Wright Sound Company WPA 3.5 with "gold" output transformers

[Paul Joppa]

750 ohm cathode resistor is visible in the picture; therefor it's probably the classic RCA operating point, 60mA/250v/45v bias. George did like to do most things "by the book".

[Steph]

Thank you, Paul! You guys are great. I appreciate all the info.

[Steph]

You could ask Mike what some of that means. Not sure what 10x10 means. I would have guessed that is the number of lams in alternating layers in the stack if it looked pinstriped. NAG might mean Nickel Air Gapped.

Hi Dan,

FYI, from Mike:

"I can confirm that the NAG stands for "nickel air gapped"... the 10X10 would have indicated that the lams were stacked alternately(i.e., interleaved) in groups of ten... but your units are NOT stacked 10x10--- they are butt stacked with an air gap spacer--- hence you see the straight line all the way across the stack where the E's butt up against the I's.

best I can figure is that I may have initially planned on stacking the core 10X10.. and then changed my mind and went with a gapped butt stack...

Stacking 10x10 introduces an airgap into the core... but not as large a gap as a butt stack with an added spacer works out to bee.

Cores that are not intended to have an air gap are usually stacked 1x1--- one by one gives you the least amount of airgap and optimizes the effective perm of the core--- so-- say in a push pull output trans you might go with a one by one stack. One by one keeps the interruption of the magnetic circuit to a minimum.

As a side note--- and something I've thought a lot about and have wanted to write about is--- for all the cache of "c-cores" being hip and efficient--- they more closely resemble the butt stacked EI lams in the sense of they have "large" effective air gaps vis-a-vis what can be obtained with carefully stacked EI laminations.

Your pair of 204 NAG's are really numerically quite rare... we've maybe made three or four pairs of these (by memory) over all of the 22 or 23 years that I've been making transformers. "

[scatterbrain0001]

Hi Dan,

FYI, from Mike:

"I can confirm that the NAG stands for "nickel air gapped"... the 10X10 would have indicated that the lams were stacked alternately(i.e., interleaved) in groups of ten... but your units are NOT stacked 10x10--- they are butt stacked with an air gap spacer--- hence you see the straight line all the way across the stack where the E's butt up against the I's.

best I can figure is that I may have initially planned on stacking the core 10X10.. and then changed my mind and went with a gapped butt stack...

Stacking 10x10 introduces an airgap into the core... but not as large a gap as a butt stack with an added spacer works out to bee.

Cores that are not intended to have an air gap are usually stacked 1x1--- one by one gives you the least amount of airgap and optimizes the effective perm of the core--- so-- say in a push pull output trans you might go with a one by one stack. One by one keeps the interruption of the magnetic circuit to a minimum.

As a side note--- and something I've thought a lot about and have wanted to write about is--- for all the cache of "c-cores" being hip and efficient--- they more closely resemble the butt stacked EI lams in the sense of they have "large" effective air gaps vis-a-vis what can be obtained with carefully stacked EI laminations.

Your pair of 204 NAG's are really numerically quite rare... we've maybe made three or four pairs of these (by memory) over all of the 22 or 23 years that I've been making transformers. "

gold output transformers is that true I have only imagined them, where do I get them if I had the money?

[scatterbrain0001]

I recently acquired a second pair of the WPA 3.5 (to use in a tri-amped
setting) and am trying to figure out what the story with the second set
of amps might be.

Most of the ones I have seen have a serial number and the initials of the
assembler along with a date (month/year). For example, my first pair have
the following info:

Serial number: 417 L 417 R
Assembler / Date: SH 5/01

The second pair have the following markings:
Serial number: 042 R 042 L
Assembler / Date: SM ROHR

It would stand to reason that the second pair were number 42, whereas
the first were number 417. What stumps me is the possible meaning of
the "ROHR" (in place of a date).

I am also interested to know which output transformers were used. On
the second pair, they are a gold color, whereas on the first pair, they are
black. From what I have read, various OPTs were used by George over
the years: MagneQuest, Sowter, and O-Netics have all shown up in various
searches. I've seen DeYoung come up, as well.

I have asked the gentleman from whom I purchased the amps about this
andhis reply was "Over the years I have owned many of his amps, pre-amps
and phono pre-amps. The 3.5s that I sold to you were used by George as an
experiment to see what the gold transformers would be like versus
Magnequest. George preferred the gold transformers but they were too
costly--he would have had to charge more for his amps and he didn't want
to do that."

Any ideas on who might have made the "gold" transformers or to what the
"ROHR" designation might refer?

Any insights / leads would be appreciated!

who would I talk to about gold output transformers if I had the money?

[Paul Birkeland]

who would I talk to about gold output transformers if I had the money?

That's a tough one, as you'd have to talk a winder into making a gapped nickel core transformer, which is highly unlikely to happen, especially for 2A3 finals.

[Doc B.]

Not to deflate this too much, but the "gold transformer" probably has gold plated end bells. Those were used by Jack Eliano in years past, more or less in response to Mike's use of polished brass bell ends. Probably only George would have known what the cryptic serial numbers meant. Ironically before George started Wright Sound he would spend his idle time at his old job drawing up schematics of ideas he had and gave some of them to me for VALVE, but when he went into his own business he didn't seem to document much of anything he actually built and sold. A thorough search of his home after he passed away turned up zero documentation.