Problem AN Kit One: Noise on Output Transformers

190.163.28.94

Posted on May 21, 2015 at 10:22:46

beto1
Audiophile

Posts: 643
Joined: March 12, 2005

I have noise in the output transformers when I play very low frequencies at high volume on my integrated 300B SET amp (AN Kit One, 2004 version).
I have installed a pair of rubber stripes down the output transformers to eliminate any posible mechanical vibration, I have tightened all the screws that compress the laminations and fix the shrouds. I made recently a complete upgrade on the PSU board, replacing all the caps and resistors. But still the noise is there.

One thing caught my attention; when this noise happens, there is a variation on the filament glow, the more the music is high volume/low fq, the more intense is the glow. I was noted this when the problem appears some years ago and now I can confirm as part of the analysis. Varies exactly in the same "intensity" than the music intensity. The noise is like there something inside the tx that is hitting the output tx shrouds. Tiny hits on a rhythmic basis, directly related with the "over saturation" on the music. The frecuency of this tiny hits is the same all the time. The same quantity of hits per time unit.
Since a long time, I am doing a research on the web and the more difficult task is get the appropriate name to this phenomenon to search an appropriate posible solution. Buzzing, motorboating, oscillation, to name a few, but still I don't find the exact match and how to cure it. I believe that the rubber stripes under the output tx helps in a small degree, by the way.
Since I don't know if the variation on the intensity of the filament glowing is normal when the music tends to sound full and complex at high volume, I can't discard that maybe the problem is some kind of gas leaking inside the output tubes or a mechanical problem inside them that is transported to the output transformers, etc.
One explaination I received earlier was "this is that there is some airgaps on lamination and the electromagentic flux generated by the current flow, activate this with vibrations"...but I'm sure that this was not there the 7 years before, so in some point this begins to happen.

At least I can hear music because this noise is only happens with very low frequencies. Those frequencies are not present on orchestral, acoustic instruments music, traditional jazz, rock, blues, folk, etc, and the maybe 90% of the music that I normally hear but there are some electroacoustic music, noise music, experimental music, etc. that can have a huge degree of very low fq.
Any clue will be gratefully received.
Regards

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RE: Why you can't get a good answer

Russ57

15:24:26 05/22/15

damage to the tx /tubes

beto1

08:42:30 05/23/15

RE: damage to the tx /tubes

Triode_Kingdom

12:31:08 05/24/15

...

Show full thread outline!

RE: Why you can't get a good answer

Russ57

15:24:26 05/22/15

damage to the tx /tubes

beto1

08:42:30 05/23/15

RE: damage to the tx /tubes

Triode_Kingdom

12:31:08 05/24/15

RE: damage to the tx /tubes

beto1

15:12:59 05/24/15

RE: damage to the tx /tubes

Caucasian Blackplate

10:50:34 05/23/15

RE: Why you can't get a good answer

Caucasian Blackplate

20:30:48 05/22/15

Agreed

beto1

16:28:30 05/22/15

+1 (nt)

Tre'

15:33:39 05/22/15

"when I play very low frequencies at high volume"

Awe-d-o-file

11:34:04 05/22/15

RE: "when I play very low frequencies at high volume"

beto1

11:47:46 05/22/15

RE: "when I play very low frequencies at high volume"

Caucasian Blackplate

13:47:20 05/22/15

RE: "when I play very low frequencies at high volume"

beto1

14:18:50 05/22/15

RE: "when I play very low frequencies at high volume"

Awe-d-o-file

19:07:29 05/22/15

RE: "when I play very low frequencies at high volume"

beto1

08:02:42 05/23/15

RE: "when I play very low frequencies at high volume"

Awe-d-o-file

14:00:17 05/26/15

in agreement! (nt)

beto1

15:00:54 05/26/15

Everyone is guessing

Triode_Kingdom

08:09:04 05/22/15

RE: Everyone is guessing

beto1

08:27:00 05/22/15

Normal Behavior

Triode_Kingdom

15:20:32 05/22/15

RE: Normal Behavior

beto1

15:57:02 05/22/15

RE: Everyone is guessing

Tre'

