Telefunken G73R

First off, I would like to thank @Elk for creating a new category under tweaks for “tube talk” it will be nice to get all the tube discussions under one umbrella!

I have been searching for and have located a NOS pair of Telefunken G73R (12AU7) tubes
They are supposed to be a step up from the famed ECC802S. We shall see FedEx say’s Friday

Anyone ever try them?

Best,
-JP


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A little more detail

This is not a commercial valve but a product made to specification by Telefunken exclusively for two companies

Agilent Technology and Hewlett-Packard

it was used in avionics and in the electromedical sector.

It met a series of qualitative requirements as restrictive as never before had been required.

In addition to the absolute constancy of production, to the best materials available at the time and to the most qualified workers, the two companies required absolute not microphone sensitivity and RFI / EMI shielding characteristics.

In particular, they demanded impeccable constancy of operation with controlled emission over time and the least possible noise generated.

A special treatment of the glass was therefore developed by the German manufacturer consisting of a black compound containing damping and shielding materials, applied at the end of the production process which covers all the exposed part of the valve with the exception of the space inside the fixing terminals, therefore, the exclusive <> symbol that distinguishes all Telefunken production is visible

The production was carried out in batches of 12 identical pieces electrically together. We found two of these packs.

In fact, this exclusive production is superior as parameters to the ECC802S from which it derives.

It is practically impossible to find new specimens, those that have appeared on the market over the years bear the manually written initials and no longer have the original label applied on the glass. Normally they come from old dismantled aircraft so it is difficult to determine the real state of wear.

It is true that these are tubes that could work for 40,000 hours so even if you use the measurement parameters they will always be excellent

We have 12 perfect pairs at the moment, never used, placed on a base only for our test.

An expensive but unique opportunity to get the best ECC82 ever.

Best,
-JP

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That’s likely to outlast most components - at least ownership of one. They look and sound intriguing. I’m looking forward to your take once they’ve gotten a few days on them.

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At $500 each they’re a bit rich for my budget. I did just purchase a NOS pair of “screened for instrument use” Telefunken 12AU7s from Brent Jessee and these sound great in my BHK Preamp. A relative bargain at $400/pair. Also claim long lived, very low noise and other goodness. There’s still a little volume adjustment “click” on one channel that Brent indicated may improve after a couple hundred hours.

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Mine too and I’ll admit they are pricy, but if they last 40,000 hrs as reported and provide the magic some claim then it wont be the worst cash I’ve spent on my audio journey

I feared if I didn’t pull the trigger, I may not get another chance at actual NOS G73’s only other options for them are eBay “roulette” not to say there are not many, many reputable sellers there

I mentioned to Brent last month when I bought the Mazda’s that I was looking for a pair. His response: “yeah, me too”

The screened Tele’s - exceptionally nice tube!

Best,
-JP

I’m just beginning to burn in the Mazda 6189’s I recently got from Brent Jessie so I may not put the G73’s in for a while yet but I certainly will share my thoughts on them after I roll them in…

Best,
-JP

The Mazda’s burning in:

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Where are you planning to use these “fancy” signal tubes?

Preamp gain
Concert Fidelity CF-80LSX2

Best,
-JP

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I guess if you own a $24k+ preamp it’s easy to justify the extra snazzy tubes! Very pretty and I’ll bet sounds quite good.

Absolutely, yet some of us still can’t seem to grasp the concept of relativity.

It is indeed a wonderful preamp and one of those very few pieces I will never part with both because of its sonic qualities and because of the screaming deal I got when I purchased it (under 5K)

The re-sale value of CF components is ridiculously low. No advertising other than some audio shows, no dealer network, very small presence outside of Japan, small number of reviews

If there is another under 5K preamp out there that performs on the level of the CF-80, I would love to hear it :slightly_smiling_face:

That said, its not for everybody. Single ended only, very purist design, 2db volume steps, service needs to be addressed in Japan. The update to LSX4 which added balanced in/out is 6K and 6-8 wks abroad, remote control of volume only, very limited functionality overall, but man does it sound sweet!

All in, best preamp I’ve ever owned, just a killer piece…

Best,
-John

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Tubes arrived today
It appears Italian tube dealers don’t mess around with packaging their tubes for shipment. I have never received tubes in a miniature flight case before. The case was packed in a heavy corrugated box with closed cell foam packed around the flight case


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Wonderful packaging!

Came across this site while seeking tubes, apparently I am on a quest to obtain every NOS 12AU7 in existence, or so it seems sometimes :slightly_smiling_face:

Anyway, cool little tube site if you are so inclined
Tube Maze - Guides and reviews of vacuum tubes and tube equipment

Best,
-JP

Thanks for the link. I like what they have to say about my favorite 12A type tube, the Amperex 7062 with slanted D and pinched waist.

Cool site. Really useful to me.

There is some good discussion, always looking to increase my knowledge on the subject of tubes and tube testing

Upon reflection, I should have started a new topic in “Tube Talk” and not blended it into the G73R thread, not sure if this can be corrected @Elk ?

On a side note and keeping with the G73R thread, I did roll them in yesterday and will post some thoughts after I have them in for a while, if there is any interest?

They are a little more difficult to see with the black coating. The tubes are running in the photo

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I’m interested to hear your impressions when you are ready. I have some 6922 types with the black coating, GE “Smokies.” Interesting sound though I have moved from that tube type to using 6SN7 type with adaptor bases in my amps and most of my preamps. Still in that application my favorite are RCA “gray glass.”

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So, I have a little over 40hrs on the G73R’s and they seem to have settled into what they will be

Ultra smooth, clean and detailed with a weight and density to the sound. Detail is there in spades, there is a sweetness to them as if everything was coated in honey, not in an overly warm or soft way and not at the expense of air & space

The sound is quite unique among other 12AU7 variants used in my CF-80, words that jump out at me are smooth, holographic and dense. If a holographic, expansive soundstage is your thing (yes please) these tubes deliver. Bass is tight & controlled while not explosive, top end is just outstanding, mid-range has all the tube goodness you can ask for

They do seem to produce a db or two less gain than my other 12AU7’s not sure why, maybe the added weight or density makes it feel this way. I did not do any db measurements. Nothing a little tweak to the volume control didn’t fix

I realize I am biased and I want these tubes at the price paid to sound amazing. In the end, I’ll just say this: It will be difficult to return to other 12AU7’s without feeling that I’m not hearing my system at it’s best, although my Siemens 5814 triple mica are not a very far fall

Best,
-JP

John, thanks for the reply with impressions! Does indeed sound as if these are excellent tubes!

The one 12AU7 spot that I have in my systems is for my Decware ZROCK2 and I have tried MANY tubes in these components (I have 3) and they actually respond very well to a little more gain, and the best that I have found are Amperex pinched waist 7062, a 12AT7 type. These give me much the same characteristics as you describe, so I know that we both have some great tubes in use!

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