The Entry Level Stax Thread

[miceblue]

I substituted the adapter with another much more powerful PS. Same result. The distortion is also much more pronounced on the left side. This means either my amp is somehow defective, or the srm-252s is simply a very weak amp. The latter would be surprising, since I haven't read in any Stax thread that the srm-252s would struggle to drive a mere lambda.

It sounds like your amp is defective. My DAC outputs 2.1 Vrms and I barely have to use the SRM-252S past 10 o'clock for most of my music. If I decrease the DAC volume so that I can use the SRM-252S past 2 o'clock, I still don't hear any distortion through my SR-207.

What the meaning of each pin in stax headphone connector.

STAX systems are balanced by nature, so the pinout of the Pro-Bias is: L+/L-, R+/R-, 580 V bias voltage.

The Normal-Bias one is: L+/L-, R+/R-, 230 V bias voltage L/230 V bias voltage R.

can I use the electrostatic connector for my regular headphones?

Are you planning to Jerry-rig an XLR headphone to a STAX amp or something? That seems like a very bad idea, and completely unnecessary if it even is possible.

 

[JimL11]

I having an old type amps:
the Beyerdynamic n1000 (temporary without the fuse ) and Stax SRD-4
for Beyerdynamic et1000 and Stax SR-30

I want to convert the et1000 6pin din to Stax connector if its possible.

The SRD-4 is designed to drive the Stax electrets (such as the SR-30), which do not need a bias supply, so you would have to install a bias supply in that to use it with any non-electret Stax headphones.

There isn't much info on the N1000 but apparently it uses a 180V bias supply, whereas the Stax 6 pin (normal bias) headphones use a 230V bias supply so it may not work optimally with Stax normal bias phones.

The modern Stax headphones are all pro bias, which is 580V, so you would have reduced sensitivity using the N1000 box. Best to use the SRD4 with the SR30 and N1000 with ET1000. If you want to drive a pro bias Stax headphone it is best to get an SRD-7 Pro, or convert an SRD-7 to pro bias for one of the sockets, or use a Stax amplifier. Unless all you are interested is getting some noise out of the headphones for the absolute possible cheapest price and don't care all that much about quality.

 

[legopart]

The SRD-4 is designed to drive the Stax electrets (such as the SR-30), which do not need a bias supply, so you would have to install a bias supply in that to use it with any non-electret Stax headphones.

There isn't much info on the N1000 but apparently it uses a 180V bias supply, whereas the Stax 6 pin (normal bias) headphones use a 230V bias supply so it may not work optimally with Stax normal bias phones.

The modern Stax headphones are all pro bias, which is 580V, so you would have reduced sensitivity using the N1000 box. Best to use the SRD4 with the SR30 and N1000 with ET1000. If you want to drive a pro bias Stax headphone it is best to get an SRD-7 Pro, or convert an SRD-7 to pro bias for one of the sockets, or use a Stax amplifier. Unless all you are interested is getting some noise out of the headphones for the absolute possible cheapest price and don't care all that much about quality.

I want to order the "Stax SR Lambda" and "Stax SRD7SB" amp, can I convert this amp to pro one? how?
can "Stax SR Lambda" could runs on SRD4 ?
which pads can you recommend for this model?

another not professional question, can I connect my regular amplifire or pre-amp to the input of Stax/Beyerdynamic amps (that required speaker input)?

this is the info that I found for the et1000

ET1000 Headphones
Working Principle： Electrostatic
Frequency Response： 10-25.000 Hz
Sensitivity at 1 kHz with a signal voltage of 2 V： 100 dB SPL (2 Pa) +/- 3 dB
Maximum output level： 115 dB SPL (11,2 Pa) - 3 dB
Maximum output level at THD ≦ 1% and at 1 kHz： 110 dB SPL (6,3 Pa)
Average pressure on ear (DIN)： 2,7 N
Weight w/o cord： 370g (0.81 lbs)
Cord： 2.5m with 6 pin DIN plug

