jmateus said:
Well, the Cyrus 1 and Cyrus 2 (basically the same circuit, the 2 had slightly higher rail voltages and beefier output transistors) were commercial amps that were quite highly regarded in their time. They were referred to as 'budget' audiophile amplifiers in some reviews.
PS. I'm pleased to hear that you are enjoying your JLH Class-A!
jmateus said:
Geoff said:
The Cyrus One ( http://www.cyrusaudio.com/ )
looks interesting.
http://www.tcaas.btinternet.co.uk/cyrus1pwr.gif
Has got some 'extras'.
Like for example the input stage solution with double transistors.
And the limiting capacitors C49 / C50.
We can see it is an amplifier done with care for best performance.
-------------------------------------------------
Questions for Geoff :
Cyrus One is not a Class A, right?
You don't happen to know where to find parts list?
I mean it would be good to see what Transistors were used?
Even if we of course, can use good upgrade/replacement devices, today.
Regards, lineup
lineup said:
Correct. Class-AB with a quiescent current of about 75mA.
All the components are identified on the schematic. The transistor types are in a list in the top left-hand corner of the diagram. When I redrew the schematic I found it gave more clarity by not including the type adjacent to the transistor itself.
jmateus said:
The very old ( 1969 ) Dynaco STEREO 80, uses two 2N3055 for output.
I was lucky to find a complete article by a guy here:
Dynaco Stereo 80 Power Amplifier
Schematic:
http://home.indy.net/~gregdunn/dynaco/components/ST80/schem.jpg
Parts List:
http://home.indy.net/~gregdunn/dynaco/components/ST80/parts.jpg
jmateus,
As there are 'generations' between year 1969 Dynaco ST-80 and Cyrus One,
no question, Cyrus One is the better amplifier.
I am more interested in simplicity, so I want to try to explore Dynaco ST-80
and see if that amplifier circuit model can be used and improved.....
------------------------------------
I am glad I found the parts list for Dynaco, though.
Now I can set up the original for simulation
and go from there - trying to improve!
Regards, lineup
jmateus said:
Yes, I have seen, now when searching, someone say the same:
"In original this amp was not very good or reliable."
But have also seen one saying the Dynaco ST-80 amplifier can be modified into being good.
He has rebuilt several.
--------------------
I managed to find a very good picture of inside of Cyrus One
http://content.answers.com/main/content/wp/en/f/f4/MissionCyrus1-2.JPG
This picture is : 1956x1309 pixels and 1.4MB !!!!!!!
lineup said:
That picture is of the earlier Cyrus 1 with the steel base and non-metalic cover. The equivalent Cyrus 2 used two paralleled output transistors as can be seen from the picture.
The schematic on my website is for the later v07 which had a cast alloy base (with integral heatsink) and cover. The Cyrus 2 implementation of this version used single, but larger, output transistors.
The two pcb layouts are generally similar. The main differences are in the area between the heatsink and the ribbon cable and the layout of the phono stage power supply.
Re:
Thanks for editing that biggy image, Carlos
I think maybe your friend jmateus will go for Cyrus One....
And for him that image can be good to study .. in small details.
I have started a new topic about my Dynaco ST-80 clone and the modification + simulation of it.
This thread is of an interesting JLH amplifier.
I do not want to disturb too much here ...
only a little bit.
Something like 1-2.5 topics per thread maybe is ideal.
Otherwise we can start call it threadjacking
lineup
destroyer X said:
Thanks for editing that biggy image, Carlos
I think maybe your friend jmateus will go for Cyrus One....
And for him that image can be good to study .. in small details.
I have started a new topic about my Dynaco ST-80 clone and the modification + simulation of it.
This thread is of an interesting JLH amplifier.
I do not want to disturb too much here ...
only a little bit.Something like 1-2.5 topics per thread maybe is ideal.
Otherwise we can start call it threadjacking
lineup
I looked at the picture of the Cyrus and I said to myself, I'll never be able to make up the layout. Sure I would like to go for the Cyrus but
the problem is, too complicated to make the layout the way I usually
do my boards, by hand, trial and error.
