Hi Bart,
I'm also looking for replacing tubes on my Stax SRM-007Ta and I wonder if you've managed to find some information on that...?
I think there is an option to replace original 6FQ7/6CG7 tubes with 6S4A tubes, but that will require rewiring and soldering work, for which some schematics and instructions will be needed.
Please advise,
Sasa
I'm also looking for replacing tubes on my Stax SRM-007Ta and I wonder if you've managed to find some information on that...?
I think there is an option to replace original 6FQ7/6CG7 tubes with 6S4A tubes, but that will require rewiring and soldering work, for which some schematics and instructions will be needed.
Please advise,
Sasa
Hi Sasa,
6FQ7/6CG7 are popular tubes, so no reason to use something else. A 6S4A is a single triode with different characteristics so you're looking at more than rewiring sockets. Then you'd have to redesign the circuit for the other characteristics.
Just use the intended tubes. Many audio amplifiers use them.
-Chris
6FQ7/6CG7 are popular tubes, so no reason to use something else. A 6S4A is a single triode with different characteristics so you're looking at more than rewiring sockets. Then you'd have to redesign the circuit for the other characteristics.
Just use the intended tubes. Many audio amplifiers use them.
-Chris
Thanks for a straightforward reply, Chris.
I'm new user of both Stax headphones (or "earspeakers") and Stax amp (or "energiser"), which is also my first tube-based audio equipment.
The main reason I asked about tube replacement is that, in order to have decent sound levels on my Stax 009 headphones, I have to adjust level on my Stax SRM-007Ta amp with 6FQ7/6CG7 tubes pretty high (around 8-9 out of 10, with the pre-amp also around the same level), and that the existing tubes are reaching the end of their lifetime.
I don't know if new tubes will provide better output levels, but I'm willing to try -- may I ask, if you know, or have some experience, which of 6FQ7/6CG7 type tube manufacturers you would recommend to buy from, particularly regarding their voltage handling performance?
Thanks again and best regards,
Sasa
I'm new user of both Stax headphones (or "earspeakers") and Stax amp (or "energiser"), which is also my first tube-based audio equipment.
The main reason I asked about tube replacement is that, in order to have decent sound levels on my Stax 009 headphones, I have to adjust level on my Stax SRM-007Ta amp with 6FQ7/6CG7 tubes pretty high (around 8-9 out of 10, with the pre-amp also around the same level), and that the existing tubes are reaching the end of their lifetime.
I don't know if new tubes will provide better output levels, but I'm willing to try -- may I ask, if you know, or have some experience, which of 6FQ7/6CG7 type tube manufacturers you would recommend to buy from, particularly regarding their voltage handling performance?
Thanks again and best regards,
Sasa
Thanks for confirming what Chris suggested, Bart -- yes, I'm using balanced inputs with balanced input signals (from Quad Artera Solus, connected via balanced Linn XLR cables). What is your SRM-007 & headphones set-up, and do you need to adjust higher volume levels on pre-amp and/or Stax amp?
Also, following my question to Chris, which brand/type of tubes you may recommend (or you may have already used?) for replacing the original ones...?
Thanks again and best regards,
Sasa
Also, following my question to Chris, which brand/type of tubes you may recommend (or you may have already used?) for replacing the original ones...?
Thanks again and best regards,
Sasa
Here's (part of) the schematic. What other information do you need?
The "output level" is determined by the gain of the amplifier, which in turn is controlled largely by the amount of global negative feedback. The gain parameter of the tubes does not make a huge difference. If your tubes are worn out, replace them with the intended type.
The max. volume of the "smaller" Stax amps is limited by the power supply voltage and the dissipation limit of the tubes. There are no simple tweaks to change that.
The "output level" is determined by the gain of the amplifier, which in turn is controlled largely by the amount of global negative feedback. The gain parameter of the tubes does not make a huge difference. If your tubes are worn out, replace them with the intended type.
The max. volume of the "smaller" Stax amps is limited by the power supply voltage and the dissipation limit of the tubes. There are no simple tweaks to change that.
I would recommend any new manufacture tube sold by New Sensor. Excellent quality, very consistent tubes. Electroharmonix would be my first choice, although they are all made extremely well from the Reflector factory in Russia.
Low level could also be due to low DC charge voltages. Electrostatics are not efficient either. So if they are truly low in level, have the power supply checked before messing around with anything else.
As for input type. Balanced inputs are normally adapters. Electronic or transformer (each have drawbacks). Most equipment is single ended internally. Balanced connections are for low level signals travelling over distance. Something you want to avoid in the first place. A balanced connection can never be lower distortion than single ended, and may be 1.414 x as noisy as single ended. Now if the designer messed up the design, balanced may be better, but the entire design would be suspect in that case.
Low level could also be due to low DC charge voltages. Electrostatics are not efficient either. So if they are truly low in level, have the power supply checked before messing around with anything else.
As for input type. Balanced inputs are normally adapters. Electronic or transformer (each have drawbacks). Most equipment is single ended internally. Balanced connections are for low level signals travelling over distance. Something you want to avoid in the first place. A balanced connection can never be lower distortion than single ended, and may be 1.414 x as noisy as single ended. Now if the designer messed up the design, balanced may be better, but the entire design would be suspect in that case.
