I keep a Dynaco system in my office consisting of a PAS 3x, FM 3 and an ST 35, and includes a Sony 5-disk CD changer. As it happens the 35 is a first-issue device with the US-made output transformers, and multi-voltage power transformer. The system runs
for 9 hours per day, 5 days per week, driving an AR Athena speaker system. Until this morning, all tubes in all three Dynaco components were original Dynaco-marked products, being mostly Mullard and Telefunken.

Well, yesterday, the 35 popped one of the 7247/12DW7 drivers - a fade-to-black in the left channel that followed the driver when I swapped them during the diagnostic process.

After a bit of research, and after learning that this driver consisted of half-a-12AX and half-a-12AU7, and not having the time to search through my tube stash, where I am sure I have several, I decided to try a pair of clear-top RCA 12AU7s from the
couple of sleeves I snagged at Kutztown last Saturday ($4 each, NIB). I was warned from the research that the gain would be lower, but that there were no specific hazards in using this option.

I dropped them in this morning, they are singing sweetly as I type. And, yes, I need to increase the volume from the preamp some to get the same volume, but not excessively much. From about 9:00 to about 10:15. Still lots to go.

Note that this is the first failure-in-use of an audio tube I have had in 40 years and thousands of hours in the hobby. Failures at turn-on, sure. But not while under use. Interesting!

Peter Wieck
Melrose Park, PA

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Peter Weaky Total Wanker wrote:

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After a bit of research, and after learning that this driver consisted of half-a-12AX and half-a-12AU7, and not having the time to search through my tube stash, where I am sure I have several, I decided to try a pair of clear-top RCA 12AU7s from the

couple of sleeves I snagged at Kutztown last Saturday ($4 each, NIB). I was warned from the research that the gain would be lower, but that there were no specific hazards in using this option.

I dropped them in this morning, they are singing sweetly as I type. And, yes, I need to increase the volume from the preamp some to get the same volume, but not excessively much. From about 9:00 to about 10:15. Still lots to go.

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** FFS, the wanker has just thrown away the entire NF loop from his amp.

The "12AX7" half of the 12DW7 input tube is THE main forward gain stage - about 100 times - now it is less than 20.

So the NFB loop, being unable to function, has collapsed allowing the overall voltage gain the amp to drop as well. Add that to the wrong bias conditions and you have an amp working in "limp mode".

Good enough for old Weaky though.

Too lazy to even go through his own tube stash.


..... Phil


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Phil:

I sat on my fingers on this one for a while, but you are such a sad waste of air, food and space, and cannot resist making an utter fool of yourself. I am glad to help the process.

I will lay dollars to Krispy Kremes that you have never touched, seen or operated a Dynaco ST35 in your entire benighted little life. They are not common in the first place. And the odds of one making it to Australia are slim to none. Assuming that
unlikely eventuality, the odds of you getting with 100 meters of such a device are equally slim.

As to my tube stash - it consists of several thousand tubes in a closet stored by type. Exotics are 'in the back'. When I have nothing better to do, I will dig down and get to them. Otherwise, I chose to experiment with what is right to-hand. Not a half-
bad result, as it happens.

So, go on, keep festering in your own excrement - it seems to suit you.

Peter Wieck
Melrose Park, PA

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Hey. Phil. Take. A. Chill. Pill.

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On Friday, January 31, 2020 at 11:51:45 PM UTC-7, brownb...@gmail.com wrote:

Hey. Phil. Take. A. Chill. Pill.

The fuck would *you* know about anything?
Take a fucking hike, asshole.

LV

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