Cyrus 1 project

[Geoff]

Originally posted by jmateus
BTW, speaking about quasi completary amplifiers, can anyone direct
me to a good and proven amplifier of this kind, using BJT's (Not Mos
fets) that would satisfy the term High Fidelity?

I'm asking because I've seen many schematics of this kind and none says Hi/Fi on the input, output or in the middle...What a shame!

Perhaps .......?

http://www.tcaas.btinternet.co.uk/cyrus1pwr.gif

[Geoff]

Originally posted by jmateus
But I've been lookiong for a quasi amplifier for quite some time as I've got so many NPN good quality transistors and I couldn't find any design that merit the term HiFi. Perhaps this one you sent me, is it that good? The schematic looks promising though.

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!

[lineup]

Originally posted by jmateus
Hi Geoff

Thanks very much for the link.
I've done a couple of JLH class A amplifiers, the last one from your
site. This one is sensational and is a must for my ESL built almost four years ago. Still running.

But I've been lookiong for a quasi amplifier for quite some time as I've
got so many NPN good quality transistors and I couldn't find any
design that merit the term HiFi. Perhaps this one you sent me, is it
that good?
The schematic looks promising though.

Originally posted by Geoff

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!

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

[Geoff]

Originally posted by lineup

Questions for Geoff :
Cyrus One is not a Class A, right?

Correct. Class-AB with a quiescent current of about 75mA.

You don't happen to know where to find parts list?
I mean it would be good to see what Transistors were used?

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]

Thanks Lineup for the links, very informative.
I believe Cyrus I was a class AB quasi complementary design.
The transistors used are in the schematic, 2SA872 and 2ASC1775
except for the drivers, MJE243 and MJE253 and of course the outputs.

[lineup]

Originally posted by jmateus
Thanks Lineup for the links, very informative.

I believe Cyrus I was a class AB quasi complementary design.

The transistors used are in the schematic, 2SA872 and 2ASC1775
except for
the drivers, MJE243 and MJE2353
and of course the outputs.

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/dynac...ST80/schem.jpg
Parts List:
http://home.indy.net/~gregdunn/dynac...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

[lineup]

Originally posted by jmateus
Yes, Geoff good old times!
Lineup,
a few years ago I bought on Ebay an ST80, burned up to
the bones,
I fixed it and had it playing.
----------------
....truth is I couldn't bare the bad quality of that amplifier, so I disassembled it ....

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/cont...onCyrus1-2.JPG

This picture is : 1956x1309 pixels and 1.4MB !!!!!!!

[Geoff]

Originally posted by lineup

I managed to find a very good picture of inside of Cyrus One

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.

[lineup]

Originally posted by destroyer X
Line up

The image is more than we can see in our computer monitor.
They normally have 1000 x 800 (or something alike) pixels
----
Watch the image with lower resolution and see that the losses are not so big...the noise are result of my processing..they can be removed or avoided.

regards, Carlos

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

[jmateus]

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.