GoodSoundClub - Romy the Cat's Audio Site

Melquiades Amplifier
Topic: Hm... yes and no....

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Posted by Romy the Cat on 08-14-2009

I did not play my playback since Sunday and turned it last night after 4 days not being off. It was very pity sound. Even I felt that it was getting better after 2 hours I shut down the system as I has other things to do.

In the past I have mentioned that Melquiades, as many other amps, need time to heat up to build up own default sound and that 3-4 non-operational days it require 3-4 hours of containing burning to return back to its proper sound.

http://www.romythecat.com/Forums/ShowPost.aspx?postID=2201

I have no definitive idea if to attribute it to tubes, caps or anything else, anyhow this is not the subject.

What I think now is if it possible to design an amp with the notion of pre-warming intrinsically built in? It is too late for Milq as it uses full-voltage delay circuits. Be let look what BAT did in 90s with this preamps – they had filaments are raring in a very low voltage in a stand-by mode in order to prolong the life expectancy the tubes. I do not care about the life expectancy but how about to play the very same concept to cure the need of an amp to be pre-formatted for it’s best operation?

Pretend we have a SET amp with no regulators; most of the SET are not regulated. Then pretend that in front of the amp, before it primaries of the power transformers we have another 6:1 power transformer that constantly feeds the amp with 20V. Let call it Lead Transformer. Now all magnetics, diodes, caps, filaments, breeder, the whole circuitry is slightly heated by the 1/6 of the voltage. It does not take a lot of power and in case of Milq for instance the gas regulators will not do off, still the bias circuits will be under the voltage as gas regulators are shunt regulators.

Now I wish to run the amp. All that I do is shorting the primary and secondary of the Lead Transformer, allowing the full wall voltage to drive the amp. I think it might be a good solution and I do not know why it is not being used, at least I never have seen and I never heard people even talk about it (in SET environment). Certainly it is not something that I would propose at $1000 amps. However if people buy $50K or $100K amps (that presumably deliver better sound) then would it make sense to demand the pre-warming feature are mandatory? If to presume that Melquiades sounds like $100K amp then after 4 non-operational days it sounds flat like $500 amps or as a dog that just walked under rain. It also sounds not as it shall for the first 30-40 minutes, but this is how most of tube amps behave….

What I wonder is the electronics incidents that we use in amps have any problem to work continually under a fraction of normal operation voltage. I know that some expanse SS amps use this concept but I never have seen any SET power amps to go there…

Rgs,
Romy the Cat

Posted by Axel on 08-14-2009

Romy,
do not spit in my eyes as I do have solid state PassLabs 350.5 but even with this 50W Class A amp (push pull) it is exactly the same problem if it is switched off completely even for a short while. I can take ~ 2 - 3 days to be back to normal if it was COMPLETELY switched off.

In the case of Pass, it uses a stand-by switch in front (main power-off in back) and will keep the power-supply's electrolytic capacitor bank charged.

In the case of power down to stand-by the amp is fully back ~ 1/2 hr. after being switched on.

I know tubes are more involved, I also know BAT preamp behaviour. I think first is to keep the power-supply caps charged and second (~ maybe...) to run very low heater current which I think you mentioned - but it is the capacitors in the power-supply that in my estimate cause the much bigger problem when allowed to get fully discharged.
Axel

Posted by Romy the Cat on 08-14-2009

Yes, I do think that the caps in here are the key but there is a twist in it. The “formatting “or burning- in of capacious is a polarization of dialectic, with time the dialectic got charged and “sounds” better. Also the dialectic is mechanically stressed and become less “loose”, minimizing the electro-mechanical distortion. In the past I modified my Milq and made the big B+ caps disconnected when amp is off. Since the caps are good they then can hold the charge for days. So, disconnected load and bleeder and made the caps to sit with voltage. Then what I want to turn the amp of I bleed the caps while I heat filaments and only then connected the load. It was slightly better but it was not the same as run the amps. So, what I concluded is that caps, while they are being formatted, want to see the AC (residual ripple). I presume that what when a cap is shorting the residual AC to ground then the dialectic is “shaking” with the AC and hard-bias with DC. If there is no AC from rectifier then dialectic is bias but with no AC there is no shaking effects and the dialectic is less strongly “oppressed”. It might be a foolish explanation but it is all that I have.

