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Home Theater => Audio => Tubes => Topic started by: Bogsle on Jan 06, 2009 at 11:09 PM
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With the SPL meter lying around after re-calibrating the HT setup I decided to play around with it.
I wanted to see if the speaker channels/outputs from my tube intergrated amp were equal.
First, I placed the SPL meter directly in front of the right speaker at exactly 2 feet away and played pink noise from the CDP. I turned the volume up until the SPL meter showed 70dB.
Next, without changing the volume control of the tube integrated amp, I move the SPL meter directly infront of the left speaker, also at exactly 2 feet away. I noticed that the SPL meter showed 69dB, and sometimes goes down to 68dB.
I tried reversing the speaker cables between left and right speakers, reversed the left and right interconnects, and even reversed the position of the tubes. But all the time I get the same readings from the SPL meter, which shows that the right channel is 1 to 2 dB louder that the left channel.
Based on the things that I have already done, it is neither the speakers nor the output from the CDP that is "unbalanced". It must be the tube amp then.
Is this normal or is there something wrong with the integrated amp?
Which components should I check or do I need to bring the tube integtrated amp for servicing already?
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Hi,
Have you tried swapping the signal tubes too?
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Hi,
Have you tried swapping the signal tubes too?
Yes, I did that as well.
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Bro,
Provided they share the same B+ supply (not dual mono, not monoblocks), and they have near identical plate resistor values for the voltage amplifier/driver stage then the only thing left is the tube amp's output transformers not being identical... (or am I missing something else? ::))
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Bro,
Provided they share the same B+ supply (not dual mono, not monoblocks), and they have near identical plate resistor values for the voltage amplifier/driver stage then the only thing left is the tube amp's output transformers not being identical... (or am I missing something else? ::))
Yes, correct in all your assumptions.
If its the OPTs, and assuming that both were identical from the start when the int. amp was new, is it possible the one of the OPTs could have deteriorated overtime? This is not normal, right? :(
Your suggestion, please.
Thank you very much for the inputs.
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Yes, correct in all your assumptions.
If its the OPTs, and assuming that both were identical from the start when the int. amp was new, is it possible the one of the OPTs could have deteriorated overtime? This is not normal, right? :(
Your suggestion, please.
Assuming the output trannies are truly identical from the start then something must have gone wrong and it's not normal, but I wouldn't go there just yet.
As of now, all we can do is speculate and that is not fair, so I would suggest that you continue to monitor the difference between the two channels with your spl meter to really see if it does change under normal use.
Another speculation is that your amp may have started it's life already "unbalanced". :)
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With the SPL meter lying around after re-calibrating the HT setup I decided to play around with it.
I wanted to see if the speaker channels/outputs from my tube intergrated amp were equal.
First, I placed the SPL meter directly in front of the right speaker at exactly 2 feet away and played pink noise from the CDP. I turned the volume up until the SPL meter showed 70dB.
Next, without changing the volume control of the tube integrated amp, I move the SPL meter directly infront of the left speaker, also at exactly 2 feet away. I noticed that the SPL meter showed 69dB, and sometimes goes down to 68dB.
I tried reversing the speaker cables between left and right speakers, reversed the left and right interconnects, and even reversed the position of the tubes. But all the time I get the same readings from the SPL meter, which shows that the right channel is 1 to 2 dB louder that the left channel.
Based on the things that I have already done, it is neither the speakers nor the output from the CDP that is "unbalanced". It must be the tube amp then.
Is this normal or is there something wrong with the integrated amp?
Which components should I check or do I need to bring the tube integtrated amp for servicing already?
we live in an imperfect world! ;D sometimes your left foot can be slightly bigger than your right foot....
question is, how does it affect your listening? can you hear that the right channel plays softer than the left?
if the answer is no, then the meter readings are more of an annoyance.....
and like they say, if it ain't broke, don't fix it. ;D enjoy the music..... ;D
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have you tried swapping loudspeakers ? It could also be the room.
is your room perfect ? I mean left side is equal to the right side ?
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Nolan you really have Dog ears! 1 - 2dB difference is negligible! Don't mind it we are listening on a Stereo sound.... ;D
But now that you check it, it bothers you! Time to change SET Amp!
Happy New Year Bro!
