Seduction hum, buzz and sound quality issues

[rebbi]

Hi, Guys,

I need some troubleshooting help with my Seduction preamp. Hope somebody can help me with this.

I have a Seduction preamp with the C4S upgrade. I've been using it for quite some time with no real issues. It feeds into a Manley Shrimp preamp, and that, in turn, drives a Bel Canto S300 amp. My TT is a SOTA Sapphire with an Ortofon 2M Blue cartridge.

I recently rearranged the physical layout of my gear as part of setting up a new pair of speakers (Merlin TSM-mmi's). And since doing so, I have been having the following issues.

There's a slight hum in the speakers when the electronics are fired up; this is only true when running the phono gear; the CD part of the rig is dead quiet. But when I turn on the motor on the turntable, a rather prominent buzzing noise crops up. I've tried moving some of the cables around, as well as relocating the outboard power transformer of the SOTA, but no luck.

How would I go about troubleshooting this?

I've also noticed that right now, my CD gear sounds better than my analogue gear - more alive and dynamic, if you will. I know that's vague... so right now, I'd settle for getting the buzzing issue sorted out.

Thanks in advance,

Steve

[Paul Joppa]

Sounds to me like a grounding issue with the phono cables and/or turntable internal wiring.

The simple test is to disconnect the phono cable at the Seduction and use shorting plugs at the Seduction input, then repeat the experiments. If the hum and buzz go away, then it's coming in from the turntable; otherwise there may be some other source.

Is everything, including the turntable, plugged into the same power outlet?

[rebbi]

Sounds to me like a grounding issue with the phono cables and/or turntable internal wiring.

The simple test is to disconnect the phono cable at the Seduction and use shorting plugs at the Seduction input, then repeat the experiments. If the hum and buzz go away, then it's coming in from the turntable; otherwise there may be some other source.

Is everything, including the turntable, plugged into the same power outlet?

Paul,

Thank you very much for the speedy reply. Excuse my ignorance, but what are shorting plugs?

Thank you,

Steve

[JC]

Although some recommend using resistance, I have always just used some cheap RCAs and shorted the center pin to the outside shell.

They are useful for inserting into the inputs of amplifiers in order to measure self-noise, among other things.

THEY SHOULD NEVER BE USED ON OUTPUTS!

[grufti]

In this case I am probably on the safe side with the following answer: take an old cheap RCA plug and solder a resistor from the center tab to ground. Good values for typical RCA inputs are about 5 kOhm. Plug those into your amp's inputs. Keep them around. They have many uses.

Paul,

Thank you very much for the speedy reply. Excuse my ignorance, but what are shorting plugs?

Thank you,

Steve

[Grainger49]

As PJ mentions you should check the placement of the Seduction.  The audio circuits of it are susceptible to pickup of hum from transformers or power supplies that are too close, but not its own The Seduction's transformer is well shielded).  So first if the Seduction is next to any other piece of equipment you should move it.  The hum field drops with the square of the distance so even a few inches can make a difference, a foot a huge difference.

The cabling from the turntable to the Seduction (the most sensitive) and from the Seduction to the preamp (less sensitive) are also prone to hum and buzz pickup.  So your routing should be changed next.

[Doc B.]

I think PJ's question of whether or not everything is plugged into the same outlet may well be the key, particularly when you mention the noise happening when you start the TT motor. If the Seduction and ttable are are in different outlets around the room try setting them up so they both run from the same power strip. If they are all in the same power strip, try using a cheater plug on the turntable motor power cord. You can also try connecting the turntable/motor chassis to the Seduction ground post

[rebbi]

I think PJ's question of whether or not everything is plugged into the same outlet may well be the key, particularly when you mention the noise happening when you start the TT motor. If the Seduction and ttable are are in different outlets around the room try setting them up so they both run from the same power strip. If they are all in the same power strip, try using a cheater plug on the turntable motor power cord. You can also try connecting the turntable/motor chassis to the Seduction ground post

I will check all this out when I get home -- I'm at work now. I think it's all in the same surge protector strip, but I'll check. IIRC, the SOTA TT power transformer has only a two-pronged plug. And I do have the ground wire from the TT attached to the ground post on the Seduction.

