Much obliged Geoff. You've been a great help.
I've hooked up the Cyrus 1 to the tweeters on my speakers in partnership with a Cyrus 2 and PSX for the rest. It is definitely imparting some of it's magic but I'll have to find a better solution. I wish I had 3 way speakers instead of 2.5 way.
I didn't know how much of the 'performance' I was missing. I always had faith that higher resolution would bring me closer to the music eventually and this is a very positive step forward.
Anyway, Thanks for the schematic Geoff. Hopefully this will be my first proper amplifier fix. My girlfriend laughs at the amount of our friends electrical equipment that I have fixed with cotton buds, post-it-notes, switch cleaner and grease.
Martin.
I've hooked up the Cyrus 1 to the tweeters on my speakers in partnership with a Cyrus 2 and PSX for the rest. It is definitely imparting some of it's magic but I'll have to find a better solution. I wish I had 3 way speakers instead of 2.5 way.
I didn't know how much of the 'performance' I was missing. I always had faith that higher resolution would bring me closer to the music eventually and this is a very positive step forward.
Anyway, Thanks for the schematic Geoff. Hopefully this will be my first proper amplifier fix. My girlfriend laughs at the amount of our friends electrical equipment that I have fixed with cotton buds, post-it-notes, switch cleaner and grease.
Martin.
Hi Sonus,
I suspect Cyrus had the gain in the power amp sections exactly matching as they moved through the various versions.
How have you arranged the gain in the bi-amped arrangement?
BTW,
I have been recommending bi-amping for years, even to the extent of using different amps for the different frequency ranges.
Your treble off the One and bass/mid off the Two+PSX seems to be the way to go.
Has that got rid of the dullness?
Is the dullness due to the Two using parallel pairs, or due to adding the PSX or due to modifying the PSX?
Could the last two causes be "cured" by adding decoupling inside the Two case? Big film caps right on the PCB?
I suspect Cyrus had the gain in the power amp sections exactly matching as they moved through the various versions.
How have you arranged the gain in the bi-amped arrangement?
BTW,
I have been recommending bi-amping for years, even to the extent of using different amps for the different frequency ranges.
Your treble off the One and bass/mid off the Two+PSX seems to be the way to go.
Has that got rid of the dullness?
Is the dullness due to the Two using parallel pairs, or due to adding the PSX or due to modifying the PSX?
Could the last two causes be "cured" by adding decoupling inside the Two case? Big film caps right on the PCB?
AndrewT said:
Hi Andrew,
I'm using issue 7 (fully metal/toggle switch) amps and both appear to be almost identical except for the power supplies, transistors and any mods I have made. I was going to start a new thread for this today because there are a lot of interesting questions raised here. I'm running both amps discretely with the Two being fed from the 'tape out' of the One and so they have independent volume controls. I thought that this may be problematic but have found it very easy to get the levels matched. There is only one setting that works. It is slightly problematic that the Cyrus One has the original 'clicky' volume pot and the correct volume setting is always between clicks. I intend to convert them both to power amps and have an outboard passive driving both. I'm also quite interested in trying a stepped attenuator.
I am trying to work out my options here. The Cyrus One (totally stock) is working the Tannoy 611 above 2.5KHz and the difference is absolutely worthwhile and exciting. I need to find a way to bring more resolution below 2.5KHZ but I am limited by the 2.5 way configuration.
The best way forward, I think, is to investigate all those pesky time constants that you told me about so many times and try some proper bypassing and snubbing on the C2/PSX. I was looking for more bass but I have obviously sacrificed something in the process. Hearing the stock Cyrus One makes this blindingly obvious.
Main mods to Cyrus 2/PSX:
30,000uF slit foil changed to 88,000uF Mundorf M-Lytic.
High speed diodes.
All electrolytics replaced.
Input cap raised from 2.2uF electrolytic to 3uF Sonicap (polypropylene).
Alps Blue volume pot (balance removed).
Main questions for me:
Are the slit foils in the Cyrus One special after all or is it just that they have less capacity?
Are the differing transitors significant?
Does larger transformer change only the bass for the better?
Was the higher value input cap a bad idea?
I'm going to try 100nF caps across the PSX diodes but do you have any recommended values for snubbers/bypassing?
Martin.
AndrewT said:
I hate to admit it but I can't think of any other way except to change the negative feedback. I am very wary of doing this partly because I don't really have the expertise and partly because I have recently mucked about with the feedback in the Cyrus 2 and the input filter. My opinion, as a novice, is that it is a very delicate balancing act. I now realise that these amps are cleverly designed to squeeze everything from the design. I have gained alot of admiration for the designer and trust their choices a lot more and perhaps even an electrolytic as the input cap is for a reason?
Martin.
Hi,
changing the global feedback to alter the gain also changes the phase and gain margins.