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Jun, masyado yata drastic yan SARS mo bro... ;D ;D ;D
baby steps muna and let's help Nolan diagnose the imbalance... :)
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brader nolan ;D
kumusta? buo na pala yang tube amp mo.
i think its the spl meter... ;D ;D ;D ;D
regards.
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With Nolan's test wherein the SPL meter is placed 2 feet in front of every speaker, will the room configuration have an effect on the imbalance?
Another area to look into is the tubes performance. Are they exactly matched?
Lastly, How does it sound in the sweetspot without the use of the SPL meter?
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With Nolan's test wherein the SPL meter is placed 2 feet in front of every speaker, will the room configuration have an effect on the imbalance?
Another area to look into is the tubes performance. Are they exactly matched?
Lastly, How does it sound in the sweetspot without the use of the SPL meter?
Thought of this as well, reflections can cause erratic readings but knowing Nolan's knowledge in tinkering with gears I'm sure he has taken this into account.
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Assuming the output trannies are truly identical from the start then something must have gone wrong and it's not normal, but I wouldn't go there just yet.
As of now, all we can do is speculate and that is not fair, so I would suggest that you continue to monitor the difference between the two channels with your spl meter to really see if it does change under normal use.
Another speculation is that your amp may have started it's life already "unbalanced". :)
Maybe so. Hmmmm....
Thanks.
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we live in an imperfect world! ;D sometimes your left foot can be slightly bigger than your right foot....
question is, how does it affect your listening? can you hear that the right channel plays softer than the left?
if the answer is no, then the meter readings are more of an annoyance.....
and like they say, if it ain't broke, don't fix it. ;D enjoy the music..... ;D
Yeah, I guess maybe I'm getting just too anal about this.
I just have to breath in and breath out....relax. :)
Thank you.
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have you tried swapping loudspeakers ? It could also be the room.
is your room perfect ? I mean left side is equal to the right side ?
Yes, did so.
I thought I tried removing the effects of the room already by placing the SPL meter at very close proximity directly in front of the speakers one at a time. Is 2 feet away still not enough?
Thanks.
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Nolan you really have Dog ears! 1 - 2dB difference is negligible! Don't mind it we are listening on a Stereo sound.... ;D
But now that you check it, it bothers you! Time to change SET Amp!
Happy New Year Bro!
Ayos bro. The best suggestion....hehehe ;D
Nooooo, not the AMX 845, nooooo.
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brader nolan ;D
kumusta? buo na pala yang tube amp mo.
i think its the spl meter... ;D ;D ;D ;D
regards.
Senor,
Funny ha, very funny... ;D
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With Nolan's test wherein the SPL meter is placed 2 feet in front of every speaker, will the room configuration have an effect on the imbalance?
Another area to look into is the tubes performance. Are they exactly matched?
Lastly, How does it sound in the sweetspot without the use of the SPL meter?
Yeah, is two feet away not enough to remove the room effects from the equation?
No, they are not perfectly matched. But is it not that the autobiasing will take care of that.
I remember also swaping the tubes between left and right channels but the left one still gave a lower dB measurement.
Regarding the sweetspot....hmmm.... gitna naman ang image ng kumakanta.
Baka nga ako lang sir talaga ang may problem, hehehe. ;D
Thanks.
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Anyway, thanks to all.
I certainly did not expect all these responses. I was not sure if my inquiry was valid or a bit silly to be taken seriously. I'm really moved. :'(
As a final act siguro, I will try changing all the tubes, the power tubes and the two peanut tubes.
I'll share my findings again.
But if the situation will be the same, I will just have to live with it and follow Tony's suggestion, enjoy the music. ;)
Cheers.
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Another possiblity is the components within the amp, capacitors and resistors which can drift from the original specs. Also this is why those exotics components are more expensive, their tolerances are smaller . Yung mga +/- 5 percent compared to +/- 1 percent sa mga exotic parts. Imagine on the extreme you could have a difference of 10 percent between left and right channel for a particular part....
try mo na rin pa clean yung mga switches specially the potentiometer ng volume and balance, treble and bass controls, if any
You should test each resistor and capacitor if its still within specs....para pantay ang tunog ng left and right channels, otherwise di ka matatahimik knowing you have 1 DB difference..hahaha Qguy.. now playing with your mind ;D ::) ;D
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Sir,
Many variables might come into play. Busted resistor, leaking caps, weak tubes, bad wire connection...