Geoff is there any chance to get the layout of the power amplifier only?
May be it's a silly question but this is the only chance I have, I've looked in the Cyrus site but the manual doesn't show the board as i was hoping.
Hafler has the boards layed out this is why looked.
the problem is, too complicated to make the layout the way I usually
do my boards, by hand, trial and error.
Geoff is there any chance to get the layout of the power amplifier only?
May be it's a silly question but this is the only chance I have, I've looked in the Cyrus site but the manual doesn't show the board as i was hoping.
Hafler has the boards layed out this is why looked.
jmateus said:
Good idea
and no problem, jmateus
You can build only the power amplifier
In fact, this is what I should do
Regarding pre amplifier part of Cyrus
there are more simple and better ways to use, nowadays
Like a couple of high quality modern Op-Amps
I am also sure some member with good PCB layout tools
would create a good PCB layout for Cyrus One
in less than 1-2 hours
I have seen this happen more than once .. with other circuits!
Regards, lineup
Anyone with the right tools to layout the board for the Cyrus?
It would be the first good deed in 2007 for these poor guys who don't have them and struggle to have a decent board when they want to build an amplifier!.....
I usually do my boards by hand, trial and error, but this one....ah,
too dificult, I already tried...
It would be the first good deed in 2007 for these poor guys who don't have them and struggle to have a decent board when they want to build an amplifier!.....
I usually do my boards by hand, trial and error, but this one....ah,
too dificult, I already tried...
AndrewT said:
Maybe you would want THE OPTIMAL layout.
Then I can see why you would take your time.
But ...
A normal working layout, from a simulated Cyrus circuit
would not take long - not once you have all in Simulator.
I have seen guys that have these tools
are enormously quick.
That is if they are not busy with work or wife or something else ...
lineup
Some schematics are so dificult to reproduce to a layout that you'll
find yourself in a maze of lines and pads that dworf your capacity of
thinking and doing whatever else you need to complete it.
Carlos has his way of doing things, I do my boards (not so complicated)
the same way, but often times I have to give up due to the complication of the design. The problem is, doing the layout by this
not very inteligent method the board ends up with a lot of mistakes
that are very hard sometimes to rectify. Because it is an empirical
method it doesn't have anything rational nor scientific except the
obvious.
I do my boards that way and most times I feel myself thinking
this is so stupid that is not even funny! But I continue to do it (the
not so difficult ones) because , first I don't want to buy a layout program to do the layouts, second, because I must be very lazy to
learn the free ones. I tried a few and none is easy, besides they all deal with double layer or multi layer and I don't want to do double boards, just single layers.
I wish there was a program in which you just had to do a click on the computer and....pronto, the board is done, no there isn't!
So, this is the story Jerry, most people must be bored to death by these thoughts but I figured that someone would have at least
some curiosity. I'm done, boards are boards anyway, very
rarely they contribute to your hapiness......
find yourself in a maze of lines and pads that dworf your capacity of
thinking and doing whatever else you need to complete it.
Carlos has his way of doing things, I do my boards (not so complicated)
the same way, but often times I have to give up due to the complication of the design. The problem is, doing the layout by this
not very inteligent method the board ends up with a lot of mistakes
that are very hard sometimes to rectify. Because it is an empirical
method it doesn't have anything rational nor scientific except the
obvious.
I do my boards that way and most times I feel myself thinking
this is so stupid that is not even funny! But I continue to do it (the
not so difficult ones) because , first I don't want to buy a layout program to do the layouts, second, because I must be very lazy to
learn the free ones. I tried a few and none is easy, besides they all deal with double layer or multi layer and I don't want to do double boards, just single layers.
I wish there was a program in which you just had to do a click on the computer and....pronto, the board is done, no there isn't!
So, this is the story Jerry, most people must be bored to death by these thoughts but I figured that someone would have at least
some curiosity. I'm done, boards are boards anyway, very
rarely they contribute to your hapiness......
jmateus said:
Geoff said:
jmateus said:
I may not have a digital camera but I do have pcb layout software so you may be in luck!
