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Welshsox
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Analog problem

Hi

For various reasons ive swapped my Quad pre amp for a NAD C 162.

The problem i have is that i cant get sufficient power from the phono stage, it sounds really weak and pathetic. Im using a Clearaudio Virtuoso MM cartridge that on paper puts out 3.4 mV. It worked fine into the Quad but now im just not getting gain, ive tried a Cambridge audio phono stage that introduces 39dB of gain and connected this into an AUX port and it sounds even worse. I tried the MC input of the C162 thinking at worst id over drive but this sounded even worse and quieter than the MM input.

The cartridge appears to want a 47kohm load but this seems very typical, what am i doing wrong ??? I cant believe i have three faulty input stages and i also cant believe that a brand new cartridge gave up the ghost at the same time I swapped pre amps.

Alan

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Re: Analog problem

Sorry Alan, but I think it's your NAD's phono stage. Can you borrow a separate phono stage to run through the NAD's line stage? That would prove the NAD is at fault.

Is the Quad still around? If so, run its line-out into the NAD's line stage to confirm the problem.

Hopefully you've got a warranty on the NAD.

Dave

Welshsox
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Re: Analog problem

Dave

I did try a seperate phone stage and it was also poor.

I think theres some form of mismatch going on, just dont know where

Alan

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Re: Analog problem

You ran the separate phono stage through the line stage of the NAD and it was still bad??? Have you tried different cables? Did you make sure your cartridge is still intact and still wired securely? Sounds like there's something wrong upstream of the phono preamp.

One other test, does CD sound good through the same line-level input? If so, then the NAD is ok and you need to look upstream.

Dave

Jan Vigne
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Re: Analog problem

Kind of sounds like there's no stylus left on the cartridge. Re-install the Quad if possible to confirm correct operation of the cartridge.

Welshsox
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Re: Analog problem

Ive tried several things now, it does just seem as if the phono stage of the preamp or of a cambridge audio phone amp ive got are doing the job. There is reasonable sound just nowhere the dynamics and overall gain that you would expect.

Can you get a step up device to boost the cartridge output before it gets to the premap ? do they do transformers specifically for this purpose ?

Alan

Buddha
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Re: Analog problem

Art Dudley has covered this topic exquisitely in his columns.

Pull out your old issues.

If you don't have those, are they linkable online?

Welshsox
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Re: Analog problem

Buddha

Do you know which issues ?

To be honest i only keep a few months worth, i throw away magazines after that

Alan

Buddha
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Re: Analog problem

Since it seems like just a month or two ago, it must be from 2007.

I don't save mine, either. I subcribe to the notion of 'read and release.'

I do recall his thoughts stretched over a couple of issues or so, and he covered many models.

I hope a more avid hoarder than myself can help us out!

smejias
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Re: Analog problem


Quote:
Since it seems like just a month or two ago, it must be from 2007.

You are right, Buddha. Art's awesome columns on step-up transformers are here and here. And he made more comparisons here.

Jan Vigne
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Re: Analog problem


Quote:
Can you get a step up device to boost the cartridge output before it gets to the premap ? do they do transformers specifically for this purpose ?

If your cartridge is capable of 3.4mV of output, you do not require a step up device. Besides, step up devices are used for low output moving coils (usually about 1.0mV or lower) and not for moving magnets. No transformers either. No need to shuffle through old Stereophile's unless you just get frustrated one night and want to take a break.

3.4mV should drive any mm phono input to reasonable levels. This is not the high end of cartridge output levels but it is certainly not the low end of mm's or even high output mc's - both of which should work without problem into a well designed mm phono section. It's quite possible the Quad had a higher sensitivity and/or gain and/or different volume control taper than your NAD and you are too concerned about the disparity between where you set your volume control on the Quad vs the NAD - but that would not logically account for the distortion you claim to hear. Do I have that right? You are hearing distortion? Or you are just concerned about the setting of the vc? If there's no distortion, we are on the way to solving the problem.

