K701/DV332 left-channel buzz, not ground loop...
Aug 28, 2008 at 11:01 PM Thread Starter Post #1 of 22

JungleMan

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Here's my deal: I have a DV 332 and I was experiencing a terrible ground loop hum. I got a Xitel Ground Loop Eliminator which really helped out a lot but I still hear a faint buzz, but it's only in the left channel. I am still running the stock tubes, I think I've had this amp for around 6 months maybe a little longer. Adjusting the volume on the amp doesn't do anything to make it louder/softer.

Any ideas?
 
Aug 29, 2008 at 1:06 AM Post #2 of 22

Zodduska

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Quote:

Originally Posted by JungleMan /img/forum/go_quote.gif
Here's my deal: I have a DV 332 and I was experiencing a terrible ground loop hum. I got a Xitel Ground Loop Eliminator which really helped out a lot but I still hear a faint buzz, but it's only in the left channel. I am still running the stock tubes, I think I've had this amp for around 6 months maybe a little longer. Adjusting the volume on the amp doesn't do anything to make it louder/softer.

Any ideas?



Hi, You are correct that it's not a ground loop which would appear uniform between both channels. The most likely suspect is the tubes, since you are still running the stock tubes I would suggest trying some of the NOS (new old stock) tubes available, 403A/B / EF95 / 6AK5 / CV4010 / M8100 are the type of the small tube and 6S19 for the larger.. there is much audible improvement to be had by rolling tubes in your 332.
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To confirm the problem is in fact a bad tube try swapping the places of the right and left sets after the amp has been off for a while. If it IS a bad tube the buzz will move to the right channel.

If at that point you confirm the problem is not a bad tube it may be that one of the sockets is not making very good contact with the pins. It is possible to very slightly bend the pins outward near the ends to try for a tighter fit in the socket using needlenose pliers, use extreme care if you decide to do this as the stock tubes seem very delicate. Another thing to try would be a contact conditioner such as Caig ProGold aka DeoxIT Gold.

Finally if none of the above solves your problem it's possible that something in the amp is causing the buzz. Sadly, this has happened to at least one person that bought a 332 lately and posted about it in the main 332 thread.

edit: another easy thing to test would be to swap your RCA from right to left to eliminate that cable and source as a suspect.
 
Aug 29, 2008 at 1:33 AM Post #3 of 22

Zodduska

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edit seems to be bugged for the moment.
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Yet another thing to check for would be sources of Electrical or Wifi interference around the amp.
 
Aug 29, 2008 at 7:24 AM Post #4 of 22

JungleMan

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Thanks for the helpful post
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we can eliminate the cable completely from the diagnosis, as it happens even without any cable plugged in whatsoever. WiFi interference is possible as there is a wireless router about 6ft away, and the amp is located right near a ton of computer equipment (directly next to two printers and above two LCD monitors). I'll eventually unhook it and test it in another spot to see if that corrects the problem.

I'll assume that the tubes on the right side control the right channel and left controls the left? I'll try swapping them after the amp has been off-- how exactly do I take the tubes out? I'm kinda thinking it's the tubes too, and hoping it is as it'd give me a good excuse to upgrade
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Aug 29, 2008 at 8:35 AM Post #5 of 22

BigTony

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I sure hope swapping the tubes fixes it.
Unfortunately I've just been told be the engineer that he can't trace the source of the problem on my amp (three weeks and the've not figured it out).

Bummer

BT
 
Aug 29, 2008 at 9:26 AM Post #6 of 22

nor_spoon

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As I have said in other thread, I also had a hum in my amp, but I think it must have been interference from other electrical components sitting very close. When I moved it, the hum disappeared. It might apply to you.
 
Aug 29, 2008 at 11:53 AM Post #7 of 22

pataburd

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Check the tube(s) on the left channel. Every hum issue I've had with the DV337 has been (driver) tube-related.
 
Aug 29, 2008 at 11:55 AM Post #8 of 22

JungleMan

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Yup, actually I JUST finished swapping the tubes and sure enough, the hum moved to the right channel. I guess the short answer is just that I need new tubes, right?

Where's the best place to get them and what kind should I go for?
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PS: Is it a bad idea to leave the tube covers off? I had to take them off to replace the tubes and I kinda like the way the amp looks without them...
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Aug 29, 2008 at 12:36 PM Post #9 of 22

nor_spoon

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Quote:

Originally Posted by JungleMan /img/forum/go_quote.gif
Yup, actually I JUST finished swapping the tubes and sure enough, the hum moved to the right channel. I guess the short answer is just that I need new tubes, right?

Where's the best place to get them and what kind should I go for?
smily_headphones1.gif


PS: Is it a bad idea to leave the tube covers off? I had to take them off to replace the tubes and I kinda like the way the amp looks without them...
cool.gif



I have mine off. I do not think it will make any difference.
 
Aug 29, 2008 at 2:51 PM Post #10 of 22

JungleMan

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I messed with the tubes a little further this morning and tried bending the pins out, to no avail. I tried switching the two power tubes around and the problem channel didn't change, so it seems that the problem is the shorter tube (don't know the name for it?). I figured since I was replacing one set of tubes I may as well replace both, so I went ahead and ordered a matched pair of Mullard 8100 as well as Ulyanovsk (sp?) 6S19P-V.

