It won't do that with a cartridge connected.
This is the standard op-amp circuit.
Ed
Not with input shorted either, unless the reference signal level is much greater or the noise bandwidth much smaller than usual (like 1 FFT bin instead of the whole audio band, with or without weighting).
Frequency response means nothing unless the tolerance is stated, and is ensured by precision components
and good design.
and good design.
I would believe that S/N with a shorted input and battery power supply. 50 dB (assuming at 1kHz) is a healthy gain for a MM phono pre. There is no way you'd ever get a 105 dB S/N unless the power supply was dead quite and the inputs were shorted.
It's one of the many phono preamps on ebay.. how the hell do you sell stuff with such claims.. Like many Chinese kits or complete phono preamps on eBay, some look very nice inside. But do they work? Do they make a sound or just a hum? Meh...
Assuming that 105 dB means 105 dB RIAA- and A-weighted with respect to an input signal of 5 mV RMS, 1 kHz, which is the usual nominal level for MM phono amplifier signal-to-noise ratio measurements:
-105 dB with respect to 5 mV is 28.11706626 nV
Long ago, I calculated that the noise bandwidth of RIAA- and A-weighting is 3219 Hz with respect to the gain at 1 kHz.
28.11706626 nV/√(3219 Hz) ~= 495.5751442 pV/√Hz
The equivalent input noise voltage density of an NE5532 is 5 nV/√Hz, so about 20 dB higher.
There is no way you get more than about 85 dB RIAA- and A-weighted with an NE5532 even when the inputs are shorted, which renders the measurement useless anyway - unless they use an unusual reference signal level or measure the noise over a too narrow bandwidth.
Unfortunately, consumer audio advertising specs are full of lies. With the only intent, to fool the laymen potential customers.
@Io NoDiyAudio
I think you should get together with a few friends and build
OREAD
or wait for “Keine Ursache” to grow up and have a kit already.
HBt.
Psst
The decision is entirely up to you, but your Pro-Ject Audio PhonoBox is certainly not bad - upgrade, buy the S2 ultra or the weird FOSI thingy.
That's my suggestion for you.
I think you should get together with a few friends and build
OREAD
or wait for “Keine Ursache” to grow up and have a kit already.
HBt.
Psst
The decision is entirely up to you, but your Pro-Ject Audio PhonoBox is certainly not bad - upgrade, buy the S2 ultra or the weird FOSI thingy.
That's my suggestion for you.
I just lost a Rothwell Simplex MM!! More than Fosi.. friends for these things? But if I don't even have a shop to buy a soldering tip here.. what can I say.
The 1970s and 1980s are simply a thing of the past. Back then you could buy everything in those radio craft stores.
Today we can consult the online mail order business.
what is it
Schematic?
HBt.
@Io NoDiyAudio
there is a great kit called PEARL 3, maybe you're looking for a real challange and invest in the future ..!
there is a great kit called PEARL 3, maybe you're looking for a real challange and invest in the future ..!
I will give the benefit of the doubt that the circuit works. It probably sounds okay too. Most people won't notice the S/N isn't what was claimed.
I see the designer threw in an extra pole (R2 and C4). The EQ has the +1 error too.
Ed
I see the designer threw in an extra pole (R2 and C4). The EQ has the +1 error too.
Ed
Now I have this little mm/mc phono box project, what do you think could be improved a bit? I can start from here to do some practice, I only care about MM and that it does not exceed 100pf as my AT head requires. All the blue capacitors are 100 microfarad 25v
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I am guessing the components on the bottom are a charge pump. That is not good in a pre-amp.
You should leave the circuit alone unless you thoroughly understand its engineering.
Ed
You should leave the circuit alone unless you thoroughly understand its engineering.
Ed
The input op-amps appear to be these:
https://www.mouser.com/datasheet/2/294/NJM2068_E-1917171.pdf
in which case they seem quite suitable for MM (although I have some difficulty interpreting the datasheet, as I don't know whether JIS A is the same as ordinary A-weighting).
https://www.mouser.com/datasheet/2/294/NJM2068_E-1917171.pdf
in which case they seem quite suitable for MM (although I have some difficulty interpreting the datasheet, as I don't know whether JIS A is the same as ordinary A-weighting).