R-Core OUTPUT Transformers......... dating back to 2012

[drlowmu]

07 - 23 - 2022

I came across this information today. In December 2012, people in Brazil were making amps with Power and Output transformers, using R-Cores. !!

Do a Google Search " R-Core, Jalbum, KDK ". They seem to claim, in one article, of people in Korea " inventing " the R-Core. Their craftsmanship looks prototypical, and questionable in quality. The Brazil amp looks very crude and cheap , to be generous when describing it.

The Softone Transformer people of Japan say on their website that an engineer from Kitamura Kiden in Japan invented the R-Core and has the Patent on it.

There are certain unique, intrinsic, benefits to an R-Core., VS an E-I core, and also a Toroid core approach.

I am too busy now with amplifier building, to look into this. If anyone wants to study it, GOOGLE search is a starting place.




Two FMs were previously unable to find any web mention of R-Core OUTPUT Transformers, other than Softone. This above, is it.

It would be wonderful if more choices existed and people tried to build an all out R-Core SE OUTPUT XFR. Softones could offer a bigger core, for a better extreme bottom, etc etc.

The existing Softone RW-20s are very nice - audibly lower in distortion. ( No interleaving needed, with cross current bucking , and no " one winding wound over another ", as separate primary and secondary winding bobbins are used. ).

After 800 hours of break-in doing critical long term listening, these RW-20s just need a better extreme low end, as in a larger core !!

Jeff

While not an R-Core, this looked interesting at first glance :

https://www.aliexpress.com/i/2251832771851174.html?gatewayAdapt=4itemAdapt

 

[arj]

...

The Softone Transformer people of Japan say on their website that an engineer from Kitamura Kiden in Japan invented the R-Core and has the Patent on it.

...

incidentally My CD transport is by Softone and at that time was also thinking of their amp but it did not have enough power for my speakers.

The transport is of excellent build and have not found any other CDMPro2 to be that much better ( other than the esoteric ones)

I would suspect their Phono would be something that wold punch far above what its price might suggest.

 

[drlowmu]

incidentally My CD transport is by Softone and at that time was also thinking of their amp but it did not have enough power for my speakers.

The transport is of excellent build and have not found any other CDMPro2 to be that much better ( other than the esoteric ones)

I would suspect their Phono would be something that wold punch far above what its price might suggest.

Hello arj,

I just looked over their Model 4 Phono unit schematic.

It should as you suspect and say , " punch well above it's price ". I agree. Basic topology is simple, decent, and it cleverly uses my favorite Phono stage vacuum tubes, 12AX7s.

Technically, what I find missing is that the first stage's B+ level is too low, to optimize the SWING in that first 12AX7 gain stage..

Only 107 VDC on the plate.

107 VDC Ea is too " sleepy " sounding to hear !!! Usually 150 VDC is the minimum. Also, 175 VDC would sound easily superior to 150 VDC.. And 195 VDC on the plate, would be ideal sounding !! The second stage is very good, at 209 VDC, and with not enough current to wear out the tubes.

I personally do not know enough about employing solid state devices ( FETs ) to co-ordinate those solid state devices in that MODEL 4 circuit - so as to re-adjust the first stage's plate voltages higher.

IF I knew how to do that, I would possibly DIY copy / develop an improved version their phono circuit.

If any experienced ( in solid state and tubes ) F.M. would like to coordinate, and look into designing better op points, please P.M. me. We can perhaps evaluate changes that could be made., and share with HFV DIYers wanting a really "great " circuit.

Is any F.M. game for a redesign...... to publish for others?? Maybe Hari Iyer knows enough. or another good E.E. type, acceptable to me, can volunteer. . I think Indian Ears may perhaps help out ? Maybe us three ?? That would surely be a pleasure.

I hesitate to commit money to any commercial product, or build project, when you can before-hand tell, and know, how to make it sound better than slightly above average .

