Amp/Preamp Asylum

Looking for a new Amp or Preamp? If you're after tubes, post over here.

Return to Amp/Preamp Asylum

Message Sort: Post Order or Asylum Reverse Threaded

Looking for troubleshooting help

61.11.125.127
Posted on May 21, 2015 at 20:25:10
murali
Audiophile

Posts: 327
Joined: March 11, 2006
 I have a ARC Reference 3 line stage connected to Aesthetix Atlas stereo power amp, using balanced interconnects, driving a pair of Vandersteen Quatro wood. The ARC is also connected to my surround processor through the pass-through inputs for running the front speakers in HT mode. Of late I find the sound from the left channel significantly lower relative to the right in stereo, and also evident with the surround process test tones. So I am trying to find where the problem is - preamp or power amp. First, I swapped the interconnects at the power amp inputs, i.e. L of preamp to R of power amp and R to L. The lower sound then shifts to the right speaker and the left one sounds louder. Next I swapped the two input stage tubes inside the power amp with normal L/L and R/R connections. The left channel goes back to lower sound and the right channel sounds louder like it was originally. Do these conclude that the preamp is at fault? If yes, I wonder what to do next - change all the tubes in the ARC or leave the power tubes as they are. Any suggestions will be most helpful. Thanks in advance.

 

Hide full thread outline!
    ...
RE: Looking for troubleshooting help, posted on May 22, 2015 at 00:08:37
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 There was no need to switch tubes in the power amplifier. The first test revealed the problem is not in the power amplifier. It could be a connection problem or an interconnect problem, though. Do you have another pair of balanced interconnects to go in-between the preamp and the power amp? If not, try switching interconnects from left to right just to determine whether the problem is a faulty interconnect. If the problem switches channels, then the interconnect is at fault. If the problem goes away, then it was a bad connection at the preamp output. If you are not already doing so, you should use Caig DeoxIT Gold on all connections.

If the problem remains after changing interconnects, then your problem is in the preamp.

Good luck,
John Elison

 

RE: Looking for troubleshooting help, posted on May 22, 2015 at 03:13:17
murali
Audiophile

Posts: 327
Joined: March 11, 2006
 I changed the interconnects. They are not the culprits. I now replaced all the tubes in the preamp and hoped for the best but the problem remains. Swapping the tubes inside the power amp was tried as suggested by Jim White of Aesthetix (who now wants me to send the amp to them which is not a feasible solution for me).

 

RE: Looking for troubleshooting help, posted on May 22, 2015 at 04:18:04
Blackdog
Manufacturer

Posts: 1505
Location: Ontario
Joined: March 20, 2006
 Your first step (swapping one end of the interconnects) would lead you to think the problem was the preamp.
However your second step (swapping tubes in the amp) has nothing to do with the preamp. Why would you conclude the preamp was at fault.
What you may have is a bad tube in the power amp.
Since you have HT bypass, try it in that mode. Does the channel still have lower output when using the HT. HT almost completely eliminates the circuitry in the Line 3.
Dan Santoni

 

RE: Looking for troubleshooting help, posted on May 22, 2015 at 05:06:26
murali
Audiophile

Posts: 327
Joined: March 11, 2006
 The power amp is a hybrid with just one input stage tube per channel which I swapped as suggested by the manufacturer. There was no change (unlike when I swapped the interconnects when the lower sound moved from Left to Right) and the Left channel output continued to be low. That is when they suggested I return the amp. This imbalance is very much evident when I play stereo where the imaging has shifted significantly to the right though the left channel sound is there at lower levels. With the pass-through, using speaker test tones from the surround processor, it is very much evident. Considering the practical difficulties in shipping the power amp (assuming the problem is with that), I am looking for some guidelines to see whether it can be fixed here.

 

RE: Looking for troubleshooting help, posted on May 22, 2015 at 05:25:49
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 Why do you think the problem is in the power amplifier? Your first test proves the problem is up stream from the power amplifier. Your second test shows the problem has nothing to do with the input tubes on the power amplifier because the problem remained in the same channel. I think you confused everyone with your second test because they all thought you kept the interconnects in the crossed configuration from your first test. However, you reconnected your interconnects properly at the same time you switched input tubes. Therefore, the problem is not in your power amplifier. You can return the amp if you want, but you're wasting your time and money and the problem will still be there when you get it back.