Should solve the problem and provide great sound quality... and Head-Fi, thanks for the apology about my wallet, but I'll forgive ya
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Aug 29, 2008 at 3:25 PM Post #11 of 22

pataburd

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Quote:

Originally Posted by JungleMan /img/forum/go_quote.gif
. . . PS: Is it a bad idea to leave the tube covers off? I had to take them off to replace the tubes and I kinda like the way the amp looks without them...
cool.gif



JM,
Both the Darkvoice 337 and the Bada PH-12 look better--and dissipate heat better--with their tube shrouds removed, IMHO.

Tube dampers may help (control the generally negative effects of microphonics), too. : )

PAB
 
Aug 29, 2008 at 3:27 PM Post #12 of 22

PrTv

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Quote:

Originally Posted by JungleMan /img/forum/go_quote.gif
I guess the short answer is just that I need new tubes, right?


Absolutely!
Those Chinese tubes should have been replaced in the first place, not because they're of low quality and unreliable, but because of their inferior sound. When you swap in a good pair of M8100 or 403B, you’ll know what I’m talking.

Quote:

Where's the best place to get them and what kind should I go for?
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eBay usually is a great source. However, you may need to take special care when bidding some tubes the sellers of which do not give you much information (some sellers even use the same picture for every tube they sell).

Quote:

PS: Is it a bad idea to leave the tube covers off? I had to take them off to replace the tubes and I kinda like the way the amp looks without them...
cool.gif


IMO, it’s a better idea to “leave it off”, since I don’t think those covers serve any purpose. Most people say they’re for damping the tubes, but I find them make the amp sound so hollow, plus area surrounding the tubes heats up considerably when I place the covers on (it traps the heat inside, which is not good for the tube). So my suggestion is just leaving it off and buying some real tube damper, if you want one.
 
Aug 29, 2008 at 4:22 PM Post #13 of 22

JungleMan

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Thanks for the help-- yeah, I know that tube rolling has been long overdue. I've liked this amp from the beginning but I've been waiting to put some tubes in it that would really "blow me away". I'll update with my thoughts once my M8100 and 6S19P-V tubes arrive. The eBay seller I bought from had a pretty good description and pics, even specified that they were compatible with the DV332... but thank you for the cautionary note.

Can someone briefly explain about tube damping? Microphonics? Are real tube dampers something worth looking into?
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Aug 29, 2008 at 5:19 PM Post #14 of 22

Pricklely Peete

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Quote:

Originally Posted by JungleMan /img/forum/go_quote.gif
Thanks for the help-- yeah, I know that tube rolling has been long overdue. I've liked this amp from the beginning but I've been waiting to put some tubes in it that would really "blow me away". I'll update with my thoughts once my M8100 and 6S19P-V tubes arrive. The eBay seller I bought from had a pretty good description and pics, even specified that they were compatible with the DV332... but thank you for the cautionary note.

Can someone briefly explain about tube damping? Microphonics? Are real tube dampers something worth looking into?
smily_headphones1.gif



Not really. Tubes either go microphonic after a little use, are microphonic from the get go or aren't at all and are dead quiet in use...tube dampers won't change that much. Micro phonic simply means transmitting of exstraneous noise outside of the normal signal, like light taps on the amp chassis, the headphone cable (not the 1/4 in jack, just the cable swinging) rocking back and forth in the jack etc...Do not tap the tubes themselves when they are powered up, that's never advisable anyway. A simple test is a gentle tap on the amps chassis, if that is being amplified the drivers are micro phonic. I had a pair of matched Sylvania 6AK5's from 1953 that went micro phonic on me in less than a month of use...which is a bummer since they sound great...but I can't stand the cable noise unless I remain absolutely still...which for me is kinda impossible.
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Just make sure the amp is on a sturdy shelf with lots of room to allow heat to escape and one that is not prone to vibration (like footsteps etc..) that will go a long way towards making your amp quiet for listening. With proper well functioning tubes the experience is wonderful
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Tubes are finite.... It's a bummer but that's how it is
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Those Mullards you chose are excellent, you'll be blown away for sure by the vast improvement these give you SQ wise. Arguably there are few better if any.

Peete.
 
Aug 29, 2008 at 5:35 PM Post #15 of 22

JungleMan

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Thanks Peete, I haven't noticed any of those effects with these tubes; the channel that doesn't have the bad tube is dead-silent when there's nothing playing. But hopefully I'll fare just as well with the new tubes. The amp is located on the very top shelf of my desk hutch which I did so that I don't spill anything on it, and it should have plenty of space to ventilate.

Glad I made a good choice with the tubes, I had read a bit about the tubes and M8100 kept being mentioned.
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Speaking of tubes being finite, how often should I be replacing them? I tend to leave my amp on 24/7, not sure if that's a bad idea... I just do it because I know tube amps take about a half-hour to warm up and I never know when I want to start listening.
 

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