The Cat

Posted by Paul S on 08-14-2009

Was it my old Audible Illusions pre-amp that kept lower voltage on all the time? But I was worried about constant 20% power causing constant 20% plate dissipation on my expensive NOS tubes, so I tested it and wound up unplugging it most of the time. In that case, it took 20 minutes to warm up to cruise speed off the 20% idle and an hour or so to come up from cold, at least as [often] I was using it at that time.

The ML2s have been "funny", taking 20 minutes to not be bad and another 25 minutes or so to start getting good, if I play them often. But if I leave them down for a while, it might take 4 or 5 hours for them to get good.

As someone who still suffers the Bad Electricity, I have noticed that warm up time is quite a bit shorter on occasions when electricity is good, FWIW.

Oddly. sometimes the amps improve from 20 minutes to an hour in and then they start getting worse again. I think the PS people once added a "de-gausing" feature on one of their power conditioners specifically to address this, or something like it.

Paul S

Posted by Romy the Cat on 08-14-2009

Paul S wrote:
But if I leave them down for a while, it might take 4 or 5 hours for them to get good.

Yes, it is exactly it. It is OK during the winter - sometimes run the power amps for days, but during the summer to run all 12 Milq’s channels for 4-5 hours just to have a decent listening session after a few days of break is kind of sad thing to do. For 5 hours Milq hits the room that I can cook pizza right in the Micro-Seiki platter.

I wonder if it possible to identify and isolate the cause of the problem and to apply a narrow targeted cure. For instance if it is about getting a right temperate in the power capacitors then would it possible to wind heating coils along them with a thermostat and as soon the amp starts and to heat the caps very fast to the default “best sounding temperature”. If it is about the agitating the dialectic then it might be possible to give to the caps the very short “shaking stress”. Perhaps it might be done by a period of operation with removing rectifiers and to driving the caps with AC. Frankly, in such a big and complex amp as 12-ch Milq is I would not mind to have a switch that would temporary activate some like of local burn-in oscillator that would “age” the caps very fast. I wonder if anyone did any research or have any solutions in the felid.

The Cat

Posted by Axel on 08-15-2009

I think what actually happens it that the dielectric, when it gets most fully discharged, simply takes some time again to get 'FULLY' recharged. The perode inbetween will make the loss angle (or power factor) become a lot worse. This means the caps' charge speed gets 'slower'. The bigger the cap, and the worse the initial loss angle, the more pronounced the problem. It would be similar to when an electrolytic cap starts to dry out. Maybe yours already are on this 'road' as they appear to live in a pretty hot environment most of the time.

More lately some (don't know the code right now) Siemens A.G. made electrolytic caps (hi-rel) have become available with a much smaller loss angle when compared with the more usual run of the mill polarized caps, it aught to help in our estimate --- yet there is more.
Since essentially the music signal has to go through these 'storage caps' all the time (therefore the noticeable degradations that may be noticed), it might be worth it to consider using not only just a few 'big' electrolytic to do the job, but make up a 'cap array' of various caps (smaller to bigger values) to reach the desired value. This way the loss angle should be improved, improving power supply’s performance.

Lastly, but I can not confirm this with the power supply caps yet, I have noticed that caps of approximately similar physical size and varying values work better when used in parallel I.E. the higher the Voltage to bigger the physical size matching to a lower voltage bigger value.
The more the physical size differs the more the chance winding up with incoherent sound. I'm sure there is some scientific explanation here, but I would like only to mention this effect I noted when working with foil caps in cross-overs.

Axel

Posted by Romy the Cat on 08-25-2011

Two days ago a local audio guy was visiting me and he was listing most of the day. When I asked him to comment on the playback problems he made insisted that sound has some brightness/harshness “around top E”. That was interesting as I know that it shall not be any problems in the noted region. However, standing behind his listing chair I did concur what he noted.

