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Why a Torroidal instead of an R-core Transformer in digital?


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Someone here suggested that R-Core was better for Dacs. I went and checked and it seems that R-Cores are easier to make as the coil wrapping is less tight. The higher tolerance in the torroidal to get it right means that there is less EMI radiation coming off and that is a good thing in digital.

 

Is that evereyone's understanding?

Edited by wis97non
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Someone here suggested that R-Core was better for Dacs. I went and checked and it seems that R-Cores are easier to make as the coil wrapping is less tight. The higher tolerance in the torroidal to get it right means that there is less EMI radiation coming off and that is a good thing in digital.

 

Is that evereyone's understanding?

What you have stated is mostly true. However, the reason why R-core transformers are the best choice for ALL low level audio applications, is due to their far lower coupling. This means that any mains-bourn interference will be greatly attenuated by an R-core transformer, compared to a toroidal. E-I type transformers lie somewhere in the middle. Better than toroidals, but not as good as R-core types. And yes, radiation is higher with both R-core and E-I types, but that can effectively dealt with by either good shielding, or placing the transformer in a separate enclosure.

Edited by Zaphod Beeblebrox
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..... mains-bourn interference will be greatly attenuated by an R-core transformer......

 

That would go a little way to explain why the Lampi I heard was disappointing. It had a single toroid that was unshielded.

 

In contrast note the design below for a quality DAC. Three seperarte R-tranies shlieded by thick aluminium.

 

M74s.JPG

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Thanks Zaphod, but isn't mains bourne interference dealt with by chokes and capacitors?

It should be, but every bit helps. And R-core transformers are around 100 times better than toroidals. They're not just a little bit better. They are spectacularly, brilliantly better. The reality is, that for anyone purporting to build the best product possible, then the best components should be used (within cost constraints, of course). I will remind you once more: Toroidals are the very WORST choice of power transformer for low level (audio) components. ANY transformer will make a better choice.

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Cost is not a constraint as both types cost about the same and from reading from Goldmund (yes, I know this is an amp):

 

A very low level of magnetic radiation (use of high quality toroidal transformer) so the amp can be located close to a computer monitor or a TV set.

 

The JOB Amplifier is DC coupled with a new type of DC Servo Control avoiding any DC offset. 

DC coupling is the only way to avoid time error in low frequencies. It avoids the usual boominess of the speakers bass response. So you get Tight Bass.

 

So I see that clever design and compromises are NOT subject to dogma. R-Cores need to have their own design constraints (seems like you need a Faraday cage to protect against MASSIVE magnetic radiation bleed) and toroids can be shielded by wraps and protected by other components such as massive chokes.

Steel is a better shielding metal than alum (for RFI), I was told.

The proof of the pudding is in the eating and I dont see anywhere there is a negative impact in Lampi, Calyx Femto, Phasure or VAD Dac performance from using torrods, so the tradeoff apparently works for them.

Edited by wis97non
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Cost is not a constraint as both types cost about the same and from reading from Goldmund (yes, I know this is an amp):

 

A very low level of magnetic radiation (use of high quality toroidal transformer) so the amp can be located close to a computer monitor or a TV set.

 

The JOB Amplifier is DC coupled with a new type of DC Servo Control avoiding any DC offset. [/size]

DC coupling is the only way to avoid time error in low frequencies. It avoids the usual boominess of the speakers bass response. So you get Tight Bass.

 

So I see that clever design and compromises are NOT subject to dogma. R-Cores need to have their own design constraints (seems like you need a Faraday cage to protect against MASSIVE magnetic radian bleed) and toroids can be shielded by wraps and protected by other components such as massive chokes.

Steel is a better shielding metal than alum, I was told.

The proof of the pudding is in the eating and I dont see anywhere there is a negative impact in Lampi or VAD Dac performance from using torrods, so the tradeoff apparently works for them.

Points:

* Almost no one uses CRT TV sets any longer. Magnetic fields are, therefore inconsequential in such environments. They do not affect modern TV sets (plasma, LCD, O-LED, etc).

* Shielding materials will depend on the desired outcome. The best shielding material is silver, followed closely by copper, then aluminium. Conductivity is the key to good shielding. Steel is way down the list. Magnetic shielding is best accomplished by 'mu-metal'. Mu-metal is around 5 times more effective than iron. Steel is bad news, due to magnetic remnance.

* Unless you have actually tried using an R-core tranny in a Lampi or VAD DAC, then you can never claim that toroidals are superior. Toroidals are used because they are convenient, cheap and require less shielding. They are not a superior transformer for a low level audio product.

Edited by Zaphod Beeblebrox
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They are not a superior transformer for a low level audio product.

 

Considering that induced hum from the magnetic fields of transformers is an obvious problem in low level audio gear surely they must be.

 

As for the close coupling and wide bandwidth of toroids making them susceptible to passing mains-bourne interference, isn't low level audio gear the perfect place for decent mains filtering (as opposed to power amplifiers where it isn't).

