Does anyone know if the Cyrus Two amps have especially low input impedance?
The Cyrus website quote 14KOhm. http://www.cyrusaudio.com/product.asp?ProductID=71&text=spec
I have just purchased a (pre-assembled) tube buffer stage which goes before this amp and the maufacturer is telling me that the quoted impedance is only a nominal value and that the amplifiers low impedance is causing the distortion problems with the preceeding tube buffer!!
Does anyone know how difficult it is to drive this amp?
It's preamp section is passive, if that helps.
I'm just hoping that someone might know since theses amps are quite popular.
The Cyrus website quote 14KOhm. http://www.cyrusaudio.com/product.asp?ProductID=71&text=spec
I have just purchased a (pre-assembled) tube buffer stage which goes before this amp and the maufacturer is telling me that the quoted impedance is only a nominal value and that the amplifiers low impedance is causing the distortion problems with the preceeding tube buffer!!
Does anyone know how difficult it is to drive this amp?
It's preamp section is passive, if that helps.
I'm just hoping that someone might know since theses amps are quite popular.
Hi Sonusthree,
The input bias resistor is 75K with a 4K7 resistor in series. This would be in parallel with the wiper of the volume control (10 K). Therefore, your input resistance is a little less than 10 K. Since there is a blocking capacitor, why not install a 100 K pot instead? The taper will not be exactly correct. This should help reduce the loading on the tube buffer.
I am assuming you just bought the buffer to lose the edgy sound some amps can get? What you ought to do first is recap your Cyrus. Replace all ceramics with mica or foil caps. Replace low value electrolytics with foil types and all other electrolytics with new. This is very important for the phono power supply. Almost every unit I see has bad caps near the voltage regulators (6 I think). This will make a large improvement in sound quality.
-Chris
The input bias resistor is 75K with a 4K7 resistor in series. This would be in parallel with the wiper of the volume control (10 K). Therefore, your input resistance is a little less than 10 K. Since there is a blocking capacitor, why not install a 100 K pot instead? The taper will not be exactly correct. This should help reduce the loading on the tube buffer.
I am assuming you just bought the buffer to lose the edgy sound some amps can get? What you ought to do first is recap your Cyrus. Replace all ceramics with mica or foil caps. Replace low value electrolytics with foil types and all other electrolytics with new. This is very important for the phono power supply. Almost every unit I see has bad caps near the voltage regulators (6 I think). This will make a large improvement in sound quality.
-Chris
Thanks Chris.
I've already replaced the standard pot with an Alps Blue velvet. It wasn't too easy getting it to fit so I'd rather not change it again if I can help it. (I'll have to check the value later today but I'm sure it's no more than 20K?)
As usuall your advice about recapping is spot on. You read my mind about the edgy sound. I couldn't see the wood for the trees!! I've begun ordering the electrolytics already and wil post my results here.
I use my Cyrus 2 with the PSX and so do not need the internal supply to work at all untill I can find a bargain record deck. Still looking though.
Ill recap that later on.
I recently contacted Cyrus about their renewal service for the PSX. I thought that it might be best to get the four monster 15000uF slit foil caps directly from them since they are quite hard to get hold of in the UK. They said:
"We do offer a service for the Cyrus 2 but the PSX is very stable and there would be no enhancement by offering a restorative service. With regards to the capacitors, we do not have these in stock as we do not change these as a rule."
16 year old 'lytics make me nervous but what do I know?
The Tube buffer is the only reason that I am asking about input impedance. The maker tells me that the input impedance is probably too low on my amp and that is why the Tubalizer is distorting badly. Frankly, I don't believe him since it distorts with every piece of equipment I have in the house. The only time it doesn't distort is when placed between the pre and power sections of a NAD integrated and this is because the input signal is greatly reduced by the preamp. I have tested on my soundcard and basically the negative cycles are being clipped but I guess this is an issue for the Tube forum.
Thanks again for your help Chris.
I've already replaced the standard pot with an Alps Blue velvet. It wasn't too easy getting it to fit so I'd rather not change it again if I can help it. (I'll have to check the value later today but I'm sure it's no more than 20K?)
As usuall your advice about recapping is spot on. You read my mind about the edgy sound. I couldn't see the wood for the trees!! I've begun ordering the electrolytics already and wil post my results here.
I use my Cyrus 2 with the PSX and so do not need the internal supply to work at all untill I can find a bargain record deck. Still looking though.
Ill recap that later on. I recently contacted Cyrus about their renewal service for the PSX. I thought that it might be best to get the four monster 15000uF slit foil caps directly from them since they are quite hard to get hold of in the UK. They said:
"We do offer a service for the Cyrus 2 but the PSX is very stable and there would be no enhancement by offering a restorative service. With regards to the capacitors, we do not have these in stock as we do not change these as a rule."
