Older Bottlehead Gear Problem

[K.Boudreau]

Hi.  I'm hoping some of you can help me here.  I posted this in the General Discussion forum, but mayby it belongs here. Anyway...

I have a full Bottlehead system that I bought and assembled around 4-5 years ago and have never had a problem with it until now.  I have the Seduction, Foreplay, and the Paramour 2A3 amps that were available back then.  They are stock except for I am running DC filaments on the Foreplay.  I have never had any problems with hum or ground loops or any noise until now, and I haven't changed anything since I've hooked them up several years ago.  Now, I have been getting an on and off again hum that jumps from one speaker to the next in a sort of ping pong, and sometimes both at once.  With the hum comes distortion as if there is a drop in voltage.  This tends to happen in the evenings and night for the most part from what I can tell, which makes me suspect some problem with the electricity in my building or neighborhood - but this could be just my imagination I guess.  The system will sometimes develop this problem after the amps have been on and in use for several hours, or sometimes right after starting them up. 

The Paramours have the C4S boards installed (I think that's what they're called), and normally when I start them up, last in the chain, there is around 15 seconds of hum as they warm up and then the hum instantly shuts off, which I assume is what the boards do, and is normal.  My problem sort of sounds like the hum before the warm up, but with distortion and sometimes loss of audio.  Again, this happens on both sides.  I live in an apartment in a house that is over 120 years old with wiring dating from the early 1950s, at least, and I can't do anything about that, but I have the system plugged into a decent quality (not audiophile at all) powerstrip that is plugged into the two prong outlet with a ground lift adapter.  The thing is, I have had it this way for years with no problems and haven't changed anything in my apartment electrically since I've had this system.  Apart from a bit of tube rolling in the first year that I owned this system, nothing has changed and the performance has been flawless and fantastic.  So...what can I do?  Should I check the wall voltage with my DVM?  Is the powerstrip suspect?  Tubes going bad?  Solder joint(s) going bad (remember it happens at the same time on both speakers)?  Neighborhood or building power bad?  Do I need a power conditioner?  Everything?

Help please, this is driving me crazy!

Thanks!

 

[Grainger49]

I don't expect that power problems (poor power quality) will cause hum in the system.  Certainly if it did it would always be both channels at the same time never the Ping Pong effect that you described.  

What you have is an ungrounded system.  There are many ungrounded systems out there that are hum free.  But power would be the last thing to check out.  That hasn't changed and you never had a ground.

One thing that is confusing is that you describe a hum in one channel then the other, Ping Pong, then say it happens in both channels at the same time later.  If it is both channels, it will probably be a problem in the power supply.  I will bet on an aging solder joint that wasn't 100% to start.  Most solder joints last decades.

Yes, the tubes could be going bad.  However, I wouldn't expect both right and left tubes to go at so close to the same time.  Don't rule it out.  Just swap in a new set, one pair at a time to see.  Try this next to the last (power being the last thing to consider).

If it were a bad solder joint in the Foreplay power supply it would be both channels always.  But maybe it is a bad audio circuit ground in the Foreplay.  This could cause problems with one or both channels.

There are stages of troubleshooting to help.  You have to find out if it is the source, interconnects, Foreplay, Paramours or the tubes.

When it happens next swap the left and right interconnects between your Foreplay and Paramours.  I mean swap the left and right with each other on one end.  Does the hum swap?  If it does it is in the Foreplay or source or these interconnects, if not the problem is in the Paramours.  I don't suspect the Paramours as they are not in the same chassis.

If you find it is the source or Foreplay then while it is still happening swap the interconnects from your source to the Foreplay at the Foreplay.  If it swaps sides it is either the interconnects or the source.  If it does not swap you have isolated it to the Foreplay or the Foreplay to Paramour interconnects.

Once you have isolated the problem to a component & interconnect point, swap the interconnects with a new pair of interconnects.  The problem may disappear or not.  But you will have eliminated the interconnects.

If you have isolated the problem to either the Foreplay or Paramours swap the left and right tubes in the Foreplay or Paramours (both Paramour tubes).  Does the hum follow the tubes?  If the hum followed the tubes in the Paramours, swap only the drivers or the output tubes.  Does it swap back?  

Your hum on startup of the Paramours is normal.  Have you adjusted your hum pots using a meter?  Short the inputs, remove your speaker wires and put a meter on the speaker posts.  Then tweak the hum pot for the lowest voltage reading on AC volts.  This will get you really good numbers.

The last thing to try here is to roll in new tubes.  Maybe they did both go bad at the same time.

 

[Grainger49]

Bueller, Bueller, Boudreau, Boudreau....

Are you out there???

 

[K.Boudreau]

Present.  I was occupied this weekend with other things, but I did manage to read your reply, and thanks for the advice. 

Saturday night, the hum started happening on one side mostly, then the other, and then at the same time again.  This time the hum and distortion stayed, though it is often intermittent.  I tried switching the interconnects as suggested, with no luck, so I started pulling and switching out tubes.  I noticed that when I switched the 12AT7's from one side to another, the hum only occurred on one side, when it was originally going on both sides.  I found some other 12AT7's that I didn't know I had and put them in.  The hum disappeared!  And, the amps started sound much more alive and "sparkly" than before.  The tubes that I had been using were the originals that came with the kit, so they must have been going dull slowly for some time now, so slow that I didn't notice.  I was pleased that I had found the solution to the problem, until...