N1000 AC Power Supply
Frequency Response： 10-25.000 Hz + 1.5 dB
Maximum input at 1 kHz (THD < 1%)： 8 V
Distortion at Ui ≦ 4 V, f = 1 kHz： ≦ 0.1 %
Voltage transfer： 1:25
Connection to amplifier outputs： 4-8 ohms
Power requirements： AC 110 or 240 V, 50 or 60 Hz
Weight： 1250g (2.75 lbs)
Dimensions： 203 x 44 x 90 mm (7.99 x 1.73 x 3.54 inches)

Release date： 1976

thanks, for all the help!

 

[JimL11]

I want to order the "Stax SR Lambda" and "Stax SRD7SB" amp, can I convert this amp to pro one? how?
can "Stax SR Lambda" could runs on SRD4 ?
which pads can you recommend for this model?

another not professional question, can I connect my regular amplifire or pre-amp to the input of Stax/Beyerdynamic amps (that required speaker input)?

this is the info that I found for the et1000



thanks, for all the help!

The SRD7SB uses the amp to power the bias (SB = self bias) and I would not recommend it. Also it is normal bias only. Only the SRD-7 Pro has a pro bias supply, unless you can build a pro bias supply and install it in a normal bias energizer such as an SRD-7. There are several Stax Lambda headphones, all but the very earliest ones are Pro bias - you can determine whether it is pro or normal bias by the number of pins it has. All the normal bias headphones have a 6-pin connector, all the Pro bias headphones have a 5-pin connector (no center pin). The Stax and Beyer boxes are NOT amps, they are transformers and contain a bias supply. You have to connect a power amp to drive them - a preamp does not have enough voltage or current output to drive them.

The SRD-4 will NOT run a Stax SR Lambda because it is not an electret headphone.

 

[tigon_ridge]

Um...so I just measured the bias of my amp to be 325V. The bias pin is the one located at around 5 o'clock, from the perspective of looking at the female connector on the amp. Isn't the correct voltage supposed to be 580V? Could this be the reason for my problem?

The bias voltage also affects the current amplitude, correct? Would it be correct to say I'm getting (325/580)^2 = 31% the amount of power the amp is supposed to be outputting?

Measuring the max V r.m.s, I'm getting 207V with the volume knob turned all the way up while playing a 1kHz sine wave. Not quite close to the specified rating of 280V r.m.s.

 

[Tinkerer]

You cant measure bias from the jack. You have to measure behind the ballast resistor. That's where it will read 580. Probias at the jack should be around 300-something with the drop from a regular multimeter, which is what you're getting. What it sounds like to me is something giving out in the channel or you have balance/offset borked in the channel. I've driven 007's off an old Xh (daddy of the 252) with no problems so it's not the base amp design. It's something in the problem channel itself.

What's your balance and offset look like for both channels with the amp warmed up? Do you see a jump in offset on the channel when you hear distortion (that's usually a leaky resistor or a cap giving out) Remember it's a balanced amp by nature too, so if only half the channel is running because something gave out, you'll still get sound, just lower and distorted.

 

[Kitchener]

Just received some new custom made earpads from Vesper Audio for my L500.
They're dark brown leather, 'cause black is boring.
Thick, yes. 2 cm thick to be precise. I should probably have had them made a little thinner, to avoid straining the headband but I'm sure it'll be fine.
Comfort, yes they have it.
Audible improvements, naaah.
Set me back $90 (could have saved $18 by choosing a standard color but I wanted dark brown damnit), well worth it I'd say.

 

[legopart]

The SRD7SB uses the amp to power the bias (SB = self bias) and I would not recommend it. Also it is normal bias only. Only the SRD-7 Pro has a pro bias supply, unless you can build a pro bias supply and install it in a normal bias energizer such as an SRD-7. There are several Stax Lambda headphones, all but the very earliest ones are Pro bias - you can determine whether it is pro or normal bias by the number of pins it has. All the normal bias headphones have a 6-pin connector, all the Pro bias headphones have a 5-pin connector (no center pin). The Stax and Beyer boxes are NOT amps, they are transformers and contain a bias supply. You have to connect a power amp to drive them - a preamp does not have enough voltage or current output to drive them.

