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Integrating a turntable into a digital system

mike70

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I run my phono pre into a miniDSP Flex. Well, not directly. The only caveat to this setup is you need to attenuate the signal between the phono pre and the Flex because the Flex clips at only 2V input on the unbalanced version. I run my Flex with Dirac Live between the preamp and power amp for this reason, but if I was using the Flex as a preamp I'd definitely stick a decent-quality passive attenuator in between, like a Schiit Sys or JDS Labs OL Switcher, with the pot set to 12 o'clock. If the overall gain ends up being too low it can be bumped up without adding noticeable noise floor in the Flex.

but ... if my math is good ... the output of a cartridge is more or less 4mv or 5mv (MM, but if you have MC, you need to upgrade to something like that).
Then the phono preamp usually have 40dB of gain ... that means x100.

so ... in the end you have ... 0,5 volts (well under 2v).

the higher output cartridges i know are some Dj cartridges with 7mv / 8mv ... nothing more than that.

how can you overdrive the 2v analog input?
 

JeremyFife

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but ... if my math is good ... the output of a cartridge is more or less 4mv or 5mv (MM, but if you have MC, you need to upgrade to something like that).
Then the phono preamp usually have 40dB of gain ... that means x100.

so ... in the end you have ... 0,5 volts (well under 2v).

the higher output cartridges i know are some Dj cartridges with 7mv / 8mv ... nothing more than that.

how can you overdrive the 2v analog input?
Agree - I run my turntable (MM admittedly) to a zen phono then balanced output directly to the miniDSP Flex (Balanced) ... no issues, works lovely
 

mike70

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Agree - I run my turntable (MM admittedly) to a zen phono then balanced output directly to the miniDSP Flex (Balanced) ... no issues, works lovely

That's what I want to do in some time.
 

levimax

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Agree - I run my turntable (MM admittedly) to a zen phono then balanced output directly to the miniDSP Flex (Balanced) ... no issues, works lovely
If you don't have a phono pre-amp you may want to try what I do which is run a short cable from TT to a balanced transmitter (modified with 47K input impedance) and then from balanced transmitter to ADC and do RIAA digitally. Works very well for me and is cheap. For balanced transmitter this is the one I built, just changed input resistors to 47K
 

AaronJ

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but ... if my math is good ... the output of a cartridge is more or less 4mv or 5mv (MM, but if you have MC, you need to upgrade to something like that).
Then the phono preamp usually have 40dB of gain ... that means x100.

so ... in the end you have ... 0,5 volts (well under 2v).

the higher output cartridges i know are some Dj cartridges with 7mv / 8mv ... nothing more than that.

how can you overdrive the 2v analog input?
YMMV depending on the rest of the setup. The cartridge's specs are at 5cm/sec, but hot inner grooves can be several times higher than this. 4mV to 5mV does not represent peaks. If you're running a low-ish output MM like 3.5mV, or in the example of the iFi Zen Phono running 36 dB instead of 40, you might not ever clip. I have definitely clipped using a 5mV cart on inner grooves with 40dB. Clipping won't be constant obviously, and may not even be common. But it's easily avoidable.
 

mike70

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YMMV depending on the rest of the setup. The cartridge's specs are at 5cm/sec, but hot inner grooves can be several times higher than this. 4mV to 5mV does not represent peaks. If you're running a low-ish output MM like 3.5mV, or in the example of the iFi Zen Phono running 36 dB instead of 40, you might not ever clip. I have definitely clipped using a 5mV cart on inner grooves with 40dB. Clipping won't be constant obviously, and may not even be common. But it's easily avoidable.

maybe you're listening to overload on the phono preamp ... the cartridge with 5mv output needs spectacular cantilever movement to generate 10mv with groove oscilation (a "pop" from dirt is another stuff, but is not something continous ... throw the record to the trash can otherwise :)).

as an example, i remember the mofi studio phono worked well with mofi cartridges (AT based) ... it not worked good with a higher output cartridge like Ortofon Blue (was recognized by Mofi itself, then i returned the preamp).
 

Avp1

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maybe you're listening to overload on the phono preamp ... the cartridge with 5mv output needs spectacular cantilever movement to generate 10mv with groove oscilation (a "pop" from dirt is another stuff, but is not something continous ... throw the record to the trash can otherwise :)).

as an example, i remember the mofi studio phono worked well with mofi cartridges (AT based) ... it not worked good with a higher output cartridge like Ortofon Blue (was recognized by Mofi itself, then i returned the preamp).

It is assumed that groove can be modulated to +18dB. It means that cartridge output will be 20mV. Always keep headroom for clicks an pops on top of that.
You absolutely do not want ADC to clip.
 

levimax

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It is assumed that groove can be modulated to +18dB. It means that cartridge output will be 20mV. Always keep headroom for clicks an pops on top of that.
You absolutely do not want ADC to clip.
My TT goes to a balanced transmitter to get the proper cartridge impedance loading and then to an ADC. I have been reading about 20 dB of headroom beyond the peak music level which always seemed extreme to me. RME with their new DAC / ADC with phono input claims 6 dB of headroom is enough and my experiments so far indicate that is about right. When you are capturing at 24 bit depth you can turn the ACD input volume down a little and have no problem capturing anything a phono cart can throw at it. I have been experimenting with some damaged records and the most I have seen out of a very loud "pop" (bad enough to cause the record to get stuck) is only about 6 dB beyond music peaks. For normal undamaged records music peaks are far louder than any noise. As far as I can tell a regular ADC (Scarlet and the like) has plenty of gain and headroom to be used with a MM cart. For a MC cart I use a SUT before the ADC.
 

MaxwellsEq

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An ASR discussion on overload:

 

Bob from Florida

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how can you overdrive the 2v analog input?

