I’m surprised at how much mains noise is evident on the plot given that the PSU is s wall wart. I think the wall wart is just an AC transformer (not sure about this, just guessing) and the regulation and filtering is done on actual preamp board. Mains harmonics are almost always the result of common impedance coupling and/or supply rail ripple coming through to amplifier stages.
There is a BIG problem with ASR measuring method of noise and SINAD of MM phono preamplifiers. The method with low output impedance AP generator gives incorrect results with respect to real world conditions when the preamp is connected to real MM cartridge with R + jwL impedance and 47k load resistor. The ASR method does not take into account the opamp input current voltage noise density (OPA1612) and also not takes into account thermal noise of 47k resistor that is shunted by cartridge R + L and increases with frequency radically. The real world SINAD with the bipolar opamp is then 10 - 20 dB worse than shown in ASR charts. For those interested, I have created a paper with detailed explanation, simulations and real world measurements, and comparation of bipolar and JFET opamp results:
https://pmacura.cz/MMpre_measuring_methods.pdf
https://pmacura.cz/MMpre_measuring_methods.pdf
Member Skeeter tried to explain that over there but Amrim is having nothing of it. If you use an AD797 as a phono amp and measure the noise with the input shorted you will get a fantastic result. Connect a cartridge and it will be 8-10 dB worse than a good JFET input opamp.
On a separate note, I don’t think overload performance is being displayed or measured correctly over there either. Ideally feed the RIAA phono preamp through an inverse RIAA network and set the input stimulus reference to initially 5 mV at 1kHz and then to a series of frequency vs distortion sweeps in +6dB steps. If you have a well designed phono stage, the overload capability will be at least 20 dB above the initial 5mV 1kHz reference across the whole audio bandwidth. Note also, it’s a good idea to sweep up to at least 50 kHz or higher if possible to make sure there are no HF anomalies like peaking.
There are cases of those who followed ASR-based reviews and recommendations getting unpleasant surprises with their purchases… so best to cross-check and verify. Pearl 3 looks pretty good and doesn’t cost too much (to build) 🙂
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Unfortunately, over there the AP is being used as a ‘measurement weapon’, and as a tool of enquiry.
Sans vouloir offenser personne, je trouve que ce préampli fait bonne figure. D'ailleurs, tous les tests vus sur YouTube en attestent. Le DIY c'est autre chose mais pour un produit fini c'est excellent vu le prix demandé et le soin apporté à la conception. Vous vous êtes peut-être demandé combien il aurait coûté s'il avait été fabriqué en Europe ? Au moins 5x le prix demandé. Il est bien parmi les tous meilleurs du classement. Là où tout le monde mettrait un op type ne 5532 pour 2 euros on a droit à un opa 1612 vendu 7 euros pièce sur mouser.
The problem with this is the lack of rumble filter (subsonic highpass). Otherwise it looks like a very good low budget thing
Unfortunately it is exactly as you have said. I have the AD797 with cartridge measured as well. You get the same total noise with cartridge and AD797 as with LM6171 ….. And all of it can be very easily calculated.
Unfortunately, when Amir makes a mistake or does not know something, he is never able to admit such fact. Bad think is that he has great influence to general users. And the forum is supposed to be “scientific”, which it is only sometimes.
Please post in English.Translation:
Without wanting to offend anyone, I think this preamp looks good. Moreover, all the tests seen on YouTube attest to this. DIY is something else but for a finished product it is excellent considering the asking price and the care taken in the design. You may have wondered how much it would have cost if it had been manufactured in Europe? At least 5x the asking price. It is among the very best in the ranking. Where everyone would put an op type ne 5532 for 2 euros, we are entitled to an opa 1612 sold for 7 euros each on mouser.
Amir was doing fine when he was just splitting hairs on DACs, but then he got a few followers, got high on his own supply and here we are… the desire for this kind of technical take down of the audio industry is strong, the industry itself created this problem with highly technical made up garbage. Now we have created a cult that believes its own bs to go along with an industry that does the same.
Can’t argue with that. Hopefully we can keep the discussion here at a technical level without the Fosi fan club. Bit like the discussion about the ultra low distortion amp that can’t drive a sub-4 ohm load. These are all products designed to game a set of measurements that are confined to a narrow set of self-selected criteria that are out of sync with real world requirements.
Slightly off topic, but has anybody pulled the socketed opamps in audio devices like this and made a small PCB which would plug into that existing socket? If the socketed op-amp in the x5 is like the last one in the path, like a buffer, it might be an easy way to add a subsonic filter circuit around a substitute op-amp. Seems like a stacked PCB to plug into the existing op-amp socket could be a plug and play way to add active filters to a circuit without modding the original board.
even much smaller - only 20x45x3 mm [ https://imrad.com.ua/ua/fonokorekto...vok-zvukoznimacha-z-ruhomim-magnitom-mm-50452 ]
I saw this on YouTube any thoughts? I know that this is subjective, but interesting. The timing is around the 50 min mark, I think.
https://www.google.com/search?q=pea...ate=ive&vld=cid:518794ea,vid:C-mbkiVBQ9I,st:0
https://www.google.com/search?q=pea...ate=ive&vld=cid:518794ea,vid:C-mbkiVBQ9I,st:0
Questi post creano confusione per le persone che non sono pienamente in grado di comprendere misurazioni o circuiti. Quando li leggono, non riescono proprio a capirci niente, supponendo che tutte le unità pre-phono abbiano problemi ed errori. Il fatto è che Audioscienze è praticamente l'unica che si occupa di misurazioni e, indipendentemente dalle convinzioni personali o dagli errori, se stabilisci uno standard di misurazione, anche se non è del tutto corretto, e lo usi in modo coerente su tutti i dispositivi testati, avrai comunque risultati comparabili su cui basare un giudizio, anche se quel giudizio non è perfetto, è qualcosa. Qualcun altro si è dedicato alle misurazioni in modo più scientifico? Questa è una domanda e non sto cercando di essere il "difensore" di nessuno. Certo, offre comunque un buon servizio per i profani come me, aiutandoci almeno in parte a evitare di essere truffati o di credere a semplici esagerazioni invece che ai fatti.
o3-mini
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