The SRD-4 will NOT run a Stax SR Lambda because it is not an electret headphone.

Can I mod the bias by myself?

I ordered something like this one (only with SRD-7/sb amp) https://www.ebay.com/itm/STAX-Ear-speaker-SR-Beauty-goods-adapter-SRD-6-SB/173516586170?_trkparms=aid=111001&algo=REC.SEED&ao=1&asc=20160727114228&meid=bdcdf78b32454bbdbff5dddfa6078ce7&pid=100290&rk=3&rkt=4&sd=253862177136&itm=173516586170&_trksid=p2060778.c100290.m3507

again. pro bias is the oldest one (for SRD-7/sb ?) and normal is more modern ?


Is it possible to connect the n1000 to some SRD amp?

 

[tigon_ridge]

You cant measure bias from the jack. You have to measure behind the ballast resistor. That's where it will read 580. Probias at the jack should be around 300-something with the drop from a regular multimeter, which is what you're getting. What it sounds like to me is something giving out in the channel or you have balance/offset borked in the channel. I've driven 007's off an old Xh (daddy of the 252) with no problems so it's not the base amp design. It's something in the problem channel itself.

What's your balance and offset look like for both channels with the amp warmed up? Do you see a jump in offset on the channel when you hear distortion (that's usually a leaky resistor or a cap giving out) Remember it's a balanced amp by nature too, so if only half the channel is running because something gave out, you'll still get sound, just lower and distorted.

Measured both offset and balance to be very close to <.5V after warming up. These pots are very sensitive; the most minor adjustment can change the value by a volt. They're also not labeled, so you have to play around to figure out which is the offset, and which is the balance.

By connecting the common lead to earth ground, and the other lead to each of the 4 non-bias jacks, I sine-swept at 1 kHz and measured over 10mA and approx 140V, with volume pot at max, from each jack. 140V * 2 = 280v per channel. (Couldn't get 280V before, because I had the EQ on). The point at which music begin to distort is around 12:45 o'clock, and 12:15 is around where it reads 1.2mA, which was what Jim told me the srm-252s is capable of moving. Based on all these measurements, can I say the amp is in good working order?...unless there's something I'm missing or not understanding. Anyways, it's been fun messing around and learning about my new toys. I hadn't gotten a chance to use my meter in a while. My conclusion so far is that my EQ is the main thing making me crank up the pot.

 

[JimL11]

Measured both offset and balance to be very close to <.5V after warming up. These pots are very sensitive; the most minor adjustment can change the value by a volt. They're also not labeled, so you have to play around to figure out which is the offset, and which is the balance.

By connecting the common lead to earth ground, and the other lead to each of the 4 non-bias jacks, I sine-swept at 1 kHz and measured over 10mA and approx 140V, with volume pot at max, from each jack. 140V * 2 = 280v per channel. (Couldn't get 280V before, because I had the EQ on). The point at which music begin to distort is around 12:45 o'clock, and 12:15 is around where it reads 1.2mA, which was what Jim told me the srm-252s is capable of moving. Based on all these measurements, can I say the amp is in good working order?...unless there's something I'm missing or not understanding. Anyways, it's been fun messing around and learning about my new toys. I hadn't gotten a chance to use my meter in a while. My conclusion so far is that my EQ is the main thing making me crank up the pot.

Sounds like the amp is working to spec. If you are using EQ in addition, no wonder you are having problems. Remember that 3 dB of EQ, which is a relatively modest amount, means you are doubling the power demand at those frequencies. If you are boosting the bass, you are going to run out of headroom in a hurry.

 

[JimL11]

Can I mod the bias by myself?