Does your preamp have a balance control? Perhaps it's not centered.

 

RE: Looking for troubleshooting help, posted on May 22, 2015 at 05:32:18
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 > Your first step (swapping one end of the interconnects) would lead you to think the problem was the preamp.

Well, the problem is upstream from the power amplifier.

> However your second step (swapping tubes in the amp) has nothing to do with the preamp. Why would you conclude the preamp was at fault?

He uncrossed the interconnects before swapping tubes in the amp. This is what he wrote:

> Next I swapped the two input stage tubes inside the power amp with normal L/L and R/R connections.

Consequently, the problem is still upstream from the power amplifier. The problem is not in the power amplifier.

 

Your problem is not in your power amplifier! /nt\, posted on May 22, 2015 at 05:33:45
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004

 

RE: Looking for troubleshooting help, posted on May 22, 2015 at 06:16:33
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 You wrote: " I swapped the interconnects at the power amp inputs, i.e. L of preamp to R of power amp and R to L. The lower sound then shifts to the right speaker and the left one sounds louder."

So this says that the problem is preamp or what is feeding the preamp. I suggest you repeat this experiment and confirm you get the same result. If you do, then you need to swap the inputs L & R going into the preamp to confirm if it is the preamp or the source that is feeding the preamp.

 

RE: Looking for troubleshooting help, posted on May 22, 2015 at 09:17:24
airtime
Audiophile

Posts: 11287
Location: Arizona
Joined: February 4, 2003
 Can you try this all with a different source? Like another CDP - ANY CDP.

Also can you swap out the balance cables for plain RCA jack cables?

 

my vote is a bad tube in the preamp - its clearly not the amp nt, posted on May 22, 2015 at 10:59:59
Ralph
Manufacturer

Posts: 4774
Location: Minnesota
Joined: April 24, 2002
 -

 

Based on his swapping methodology I have to agree - nt, posted on May 22, 2015 at 14:25:18
AbeCollins
Audiophile

Posts: 46295
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
 .

 

RE: Looking for troubleshooting help, posted on May 22, 2015 at 17:47:47
Blackdog
Manufacturer

Posts: 1505
Location: Ontario
Joined: March 20, 2006
 Agreed, I misread that section.


Dan Santoni

 

RE: Based on his swapping methodology I have to agree - nt, posted on May 23, 2015 at 09:06:48
murali
Audiophile

Posts: 327
Joined: March 11, 2006
 I mentioned earlier that I changed all the 6 tubes of the preamp and the situation is the same.
The preamp is connected to both my single stereo source (Ayre C5) as well as the front L/R of my Marantz surround processor (using pass-through) and in both cases, it is the same - lower sound from left channel. So why I should I suspect the CD player as someone has suggested?
The most important observation is that when swapped the L and R inputs at the power amp, the lower sound shifted from left to right, so logically both the power amp and speakers are okay and the suspect seems to be the preamp. So even after changing all the tubes in the ARC Ref-3, if it still does not solve the problem, what else could be wrong with it? Next I am going to run the surround processor L/R directly to the power amp bypassing the line stage and hopefully that should conclusively prove that the issue is with the preamp if the left channel sound improves.

 

RE: Based on his swapping methodology I have to agree - nt, posted on May 23, 2015 at 10:37:19
airtime
Audiophile

Posts: 11287
Location: Arizona
Joined: February 4, 2003
 Did you try another source!

Another input for the source!

And not using the balanced cable - RCA.

Don't bypass the simple fix!!!

charles

 

Simplify, separate, then conquer, posted on May 23, 2015 at 12:26:52
AbeCollins
Audiophile

Posts: 46295
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
You have too much crap going on. Simplify by separating the components then proceed methodically.

If you can't separate the components then half-split then half-split again until you narrow it down. It's a common troubleshooting technique for systems and circuits.





