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Groovewatt - tube RIAA phono preamp
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Author:  Geek [ 01 Feb 2018, 00:50 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

Rega's can have issues with certain cartridges, esp. Grado. Audio Technica or Nagoka are usually the ones we pair with them.

If it's not the cartridge, then the issue of them tying the ground to one of the RCA shields can wreak havoc in setups.

Cheers!

Author:  coaltrain [ 01 Feb 2018, 00:59 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

It is the standard Carbon Cartridge that comes with the player. I was surprised to find there wasn't a ground and they way Rega chose to do this. Is the noise getting dropped on my signal ground in the Groovewatt and then causing the hum?

Author:  Geek [ 01 Feb 2018, 06:01 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

Not sure specifically about the Groovewatt, but it definately doesn't play nice with certain phono stages.

I actually do quite a bit of mods on Rega's out-of-the-box to split that ground into a real one. Not for the faint of heart and one mis-step will have you rewiring the entire tonearm, but it can be done!

Unless you were an expert at the game of "Operation" as a kid, I'd suggest maybe trying another table (if for no other reason to rule out the phono stage as the issue) if you want to use the Groovewatt ;)

Author:  gofar99 [ 01 Feb 2018, 08:53 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

Hi, I suspect that you are running into a ground loop. The Groove works fine with nearly any cartridge/tonearm/turntable. I have not encountered any that did not work well (I have 6 turntables and about 20 cartridges plus lots of feed back from other users)...but there are always exceptions. I thought I would encounter problems with an OM30...but didn't. It has the right ground connected to the "chassis/case" ground. All my turntables have separate chassis/case grounds that are separated from the signal grounds. I believe in you case what I would try is use a separate ground wire from the chassis/case and do something like what is used in pro audio gear to make a ground break. Leave the cartridge alone. There are two ways I would try. One do like I do in most of my gear and put a 120-150 ohm resistor in series with the new ground wire (that goes between the chassis/case of the TT to the preamp ground) and put a 0.1uf poly cap in parallel with the resistor. The alternative is to replace the resistor and cap with a pair of rectifier diodes in parallel with one facing each way. Both methods are common in pro gear to isolate / but not really isolate two different pieces of gear. I would not initially worry about the ratings on the parts...just try them and see. Please let us know if this works as it may be a good tip to pass on. Another possibility with that turntable and cartridge (I own neither) is that the cartridge is picking up the turntable motor. That can be helped with a thin piece of Mu metal shielding under the platter stuck to the plinth. This sort of hum usually intensifies as the arm is moved toward the center of the platter. If this fits your situation let us know and I will provide details on the shielding.

Good listening
Bruce

Author:  coaltrain [ 06 Feb 2018, 15:43 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

The noise does not change with movement of the arm, or turning the turntable off. A different TT was quiet so must be the Rega.
The noise does go away when the turntable is unplugged from the Groovewatt phono preamp so the way Rega has the TT wired must not be playing nice.
I looked into the Rega arm grounding and schematics online and I think I would have to separate the ground from the signal ground and add a real ground as Geek implies. I am a surgeon so I have steady hands (also did 3 years as electrical engineer 30+ years ago before a changed my major) so I would be interested in any tips how to add a real ground to the Rega without destroying the tonearm.
Thanks, Chace

Author:  coaltrain [ 06 Feb 2018, 22:45 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

coaltrain wrote:
The noise does not change with movement of the arm, or turning the turntable off. A different TT was quiet so must be the Rega.
The noise does go away when the turntable is unplugged from the Groovewatt phono preamp so the way Rega has the TT wired must not be playing nice.
I looked into the Rega arm grounding and schematics online and I think I would have to separate the ground from the signal ground and add a real ground as Geek implies. I am a surgeon so I have steady hands (also did 3 years as electrical engineer 30+ years ago before a changed my major) so I would be interested in any tips how to add a real ground to the Rega without destroying the tonearm.
Thanks, Chace


To try Bruce's suggestion I think I need a "real earth" ground on the TT to tie to other than the signal ground??

Author:  gofar99 [ 07 Feb 2018, 13:47 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

To add a "real" ground to something like a turntable can be either easy or nearly impossible. I have run into both situations. The idea is to connect the primary metal parts together and then run a wire from them to the phono preamp case or your main preamp ground terminal. The first thing I would do is use a meter and check the resistance between the main metal parts of the turntable and the signal lead grounds (shields on RCA connectors usually). If it shows nearly zero then you will probably need to find out where the two are joined. I would then separate the connection. Run a wire from the part not connected to the signal cable shields for your new ground wire. I find that nearly all turntables have plenty of screws inside that you can attach a wire to. Be careful though when you loosen one up that it is not a bolt and you will have difficulty in re-tightening it or worse some part will fall off or get out of alignment . If you desire, you can post the question on how to do this on the vinylengine.com forums. You will need to register first though. There are many users and it is a friendly site. Someone has probably done what you need to do and can give specifics on it.

Good listening
Bruce

Author:  laurie54 [ 07 Feb 2018, 15:09 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

Well Bruce you have done it again. I find myself laughing out loud at the nut that, when undone lets (something ) fall off inside and then the fun starts. It doesn't happen often but the inside tinkle of the other end of some screw or worst (springs) falling off inside is almost like a right of passage into the world of tinkering. Thank you for that.

Author:  gofar99 [ 07 Feb 2018, 16:41 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

Hi, I'm glad to have provided some mirth. As like most other serious diyers .....I have had small parts fall off inside things. Like you observed....that nearly inaudible "tinkle" inside a device is often the signal that you are in for serious trouble. :eek:

Good listening
Bruce

Author:  laurie54 [ 07 Feb 2018, 23:54 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

Been there, done that. lol Good tinkering! Just so good to know we are not alone in such instances. Thanks again.

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