Good question: Why DON"t we see R-core transformers in new high end equipment?

Or are they out there and not being noticed? I haven't seen them.

http://leftyshefty.blogspot.com/2013/04/whatever-happened-to-r-core-transformers.htm

 

That's because even your link doesn't exist.
The "l" in html got left off.
http://leftyshefty.blogspot.com/2013/04/whatever-happened-to-r-core-transformers.html

I don't keep up with the insides of lots of gear. I do know that Cavalli Audio headphone amps use R-core transformers.
Here's the page for the Liquid Glass headphone amp and there's an internal shot that shows the transformer. I'm pretty sure their other amps like the Liquid Fire and Liquid Lightning also use R-core transformers.

 

Micromega CD players...

http://www.micromega-hifi.com/index.php/en/products/cd-players/cd-10

http://www.micromega-hifi.com/index.php/en/products/cd-players/cd-20

 

Parasound uses R core transformers in several of its preamps. Most commercial manufacturers don't keep up with the latest developments.

 

My Sony 5400 has two R-core traffos.

http://store.sony.com/p/SCD-XA5400ES/en/p/SCDXA5400ES

 

IYPO are there disadvantages of them vis-a-vis EI cored or toroid parts? I know the big toroid trend has been sort of sidelined over saturation via DC offset, although at my house I've never seen over 50 mV of DC offset I have heard of three to five volts in places.

They do appear a lot smaller and in a potentially better form factor than EI lam transformers.

 

Yep, this is a problem for me! However, I have a potential cheap solution that I'm going to test out tomorrow.

 

Hello John, welcome to the Forum. I did not know you were a member here as this is the first post of yours I've read. Did Robin L invite you?

We shared a few CES together when the late Bob Crump was around (I have not forgotten him, and I miss the big fella to this day). I hope you are well and keeping busy. It's a real pleasure to see you (in a virtual way).

I hope you'll find the time to post occasionally - your expertise and general sense of fun should fit in well here. Don't let the tube fanatics here get to you.

 

Wow, a dually in a sacd player! Reminds me of those old skhool twin powered Harmon Kardon receivers.

 

Nope. He told me about joining up yesterday, but I didn't find out about his post in the DIY Forum 'til he called me about it. Glad he's here though.

 

So am I - and thanks for responding.

 

Welcome Mr. Curl!
He's a fan of tube gear as well, being a fellow Marantz Model 10 tuner owner.

 

I know - we've had the discussion in person a few times.

That's a lovely unit. Did you read the article in Vacuum Tube Valley on Marantz and the 10B?

 

I would not expect too-too much participation from Mr Curl on this forum; He is kept very busy at DIYaudio.com

 

Ok, that's probably the right forum for young John.

 

Welcome to the forum John love your work.

 

Thank you!
It's serial number 35 out of a total of 100 made. Works like a charm. I am trying to find out what serial number Mr. Curl has. That would be cool since I keep a database of surviving Model 10's.
As for the VTV article, yes I read it. Fascinating stuff. Written by Mike Zuccaro which lives right here in San Diego.
The same issue has a tuner shoot out in which the Marantz came out on top.

 

Fantastic article - I was rapt when reading it. Times have changed.

 

220 V, 750 VA R-core power.

CAV A12 Hybrid Amplifier.

Cheers from Greece!

 

TECHNICS SU-A808 Stereo integrated amplifier (the same for SU-A707)

 

McIntosh MA-6300

 

SOULNOTE SA-730 (DIGITAL)

 

A year and a few months later, I see this after it was revived by a member from Greece with a big R-Core tranny in his amp. I think the main reason for not seeing these much is cost. The toroid can replace it in most situations. I do see R-Core transformers in Chinese made gear. They seem to be able to better absorb the costs due to their ridiculously low labor costs and also make use of the smaller chassis to bring the overall cost of product design back to where it might be otherwise. Cambridge Audio and Jolida both use some in a few of their lower profile units.
Another low profile transformer which is not a true R-Core also exists and is called a Flat Pack transformer. The Flat Pack uses a UI core and has the same low profile but cuts costs on the core material as well as labor. I have a Flat Pack in an old Soundcraftsmen amplifier that I have. That allowed for a fairly heavy transformer to be used in a very low profile chassis.
-Bill

 

IIRC the original reason for the R-Core was that they were less expensive than toroids to wind. A toroid has to be wound using a two step process, low frequency (<20-50 kHz) ones being wound on a Gorman machine. First, a round hula hoop wire magazine is put through the center of the core, then it is rotated, through the core, while wire is spooled onto it and then the wire is cut and attached, then the magazine and core are both rotated so as to wind the wire onto the core. It can be done by hand with a sewing hoop or, on big ones, a slit Hula Hoop, but it's incredibly awkward except for RF units needing only five to ten turns. The R core is itself priced similarly to a tape toroid core, but the wire is wound on split spools very much like sewing machine spools that have gear teeth and themselves spin on the core.

Notice all the sewing terminology here? Probably why transformer winding is a distaff activity.

http://www.gormanmachine.com/productor2.htm check out the videos. These machines have substantially smaller magazines than the ones I worked around decades ago, incidentally.

At any rate, I'd think that R-Cores would share the bane of toroids, the nearly perfect magnetic circuit that makes even the slightest DC offset saturate the coil, unless the core is slit, and slitting the core means using a lot bigger core. However, I do see ads for R-Core single ended output transformers, so there is a workaround somehow.