Foreplay II : anticipation upgrade - check out problem

[Grainger49]

Each RCA connection, male and female, has an outer conductor which is called ground, shell or outer conductor.  This is the part of an RCA plug that you can grasp.  There is also a center conductor that is called hot or center conductor.  This is the pin that goes into the hole of the RCA jack.  Since audio signals are AC part of this is a bit of a misnomer.  The outer, shield, ground is most often grounded, but not always.  The inner is the signal which is "hot" relative to ground but in actuality it swings positive and negative around ground.

It sounds like tube rush, a noise that can sound like white noise, a sleep machine, to a low frequency rrrrrr kind of noise.  The best way to check the ST-70 is to use shorting plugs on it, or just use jumpers to short the input RCA jacks.  That tells you the minimum noise produced by the ST-70.  The same for the FP 2 and Seduction; short the input and listen.

Since each C4S board only has 3 wires you can easily re-wet each of the terminations just to assure yourself on those.

[Doc B.]

The upgrade increases the gain slightly and therefore increases what from your description sounds like tube rush coming from upstream. The Stereo 70/Foreplay I/II combo has been pretty well documented as having a ton of gain that emphasizes the noise floor of the tubes in the source and preamp, and usually the easiest solution is a couple of in line attenuators between the FP and the ST70. Parts Express sells them. A search on the forum archive will turn up a fair amount of discussion about these attenuators.

[choff]

Thanks guys.  Without question there is a bunch of additional gain in the system now after this upgrade.  Probably 2 clicks worth on the sweet whispers.  Thought it odd that the noise I hear is not affected at all by the position of the pots?  It's just very consistent.  Air and a tiny buzz noise like a bee would make (or tubes i guess in this case).  Really not noticeable during playback except for very quite passages it can be annoying and when switching out music.

I'll check into the attenuators you mention.  Did I mention this is one awesome upgrade?  Feel like I just got a whole new stereo system. Thank you Doc!!  Got to love the fact that it only took me 10 years to sit down and finally get it done : )

[choff]

any thought on the DB reduction factor I should chose as they seem to come in 3, 6 or 12 db : http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=725

also,  I would attach this to the output end of the Foreplay or the input of the Dynaco.....or does it matter?

[Doc B.]

The noise comes into the circuit mostly from after the Sweet Whispers, so the volume control won't change the noise level. That's why an inline attenuator to cut the high gain of the Stereo 70 is the best approach. The "air" is tube rush and that might change a bit with different tubes in the FP. The buzz is ground loop noise and that could be due to the terminal 13/14 thing mentioned by Grainger, cables or cable connections that are less than perfect, ground loops between the preamp and amp, light dimmers, or a whole bunch of other less likely sources.

If you still have four or more clicks left at the high end of the attenuator range when listening at average levels I'd suggest the 12dB, which will have the strongest effect on lowering the noise. If you are listening with the attenuator higher than that try the 6dB attenuators. Put them right at the input of the amp.

[choff]

Thank you.  That really helps me understand the issue much better and arms me with some ways to correct it.   Cheers!!

Carl

[Paul Joppa]

OK, that helps. The ST-70 is notoriously sensitive, and the relatively high gain of the Foreplay is not a good match. Best bet is usually to reduce the ST-70 input sensitivity; that will reduce the FP hiss and hum, and cure the hair-trigger volume controls you probably also have.

Hopefully some one of the many FP/ST-70 owners will respond with more on this.

The phono noise is a different problem; I'm thinking it's better to cure the gain-matching problem first. You can "read all about it" (well, more about it anyway) in my Signals and Noise white paper on the Bottlehead Community page.

[choff]

Picked up the 6db version.  Took care of the hum issues.  In fact, if possible,  it really made the system sound a lot better overall.  That was a nice surprise. Thank you so much for all this great advice. 

Now if i could only figure out why my tonearm is so sensitive since this mod and how to correct it.

[Grainger49]

Picked up the 6db version.  Took care of the hum issues.  In fact, if possible,  it really made the system sound a lot better overall.  That was a nice surprise. Thank you so much for all this great advice. 

Now if i could only figure out why my tonearm is so sensitive since this mod and how to correct it.

Glad you got it fixed.

For the phono problem start a thread in the Phono folder.  Include what you mean by "sensitive" after the mod.

[choff]

Perhaps,  but it does seem odd and more appropriately addressed here given the fact that this only occurred immediately AFTER the Anticipation upgrade was installed.  You know??

By sensitive I mean that there is a microphone quality when I touch the tonearm or tap the platform that the turntable sits on.  This is really only noticeable at high volume settings on the Foreplay when no music is playing.

Otherwise.....everything sounds outstanding.

[Doc B.]

Sounds like it is a case of the gain increasing with the upgrade to the point where you will hear more noise artifacts if you crank the volume, in other words you may hear stuff that was there before but just not amplified quite as loud when you cranked the volume up before the upgrade. Sounds like the best approach might be to consider some form of turntable and/or tonearm isolation.

[choff]

wow.   so that would be a possible problem exclusive to the Seduction / turntable's interaction with the Foreplay and not the CD player / Foreplay performance??....because that is flawless at present.

[Doc B.]

I don't think it's really an interaction, I think your tonearm has been picking up noise all along and it didn't become noticeable until the system gain was increased with the Anticipation upgrade. In other words the problem has always been there in the tonearm, and you now hear it with the new preamps because they are more sensitive than the previous setup you had. That's why you wouldn't hear any problem with the CD player. Based upon your description, isolating the turntable from external vibration should reduce the noise.

[Paul Joppa]

If the tonearm rings like a bell when you tap it, then mechanical damping might help. You can probably try the low-residue - usually blue? - masking tape for something easily removed if it has no effect. (No, I'm not guaranteeing this!) Just put it around the end closest to the bearings, where it won't affect the dynamic mass so much.

[Grainger49]

Carl,

Your turntable isn't really reacting to the Seduction.  The Seduction is showing you what your turntable is doing.  In other words, the system has become more revealing and resolving, so you hear good and bad things you never heard before with lower bandwidth pieces.

I haven't asked where you are but there might be a Bottlehead in your area.  Two heads are better than one.  Entice him with either the promise of beer or his favorite brown liquid.  It would work for me if I'm in your area.  Even I work better talking to someone who can bounce my thoughts back, it doesn't work with just me, and I have been doing this for a long time.  If you post in the General Forum here you might find someone who can walk through the system with you to check grounding, reseat your tubes to clean the pins and socket and help eliminate the noise.

Noise can drive you crazy in short order, especially me as it is a short trip.  There are just so many places that it might creep into the system.  I reseat my tubes 2-4 times a year.  As PJ pointed out the outer conductor, ground, of interconnects are notoriously unreliable.

I like PJ's suggestion of painter's tape to test the arm.  A plug of blue tak (comes in yellow at Wal-Mart in the office supplies section) will deaden the tube too if you can insert it into the tube at the front.  It also adds mass to the end of the arm, not necessarily a good thing.

Turn on sequence with tubes should be Seduction or source, wait 10s, Foreplay 2, wait 10s, Stereo 70.  That way all the turn on noise doesn't get amplified.  Reseating tubes, all the tubes in the Seduction, Foreplay 2 and ST-70 will help with some of the rushing you hear.

Since PJ mentioned attenuators you might also put another pair of 6dB attenuators at the ST-70 to decrease the sensitivity of the total system to the noise you hear because of the high gain system.

P.S. You have a PM.