I have attached a slightly simplified schematic (but with no loss of performance) for which I have prepared a preliminary layout. It goes without saying that that there is no guarantee for this layout and that it will need a careful, independant check prior to being used.
I have added a preset to enable the quiescent current to be adjusted and have tried to allow some flexibility in the selection of the input capacitor C31 (Cyrus used a physically small bipolar electrolytic) and R107A/B (Cyrus used a three leg dual resistor). Other than that, component footprints were taken from the Cyrus pcb. I have assumed that the output transistors would have a pin spacing similar to that of a TO-3P package rather than the TO220 used in the Cyrus 1.
It might be worthwhile asking a moderator to separate out the Cyrus related posts from this thread into a new one with an appropriate title.
PS I had to resize the schematic to allow it to be attached which reduced the quality. If you want a full size version please email me.
Attachments
Here is the pcb layout. The physical size is 100 x 80. I started with a component placing identical to that on the Cyrus pcb but ended up making various changes to allow space for components that were mounted elsewhere on the Cyrus board (eg the output Zobel network) and for a physically larger input capacitor etc.
When the layout has received an independant check, and any necessary modifications have been made, I can supply a high-res image of the copper pattern
When the layout has received an independant check, and any necessary modifications have been made, I can supply a high-res image of the copper pattern
Attachments
Hi,
compensation consists of only c35, c41 & c45.
I think you should add a few more locations for C and RC compensation BUT NOT a Miller comp cap.
C43 is too large.
C31 limits the input filter to <=165mS.
C43 can usefully be reduced to 220uF or 470+470uF in series back to back
This will allow a lower value of PSU capacitance to be used.
470uf gives 470mS requiring the PSU to be set to 660mS and for an 8ohm speaker that amounts to +-80mF on each channel. Simply too much.
R83 might be a little high, try 560r.
Swap c59 & r109. That allows an alternative feed back tapping point from the top of c59.
Q1.
is there any advantage in reducing the negative feedback resistor values and Zin? to maybe 47k or even lower? Then the 470uF may be required.
Q2.
why have you removed the thyristor protection? It is the ONLY protection to prevent catastrophic blow up.
compensation consists of only c35, c41 & c45.
I think you should add a few more locations for C and RC compensation BUT NOT a Miller comp cap.
C43 is too large.
C31 limits the input filter to <=165mS.
C43 can usefully be reduced to 220uF or 470+470uF in series back to back
This will allow a lower value of PSU capacitance to be used.
470uf gives 470mS requiring the PSU to be set to 660mS and for an 8ohm speaker that amounts to +-80mF on each channel. Simply too much.
R83 might be a little high, try 560r.
Swap c59 & r109. That allows an alternative feed back tapping point from the top of c59.
Q1.
is there any advantage in reducing the negative feedback resistor values and Zin? to maybe 47k or even lower? Then the 470uF may be required.
Q2.
why have you removed the thyristor protection? It is the ONLY protection to prevent catastrophic blow up.
AndrewT said:
Compensation is as per the original Cyrus 1. I agree, NO Miller cap (one of the reasons why I like this circuit)
The Cyrus uses a 470uF 6.3V bipolar electrolytic for C43, hence the large footprint (and no need for back-to-back). Of course a lower value capacitor can be used in this position, given the value of the associated resistor, but with the value given phase change does not begin until around 30Hz which may be why it was chosen.
There is a note on the schematic regarding reducing the value of R83.
The original has C59 and R109 the other way round. I had to reverse the order so that the components would physically fit on the pcb. The alternative would be to mount the Zobel across the output terminals.
Not if one wants to follow the original design.
Because it caused too much complication with the board layout and I was not prepared to spend too much time on a pcb design that I would never need to use (I already have four Cyrus 1s of various vintages).
Also, the pre v07 versions of the Cyrus did not have this part of the circuit and they have worked well enough over the years. An added factor is that this feature does not appear to work as intended. A friend's Cyrus lost its output transistors due to a near short across the output terminals despite it being a v07 with the protection circuit fitted.
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