16 year old 'lytics make me nervous but what do I know?
The Tube buffer is the only reason that I am asking about input impedance. The maker tells me that the input impedance is probably too low on my amp and that is why the Tubalizer is distorting badly. Frankly, I don't believe him since it distorts with every piece of equipment I have in the house. The only time it doesn't distort is when placed between the pre and power sections of a NAD integrated and this is because the input signal is greatly reduced by the preamp. I have tested on my soundcard and basically the negative cycles are being clipped but I guess this is an issue for the Tube forum.
Thanks again for your help Chris.
Hi Sonusthree,
Change the 6 caps for the regulator stage now. Add some heatsink grease to the regulators now also. They are currently oscillating I bet, and running too hot. Given the cost you could always install new regulators now also. This cuts down on the number of times your unit has to come apart.
Check for ceramic caps at C69 and C70. Replace with mica. Do all teh other electrolytics as well as the 470uF 6 V feedback to ground caps. A bypass with a poly type would helps here. There are already a large number of polystyrene caps (great news).
You can replace the main filters later on. The PSX would be working within spec, but maybe conside bypassing them locally with film types (just the supply in the amp). On second thought, bypassing the main caps in the PSX would reduce the high frequency noise coming across the cable. Might be worthwhile.
-Chris
Change the 6 caps for the regulator stage now. Add some heatsink grease to the regulators now also. They are currently oscillating I bet, and running too hot. Given the cost you could always install new regulators now also. This cuts down on the number of times your unit has to come apart.
Check for ceramic caps at C69 and C70. Replace with mica. Do all teh other electrolytics as well as the 470uF 6 V feedback to ground caps. A bypass with a poly type would helps here. There are already a large number of polystyrene caps (great news).
You can replace the main filters later on. The PSX would be working within spec, but maybe conside bypassing them locally with film types (just the supply in the amp). On second thought, bypassing the main caps in the PSX would reduce the high frequency noise coming across the cable. Might be worthwhile.
-Chris
Hi,
I don't think the PSX disables the internal PSU.
The low current stages still get their power from the internal and the power output stage gets it's power from the PSX.
part of the improvement comes from the bigger grunt of the PSX, but I believe that a bigger improvement comes from the SEPARTION of the supply to the low level stages and the high current stage. No modulation effects creeping into the voltage amplifier.
If all the preceding is true then replacing aged components in the internal PSU should also reap dividends.
I don't think the PSX disables the internal PSU.
The low current stages still get their power from the internal and the power output stage gets it's power from the PSX.
part of the improvement comes from the bigger grunt of the PSX, but I believe that a bigger improvement comes from the SEPARTION of the supply to the low level stages and the high current stage. No modulation effects creeping into the voltage amplifier.
If all the preceding is true then replacing aged components in the internal PSU should also reap dividends.
As far as I understand it the PSX replaces the internal Cyrus 2 power supply except for the phono stage and the front power LED.
I provide power only to the PSX in my setup since I don't currently own a vinyl source (Yet )
Once I get the rest of my system balanced I would certainly like to hear the Phono stage which is, apparently, fantastic. Presumably partly due to the power supply seperation mentioned above.
I provide power only to the PSX in my setup since I don't currently own a vinyl source (Yet
) Once I get the rest of my system balanced I would certainly like to hear the Phono stage which is, apparently, fantastic. Presumably partly due to the power supply seperation mentioned above.
Hi Andrew,
The PSX replaces the supply for the entire amplifier including the voltage amp stage. The internal supply runs the power LED (yahoo!) and the phono amplifier regulators. That's it. However, the internal regulators tend to oscillate when the supply caps go bad and this could interfere with the operation of the power amp. Since these supply components are not expensive, it's best to simply replace the lot and be done with it.
Some amplifiers do regulate the voltage amp stages independently (like my Marantz 300DC). This really does have a very positive influence on the sound quality.
-Chris
Edit: Hi Sonusthree, I see we posted close to the same time.
The PSX replaces the supply for the entire amplifier including the voltage amp stage. The internal supply runs the power LED (yahoo!) and the phono amplifier regulators. That's it. However, the internal regulators tend to oscillate when the supply caps go bad and this could interfere with the operation of the power amp. Since these supply components are not expensive, it's best to simply replace the lot and be done with it.
Some amplifiers do regulate the voltage amp stages independently (like my Marantz 300DC). This really does have a very positive influence on the sound quality.
-Chris
Edit: Hi Sonusthree, I see we posted close to the same time.