08:45:48 05/22/15

RE: Everyone is guessing

Caucasian Blackplate

09:43:53 05/22/15

RE: Everyone is guessing

beto1

11:48:59 05/22/15

RE: Everyone is guessing

Caucasian Blackplate

13:57:50 05/22/15

RE: Everyone is guessing

beto1

14:03:30 05/22/15

RE: Everyone is guessing

Caucasian Blackplate

14:09:07 05/22/15

RE: Everyone is guessing

beto1

09:09:43 05/22/15

Won't have to guess long

Chip647

08:17:45 05/22/15

Here is the problem

Chip647

07:50:30 05/22/15

RE: Here is the problem

beto1

08:19:56 05/22/15

RE: Here is the problem

Chip647

08:49:23 05/22/15

RE: Problem AN Kit One: Noise on Output Transformers

sv572-10

13:08:43 05/21/15

RE: Problem AN Kit One: Noise on Output Transformers

sv572-10

05:18:31 05/23/15

RE: Problem AN Kit One: Noise on Output Transformers

beto1

14:25:35 05/21/15

RE: Problem AN Kit One: Noise on Output Transformers

sv572-10

01:13:06 05/22/15

RE: Problem AN Kit One: Noise on Output Transformers

beto1

06:19:47 05/22/15

RE: Problem AN Kit One: Noise on Output Transformers

Tre'

08:51:03 05/22/15

RE: Problem AN Kit One: Noise on Output Transformers

beto1

09:12:37 05/22/15

RE: Problem AN Kit One: Noise on Output Transformers

Tre'

10:19:58 05/22/15

RE: Problem AN Kit One: Noise on Output Transformers

beto1

11:37:12 05/22/15

RE: Problem AN Kit One: Noise on Output Transformers

Tre'

12:48:34 05/22/15

Don't you think that 0.22uf and 330,000 ohms and driving a 300b hard is a pretty obvious problem?

Chip647

12:26:24 05/22/15

RE: Don't you think that 0.22uf and 330,000 ohms and driving a 300b hard is a pretty obvious problem?

Tre'

12:46:08 05/22/15

Yes (nt)

Chip647

19:24:14 05/22/15

RE: Don't you think that 0.22uf and 330,000 ohms and driving a 300b hard is a pretty obvious problem?

beto1

14:13:59 05/22/15

RE: Problem AN Kit One: Noise on Output Transformers

Paul Joppa

13:06:29 05/21/15

RE: Problem AN Kit One: Noise on Output Transformers

beto1

14:21:18 05/21/15

RE: Problem AN Kit One: Noise on Output Transformers

Tre'

10:42:08 05/21/15

RE: Problem AN Kit One: Noise on Output Transformers

beto1

10:50:00 05/21/15

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 21, 2015 at 10:42:08
Tre' Industry Professional Posts: 17294 Location: So. Cal. Joined: February 9, 2002	Doesn't the sound from the speakers drowned out the sound coming from the transformer? Tre' Have Fun and Enjoy the Music "Still Working the Problem"

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 21, 2015 at 10:50:00
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Hi Tre' it is noticeable even at high volume (not like a concert hall, btw) because the characteristics of the noise. It is on the high fq spectrum...exactly as if you hit with the tip of a nail the transformers shrouds repeatedly.

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 21, 2015 at 13:06:29

Paul Joppa
Industry Professional

Posts: 7295
Location: Seattle, WA
Joined: April 23, 2001

Very low frequency at high volume means the transformer core is probably saturated at current peaks, and the tube is probably clipping - cut off at zero current for a portion of the waveform, and/or drawing excessive current for a different portion of the waveform.

There are many possible consequences that might result in high-frequency noise. It was not completely clear, but I think you are saying the noise emanates from the transformer itself? If so, then when the tube goes to zero current the transformer is unloaded so large voltage spikes are a possibility. Transient oscillation of the tube, or internal arcing, are other possibilities. Or, when the current is excessive, the transformer saturates and the load on the tube drops very low. There are many more.

Driving the tube beyond its functioning, more or less linear range could easily affect the filament power - excess current draw will cool the cathode by evaporation of electrons for instance.

The solution is to avoid driving the tube or transformer beyond their functional frequency and voltage range. :^)

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 21, 2015 at 13:08:43
sv572-10	It could be core saturation. At very very low frequencies a transformer can easely saturate and specially at high volumes.

