How much hiss should be acceptable in a TT rig?

izafar

Ever since I upgraded the TT section from Technics table/phono pre built in the AVR to Music Hall MMF5/Parasound ZPhono preamp, I am getting a lot more hiss during the playback. I was trying to live with it so far, but then yesterday I played a brand new 180gm copy of "Brother in Arms". This album is wonderfully cut and the surface noise is non-existent, which leaves the hiss to pop out a lot more then all my other LPs. It really made the LP unlistenable and now I need some of your help to fix this.

Based on my understanding the source of hiss is Zphono pre-amp. When I start looking at other phono pre-amps, I read that all of them produce some hiss. I want to find out how much hiss should be acceptable in a TT rig, and what should I get as a replacement for Zphono (budget is around $400 for new or used).

madmax

There shouldn't be so much that you notice it. I've had some really good preamps that didn't have much hiss and two older generation cheap ones that had very little. Is the cartridge output reasonable for the preamp you have?
madmax

izafar

The cartridge is Goldring 1012GX which has 6.5mv output. Which should be sufficient for the phono pre-amp. The complete specs for this cartridge are here:

http://www.musicdirect.com/products/detail.asp?sku=AGOLD1012GX

mhardy6647

An MM phono preamp is a high gain device, and it will produce noise: the noise is typically "shot noise" in transistor circuits, and thermionic noise in tubes -- the net result is the same; random thermal noise that sounds like hiss.

You can look at the signal to noise ratio of your phono preamp (if specified), the reference voltage (2.5 mV? 5 mV? 10 mV?) and calculate how much noise you can expect to hear. At higher volumes, it probably won't be inaudible. Consider that a 60 dB signal to noise ratio would put the noise at one millionth of the signal. 10 mV / 1,000,000 = 10 nV (nanovolts) of noise from a 10 mV signal. But the S/N will still be no better than 60 dB at your loudspeaker. Let's say your loudspeaker is (re)producing a signal at 10 VAC RMS. Now you've got 10 uV (microvolts) of noise. If your speakers are sensitive, yup, you'll hear it.

Also remember that a S/N specified at, say 80 dB referenced to 10 mV is only 70 dB referenced to 1 mV.

madmax

So is the gain set at 46db for your MM? You would certainly get a lot more noise if it were set for a MC at 61db gain.
madmax

izafar

madmax wrote: »

So is the gain set at 46db for your MM? You would certainly get a lot more noise if it were set for a MC at 61db gain.
madmax

The gain is set at 46db for MM cartridge. I get a lot more noise & some distortion when I move it to 61 DB for MC. There is also an AC polarity swicth at the back and I have tried both positions, that have no impact on the hiss.

S/N ratio for MM is 84db which looks pretty respectable. Can this be an issue with this particular unit?

madmax

I tried to look up the acoustech to see what it was noise wise but there were no published specs, looked up my manley and they had a whole page of noise specs and couldn't make heads nor tales out of it.
madmax

izafar

I just started looking at the specs for S/N ratios, and all the pre-amps I looked at have very good rating of >80db. But I believe all will produce different level of actual hiss. That's why I want to get feedback from club members to see what works based on their experience in this price range.

fredv

What if the input is unplugged from the phono preamp? If the hiss persists, then it may point to that's the noise floor of the pre.

billbillw

My Sony ES preamp has a pretty decent phono stage. The MM S/N is like 95dB and the MC is like 83dB. I never really heard a hiss when I used a MM cart. Now I have a MC cart. I can hear a slight hiss when I have the volume up to like 11 o'clock, but its usually less than what the noise floor on the album. It definitely doesn't interfere with my listening pleasure. I actually found as much or more tape hiss on one of my CDs recently, and it was a fairly new album too, which surprised me (Diana Krall-When I Look In Your Eyes).

I would double check your leads to the cartridge, maybe put some pro-gold on them or something. If the specs are accurate, and all the connections are clean, you should not have excessive hiss, unless something is amiss in the phono stage.

izafar

I did some more testing last night, here are the results:

1. Hiss remains when I unplug the Cartridge input, i-e the issue is within the Phono stage, not in the Cart & wiring

2. I have a slider switch for MM/MC selection at the back. When switch is moved to MC the hiss goes down. My first conclusion was that somehow the switch is wired wrong. I then played some music on MC setting and found that its level was bellow the MM setting, but at the same time the music was sounding very harsh, like someone one has muted the mid range and treble.

My understanding is that on MC setting I should get more gain, but the above experience tells me that there is something wrong with unit. I will be contacting Parasound technical support today to see what they suggest.

madmax

Yes, on the MC setting you should definitely get more gain. If all is well both should be of similar quality unless the signal is overloading the pre. To be more precise, a quiet passage played on both MC and MM should be of similar quality with the only difference being gain.
madmax

mhardy6647

The cartridge loading for MC should be different than MM (something like 100 ohms for MC vs. 47k ohms for MM); the frequency response of a mismatched cartridge will be altered as a consequence.

billbillw

izafar wrote: »

I did some more testing last night, here are the results:

2. I have a slider switch for MM/MC selection at the back. When switch is moved to MC the hiss goes down. My first conclusion was that somehow the switch is wired wrong. I then played some music on MC setting and found that its level was bellow the MM setting, but at the same time the music was sounding very harsh, like someone one has muted the mid range and treble.