Jeff



A DIY build project unique to and for HFV F.M.s .

Who will help ??

Maybe a new thread needs to be done .

Let me hear from you please. I need help !! Easy to use great sounding / available parts here. For me, it may possibly be this, or Jim Hagerman's Coronet phono circuit adaptation. ( No negative EQ feedback , and upping the VDC across Directly Coupled 12AX7 plates, from 150 VDC to 195 VDC. Fun stuff here to contemplate !!

Jeff

 

[drlowmu]

07 - 24- 22 ...........ADDENDUM to the original Softone Model 4 PHONO unit post, just above :

To clarify the initial PHONO Stage suggestions above, any MODEL 4 redo I had in mind will be to

a) simplify the circuit, and
b) minimize parts and circuit complexity,
c) maximize parts quality..

For example :

** Eliminate any and all the active solid state regulation devices of B+, zeners, etc., ( noise considerations, etc. ).

** Eliminate each and every RELAY Softone EEs used to switch signals / signal paths.

** Use film caps , and not allow electrolytic capacitors, in almost all locations.

** Greatly improve the cathode resistor bypassing capacitance , for each 12AX7 triode stage. Certainly absolutely NO electrolytic Rk bypasses allowed.

** Likely use the best sounding thin film resistors on the signal path. A well-current ( proven ) resistor reference is Caddock TF 020.



Possibly Caddock's MK-132 series.





We can also systematically evaluate Intron resistors, a local ( Thane !! ) Indian brand thin film resistor manufacturer.

https://intronresistors.com/wp-content/uploads/2021/07/BA_Series_20_21.pdf compare Introns to Caddock TF020s !!!

If we go forward, this will be an ALL-OUT effort, with maximum Phono playback performance as the key over-riding design goal, in every possible way. AS good as we can do " or forget starting upon the project. "

Can I get some help with the solid state Mos FET application ?? My personal vote, for my own use and listening, goes to tube rectification of the B+. . It usually sounds better.

Thanks !! Jeff

 

[drlowmu]

07 - 24 -2022 ...................... A friend's initial response, the first ......................................


( Note : Change " shy" to " why " in first paragraph ):







Here is my own modded Cornet Directly Coupled Phono preamp. All-tube topology. It has a Passive RIAA ( no feedback ) located between -between-two-stages of 12AX7s. Cap coupled in and out of a 12B4A finals / line stage.

All lovely sounding 9 pin NOVALS tubes. No compromised cathode followers, anode driven !! Final tube idles at over 30 mA. to easily power a constant 10K Z L-Pad volume control and Interconnect Cables.:



Jeff

 

[arj]

Thanks Jeff

Just to clarify I have never heard this phono although based on my ownership experience of their CD transport i do believe this will be a solid value for money build. their case itself is built of stainless steel and an excellent power supply.

 

[drlowmu]

07 - 24 -2022 ...................... A friend's initial response, the first ......................................


( Note : Change " shy" to " why " in first paragraph ):

View attachment 70850





Here is my own modded Cornet Directly Coupled Phono preamp. All-tube topology. It has a Passive RIAA ( no feedback ) located between -between-two-stages of 12AX7s. Cap coupled in and out of a 12B4A finals / line stage.

All lovely sounding 9 pin NOVALS tubes. No compromised cathode followers, anode driven !! Final tube idles at over 30 mA. to easily power a constant 10K Z L-Pad volume control and Interconnect Cables.:

View attachment 70849

Jeff

Yikes Jim,

The Softone Model 4 is a very uninspired tube design, on closer look.. It has two unneeded " grid stoppers ", useless series resistors, which total 560R and 5.6K, or 6.26 K Ohms. UGH. Fooey.

You and I would never use grid stoppers / " music stranglers ", - in such a way.

Additioally, the Softone MODEL 4 circuit, between tube stages, has a whopping 180K and 43K of added series resistances as you pointed out. The entire audio signal has to also pass though, these two added resistors, in series.