Not so with Stax / e-stat amps. They need to drive both stators with opposite polarity, so they need a phase splitter anyway before the output stage. If I remember correctly, the Stax amps use a long tail at the input, with no internal conversion to single ended.
That could be as far as inputs are concerned. I thought they drove the panels differentially.
By in large, most equipment that has balanced inputs and outputs use adapters. The actual circuit is single ended. If the circuit is duplicated (true balanced design) it will have 1.414 x the noise of a single path amplifier. It would be 2x except the noise is random and uncorrelated.
By in large, most equipment that has balanced inputs and outputs use adapters. The actual circuit is single ended. If the circuit is duplicated (true balanced design) it will have 1.414 x the noise of a single path amplifier. It would be 2x except the noise is random and uncorrelated.
Thanks to all for your kind replies, for provided partial schematic (is there maybe a full schematic somewhere?) and for indeed useful suggestions -- may I please check following couple points:
1. I've found a UK-based supplier of Electro-Harmonix (New Sensor) tubes and have already made an order. As I said before, I'm new with tube amps and I think some "tuning" should be done with the new tubes upon replacing the old ones -- is there some instruction as to how to do that with Stax SRM-007Ta? Will I need a volt-meter and, if yes, what are the points of measurements and values to be adjusted (e.g. on provided schematic)? Based on your previous ecxperiences, should I do this "tuning" only once and immediately after replacing, or I should wait some time and then do it, or repeat/recheck several times, or follow some other procedure?
2. Should I use balanced or single-ended inputs? I will of course do my own hearing tests and A-to-B comparisons, but I'm now curious if Stax SRM-007Ta is fully balanced amp, or it actually converts balanced signals to single-ended ones before amplifying and outputing to headphones?
Best regards and looking forward to your further replies,
Sasa
1. I've found a UK-based supplier of Electro-Harmonix (New Sensor) tubes and have already made an order. As I said before, I'm new with tube amps and I think some "tuning" should be done with the new tubes upon replacing the old ones -- is there some instruction as to how to do that with Stax SRM-007Ta? Will I need a volt-meter and, if yes, what are the points of measurements and values to be adjusted (e.g. on provided schematic)? Based on your previous ecxperiences, should I do this "tuning" only once and immediately after replacing, or I should wait some time and then do it, or repeat/recheck several times, or follow some other procedure?
2. Should I use balanced or single-ended inputs? I will of course do my own hearing tests and A-to-B comparisons, but I'm now curious if Stax SRM-007Ta is fully balanced amp, or it actually converts balanced signals to single-ended ones before amplifying and outputing to headphones?
Best regards and looking forward to your further replies,
Sasa
First if all, please understand that this amp uses high voltages that can be dangerous. If you don't know what you're doing, don't do it without help from someone who is competent with this stuff.
After installing the new tubes, adjust the trimmers to get the DC output voltages close to zero (both absolute level and relative imbalance).
After installing the new tubes, adjust the trimmers to get the DC output voltages close to zero (both absolute level and relative imbalance).
Thanks -- yes, I'm aware there is 350V voltage inside the chasis, which can be dangerous (I have degree in electrical engineering and have experience with audio equipment, alas not with tube-based ones).
May I ask where I should measure these voltages and how I could adjust them -- maybe the easisest way is to indicate that on the provided schematic?
May I ask where I should measure these voltages and how I could adjust them -- maybe the easisest way is to indicate that on the provided schematic?
I don't know the diagram of the front stage. Here is an interesting contribution to understanding how the final stage works. Il's in Japanese, but google translate does a good job.
http://www7b.biglobe.ne.jp/~konton/STAX Driver Ver7.htm
http://www7b.biglobe.ne.jp/~konton/STAX Driver Ver7.htm
Many thanks again for your reply.
With apologies for my ignorance, may I please check:
To which exact trimmers you're referring to (are they indicated on the provided schematics)?
After I find them:
Should I do adjustment of trimmers "one at a time", or "alternating between them" to get the DC output voltages close to zero (both absolute level and relative imbalance)?
Also:
Output of the amp are two 5-pin female plugs for connecting the headphones, so I guess you are suggesting to measure voltages between the pins, but may I ask between which pins (and should adjustment go in any particular order, or it does not matter?), and how close to zero these voltages should be so it can be concluded that adjustment should stop?
Thanks again for your patience and help with my questions (which I suspect may be a bit silly for someone experienced in the above matters)
With apologies for my ignorance, may I please check:
To which exact trimmers you're referring to (are they indicated on the provided schematics)?
After I find them:
Should I do adjustment of trimmers "one at a time", or "alternating between them" to get the DC output voltages close to zero (both absolute level and relative imbalance)?
Also:
Output of the amp are two 5-pin female plugs for connecting the headphones, so I guess you are suggesting to measure voltages between the pins, but may I ask between which pins (and should adjustment go in any particular order, or it does not matter?), and how close to zero these voltages should be so it can be concluded that adjustment should stop?
Thanks again for your patience and help with my questions (which I suspect may be a bit silly for someone experienced in the above matters)