My understanding is that on MC setting I should get more gain, but the above experience tells me that there is something wrong with unit. I will be contacting Parasound technical support today to see what they suggest.

This actually sounds normal because of the impedance mismatch like mhardy said. I remember trying (the MC setting) this with my setup when I still had a MM cartridge and it was distorted, but not any louder.

hearingimpared

I've spoken to the engineer at Spectral who was instrumental in the design of my preamp. He told me that there will be a hiss with the tonearm on the armrest with the volume up. That hiss should then turn into music/signal once the stylus is running the music grooves. I've found this to be true. I get no hiss at all even in the quietest passages.

hearingimpared

mhardy6647 wrote: »

The cartridge loading for MC should be different than MM (something like 100 ohms for MC vs. 47k ohms for MM); the frequency response of a mismatched cartridge will be altered as a consequence.

Don't forget that there should be a capacitive load on MM carts also. Actually adding the capacitance to the load smooths out the frequency response of MM carts.

izafar

hearingimpared wrote: »

I've spoken to the engineer at Spectral who was instrumental in the design of my preamp. He told me that there will be a hiss with the tonearm on the armrest with the volume up. That hiss should then turn into music/signal once the stylus is running the music grooves. I've found this to be true. I get no hiss at all even in the quietest passages.

That was my expectation too, but somehow on that table hiss never went away and was clearly heard at my normal listening level. I have since then upgraded to a CIAudio VPP-1 phono stage with upgraded outboard supply (VAC-1). This little piece is dead quite and sound wonderful. I will do a detailed review latter.

SCompRacer

izafar wrote: »

I have since then upgraded to a CIAudio VPP-1 phono stage with upgraded outboard supply (VAC-1).

Excellent choice! You get much bang for the buck from Dusty.

I wouldn’t get too wound up about hiss from the phono stage if you crank the volume all the way up with no music playing. Lift the stylus at reference levels and if you don’t hear anything, life is good.

I must put in a plug for my ModWright SWLP with phono stage. At the Chitown Polk Fest, I turned the volume knob full tilt with no music playing on CD and phono to show how quiet it was. Not bad for tubes and a 68dB gain phono stage.

hearingimpared

SCompRacer wrote: »

Excellent choice! You get much bang for the buck from Dusty.

I wouldn’t get too wound up about hiss from the phono stage if you crank the volume all the way up with no music playing. Lift the stylus at reference levels and if you don’t hear anything, life is good.

I must put in a plug for my ModWright SWLP with phono stage. At the Chitown Polk Fest, I turned the volume knob full tilt with no music playing on CD and phono to show how quiet it was. Not bad for tubes and a 68dB gain phono stage.

How is the break in going with those teflon caps? Have you noticed any changes in tone?

SCompRacer

hearingimpared wrote: »

How is the break in going with those teflon caps? Have you noticed any changes in tone?

The Teflon cap and tube rectified PS upgrade provides increased body or weight, along with a slightly warmer tonal balance. The mids are smoother, richer. Dan calls it more meat on the bones. The noise floor is quieter. The upgrade actually adds to the punchy, tight dynamics the SWL 9.0 with Sonicaps was known for.

I was skeptical of the 200-400 hours burn in, but there is no way one could acclimate to the sonics of the Teflon caps when they are new. I got soggy bass, a thin midrange. Diffused vocals. A sinking feeling of what have I done. Kind of like what you may be going through with your Sonicap burn in.;)

I am approaching the 400 hour mark and it continues to sound better. My active crossover is now set in the minus 2-3 dB range instead of zero or positive gain. The kewl thing is not only the phono sounds better, redbook and SACD do too.:cool:

hearingimpared

SCompRacer wrote: »

A sinking feeling of what have I done. Kind of like what you may be going through with your Sonicap burn in.;)

Yep I had those same thoughts at first. It is now in the 100th hour of burn in and I can tell you the rich tone of the cello is starting to come through as I've been using the Living Stereo SACD of Don Quixote as burn in music, the detail WOW the detail is starting to really settle in. I played some female vocals and I noticed a subtle improvement in sibilance.

My wife has been playing 70s & 80s dance music as well as Phil Collins during the day and is thrilled with the sound.

It does keep getting better each day.

cmy330go

izafar wrote: »

That was my expectation too, but somehow on that table hiss never went away and was clearly heard at my normal listening level. I have since then upgraded to a CIAudio VPP-1 phono stage with upgraded outboard supply (VAC-1). This little piece is dead quite and sound wonderful. I will do a detailed review latter.

So what happened to the Parasound? Did it need repairing/replacing? I have the predecessor to yours and have had zero issues with noise.

Just curious.

izafar

cmy330go wrote: »

So what happened to the Parasound? Did it need repairing/replacing? I have the predecessor to yours and have had zero issues with noise.

Just curious.

The parasound unit was fine, just had too much hiss per my expectations and also somehow the combo with my dared line stage was contributing to the problem. The VPP-1 works fine with my line stage and is much quitter/better unit to begin with.