My recommendation, source a signal transformer with an Amplimo TM888 stamp and do it for half the Thomas Hartwig price.
(or a hit and run Elektroakustik Kiel original from the late '60s)
So you're saying the cartridge has true headroom to be able to produce peaks that translate to those level voltages with normal preamp gain, this is something that can be seen on a CRO? Even after the equalisation ...
Red ring means it's a 160V part, 4640pF implies it has 0.6mm Ø leads.
Actually, the low budget of the Siemens KS series, polystyrene & aluminum foil.
Siemens boxed type B31531 is polystyrene & tin foil, 63V parts, lead diameter 0.6-0.8mm.
Both are good for 200.000hrs minimum, but the boxed ones have ~50% better numbers (tan δ, TK, dropout number, etc.), at 4 times the cost for the value in the picture.
(under 220pF, 10 times as much, >$5/pc in the early '90s)
So it's all relative.
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That's in the ballpark. I think in bed unable to sleep this AM, I figured about 800 BF862, assuming you could use 150mW of the phantom power, say at 3V, for the FETs. This would be to achieve around the thermal noise of a one ohm ribbon at 300 K. The Brownian and thermomechanical noises are likely higher, let alone normal studio ambients, and iirc Scott mentioned that a considerably noisier preamp still worked quite acceptably in real-world direct ribbon use.
But it's still an interesting stunt, a cunning stunt as the risque joke goes. Note that this approach only works for FETs and does not work for bipolars, which would otherwise probably be the devices of choice (some of the 2 ohm rbb' ones run at healthy currents) where the mic could have a separate power supply.
Oddly, many years ago I did some experiments, on 2SK170 equivalents and a couple of the big Crystalonics parts, in response to a challenge from Pease, who'd been busy in print emphatically disbelieving one of his favorite whipping boys, Keats Pullen. However I did not measure noise at the time, just followed the transconductance versus drain current down to very low levels (nanoamps). As the data vindicated Pullen, Bob was evidently disgustipated worse than Popeye and almost completely ignored the work, mentioning it briefly in a paragraph of a "cleanup detail" column and getting most of the details wrong. But we shall say nothing more ill of the dead.
However, it is possible that the noise performance deteriorates faster going to low currents than first-order theory predicts. A couple of people I recall said they were seeing some evidence of this, albeit not perhaps conclusive.
Bravo
I was lucky to get some Siemens transformers made by them.
I also really appreciate their speaker drivers from 60’s.
They are still strong in innovating.
AudioStereo -- ELAC -- History (EN)
George
A beautiful piece of hardware, almost a shame to put an opaque cover on it. With components like that, I'd build shelving tipped forward 20 or 30 degrees to show off the guts..a geek thing of course..😀
The grounding scheme however, is terrible. Any time varying magnetic field trapped between any left channel IC and any right channel IC will push loop currents through the green ground wires. This couples to the signal wires.
Coax shield does not shield magnetic. This design forces the customer to tightly bundle ALL input cables together. Otherwise, there may be hum/noise issues.
jn
whats the fascination with phono mistracking - why should electronics have to faithfully follow what was never recorded, cut by the lathe
fast limiting, clean recovery yes - but a power bandwith of ~5 kHz is all that can be tracked
fast limiting, clean recovery yes - but a power bandwith of ~5 kHz is all that can be tracked
It's crying out for a PCB across the connector array with all the switching/transformers mounted on it. Much better control of everything but no magical wire to make the sound better than it actually is. And an empty machined aluminium box (it is now but the wire makes it look less empty).
Also the first commercial echo sounder for fishing vessels (Fischlupe)
The echo-sounder was also a German invention, 1918.
(Elac/Electroacustic started out as Signalgesellschaft, a company that developed sound apparatuses for submarines)
Attachments
The well-regarded Royer R-122 still uses a matching transformer, but they may not need the whole 1:50 stepup. Pretty certain they didn't include DC-to-DC conversion either, but still a solid and practical commercial compromise. (That's *not* a bad word.)
I once calculated the number of 12AX7 triodes it would take for 3dB noise figure from a nominally 3 Ohm Coles. IIRC it was 853, but can't remember if that was triodes or whole (two triodes each) 12AX7's. And ignored excess noise. And ignored the wire resistance from the ribbon to the electronics. Yikes!
Thanks, as always,
Chris
I traced 32 patents (*) of them on this topic, which were known in UK during 1920-1921.
George
>Edit: (*) patent applications
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Is everybody finished with the first layer of criticisms of the passive line amp? If so, we might go forward.
i'm not completely comfortable with the colour of the sleeving and would prefer clear zip-ties 😛 the vast empty space could be smaller also
One more. Get rid of all the wires, squash everything down to the tightest, most compact configuration. Of course, then there is no excuse for the bling enclosure, sized appropriately ... 😉
Smarty pants
Critics should send their suggestions to Herr Hartwig:
Passive Vorstufe mit High-End Leitplastikpoti
Would love to read his answer
Critics should send their suggestions to Herr Hartwig:
Passive Vorstufe mit High-End Leitplastikpoti
Would love to read his answer
well OK i'm not surprised at the freyed blue sleeving now, the website is loud and covered in that blue. I particularly love this one
love the heatsinks...
I guess the cases are designed to make them look more substantial, or match other components, but its still pretty funny, I wonder if they are extra
An externally hosted image should be here but it was not working when we last tested it.
love the heatsinks...
I guess the cases are designed to make them look more substantial, or match other components, but its still pretty funny, I wonder if they are extra
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