Sunday night, one side started to hum again, then the other.  A few seconds later a strange thing happened.  From outside on the street I hear a Bzzzzt! Pop! Pop!  And my lights dim and then flicker on and off and the hum increases.  Then, Pop! Pop!  BAM!!  And all the electric wall sockets go out, but not the overhead lights (which I hardly ever use, instead using floor standing lamps so I didn't notice right away).  It turns out that a power line of some kind had fallen loose and shorted out everyone's wall sockets on the block (I also found out that all the street lights and overhead ceiling lights in all the buildings are powered by another power plant and is on the same circuit as the hospital on the hill - weird). 

Now, I'm starting to think there may have been something wrong with the power in my neighborhood after all that was causing this.  There have been some other appliances that have been mysteriously faulty, only to work again later.  It turns out that my landlord, who lives below me, has also had the exact same appliances malfunction in the same way only to work later.  I also remembered that he had a microwave oven that would turn on, but not heat anything up, then work fine later.  Microwave oven - tube related?  Hmmm.

I remembered to switch off all the amps after the power went off, and the power company didn't get it fixed until after 2am, so I haven't had a chance to try them again.  I don't know, but it seems like such a strange coincidence that I would have seemingly solved the problem with new tubes, only to have the problem come again, and worse than ever, just as a power line drops outside and then everything goes out.  It could be just a coincidence, and power was last thing you said would cause the problems, but then...I don't know what to think now.  I guess I will just have to see how the amps function now that that power line has been replaced or repaired.

 

[Paul Birkeland]

When the power is back on, and the amps are up and running again, I would recommend rolling the 12AT7's again to see what you notice.  You might indeed have had an issue with line voltage, and that in turn could have cooked a tube or two a little bit.  Depending on how often you run your amps, the 12AT7's might indeed be worn out (I'd expect 30,000 hours out of new old stock American AT7's, and about 12,000 out of EH 12AT7's).

It sounds like you are on your way!
-PB

 

[Grainger49]

Edited!

Good, no truant officer will be sent.

Since you went from interconnect swaps to tube swaps you haven't eliminated the source, the Foreplay or the Paramours.  You will need to find what piece is the real source of the problem here.

What you described has happened to my Paramours.  I converted to a 76 driver.  The tube sockets I bought for the 76 are not the best.  My sockets aged and the pins got loose.  The ones Doc uses are better.  But most of us roll tubes more often than you seem to.  For instance, I bought one of the last 4 pair of Paramours made just before the Paramour II was released.  My original Sovtek output tubes have already become "mushy" and been replaced with some Chinese 2A3Cs.  Good tubes by the way.  I'm saying I have more hours on mine than you probably do.

Another thing that often happens is a tube gets a little oxidation on the pins and simply removing the tube and reseating it several times makes the problem go away completely.   So the old tubes may not be bad.  They may be bad, just check a second time after cleaning the tube pins and socket by removing them and reseating them.  If this is a factor then the tube swapping should have improved the problem somewhat at the minimum.

I'm still bothered that both channels exhibit the problem at the same time.  That is unusual.  It points elsewhere.  Most likely the Foreplay.

Your power problems should be completely eliminated when the new wiring is installed outside your residence.  (they will not just crimp on the old wires and let that go, it will be replaced)

 

[K.Boudreau]

So far so good.  No issues at all the last few days.  It seems to have been either the 12AT7's or the power line issues or both.  But, I'm not 100% convinced that it won't come back, that will take a week more or two for me to be sure, but so far it sounds great.  I don't know what brand the 12AT7's are that I put in, but they have definitely added new life to the sound.  Now I'd like to try some tube rolling again on all the units, but where to start?  Right now, I have the Sovtek's 2A3's that came with the kit, EI brand in the Foreplay, and NOS RCA's in the Seduction. 

The Chinese 2A3C's you mention must be the Shuguang 2A3C?  From here:

http://chinesetubes.com/index.php?main_page=product_info&cPath=2&products_id=18&zenid=7d04c337480c89f0cd5a204821a9da31

How do they compare to the Sovtek's?  Do you have any recomendations for any other brand tubes, new or NOS that I should check out for my other BH gear?

 

[Grainger49]

Well the problem could have been the tubes, could have been that the tubes were corroded on the pins (just needed cleaning).  But it is good to be back to clean sound again.

I never notice how the sound has deteriorated until I wake up one day and say, "Hey the tubes need changing!"  Sad!  I should realize it when the sound takes a down turn.

Over the years I have made a list of 12AU7 equivalents.  I am fond of the Mullard 4003 and Sylvania JAN 5814A variants.  I will post the whole list below.

Yes, it is the Shuguang 2A3C that I bought but I got them from ebay for under $100 delivered.  A search there will find the same vendor.  I think they are close to the RCA Blackplates I also have.  I presume that they are much better than new Sovteks, but my Sovteks were pretty worn when I did the comparison.  So it isn't really a fair comparison.

I still doubt that the power problem could cause on channel to hum.  It just isn't logical.

Here is the list of 12AU7 equivalents:

12AU7(A)(WA)
13D5 (?) should be 13V heater?
ECC186
ECC82
ECC802(S) Telefunken reported to be the best
E8025
E82CC
CV4003
CV4122
CV491
5814(A)
6189(W)(WA)
6680 (WL6680)
6067
7489
7316

 

[Len]

I still doubt that the power problem could cause on channel to hum.  It just isn't logical.

An unbalanced transformer/large DC offset could mess with the power tranny, and from there down the chain. Maybe.