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 21, 2015 at 14:21:18

beto1
Audiophile

Posts: 643
Joined: March 12, 2005

Hello Paul,
thanks for answer me.
Yes, the noise appears to be from inside the transformers. It is something like is hitting from the inside the tx shrouds, on one rhythm.
As far as I can understand from your answer, it is a normal behaviour on such heavy playing conditions, with low fq at high volume or high dynamics with a crescendo, for example into a musical source. This put the trafo into the point of clipping.
Since I can't recall that this happened before this last 3 years, do you think that this is normal due a poor quality trafo or this is a general law? maybe an exhausted output tube? but this last option is not too much probably because the rest of the"normal" music sounds very good.
regards

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 21, 2015 at 14:25:35
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Hello sc572-10, and this is a normal behaviour, no matter the quality of the output trafo? There is a cure for this, without censoring the music I hear? regards

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 22, 2015 at 01:13:06
sv572-10	If the transformer design is better the problem would be less but it helps a lot to filter out the lowest frequencies (<15Hz). In normal acoustik musik there are no sub bass frequencies except organ.

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 22, 2015 at 06:19:47
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Hi, yes indeed, regular acoustic music are on the border of 40 Hz. What do you mean with filter from below 15Hz? something like a high pass filter? If is that, I would have to think if it's good thing to filtering the audio signal, which is opposed to the concept of an amplifier like this, I guess. Regards

Here is the problem, posted on May 22, 2015 at 07:50:30

Chip647
Audiophile

Posts: 2649
Location: The South
Joined: December 24, 2012

Usually one designs an amp that will have the tube be the weakest link. When you over-drive the amp, you will drive the tube itself into saturation rather than other any specific part on the amp. Your amp's output transformers do not have the headroom to allow your 300B to be over-driven. That is OK. You are dealing with a 6 watt amp and you have to expect that you will not have the power to do everything a 1000 watt solid state amp can do.

The fix is to get OPTs with +120mA current capability before saturation. Getting OPTs that sound as good as yours but having the higher current capability are expensive and large and will not likely fit in your amp. Accept your fate. Better yet, get an electronic crossover and a sub so you can party on to all the EDM you can handle.

Everyone is guessing, posted on May 22, 2015 at 08:09:04

Triode_Kingdom
Audiophile

Posts: 10042
Location: Central Texas
Joined: September 24, 2006

Every answer you've received so far is a guess based on assumptions about what you're hearing. This really isn't something that can be remotely diagnosed. If my amplifier were doing something odd like that, I'd want to know immediately if continuing to use it might cause expensive damage. My suggestion is that you take it to a shop so they can determine whether this is a component failure or just a normal limitation of the amp.

Won't have to guess long, posted on May 22, 2015 at 08:17:45
Chip647 Audiophile Posts: 2649 Location: The South Joined: December 24, 2012	Eventually the arching will cause a short then everything will get really quiet.

RE: Here is the problem, posted on May 22, 2015 at 08:19:56

beto1
Audiophile

Posts: 643
Joined: March 12, 2005

hello Chip,
well, the higher graded Audio Note OTx has the same standing current of 90mA than my 152 model Tx.
Maybe there is an influence of the magnetic material of the shrouds that create a short out the air gap when saturation starts.
I realized a moment ago that on the AN web site, they adivise to use copper shrouds on their higher grade tx because:
"the copper shroud being non-magnetic improves not only RF influx, but also low level behaviour as it does not short out the airgap on the higher permeable cores like the AN Ultra HiB and the nickel cores this is essential for optimal performance".
This sentence took my attention because as I have stated on my first post, one explanation was (from AN, btw a year ago) "this is that there is some airgaps on lamination and the electromagentic flux generated by the current flow, activate this with vibrations"
Regards

RE: Everyone is guessing, posted on May 22, 2015 at 08:27:00
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Hello Triode Kingdom, thanks for your advise. According to the manufacturer this is a normal behaviour. But I am a bit sceptical and nonconformist, so I am trying to get some inputs from the collective experience, because maybe there is some little mod that can fix this "normal" problem. Regards

RE: Everyone is guessing, posted on May 22, 2015 at 08:45:48

Tre'
Industry Professional

Posts: 17294
Location: So. Cal.
Joined: February 9, 2002

"...maybe there is some little mod that can fix this "normal" problem"

Single ended output transformers have limited inductance.

My guess is the "mod" would be to limit the low frequency arriving at the output transformer with a high pass filter somewhere in the signal path or limit the amplitude of the signal as a whole by simply turning the volume control down.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

RE: Here is the problem, posted on May 22, 2015 at 08:49:23
Chip647 Audiophile Posts: 2649 Location: The South Joined: December 24, 2012	A 300b can sit at 90mA, right at the saturation point. And despite the Class A, when they are thumping bass they will go above.

