I apologise if this has been asked before but I was wondering there are many people who have used different output transistors for the Mission Cyrus one amplifier such as 2d1047 and I believe the original was PT7 or BUV28.
What I dont understand and my question is what actually makes one better than the other? When you compare similar transistors what actually makes one better than the other as the output transistors are so important I would imagine.
I'm getting my hands on one soon that's faulty was about this . If the outputs are blown or not I would be very interested to know what kind of difference the transistors would make to the sound.
Appreciate any input! Thanks
What I dont understand and my question is what actually makes one better than the other? When you compare similar transistors what actually makes one better than the other as the output transistors are so important I would imagine.
I'm getting my hands on one soon that's faulty was about this . If the outputs are blown or not I would be very interested to know what kind of difference the transistors would make to the sound.
Appreciate any input! Thanks
What specific specification makes 2 almost identical transistors better?
Below is the specs for 2sd1047. What value would make it better for example? Ultimately yes for best for listening to music
Table 4.
Electrical characteristics
Symbol
Parameter
Test conditions
Min.
Typ.
Max.
Unit
I
CBO
Collector cut-off current
(I
E
= 0)
V
CB
= 200 V
0.1
μA
I
EBO
Emitter cut-off current
(I
C
= 0)
V
EB
= 6 V
0.1
μA
V
(BR)CEO
(1)
Collector-emitter
breakdown voltage (I
B
= 0)
I
C
= 50 mA
140
V
V
(BR)CBO
Collector-base breakdown
voltage (I
E
= 0)
I
C
= 100 μA
200
V
V
(BR)EBO
(1)
Emitter-base breakdown
voltage (I
C
= 0)
I
E
= 1 mA
6
V
V
CE(sat)
(1)
Collector-emitter
saturation voltage
I
C
= 5 A I
B
= 500 mA
I
C
= 7 A I
B
= 700 mA
0.5
0.7
V
V
V
BE
Base-emitter voltage
V
CE
= 5 V I
C
= 5 A
1.3
V
h
FE
DC current gain
I
C
= 1 A V
CE
= 5 V
I
C
= 5 A V
CE
= 4 V
60
50
200
f
T
Transition frequency
I
C
= 0.5 A V
CE
= 12 V
20
MHz
C
CBO
Collector-base
capacitance (I
E
= 0)
V
CB
= 10 V f = 1 MHz
150
pF
t
on
t
stg
t
f
Resistive Load
Turn-on time
Storage time
Fall time
V
CC
= 60 V I
C
= 5 A
I
B1
= -I
B2
= 0.5 A
0.22
4.3
0.5
μs
μs
μs
Below is the specs for 2sd1047. What value would make it better for example? Ultimately yes for best for listening to music
Table 4.
Electrical characteristics
Symbol
Parameter
Test conditions
Min.
Typ.
Max.
Unit
I
CBO
Collector cut-off current
(I
E
= 0)
V
CB
= 200 V
0.1
μA
I
EBO
Emitter cut-off current
(I
C
= 0)
V
EB
= 6 V
0.1
μA
V
(BR)CEO
(1)
Collector-emitter
breakdown voltage (I
B
= 0)
I
C
= 50 mA
140
V
V
(BR)CBO
Collector-base breakdown
voltage (I
E
= 0)
I
C
= 100 μA
200
V
V
(BR)EBO
(1)
Emitter-base breakdown
voltage (I
C
= 0)
I
E
= 1 mA
6
V
V
CE(sat)
(1)
Collector-emitter
saturation voltage
I
C
= 5 A I
B
= 500 mA
I
C
= 7 A I
B
= 700 mA
0.5
0.7
V
V
V
BE
Base-emitter voltage
V
CE
= 5 V I
C
= 5 A
1.3
V
h
FE
DC current gain
I
C
= 1 A V
CE
= 5 V
I
C
= 5 A V
CE
= 4 V
60
50
200
f
T
Transition frequency
I
C
= 0.5 A V
CE
= 12 V
20
MHz
C
CBO
Collector-base
capacitance (I
E
= 0)
V
CB
= 10 V f = 1 MHz
150
pF
t
on
t
stg
t
f
Resistive Load
Turn-on time
Storage time
Fall time
V
CC
= 60 V I
C
= 5 A
I
B1
= -I
B2
= 0.5 A
0.22
4.3
0.5
μs
μs
μs
Only a few datasheet specs and graphs, mark out modern audio power transistors as special or different to early audio transistors such as the switching types fitted long ago to early Mission/Cyrus models. For some understanding, spend a little time reading one of Douglas Self's design handbook editions for simple but detailed illustrations of how modern power transistors do better. See "Output stage distortions"
60 years of developments have changed the technology and capabilities semiconductors significantly. For audio types, it has shifted from fast switching characteristics for class AB amplifiers to simply overall faster devices. Now, Ft (the gain-bandwidth product) and gain linearity are considered prime factors of a good audio transistor and the best but most expensive types are Sanken's LAPT type transistors. Toshiba, On-semi and others follow closely with their more economical, perforated emitter audio types. However, "best type" interpreted as meaning best specifications for lowest THD at all power levels, does not mean best sounding - it means best measuring which should translate to best sound quality but often doesn't - at least not for many who listen for the pleasure of music at family-friendly levels.
