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Old 23rd August 2005, 08:11 AM   #1
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Default Lyra Connoisseur 4-2L SE: What a masterpiece!

Hello Everyone,


there is a review of the 4-2LSE in the German magazine Stereoplay (August 2005) that has some superb photos of the inside of the line amp, and also has plenty of informatio about the circuit topology, and also about its components.

The article can be downloaded here: http://www.stereoplay.de/sixcms/medi...tp0805Lyra.pdf

MRupp wrote "I could translate the relevant passages in a few days but maybe somebody else is quicker? In the meantime you may try to get a reasonable translation from babel fish."

I will do a translation/resumé of the important stuff from that article:

* The power supply PCBs are right on top of the audio signal PCBs makeing the PS wires connect directly to the signal amplifiers

* A differential cascode on the input

* output stage with linear bipolars, powerful MOSFETs (IRF 510) and super fast JFETs are used to have a high bandwidth and a current potent amplifier

* dual mono power supply all through the amp.

*special iron plate circular transformers

* huge 20 000 uF caps in the PS

* Carr uses no ICs for the power supplies. Instead he uses 24 discrete regulators

* important signal wiring is done with wires and not on the PCBs

* Schottky diodes in the PS (20A diodes)

* the 20 000 uF caps are mounted in a way to minimize microfony effects

* input rotary switch and stepped attenuator with specially made Shallcos - Carr do not find potentiometers sonically good enough

* it is not balanced inside the line amps, but it can take balanced connectors

* star ground


That was it. If I have missed something, I apologise.


Photos in the next post.


Regards,
Sigurd
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Old 23rd August 2005, 08:28 AM   #2
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Old 23rd August 2005, 08:31 AM   #3
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This is taken from another thread (I hope you do not mind Mr Carr):

"hesener:

If you want to use a similar topology to the 4-2SE line amp, for the input I'd recommend a dual-JFET with a high Vds (40~50 volts), in addition to good noise and linearity. The 4-2SE can produce about 11V output, and the input JFETs should preferably work well with a healthy amount of Vds across it. The input JFETs' load is the low impedance of a common-base stage, so small capacitance is perhaps of less importance.

The input JFETs should also have low gate leakage currents with the operating Vds applied. Regarding gate leakage currents of JFETs in general, P-channel JFETs tend to behave better than N-channels, but FWIW, I've chosen N-channels for the inputs of the 4-2SE.

>The topology I am thinking of is a input differential pair, followed by source followers.

Hmmm. Although the 4-2SE does operate differentially, it is essentially a much-augmented folded-cascode topology, loosely similar to what the AD829 would be if it were made from discrete semiconductors and had a JFET input. And a bit more complex than what you have in mind.

How informative was the article about the circuit topology, componentry or physical structure of the 4-2SE?

regards, jonathan carr"



I found the article in Stereoplay very informative!


Here is the AD829 schematic:



Click the image to open in full size.


Regards,
Sigurd
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Old 23rd August 2005, 08:33 AM   #4
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The review says "Extrem teuer", what about 25000 EUR but it looks nice. I like massive materials.
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Old 23rd August 2005, 08:35 AM   #5
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Photos from the article:

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Looking really good!


Sigurd
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Old 23rd August 2005, 09:33 PM   #6
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Sigurd, thank you for the translation. I was wondering if the only thing that I could do with the article was look at the pretty pictures, like a comic book.

>The power supply PCBs are right on top of the audio signal PCBs makeing the PS wires connect directly to the signal amplifiers<

Actually the regulator boards sit right under the audio signal boards, and the two were designed as pairs so that the audio signal boards "plug into" the regulator boards. The mental image that I had for this structure was how a CPU plugs into a computer motherboard, but with proximity regulation, i.e., each individual regulator sits directly underneath the circuit section that it needs to supply power to. And to tie the two boards together, rather than using additional wires, I have employed the components of the circuit and their leads. In other words, the component leads and components on one board have matching pads on the other, all of which need to be physically aligned when mating the two boards together, and then these multiple connections between the boards are soldered.

>important signal wiring is done with wires and not on the PCBs<

The signal wiring isn't made using wires, nor circuit traces, but rather with component leads which are kept separate from the board (air dielectric). And in order to increase the density of the air dielectric parts of the circuitry, the air dielectric exists in nominally 5 layers which are axially symmetrical to the board, with the center (3rd) layer running through the board (via oversized holes so that the component leads have good clearance to the board), the second and fourth layer spaced away from the top and bottom (respectively) of the board, and the first and fifth layers spaced somewhat farther away from the top and bottom of the board. Conceptually imagine a structure which looks similar to how a sewing machine stitches cloth. I can run signal leads parallel to each other or I can cross them without fear of short-circuits by choosing from any of the 5 air-dielectric layers. I call this type of structure "boundary-layer air-dielectric".

