Need a little help here.
To cut a long story short.
A friend asked me to look at his headphone gear. Stax 007 and SRM-T1S headphone amp. The story is, that this
never worked as expected. And he´s right. The sound is dull, boring and nowhere near, what you would expect from STAX.
He hiself had replaced the tubes and all the elctrolytic cap´s. This made no difference.
Visited another firend, who has a set of Lambda phones and an older solid state Stax headphone amp.
On his setup, the 007´s sound perfect. A slight more laid back than the Lambda´s but totally acceptable. On the SRM-T1S far from as good.
So I´m confident, the error must be in the SRM-T1S
Can´t see or measure any faults in the circuit........... other than maybe this one..........
People write, that the bias voltage is 230V for normal and 580V for Pro.
Where to measure this??
No matter if I measure from L-, R-, L+, L- or ground to bias in the plug I end up with approx. 150V in the normal plug or 360V on the Pro.
I called the Lambda guy and asked him to measure his amp, and he got the same results....... 160V vs. 355V.
Am I on thin ice here, or is this measurement taken between "bias" and some unknown ref.??
I only have a really bad copy of the schematics, so if anyone can scan the org. service manual from Stax, it would be very much appreciated.
I found the adjustments on Headfi.org and adjustments are done within less than 1 Volt (Stax acceps +-15 or less).
Thanks in advance for any info...... and no...... I´m not gonna convert it according to the CCS mod´s 😉
To cut a long story short.
A friend asked me to look at his headphone gear. Stax 007 and SRM-T1S headphone amp. The story is, that this
never worked as expected. And he´s right. The sound is dull, boring and nowhere near, what you would expect from STAX.
He hiself had replaced the tubes and all the elctrolytic cap´s. This made no difference.
Visited another firend, who has a set of Lambda phones and an older solid state Stax headphone amp.
On his setup, the 007´s sound perfect. A slight more laid back than the Lambda´s but totally acceptable. On the SRM-T1S far from as good.
So I´m confident, the error must be in the SRM-T1S
Can´t see or measure any faults in the circuit........... other than maybe this one..........
People write, that the bias voltage is 230V for normal and 580V for Pro.
Where to measure this??
No matter if I measure from L-, R-, L+, L- or ground to bias in the plug I end up with approx. 150V in the normal plug or 360V on the Pro.
I called the Lambda guy and asked him to measure his amp, and he got the same results....... 160V vs. 355V.
Am I on thin ice here, or is this measurement taken between "bias" and some unknown ref.??
I only have a really bad copy of the schematics, so if anyone can scan the org. service manual from Stax, it would be very much appreciated.
I found the adjustments on Headfi.org and adjustments are done within less than 1 Volt (Stax acceps +-15 or less).
Thanks in advance for any info...... and no...... I´m not gonna convert it according to the CCS mod´s 😉
You should measure referenced to ground. There is no ground connection in the plug. Only bias and positive and negative output.
Hope this helps.
Hope this helps.
Me too.
I do know from someone who built his own 'STAX' amp is that the exact bias voltage isn't very critical. But the difference you have is way beyond that.
That´s what puzzles me.
On this one here, SRM-T1s, the 007´s sound dull and awfully boring.
On my friends older Solid State Stax headphone amp, they sound just gorgeous.
And he measures the same bias voltage on his, as I do on the T1s 😳
The bias supply has a very high output impedance, so your DMM loads the bias supply and drags it down. The voltages you see are pretty consistent with what I have seen and what others report, so probably not where the problem is.
EDIT: Better explanation here: https://www.head-case.org/forums/topic/21842-stax-t1w-bias-voltage/
EDIT: Better explanation here: https://www.head-case.org/forums/topic/21842-stax-t1w-bias-voltage/
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Ever got to the bottom of this? Which amp does your friend use?
Also, simply hooking up a DVM between BIAS and GND will indeed not work to measure the BIAS voltage (as mentioned above). You'll need a very high-ohmic resistor between the BIAS output and the DVM input, and then convert the DVM reading according to the voltage divider formed by the high-ohmic resistor and the internal resistance of the DVM. See here and follow-up posts.
To answer in reverse order.
I realized the impedanxe problem and yes... found out that this could only be measured with a good old fashioned tube-voltmeter.
No...... gave up and returned the set to my friend. Everything I tried measuring, components, swapping to different tubes etc. did
not make the slightest difference. Now I´m happy and have forgotten all about it 👍
I realized the impedanxe problem and yes... found out that this could only be measured with a good old fashioned tube-voltmeter.
No...... gave up and returned the set to my friend. Everything I tried measuring, components, swapping to different tubes etc. did
not make the slightest difference. Now I´m happy and have forgotten all about it 👍