Carl's Seduction Hum Buzz Problem

[Grainger49]

Moving Carl's problem from Rebbi's thread.  There is editing and combining of posts:

Hello,

I have a very similar problem to the one described [by rebbi].  My issue is the buzz occurs or is noticeable only when I have the volume turned high.  I have always had to open the volume on the Foreplay to 3 0'clock if not all the way, which is about 5 o'clock when using the Turntable.  

I noticed that with no record playing or the motor on,  if I lift and rotate the tonearm towards the center of the table (as if to play a record) the buzz gets significantly louder.   Any ideas how to approach identifying and fixing this issue? [this resolved below] . . .  

Another post:

I'm using a Clearaudio "Emotion" table.  There is a ground wire running from the tonearm and another ground running out from under the center spindle.  On a hunch I decided to remove the one wire under the center spindle but kept the one from the tonearm attached to the Seduction ground post.   MAJOR improvement!!!  Hum subsided about 50-75% from where it was before.   Also,  there is now little or no reaction when I move the arm towards the platter.   Am I on the right track?  Seems so but I want some more feedback and thoughts if possible.  Why is there a ground off this center spindle to begin with?  It's not attached to the tonearm or motor so why would it need to be grounded?

I've been living with this issue for years and just now addressing....go figure : )

Another post:  

I'm now only able to discern a hum (sorta microphonic sounding) when at the highest setting on my Foreplay (without music playing).  There is no difference when the motor is either on or off.  I detect only the slightest change in hum now when  i move the tonearm towards the center (i.e. closer to to the motor which is in the back left corner of the table).  Only grounding now has the tonearm to the Seduction.....is this incorrect meaning I still need the grounding I removed from the center spindle?

When you say silent should it be the same silence I hear when set to a cd player without any music playing? because I have not achieved this quite yet.

Thanks,

Carl

So far Carl has removed the ground from the center spindle to the Seduction and it reduces hum a lot.  That isn't an issue, leave it that way.

Carl reports that the hum no longer increases as the arm moves toward the center/motor.  There is no difference in noise with the motor on or off.

The Seduction and TT are on one dedicated outlet and Foreplay and Dynaco [we should find out what model] on another dedicated outlet.

The noise is only audible from the listening position when no music is playing.

The ground lug on the Seduction is properly attached to the Seduction top plate.

The TT AC plug is grounded and attaches to the motor/switch only, it doesn't even touch the table.  So there is no connection between the TT motor and AC and the TT.

I mentioned this about the two dedicated outlets:
If the two outlets are from opposite phases of your incoming power it can produce noise.  (In my service panel the breakers on each side of the panel are on alternating phases.  That means if they are above and below each other they are probably on opposite phases.)  Try an outlet strip on the same dedicated outlet as the rest of the system.  If indeed the second outlet is on the opposite phase of the incoming power then it would be great isolation for all digital devices.  That is what I have done in my system for analog and digital devices.

A couple of questions still need to be answered:

Have you tried different a different TT, tubes, interconnects, a separate ground wire?

You say you have buzz rather than hum.  That can be a power supply noise.  If you haven't had the noise before try rewetting the solder joints on the diodes.

Paul Joppa asked:  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?

[Grainger49]

It sounds like you have beat down most of the noise.  Good!

I understand now your Seduction and FP 2 are running much like my Seduction and FP 2.  I run at 3:00 to 5:00 because of the low gain in my system [I have 76 drivers on my amp lowering the gain there] and my speakers.

At some point you said you could use a little more gain.  Do you have the C4S in your Seduction?  It gives 6dB gain if I have it right.  It also lowers and isolates power supply noise.

I suggested you try putting the TT and Seduction on the main stereo outlet.  It might help, might not but is worth a try.

Which Dynaco amp are you using?  If it is a ST-70 does it have the stock driver circuit board, just two small tubes on the circuit board in the middle?  If yes to both there is a resistor you should try jumping around.

From Paul Joppa concerning this problem:

My memory is not that good but I do recall that early Foreplays did not have the signal ground attached to the chassis. Making that connection (T13 to T14) reduced hum and buzz in many cases.