Now it was kind of fun. Although I admit to myself that he was not wrong but I know that this brightness/harshness was not in my Sound. I knew also that I did not make any change with my playback for a long time. I knew also that even if electricity slide somewhere then it would be other symptoms and I did not recognize those other symptoms in the sound I heard. The sound was fine all together but that very fine “alien” presents was in a way mystifying as I had no idea what it was coming from…

As the time went buy I noted that the brightness/harshness was residing it and in 3 hours it went away completely. The sound returned back to it’s normal state of being soft and spongy. Then it came to me. I recognized that before the visiting of my guy I did not play Macondo/Milq for 2 days - a quite long period in my room. So, apparently Melquiades need some time to bring itself back to the full duty. It is was not the I did not know it but I was under impression that 2 days might be recovered by one hour of hot playing… It turned out that it was not enough.

It would be interesting to learn what kind specific elements of the Melquiades are more vulnerable to that “non-working effect”. Usually we blame capacitors but who the hell know what it is in reality….

Rgs, Romy the Cat

Posted by noviygera on 08-25-2011
fiogf49gjkf0d I notice the same warming up effect on my system, takes a few hours. And I thought... could it be the speakers warming up?

Posted by Romy the Cat on 08-25-2011

noviygera wrote:
I notice the same warming up effect on my system, takes a few hours. And I thought... could it be the speakers warming up?

I tend to think that it is not speakers but electronics. At the upper MF my speakers has metal cone and currents in voice coils that will not be able to electrocute a grasshopper. I do not think that that it is speaker but no one knows for sure. What kind argument would you bring that would move blame from electronics to speakers?

The Cat

Posted by noviygera on 08-26-2011

I have noticed that after playing music through speakers, the sound warms up and becomes more dense and relaxed. It would be an experiment to let the system stay "on" for an equivalent amount of time without playing music through speakers to hear the result. I thought the voice coils and drivers cones warm up and loosen up.

I have made one observation in the winter time in my car. If it's very cold (below freezing), the audio system would sound supremely compressed until the interior warms up, so I assumed the speaker drivers are too stiff when cold.

Posted by unicon on 08-26-2011

Romy the Cat wrote:
noviygera wrote:
I notice the same warming up effect on my system, takes a few hours. And I thought... could it be the speakers warming up?

I tend to think that it is not speakers but electronics. At the upper MF my speakers has metal cone and currents in voice coils that will not be able to electrocute a grasshopper. I do not think that that it is speaker but no one knows for sure. What kind argument would you bring that would move blame from electronics to speakers?

The Cat

There would be for sure some minor changes in electronic and loudspeaker during playback, which is negligible in most situations.
The most changing factor during the playback is the human ear it will try to adapt to the noise coming into it.
Ear wax and change in ear canal diameter during expose of noise do control and help to hear safe sound ...
Rgs

Posted by rowuk on 03-02-2019

We know that speaker surrounds are subject to memory effects. Is not playing the speaker (keeping the voice coils warm and surrounds elastic) not the big part of having to warm up the system?
With power supplies containing modern diodes, caps and resistors, everything is pretty much stable after a couple of minutes. I used to use tube rectification, then it took hours before everything settled down. I dumped that 10 years ago.
Another factor is warming our ears up to playback. We do have short term effects on perception and are ultimately adaptive creatures. It would be difficult to separate our perception from the hardware warm up.

Posted by Romy the Cat on 03-02-2019

For sure the speaker surrounds are working up with practice but it also greatly depending from temperature, humidity and a few other factors. It is indeed very hard to factor everything in, did I mention the electricity? :-)
The warming our ears up to playback is complicated subject. I would not deny it but I would also do not agree with it. To talk about it seriously wee need to be able to factor out all other very objective reasons why the sound of playback is fractures under different conditions and…. unfortunately I do not know any methodologically-proper ways to do it practically.

Posted by rowuk on 03-02-2019

Our hearing is very elastic for everything except phase. We can learn to compensate for errors in frequency response easily. My personal experience with sense of space is also very much an acqired response.
When I listen to my playback after a couple of days of rest, I have a period of acclimation that takes "hours". I recognize tone quickly, but the feeling of integration and space take time. With some programming (older monophonic recordings for instance), I need more time before i can relax.

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