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New member, phono stage frustration

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Richardl60 View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jul 2019 at 6:29pm
sure Graham can give you the tech side but if his says 9.2v & 10v you are well inside the phono stage capabilities 
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Lucabeer View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Lucabeer Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jul 2019 at 7:15pm
I use an Ortofon 2M Bronze/Black which has a similar output level, with the Reflex M. No problems at all.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jul 2019 at 10:23am
Thank you for bringing this to my attention.

Most phono stages will provide sufficient headroom for such tests. I don't think you need worry about more headroom in the phono stage.

It would seem that the modern way of providing input switching in integrated amplifiers, is the problem. That being the use of bilateral logic switches.

I looked up the 74HC4051 which I have seen used in one popular integrated amplifier and I guess it will be in use in a few others.

(http://www.ti.com/lit/ds/symlink/cd74hc4051-ep.pdf)

Listed amongst its features is "Wide Analog Input Voltage Range of ±5 V Max"

The maximum rms voltage is therefore 3.5V, unless attenuated, but each line input element (in the above case) is via a 10k resistor, which forms a potential divider switch with the elements on or off resistance.

If your phono stage outputs 918mV for a 0dB signal using the 6.5mV output cartridge, then at +12dB it is 4 times that, which is 3.672V rms. Therefore it is being clipped by the integrated amplifier's input switching, albeit softly due to the 10k resistor (if of similar configuration).

Commonly 0dB is output from a record with velocity of 5mV/sec., whether LPs or singles. Therefore the cartridge output of 6.5mV will hold true at 0dB.

The RIAA recording characteristic establishes a maximum recording velocity of 25 cm/sec in the range of 800 to 2500 Hz.

This means the output can rise by a factor of 5, or +14dB. Therefore if the phono stage is outputting 918mV at 0dB, it can rise to 4.95 volts.

However, in the digital domain there is nothing above 0dB - it all appears below 0dB - so >3V covers just about all digital sources and such an integrated amplifier will never suffer this distortion.

It seems obvious that the amplifier designer is not conversant with vinyl reproduction.



Edited by Graham Slee - 16 Jul 2019 at 10:28am
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Pwog Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jul 2019 at 3:33pm
I use an Ortofon Bronze 2M and just finished home auditioning the Reflex M. I never heard my system sound better, (until I auditioned the Accession M). if the Accession isn’t in your budget, you will love the Reflex M.
Paul
Acoustic Research ES-1, Ortofon 2M Bronze, Ayre C-5xemp disc player, Dynaco SCA-35 (updated), Dynaco ST-70 (updated and modified), Revel performa M20, Accession M, CuSat 50 interconnects
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Post Options Post Options   Thanks (1) Thanks(1)   Quote DeepEnd Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jul 2019 at 2:39pm
I agree this has/may have been missed by some amplifier designers in the pursuit of easily switched inputs, but unless the end user is also aware of the issue then potentially when testing a cartridge the distortion heard might not be the cartridge miss-tracking but the actually the amp clipping.

I don't think my 4.0mV cartridge and 41db gain phono stage are going to be an issue but something like a Rega at 7.2mV and gains above 41db could well be an issue with lots of amps.
Paul

Rega RP8, Audiomods S5, A&R P77/SP, P78+FG2 and Nagaoka MP11Boron +Paratrace.
Musical Fidelity A3.2, Rega RS3
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