Phono is not limited to 2 volts like the typical unbalanced digital limit. Even if your cartridge output times the gain of the phono stage is under 2 volts, you still can have peaks above 2 volts. How does the ADC react to levels above 2 volts? The analog input on the Flex is clearly designed for a source such as the unbalanced output of a CD player not phono.
 

Balle Clorin

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Not an issue ,I have Puffin and it logs any cliping, and in my experience it is extremely rare at 61db gain , 100% volume and a MC cart with 0.4mV nominal output. Only a serious scratch( or end of record bump ) can provoke clipping, and clipping in analog or digital domaine never occurred with music On my records.
 

Bob from Florida

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Not an issue ,I have Puffin and it logs any cliping, and in my experience it is extremely rare at 61db gain , 100% volume and a MC cart with 0.4mV nominal output. Only a serious scratch( or end of record bump ) can provoke clipping, and clipping in analog or digital domaine never occurred with music On my records.
I was referring to the Flex under discussion. Its analog input has to be 2 volts or less. Someone recently quoted a suggested overload margin in a phono preamp as 26 db. Doing math. 10 to the x where x = 26/20 = 19.95 or 20 rounded up. For a 5 mv cartridge at 40 db gain (times 100) = .5 volts nominal times 20 = 10 volts peak output before the phono preamp clips. This is 5 times the max input allowed on the Flex. If we back off some and go with 20 db overload margin on the phono preamp - more math yields 5 volts peak out of same setup - .5 mv at 40 db gain phono. This is still 2.5 times max signal allowed with the Flex.
It does not appear the Flex analog input was designed with phono preamps in mind.
 

ilovetinnitus

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Also in i similar situation :) I'm trying to get my turntable (u-turn orbit) connected to my sonos and I've been looking at upgrading my cheap amazon/ebay rca to optical ADC after reading the review https://www.audiosciencereview.com/...s/unbranded-adc-from-ebay-measurements.23962/ I'm not too sure if it'll make a difference, but I have noticed certain records sound a bit muffled, not too sure if that's attributable to the rolloff at lower frequencies

I've seen the swissonic converter suggested, but I live in the US and shipping alone is the same price as the unit itself so it hardly feels worth it. Are there any others? https://www.audiosciencereview.com/...c-converter-ad-24-192-adc-measurements.24187/
 

mike70

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A cheap ADC is what you have and normally they are only a commodity.

A good ADC without phono preamp normally is USB, so, more complicated, you need a computer.

Integrated preamp in the turntable is not a good idea, you ended paying for something you'll need to change sooner or later. My opinion. Stay with what you have or go forward with an external ADC / preamp like the Project or the Puffin
 

wgh52

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I have a similar system plan as the OP: The main signal chain is digital, but I want to integrate a Turntable phono signal coming from a Lehmann Black Cube SE II. My new speaker project is 4-Way active DIY, so the x-over will most probably be the miniDSP Flex Eight.

Now, as the Flex Eight has no ADC, we may need that externally - or would internal ADC even be possible by an internal modification??

I've just come across an Audiophonics ADC which can run 24/96 and feed the Flex Eight cinch coax SPDIF or Toslink. Putting that into a little box with power supply would already do the interfacing trick, but at the potential sound relevant expense of (avoidable) I²S>SPDIF>I²S conversion and two separate clock domains..

Well, the linked Audiophonics board can run as clock slave and also has I²S solder bumps, which (probably) enables Flex Eight integration (by e.g. sacrificing bluetooth...) into the local clock domain.

What's the thinking about this potential option?

Regards,
Winfried
 

antcollinet

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I have a similar system plan as the OP: The main signal chain is digital, but I want to integrate a Turntable phono signal coming from a Lehmann Black Cube SE II. My new speaker project is 4-Way active DIY, so the x-over will most probably be the miniDSP Flex Eight.

Now, as the Flex Eight has no ADC, we may need that externally - or would internal ADC even be possible by an internal modification??

I've just come across an Audiophonics ADC which can run 24/96 and feed the Flex Eight cinch coax SPDIF or Toslink. Putting that into a little box with power supply would already do the interfacing trick, but at the potential sound relevant expense of (avoidable) I²S>SPDIF>I²S conversion and two separate clock domains..

Well, the linked Audiophonics board can run as clock slave and also has I²S solder bumps, which (probably) enables Flex Eight integration (by e.g. sacrificing bluetooth...) into the local clock domain.

What's the thinking about this potential option?

Regards,
Winfried
My thinking is I wouldn't dream of trying to do an internal mod (and I've had a 35 year carreer in electronics development). Just use an external ADC.
 

levimax

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I have a similar system plan as the OP: The main signal chain is digital, but I want to integrate a Turntable phono signal coming from a Lehmann Black Cube SE II. My new speaker project is 4-Way active DIY, so the x-over will most probably be the miniDSP Flex Eight.

Now, as the Flex Eight has no ADC, we may need that externally - or would internal ADC even be possible by an internal modification??

I've just come across an Audiophonics ADC which can run 24/96 and feed the Flex Eight cinch coax SPDIF or Toslink. Putting that into a little box with power supply would already do the interfacing trick, but at the potential sound relevant expense of (avoidable) I²S>SPDIF>I²S conversion and two separate clock domains..

Well, the linked Audiophonics board can run as clock slave and also has I²S solder bumps, which (probably) enables Flex Eight integration (by e.g. sacrificing bluetooth...) into the local clock domain.

What's the thinking about this potential option?

Regards,
Winfried
I have been doing the "TT to ADC " for quite some time. I would recommend a external ADC like the Focusrite Scarlett 2i2 or similar. One thing to keep in mind is that in order to get this to work you really need the "input volume controls" on the ADC.
 
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