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Balanced input phono stages |
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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Actually my circuit above would "allow the full benefit of a BIPS to shine through" (and using MM or MC - adjusted to suit).
Dynavector patented I-V (current amplification) used for MC in the 70s/80s, but patents only last 20 years so the German manufacturer should be safe. I assume it's that being used here (doubled for balanced - one for each leg), because that doesn't work for all MC cartridges either. It also does part of the EQ, as it must, because of the loading it has on the cartridge due to it feeding a virtual earth, and that's why it doesn't work for all - it has to be "optimised" for a particular cartridge or the EQ is out - and Dynavector's invention obviously favoured Dynavector's cartridges once in production. However Norman could be talking about current-feedback op-amps which is a different kettle of fish. And yes, all transducers do seem to be balanced (I'm sure somebody will point me at one which isn't), or more correctly stated: floating. They can be used both ways, for example loudspeakers can be driven single ended or by bridging two amplifiers with one out of phase with the other. This could be called balanced (and is), but most would simply say bridged. Microphone capsules are floating but can be made to be either by the way they're wired; transformed; or preamplified. As for capacitor-phobia, I'm afraid I have to inform you and all readers that you can take out every physical capacitor from a circuit and still the signal will be subject to capacitance - which exists in all components. Yet another piece of marketing folklore which people claiming to be engineers have adopted (a bit like "pure class-A" and "zero negative feedback" - modern day paganism...) EQ simply doesn't work without capacitors and in the Dynavector patent a capacitor has to be in-line with the signal to replace the mid frequency RIAA knee. Passive EQ uses capacitors "across" the signal. How does this differ with them being in-line with the signal? Their effect can still be heard used "across" the signal! Some designers go to extremes to remove every capacitor they can. For example: DC output offset where an integrator (they call them "servos") is used to pull/push the output back to centre/zero - but an integrator uses a capacitor! Connecting an expensive cartridge directly (DC coupled) to an input comes at a price. Any DC offset, even a small amount, could gradually heat the fine wires - you know how fine they are? - and basically they are being used to bias the input DC level. Even if the coil windings survive they are effectively a solenoid with the armature being pushed "off-centre" by whichever way the DC input bias is flowing. If a speaker drive unit was pushed in or out to remain that way when the amp was switched on there'd be an outcry! But you can't see what's going on inside a £200 - £5,000 cartridge... Edited by Graham Slee - 07 Sep 2018 at 4:16am |
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That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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roger staton
New Member Joined: 03 Sep 2018 Status: Offline Points: 10 |
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Hello,
I would like to try the Accession MM phono stage please if that could be arranged. regards Roger Staton
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Fatmangolf
Moderator Group Joined: 23 Dec 2009 Location: Middlesbrough Status: Offline Points: 8960 |
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No problem Roger. Please PM me (drop menu under my userid on the left) and we'll sort out the details.
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Jon
Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC. |
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