In contrast, the 2019 redesigned Jim Hagerman inspired Cornet phono DC circuit has only 10K Ohms, a single Caddock TF020, in those equivalent circuit locations.

10K ............. VS: ................ 229.26K.

Can we imagine / think that four Softone resistors, in series with the signal,......... totaling all of of 229.26K, will quite easily be way-outperformed with a planned single 10K Caddock TF020, ...... and a short 18 AWG silver wire connection ????? I certainly can !!

Yes, I need to execute this modded 2019 Cornet Phono circuit, next - right after 2022's TRIPLE 6005 mono amps.!!! Begin in Q4, 2022, or Q1 2023.

About 13.000 L.Ps await.

 

[Hari Iyer]

Hello arj,

I just looked over their Model 4 Phono unit schematic.

It should as you suspect and say , " punch well above it's price ". I agree. Basic topology is simple, decent, and it cleverly uses my favorite Phono stage vacuum tubes, 12AX7s.

Technically, what I find missing is that the first stage's B+ level is too low, to optimize the SWING in that first 12AX7 gain stage..

Only 107 VDC on the plate.

107 VDC Ea is too " sleepy " sounding to hear !!! Usually 150 VDC is the minimum. Also, 175 VDC would sound easily superior to 150 VDC.. And 195 VDC on the plate, would be ideal sounding !! The second stage is very good, at 209 VDC, and with not enough current to wear out the tubes.

I personally do not know enough about employing solid state devices ( FETs ) to co-ordinate those solid state devices in that MODEL 4 circuit - so as to re-adjust the first stage's plate voltages higher.

IF I knew how to do that, I would possibly DIY copy / develop an improved version their phono circuit.

If any experienced ( in solid state and tubes ) F.M. would like to coordinate, and look into designing better op points, please P.M. me. We can perhaps evaluate changes that could be made., and share with HFV DIYers wanting a really "great " circuit.

Is any F.M. game for a redesign...... to publish for others?? Maybe Hari Iyer knows enough. or another good E.E. type, acceptable to me, can volunteer. . I think Indian Ears may perhaps help out ? Maybe us three ?? That would surely be a pleasure.

I hesitate to commit money to any commercial product, or build project, when you can before-hand tell, and know, how to make it sound better than slightly above average .

Jeff

View attachment 70842

A DIY build project unique to and for HFV F.M.s .

Who will help ??

Maybe a new thread needs to be done .

Let me hear from you please. I need help !! Easy to use great sounding / available parts here. For me, it may possibly be this, or Jim Hagerman's Coronet phono circuit adaptation. ( No negative EQ feedback , and upping the VDC across Directly Coupled 12AX7 plates, from 150 VDC to 195 VDC. Fun stuff here to contemplate !!

Jeff

The FETs are used to increase the current from the previous stage to the next stage by a factor of 10. This will give more juice to the mids and highs. Also the FETs acts like a buffer in this case and helps to couple both the stages. There is some scope for experimentation to reduce the source resistor to increase the current if more juice and air is required. Also the FETs help in impedance matching.

For removing the grid resistors, it would again be an experiment as that could increase noise due to very low level signals found in the phono stage especially the input ones. Also the second grid resistors form the part of the RIAA EQ and should not be removed and is also handles the I to V conversion. Also the R120 (560 ohms) in the output should not be removed as it does the I to V conversion.

For modifications - i would stick to changing all the electrolytic capacitors to Film types, resistors to thin film like Introns. That's it. If i require more high freq air then modify the 33K source resistor to around 15K to double the current by listening.

 

[drlowmu]

The FETs are used to increase the current from the previous stage to the next stage by a factor of 10. This will give more juice to the mids and highs. Also the FETs acts like a buffer in this case and helps to couple both the stages. There is some scope for experimentation to reduce the source resistor to increase the current if more juice and air is required. Also the FETs help in impedance matching.

