And there you have it, the only solar powered current mode headamp currently in captivity (well bar the other one in your lab).
You think I can sell it to a Golden Ear for $2413 plus shipping plus 4% PayPal fee
? I can make up a nice story about the internal light who filters noise and makes the sound smooth and enlightening.
It's likely the $$$ suppliers buy from Jensen/Sowter/Lundahl, stick it in a $10 box and add a $1000 label
But making these transformers is still a hand-carved-from solid-Unobtainium-by-Virgins process ... even at Lundahl who had the most modern plant. Their multi-section designs are very labour intensive.Can't really say which Lundahl or Sowter is suitable for MC as my scribblings show matching is key. In 1980, we considered both of equal competence. Lundahls were always slightly smaller for the same performance. Cynics might say this is cos Old Man Sowter insisted on their deep-drawn mu-metal shielding cans which he invented.
Size was the main reason Calrec were moving to Lundahl after our long association with Sowter. The microphones stayed with Sowter much longer cos they didn't come with cans.If you twisted my arm, I would say Sowter cos their matching chart for different cartridges. But even then, you need to read between the lines to find what source they were originally designed for.
For the Lundahls, look for a specified frequency response at a given source resistance. This should tell you what it was designed for. Alas, many of their new transformer datasheets don't show this. It is likely their zillion transformers with the 'same' spec. are slightly different versions for OEM customers ... See above.
In da rebel colonies, Jensen has an equivalent reputation .. certainly for mike preamp stuff. These three firms still have people fully versed in the arcane art of transformer design. I know the transformer man in Cinemag or Edcor passed away this Millenium.
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Incidentally, the main reason for the demand for 30dB OL margin in MM RIAA amps was Ortofon SL15E. This came with the STM-72 transformer with 40dB step up.
This wasn't a very good transformer even by the standards of the day but it meant the combination was 10dB+ louder than V15, ADC 10E, Empire & other top of the line cartridges of the day
They sold a much better & $$$ transformer (for MC20 & 30) around the genesis of Duraglit. But this was still beaten by their cheap MCA10 battery head amp ... all of which were trounced by the prototype Duraglits.
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Soft Magnetic Materials for Audio Transformers: History, Production, and Applications
This is a fascinating article with much of practical use today. IIRC, Old Man Sowter talks about 'glass metal' cores which might the special 'ferrites' that Marik uses in his transformers & ribbons.
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It looks like transformers haven't been standing still since 1980 and some now approach the performance of the original Duraglits but at mucho $$$.
But this thread now allows mere mortal DIYers to take Duraglit well beyond their reach ... for pocket change $
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Who were these folk? Was it a commercial mike? I'd be really interested in details.
BBC 4038 is still IMHO & ken, the passive Fig-8 mike with the most extended LF response in da known universe. It is the only passive Fig-8 that shows a rise in response below 50Hz measured at 1m. Its true free-field LF is -3dB @ 45Hz
Only TetraMic and the Calrec Soundfields have more extended Fig-8 response and only cos I cheat
The earliest I've seen this was in the Wireless World 1947 Williamson Amp articles. You could probably find more examples in RDH and even older Wireless World.
This Millenium, Eric & I saw this when looking at small transformers for a commercial mike project.
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If it's hand carved from solid BS .. I mean Unobtainium, by Virgins, its worth at least another $1000 to da Golden PinnaeYou think I can sell it to a Golden Ear for $2413 plus shipping plus 4% PayPal fee
Hmm ... Not much info on the Cinemag site but the Intact Audio guy says
"Many transformers (particularly the vintage ones) are speced with impedance numbers like 150:50K which simply translates to a 1:18 step up ratio"
150:50K was a standard transformer spec for valve mike preamps and 150R mikes. If he is using one for MC cartridges, he's pontificating from the wrong orifice.
Using a 150R design for 3R doesn't have LF problems but you'll have mucho noise.
I would stick to Lundahl/Jensen/Sowter.
S&B did this for supa deaf Golden Pinnae ThoerstenBill Shurv said:
Their virgins got fed up of being accused of hand-carving stuff from solid BS
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I installed the thing in my system, feeding my latest HPS 6.2 on low gain (~60dB), total gain is about 76dB for my Benz Micro Gold 12ohm 0.4mV @5cm/s.
Did a quick comparison with HPS 6.2 on high gain (~72dB gain) and, as usual, can't hear a damn of a difference, so I guess it's settled: reading a MC in a virtual ground (this one has about 5ohm) is as good as any other method.
Therefore, to hell with the "recommended" load of 100ohm it's yet another BS perpetrated by the audio industry. I'd bet the MC manufacturers didn't even bother to figure out what's happening in high/low impedances, they just copied the 100ohm spec, to stay aligned with the fashion and most of the available MC preamps.
Someone mentioned a few posts bs k that an MC cart puts out about 100 uA. I don’t think there’s a problem.
I tend to fully agree. The only thing that can be said for sure is that, if you go significantly lower than 100R with a voltage input amp (and 99% of commercial MC amps are voltage input), signal level will get attenuated and thus reduces output level and worsens SN. For cartridges with Rs > 30R the 100R already have an audible effect while for an Rs of 3R, one can go lower before this attenuation gets significant. As the majority of cartridges today are in the 5 to 15R range, the 100R recommendation or the rule of thumb to use 10*Rs fits the bill for most cases.
And if output level is not adjusted when listening and comparing different input resistor values, the louder setting will in most cases be preferred. And the majority of people do not realize that when playing with the DIP switches on their MC preamp, they change output level.
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Valid information.
Now when putting two amps in the box, you could make a diff in version.
You mentioned some postings ago not to be a fan for this topology, but that’s just a prejudice. Only by trying you know for sure wether it does or doesn’t makes sense sound wise.
Hans
100 µA signal current are still 1.6x10**10 electrons per 25 µs (time of pos. or neg. part of a 20 kHz signal). And even if it is only 1µA, one electron more or less at 1.6x10**8 signal electrons ist still -160dB of quantization noise.
If looking on reports and reviews on the internet and in the HiFi press, sometimes this is mentioned, sometimes it's said that running at high input impedances is even better than with 100R to 500R.
The 'experts' then try to explain this with missing 'damping'
Same people explain the sound differences for a too low impedance with 'overdamping' which in my view is nonsense. If this would be true, current input would always 'overdamp' as max. current is flowing and a max. force, counteracting the generator movements, is created. And all reviews for current input amps as well as Syn08's experience say exactly the opposite - there is no difference to a voltage input. As voltages and current are highest at high frequencies (highest velocities) some change in the frequency plots should be visible.For a high input resistance the only fact is, that almost no current is flowing anymore and one is approaxhing open circuit mode of operation. The change in signal level becomes insignificant so if there is any truth in it, there must be something different.
The 'experts' then try to explain this with missing 'damping'
We've covered this before the mechanical losses are orders of magnitude too large for any cartridge to act like a reciprocal motor.