A portion of Distortion.
Hi.
So far I have pretty much completed replacing the electrolytics, I have added heatsink grease to both regulators. I have used Cerafines for the polar and Black Gate N for the Non polar. I have managed to fit (just about as a temporary measure) two huge 2.2uF MKP's at the input of the power amp section. I have replaced the two 470uF caps at the regulators with 680uF.
I have not changed the large slit foil caps on the PSX or amplifier's internal supply.
I'm having a little trouble finding suitably sized 2.2uF Film caps to replace the original electrolytics but I believe these are for the currently unused phono stage. New regulators are on their way.
The sound at the moment is very disappointing. I'm hearing some distortion in both channels and the soundstage is greatly diminished. I would describe the problem as a very strong "Grain". It appears mostly when singers put some vigour into their performance.
I'm just starting to try and come to a diagnosis. I have disabled the PSX and a using the internal supply. I've tried different sources at differing levels with no difference. It seems to me that it is frequency related so I will run some test tones tomorrow.
I was expecting some time for the caps to settle. I've only run it for approximately 18 hours so far since the recap but I don't think this is the cause.
It's driving me crazy. Partly because I've tried so hard to improve the sound and have made it worse somehow and perhaps more importantly because I feel completely out of my depth if there is another more serious problem.
It seems to me that it is frequency and not level (input or output) related so I will run some test tones tomorrow.
The problem is in both channels.
My suspicions so far are C43 (470uF 16V) in the Feedback loop. I replaced it with the same value Black Gate N. The original looked quite strange when I removed it. Kind of potted at the bottom. I'll post some pictures soon. Perhaps the low ESR of the new caps has altered something? The originals were mostly Elnas though. There was already some very slight distortion before the recap but definitely not as obvious as it is now.
Please forgive my inane ramblings here especially since I have not yet tried absolutely everything to remedy the problem. I just needed to get this off my chest. I have dreamed of owning exactly this setup since 1991 and it means the world to me.
Thanks for reading this far.
Martin.
Hi.
So far I have pretty much completed replacing the electrolytics, I have added heatsink grease to both regulators. I have used Cerafines for the polar and Black Gate N for the Non polar. I have managed to fit (just about as a temporary measure) two huge 2.2uF MKP's at the input of the power amp section. I have replaced the two 470uF caps at the regulators with 680uF.
I have not changed the large slit foil caps on the PSX or amplifier's internal supply.
I'm having a little trouble finding suitably sized 2.2uF Film caps to replace the original electrolytics but I believe these are for the currently unused phono stage. New regulators are on their way.
The sound at the moment is very disappointing. I'm hearing some distortion in both channels and the soundstage is greatly diminished. I would describe the problem as a very strong "Grain". It appears mostly when singers put some vigour into their performance.
I'm just starting to try and come to a diagnosis. I have disabled the PSX and a using the internal supply. I've tried different sources at differing levels with no difference. It seems to me that it is frequency related so I will run some test tones tomorrow.
I was expecting some time for the caps to settle. I've only run it for approximately 18 hours so far since the recap but I don't think this is the cause.
It's driving me crazy. Partly because I've tried so hard to improve the sound and have made it worse somehow and perhaps more importantly because I feel completely out of my depth if there is another more serious problem.
It seems to me that it is frequency and not level (input or output) related so I will run some test tones tomorrow.
The problem is in both channels.
My suspicions so far are C43 (470uF 16V) in the Feedback loop. I replaced it with the same value Black Gate N. The original looked quite strange when I removed it. Kind of potted at the bottom. I'll post some pictures soon. Perhaps the low ESR of the new caps has altered something? The originals were mostly Elnas though. There was already some very slight distortion before the recap but definitely not as obvious as it is now.
Please forgive my inane ramblings here especially since I have not yet tried absolutely everything to remedy the problem. I just needed to get this off my chest. I have dreamed of owning exactly this setup since 1991 and it means the world to me.
Thanks for reading this far.
Martin.
Hi Martin,
The odd caps are non-polerized 470uF 6.3V (?). Sometimes they go open but are often okay. They are easy enough to reinstall. I've replaced them before without any ill effects.
I would make sure the differential transistors are properly matched and the outputs have proper bias current. Test tones may shed some light on this. I am never come across the problem you mention. I have repaired some units where the phono regulators were oscillating and the amp section was picking some up in line modes, that's the closest I've come to this.
A 'scope comes in very handy.
-Chris
The odd caps are non-polerized 470uF 6.3V (?). Sometimes they go open but are often okay. They are easy enough to reinstall. I've replaced them before without any ill effects.