I know the earliest Foreplays had 2-wire power cords; I do recommend a 3-wire cord with the ground lead taken to the chassis close to where the power cord comes in. The UL standard is for that ground lead to be the longest, so that if the power cord is ripped out of the preamp by brute force, the ground wire will be the last one to disconnect.

[choff]

I do have the CS4 running in my Seduction.  Have not tried the moving the plugs to the main stereo outlet but will try that.

I do have a Dynaco St-70 with the original circuit board.  What resistor change do you suggest? 

thanks,
Carl

[Grainger49]

Probably the first thing to do is try Paul Joppa's suggestion.  Use a jumper and connect terminals 13 and 14.  Most of the time that lowers noise.  In very rare cases it increases.  Jumpers can be had at Radio Shack.  They are short pieces of wire with an alligator clip on each end.  They are handy for all kinds of things in the hobby.  For instance below.

I have found that the stock ST-70 driver board can cause noise since the "ground" of the incoming signal goes through a 10 ohm resistor before getting to ground.  Use a jumper to jump around each of them.  I'll do a little research to find just where on the board they are.  Just put a jumper on each of the wires going into the body of the 10 ohm resistors.  It grounds the input circuit.

Your ST-70 can also get a grounded power cord.  It is a safe thing to do.  If the high voltage shorts to the chassis it will blow the fuse.  With no chassis ground it can kill you.

[choff]

I have in fact installed a grounded cord on the ST-70.  I may have done the jumper on the Foreplay but will have to check.  I think I just solder wire between these two terminals.

Incidentally,  I have noticed that one of the tubes on my Foreplay always glows less than the other.  This is true regardless of what tube I insert in this channel (left side).  I seem to get some sputtering out of this channel as well. 

[Grainger49]

Carl,

Then you have all the gain that the Seduction can give you.  Is your cartridge at least 2.5mV?  I have added a dropping resistor for two inputs.  If I get confused and put the Seduction on one of those it doesn't play loudly enough for me either.  Is there a possibility you have padded an input or two?

Each tube glows as much as it wants, it is individual.  What matters is how much voltage you have on the heaters.  Check between tube pins A9 and A4, between B9 and B4.  Both should be about 6.3V AC for a FP 2.  The FP 1 had been retired by 2002 when you bought yours.

Reseating your tubes cleans the pins on the tubes and the socket too.  Try reseating them 6 times to make sure there is no oxidation on either the pins or the socket.

You have a PM.

[choff]

Since my last post I have noticed that the hum problem seems to come a go.  When I do hear the hum it sticks around for a listening session.  Next time I turn on the system it will have vanished???   Sounds like I may have trouble on the electrical lines perhaps??  feed to the hose being inconsistent or something??

[Grainger49]

The Seduction has good filtering in it.  The power supply includes the RRSF, Reverse Recovery Spike Filter, and the heaters include three 1uF caps at each socket.  The C4S isolates the power supply from both tubes. 

If something is injecting noise into your Seduction it would have to be bad noise or a large electrical device. 

I would suspect a connection that is loose and intermittant.  Is the noise now in both channels?

Have you performed the checks in reply #5 above?

[Grainger49]

Carl,

Haven't heard back.

[choff]

Sorry.  I need to take the system apart to do the checks.  As it's set-up, doing this is a bit awkward and time consuming.  I also have an upgrade to apply to the Foreplay I have been meaning to do for about eight or nine years.  It's the Anticipation mod which I bought when I bought the kit.  Hope to do this within the next month.  What can I expect from this change?

[Grainger49]

Gave me a chuckle.  I have the Anticipation boards too, assembled, and haven't put them in.  I changed the output caps in my FP 2 and now have room, maybe.  I have had them since about 2002.  Just assembled a few months ago.  I like the sound of my system so well that I haven't felt any pressure to put the boards in.  I know I will like them, just haven't done it.

I also have some huge caps to put as the final stage that won't fit inside.  But that will happen with time too.

[choff]

Hum problem went away when I installed my new Clearauio "Virtuoso" cartridge!!!   guess the old one was defective in some way.   thanks for everyone's help.

Carl