You can bring your amp in and we are more than happy to give you a free diagnosis.
www.audioamplified.com
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You should test each resistor and capacitor if its still within specs....para pantay ang tunog ng left and right channels, otherwise di ka matatahimik knowing you have 1 DB difference..hahaha
today's parts like resistors and caps are better than yesteryear's, today we have the Kiwames, holcos, polypropylene caps, tefloncaps, etc.,etc......whereas tube equipment of the olden days used paper caps, and +/-20% tolerance resistors, today we see film type not less than 5%.....
i wouldn't be bothered by a mere 1db. difference, not worth the time and effort.... ;D
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today's parts like resistors and caps are better than yesteryear's, today we have the Kiwames, holcos, polypropylene caps, tefloncaps, etc.,etc......whereas tube equipment of the olden days used paper caps, and +/-20% tolerance resistors, today we see film type not less than 5%.....
i wouldn't be bothered by a mere 1db. difference, not worth the time and effort.... ;D
Thanks for your thoughts on this matter, sir.
As for qguy and AudioAmplified, I will think about your suggestions as well. Thanks for the offer.
Regds.
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How about your room reflection sir? Why dont you measure the current coming from the amp. I mean the speaker output.
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I have the same problem with my tube amp and when I checked the innards I saw a couple of black cylindrical thingies na parang nag leak at ng matuyo ay naging white stain. Leaking capacitor po ba ito and another thing I noticed ay parang numipis yung tunog nya. Its a 50wpc 6550 PP int. amp. Cant bring to Manila for servicing dahil ang bigat baka mabali likod ko (taga laguna kasi ako)
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How about your room reflection sir? Why dont you measure the current coming from the amp. I mean the speaker output.
I don't think room reflection was an included factor.
I was hoping it will not be the case anymore since I placed the SPL meter 2 feet directly in flont of the each of the speakers.
Regarding them current measurement, I may have to call you one of these days.
Thanks.
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I have the same problem with my tube amp and when I checked the innards I saw a couple of black cylindrical thingies na parang nag leak at ng matuyo ay naging white stain. Leaking capacitor po ba ito and another thing I noticed ay parang numipis yung tunog nya. Its a 50wpc 6550 PP int. amp. Cant bring to Manila for servicing dahil ang bigat baka mabali likod ko (taga laguna kasi ako)
I'm guessing you are describing a capacitor there.
I don't think the capacitors are the culprit. I just had all capacitors upgraded last year from Audio Amplified (Mundorf) as shown here:
(http://i93.photobucket.com/albums/l67/bogsle/102_1250.jpg)
The auto bias resitors have been replaced also with new ones. The picture hasn't been updated. The white ceramic type resistors in the middle of the main board have been changed to wirewound enamel types.
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I have the same problem with my tube amp and when I checked the innards I saw a couple of black cylindrical thingies na parang nag leak at ng matuyo ay naging white stain. Leaking capacitor po ba ito and another thing I noticed ay parang numipis yung tunog nya. Its a 50wpc 6550 PP int. amp. Cant bring to Manila for servicing dahil ang bigat baka mabali likod ko (taga laguna kasi ako)
in your case that capacitor is easy to replace, just get another one with simmilar specs and solder it in, if that was an axial type, you can still replace it with a radial type of same value, all you need are soldering skills to do it.
in order to avoid mistakes, do not remove the leaky cap just yet, solder in the repalcement in parallel then cut off the leaky cap after, you can tell your tech to do this.. ;D
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I have the same problem with my tube amp and when I checked the innards I saw a couple of black cylindrical thingies na parang nag leak at ng matuyo ay naging white stain. Leaking capacitor po ba ito and another thing I noticed ay parang numipis yung tunog nya. Its a 50wpc 6550 PP int. amp. Cant bring to Manila for servicing dahil ang bigat baka mabali likod ko (taga laguna kasi ako)
Hi Ding,
I took a look at your 6550 PP amp about an hour ago, the white stain things on the bypass caps are the glue that hold the wrapper on the polypropylene caps, the caps are intact, the labels are not. On your left channel, both the cathode bypass caps are gone and bulging.