It also needs to be said that simply substituting modern, faster and more linear transistors for the earlier types is a bad idea. Not only do you risk the stability and reliability of an old design by fitting faster or substantially different type transistors but it's likely that some of the desired harmonics that were an identifiable part of the original product, will be lost. So even if you have containers full of cheapo Chinese copied audio semis, don't be tempted to fit them in your Cyrus. BUV48 from RS is a suitable substitute, given the larger package and lead spacing but available if you need similar replacement output transistors and this advice has been repeated in many Cyrus repair threads here over the years.
Original Sanyo 2SD1047 was a good power transistor for general audio use - sort of in the middle, between craptanium TIP3055 and high grade MJW0281 etc. It was the mainstay of Rotel amplifiers for many years but current Chinese copies vary too widely from one off-brand to another and too many sanded, re-marked and unbranded products to consider reliable for anything more than power supplies. Genuine KEC brand KTD1047 is a good substitute but even that 2nd source is now faked
60 years of developments have changed the technology and capabilities semiconductors significantly. For audio types, it has shifted from fast switching characteristics for class AB amplifiers to simply overall faster devices. Now, Ft (the gain-bandwidth product) and gain linearity are considered prime factors of a good audio transistor and the best but most expensive types are Sanken's LAPT type transistors. Toshiba, On-semi and others follow closely with their more economical, perforated emitter audio types. However, "best type" interpreted as meaning best specifications for lowest THD at all power levels, does not mean best sounding - it means best measuring which should translate to best sound quality but often doesn't - at least not for many who listen for the pleasure of music at family-friendly levels.
It also needs to be said that simply substituting modern, faster and more linear transistors for the earlier types is a bad idea. Not only do you risk the stability and reliability of an old design by fitting faster or substantially different type transistors but it's likely that some of the desired harmonics that were an identifiable part of the original product, will be lost. So even if you have containers full of cheapo Chinese copied audio semis, don't be tempted to fit them in your Cyrus. BUV48 from RS is a suitable substitute, given the larger package and lead spacing but available if you need similar replacement output transistors and this advice has been repeated in many Cyrus repair threads here over the years.
Original Sanyo 2SD1047 was a good power transistor for general audio use - sort of in the middle, between craptanium TIP3055 and high grade MJW0281 etc. It was the mainstay of Rotel amplifiers for many years but current Chinese copies vary too widely from one off-brand to another and too many sanded, re-marked and unbranded products to consider reliable for anything more than power supplies. Genuine KEC brand KTD1047 is a good substitute but even that 2nd source is now faked
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Hi dj_holmes,
Just build it as it is. You can use any decent quality (real) output transistor with high enough ratings. The BUV48 will work as I used them doing warranty work on these amps. The new ones from On-Semi also work really well and are better suited to the job at hand.
One thing you should do is file the heat sink surface flat with a large, fine flat file so the heat transfer is maximized. If I had one complaint to lodge against Cyrus, it is that the finish on the transistor mounting area on their heat sinks is well below standard. I don't believe their special insulators work that well against that surface roughness. You should use mica insulators and thermal compound. All new, don't attempt to reuse the ones in there.
-Chris
Just build it as it is. You can use any decent quality (real) output transistor with high enough ratings. The BUV48 will work as I used them doing warranty work on these amps. The new ones from On-Semi also work really well and are better suited to the job at hand.
