Low output on Seduction

[smithanh]

I just completed a build on a Seduction with the C4S upgrade, and am not getting the results I had hoped.  First, I'm not getting much output.  I'm running it through a Stereomour and Klipsch LaScalas, and I have to turn the volume up more than halfway to get only modest volume (my wife hasn't said a word!) but when I play a CD, I can hardly turn it up more than 1/4 before it gets too loud!  And I'm getting a bit of quiet white noise from the right channel.  Biggest issue is that overall, it sounds congested.  I had a couple problems with the build, some because of old manual and some because of my incompetence, but it seems that I have everything done pretty much right.  It plays, and no smoke is coming out.

I am NOT an expert on electronics, so any advice or things to check in layman's terms would be welcome!

[Paul Joppa]

First thing, halfway on the volume pot is about 20dB lower than all the way - that's 1/100th of the power. Do not be afraid of using the upper half of the volume control! You paid for it, might as well use it...  :^)

(By the way, I assume the voltage checks are OK - no serious problems with the Seduction operating conditions. Just making sure.)

Second - "congested" is a good description of what I hear while gear (mostly capacitors and transformers) is breaking in. If you don't have at least 50 hours on the newest component, try to suspend judgement until you do. I didn't believe in this effect - it makes no technical sense - until I did the experiment of doing the breakin without listening (driving a resistor instead of speakers). I heard exactly the same change that I had heard while listening to the process. And I'm a reasonably hard-headed engineer.

Now to the gain issue. I do have a white paper on the Bottlehead Community page on signals and noise - bottom line, signal levels are far from standardized in home audio gear. So it's not surprising that one source (phono) may be a lot different than another (CD player). iPods, tuners, and internet/satellite radio are other sources with their own signal level peculiarities. We can make changes to accommodate these differences but I'll put put off that discussion until we make sure there is nothing fundamentally wrong with your components.

So - first questions, what is the output level of your CD player, and what is the output of your phono cartridge? If you can't find specifications for these, give us the model numbers and the community can often locate the missing information.

Second question, what kind of music are you listening to - I ask this one just because the compression used in the studio varies a lot between genres and that can make a big difference.

Third question, does the vinyl sound like the equalization is OK - no seriously missing or overemphasized bass, treble, or midrange? The makes sure that there is no error in the equalization network of the Seduction.

[Grainger49]

Let's see...   Some basic things, what is the output of the cartridge, I.E. ???mV?  Suggested is 2.5mV or higher.

Post only the resistance and voltage measurements that are out of spec by more than +/- 15%.  Measurements that are good are expected and only clutter up the post with useless information.

The hiss you have in the right channel, it can be the cathodes forming, that is black magic electrical stuff that you don't need to know.  Paul, above, has explained not to judge till you have 50 hours on the components.  But,  have you swapped the tubes?  If so, did the noise swap channels?  That would locate the noise in the tube.  It might likely go away after 50 hours.

By the way, my Seduction was 1/4 turn louder than my CD player.  Still it was quiet and sounded great after break in.

And finally, you can make the CD matched to the Seduction with a pair of series resistors.  What that will do is bring down the CD volume so that when you switch you don't get blasted out of the room. 

[smithanh]

Checked the voltages again and had some interesting readings.  First, a couple terminals that should have read 0V showed voltage. Here are the terminals and the voltages that are wacky:

Terminal  Manual   Reading
A1           70         127
A2           0           1.6
B2           0           4.2
A4           0           6
B4           0           4

Everything else checks out.  The problem seems to be centered around the heater wiring and because it is small and crammed in, I can't visually tell if there are any shorts or bad joints.  Is it worth removing the whole connection and starting that part over?

[smithanh]

And about the output (which I think is related to my last post), I've got a Shure V15 VxMR which is rated 3.0mV
The CD player is an old NAD C521BEE, don't know what it's output is.

[Paul Joppa]

Good stuff! These are important variations from the correct values, and they can be used to help figure out what's wrong. And they indicate there IS something wrong, so your ears are not deceiving you - always a relief to know!

First off, the A1 voltage suggests a bad tube. But A2 and B2 should be close to zero. If you are reporting millivolts (mV) then the readings are reasonable and the tube is not conducting enough current on the A1-A2-A3 triode. But if they are volts then something is badly wrong. Check the meter's manual if necessary - this is a common confusion with autoranging meters.