Regarding the AD829, yes the overall topology is similar, but some sections like the output stage are totally different. Rather than the AD829, the output stage of the 4-2SE shares conceptual similarities to a White follower, except that it is a fully active, complementary P-P design. However, it is a hybrid design, so FETs are not necessarily matched to FETs, nor bipolars to bipolars. You could just as easily call it a mongrel as a hybrid.

There's more but that should be enough for now.

kind regards and many thanks for the translation, jonathan carr
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Old 24th August 2005, 08:22 AM   #7
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No problem, JJonathan. My pleasure. I am a German with a Polish name living in Sweden, and I am fortunate to master many several languages

I just translated the technical stuff as I figured that this was what people wanted to read. There is also a short hiistory of Lyra, and a short review of the phono amp 4-2 P SE (which Stereoplay sounded the best that they have ever heard (together with the Lyra Titan) but it will not be their reference as they want more impedance choices for that). I did not translate what they thought about the sound of the Lyra. It goes something like this:

"...that the Lyra did not have a remote control for volume attenuation was quickly forgotten once we started listening to the Lyra. The sound from the Lyra was breathtaking. Such precision had the reviewers never heard before. Voices were extremely natural sounding. Also, the treble was produced with exactness and it even cared for the smallest details, and it was easy to follow how cymbals died away.The huge soundstgae that it produced was also unique. Even our long time reference Naim Audio NAC 552 could not match the Lyra. Stereoplay have a new reference, and this proves that enthusiasm in designers pays off."


Thanks for sharing some design details with us. You are really teasing us, and challenging us
I like that!

<but rather with component leads

I do the same just because it is the simplest way, but have recently been thinking about what are the component leads made out of? Some are pure copper with gold plating, but most are made out of lesser highend audio quality metalls.
Have you thought about using super short component leads and use for ex solid silver wire instead?
Or will the extra soldering joint destroy any poaitive gain one gets?

I am somewhat puzzled that bipolar transistors can give such good treble. I though that JFETs was the way to go a la Borbely's newer designs.

A question: the power transformers you use. What are they? and in what way are they better than toroids?




Sigurd

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Old 24th August 2005, 11:35 AM   #8
zinsula is offline zinsula  Switzerland
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Quote:
Originally posted by Sigurd Ruschkow
I am somewhat puzzled that bipolar transistors can give such good treble. I though that JFETs was the way to go a la Borbely's newer designs.
If I understood Jonathan correctly, J-FET's are used at input and BJT's for the folded cascode. For a cascode, BJT's seem to do pretty well....but I never tought about J-FET's as cascode devices in a folded cascode. Hmm....

Quote:
Originally posted by Sigurd Ruschkow
A question: the power transformers you use. What are they? and in what way are they better than toroids?
I believe these are R-Core transformers.

For John Curl's explanation not to use toroids for line level amps, read page 8 + 9 of this document:
http://www.parasound.com/pdfs/JCinterview.pdf

Jonathan Carr suggested R-Core transformers here:
http://www.diyhifi.org/forums/viewtopic.php?p=2785#2785

Maybe they have some R-Cores left:
http://www.hifituning.de/html/r-core_trafos.html

Ciao, Tino
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Old 13th May 2006, 09:22 AM   #9
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In the latest issue of Hi-Fi + (issue 43) they have an 8 page review of the lyra 4.2 se with a LOT of content about the design and construction side. They claim it is the best componant that has ever come along.

Magazines always give lavish praise in reviews so we tend to take it with a grain of salt, but trust me, you have never seen anything like this Hifi Plus review.
They talk of the Lyra like the second coming of god, with the reviewer mortaging his life to get one and the publisher about to as well. They talk of it being a pre amp that is on a level so far above all other products seen yet. And considering the exotic/expensive gear reviewed in Hi-Fi + this is saying something.

So well done Jonathon Carr!!

How is the more reasonable 6.0 coming along? (for those not in the country club)
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Old 13th May 2006, 09:40 AM   #10
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In the next latest issue of the British magazine HIFI+, there is a review of the Lyra 4-2L SE. The comments in the review were very, very positive.

You can find the review at http://www.hifiplus.com/issue43.html

I thought that SE stood for Single Ended, but it stands for Special Edition, and the 4-2L SE is an upgrade to the 4-2.

Jonathan, it would be interesting to know what you changed between the older and the new SE versions?



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Sigurd
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