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 22, 2015 at 08:51:03
Tre' Industry Professional Posts: 17294 Location: So. Cal. Joined: February 9, 2002	SE output transformers have limited inductance. Filtering out the lowest frequencies will make the rest of the music sound better (less harmonic distortion). Tre' Have Fun and Enjoy the Music "Still Working the Problem"

RE: Everyone is guessing, posted on May 22, 2015 at 09:09:43
beto1 Audiophile Posts: 643 Joined: March 12, 2005	well, the second choise is not going to fix the problem. There is no need to have too much volume to saturate the ooutput transformers, but a high dynamic on the music with full fq. I will think on the first choise. Thanks for the advice. So, this is a regular behaviour of this kind of amplifiers with a given music, uh?

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 22, 2015 at 09:12:37
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Ok, I will do some research on this point, independent that I think is contrary to the philosophy of AN. Do you have any recommendation about this high pass filter? regards

RE: Everyone is guessing, posted on May 22, 2015 at 09:43:53
Caucasian Blackplate Industry Professional Posts: 8313 Location: Seattle Joined: June 18, 2004	How about using a compressor ahead of the amp?

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 22, 2015 at 10:19:58

Tre'
Industry Professional

Posts: 17294
Location: So. Cal.
Joined: February 9, 2002

Just a cap will do.

I don't know which schematic you have but changing the .22uf cap that feeds the 300b to a .022uf cap will increase the frequency of the high pass filter from 2.2Hz to 22Hz

That might do it.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

"when I play very low frequencies at high volume", posted on May 22, 2015 at 11:34:04
Awe-d-o-file Dealer Posts: 21037 Location: 50 miles west of DC Joined: January 10, 2004	You should really turn that statement from vague to actual measured numbers in hertz and watts. E T ET "If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 22, 2015 at 11:37:12
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Yes the scheme is similar Interesting. Have you done something like that on your amp? An what about the C9/C8 that is related to the potentiometer? has the same value.

RE: "when I play very low frequencies at high volume", posted on May 22, 2015 at 11:47:46
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Hi, Thanks for your answer. yes, I'm agree , in an ideal world. But I don't have a laboratory and my question is to mates that can know this phenomenon that seems to be common with 300B SET amp like mine as even the manufacturer give the same explanation. Regards

RE: Everyone is guessing, posted on May 22, 2015 at 11:48:59
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Hello, can you elaborate a little more, please?

Don't you think that 0.22uf and 330,000 ohms and driving a 300b hard is a pretty obvious problem? , posted on May 22, 2015 at 12:26:24
Chip647 Audiophile Posts: 2649 Location: The South Joined: December 24, 2012	Just drop the grid resistor to 100K and you may fix 2 problems.

RE: Don't you think that 0.22uf and 330,000 ohms and driving a 300b hard is a pretty obvious problem? , posted on May 22, 2015 at 12:46:08

Tre'
Industry Professional

Posts: 17294
Location: So. Cal.
Joined: February 9, 2002

What problem?

Edit; I'm guessing that when grid current is drawn the cap will charge and then the bias will take a long time to recover?

I think beto1's biggest problem is that his speakers are not efficient enough for a SE 300b amp.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 22, 2015 at 12:48:34
Tre' Industry Professional Posts: 17294 Location: So. Cal. Joined: February 9, 2002	Yes. I have a .003535uf cap feeding a 330k ohm grid resistor of the input stage to limit the LF at 136Hz. This is in a bi amp system. There is a SS amp driving the woofers. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

RE: "when I play very low frequencies at high volume", posted on May 22, 2015 at 13:47:20
Caucasian Blackplate Industry Professional Posts: 8313 Location: Seattle Joined: June 18, 2004	Put a 60Hz tone into the amp and measure the AC voltage coming out of your amp with a multimeter. The $10 of tools necessary for this will give you a lot of information.

RE: Everyone is guessing, posted on May 22, 2015 at 13:57:50
Caucasian Blackplate Industry Professional Posts: 8313 Location: Seattle Joined: June 18, 2004	A compressor could be used to lessen dynamic peaks a bit, which may help.

RE: Everyone is guessing, posted on May 22, 2015 at 14:03:30
beto1 Audiophile Posts: 643 Joined: March 12, 2005	thanks for your answer. also a compressor will kill the music in the way that comes from the source. I am more on the road to leave it in the way it was now or maybe convert the bypass caps into a high pass filter...a more natural solution, I think. regards

RE: Everyone is guessing, posted on May 22, 2015 at 14:09:07
Caucasian Blackplate Industry Professional Posts: 8313 Location: Seattle Joined: June 18, 2004	Compression is used on many (I'd go as far as to say most) recordings already. You won't need much.