 

And if you want to go even further you can buy shielded, as in inter-winding electrostatic shielded toroids.

 

For efficiency and regulation a toroid is also superior to an r-core.

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 ......... Unless you have actually tried using an R-core tranny in a Lampi or VAD DAC, then you can never claim that toroidals are superior. Toroidals are used because they are convenient, cheap and require less shielding. They are not a superior transformer for a low level audio product.

 

Thanks for your expert opinion once again Zaph.

 

It appears that this thread may be fueled by some unarguable "logic"

 

a. Lampi use toroids

b  Lampi is and will always be the greatest DAC in the entire creation

c  Therefore torioids must be the best

 

You cant argue with that Zaph. Convert now. It only costs $6,499.99.

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Or maybe you again try to prove yourself against the world saying that Lampis dont sound good when all objective people say otherwise.

 Given that torrids and r-cores cost about the same ( and are equally available) and the tube guys use them (also the Phasure Dac, Antelope Eclipse,Anedio Dac, X-Sabre, Calyx Femto and the Aurelic Vega, to name a few prominent ones), perhaps they see that magnetic fields are the greater nemesis, as they can deal with mains grunge more efficiently with other means.

 

You and anyone else can choose what you like, but chill with the agenda.

Edited by wis97non
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I found the links to the change over for the Havana dac.

It does not seem anyone has any extra shielding but from reading the forums, it is a good sound upgrade.

http://www.head-fi.org/t/310441/mhdt-havana-dac/1515#post_7912264

https://sites.google.com/site/computeraudioorg/mdht-havana-dac-modifications

 

I would not know myself it there is any improvement but thought it might be worth mentioning.

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Ive used toroidals, E core and R core in PSU's I have made up. My my laypersons perspective, it boils down to the application and the quality of the trafo whatever type it be. For example, I find a toroid is most useful in source component type supplys when something like a teddyreg is used, the resulting output has a lower noise floor than the equivalent made with either R or E core, and I guess thats because of the radiated noise. I found a good E core worked best with a choke/filter type of PSU with an LT1084 reg, a toroid in this case did let through some mains borne noise wheras the output was quieter with the E core. I like Rcore for low power and digital stages, as long as the trafo is well shielded or even in a seperate chassis.  Toroids definitely for power output stages.

Across all types, there is quite a range of build quality, with some at the rubbish end having bad regulation, bigger temp swings, physically noisy windings, and just giviing a slightly untrustworthy aura.

While I'm no expert, I have invested quite a lot of recent time building and understanding PSU's, currently using a main system that is all DIY aside from the speakers.

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honestly if you cant make a modern well made toroid work well for you in low noise source components, I would suggest you build a better power supply and an DAC/ADC/Line stage/headphone amp with better PSRR.

 

toroids are used here in the LPUHP. SNR is 125.335dB vs 1V; in the FFT the mains and its harmonics are all -130dB/V you are saying this is a problem? its not even an overkill regulator, just a well laid out one.

 

toroids also used here in the 3rd pic onwards, in both the DAC, DAC IV stage and the ADC sections of this rather high end measurement device built as an upgrade the front end of an audio precision system 2 (already fully optioned up)… yes an upgrade to an AP2, because previous measures of this IV stage were bouncing against the noise floor

 

so wheres that horrible noise and/or distortion?

 

toroids can be bad, but well made toroids, perhaps with electrostatic shielding between primary and secondary windings (not used here, but I usually go for this) are now very good. They also have the benefit of allowing you to have your power supply in the same chassis; in many cases I believe 2 box builds are counterproductive, just an excuse for manufacturers to charge more.

 

dont get me wrong, R-Cores can be good also, but I do think their FOTM status and advantages are largely overrated and more about fashion. there are also hybrid R-Core/Toroid units available which look pretty good.

 

pretty excellent IMD performance below, well everything is pretty special really, not a single digital THD at 1khz measure in sight. its a discrete IV with no global feedback on the DAC too.

post-111873-0-38667500-1379664104_thumb.

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post-111873-0-98035500-1379664189_thumb.

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post-111873-0-74941100-1379664219_thumb.

post-111873-0-01378100-1379664238_thumb.

post-111873-0-27290900-1379664272_thumb.

post-111873-0-65842600-1379664285_thumb.

Edited by fetischizm
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given Paul makes very high dollar shunt regulated PSUs I would hope it wouldnt matter what type of transformer he used. if it did they would be pretty **** shunt regs

Why do you think it would be ???? shunt regs if it made a difference just wondering since my power cables make a difference?

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and?

 

there are numbers of designs that put them inside, but that doesnt change the fact they have higher emissions than toroids. it wasnt my assertion they are best placed at a distance, but that may be the case depending on the design/purpose. whats the go with that distant choke? it is a choke or inductor yes with the red wiring?

Edited by fetischizm
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