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Lyra Connoisseur 4-2L SE: What a masterpiece!
Lyra Connoisseur 4-2L SE: What a masterpiece!
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Old 18th May 2006, 09:33 PM   #21
karma is offline karma  Canada
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amazing woodwork
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Old 18th May 2006, 09:40 PM   #22
jleaman is offline jleaman  Belgium
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Quote:
Originally posted by karma
amazing woodwork

Just made 4 Look really simular to these too.
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Old 19th May 2006, 07:32 AM   #23
Sigurd Ruschkow is offline Sigurd Ruschkow  Sweden
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Hi Jonathan,

really interesting to read that you do NOT use heavy "lead" mats nor rubber to dampen the assemblies. I have been using it for many years, and I think my ideas came from the time when I built loudspeakers in the 80s. Add mass to lower the resonance freq and also to lower the amplitude with which any assemblies might vibrate with.

The "lead"mats that I use are actually not made out of lead, but of some rubber compound material, so there is no problems with ROHS or my personal health. I am fully Śrp ROHS even though it has caused some problems for me, aswell increased costs due to the need to invest in new soldering eq. and skills.

I also use Teflon PCBs for low voltage applications like RIAA (both MM and MC) to minimise influnece from vibrations onto the sensitive circuits.

I think I have gone to the extreme in my latest assembly of a remote controlled attenuator system where I dampen the PCBs by putting them into clay and also to add clay onto the top of the PCBs. At least it dampens the sharp noise from the clicking relais

Now, your ideas to control resonance is really neat and intelligent! I guess one cannot use clay inside a consumer product....

Maybe I am going in the wrong direction when just adding mass to a mechanical system. What I think I do is to lower the resonance freq by adding mass, but maybe I am moving the resonance freq to a freq range where there is lots of energy in the music (ie 50 - 200 Hz). Instead I should add stiffness to the mechanical system so the resonace freq goes up towards a freq range ehere there is much less energy in the music (above 1kHz or so). Less energy that can trigger a resonance disturbance in the assembly.

And this is probably what you do in the 4-2 preamp.



Best regards,
Sigurd

Quote:
Originally posted by jcarr
Hi again Sigurd:

In general, for resonance control, I find that there is an optimum degree of coupling assemblies and components together - neither too tight nor too loose. Too loose and the individual assemblies can resonate, too tight and the entire stucture will resonate as one.

The chassis of the main unit is made from machined and shot-peened aluminum plates, while the wood cabinet is made and mounted so that it constrains and partly damps the remaining resonances of the aluminum (what you think are aluminum side plates are in fact wood).

Rather than trying to damp the electronic assemblies themselves, or rather than mounting the assemblies directly to the chassis, I now use various types and forms of plastic to provide greater isolation between assemblies as well as to the chassis (similar in concept to the plates under the caps in the PS).

I have experimented with rubber and lead damping, but don't use them because I don't necessarily like all of what these do to the sound. Also, lead in electronic components runs afoul of ROHS regulations, so for a product in thsi day and age it is a non-starter.

best regards, jonathan carr
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Old 19th May 2006, 07:35 AM   #24
Sigurd Ruschkow is offline Sigurd Ruschkow  Sweden
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Peter,
good question!

I have an idea and that is to use copper tracks and ontop of them plate with silver and then plate with gold. The gold will both protect the silver and maybe add some warmth to the sound. The silver will be there for its sound qualities. The copper I guess have to be there as one has to have something to plate onto :-)



Best reagrds,
Sigurd

Quote:
Originally posted by Peter Daniel
Jonathan,

What is your opinion on different board materials: FR-4, teflon, arlon, gold plating, mask, no mask? Any specific sonic advantages?

thanks, Peter
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Old 19th May 2006, 10:01 AM   #25
Bobken is offline Bobken  United Kingdom
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Hi,

Yes, it is a good question.

I have always thought that solder masks will quite likely have some small affect on the sound, but have not (yet) tried a direct comparison here, with no other changes.

Whether solder mask is 'audible' or not, it will act as a dielectric with all of the traces being covered with this material.

I did try direct comparisons between conventional glass fibre boards and teflon in a MC head-amp, and the teflon board was 'cleaner' sounding, presumably due to the better dielectic.

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Old 19th May 2006, 09:07 PM   #26
jcarr is offline jcarr  United States
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Originally posted by rdf
If I understand correctly, the air dielectric construction simplified managing high frequency circuit stability and appears to have enough intrinsic RF rejection to permit a great deal of latitude in chassis design. Am I on the right track?
I think so . Being able to get the circuit off the board minimizes parasitic capacitances (and leakages) on critical nodes; being able to work point-to-point enables inductances to be reduced, and the circuit is more intrinsically stable as a result. The stacked boards of the 4-2SE are fully ground and power-planed, and provide a fair amount of shielding on their own (especially when RF-sensitive nodes are located between the boards). And it helps if the circuitry is designed with at least some foresight as to its behaviour when forced to operate in an RF-prone environment.

The RF sensitivity of a circuit is also related to its effectiveness as an antenna - a physically smaller circuit (and more compact wiring harnesses) means a less sensitive antenna means less pickup of environmental RF.

The 4-2SE is a wide-band circuit in a chassis that is pretty much unshielded, but I have not noticed (nor heard of) any real problems pertaining to RF. In fact, I've had situations at audio shows where RF was leaking in from both the hotel walls and the local AM stations, and other preamps manifested RF issues while the 4-2 didn't. OTOH, I don't run 100dB+ speakers in an RF-rich environment - if I did, perhaps my chassis designs, circuit designs (or both) would be different.

However, I've already done an excavated-from-solid chassis in an earlier product - the 3.0, and I can't say that the 4-2SE, open chassis and all, appears to be any inferior in terms of RF breakthrough.

regards, jonathan carr
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Old 19th May 2006, 09:10 PM   #27
MikeW is offline MikeW  United States
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What do you consider RF? 2 to 18 GHz ?
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Old 19th May 2006, 09:31 PM   #28
jcarr is offline jcarr  United States
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Most of the problems that I have noticed in real life seem to come from AM, CB, occasionally wireless WiFi and cellular phones. FWIW, doing audio shows in a downtown location seem to trigger far more problems than dealer or home installations.

regards, jonathan carr
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Old 20th May 2006, 12:25 AM   #29
MikeW is offline MikeW  United States
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Nextel just bought up the bottom end of the ENG spectrum (1999 MHz to 2030 MHz). There will be more cell phone traffic in that band.
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Old 20th May 2006, 03:57 AM   #30
Panelhead is offline Panelhead
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Default That is minor

Looking out from my front yard, I can see 7 televsion towers, at most 10 miles for the furthest.
This is why I line most aluminum chassis with mumetal. Try to shield as well as possible.
The tube gear with high impedances seems to be okay. The solid stage with "virtual grounds" gets eaten alive. The solid state gear with low impdeances works best.
This is with 100 dB efficient speakers.
Guess I need to blow either some of the kids college money or the old ladies next car money and give the 4-2L a listen. Looksalone justify the splurge.
Where is the closest dealer with stock?

George
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