v bias. The kingsound must have been modified to lower bias voltage otherwise these headphones will eventually pop.

yes the kse1500/kse1200 is an extremely low power classAB amplifier with significant distortion. But great battery life. 

The kingsound is a chip amp driving transformers. Might actually sound better, but definitely not stax mafia approved.

A really good battery powered portable electrostatic amp is harder than you might think.

The stax d10 is another example that has issues.

A KSE1500 desktop amp would be great :P 

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Getting parts from Stax turned out to not be a pain! I had to go through my country's Stax importer but it was a pretty painless process so now new wool and 234BL earpads are on the way! I was wondering about the resistors/thermistors/whatever in the earcups though. What is their function? Current limiting the stators? Could they become an issue with time? I'm refurbing this pair of lambdas to be as nice as possible, so I'd like to remove/replace them if that is necessary when I open the headphones.

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