For removing the grid resistors, it would again be an experiment as that could increase noise due to very low level signals found in the phono stage especially the input ones. Also the second grid resistors form the part of the RIAA EQ and should not be removed and is also handles the I to V conversion. Also the R120 (560 ohms) in the output should not be removed as it does the I to V conversion.

For modifications - i would stick to changing all the electrolytic capacitors to Film types, resistors to thin film like Introns. That's it. If i require more high freq air then modify the 33K source resistor to around 15K to double the current by listening.

Thanks Hari.

I hear your " E.E. training explanation " as to why to use a grid stopper.

In an all- tube circuit, grid stoppers are not often needed.

It is always a degrade in sound ( by having to send the fragile audio signal, through an extra series part. Imagine sending every musical note, of a 100 piece Chorus, a full Symphony orchestra, and a pipe organ, simultaneously through an added series-resistive part !!! ( Beethoven's Ninth ). Less is more.

Both my friend " Jim" in this thread, and my Audio Mentor " Dennis" will not use grid stoppers. It is perceived by us three as an EE type person's sonic degrade, despite any EE's knowledge / reasoning as to " why " to add them. No thank you, not for us three to listen through my friend.

The KT88 SE DC amp circuit I did for you in 2020 has NO grid stoppers.

Add just one resistor in series on either of the amp's two tubes' control grids, and it will become an instant sonic degrade. Especially IF the rest of the circuit is optimally wired, and the entire audio system is executed well above the usually - seen " mid fidelity " audio performance level so many people enjoy..

At this juncture, after the last 24 hours of discussion on HFV, I now have little interest left in the Softone / tube - Mos FET circuit.

I will pursue the all-tube-only Cornet as I modded it in 2019, for my future PHONO playback use. It is far more elegant. Simpler. Consider this : there is 29 times less series resistances between these two phono playback circuits.

It is much like entering a automotive DRAG race, with five tons of weight added to the rear seating area of an automobile. Yes, the Mechanical Engineer will inform me this weight gives the tires more traction from a dead stop. But the motor now has to be saddled with the design's added five TONS of weight.

Not for my money, DIY build effort, and / or ears, thank you !!

Life is too brief to be saddled with any inelegant designs, less than excellent.


Appreciate you - and every post you contribute !! Bravo. Thanks.

Jeff

 

[manek]

07 - 23 - 2022

I came across this information today. In December 2012, people in Brazil were making amps with Power and Output transformers, using R-Cores. !!

Do a Google Search " R-Core, Jalbum, KDK ". They seem to claim, in one article, of people in Korea " inventing " the R-Core. Their craftsmanship looks prototypical, and questionable in quality. The Brazil amp looks very crude and cheap , to be generous when describing it.

The Softone Transformer people of Japan say on their website that an engineer from Kitamura Kiden in Japan invented the R-Core and has the Patent on it.

There are certain unique, intrinsic, benefits to an R-Core., VS an E-I core, and also a Toroid core approach.

I am too busy now with amplifier building, to look into this. If anyone wants to study it, GOOGLE search is a starting place.


View attachment 70836

Two FMs were previously unable to find any web mention of R-Core OUTPUT Transformers, other than Softone. This above, is it.

It would be wonderful if more choices existed and people tried to build an all out R-Core SE OUTPUT XFR. Softones could offer a bigger core, for a better extreme bottom, etc etc.

The existing Softone RW-20s are very nice - audibly lower in distortion. ( No interleaving needed, with cross current bucking , and no " one winding wound over another ", as separate primary and secondary winding bobbins are used. ).

After 800 hours of break-in doing critical long term listening, these RW-20s just need a better extreme low end, as in a larger core !!