I would make sure the differential transistors are properly matched and the outputs have proper bias current. Test tones may shed some light on this. I am never come across the problem you mention. I have repaired some units where the phono regulators were oscillating and the amp section was picking some up in line modes, that's the closest I've come to this.
A 'scope comes in very handy.
-Chris
Hi Chris, Everyone,
I've been like a bear woth a sore head lately trying to work out what to do. Definite distortion with music but none was audible with test tones.
Ages ago when I swapped out the original pot for an ALPS unit without balance control, I substituted the balance control for two 100K resistors. I recently removed those resistors completely after I read this thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=89636
I must have been confused and misread the advice on removing the balance altogether. Oh well these things happen.
Well tonight I fitted the vacant balance controls with two 42K Resistors and at low 2am listening levels the detail is back. The grain is gone and the sound is forcably being projected from my speakers like it has no choice. Mmmm... Madeleine Peyroux.
I don't quite know whats going on here yet but the original balance should have been 50K per side and not the 100K that I mistakenly substituted it with. I guess when I removed the balance altogether I raised the resistance towards infinity.
Given the time here (2:40am) I'm not even going to start hypothesising. But it's definitely working better at low levels and I'm very happy. Can't wait to test at decent levels in the morning.
If the tubalizer works as well I think I may just soil myself.
I'll post the results tomorrow,
Cheers,
Martin.
I've been like a bear woth a sore head lately trying to work out what to do. Definite distortion with music but none was audible with test tones.
Ages ago when I swapped out the original pot for an ALPS unit without balance control, I substituted the balance control for two 100K resistors.
I recently removed those resistors completely after I read this thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=89636 I must have been confused and misread the advice on removing the balance altogether. Oh well these things happen.
Well tonight I fitted the vacant balance controls with two 42K Resistors and at low 2am listening levels the detail is back. The grain is gone and the sound is forcably being projected from my speakers like it has no choice. Mmmm... Madeleine Peyroux.
I don't quite know whats going on here yet but the original balance should have been 50K per side and not the 100K that I mistakenly substituted it with. I guess when I removed the balance altogether I raised the resistance towards infinity.
Given the time here (2:40am) I'm not even going to start hypothesising. But it's definitely working better at low levels and I'm very happy. Can't wait to test at decent levels in the morning.
If the tubalizer works as well I think I may just soil myself.
I'll post the results tomorrow,
Cheers,
Martin.
Hi Martin,
That's great news!
If the two 100K resistors terminated to ground you should have been fine. Open would be okay as well. The ground point must have been bad or non-existant, that's what I'm thinking anyway. That would have mixed the two channels together somewhat, not completely.
-Chris
That's great news!
If the two 100K resistors terminated to ground you should have been fine. Open would be okay as well. The ground point must have been bad or non-existant, that's what I'm thinking anyway. That would have mixed the two channels together somewhat, not completely.
-Chris
anatech said:
http://www.tcaas.btinternet.co.uk/cyrus1inp.gif
I had completely removed the 100K pot shown in the input schematic (above) . Which, I think, completely severed any links with the other channel? Your theory about mixing the channels instinctively sounds right to me because symmetrical test tones sounded fine but music did not. I would have expected the bass to be more susceptible this problem but maybe the 150pF cap (c29) has something to do with this?
Can you tell that I don't know what I'm talking about?
I really don't. But I'm learning all the time. -Martin
hi i have just removed the four diodes and the regulators the power led still lights up. and the amp sounds great would i expect any sonic improvment similar to psx or was what i done a waste of timeSonusthree said:As far as I understand it the PSX replaces the internal Cyrus 2 power supply except for the phono stage and the front power LED.
I provide power only to the PSX in my setup since I don't currently own a vinyl source (Yet
Once I get the rest of my system balanced I would certainly like to hear the Phono stage which is, apparently, fantastic. Presumably partly due to the power supply seperation mentioned above.
yes with psx.
now what was so difficult about that?
Can I presume you don't need the phono stage?
Then, you have reduced the loading on the PSU. Effect, unknown.
Apparently the advantage of PSX is the dedicated and larger PSU to the line and output stages of the 2. There not being sufficient room for a proper supply inside the 2.
Cyrus have stuck with this philosophy all the way to present. Small cases = extra sales of PSXr
now what was so difficult about that?
Can I presume you don't need the phono stage?
Then, you have reduced the loading on the PSU. Effect, unknown.
Apparently the advantage of PSX is the dedicated and larger PSU to the line and output stages of the 2. There not being sufficient room for a proper supply inside the 2.
Cyrus have stuck with this philosophy all the way to present. Small cases = extra sales of PSXr
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