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Catman's Analog Musings

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Here is  Bruce Heran's  review of 6 phono preamp kits, his valve "Groove"(aka Groovewatt http://diyaudioprojects.com/Tubes/RIAA-Phono-Preamp/    http://www.oddwattaudio.com/) is rated highly.

 

 http://diyaudioprojects.blogspot.com.au/2011/11/informal-comparison-of-six-phono.html

 

Felix, would you consider building a valve-based phono stage?

 

 

 

 

Edited by audiofeline

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19 minutes ago, audiofeline said:

Here is  Bruce Heran's  review of 6 phono preamp kits, his valve "Groove"(aka Groovewatt http://diyaudioprojects.com/Tubes/RIAA-Phono-Preamp/) is rated highly.

 

 http://diyaudioprojects.blogspot.com.au/2011/11/informal-comparison-of-six-phono.html

 

Nice design.  Amazing how many variations can be found on the old RCA circuit from their tube manual.     I never got around to trying SRPP stages on my phono preamps.   The standard circuit from RCA with good components, DC heaters,  just sounds so good I never bothered, but I do have to wonder how much better it sounds , or not, for all the extra work.

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The 'sound' of phono preamp hiss.

 

G'day all, over the years of my dabbling with phono preamps, the sound of phono preamp 'hiss' especially with the inputs 'open' is sometimes unexpected in its 'sound'.  Mostly it is a 'hiss' but not always! 

 

Two of my phono stages sound distinctly different in terms of their 'hiss'.  My ANT Kora 3T SE and now my Schiit Mani.  In both cases the phono stage 'hiss' sounds more like a 'whoosh'.  I am advised that the Mani uses a particular op amp along with passive RIAA equalisation, and the ANT Kora 3T SE likewise uses passive equalisation and 'industrial' FET's not normally used for audio applications.  At the very least, it's interesting.  Regards, Felix. 

Edited by catman
Addition.

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Guest gmdb

Hi Felix

 

Right now I have no hiss from the phono amps. I use MC carts and an SUT so I am always to looking to find the best placement for the SUT and the phono amp.  Hum can be an issue until you get the positions right.  But then it is dead quite and there is no hiss.  I use the Graham Slee Reflex M with the SUT but I recently tested my Graham Slee Genera and the was no hiss with the Genera either.  And the Genera is quite cheap. I sold my Genera secondhand for $150. 

 

I mostly use integrated amps but I have an integrated 300B amp which is essentially a power amp with a volume control.  Sometimes I need more power from it and then I hook up a preamp and run the 300B in power amp mode. And then I notice the hiss - the noise floor - of the preamps.  

 

cheers

 

Geoff m

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G'day mate, that's interesting.  In my observation no MM phono stage is entirely hiss free.  Quite frequently the self inductance of the cartridge itself is a factor with high inductance cartridges tending to be 'noisier'.  It is always a technical challenge but remarkable things can be done with good care and design.  Regards, Felix.       

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Strange.  I don't hear any hiss from my phono amps.    Are you saying you hear hiss at normal listening levels of gain?

 

 

 

 

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G'day mate, lift the stylus off the record and turn the volume to max and I'll guarantee that you'll hear 'some' hiss.  The less the better!  Regards, Felix. 

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Hi Felix.  Yes, I see now.  If I turn it up to full volume I can hear the hiss with my ear very close to the speaker.  At normal listening levels - which is quite loud at my place - the hiss isn't audible. 

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2 hours ago, gmdb said:

Hi Felix.  Yes, I see now.  If I turn it up to full volume I can hear the hiss with my ear very close to the speaker.  At normal listening levels - which is quite loud at my place - the hiss isn't audible. 

 

Same here, Geoff.  :)

 

3 hours ago, catman said:

G'day mate, lift the stylus off the record and turn the volume to max and I'll guarantee that you'll hear 'some' hiss.  The less the better!  Regards, Felix. 

 

That's a pretty strange 'test', IMO, Felix.  :ohmy:  Sure, the less the better - but that hiss is not coming exclusively from your phono stage!

 

A phono stage produces a specified output for a given input - for instance, if it's a 40dB gain MM phono stage ... it will output 500mV when the cart is producing 5mV.

 

The signal then goes through one's preamp - which:

  • amplifies the signal (I'm talking active preamps here), and
  • has a volume control, to get the sound coming from the speakers at the level you want (since the power amplifier, by definition, amplifies the signal it receives from the preamp).

 

So if you "lift the stylus off the record and turn the volume to max" ... you are not just listening to phono stage hiss - you are listening to preamp hiss as well.

 

But, sure, you can compare the hiss that each of your phono stages has by putting your ear to the speaker (as Geoff mentioned) and listening - all at the same preamp volume!