Jeff

While not an R-Core, this looked interesting at first glance :

https://www.aliexpress.com/i/2251832771851174.html?gatewayAdapt=4itemAdapt

Viren from Lyrita audio used to or still uses R-core as output transformers from Delta transformers. I have his 6SN7 based preamp cum headphone amplifier for probably 12+ years now or more. Still works like a charm. Just love those tubes for preamp and headphone amp duty.

 

[drlowmu]

Viren from Lyrita audio used to or still uses R-core as output transformers from Delta transformers. I have his 6SN7 based preamp cum headphone amplifier for probably 12+ years now or more. Still works like a charm. Just love those tubes for preamp and headphone amp duty.

Hello Manek,

Thank you so much for posting. DELTA has become the third Indian Transformer winder ( I am aware of ) based in India who winds R Cores. In the USA, we have " Magnetic Components ", run by Indian - born individuals, with a R Core capability.

Looking at DELTA's web pages, they seem to offer the same sizes and VA choices for R-Cores, as does India's huge SHILCHAR company.

R-CORE TRANSFORMER

Kindly simply re-confirm that the DELTA R Core inside your unit is wound , not as a power transformer, but as an OUTPUT transformer. It is easy to mistake one for another.

If it is an output transformer, and also about a dozen years old, that is impressive to me, that DELTA did such a wind / design..

Up until your posting today, the only other company who wound R Core outputs was the R Core International Patient holder : Kitamura-Kiden of Japan. They wind OUTPUTS which are marketed in several choices, by SOFTONE AUDIO, in Japan. Friends and I have purchased about 15 of their RW-20 units. Pretty nice, not perfection ........but close, perhaps rate it as " excellent plus. "

A third India-based R-Core winder I was aware of was PRECISION Transformers, in Chennai. When I Googled them today, it says they are Permanently Closed. If this is correct, that is a shame. Anyone able to confirm this?





I think there are advantages, inherent in an R-Core, that will allow perhaps the best possible OUTPUT transformer, for a S E amplifier to be wound.

What I am thinking of is there is no need to do "Interleaving " of the winding, to maintain wide bandwidth. Supposedly, the more interleaving the better the high frequency bandwidth. BUT, each interleaving places a opposite direction current loop into the wind. One winding direction BUCKS the other's, a bit. This lessens low level detail retrieval through the winding, VS all the R Core's windings ......all done in a uniform direction.

Plus, with an R Core, the primary and secondary windings are done on separate bobbins, not one on top of the other. Audible distortion is immediately noticeably lower !! I am only GUESSING at cause and effects here. But I know what I hear at home. So likely, does Hari iyer.

The only thing missing from a Softone, is the 50 VA core size is skimpy, and extreme low bass response has not been optimized. The bass which all my RW-20s play, is clean sounding and quick after an 800 hour break - in, but just a tiny bit bass shy. All else - is AOK.

Jeff

 

[Dr.Gary]

Hello Manek,

Thank you so much for posting. DELTA has become the third Indian Transformer winder ( I am aware of ) based in India who winds R Cores. In the USA, we have " Magnetic Components ", run by Indian - born individuals, with a R Core capability.

Looking at DELTA's web pages, they seem to offer the same sizes and VA choices for R-Cores, as does India's huge SHILCHAR company.

R-CORE TRANSFORMER

Kindly simply re-confirm that the DELTA R Core inside your unit is wound , not as a power transformer, but as an OUTPUT transformer. It is easy to mistake one for another.

If it is an output transformer, and also about a dozen years old, that is impressive to me, that DELTA did such a wind / design..

Up until your posting today, the only other company who wound R Core outputs was the R Core International Patient holder : Kitamura-Kiden of Japan. They wind OUTPUTS which are marketed in several choices, by SOFTONE AUDIO, in Japan. Friends and I have purchased about 15 of their RW-20 units. Pretty nice, not perfection ........but close, perhaps rate it as " excellent plus. "

A third India-based R-Core winder I was aware of was PRECISION Transformers, in Chennai. When I Googled them today, it says they are Permanently Closed. If this is correct, that is a shame. Anyone able to confirm this?

