Hey there!
I just became the owner of a very wonderful Threshold S/200 optical bias amplifier. It is in great shape, but clearly could use a tune up. I have either a very low hum or maybe a static noise, it's hard to tell. This is through 98db speakers, so they are a bit sensitive. This may just be a limit of the power supply, but I am ready to learn about this amp.
One major issue is the lack of a printed schematic or service manual. It would be extremely helpful for those who need to update their amp as things get out of spec.
Are there any capacitors that fit exactly where the the Mallory caps are? Diameter seems easy, height less so. If I just need to search, I can on Mouser and Digikey. Just hoping for an easy solution.
Is there really any point in replacing the tantalums? Depending on the schematic, they seem to be used just fine.
So far I was able to set cold bias and temp. Both of those readings are good.. Dc offset seems high. I should have recorded them, I will tomorrow.
I realize now that I must get many tests done tomorrow and update this post.
I just became the owner of a very wonderful Threshold S/200 optical bias amplifier. It is in great shape, but clearly could use a tune up. I have either a very low hum or maybe a static noise, it's hard to tell. This is through 98db speakers, so they are a bit sensitive. This may just be a limit of the power supply, but I am ready to learn about this amp.
One major issue is the lack of a printed schematic or service manual. It would be extremely helpful for those who need to update their amp as things get out of spec.
Are there any capacitors that fit exactly where the the Mallory caps are? Diameter seems easy, height less so. If I just need to search, I can on Mouser and Digikey. Just hoping for an easy solution.
Is there really any point in replacing the tantalums? Depending on the schematic, they seem to be used just fine.
So far I was able to set cold bias and temp. Both of those readings are good.. Dc offset seems high. I should have recorded them, I will tomorrow.
I realize now that I must get many tests done tomorrow and update this post.
Congratulations with your purchase. It's a great amp.
As you've found, there are several manufacturers that make the 'right' size caps. Cornell Dubilier and Chemi-Con to mention a few.
You will need to look at bigger values than the originals though, and they might still be a bit shorter than the originals, but that shouldn't be a problem.
I used 2x39mF in an S/200 I refreshed for a friend, without any other changes. Bridge and switch are fine with it.
...and yes, replace the tantalums.
With speakers this sensitive you should expect a tiny bit of hum with these amps. PSU is very basic.
I have heard S/150, S/200, S/300, SA1, 2 and 3, and they all had a tiny bit of audible hum on sensitive speakers.
...but they all sounded great!
As you've found, there are several manufacturers that make the 'right' size caps. Cornell Dubilier and Chemi-Con to mention a few.
You will need to look at bigger values than the originals though, and they might still be a bit shorter than the originals, but that shouldn't be a problem.
I used 2x39mF in an S/200 I refreshed for a friend, without any other changes. Bridge and switch are fine with it.
...and yes, replace the tantalums.
With speakers this sensitive you should expect a tiny bit of hum with these amps. PSU is very basic.
I have heard S/150, S/200, S/300, SA1, 2 and 3, and they all had a tiny bit of audible hum on sensitive speakers.
...but they all sounded great!
Attachments
Sounds like it's universal that the tantalums must go. Do you happen to remember the uF? I'd like to make sure I have the right value laying around. I've always been a fan of removing tantalums, but wasn't sure the reason for them due to no schematic.
If some very mild (like ear about 1.5 feet) hum is detected that sounds normal then. Perhaps the capacitors are still good. I should really just scope it and see exactly what's passing through.
If some very mild (like ear about 1.5 feet) hum is detected that sounds normal then. Perhaps the capacitors are still good. I should really just scope it and see exactly what's passing through.
Well I figured out the hum. There was a splitter for a sub I completely forgot about. The sub had been out of use, but not unplugged. So totally the preamp here.
It appears I must not have measured DC offset, or else this would have been obvious. Today I shorted the inputs on the S/200 and it was silent. Plugged into preamp, noise.
I am slightly concerned about the amount of DC offset:
Right Channel: 66mv
Left Channel: 17mv
Not sure if I should pursue fixing this, as some amps even run higher. I am always glad to take advice.
Bias is still correct, the amp seems to be working well. It would be nice to get the right channel dc offset down though.
Thank you for the help so far!
It appears I must not have measured DC offset, or else this would have been obvious. Today I shorted the inputs on the S/200 and it was silent. Plugged into preamp, noise.
I am slightly concerned about the amount of DC offset:
Right Channel: 66mv
Left Channel: 17mv
Not sure if I should pursue fixing this, as some amps even run higher. I am always glad to take advice.
