The lean bass may be due to insufficient open-loop gain. I estimate the open-loop gain is in the low 70s dB, which would lead to a RIAA EQ error at low frequencies.
Ed
Ed
Too little OLG in the low bass range?
Definitely a clear NO at this point. As I always do my homework and know RIAA EQs inside out, I think that +100dB could be enough, don't you?
HBt.
As soon as Morten's circuit boards arrive, I'll get to work - and get to the bottom of everything. I will probably start by looking at the "RUBY" circuit. Because SUPRA itself works perfectly. How do I know that? Of course I have the current dimensioning in my back as a test circuit on a breadboard. I don't operate in a vacuum.
Note:
This board must be optimally shielded from all external and internal fields.
hbt.audio
Okay, my small-signal calculation matches the open-loop gains for the loadings you have used.
I had assumed the loading of core-outp would be closer to 30K.
Ed
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CLG without EQ
Rload ---> 5k12
riq(dc to 50Hz) ---> less 5300Ohm !
If the input resistance of the RUBY buffer is only 53kOhm, then the error at 20Hz is -1dB. However, when loaded with 500kOhm, the maximum error at 20Hz is only -0.1dB. So if the deepest bass on a long-playing record fades, it is due to the input resistance of the incredibly interesting buffer in the form of the diamond. The most extreme would be -1dB at 20Hz. I have already discussed this fact.
@alugner
Use at least 470µF charging capacity. If the two capacitors are only 47µF, then the reason for the somewhat thin low bass impression has already been identified. This capacitor is more or less a battery and, the larger the series resistors are, in our case it's 75 Ohm, it must be up to 1000µF. Otherwise the bass will fade.
see also my posting #26
kindly,
HBt.
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@EdGr
Remember that we need a current-to-voltage converter - and that is the RIAA network, (or even) our frequency-dependent negative feedback resistor. Just like in the OREAD-EQ, this trick (the current injection) is what makes it special. It may be old hat, but who can still distinguish these subtleties today?
regards,
HBt.
Remember that we need a current-to-voltage converter - and that is the RIAA network, (or even) our frequency-dependent negative feedback resistor. Just like in the OREAD-EQ, this trick (the current injection) is what makes it special. It may be old hat, but who can still distinguish these subtleties today?
regards,
HBt.
Should I reveal the secret Ed 😉.
It's quite clear that other mothers also have beautiful daughters. The important thing is that we keep the tradition alive and can enjoy our record collections as much as possible - as I write this, my turntable is spinning the black disk. Well, and that we show our youngsters what quality is.