I ordered something like this one (only with SRD-7/sb amp) https://www.ebay.com/itm/STAX-Ear-speaker-SR-Beauty-goods-adapter-SRD-6-SB/173516586170?_trkparms=aid=111001&algo=REC.SEED&ao=1&asc=20160727114228&meid=bdcdf78b32454bbdbff5dddfa6078ce7&pid=100290&rk=3&rkt=4&sd=253862177136&itm=173516586170&_trksid=p2060778.c100290.m3507

again. pro bias is the oldest one (for SRD-7/sb ?) and normal is more modern ?


Is it possible to connect the n1000 to some SRD amp?

You have it backwards. The normal bias is old, the Pro bias is new. Stax stopped building adapter boxes decades ago, that is why most of the adapter boxes on sale only have normal bias. Only the SRD-7 Pro adapter box, which is the newest, has the Pro bias. You either have to buy a pro bias circuit board from spritzer, if he has any for sale, and then build it, or you have to build one from scratch. It's a relatively simple mod - basically a Cockroft voltage multiplier circuit using diodes and capacitors, but you have to know what you are doing, i.e. you have to know which way to orient the diodes. In addition, the SRD boxes do not have an isolation transformer for the bias supply so that the supply is connected directly to the AC power line, which could have lethal consequences if the builder is careless and somehow causes the power line to be connected to the box.

All the Stax SRD boxes are adapters, just like the n1000, and require a speaker power amp to work. They are NOT amplifiers. If you look inside them, you will find two passive step-up transformers to step up the voltage from a speaker amp to the levels needed to drive the headphones, and a bias supply. Only the bias supply is connected to the AC power line. In the Stax SB adapters, the bias supply is connected to another transformer that is driven by the speaker amp so there is no AC power connection. The problem with the SB units is that when you start playing music, it takes time for the bias supply to power up because the music signal actually supplies the voltage to boost the power supply, which means that the box is not fully working for at least the first few seconds of music. That is why I do not recommend the SB units.

The SRD-4 box doesn't have a bias supply because it is only intended to be used for the Stax electret headphones, which have their diaphragm permanently charged, hence the term electret.

Since the n1000 and SRD are both passive adapter boxes, connecting the two together won't do anything, just like connecting two passive cables won't power anything.

All the Stax SRM are amplifiers - they have a power supply and use transistors and/or tubes to actively enlarge the signal from a source. Don't confuse adapters and amplifiers.

I suggest you do a bit of reading, researching and thinking before asking more questions.

 

[tigon_ridge]

You have it backwards. The normal bias is old, the Pro bias is new. Stax stopped building adapter boxes decades ago, that is why most of the adapter boxes on sale only have normal bias. Only the SRD-7 Pro adapter box, which is the newest, has the Pro bias. You either have to buy a pro bias circuit board from spritzer, if he has any for sale, and then build it, or you have to build one from scratch. It's a relatively simple mod - basically a Cockroft voltage multiplier circuit using diodes and capacitors, but you have to know what you are doing, i.e. you have to know which way to orient the diodes.y charged, hence the term electret.

Incidentally, I just recently watched David Jones's lecture/presentation on his EEVblog youtube channel explaining the Cockroft-Walton voltage multiplier. I remember thinking after watching that video, "Eureka! Could this be how the bias on an electrostatic amp is made??" Thanks for confirming, Jim!!!

 

[legopart]

You have it backwards. The normal bias is old, the Pro bias is new. Stax stopped building adapter boxes decades ago, that is why most of the adapter boxes on sale only have normal bias. Only the SRD-7 Pro adapter box, which is the newest, has the Pro bias. You either have to buy a pro bias circuit board from spritzer, if he has any for sale, and then build it, or you have to build one from scratch. It's a relatively simple mod - basically a Cockroft voltage multiplier circuit using diodes and capacitors, but you have to know what you are doing, i.e. you have to know which way to orient the diodes. In addition, the SRD boxes do not have an isolation transformer for the bias supply so that the supply is connected directly to the AC power line, which could have lethal consequences if the builder is careless and somehow causes the power line to be connected to the box.