One thing you should do is file the heat sink surface flat with a large, fine flat file so the heat transfer is maximized. If I had one complaint to lodge against Cyrus, it is that the finish on the transistor mounting area on their heat sinks is well below standard. I don't believe their special insulators work that well against that surface roughness. You should use mica insulators and thermal compound. All new, don't attempt to reuse the ones in there.
-Chris
I don't know of anyone here in Oz who has attempted anything radical with a little Mission Cyrus amplifier and I wouldn't even consider. modding it. You could easily google threads here if you want to see what others suggest but space is tight enough already and significant mods render amplifiers unsaleable when you decide to change your audio system again. Useful comments on Cyrus 1&2 power supply and cooling limitations here: A Paul Kemble web page - Mission Cyrus 1 integrated amplifier.
The PSX series auxiliary boosted power supplies were recommended and necessary for all Cyrus models in order, to reach their full rated power output since none of them can accommodate large enough power supplies for that. Perceived power has a logarithmic relationship to electrical power so even doubling it doesn't increase maximum volume by all that much. Increasing the power supply rails by +/- 10V and doubling the number of output transistors does make them run hotter though. Look at the increased heatsink size of Cyrus 2 for a hint of how much and even that wasn't enough cooling.
Hi Chris,
do you mean new BUV48's, or new devices from ON-Semi in general? Which ones then?
Best regards!
Thanks guys very interesting read! Thanks Chris / Ian I'm really keen on this whole modding thing at the moment and was already thinking of changing caps to say the least! I have so many heatsinks from broken equipment I found or bought that I'm sure something will fit! But for now I will just wait to see what issue the Cyrus actually has, if it is a power supply issue then replacing it with something better is definitely an option for me
Maybe not more voltage but more current!!?!?!? Getting excited now and I don't think delivery is until next week. Also I dont think I have ever seen anyone change the PSU online!
Maybe not more voltage but more current!!?!?!? Getting excited now and I don't think delivery is until next week. Also I dont think I have ever seen anyone change the PSU online!
Hi dj_holmes,
Hold on a moment!
Wouldn't you like to see what you are modding from first?
As for increasing voltage and current, you'll have to double the power to hear a difference. Then you have got to worry that the drivers and input stage can handle the extra voltage. If that's okay, you have to calculate dissipations for all components that are going to run warmer. A part that is already warm will be hot at these increased voltages.
To be honest with you, this design is good at the voltages it is designed to operate at. If you want to go for higher power, build an amplifier designed for the higher voltages. But running this one that way is only asking for trouble. It certainly will not be at it's best at the higher voltages.
Higher current? Why? What do you plan to drive with it? I don't think you understand what you're doing. Have a good, long look at my tag line and think about that.
-Chris
Hold on a moment!
Wouldn't you like to see what you are modding from first?
As for increasing voltage and current, you'll have to double the power to hear a difference. Then you have got to worry that the drivers and input stage can handle the extra voltage. If that's okay, you have to calculate dissipations for all components that are going to run warmer. A part that is already warm will be hot at these increased voltages.
To be honest with you, this design is good at the voltages it is designed to operate at. If you want to go for higher power, build an amplifier designed for the higher voltages. But running this one that way is only asking for trouble. It certainly will not be at it's best at the higher voltages.
Higher current? Why? What do you plan to drive with it? I don't think you understand what you're doing. Have a good, long look at my tag line and think about that.
-Chris
I certainly agree with Chris. Choose something larger with a more open layout to mod, for reasons already made clear. More experienced folk than I and apparently the manufacturer too, realised that increasing power could cause this model to overheat and fail - hence the Cyrus 2 upgraded design was released. Not all Cyrus 2 versions used 2 pairs of output transistors though, as you can see in Paul Kemble's pic. and the service manuals for the different versions.
Re-capping an old amplifier isn't a bad idea but it would be surprising if the original power supply caps hadn't already been replaced as they weren't robust. This is restoring, not modding though. Mods amount to a re-design which needs to be carefully thought through from an engineering point of view - hence the caution because no one wants to end up with something that costs more than its worth, where the amazing night and day sound quality improvements soon wear off or it just self-destructs. That's what I find happens with typical DIY "mods"
Re-capping an old amplifier isn't a bad idea but it would be surprising if the original power supply caps hadn't already been replaced as they weren't robust. This is restoring, not modding though. Mods amount to a re-design which needs to be carefully thought through from an engineering point of view - hence the caution because no one wants to end up with something that costs more than its worth, where the amazing night and day sound quality improvements soon wear off or it just self-destructs. That's what I find happens with typical DIY "mods"
Lord is nothing simple! And there seems no tracking update on my Cyrus since yesterday!
