The distortion appears to be caused by one of the new tubes. Replace the new tubes - one at a time - with equivalent older ones, listening to the amp after each replacement, until distortion disappears. This technique should allow you to identify the bad tube. Hope this helps. |
Budrew, tracking down a sick tube requires a little patience and a consistent, methodical approach. Also, keep in mind that moving a tube can cause an intermittant problem to clear up for a while, but then return later.
First, pull and re-seat all the tubes to make sure contacts are clean and you are making a good connection in the sockets. Probably a good idea to clean the tube pins while you're at it, if you didn't do this originally. If the noise continues, try to narrow down where the problem tube is located.
From your description, you know the noise is in the left channel but you don't know if it is in the preamp or the power amp. If you have a way to resolve this, that would be a first step. For example, if you have a CD player or tuner with variable outputs, you could try plugging it directly into your amp to see if the noise continues. You would then know whether the problem is with the amp or the preamp.
If you decide the noise is most likely coming from the preamp, if it is a full function preamp, determine if the noise is in the phono stage or the line stage (i.e., do you hear the noise only when playing an LP).
Then try switching one tube from the left channel with it's matching partner in the right channel. Listen for whther the noise shifted to the right channel. If it did, that's the tube to replace. If the noise stayed in the left channel, switch a second pair of tubes. Switch only one pair at a time, and don't switch another pair until you've listened long enough to be sure you are getting consistent results.
Have patience and be methodical. Good luck! |
If the buzzing continues to exist in one channel only, start by swapping each pair left and right until the distortion hops channels. Too tedious? You could always pay someone else to check it out.
Buzzing commonly indicates a faulty tube. Then again, there are some species of moth that like to nest in the tube sockets...
Take heart. Be patient. Keep telling yourself how happy you'll be once it's all sorted out. |
With my ARC PH-3, I had a situation were I replaced all the tubes with NOS JAN Philips and everything seemed ok for a while. Then, problems with the right channel. My intention was to put back the original Sovteks one by one until the unit worked, but after substituting just one the situation seemed ok. Short while later, problems with the right channel again. So I brought the unit in to the local ARC dealer for an inspection. Turns out the mute switch was bad. They checked the two sets of tubes I had and they elected to put back the original Sovteks, declaring them way better than the just recently bought NOS. Moral of the story: NOS may not be the best road to go down (conversely, ARC dealers may be averse to using anything other than what ARC sells???) and more than one problem can surface at once making diagnosis/repair best left to qualified techs. Good luck. |
I had this problem. The first thing I did waw to reverse my interconnects to see if the sound moved from right to left. In my case it did not so the problem was in the amp.
Next, I reversed all of my tubes in the amp to see if the sound moved and i did this to see if indeed the problem is a tube or some other connection. The noise moved.
Then it was just a matter of time as I traded pairs of tubes until the sound moved again. I nest moved just one of the tubes and the noise moved again. Bingo! |
I'm facinated with the fact that the hum level varies with the level of the music - the reason is that the tubes in the line stage and amp are constant and merely pass on, amplified, what passes thru them. Question - does this problem occur with any source you select, or just one? |
Thanks folks. I'll have to spend some time this weekend on this detective effort. The sound, a buzz that reminds me of a blown speaker though I did nothing to effect the speakers this way, appears with whatever source I have selected. This morning I switched interconnects between preamp and amp and the sound was still coming from the left channel. I'll try switching the left and right tubes in the amp and see where that goes.
Do you use a Q-tip to clean the tube pins?
If necessary I'll take the amp in for service, but it weighs 100 lbs so it's a freakin pain in the arse. |
What did you buy for new tubes, and from whom? Are you still using the new tubes in your preamp, amp, or both? What make is your preamp and amp (monoblocks?) |
At Radio Shack, there are non-shedding replacements for Q-tips so no particles accidentally transfer from tube pins into tube sockets. Another way to go is to use tiny, pointed, non-shedding eye cosmetic applicators from the cosmetic section at any pharmacy. These are what seem to be included with the wonderful Walker Audio SST contact enhancer, for use on tube pins, only after your mystery problem has first been definitely solved. Caig makes contact cleaner-enhancer suitable for tube pins, but other Audiogon members can comment whether there is any type, and concentration, of ordinary alcohol also acceptable for preliminary cleaning of tube pins.
Owning tube equipment is more fussy than transistor equipment, and I have been saved more than once from the sound of silence, by having at least one backup tube of each type used in my components. This is one of the prices paid to stay on the side of the angels. |
I put the stock tubes back in both components and that's when the problem started. The new tubes I tried then removed were Electro-Harmonix purchased from Tubeworld. The amp is the Mcintosh MC2102 and preamp is C2200. |
I'm frustrated because I'm stuck here at work in meetings and all I want to do is trouble shot my tube problem : ( But I suppose we have to earn the money to pay for this hobby, eh.
It occurred to me I can try switching the channels for the speaker connections. This may not help with much but at least it will clarify if in fact it is a speaker problem. I have no reason to believe there could be a problem with the speaker, but it's one more thing I'd like to rule out for sure. |
McIntosh 2102? I have that amp. The stock tubes used to be Svetlana KT 88 and a bunch of Chinese-made smaller tubes. I understand that the newest 2102 amp has Electro Harmonix Kt 88s, but I don't know what the rest are.
My 2102 sounds great with the Svetlana tubes and I traded out the 12AT7 tubes for some 1960-era Sylvania and the 12AX7A to Electro harmonix. This made a terrific differance as the stock tubes never reached my espectations.
I am told that the Electro Harmonix KT 88s are fine, but if McIntosh is still using those Chinese other tubes, junk them. |
I don't know if I should feel stupid or relieved. I switched speaker cable channels and the problem still occurred in the left channel. I was sure it was not a speaker problem but I checked it out to see what was what. It turns out there is a ficus tree next to the left speaker that had grown a limb between the speaker grill and the bass driver and when the bass driver started thumping some of the leaves were vibrating off of it. Doh!!!
I'll check into the EH KT-88s. My amp is from late last year. I still have the EH tubes and may try them again someday.
Anyway, thanks to you all! |
My hat's off to you!!!!! Talk about a mistake that would be hard to own up to, most folks would be running around looking for a place to bury that one. You're on the honor roll for honesty, if nothing else. :-) |
As Maxwell Smart would say: the old tree growing in the speaker routine, eh? Glad you solved the mystery! |
Being a fellow owner of the marvelous 2102, I had serious doubts it was the amp itself. This thing is built like a tank. |
I don't think my local ARC dealer's service dept. would have figured out the ficus tree syndrome! Glad you found the source of your woes. |
OK, I can admit human error : ) Having figured out the trouble I put the NOS 12AX7s back in the preamp and also a pair of the EH 12AT7s. This rounded off some of the gritty edges and I'm back to captivating tube bliss : ) So nice! I'm happy. |
If you ever get a chance to try a pair of Mullard 12AT7 tubes you will find some improvement in bass on the 2102. |