Bias is still correct, the amp seems to be working well. It would be nice to get the right channel dc offset down though.
Thank you for the help so far!
don't be, everything in bracket of +/-100mV is normal, if steady
just replace small electrolytics and tantalums
considering that there is no hum, you don't exactly need to replace biguns, you can do that whenever you have proper itch
you can go through entire amp and check/tighten bolts/screws, especially those on outputs - thermal cycling is tricky
Good to know. It seems the only capacitors that aren't film, ceramic, or mica is a single tantalum per a side and the two filter capacitors.
I also appreciate the idea of giving the contact point a torque check. These amps are getting a bit long in the tooth and need a little love to keep them at ideal operation.
Well thats a seal of approval. I'll set up my bench to remove them. Luckily there only two.
Does anyone know the uF/voltage? I feel as though film capacitors will fit easily, but want to insure I have the correct ones out of my way too many capacitors
Thank you!
Does anyone know the uF/voltage? I feel as though film capacitors will fit easily, but want to insure I have the correct ones out of my way too many capacitors
Thank you!
I believe I have scrapped up the uF, it appears to be 0.15uF. Those may be laying around, but not sure I have a set. Mouser here I come!
Also, thanks again everyone and Mr. Pass!
Also, thanks again everyone and Mr. Pass!
I chased a hum for a day or two. Turned out one of two DACs, both powered up, but unused ones interconnects not plugged in to preamp...
Hello all,
I have a Stasis S/200 which I tried to swap out the big PS Caps on. Affer all is back together (without the 2 silver Tantalums) there is one small red wire with a eyelet on the end that I cannot remember where it went. It seems to provide power to the little power light on the front. It runs down to the back and right and is connected to a connector strip, then through a resistor, and then goes on between the big caps to the front and up to the little lighit. Does it go under the nut on the positive side of one of the big caps. Also, what was the value of the tantalums as I cannot find where I put them. Is it worth buying a $185 refresher kit on ebay for redo the boards? Do resistors need to be replaced also, or just electrolytic caps?
I have a Stasis S/200 which I tried to swap out the big PS Caps on. Affer all is back together (without the 2 silver Tantalums) there is one small red wire with a eyelet on the end that I cannot remember where it went. It seems to provide power to the little power light on the front. It runs down to the back and right and is connected to a connector strip, then through a resistor, and then goes on between the big caps to the front and up to the little lighit. Does it go under the nut on the positive side of one of the big caps. Also, what was the value of the tantalums as I cannot find where I put them. Is it worth buying a $185 refresher kit on ebay for redo the boards? Do resistors need to be replaced also, or just electrolytic caps?
@Pavlograd: The LED (light) and its series-resistor is connected to one of the PS caps. One eyelet to '+' the other to '-'
I don't know what you mean when you say (without the 2 silver Tantalums).
Some owners have added film-caps to the PS-caps, but I seriously doubt tantalums were ever used for this, and it was definately not factory.
No need to change anything but the electrolytics.
If you really want to 'refresh' the magic, the only right way is to build the new stasis frontend made by the man himself. If not, leave it as is. No 'refresher-kits'... please.
Note: There are at least 3 different versions of the S/200.
I don't know what you mean when you say (without the 2 silver Tantalums).
Some owners have added film-caps to the PS-caps, but I seriously doubt tantalums were ever used for this, and it was definately not factory.
No need to change anything but the electrolytics.
If you really want to 'refresh' the magic, the only right way is to build the new stasis frontend made by the man himself. If not, leave it as is. No 'refresher-kits'... please.
Note: There are at least 3 different versions of the S/200.
Interesting baeijsman.. When I first opened the top on my S/200 there were 2 silver caps jumpered across at the top of each of the big power supply caps. I have misplaced them (they are around here somewhere) and I assumed that these 2 were the 'tantalum' caps everyone was talking about leaving off. Anyone know their values? How can I tell which version S/200 I have? I thought my was a Stasis one.
@Pavlograd: Those 2 caps are probably film in some fancy 'alu-design'. You can put those back if you want. Size is likely somewhere between 2 and 10uF. Not important.
The tantalums everyone's talking about are located on the PCB. Not all models had tantalums, and some might have been replaced at a later stage by people who added film caps to the PS-caps.
All S/200's are Stasis ones, only minor variations to the circuitry.
The tantalums everyone's talking about are located on the PCB. Not all models had tantalums, and some might have been replaced at a later stage by people who added film caps to the PS-caps.
All S/200's are Stasis ones, only minor variations to the circuitry.