For the life of me, I cannot believe that the designer of the amp placed 50Volt capacitors on the cathode of the 6550! (cathode biased) The voltage on the cathode hovers at around 48 to 50VDC. He even used Rubycon caps for the cathode bypass! This guy is suicidal. >:(
This is the second amp that he designed and built that I am fixing, both are PP amp one is KT88 and this one is 6550.
I will text you with other things that I will see on your amp.
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This is the second amp that he designed and built that I am fixing, both are PP amp one is KT88 and this one is 6550.
does he have a name?, i think you should name him, otherwise all guys that are into diy will become suspects.... ;D
as a matter of courtesy, the one who built the amp should have the first crack at repairing the amp, after all selling amps comes with an after sales service, it goes without saying..... ;D
if it were me, i would not touch it until the maker of that amp has been suffieciently informed and given the chance to work on the repairs...this is how it was in the old days, shouldn't be any different today.... ;)
owner's of tube amps must realize that having one is not like having an SS amp. owners are obliged to know more about their amps unlike SS ones... ;D
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Having a tube amp is like getting a vintage car, it requires some TLC.. unlike an SS amp..
This was my advise to a friend who dove into the tube amp headfirst, specially if your going to go the DIY route or the used / Vintage market route..
owner's of tube amps must realize that having one is not like having an SS amp. owners are obliged to know more about their amps unlike SS ones... ;D
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Having a tube amp is like getting a vintage car, it requires some TLC.. unlike an SS amp..
This was my advise to a friend who dove into the tube amp headfirst, specially if your going to go the DIY route or the used / Vintage market route..
...meaning SS amp is modern tech ;D ;D ;D
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...meaning SS amp is modern tech ;D ;D ;D
tubes were invented in 1903 by Lee DeForest, he invented the triode, the transistor was invented in 1946 at Bell Labs. so that makes SS the newer technology..... ;D
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tubes were invented in 1903 by Lee DeForest, he invented the triode, the transistor was invented in 1946 at Bell Labs. so that makes SS the newer technology..... ;D
43 years gap. matanda pa sa akin ang pagitan.
informative! tnx
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owner's of tube amps must realize that having one is not like having an SS amp. owners are obliged to know more about their amps unlike SS ones... ;D
Having the tube amp exprience for sometime now, I could not agree more.
It's kinda hard nga lang for us who don't have the background nor the schooling, coz we have to really catch up and learn as much as we can, in my opinion. But nevertheless necessary.
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This is the second amp that he designed and built that I am fixing, both are PP amp one is KT88 and this one is 6550.
does he have a name?, i think you should name him, otherwise all guys that are into diy will become suspects.... ;D
yeah, since it was brought up here, could you give us a name please?
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It's kinda hard nga lang for us who don't have the background nor the schooling, coz we have to really catch up and learn as much as we can, in my opinion. But nevertheless necessary.
if you paid carefull attention to your physics class in high school and in college, uderstanding tubes should not be that hard..... ;D
and these days, we have the internet and you can find anything you want to know with just a few mouse clicks and keyboard typing.... ;D
i am of the belief that the tube art should not be lost, it is up to the younger generation to pick up, as we are no longer young, and in a few years will be gone......
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Soory, I am not very good with computor websites, so I'm not sure where to post this question. I recently bought a used Cayin A70-T off of e'bay, and have loved it. Now the bad news...today the amp just quit working. no blown fuse, no bad conn. at the power cord iec conn, no bad rectifier tube! I tried these things one at a time, and no good. I did wonder if all the tubes need to be plugged in, as I only had the rectifier tube plugged in when I swapped to another tube. I did take the bottom cover off, just to look and see very impressive work inside. Nothing appeared to be burnt or loose. Now if I can find a place to buy a service manual, then there is a tech nearby that would be able to at least trouble shoot this problem. So, is there any place that I can get ahold of a service manual?
Thx in advance, Greg
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1. Which version of the A-70T did you get. Is it the Autobias model with the switch to changed from Kt88 to El34 ?, if not you would need to changed the BIAS if you swap tubes otherwise something can go wrong...
2. What tubes were there initially ?
3. what tubes did you put in ?
