New man has trouble with volume and hum

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New man has trouble with volume and hum

Postby Andy Parrett » Mon Mar 17, 2008 10:58 pm

Just got started and I've gone successfully through from start to CD, but I have 2 queries, and whilst the volume one has been discussed here before, I don't feel confident (as a 'plug and play' sort of person) that I've got an answer from it.
ie 1) My line-in volume level is set at zero, yet I still get 'overload'. Not all the time, but there's no latitude at all in the vol. control. Should I get a pre-amp with a vol. control? (The one I bought - £15 - said it was designed specifically for the purpose I'm using it) If so, I'm puzzled that the only one I can find on the web means ordering from the USA (www.phonopreamps.com) - not, of course that that's a serious problem as they are supplied for 240v. Should I alternatively (or additionally) buy the soundcard people are generally recommending - the Audiophile 2496 (the one I have is whatever came with this Dell PC - it says 'SoundMAX digital audio')

Q2) I'm getting hum which shows up at between -18 and -25 on the WC volume meters (greater when I have my main amp switched on for the purpose of connecting the earth from the turntable - do I need to do this?). Apart from the hum sound itself, it means that WC can't find any breaks between tracks and I've put them in manually. How can I get rid of it? (Is it the pre-amp again - I've tried 2 different turntables)

Any advice gratefully received!

Andy
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Postby Glenn » Tue Mar 18, 2008 12:53 am

Hi Andy;

I'm not sure how you would be getting any signal into your soundcard if the line-in volume is set to zero. Isn't that the same as mute? More than likely somebody else will have a better explanation. I don't think it matters which card you use; the 2496 is a good card and it might solve your problem, but you're really splitting hairs in terms of sonic performance.

As for the hum, it is usually caused by either the absence of a ground path or by too many. Have you tried lifting the table's ground lead from the amp and connecting it to the preamp? A simpler approach if it's available is to connect the soundcard line-in to the amp's monitor loop (line out). If your table is connected to it then presumably it already has a phono stage.

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Postby Andy Parrett » Wed Mar 19, 2008 7:00 pm

Thanks for your reply, Glenn. Nope, it's not the same as mute! I've got the volume slider all the way to the bottom and the sound's coming through to the WC meters as previously described.

Regret I don't understand your last couple of sentences, but anyway, is there any reason why I shouldn't connect the earth/ground to the earth/ground pin in the turntable's plug and simply stick that in the wall socket, as we normally do for appliances anyway? (I do appreciate that you're in Canada, and things may be different there.) BTW the preamp just has in/out phonos, no place for hooking on an earth wire.

Andy
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Postby Ray Bell » Wed Mar 19, 2008 10:08 pm

Hi Andy

The problem with connecting to the earth pin of the turntable's mains plug is the possibility of creating an 'earth loop' otherwise known as a 'ground loop' or 'hum loop'. (Correct earthing is one of the banes of any low signal level electronic designer's life.) If you create a loop of ground connections stray magnetic fields, usually from a mains transformer will cause current (at the mains frequency 50 or 60 Hz and its harmonics) to flow around this loop and this can result in hum being added to your signal. The traditional strategy for turntables was to connect the earth wire to an earth point on the amplifier so that the turntable earth was through the same path as the amplifier earth and no loop was formed. These days many pieces of electrical equipment are not earthed (but double insulated) and the situation may be different. I suspect this may be the case with your preamp. You may need to experiment with grounding configurations to find one which works, e.g. connecting to earthed metalwork on the pc although this may give other problems.

With regard to your volume issue firstly are you sure you have plugged in to the line in not mic in? Secondly are you adjusting the record level or the playback level in the windows volume control?

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Postby Glenn » Thu Mar 20, 2008 1:38 am

Hi Andy; yes ground loops can be problematic.

Regret I don't understand your last couple of sentences...


To clarify:

Assuming I understand you, you already have your table connected to a stereo, which has a built-in phono preamp. Why not use this to supply signal to the pc, instead of a dedicated preamp? Most stereos have some means to connect a tape recorder to record/playback. Over here we call it a 'monitor loop'; it could be called 'tape-out', 'line-out' or 'signal out'. The point is, if your table and it's ground are both already connected to the stereo, a hum-free signal can be taken from it through the stereo's 'line-out'. This is exactly the same as if you were using your pc as a tape recorder.

If the 'line-in' level control on your soundcard is not working, check to see if there is a 'master' record level control that does the trick.

Glenn
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Postby Derek » Thu Mar 20, 2008 10:30 am

Yes, I would reiterate what Glenn says. Also, you need to describe how you are interconnecting your equipment in order for us to find the solution to the problem. For example, you may be going through two pre-amplifiers; this would explain why the signal is too high. What turntable are you using and what type of pickup cartridge?

If you provide as much information as possible about your equipment, there's a good chance that we can find a solution.

good luck
Derek Higgins
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Postby Andy Parrett » Thu Mar 20, 2008 8:47 pm

Gentlemen
Thank you for your help. So let's have a rundown of equipment:
Turntable: Dual 505 with OrtofonVMS2E stylus. I'm assured there's no pre-amp inside this item.
Regular amp, only there (but switched on) for earth connection from t/table: Harmon/Kardon PM640
Pre-amp just purchased from Hayley at www.turntablestylus.co.uk It came with a phono to jack adapter just like the one in the picture in your instructions, Derek. Tech data: Input impedance 50k Output ditto, Gain: 34dB, Max. input 1.8V rms, S/N ratio 50db (none of this means anything to me). It is mains powered, has no place to attach earth from t/table, just in and out phono sockets. Computer is a regular Dell desktop pc with Intel celeron processor, and Windows 2000pro/Service pack4. On WC recording screen it says the device is MS Sound Mapper and on the Recording Control window (definitely line-in selected and slider bar on zero) it says SoundMAX Digital Audio.