I'm just excited to work on it and see what the results are as I heard so much about it. I do have a friend who also thinks he knows what hes talking about lol. Neither of us are experts but we both enjor pretending we know more than the other and often swap amplifiers etc. Its good fun! I gave him a partially modded/upgraded(?) amplifier from my last thread. The amp had no name! But was good quality. I have been reading a lot more about the Cyrus, guess just have to wait and see before I get too excited!
I'm just excited to work on it and see what the results are as I heard so much about it. I do have a friend who also thinks he knows what hes talking about lol. Neither of us are experts but we both enjor pretending we know more than the other and often swap amplifiers etc. Its good fun! I gave him a partially modded/upgraded(?) amplifier from my last thread. The amp had no name! But was good quality. I have been reading a lot more about the Cyrus, guess just have to wait and see before I get too excited!
I got it!!
After inspection I check the external fuse and it was blown. After replacing it it blew again. After replacing it with a higher wattage fuse because that's all I had it blew the internal fuses.
So I guess the transformer is fine. After getting my meter out it was beeping all over the place on the left channel (or right channel?) output transistors. I guess they are both blown as the other channel does not beep.
I did not check the controller (driver?) transistors behind the main transistors. Guess they are blown too? But from what I have read its best to replace those too. So I guess I need to replace 4 transistors! and 4 driver transistors what ever they are. I have service manual guess I'll check later.
I know Sanken transistors are a lot better has anyone fitted these in them?
Thanks in advance!
After inspection I check the external fuse and it was blown. After replacing it it blew again. After replacing it with a higher wattage fuse because that's all I had it blew the internal fuses.
So I guess the transformer is fine. After getting my meter out it was beeping all over the place on the left channel (or right channel?) output transistors. I guess they are both blown as the other channel does not beep.
I did not check the controller (driver?) transistors behind the main transistors. Guess they are blown too? But from what I have read its best to replace those too. So I guess I need to replace 4 transistors! and 4 driver transistors what ever they are. I have service manual guess I'll check later.
I know Sanken transistors are a lot better has anyone fitted these in them?
Thanks in advance!
Hi dj_holmes,
You should have stopped and looked at the blown fuse first. Was it silvered or blackened? Probably it was, meaning a high energy blow. Do not replace the fuse then, you likely extended the amount of damage.
Measure each output for short circuits. Measure them all even if you find the first ones blown.
Keep in mind that both channels might be blown. You can lose both at the same time if they were connected together. You should also replace the driver transistors and keep checking back until you start finding good parts. Replace one level back from the last bad part. Parts can be stressed and change their characteristics without failing immediately. That's why you replace one stage back from the last dead thing you find.
One thing you need to do. Take a breath, take your time and do not rush to do anything! Always ask yourself if what you are doing might cause damage. Advice from someone who isn't a good audio technician is very likely bad advice.
Patience man!
-Chris
You should have stopped and looked at the blown fuse first. Was it silvered or blackened? Probably it was, meaning a high energy blow. Do not replace the fuse then, you likely extended the amount of damage.
Measure each output for short circuits. Measure them all even if you find the first ones blown.
You know they are better? Depends on the application. do you know how to compensate an amplifier by chance? No need to answer that. Stick with the plan and replace them with BUV48. I haven't used those in over a decade, so I can't remember which to use. Try matching the case style to the ones installed in the amplifier. How about showing us a picture? That would be helpful.
Keep in mind that both channels might be blown. You can lose both at the same time if they were connected together. You should also replace the driver transistors and keep checking back until you start finding good parts. Replace one level back from the last bad part. Parts can be stressed and change their characteristics without failing immediately. That's why you replace one stage back from the last dead thing you find.
One thing you need to do. Take a breath, take your time and do not rush to do anything! Always ask yourself if what you are doing might cause damage. Advice from someone who isn't a good audio technician is very likely bad advice.
Patience man!
-Chris
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