Bottlehead Forum
General Category => General Discussion => Topic started by: Steph on March 22, 2013, 09:59:19 AM
-
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!
-
Most of the gold color transformers I've come across were made either by Bertolucci of Lundahl, but this was supposedly a more champagne gold than real gold plating. The only real gold plating I've seen has been on some elektra print transformers that Sy Brenneman used in some of his higher end amps. Come to think of it, I believe the James transformers are also available in a champagne gold color, but those would not have been more expensive than the others you mention. If I were you, I'd go with Lundahl and start looking there.
No idea what the rohr is, sorry.
Hope this helps,
Jim
-
I'd guess they are Electra Prints. Gold plated end bells were an option for a while. You might check with Jack.
-
Thank you for the reply / replies. Not sure who this will be in reply to as I'm not familiar with this forum design! But I do appreciate the comments.
I put the word gold in quotes because I intended to emphasize the color. It's not just the end plates and it's unlikely that they are gold plated. The term champagne seems apropos here. I will try to post picture of innards and outtards tomorrow after a friend and I look into these and give them a listen later today.
-
OK, those don't sound like they are ElectraPrints. Not sure what else they might be. I know George tried Sowters for a while and they are on the higher side price wise (and sound very good) but I don't know if Brian makes anything with a gold finish. When it comes to George's amps, every one was a one off to some degree. And the only schematics I ever saw were a couple that George gave me many years ago. So it's a little hard to make a definitive guess about any of the parts!
-
Thanks for the replies so far. I'm still figuring out this site's software, so if you don't mind slumming it at the Asylum for a few moments please take a look at the link for some exterior pics.
http://www.audioasylum.com/forums/set/messages/7/72784.html
http://www.audioasylum.com/forums/set/messages/7/72784.html (http://www.audioasylum.com/forums/set/messages/7/72784.html)
I didn't bother with posting pics of the innards because I had three different pairs to look at and they (as Doc suggested) are all somewhat different in their layout. Also, it turns out the serial numbers appear to be meaningless, as they don't line up chronologically with the stated production dates!
The "RORH" designation in place of a date on the 042 units remains a mystery.
-
The end bells are brass, not gold and those look to be MagneQuest TFA -2004s. What's curious is they appear to have permalloy laminations, which should be used in a parallel feed circuit, which that amp does not appear to be. Perhaps the lams are M4 or M3, or perhaps George was just wingin' it on the design of that one.
-
Since the laminations are "gold" I expect that the transformer was painted. I posted this in Mikey's thread. These are my TFA-2004 transformers with polished/lacquered end bells:
http://www.bottlehead.com/smf/index.php/topic,2865.0.html
-
The lams in the photos are a nickel color, or perhaps the color of m3 lams. And Mike did quite a few transformers with raw, unpolished brass end bells, which those look like to me, as I have some myself.
-
I think in the middle picture the lams look more silver than gold. I didn't pay that much attention to it. In the other two the lams look more gold. But you are probably right. I don't remember that my end bells looked gold before polishing. That probably has something to do with how long the end bells have been around.
-
Thanks, guys! Not ignoring other responses ... just don't know how to navigate this forum, yet.
Does this work?
http://gallery.AudioAsylum.com/cgi/gi.mpl?u=6942&f=417_inside.JPG
-
I still think it's a permalloy or M3 TFA, but I wasn't paying attention to the stack before - it's a TFA-204 not a 2004. The lams are stacked and gapped for series feed and you can see that is how it is wired underneath. Probably permalloy lams, and George was probably assuming that the 3.5W 2A3 power output would be OK in series feed with the permalloy. Not sure about that, because I don't know how much DC current he was running through the core.
-
I still think it's a permalloy or M3 TFA, but I wasn't paying attention to the stack before - it's a TFA-204 not a 2004. The lams are stacked and gapped for series feed and you can see that is how it is wired underneath. Probably permalloy lams, and George was probably assuming that the 3.5W 2A3 power output would be OK in series feed with the permalloy. Not sure about that, because I don't know how much DC current he was running through the core.
We have a winner! Thanks to all for your efforts. Upon some dissection, we found the following handwritten marks on the core:
60 MADC
10x10 TFA
204 NAG
The core in the 042 unit (all black) was simply stamped "TFA".
Still wondering about the meaning of the RORH designation on those units.
-
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.
-
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.
Thanks for all the help, Dan! I'll touch bases with Mike.
-
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".
-
Thank you, Paul! You guys are great. I appreciate all the info.
-
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. "
-
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?
-
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?
-
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.
-
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.