Phase Linear Bridging Information (Using Triad G-336 Transformer)

[oldphaser]

I have gathered up some historical information concerning the Triad G-336 transformer.

There were several Phase Linear service bulletins issued (one has been previously posted on this forum) as well as a couple Triad documents.

Also included is a photo of a G-336 transformer I acquired a number of years ago after searching for several decades. It didn't come cheap.
Someday, I hope to install it into an amplifier and do some testing and then pass the transformer along to someone else.

(Please see attached files.)

Of course, these days there are many options out there for bridging audio power amplifiers.


Ed

 

[mlucitt]

I wish these Triad transformers (autoformers) were available today. This is the best substitute in my opinion:
https://lightningboyaudio.com/store/p70/UJ20_line_input_transformer.html#/accounts

The LBA-UJ 20 is the first official transformer design released by LBA. It's name draws from the guidance given to me by a transformer guru, my late Uncle Joe Marino and from its impedance ratio of 10k:20k. It was designed to be used as a high performance line-input transformer. It converts balanced 600 Ohm line-level signals to a high impedance unbalanced 20k Ohms for input stages. The UJ20 is housed in a MuMetal shielding can for superb rejection of external electro-magnetic, electro-static, and RF noise, PC pins come standard. The transformer core contains a high concentration of nickel, which facilitates a very wide bandwidth with low distortion. Its a step up transformer intended for converting 600 Ohm balanced line level (+4dBu) to unbalanced Hi-Z for tube input stages. Designed and crafted in a secret laboratory in North Collins, NY USA.

$78.00

 

[TimD]

The best substitute is an electronic inverrter. There is *ZERO* need for expensive transformers for this application.

 

[laatsch55]

I wish these Triad transformers (autoformers) were available today. This is the best substitute in my opinion:
https://lightningboyaudio.com/store/p70/UJ20_line_input_transformer.html#/accounts

The LBA-UJ 20 is the first official transformer design released by LBA. It's name draws from the guidance given to me by a transformer guru, my late Uncle Joe Marino and from its impedance ratio of 10k:20k. It was designed to be used as a high performance line-input transformer. It converts balanced 600 Ohm line-level signals to a high impedance unbalanced 20k Ohms for input stages. The UJ20 is housed in a MuMetal shielding can for superb rejection of external electro-magnetic, electro-static, and RF noise, PC pins come standard. The transformer core contains a high concentration of nickel, which facilitates a very wide bandwidth with low distortion. Its a step up transformer intended for converting 600 Ohm balanced line level (+4dBu) to unbalanced Hi-Z for tube input stages. Designed and crafted in a secret laboratory in North Collins, NY USA.

$78.00

Mark, there is a very expensive Jensen line level transformer on EVERY INPUT AND OUTPUT ON the Rowland. When folks were having hum and buzz issues when we were all going the tri-amp route, I wasn't, dead quiet from the outset, and I'm not THAT GOOD an XLR cable maker...

 

[mlucitt]

I was only commenting on the response from Old Phaser. My post has nothing to do with any piece of equipment including the Rowland.
This was related to the Phase Linear Service Bulletin referencing the Triad G-336 Autoformer which is no longer available or in production.
I believe it was the easiest, least expensive way to bridge a Phase Linear amplifier.

Please refer to the title of the original post.

Tim, which electronic inverter are you talking about?

 

[TimD]

The one you could trivially build, and swipe the design from just about any bridgeable amplifier. Basically, and op amp inverting unity gain stage feeding input 1 to input 2. Typically, a single op amp and two resistors or so, similar to this https://sound-au.com/project14.htm (although you could likely do it without the pos/buffer side). Since these typically want +/- 15v, which is already present in the amp, the best way to do this would be a small PCB inside the amp, with a small switch to set channel 2 to take either the direct chan 2 input or inverted chan 1.

(Someone had also posted a 3 transistor design option, the Phase PL11 bridging adapter, in another thread . . . specifically, post 183 in the "700/B/Ser 2 Transformers" thread . . . https://forums.phxaudiotape.com/attachments/phase-linear-pl11-bridge-adaptor-assembly-pdf.27976/ )

I've seen bare boards offered for under $3 (although this could be done just as well on a generic project board), resistors (singles) are about a dime, and the op amp should be a few dollars . . . for the example above, then, the total cost would be about $5.50 plus maybe 30 to 60 minutes time. Build a power supply and enclosure, and it could go external, but more $$$ . . . Someone may sell a product to do this, but since most amps that get used in bridged configs already have basically this already, external bridging devices are likely not that common. Heck, even with a transformer, there would be work to either install it internal, or create an enclosure externally . . .

As projects go, install would be similar to the WA DC protect board, but the build far, far, easier.

 

[oldphaser]

Here is a little more history on the Triad Transformer Mfg. Company now Triad Magnetics.

"Talking With Triad Magnetics: Demystifying the Science Behind Audio Transformers" by Frank Doris in PS Audio Copper magazine March 25, 2025 Issue 216:
https://www.psaudio.com/blogs/coppe...b59_ZlRo24jIkgQ_BJZEaFITTIq9UTaV0qrhC5BCFPkwM

 

[laatsch55]

I was only commenting on the response from Old Phaser. My post has nothing to do with any piece of equipment including the Rowland.
This was related to the Phase Linear Service Bulletin referencing the Triad G-336 Autoformer which is no longer available or in production.
I believe it was the easiest, least expensive way to bridge a Phase Linear amplifier.

Please refer to the title of the original post.

Tim, which electronic inverter are you talking about?

I know that Mark..