Oh, almost forgot, maybe the expert @
Strange Module: "Telefunken" Neumann preamp
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rock soderstrom
Tour de France
That would be rather unusual. I would not make it dependent on two retrofitted capacitors. The position in the circuit of the caps also plays a role. The two ERO tantals seem to be coupling capacitors for the input to block potential DC. Best, as said before, trace the circuit and you really know what's going on.
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rock soderstrom
Tour de France
Yes, Volker knows best
OK, got it. According to the datasheet, the OA10 op amp is typically driven by 24V, so maybe my initial guess was right. The RK204 input transformer has a voltage ratio of 1:2, so I can easily rewire it as a mic amp.
It works otherwise, but the [ prevents it from parsing the username, looks like.
In 1930 the transistor had not yet been invented.....
So this preamp can only produces after World War 2 and the invention of the bipolar transistor around 1947.
On the photo of the conductor side you can see that 2 transformers have been unsoldered.
Best regards
Well, maybe I should DM him
agreed, 1 to 4 distro card, only (1 to 2 currently possible from the photo) telefunken has a model that does the same thing, this is the neumann version, they come up cheap enough its tempting to try and test them out. but havent yet.
MidnightArrakis
Well-known member
[looks more like something from the 60s, rather than the 30s] -- Or.....more likely the 70's, as I can't imagine even the Germans were using PCB's with TO-92 transistors as far back as the 1930's, despite their advanced engineering technologies back then!!!
/
Looks like a standard Danner cassette distribution amp. I would guess 1970's maybe later. It has one of the common discrete amps of the era from over there.
They are similar to Telefunken V682 type modules (the Neumann equivalent number would be V482). similar era as well. Usually really nice transformers in them. Probably why a couple are missing.
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rock soderstrom
Tour de France
Not really, as said before, trace the circuit, that is not complex. One input circuit and four equal discrete drivers for the output transformers. Quickly done, you will learn a lot.
Then tinker a 24V PSU and you are in business.
as far as not fully loaded I have certainly seen it - but I have not seen that in the Austrian, Swiss, German stuff we work on here. I think if you asked a German engineer in those days to build you a board then only put half the stuff on it, you would get the cock-eared dog look, and then a long lecture as to why not to do it that way. He would then painstakingly build you a new kick-butt board for just half the stuff, and give it a corresponding part number. Say V482/4 for your 4 outputs or a /6 board for 6 etc. In your case... Vx82/4-2
They are more likely to fully load it and not use it. Later stuff - by the time LAWO era that may have happened.
Switching is often external on these if needed. Being a distribution amp - it likely had a fixed resistor gain setting so nobody could fiddle with if after setting it.
They are more likely to fully load it and not use it. Later stuff - by the time LAWO era that may have happened.
Switching is often external on these if needed. Being a distribution amp - it likely had a fixed resistor gain setting so nobody could fiddle with if after setting it.
and yes it will be positive 24V in that era.
your phantom power for your mic pre modules came from a separate same sized module - also powered by 24 volts.
I guess I need to lay off the giant Chai Tea's after midnight. Captain ramble here...
I don't think converting it to a mic pre is worthwhile. You would be better off scavenging the two output transformers and starting fresh pair of pres. That is what the last owner did, he was not building a line level device, or he would have pulled the input tranny too, lol.
Use that input transformer for some discrete line level transistor technology, a compressor or eq. -
The modules can work fine as makeup gain for other project modules just one in one out. It likely has about 10 to 20dB of gain available as it sits.
Use that input transformer for some discrete line level transistor technology, a compressor or eq. -
The modules can work fine as makeup gain for other project modules just one in one out. It likely has about 10 to 20dB of gain available as it sits.
I'm not sure the input stage has a good enough noise performance for that.
Typically, a line input stage has an EIN (Equivalent Input Noise) about 20-30dB worse than a mic preamp.
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