So here I am: the turntable is connected to the preamp and the preamp goes to line-in at the back of the pc. Amplifier, preamp and t/table all have separate regular modern plugs (only the preamp has an earth wire to the plug) and all go through a multi-connector to the same wall-outlet.

As I sit here, playing no music, with headphones on, connected to the pc. The WC shows a recording level of about –18, reacting to a low-level hum, which from time to time is augmented by a higher buzz sound which comes and goes, pushing the level to approx –12

I can’t think of anything else right now.
Thanks again and I look forward to hearing from you again.
Andy
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Postby citguy » Fri Mar 21, 2008 6:11 am

http://www.harmankardon.com/product_sup ... p=&#active

Hi Andy. If you don't have a manual for the Harmon amp, go to the link above and download one. I assume you are using one of the "tape outputs" to connect to your sound card. The tape outputs are "line level' outputs or can not be controlled by the volume control on your amp. The tone controls do not affect the tape outputs. There is a provision for a ground wire from the turntable at the phono inputs. The volume and tone controls are for monitoring the recorded material you are running to your sound card.
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Postby Derek » Fri Mar 21, 2008 9:46 am

There are several things you can do to track down the source of the problem.

First completely disconnect the PM640; does this affect the hum?

Then, disconnect the turntable from the pre-amp; does this affect the hum?

Then, I would remove the pre-amp entirely form your set up; ie connect your turntable to the phone-in sockets of the PM640 and connect your computer to the tape-out sockets of the PM640; again how does this affect the hum?

Let us know how you get on.
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Postby Glenn » Fri Mar 21, 2008 4:22 pm

Hi Andy;

The link you provided above didn't reveal anything, but a search for 'hayley preamp' brought up the ebay site that retails the preamp you're using. First of all, I find the lack of a grounding post highly suspicious. I'm not aware of ANY record player setup that can be connected without a ground lead. My guess is this model is intended for a table that has the ground lead integral with the signal ground. So try this: Lift the phono ground from the HK (you shouldn't be using it for ground if you're not using it for signal, anyway) and touch it to the exposed metal sleeve of the rca jack on the preamp (this will effectively couple the 2 grounds). If this removes the hum, then you have 2 options: Either rig the preamp with a ground post, or buy a new preamp that comes with one (such as the Behringer PP400). If this doesn't work, then send it back to Lurch and stick with the HK tape-out connection; it's guaranteed to work.

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Postby citguy » Fri Mar 21, 2008 6:06 pm

Hi Glenn. The link I provided in the 2:11 pm message does work and allows a download of the manual for Andys Harmon. The Harmon does provide a ground connection for the turntable according to the manual.
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Postby Andy Parrett » Fri Mar 21, 2008 11:16 pm

Thank you, Stan, Glenn, Ray & Derek
I'll mull your ideas and suggestions over the weekend. As it's a public holiday on Monday in the UK - and I've taken Tuesday off as well, I should have time to sort this out!
Happy Easter!
Andy
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Postby Andy Parrett » Mon Mar 24, 2008 9:19 pm

Well, it looks as though the answer is simply to use the Harmon/Kardon amplifier!

As suggested, I have tried Turntable to phono on the amp and then tape-out to line-in on the computer. It worked fine with no hum at all, plus the volume problem was also improved. I have also connected my cassette tape unit to the amp (using the AUX sockets) and that has worked OK too (using the same amp to pc arrangement). I have produced two (to me) quite acceptable CDs as a result.

So what is the point of a separate pre-amp? Should that give a better quality signal in some way? I have found the Behringer PP400 and supplier - it's not at all expensive - but would it make any difference?

Otherwise, it seems to me that I just need an external hard drive for my computer (these files are big!) and some Avery labels for printing inserts for CD jewel cases.

Many thanks for your help.
Andy
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Postby Glenn » Mon Mar 24, 2008 10:42 pm

Hi Andy, glad you were able to sort things out.

So what is the point of a separate pre-amp?


That depends. The preamp in the HK is pretty decent to begin with so the only point to using a separate preamp will be for one of convenience; if the table is not being used to play music through your stereo then a dedicated phono stage will give better fidelity by means of a shorter signal path to the pc.

If the setup you have now is ok for you then there are better ways to improve the sound. Start by making sure the record is absolutely as clean as can be. I can't stress how important this is. Unless the record has never been played before, cleaning it properly is the cheapest upgrade one can make.

Have fun.

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Postby Andy Parrett » Tue Mar 25, 2008 8:28 pm

Glenn
Many thanks for that. It looks like I'll carry on using this HK amp - which seems OK although it is 24 years old! I'm not using it for anything else so it can be dedicated to this use.

Right then, cleaning records, what's your suggestion? I have an 'anti-static record cleaning cloth' bought over a decade ago (and the rest, probably!) used on only one side. Is that adequate? Otherwise?

I should probably get a new stylus for the deck don't you think? (Don't know if Ortofon is still in existence.)

Andy
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