If it is just that you need to raise the NAD's volume control to a higher level, that should be considered normal. As I indicated all volume controls have a taper that determines the amount of voltage through the control at various positions. A log taper or audio taper will typically allow more voltage at a lower position than a linear taper. So you would set the vc higher for the same final output level with one type of taper vs. another. This higher position/level set would be fairly consistent over all inputs if the issue resides with the volume control. How are the other source's levels compared to the phono's? Are you needing to set the vc slightly higher for all inputs?

Gain from a phono and/or line stage also varies from pre amp to pre amp and the NAD might not have as much overall gain as the Quad. You should be able to compare specs between the products for this determination.

3.4mV is still a healthy amount of voltage output from a cartridge and unless you are experiencing other problems, the position of the vc shouldn't be a concern. If you cannot achieve full power from your amplifier, then you would have other things to discuss.

On to "dynamics". I don't know exactly what to say since I cannot make a comparison for myself. The way to make a decision here is to think logically as each component is substituted for the other. If the dynamics are restricted with the NAD and Cambridge but not the Quad while all else other than vc position remains equal, I would tend toward thinking the Quad has the more dynamic phono stage. This probably isn't what you wanted to hear, but logically that would be my conclusion.

If you still have the Quad, or use the Cambridge, run it from the tape out of the Quad and go into the tape monitor inputs of the NAD rather than the AUX in. What results do you get then?

You described the sound in your first post as "pathetic". Is this just the lack of dynamics you are describing? Has anything else at all changed between the time you removed the Quad and added the NAD? Anything at all? Did you move the table? Have you inspected the cartridge to make certain there is a complete stylus assembly? Do I have it right that you had the cartridge for a while with the Quad before you made the switch to the NAD?

Welshsox
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Re: Analog problem

Hi

The issue does appear to be one of gain.

I just cant get enough gain from any combo to match the dynamics and volume of the Quad. Im using the phone section of teh Nad with a 12dB variable gain preamp out and then im using the variable pre in on the power amp with another 12 db of gain !!

The sound itself is OK but im still driving volume pot to hard and I cant help but think im losing dynamic range.

Does anyone know of a really dynamic high gain phone stage that is not really expensive ?

Thanks

Alan

Jan Vigne
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Re: Analog problem

I therefore assume the sound is not distorted and the problem is nothing more than where the vc position resides for a given output level. If that's the case, the solution is simple.

Ignore where the vc is positioned, its position is relative only to what you have grown accustomed to using.

Once again, not what you wish to hear but probably the correct advice. The vc is nothing more than a faucet that can only step down the amount of voltage through the circuit. At full rotation of the vc it is out of the curcuit (so to speak) and you have the full output of the phono stage. At anything less than full rotation you are cutting back on the voltage and therefore affecting the signal to some extent. Volume controls tend to sound best at their higher positions than at, say, a 9 O'Clock position. Be happy you can advance the vc into its most linear range.

The gain controls on your amplifier operate in a similar fashion. By cutting back on a gain setting you are actually imposing a restriction on the signal. Running the system with all levels at or close to their maximum position is far better than running with everything shut down to minimum levels. When you wish to make volume adjustments you now have subtle control over the range of the volume pot not available to someone with too much signal.

If the sound is "OK", you aren't loosing dynamics just because you have to advance the vc a bit farther than on the Quad. I know you have the impression of insufficient output levels with the vc advanced beyond 12 O'Clock but this is purely a matter of how you have been trained by manufacturers who use an audio taper vc where most of the gain is into the circuit by the time the pot reaches 10 O'Clock and then you have nothing much left above that position and clipping sets in by 1 O'Clock. Such a control is meant to sell on the showroom floor rather than be useful in your home.

