Musical Fidelity DAC/pre & technics 1200 incompatibility gain distortion

[Ted-M]

This is crazy! Musical Fidelity are charging nearly £1000 for a an AD converter with no variable input gain setting and not enough headroom to cope with a line level phono stage?? If they don't want to add a variable input gain they could at least put a -20dB pad button for hot sources. I would take it up with Musical Fidelity rather than trying to reduce gain before you hit the inputs, it really is their problem.

 

[Julf]

This is crazy! Musical Fidelity are charging nearly £1000 for a an AD converter with no variable input gain setting and not enough headroom to cope with a line level phono stage?? If they don't want to add a variable input gain they could at least put a -20dB pad button for hot sources. I would take it up with Musical Fidelity rather than trying to reduce gain before you hit the inputs, it really is their problem.

So what DACs can handle 14V on their analog inputs?

 

[Bigbobby666]

This is crazy! Musical Fidelity are charging nearly £1000 for a an AD converter with no variable input gain setting and not enough headroom to cope with a line level phono stage?? If they don't want to add a variable input gain they could at least put a -20dB pad button for hot sources. I would take it up with Musical Fidelity rather than trying to reduce gain before you hit the inputs, it really is their problem.

They're solution was to alter the analogue in's to 2volt... but that wont really help from what i now 'kind of' understand!

Out of interest on a traditional analogue pre-amp what is the headroom that you generally get regarding voltage capacity?

 

[Julf]

They're solution was to alter the analogue in's to 2volt... but that wont really help from what i now 'kind of' understand!

Out of interest on a traditional analogue pre-amp what is the headroom that you generally get regarding voltage capacity?

In an analog chain, the gain structure is usually set so that the power amp is the first one to clip. It is easy to make an analog pre able to deal with 10 V or so on the line in, but usually the power amp is clipping badly at that point.

Digital is different in that it has a well-defined maximum amplitude (full scale).

 

[Ted-M]

So what DACs can handle 14V on their analog inputs?

Are you suggesting this isn't a problem with the AD converter in the DAC? The problem seems to be that the AD converter cannot handle a hot (?) signal from a standard phono preamp. The problem lies with the inability to adjust the input gain in my opinion, especially as this is rather an expensive bit of kit.

 

[Ted-M]

Actually the AD/DAC in my studio will handle any signal as it has variable gain inputs, but it is primarily for studio use rather than hifi use, but of course the principle is the same that if you have an A/D converter then you really need input gain adjustment of some kind otherwise you will run into the problem described by the OP.

 

[Paul R]

This is crazy! Musical Fidelity are charging nearly £1000 for a an AD converter with no variable input gain setting and not enough headroom to cope with a line level phono stage?? If they don't want to add a variable input gain they could at least put a -20dB pad button for hot sources. I would take it up with Musical Fidelity rather than trying to reduce gain before you hit the inputs, it really is their problem.

They're charging nearly £1000 for a DAC/pre. It has a bonus an ADC which will also feed the digital outputs.

The core of the problem is the ludicrously high output levels of 'cheap' phono stages and the healthy output of modern Ortofon MM carts. The ADC I use is either 2v or 1v for clipping and I have no problems connected to my phono stage. (Linn carts, 1v sensitivity, AT33PTG, 2v.)

It's worth looking at the specs of the Rega Fono A2D, to see at what input it clips its internal ADC.

Paul

 

[Ted-M]

They're charging nearly £1000 for a DAC/pre. It has a bonus an ADC which will also feed the digital outputs.

The core of the problem is the ludicrously high output levels of 'cheap' phono stages and the healthy output of modern Ortofon MM carts. The ADC I use is either 2v or 1v for clipping and I have no problems connected to my phono stage. (Linn carts, 1v sensitivity, AT33PTG, 2v.)

It's worth looking at the specs of the Rega Fono A2D, to see at what input it clips its internal ADC.

Paul

I respect your opinion but the OP stated he tried three phono stages which at a quick glance seem to range from £85 to £400. They are not 'cheap' phono stages and apparently they all clipped the AD converter. The ADC may be a 'bonus' feature but if I was spending nearly a grand on a piece of kit I would expect all its features to function correctly.

Musical Fidelity have set the gain input too high to leave headroom for hotter inputs. A simple high/low input gain button would have solved the problem, or setting the gain input lower as standard. Seems to me like the problem lands fair and square in the lap of Musical Fidelity.

 

[Julf]

Musical Fidelity have set the gain input too high to leave headroom for hotter inputs. A simple high/low input gain button would have solved the problem, or setting the gain input lower as standard. Seems to me like the problem lands fair and square in the lap of Musical Fidelity.

A gain button would have solved the problem, but it is always easier to use an attenuator compared to having to add amplification, so it is better to err on the side of too much rather than too little sensitivity.

Anyway, a digital device has a predictable maximum input and output level. An analog mc amp doesn't, as signal levels of different pickups vary widely. Thus the natural place for gain adjustment is the mc preamp.

 

[Bigbobby666]

I respect your opinion but the OP stated he tried three phono stages which at a quick glance seem to range from £85 to £400. They are not 'cheap' phono stages and apparently they all clipped the AD converter. The ADC may be a 'bonus' feature but if I was spending nearly a grand on a piece of kit I would expect all its features to function correctly.

Yes... My thoughts exactly!

 

[Ted-M]

A gain button would have solved the problem, but it is always easier to use an attenuator compared to having to add amplification, so it is better to err on the side of too much rather than too little sensitivity.

Anyway, a digital device has a predictable maximum input and output level. An analog mc amp doesn't, as signal levels of different pickups vary widely. Thus the natural place for gain adjustment is the mc preamp.

24bit AD conversion doesn't need to be peaking near the red, so there isn't much reason to have the sensitivity overly high, I wonder what Musical Fidelity were expecting as sources? Tuner, Turntable, CD, I would expect the CD to be the hottest source here? Anyway, I'm not impressed by their thinking!

 

[Bigbobby666]

24bit AD conversion doesn't need to be peaking near the red, so there isn't much reason to have the sensitivity overly high, I wonder what Musical Fidelity were expecting as sources? Tuner, Turntable, CD, I would expect the CD to be the hottest source here? Anyway, I'm not impressed by their thinking!

Well they said they built it expecting digital analogue inputs like a TV RCA etc... bloody stupidity if you ask me, of course the first thing any music fan would think of using would be Vinyl!