 

Simple, but still unresolved, posted on May 23, 2015 at 21:27:45
murali
Audiophile

Posts: 327
Joined: March 11, 2006
 Okay, the simplest test. I disconnected the source and preamp from my system and using different balanced interconnects, I connected my Marantz surround sound processor L/R directly to the Aesthetix power amp L/R, of course through the HP filter in front as always required for the Vandersteen Quatro. Played the test tones through Front L, Front R, Center, Rear R and Rear L speakers. The Front L sound is still low, at least 5 dB relative to the right (levels can be adjusted in test tones). When I swap the L/R at the power amp inputs, the lower sound shifts to the right channel.
So even without my stereo source and line stage in line, the left channel sound is lower by around 5 dB. Is there any other conclusion except that there is something wrong in the power amp? The question is what could be wrong with it.

 

Correction, with apologies, posted on May 23, 2015 at 22:03:06
murali
Audiophile

Posts: 327
Joined: March 11, 2006
 Sorry, one mistake in my previous post. When I swapped the interconnects at the power amp inputs, the lower sound of Left channel DID NOT shift to the right, it continues in the L at around 5 dB lower than the right.
Apologies for the mistake.

 

RE: Correction, with apologies, posted on May 23, 2015 at 23:29:09
AbeCollins
Audiophile

Posts: 46295
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
 If it were me, I'd get the processor out of the system and use just the linestage and power amp.... and a simple source like a CDP. Begin troubleshooting to determine if you have any channel imbalance between the L&R channels.... and be sure that your linestage balance control isn't offset.

IMHO, processors have too many variables that can be incorrectly set so that's the first item I would set aside and remove from the system to simplify the troubleshooting.





 

Final conclusion - it is the power amp, period..., posted on May 25, 2015 at 19:37:36
murali
Audiophile

Posts: 327
Joined: March 11, 2006
 With the help of a local technician, we systematically tried all the troubleshooting options, like swapping interconnects, speaker cables, preamp/processor/line-stage etc. All observations point out to the left channel output side of the power amp producing around 5-6 dB lesser sound than the right channel.
So the next part is going to be to measure voltages at different sections of the output side board of both channels and compare to find out the "weak" electrical element that may be causing the problem. It does not appear to be a total failure of some component(s) as otherwise, the channel should have been dead. It still responds when I increase or decrease the input. If someone has done a similar exercise and willing to share, it will be most helpful. The Aesthetix Atlas stereo amp uses tubes only on the input stage. I also requested the manufacturer to provide some guidelines for measurements and checks and hope they give some info.

 

Your initial post seems to contradict that..., posted on May 27, 2015 at 13:42:31
Ralph
Manufacturer

Posts: 4774
Location: Minnesota
Joined: April 24, 2002
 First, I swapped the interconnects at the power amp inputs, i.e. L of preamp to R of power amp and R to L. The lower sound then shifts to the right speaker and the left one sounds louder. Next I swapped the two input stage tubes inside the power amp with normal L/L and R/R connections. The left channel goes back to lower sound and the right channel sounds louder like it was originally.

The section in bold tells us incontrovertibly that its either the preamp or the interconnect. But apparently through other means you found out that the amp had a problem, so that means that the above highlighted text of your original post was incorrect. I'm glad you got to the bottom of it.

I was going to suggest a missing phase in the signal- for example a broken connection in the interconnect. This would have dropped the output in that channel by 6db. Oddly, that's about the same amount of drop you have surmised. Is it a coincidence?

 

RE: Your initial post seems to contradict that..., posted on May 27, 2015 at 19:24:08
murali
Audiophile

Posts: 327
Joined: March 11, 2006
 Thanks. Out of curiosity, just how do you find out a "broken connection" in an interconnect?

 

Its called a 'continuity test', posted on May 28, 2015 at 08:23:08
Ralph
Manufacturer

Posts: 4774
Location: Minnesota
Joined: April 24, 2002
 You measure the resistance from one end of the cable to the other- pin 1 to pin 1, pin 2 to pin 2 and pin 3 to pin 3 (FWIW it won't be pin 1 since that is ground and you are not experiencing a hum so its pin 2 or pin 3 that is open if the cable is bad).

This test is done using a Digital VoltMeter (DVM) set to the Ohms scale. The correct reading from the cable should be very similar to what you get when you connect the probes of the DVM together, 0.2 ohms or so.

 

Page processed in 0.024 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]