This requires both expertise and instrumentation to get right.
Are there a pre out, power in set of RCAs on the Two? takes the pot and pre circuitry out of the equation.
I would adjust the Rs/Zin ratios to match the power amp overall gains (i.e. fixed attenuator) but it can alter output offset and HP filter.
I wonder if the dullness would show up as a frequency response difference. If it did, it would be easy to measure/modify/listen/measure/modify/listen etc.
But, I suspect that the dullness will not show as a response error. That takes the measure out and it becomes modify/listen/modify/listen and maybe never get to a solution.
changing the global feedback to alter the gain also changes the phase and gain margins.
This requires both expertise and instrumentation to get right.
Are there a pre out, power in set of RCAs on the Two? takes the pot and pre circuitry out of the equation.
I would adjust the Rs/Zin ratios to match the power amp overall gains (i.e. fixed attenuator) but it can alter output offset and HP filter.
I wonder if the dullness would show up as a frequency response difference. If it did, it would be easy to measure/modify/listen/measure/modify/listen etc.
But, I suspect that the dullness will not show as a response error. That takes the measure out and it becomes modify/listen/modify/listen and maybe never get to a solution.
Hi,
It's a shame that I don't have a scope. I use my soundcard for line level work. The Two doesn't have pre outs so I was thinking of making my own pre to feed them both just as they are now with a high pass filter preceeding the pot/stepped attenuator. I will try to keep the wires as short as possible of course and possibly add a switchable buffer just for experimentation.
Do you think I can recover the upper mid range detail from the Two? It only has to work well up to 2.5KHz. I know that you are a specialist in this area. Can you give me some ball park suggestions for a snubber or more local decoupling? I'll be reading up on it tonight though but I know that you guys understand the interactions of LCR a lot more than I do.
Many thanks,
Martin.
It's a shame that I don't have a scope. I use my soundcard for line level work. The Two doesn't have pre outs so I was thinking of making my own pre to feed them both just as they are now with a high pass filter preceeding the pot/stepped attenuator. I will try to keep the wires as short as possible of course and possibly add a switchable buffer just for experimentation.
Do you think I can recover the upper mid range detail from the Two? It only has to work well up to 2.5KHz. I know that you are a specialist in this area. Can you give me some ball park suggestions for a snubber or more local decoupling? I'll be reading up on it tonight though but I know that you guys understand the interactions of LCR a lot more than I do.
Many thanks,
Martin.
AndrewT said:
I would never describe the unmodified Cyrus 2 + PSX as 'dull'. When I did a side-by-side comparison between this combination and a Cyrus 1 in my small, at the time, listening room and with my preferred music (acoustic Jazz and Baroque classical) I found the 2+PSX sounded a little 'heavy' compared with the 'delicacy' of the 1 and on balance I came out in favour of the latter. I suspect that the difference between the two is primarily down to the power supply rather than the different output transistors though the latter could contribute.
I have only bi-amped using two Cyrus 1s (with both passive and active filters) so the gain difference question did not arise. However, I see no problems in changing one of the feedback resistors in the Cyrus 2 (750R) to match the value used in the Cyrus 1 (1k), or vice versa, so that the gains are equal. The same pcb, schematic, compensation components etc are used for both amps so there should be no stability problems.
Sonusthree said:
At the time they were introduced, the slit foil capacitors did gain a reputation for sounding better than normal electrolytics of a similar value.
I doubt that the different output transistors are having any significant effect, nor the increased capacitance of the input capacitor. The type of capacitor used at the input will have a noticeable effect as will the fact that you have changed to a conductive plastic volume potentiometer. In conjunction with the changes made to the power supply, the input capacitor and potentiometer may well be robbing your Cyrus 2 of some of its 'life'.
Have you tried disconnecting the PSX and replacing the rail fuses in the amp so that it runs off its internal (smaller) transformer and slit foil capacitors? This may bring its performance closer to that of the Cyrus 1 as regards resolution but you may lose out elsewhere in the bass. It could at least narrow down the possible culprit(s) to either the modified PSX, if there is an improvement, or the input capacitor or potentiometer if there isn't.
Hi Geoff,
The Cyrus 2 already had Elnas installed and I recently replaced them with 12,000uF Nichicons as an experiment before getting the PSX recapped. I have heard a few people say that they don't have slit foils as standard either.I was quite happy with the results at the time but it is all relative and I have gained new insight into the sound I am looking for. For some unknown reason I was lacking bass and this is what I focused on in listening tests. I took my eye off the big picture.
I'll try it without the PSX and see what happens.
Best regards,
Martin.