If it still seems to be a bad tube, then swap the tubes and measure again to confirm it - there are other (less likely) possible causes so let's be sure. If it's a bad tube, it may "burn in" if you give it 50 hours of running - that's been known to happen - but it may just be a bum tube, in which case contact the Queen (Eileen) and she'll take care of it.

The heater voltages worry me. A4 and B4 are connected to each other and should read the same voltage. Again, it is possible that you are measuring millivolts instead of volts - autoranging meters will do this to you! - so check the rest of the markings. If it's mV then it's no problem. Do both tubes show an orange filament glow?

In the above, I am assuming the rest of the voltage checks are OK -  I think you said that, I'm just making sure.

The V15 is on the low side of output (great cartridge btw), and the NAD C521BEE is slightly high -  so the level difference is reasonable. We can deal with that (as Grainger suggested) by adding a resistor at the selector switch. But let's get the Seduction operating correctly first!

[smithanh]

Thanks! I'll swap the tubes tomorrow (easiest to do).  Both are glowing.  And I'll leave it on overnight to burn it in.  I know this is not as good as playing music through it, but it will apply heat for a while.  As long as you're pretty sure I won't burn the house down!

[smithanh]

Just got back from a business trip.  Looked carefully at all the solder joints and trimmed a few leads, but everything looked right, but I was still getting the same bad voltage measurements.  Hooked it up and was only getting left channel.  Switched the tubes and only got the right channel.  Have been typing with it playing for a couple minutes and the left channel just kicked in.  Could this be a bad tube?  Should I just let it run for a while and see what happens?

Thanks,
Andy

[saildoctor]

It can be helpful sometimes to check each connection one by one with a small pair of needle nose pliers (with power off and power supply caps drained.)  I've made a goof or two that I had missed by visual inspections alone.  Although it could be a bad tube...?

[2wo]

If it is working now it is probably not a bad tube. You probably have a iffy solder joint on that side. At some point you will need to address it.  Me I would enjoy it for a while, Circle back when it bugs you or starts to give trouble.
 We'll be here...John

[Grainger49]

Bottlehead sends out new tube sockets.  Who knows how long ago they were made?  So it could be a dirty tube socket or dirty new tube pins.

Just to be sure check FAQ # 2.

[smithanh]

Seems to definitely be a tube.  The right channel wanders in and out, but it is sounding better.  I'm going to let in play for 50+ hours before I take any next steps.  Thanks for the advice.

[Laudanum]

Yeah, I'd definitely replace the problem tube, it accounts for atleast a good protion of your issue.   You mentioned that the lack of left channel became lack of right channel when you swapped tubes around.  Im no tube guru but never had one that just flat out didnt work and ended up permanently fixing itself for the long term.  Not worth the hassle for current production tubes, just replace it, Bottlehead will send a new one out, just call the Queen, Eileen.

[smithanh]

OK, I'm back and still have some problems ...
First of all, I did have a bad tube (thanks Queen Eileen!) and the lack of channel problem is fixed.
The bigger problem is that I still have some bad voltages.  I've visually and physically reinspected the solders (multiple times!) but have not been able to cure this.  Here are the voltages that are off.

Terminal    Manual   Measured
7              0           1.4
26            0            3.6
36            0            2.4
A2            0            3.5
B2            0            2.4
A4            0            3.7
B4            0            5.6

Sound is still dark and muddy.  Not much high end and certainly no "space"

Any suggestions greatly appreciated!
Andy

[Grainger49]

Terminal 7 should be at ground/circuit common.  The same goes for T10, T11, T14, T16 and T20.  Since you don't list any of these there might be a bad solder joint on T7 or the other end of the ground buss at T10.

T26 is tied to ground through the 1M ohm resistor.  That should keep it at ground.  Check this resistor for both T26 and T36.

Since A2 is tied to T26 the same thing goes for A2 as for T26.  B2 is the same as A2.

A4 and B4 are wired together, they should have the same voltage on them.  3.7V and 5.6V doesn't make sense. 

But... there should be a bare wire from T7 to T10 and from T10 to T11.  Since T11 is at ground in the high voltage supply that should keep any voltage from being on A4 and B4