All the Stax SRD boxes are adapters, just like the n1000, and require a speaker power amp to work. They are NOT amplifiers. If you look inside them, you will find two passive step-up transformers to step up the voltage from a speaker amp to the levels needed to drive the headphones, and a bias supply. Only the bias supply is connected to the AC power line. In the Stax SB adapters, the bias supply is connected to another transformer that is driven by the speaker amp so there is no AC power connection. The problem with the SB units is that when you start playing music, it takes time for the bias supply to power up because the music signal actually supplies the voltage to boost the power supply, which means that the box is not fully working for at least the first few seconds of music. That is why I do not recommend the SB units.

The SRD-4 box doesn't have a bias supply because it is only intended to be used for the Stax electret headphones, which have their diaphragm permanently charged, hence the term electret.

Since the n1000 and SRD are both passive adapter boxes, connecting the two together won't do anything, just like connecting two passive cables won't power anything.

All the Stax SRM are amplifiers - they have a power supply and use transistors and/or tubes to actively enlarge the signal from a source. Don't confuse adapters and amplifiers.

I suggest you do a bit of reading, researching and thinking before asking more questions.

I would like to read more, can you suggest me more links about it?
1- I cant find any guide for et1000/ n1000 amo
2- how to mod SRD amp to have a bias connection or create this amp by myself
3- how can I measure the bias voltage (between which pins), so I could decide if the amp working fine before I connect the headphones {or to know if this headphones fit to this amp}

again, thanks for the information!




I was amazed on my SR-40 that it's sounds only from one connection on it (without use the the - side of the cable)

I understood that the bias turn on the magnet on electrostatic headphones,
Soo if I connect the electrostatic headphones to SRD amp then it's may works a little bit but still not strong and good enoth.

ET1000 is electrostatic headphones they have connection to the electricity
the fuse of 32mA 240v is blown and for this moment I not having the replacement.
I searching for information about this item (n1000) because I think that there are more things to fix inside
{or maybe I will order another headphones in the futur that will use this or SRD amps}

https://i.imgur.com/xiDBmgU.jpg





Can another amp for cheaper price run Stax electrostatic headphones?

 

[JimL11]

I would like to read more, can you suggest me more links about it?
1- I cant find any guide for et1000/ n1000 amo
2- how to mod SRD amp to have a bias connection or create this amp by myself
3- how can I measure the bias voltage (between which pins), so I could decide if the amp working fine before I connect the headphones {or to know if this headphones fit to this amp}

again, thanks for the information!




I was amazed on my SR-40 that it's sounds only from one connection on it (without use the the - side of the cable)

I understood that the bias turn on the magnet on electrostatic headphones,
Soo if I connect the electrostatic headphones to SRD amp then it's may works a little bit but still not strong and good enoth.

ET1000 is electrostatic headphones they have connection to the electricity
the fuse of 32mA 240v is blown and for this moment I not having the replacement.
I searching for information about this item (n1000) because I think that there are more things to fix inside
{or maybe I will order another headphones in the futur that will use this or SRD amps}

https://i.imgur.com/xiDBmgU.jpg





Can another amp for cheaper price run Stax electrostatic headphones?

1) Don't be lazy, start with Google search.

2) Please stop saying amp when you mean adapter. An amp is an amp, and an adapter is an adapter, they are not the same thing. To repeat myself, all the Stax SRD units are ADAPTERS, as is the n1000.

3) No, the bias does not turn on a magnet. Electrostatic headphones use a completely different principle.

 

[legopart]

now I see.
I still having an issue to find information about it.
I understand that the down part, transformer and the electric parts, is the bias supplayer.
If I build one I can add It to each adapter to this pin (looks like heavy voltage for one cable)

but although the n1000 having AC connector to 230v, but I cant see how it's transform and use on the headphones.
I found nothing on this moment about the n1000, and without the fuse and the connection to the AC.
Its sound creepy and distorted.

I really hoped to get some help, cause no one work, use this things anymore.