That's where the 2 x 1N4148 I never seem to remember to fit could have saved the day.
I once fitted a gate of diodes as a primitive anti-theft device to my car via a relay. The relay once activated kept itself latched until the ignition switched off. The car was damaged when someone tried to hot wire it. They never found how I did it and gave up 100 metres down the road.
I once fitted a gate of diodes as a primitive anti-theft device to my car via a relay. The relay once activated kept itself latched until the ignition switched off. The car was damaged when someone tried to hot wire it. They never found how I did it and gave up 100 metres down the road.
I'll have to make a note of all the commercial preamps where I need to hookup the DC supplies.
I'll have to make a note of all the commercial preamps where I need to hookup the DC supplies.
We are making demons out of capacitors.
Caps block DC. Select them correctly and they offer almost zero impedance at the f of interest and show 0 (zero) distortion according to the AP.
There's actually a big disadvantage of the input cap(s).
It's physical size .. especially for MC means the input loop is a LOT bigger with the potential to pick up hum, buzz & RFI.
But Doug is going to show us how to get all this yucky stuff unmeasurable with simple unbalanced topologies .... and with his beloved input caps too.
Cmon!
Are you telling me all MM stages that use input coupling caps suffer from hum etc? You know as well as anybody its in the implementation.
The input loop size is critical in ANY LN application. Yes it is about implementation ... but huge extra Golden Pinnae bits in the loop certainly don't help.
You can tell immediately if a designer understands LN by how he lays out the input loop on a PCB.
I pontificate at length on this in LNprimer from my Yahoo MicBuilders Files.
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Could you post the schematic please. I'm seriously interestedWell I could really take offence at this as the c**p preamp was one of my designs.
You might want to try my little circuit from my Yahoo MicBuilders Files.
It has the lowest noise of any such device in da known universe.
It uses a huge total of 2 devices, so you might rustle it up with parts from your spares bin ... then spend the next 30 yrs trying to do something better.
PS It won't kill your cartridge if you reverse the battery.
Well then you can't reverse the supplies. We could let this lie, I've worked with Walt Jung who has extensively published on RIAA pre-amps and he never in the decades I have known him used a coupling cap for any reason other than a very large Ib for a very few bi-polar op-amps. BTW I have a 0-60dB mic pre-amp with horrible microphonics from the coupling caps (commercial).
virtual earth preamps
Doug, here's another suggestion for your book that will result in better sound as opposed to more Golden Pinnae gobbledegook.
Bill Shurv has a thread on mechanical resonance of cartridges
LD and some others are promoting the use of virtual earth preamps for MM. This is one of the classic topologies to extract every microBell of S/N (Normal non-inverting amps don't do this)
Of course the '75us' pole is done via the Inductance & Resistance of the cartridge so will be wrong. A simple (??!) shelf (which is ideally built into the RIAA network) will correct this.
Has to be matched to individual cartridges but as anyone building a vinyl preamp today will be a Golden Pinnae, this is just something else for them to tweak
You just have to provide the mathematical tools for them to do this
And you need to provide some way to replace the peaked 2nd order HF filter provided by the usual 47k + extra C & the L bla bla
I haven't looked in detail at the requirements for the OPA but it's likely the usual 5534 might still be good.
It's likely to get even better noise performance than your Virtual Reality Input Z with less bits .. the trade off being the need to match to cartridges.
Here's one example with is even sorta balanced input.
http://www.diyaudio.com/forums/analogue-source/303389-mechanical-resonance-mms-21.html#post5012334
You'll have to search that thread to find the others.
Doug, here's another suggestion for your book that will result in better sound as opposed to more Golden Pinnae gobbledegook.
Bill Shurv has a thread on mechanical resonance of cartridges
LD and some others are promoting the use of virtual earth preamps for MM. This is one of the classic topologies to extract every microBell of S/N (Normal non-inverting amps don't do this
)Of course the '75us' pole is done via the Inductance & Resistance of the cartridge so will be wrong. A simple (??!) shelf (which is ideally built into the RIAA network) will correct this.
Has to be matched to individual cartridges but as anyone building a vinyl preamp today will be a Golden Pinnae, this is just something else for them to tweak
You just have to provide the mathematical tools for them to do this
And you need to provide some way to replace the peaked 2nd order HF filter provided by the usual 47k + extra C & the L bla bla
I haven't looked in detail at the requirements for the OPA but it's likely the usual 5534 might still be good.
It's likely to get even better noise performance than your Virtual Reality Input Z with less bits .. the trade off being the need to match to cartridges.
Here's one example with is even sorta balanced input.
http://www.diyaudio.com/forums/analogue-source/303389-mechanical-resonance-mms-21.html#post5012334
You'll have to search that thread to find the others.
Exactly.
Many op amps work well at low voltages. Whilst it's not a great solution it would limit the current that could pass if stage one was at lower voltage. It also allows a bit of extra filtering if in cascade. If we want lets say 350 mV out and stage two is gain of 16 @ 1 kHz and I use 1 mV sensetivity that suggests a gain of 350. That says a gain of 22 for stage one. 22 x 1.6 mV ( DL110 ) = 35.2 mV rms. If we say + 30 dB we are looking at about 1.25 Vrms maximum output ( perhaps higher would be nice ). It looks to me this is worth considering. 350 mV is a healthy output. Stage two would need a gain of circa 160 at 20 Hz if the simple RIAA curve ( not IEC ). The gain of stage two can be higher and stage one lower without problems.
If one takes a MM apart the wire looks to be thicker than a 250 mA ( F ) fuse wire ( The last one I did was an AT93 ). I feel it should take 10 mA without problems either for the coil or the magnetic circuit. If the power supply was limited to just above the op amp needs it would be safe? This would be a good idea even if using an input cap I suspect.
BTW. Some demagnetise their pick ups. I never looked at this myself so can only pass on th idea.
@ Pandit Litoral @ Cooktown Recording and Ambisonic Productions
OOOH, dat "sounds" good ! Be nice if you could provide a link to your Yahoo MicBuilders Files I guess you don't have a link to CRAP though
OOOH, dat "sounds" good ! Be nice if you could provide a link to your Yahoo MicBuilders Files
I guess you don't have a link to CRAP though OP270
Looking forward to your tests Try to get the better grade, for eg OP270E. Which are guaranteed the noise spec
To All
Confusingly, there are other different devices with the Exact same code ? This shouldn't be allowed
Looking forward to your tests
Try to get the better grade, for eg OP270E. Which are guaranteed the noise spec To All
Confusingly, there are other different devices with the Exact same code ? This shouldn't be allowed
@ Pandit Litoral @ Cooktown Recording and Ambisonic Productions
Richard, I didn't know you worked with Eric. I have two of the very few Zucharelli Holophonic recordings, they are scary good through headphones. Never played with ambisonics.
Fusing current on #44 wire is .9A, 9V on 15 Ohms doesn't do it. Even if carts use a higher gauge 15mA will never get even close. At the moment I can't find data that I used to have up to #50 wire.
I did find the capacity of the smallest normal copper bond wire (.6mil) as 255mA.
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