The Cyrus 2 already had Elnas installed and I recently replaced them with 12,000uF Nichicons as an experiment before getting the PSX recapped. I have heard a few people say that they don't have slit foils as standard either.I was quite happy with the results at the time but it is all relative and I have gained new insight into the sound I am looking for. For some unknown reason I was lacking bass and this is what I focused on in listening tests. I took my eye off the big picture.
I'll try it without the PSX and see what happens.
Best regards,
Martin.
Thank Geoff!!!!
Geoff
Just an update on the original post, I've now replaced the components in the output stage that were blown including the output transistors, the Cyrus is now working fine with the external PSX. So many thanks. The righhand channel (which is the one that was damaged is now substantially clearer than the left - do you think that replacing all the transistor would help to even things out, also I don't seem to have a lot of bass - my speakers have always been laking somewhat in this department, I bought the Cyrus and PSX of e-bay together and they have always sounded the same - even pre repair, Would changing the caps help ? although the unit has been serviced my Cyrus in the past before I bought it. I have no way of knowing what was replaced.
Many thanks again
Dave
Geoff
Just an update on the original post, I've now replaced the components in the output stage that were blown including the output transistors, the Cyrus is now working fine with the external PSX. So many thanks. The righhand channel (which is the one that was damaged is now substantially clearer than the left - do you think that replacing all the transistor would help to even things out, also I don't seem to have a lot of bass - my speakers have always been laking somewhat in this department, I bought the Cyrus and PSX of e-bay together and they have always sounded the same - even pre repair, Would changing the caps help ? although the unit has been serviced my Cyrus in the past before I bought it. I have no way of knowing what was replaced.
Many thanks again
Dave
Re: Thank Geoff!!!!
Hi,
I'm glad to hear that it's working!! Well done! It gives me hope that I may fix my blown Cyrus One.
Did you only replace one channel's transistors? It's recommended to replace both sets with the same type. It's very interesting that you have more detail with the new ones. Do you prefer the sound? Which transistors did you use?
The Cyrus amps, even with PSX, were always known for their rather forward nature and this is the problem that I had. My speakers have four 8" drivers in large cabinets but the bass was still a little overun by the mid/treble. I assume that you've read the rest of this thread and how I modified my Cyrus 2 and PSX. I ended up with a bit more bass and it was a lot more solid but I lost something else in the process.
I don't want to discourage you from tinkering but do so with open eyes/ears and don't modify without thorough listening tests at every stage. To be fair though, I did go a little overboard on the PSX. Do you have slit foils caps in your C2/PSX or something else? Cyrus' service department told me that they don't replace them because they are stable. I'm not so sure about that so I changed them. I just can't be sure why I have lost some of that detail.
Do you get more bass with the PSX or using the internal supply?
How is your speaker placement? Have you tried them against a wall? It usually helps a bit.
Best regards and happy Easter,
Martin.
Hi,
I'm glad to hear that it's working!! Well done! It gives me hope that I may fix my blown Cyrus One.
Did you only replace one channel's transistors? It's recommended to replace both sets with the same type. It's very interesting that you have more detail with the new ones. Do you prefer the sound? Which transistors did you use?
The Cyrus amps, even with PSX, were always known for their rather forward nature and this is the problem that I had. My speakers have four 8" drivers in large cabinets but the bass was still a little overun by the mid/treble. I assume that you've read the rest of this thread and how I modified my Cyrus 2 and PSX. I ended up with a bit more bass and it was a lot more solid but I lost something else in the process.
I don't want to discourage you from tinkering but do so with open eyes/ears and don't modify without thorough listening tests at every stage. To be fair though, I did go a little overboard on the PSX. Do you have slit foils caps in your C2/PSX or something else? Cyrus' service department told me that they don't replace them because they are stable. I'm not so sure about that so I changed them. I just can't be sure why I have lost some of that detail.
Do you get more bass with the PSX or using the internal supply?
How is your speaker placement? Have you tried them against a wall? It usually helps a bit.
Best regards and happy Easter,
Martin.
Dave
I'm pleased to hear that you have got your Cyrus 2 working again. The difference in clarity between the channels may well be due to the replacement components you have fitted so it could be a good idea to make the same changes to both channels. In fact, when I contacted Cyrus many years ago the service engineer recommended changing all the output transistors even if only one or two had blown. I didn't do so and didn't notice any difference when the amp was compared with another Cyrus 1 that hadn't had any work done on it.
The lack of bass may be due to capacitor ageing, a lot depends on when your amp was serviced by Cyrus. Again when I contacted Cyrus, I was informed that they replaced all on-board electrolytics as a matter of course whenever an amp went in for service or repair. The prime suspect is the 470uF non-polarised capacitor in the feedback network (C41/42 in your v6). Unfortunately, though most suppliers have a 470uF 6.3V NP in their stock range, I have been unable to find a source in the UK for a quality capacitor to use in this position, eg a Nichicon Muse as originally fitted in one of my Cyrus amps. It is desirable to use a good quality capacitor in this position and the only solution is either to import some suitable capacitors from the States or elsewhere (expensive in small quantities due to handling charges etc) or to use two 1000uF polarised electrolytics back-to-back.