Thanks, everybody,

Steve

[Grainger49]

I'm pulling Carl's problem from rebbi's thread and posting here:

http://www.bottlehead.com/smf/index.php/topic,1512.msg10931.html#msg10931

I have finished it now.  I will delete the posts here to clean up the confusion.  Well, I'm confused.

[rebbi]

As the original poster from last July, I still haven't managed to sort out this hum/buzz issue. I even took my Seduction to Austin Stereo Service here and Mike, the owner, resoldered a lot of my -- ahem! -- less than lovely solder joints. No difference... the hum's still there.

Like the other poster here, I notice that the hum gets worse if I, for example, touch the tone arm on my SOTA Sapphire.

I still haven't had the chance to make shorting plugs to ascertain if the hum is somehow coming from the Seduction itself.

All in all this is very frustrating!  :-/

Steve

[dstrimbu]

Steve,

You gotta try shorting the inputs of the Seduction.  That's the only way to isolate the noise source.  Paul mentioned this back in July.  If the hum goes away with the shorting plugs in the Seduction inputs, you will have eliminated everything downstream of the Seduction's inputs from "blame".

Please don't just assume that, just because you built the Seduction, it's at fault... (even though I know that I would do that :-) ).  Since this problem started after you moved your equipment, I'm thinking that it's a turntable issue... because the turntable is the most delicate piece in the chain, for sure.

The Sapphire has an AC motor.  There's a ground issue somewhere in the signal chain, and I'm wondering if something hasn't gone awry with the wiring in the tonearm...  the hum increasing in volume when you touch the tonearm could be pointing to this.

I would recommend making up a set of shorting plugs (maybe you can borrow some from Mike at Austin SS?).  If the problem goes away, I'd start looking at the interconnects from the Sota to the Seduction, then the tonearm / headshell / cartridge.

Been too long, man.  Need to get this fixed... music is life!  :-)

-Don

[Paul Joppa]

As the original poster from last July, I still haven't managed to sort out this hum/buzz issue.
...
All in all this is very frustrating!  :-/

Man, that just sums up hum and buzz issues!

I encourage everyone to never give up though. There is almost always an answer, and it pretty often taken an inordinate amount of trying to find it. Take a break when you have to, but keep coming back to it - this forum has found some pretty amazing solutions to seemingly intractable problems.

OK, if touching the tonearm increases hum, and if the tonearm is properly grounded to the Seduction chassis, then it's logical that touching the Seduction chassis would increase hum. Does it?

[rebbi]

Steve,

You gotta try shorting the inputs of the Seduction.  That's the only way to isolate the noise source.  Paul mentioned this back in July.  If the hum goes away with the shorting plugs in the Seduction inputs, you will have eliminated everything downstream of the Seduction's inputs from "blame".

Please don't just assume that, just because you built the Seduction, it's at fault... (even though I know that I would do that :-) ).  Since this problem started after you moved your equipment, I'm thinking that it's a turntable issue... because the turntable is the most delicate piece in the chain, for sure.

The Sapphire has an AC motor.  There's a ground issue somewhere in the signal chain, and I'm wondering if something hasn't gone awry with the wiring in the tonearm...  the hum increasing in volume when you touch the tonearm could be pointing to this.

I would recommend making up a set of shorting plugs (maybe you can borrow some from Mike at Austin SS?).  If the problem goes away, I'd start looking at the interconnects from the Sota to the Seduction, then the tonearm / headshell / cartridge.

Been too long, man.  Need to get this fixed... music is life!  :-)

-Don

Okay, I will try the shorting plug thing tomorrow and report back. I would really like to get this sorted out so I can enjoy my TT again.

[Grainger49]

Steve,

You have been wrestling with this for quite a while.  Let's start eliminating components and arrangements so you can get rid of the hum.

[rebbi]

Steve,

You have been wrestling with this for quite a while.  Let's start eliminating components and arrangements so you can get rid of the hum.

Can I just solder the cut wire coming out of an RCA plug onto the outer collar of the plug to make a shorting plug? Fry's doesn't have any bare, male RCA plugs in stock.

Steve