If you can drive the system to acceptable listening levels with all of your LP's, you have nothing wrong with your system. It will take awhile to adjust to but you have a system that is better balanced than most. You don't need to buy anything else for this phono system. If you did, the better alternative would be a higher ouptut cartridge rather than a higher gain pre amp. Higher gain from a circuit always risks the possibility of higher noise along with the additional gain. But, just as with amplifiers, you will need to double your ouput voltage before you actually realize a somewhat noticeable change in level for the same vc position. There aren't many 7 Volt cartridges around today.

If you haevn't tried the tape monitor input yet, do so. There might be a slight change in input sensitivity between it and the AUX IN which feeds to the line stage with its typically more complex circuitry.

Welshsox
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Re: Analog problem

Jan

Thanks for the help

Ive been trying and listening

You are correct in saying that there are no faults on the system, the issue is strictly one of gain and a change in dynamics.

The NAD amps do have pretty sophisticated gain controls and I have variable gain output on the pre and input on the power. I can use these but im sure that by using two variable stages instead of fixed i will as you stated lose quality. The issue is that the Quad appears in hindsight to have a very high gain dynamic phono stage, it just wasnt working on other areas for me.

So what i think the answer is long term is to find a high gain dymanic sounding phono stage that i can run into a line imput on the Pre, this will be used for my good setup and then I can use the phono section of the pre for my casual falling sleep TT.

In case i didnt make it clear earlier I have a Marantz TT15 with Clearaudio for serious listening and a Thorens TD240 automatic ( lazy ass i know ) for falling asleep stuff.

Appreciate any recommendations for an economical but dynamic phone stage

Thanks

Alan

Jan Vigne
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Re: Analog problem

Sorry, I really don't have any comments about phono stages. I haven't been looking for a phono stage for decades so I'm unaware of what's likely to suit your requirements in today's market and I doubt recommending a McIntosh C22 would fit into your scheme.

As always I would set a budget, review the Recommended Components listings and go from there. What the RC listings don't show, however, are the small internet only manufacturers and the "cult status" products that aren't often reviewed by the major magazines. These products can offer some high value performance and typically have the advantage of a trial period. I wouldn't ignore those products but I realize they are more difficult to assess without personal experience.

Good luck.

Buddha
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Re: Analog problem

Not being argumentative here, but do invest the 15 minutes it takes to read Art Dudley's columns about the transformers.

Some are at a much lower cost than a new phono preamp, and may really address your desire for more dynamism.

Jan Vigne
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Re: Analog problem

But you don't want to use a transformer with a moving magnet cartridge. I'm unaware of a transformer that would offer the correct input loading for a mm cartridge since there's no need for such a device. While mm's are not sympathetic to even fairly large variations in impedance loading, a change from the required 47kOhms to 100 Ohms would be outside the limits of what any mm cartridge expects to see. With improper cartridge loading frequency response and dynamics will be altered, and the alteration is usually not in a good way but certainly would be in an unpredictable way.

If a separate phono stage is considered, one with variable capacitive loading would be the correct choice. Though once again mm's tend to operate well into a wide range of capacitive loadings in a typical mmphono stage. If either the NAD or the Cambridge phono sections offer such optional loadings, it is possible you could alter the sound of your present set up enough to satisfy your desires.

http://www.soundfountain.com/amb/ttcartridge.html

http://www.extremephono.com/Loading.htm

Buddha
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Re: Analog problem

Excellent points, sir!

Jan Vigne
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Re: Analog problem

Alan, I don't want to get into a discussion of the various merits and downsides of any one product, but have you considered the NAD realy might be the problem? My experience with NAD products suggests to me they are not known for their reality based dynamic range. Compared to "better" products they lack the leading and trailing edges of notes IMO. Plugging any outboard phono section into the NAD will still result in what would be a mostly NAD influenced sound.

Welshsox
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Re: Analog problem

Jan

Thanks, your comments are very constructive and im more than happy to listen to thoughts on equipment, either positive or negative. I do agree that I might have taken a step back with the Nad in this area, I just wasnt getting along that well with the Quad's and decided just to experiment a little.

I think a new phono stage might be the answer

Alan

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