RE: Don't you think that 0.22uf and 330,000 ohms and driving a 300b hard is a pretty obvious problem? , posted on May 22, 2015 at 14:13:59
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Tre', if the speaker's efficiency is related in that way with this noise, you are right. I have a 91dB speaker that sound well on a medium size listening room, but not an ideal match for a low powered SET amp. I must to be very honest: I am one step behind your explanations; my electronic knowledge is very limited, so with every answer opens a new path to research for me. regards

RE: "when I play very low frequencies at high volume", posted on May 22, 2015 at 14:18:50
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Thanks for the input. sounds like something that I will do soon.

Normal Behavior, posted on May 22, 2015 at 15:20:32
Triode_Kingdom Audiophile Posts: 10042 Location: Central Texas Joined: September 24, 2006	"According to the manufacturer this is a normal behaviour. " Didn't you say this is relatively recent, that the amplifier didn't do this in the past? That doesn't sound normal to me. Has the manufacturer examined the amplifier?

RE: Why you can't get a good answer, posted on May 22, 2015 at 15:24:26

Russ57
Audiophile

Posts: 3754
Location: South Florida
Joined: November 16, 2001

A given amp has a limit to how many watts it can put out. Depending on the amp it may have the ability to briefly handle a larger "peak" wattage....or it may not.

SET amps often don't have much extra peak power and typically aren't well suited to low bass.

Certain types of music have limted dynamic range. This means much of the music places the same demand on the amp. Other types have much larger dynamic ranges. If you want to listen to this type of music you need a much more powerful amp.

For an amp to play music which reaches your ears at a certain degree of volume several things interact. Amplifier power, distance from speakers, how efficent the speakers are, etc.

So without us knowing amp power, music dynamic range, what hertz and dB gives the problem, how far you sit from speakers, how efficent the speakers are, the impedance plot of the speakers at the hertz where amp acts up, etc., etc., ETC.. Well then we simply can't help much.

From all that you have said it would be easy to "suggest" that you have the wrong amp/speaker combo for the type of music and volume you seek to reproduce. However that would be little more than an educated guess.

Perhaps an easy test might be to rent an active crossover and borrow a solid state amp. Have the 300B amp only play music above a 100-200 hertz and route the rest through solid state amp of at least a couple/few hundred watts. That would require speakers that allow bi-amping....or better yet add speakers just for low bass.

Frankly I was never happy until I had speakers (for the tube amp(s)) that were 100dB/watt or better (think horns) and routed lower bass through solid state amp(s) and then to a pair of 12" to 15" speakers per side. Basically you want to use pro-audio drivers for the speakers....drivers that are rated to handle 5...10...20 times the wattage you need to throw at them to get the volume you want.

And if you really want to do justice to stuff under 60-80 hertz range....and you like your music loud (105-110dB+)....don't be surprised to find you need 400 to 1,000 solid state watts. To think a 6 watt SET can do it with 91 dB speakers....well, that just isn't happening my friend (in fact you are likely doing your amp/tubes serious harm). IMHO 91dB speakers aren't suitable for most tube amps....let alone almost all SET amps.

+1 (nt), posted on May 22, 2015 at 15:33:39
Tre' Industry Professional Posts: 17294 Location: So. Cal. Joined: February 9, 2002	. Have Fun and Enjoy the Music "Still Working the Problem"

RE: Normal Behavior, posted on May 22, 2015 at 15:57:02
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Hello, thanks for your answer, I built this amp about 10 years ago and I beginning to note this since about 3 years, before that I did not noticed, but since 3 years I have rationalized the phenomenon, I can't be sure because if the noise was there before. I talk to the manufacturer several times. Maybe I am on an small statistics % with some of the music I hear. regards

Agreed, posted on May 22, 2015 at 16:28:30

beto1
Audiophile

Posts: 643
Joined: March 12, 2005

Hey, thanks. I'm agree, of course.
My next project is a HEff horn speakers set, by the way. A long postponed project due to the cost and the time that take the research and design.
Harm to my amp? because of the over-saturation on the OP Tx?
I started this thread knowing that from the manufacturer point of view this is normal, but I guess not dangerous to my amp/tubes as they never warned me about . He talked to me about a few examples of amps with the same OP tx doing exactly the same rattle than mine. I'm only trying to expose this topic to a more exhaustive revision on this forum, engaging the community experiences.
Thanks for sharing yours.
Regards
p.s. I will ask locally to some folks on how to do some rigorous measurements, to the same thing with some numbers on the table.