Geoff
I'm pleased to hear that you have got your Cyrus 2 working again. The difference in clarity between the channels may well be due to the replacement components you have fitted so it could be a good idea to make the same changes to both channels. In fact, when I contacted Cyrus many years ago the service engineer recommended changing all the output transistors even if only one or two had blown. I didn't do so and didn't notice any difference when the amp was compared with another Cyrus 1 that hadn't had any work done on it.
The lack of bass may be due to capacitor ageing, a lot depends on when your amp was serviced by Cyrus. Again when I contacted Cyrus, I was informed that they replaced all on-board electrolytics as a matter of course whenever an amp went in for service or repair. The prime suspect is the 470uF non-polarised capacitor in the feedback network (C41/42 in your v6). Unfortunately, though most suppliers have a 470uF 6.3V NP in their stock range, I have been unable to find a source in the UK for a quality capacitor to use in this position, eg a Nichicon Muse as originally fitted in one of my Cyrus amps. It is desirable to use a good quality capacitor in this position and the only solution is either to import some suitable capacitors from the States or elsewhere (expensive in small quantities due to handling charges etc) or to use two 1000uF polarised electrolytics back-to-back.
Geoff
I had a similar problem finding the correct part so went for these Black Gates :
http://www.hificollective.co.uk/components/black_gate_n_type.html
http://www.hificollective.co.uk/components/black_gate_n_type.html
Cyrus 2 Power supply
Hi,
Have just replaced all the faulty output and driver transistors on my early Cyrus 2.
I get sound out both channels so that's fine.
Problem is R110 connected to C61 large resistor gets very hot and have seen it smoking, but not sure what the problem is?
It's the resistor with ceramic washers on the PCB.
The 3.15A fuses have not blown yet.
This amp was previously used with a PSX, so apart from the fuses have I missed anything?
Hi,
Have just replaced all the faulty output and driver transistors on my early Cyrus 2.
I get sound out both channels so that's fine.
Problem is R110 connected to C61 large resistor gets very hot and have seen it smoking, but not sure what the problem is?
It's the resistor with ceramic washers on the PCB.
The 3.15A fuses have not blown yet.
This amp was previously used with a PSX, so apart from the fuses have I missed anything?
Hi Optimiser,
Which version of the Cyrus 2 do you have? (Does it have a metal or plastic case, a headphone socket and/ or a push or toggle switch?) I'm guessing that it's an early plastic model.
Have you traced that part of the circuit?
Is it a 'bleeder' resistor to discharge the caps?
I only have one early plastic Cyrus and I don't fancy dismantling it again!
Cheers,
Martin.
Which version of the Cyrus 2 do you have? (Does it have a metal or plastic case, a headphone socket and/ or a push or toggle switch?) I'm guessing that it's an early plastic model.
Have you traced that part of the circuit?
Is it a 'bleeder' resistor to discharge the caps?
I only have one early plastic Cyrus and I don't fancy dismantling it again!
Cheers,
Martin.
It's the plastic case version with headphone socket and push button.
I have been testing the Cyrus 2 through headphones and also with Ruark Talisman 2's for about an hour and it's working great, and the resistor seems to have stopped smoking now.
The resistor is connected to D6 and D8 rectifier diodes.
One of the diodes looks as though it has been replaced as it is darker than the other 3 marked as MR852. Should I replace these diodes as a precaution perhaps?
The amp was serviced by Mission a few years ago and has had all the usual caps replaced.
Does anyone know the original value of R110 which is a power resistor, and measures about 190R but the markings look a bit worn. It looks like brown white brown, so could be 190R ?
I have been testing the Cyrus 2 through headphones and also with Ruark Talisman 2's for about an hour and it's working great, and the resistor seems to have stopped smoking now.
The resistor is connected to D6 and D8 rectifier diodes.
One of the diodes looks as though it has been replaced as it is darker than the other 3 marked as MR852. Should I replace these diodes as a precaution perhaps?
The amp was serviced by Mission a few years ago and has had all the usual caps replaced.
Does anyone know the original value of R110 which is a power resistor, and measures about 190R but the markings look a bit worn. It looks like brown white brown, so could be 190R ?
optimiser said:
This resistor is 180R. It feeds the 'power on' LED from the junction of D6/D8. The arrangement is similar to that shown on my website for the Cyrus v7 power supply except that a single 180R resistor (R110) is used in place of the two 100R resistors (R119 & R120) that are fitted on the later version.
The current through this resistor, and the LED, is rather high (too high IMO) so it will get warm.
Geoff
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