View attachment 71049



I think there are advantages, inherent in an R-Core, that will allow perhaps the best possible OUTPUT transformer, for a S E amplifier to be wound.

What I am thinking of is there is no need to do "Interleaving " of the winding, to maintain wide bandwidth. Supposedly, the more interleaving the better the high frequency bandwidth. BUT, each interleaving places a opposite direction current loop into the wind. One winding direction BUCKS the other's, a bit. This lessens low level detail retrieval through the winding, VS all the R Core's windings ......all done in a uniform direction.

Plus, with an R Core, the primary and secondary windings are done on separate bobbins, not one on top of the other. Audible distortion is immediately noticeably lower !! I am only GUESSING at cause and effects here. But I know what I hear at home. So likely, does Hari iyer.

The only thing missing from a Softone, is the 50 VA core size is skimpy, and extreme low bass response has not been optimized. The bass which all my RW-20s play, is clean sounding and quick after an 800 hour break - in, but just a tiny bit bass shy. All else - is AOK.

Jeff

I'd really like to know how many other members of this forum have also experienced the need for an audio output transformer to have an 800 hour break-in period.

 

[manek]

I'd really like to know how many other members of this forum have also experienced the need for an audio output transformer to have an 800 hour break-in period.

Not me, 800 hours ? Who counts 800 hours ? Its difficult to jeep track of 100. Id memory serves me right, i could hear a slight difference post a week or 15 day max. Post that stable performance.

Hello Manek,

Thank you so much for posting. DELTA has become the third Indian Transformer winder ( I am aware of ) based in India who winds R Cores. In the USA, we have " Magnetic Components ", run by Indian - born individuals, with a R Core capability.

Looking at DELTA's web pages, they seem to offer the same sizes and VA choices for R-Cores, as does India's huge SHILCHAR company.

R-CORE TRANSFORMER

Kindly simply re-confirm that the DELTA R Core inside your unit is wound , not as a power transformer, but as an OUTPUT transformer. It is easy to mistake one for another.

If it is an output transformer, and also about a dozen years old, that is impressive to me, that DELTA did such a wind / design..

Up until your posting today, the only other company who wound R Core outputs was the R Core International Patient holder : Kitamura-Kiden of Japan. They wind OUTPUTS which are marketed in several choices, by SOFTONE AUDIO, in Japan. Friends and I have purchased about 15 of their RW-20 units. Pretty nice, not perfection ........but close, perhaps rate it as " excellent plus. "

A third India-based R-Core winder I was aware of was PRECISION Transformers, in Chennai. When I Googled them today, it says they are Permanently Closed. If this is correct, that is a shame. Anyone able to confirm this?

View attachment 71049



I think there are advantages, inherent in an R-Core, that will allow perhaps the best possible OUTPUT transformer, for a S E amplifier to be wound.

What I am thinking of is there is no need to do "Interleaving " of the winding, to maintain wide bandwidth. Supposedly, the more interleaving the better the high frequency bandwidth. BUT, each interleaving places a opposite direction current loop into the wind. One winding direction BUCKS the other's, a bit. This lessens low level detail retrieval through the winding, VS all the R Core's windings ......all done in a uniform direction.

Plus, with an R Core, the primary and secondary windings are done on separate bobbins, not one on top of the other. Audible distortion is immediately noticeably lower !! I am only GUESSING at cause and effects here. But I know what I hear at home. So likely, does Hari iyer.

The only thing missing from a Softone, is the 50 VA core size is skimpy, and extreme low bass response has not been optimized. The bass which all my RW-20s play, is clean sounding and quick after an 800 hour break - in, but just a tiny bit bass shy. All else - is AOK.

Jeff

Thanks for Pointing me to Shilchar. If the ratings between delta and shilchar are spot on then one must be winding it for the other I guess.