 

Of course, given that you say different carts produce different levels of hiss ... all these phono stage comparisons have to be done with the same cart.  :)

 

Andy

 

 

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G'day all, unrealistic?  No I really don't think so.  On my systems anyway I have proven that pretty well all the 'hiss' comes from the general area of the phono preamp and connected components (i.e., the phono cartridge).  Regards, Felix. 

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G'day mate, yes you are quite right, but zero hiss is an impossibility.  Regards, Felix.       

 

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Guest gmdb
1 minute ago, aussievintage said:

Felix, the hiss only needs to be inaudible at normal listening levels.

True, but I think Felix is actually interested in the type of hiss that phono amps may produce, or perhaps wonders why there is any hiss at all. 

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1000 times the gain on a mc can really show up the weakness in the chain and the reason some phono stages command mega prices. just tried mine at full volume and no hiss. (BMC MCCI) but I just recently sunk a 2M copper rod into the ground right behind the power point and that may have drained the last iota of hiss. 

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On 12/23/2017 at 6:23 PM, gmdb said:

True, but I think Felix is actually interested in the type of hiss that phono amps may produce, or perhaps wonders why there is any hiss at all. 

It's not a phono amp thing per se.  All components in a circuit may exhibit thermal noise. This is where it comes from.   Some, like some types of  resistors, are more noisy than others.   Normally this is not a problem but when you amplify it many times, you eventually get to hear it as hiss.  Phono amps, because they deal with very low level signals, have to add gain at the front of a long signal chain resulting in lots of gain from end to end, and so, low noise components must be used to avoid the hiss becoming audible. 

 

Same thing happens to microphone amplifiers and anywhere else high gain is used, not just phono amps     Components selected for low noise should be used.  As an example, common transistors used in early preamps used to be too noisy, but you could buy specially selected versions (usually with suffix letters on the number to indicate this).  The microphone inputs on my AKAI reel to reel were like this.  Very hard to get a replacement with thr right suffix letters, and I had to use a 'normal' one.    Hiss became audible unfortunately.  

 

The point is, it is manageable.  If you have to turn the volume right up, or stick your ear next to the speaker to hear it, then you have no problems.  You can never eliminate it, just make sure the signal to noise ratio is such that you can't hear it.

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G'day mate, component wise, yes it's all true and this is why I only use metal film resistors in critical audio applications for the lowest possible noise, however 'inoptimum' circuit design can make any given circuit needlessly noisy, when it needn't be. 

 

Phono applications tend to be especially demanding in this respect!  Although at 'normal' listening levels hiss may not be audible, however the effect on the ultimate signal to noise ratio may be considerable and 'ultimately' audible.  That aspect worries me!  Regards, Felix. 

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14 minutes ago, catman said:

  Although at 'normal' listening levels hiss may not be audible, however the effect on the ultimate signal to noise ratio may be considerable and 'ultimately' audible.  That aspect worries me!  Regards, Felix. 

 

That's the bit I can not agree with.  What is an "ultimate signal to noise ratio" anyway?   It should be what comes out of the speakers.   What mechanism makes a very low level noise ultimately audible when you agree at the start it is NOT audible?  

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G'day mate, well that's the difference between quiet/very quiet and silent.  Regards, Felix. 

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5 minutes ago, catman said:

G'day mate, well that's the difference between quiet/very quiet and silent.  Regards, Felix. 

 

Well, ok Felix, it's your thread after all. 

 

oh and Happy Christmas !!!

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4 hours ago, aussievintage said:

 

That's the bit I can not agree with.  What is an "ultimate signal to noise ratio" anyway?   It should be what comes out of the speakers.   What mechanism makes a very low level noise ultimately audible when you agree at the start it is NOT audible?  

Volume? I took it as meaning 'no audible hiss at normal volume' but 'audible hiss at very loud volume'........ like my set up. I hear a slight buzz at very high volume levels (which is most of the time but it doesn't effect the music:cool:) but little to no noise at lower/'normal' volume levels......I think that's what Felix meant but I might be wrong.:P

Edited by stevoz

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May be, but I can't see the point in worrying about hiss that cannot be heard without winding it up too loud to actually use.

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7 minutes ago, aussievintage said:

May be, but I can't see the point in worrying about hiss that cannot be heard without winding it up too loud to actually use.

Me too......:thumb:

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G'day all, 'ideally' hiss from a phono stage should be as low as possible, but maybe it is a moot point in any case as for example my Schiit Mani is a stunningly good sounding phono stage yet it has a slightly higher than average level of phono stage hiss, however it is barely noticeable during play!  Regards, Felix.     

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'In absolute terms'.

 

G'day all, leading up to Christmas I've been playing a lot of music, on both record and CD, and this afternoon I asked myself the question, in absolute terms of sound quality, is even a mid range CD player better than a top notch turntable and phono cartridge combination?  Dare I even ask the question?!  Regards, Felix.

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