4. Don't tell me you swapped tubes w/o turning it off ?
I did wonder if all the tubes need to be plugged in, as I only had the rectifier tube plugged in when I swapped to another tube
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Thx for your response. what I meant was that I took the tubes out of the amp before turning it over to remove the bottom cover. Then I only put the new rectifier tube back in to see if the amp would work. Nothing happened. But I wonder if all the tubes need to be plugged in in order to light the power indicator(actually, I doubt it, but just wanted to make sure). So, at this point, a service manual is the best step for a tech to trouble shoot this problem. I was just hoping there might a simple fix for the problem before getting too involved in an 'autopsy'.
thx again, Greg
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Thx for your response. what I meant was that I took the tubes out of the amp before turning it over to remove the bottom cover. Then I only put the new rectifier tube back in to see if the amp would work. Nothing happened. But I wonder if all the tubes need to be plugged in in order to light the power indicator(actually, I doubt it, but just wanted to make sure). So, at this point, a service manual is the best step for a tech to trouble shoot this problem. I was just hoping there might a simple fix for the problem before getting too involved in an 'autopsy'.
thx again, Greg
You mean you turn on the amp with the rectifier tube only? If your A70T is not autobias, All the tubes should be back in there original place before you turn it on.
If all the tubes where back in thier original place and you replaced the old rectifier tube with the new tube, maybe the new rectifier tube is busted.
Cheers
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Thanks for the suggestion. Even as I tried it, there was still no power. The day that it happened, i.e. when the amp died, there was a failure in the city power system. The electrical system tried to reset itself 4 four times before it came back up for good. I can only imagine how many other devices in town that were affected! So, it seems that after tying these different simple tests, it may well be time to take the A70 in for service. A service manual would be very helpful to the tech, and I wish I could find one available. Any suggestions? Greg
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I would assume its the power supply... Check if theres a busted fuse, any competent tech with experience in repairing tubes should be able to fix the problem.
You can try to get in touch with Audio Amplified or your nearest Cayin Dealer in your area
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I have left a message for Steve at VAS here in the US, and hopefully he will be able to get a service manual for me. And yes, I agree, it is the power supply that I suspect most. The fuse is good, the rectifier tube is fine, and the ac conn is good to the amp., so next, we will have to 'go inside'. I'll keep you posted, and thx! Greg
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Soory, I am not very good with computor websites, so I'm not sure where to post this question. I recently bought a used Cayin A70-T off of e'bay, and have loved it. Now the bad news...today the amp just quit working. no blown fuse, no bad conn. at the power cord iec conn, no bad rectifier tube! I tried these things one at a time, and no good. I did wonder if all the tubes need to be plugged in, as I only had the rectifier tube plugged in when I swapped to another tube. I did take the bottom cover off, just to look and see very impressive work inside. Nothing appeared to be burnt or loose. Now if I can find a place to buy a service manual, then there is a tech nearby that would be able to at least trouble shoot this problem. So, is there any place that I can get ahold of a service manual?
Thx in advance, Greg
Hi Greg,
you can try replacing the power cord if that is the detachable type, maybe it was dislodged when you turned it over, else try a different outlet....
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different outlet in a different room.. it could be the circuit breaker.. or at least try to plug something else in the same outlet and check it that equipment works
Hi Greg,
you can try replacing the power cord if that is the detachable type, maybe it was dislodged when you turned it over, else try a different outlet....
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different outlet in a different room.. it could be the circuit breaker.. or at least try to plug something else in the same outlet and check it that equipment works
yeah, good idea....
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WELL, I FOUND THE PROBLEM! Not exactly where I would have searched first. There was a defective connection in the fuse receptacle, and I recrimped it. Now the problem is fixed. Who ever would of thought...but thanks to a good vom, and a step by step approach to the problem, the reoccuring test result from the EIC socket led me to investigate what looked to be a perfectly connected fuse holder. Anyway, what a relief. Can you imagine the cost of time and shipping for such a small problem? Well guys, back to the 'musyc', and thanks to all for the support! One note for future reference; the power indicator will light on this unit even if there are no tubes plugged in(even the rectifier tube). cheers, Greg
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were you using quick connects and does the fuse have spades? good job! ;D
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Thx! Thats just it, all conn were factory soldered, no quick conn. And the fuse is just the regular type cylinder shape. No spades, just the fuse holder was not making contact with the crimped conn from the factory part. This part is defective from the supplier, not done by Cayin themselves. I just feel lucky....now, back to the musyc.....Greg