RE: "when I play very low frequencies at high volume", posted on May 22, 2015 at 19:07:29
Awe-d-o-file Dealer Posts: 21037 Location: 50 miles west of DC Joined: January 10, 2004	You can download a free signal generator piece of software, there are several on the net. E T ET "If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

Yes (nt), posted on May 22, 2015 at 19:24:14
Chip647 Audiophile Posts: 2649 Location: The South Joined: December 24, 2012

RE: Why you can't get a good answer, posted on May 22, 2015 at 20:30:48
Caucasian Blackplate Industry Professional Posts: 8313 Location: Seattle Joined: June 18, 2004	I agree, it wasn't until I put two 18" woofs in crossover over at 55 Hz and under that I really got everything I wanted out of the bottom end from my system with only 8 Watts per side.

RE: Problem AN Kit One: Noise on Output Transformers, posted on May 23, 2015 at 05:18:31

sv572-10

On second thought..... It is probebly not core saturation.

Because the transformer is 2500 Ohm at large low frequency signals the tube will cutoff itself first, before there is core saturation. If you look at the signal with a oscilloscoop one half of the sinus will be cutt off and the other half not. There is simply no current through the tube anymore at large signals.

It still helps to filtering out the low frequencies but you are at the limit of the tube/ transformer combination.

RE: "when I play very low frequencies at high volume", posted on May 23, 2015 at 08:02:42
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Thanks for the input. I will take a look around on the web. I was out of the hobby for several years, only enjoying music. From the last year I'm coming back, slowly, looking for a little time to build a pair of H Eff speakers. It is always positive to come back to the audio asylum. Regards

damage to the tx /tubes, posted on May 23, 2015 at 08:42:30

beto1
Audiophile

Posts: 643
Joined: March 12, 2005

Hi Russ57,thanks for your explanation. Your post appears as deleted, btw. I rescued it from my email.
"The transformer has stored a field that would like to oppose these changes. Under conditions of tube cuttoff/no current that field would like to produce an unlimited voltage to attempt to keep a current draw happening. This could cause a failure in the insulation of the transformers and ruin them. At maximum current draw you run the chance
of running your 300B's way above their current ratings and greatly reducing tube life."
This insulation failure happens with a huge increase on the trafo temperature while it is oversaturated? As far as I remember, always they are running at a low temperature.
My amp sounds very well, but your comment provoke me a little doubt about the health of the insulation on my pair of tx, how can I check if the insulation is still in perfect shape? or when this insulations fail, just kills the trafo and there is no more sound?
Also thanks for your advises about speakers.
I was researching on Lowthers and on 3 way systems, like the derivated from klipsch horns (Crites and others) or similars or maybe the 2 way duplex derivated from Altec 604 GPA, -. Drivers like you mention and a lot more like BMS,Beyma, etc, Volti horn,etc and several projects associated to them are under my sight now.
thanks again

RE: damage to the tx /tubes, posted on May 23, 2015 at 10:50:34
Caucasian Blackplate Industry Professional Posts: 8313 Location: Seattle Joined: June 18, 2004	The DCR across the primary of the output transformer will measure lower than it should if the insulation breaks down.

RE: damage to the tx /tubes, posted on May 24, 2015 at 12:31:08

Triode_Kingdom
Audiophile

Posts: 10042
Location: Central Texas
Joined: September 24, 2006

"Under conditions of tube cuttoff/no current that field would like to produce an unlimited voltage to attempt to keep a current draw happening. This could cause a failure in the insulation of the transformers and ruin them."

The voltage of the collapsing field is controlled (limited) by energy transferred to the speaker. This is why tube amplifiers in general should only be operated with a load attached. I wouldn't be concerned about the above scenario unless you've violated this rule.

RE: damage to the tx /tubes, posted on May 24, 2015 at 15:12:59
beto1 Audiophile Posts: 643 Joined: March 12, 2005	Not at all, every time I have my amp on my work bench is connected to a pair of apeakers and a source. When is placed on the living room, of course the same thing. thanks

RE: "when I play very low frequencies at high volume", posted on May 26, 2015 at 14:00:17
Awe-d-o-file Dealer Posts: 21037 Location: 50 miles west of DC Joined: January 10, 2004	Should be a fun thing to check that out, welcome back to AA. Remember have fun should be near the top of your list! E T ET "If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

in agreement! (nt), posted on May 26, 2015 at 15:00:54
beto1 Audiophile Posts: 643 Joined: March 12, 2005	.

Tube DIY Asylum

Problem AN Kit One: Noise on Output Transformers

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