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Low Wattage Tube Amps - 6 Watts enough for La Scalas?


CharlieFromVB

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2 hours ago, richieb said:


Truth be told - (they were both annoying) (I cant believe my fingers typed that)

Almost as annoying as you! 
 

Mookie is a nice guy so he gets a pass, this time.

 

To the OP, the Decware amp will make your La Scalas sing beautifully. Makes my Khorns sound great. 
 

After I sorted them out from being in Richieb's possession.......

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23 minutes ago, richieb said:


No worries. He’s become quite aloof since building his mansion on the beach. I believe hanging with the Forum is well under his new status - 

I think its one of those retirement sex communities!

Shhh, I think hes slumming in the forum. Must be between rounds.

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15 hours ago, tube fanatic said:

Instead of debating how much power is needed, why not measure it?  
 

https://community.klipsch.com/index.php?/topic/170414-who-wants-to-measure-how-much-power-voltage-is-really-needed/

 

That said, I have powered LS systems with as little as 300 milliwatts per channel and it was far more than needed.  
 

 

Maynard

 

A tone, or a sample of pink noise (usually 500 Hz to 2,000 Hz) is, IMO, continuous, not peak.

 

The SPL of a sample of music played as loud as we ever would depends on:

  1.   Mood
  2. The amount of distortion in the recording.  IMO, the more distortion on the recording, and the more noxious the type of distortion, the lower the the preferred SPL, and therefore the lower both the watts and volts.  I guess I'd play the cleanest, least distorted recordings  I have, and select the loudest, if I wanted to know the max amp power and voltage I needed.

I don't have a working multi meter right now.

 

 BUT:

  1. Can it be that the Crown calculator is not working properly right now?  With the Khorn sensitivity re-rated at 101 dB (since Crown probably assumes anechoic chamber measurements, at 2.83V, at 1 M, rather than Klipsch's rating of 105 dB in a typical room ) at 4 meters distance tells me I need 40 watts to produce the 102 dB peaks THX recommends, in my 4,257 cu. ft. room.  I could swear it gave me 6 watts in the past.
  2. Another calculator says that 10 watts will do the job.  That's much closer to what I thought.  Wouldn't that be about 3.16 volts?  That calculator is at: http://myhometheater.homestead.com/splcalculator.html
  3. When I used to have a power amp that had a (supposedly) peak reading meter, once in a while it would reach 25 watts, just for a moment.  I think that would be about 5 volts.

 

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8 hours ago, garyrc said:

 

A tone, or a sample of pink noise (usually 500 Hz to 2,000 Hz) is, IMO, continuous, not peak.

 

The SPL of a sample of music played as loud as we ever would depends on:

  1.   Mood
  2. The amount of distortion in the recording.  IMO, the more distortion on the recording, and the more noxious the type of distortion, the lower the the preferred SPL, and therefore the lower both the watts and volts.  I guess I'd play the cleanest, least distorted recordings  I have, and select the loudest, if I wanted to know the max amp power and voltage I needed.

I don't have a working multi meter right now.

 

 BUT:

  1. Can it be that the Crown calculator is not working properly right now?  With the Khorn sensitivity re-rated at 101 dB (since Crown probably assumes anechoic chamber measurements, at 2.83V, at 1 M, rather than Klipsch's rating of 105 dB in a typical room ) at 4 meters distance tells me I need 40 watts to produce the 102 dB peaks THX recommends, in my 4,257 cu. ft. room.  I could swear it gave me 6 watts in the past.
  2. Another calculator says that 10 watts will do the job.  That's much closer to what I thought.  Wouldn't that be about 3.16 volts?  That calculator is at: http://myhometheater.homestead.com/splcalculator.html
  3. When I used to have a power amp that had a (supposedly) peak reading meter, once in a while it would reach 25 watts, just for a moment.  I think that would be about 5 volts.

 

 


 

 Anything subjective is going to have some variability which is why Pano recommended setting the maximum subjective level by using multiple recordings.  His method, which I have tried in many systems, has been excellent.  Calculators are fine, but can only provide very basic information and guidance.  The thread on DIY is still active after 8.5 years, and should be read in its entirety by anyone interested in actually measuring their equipment.

 

 

Maynard 

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On 7/29/2020 at 7:04 PM, codewritinfool said:

Oh!  Genius idea!  I would buy a wristband that said that and had a little PWK logo on it.

 

I would be afraid to do it, poor example in hindsight. 

 

But calculating and measuring is how Paul would have done it, and did do it, in many peer reviewed journals.

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I'm using a 6 watt amp with my Cornwall IIIs but I feel I could do better on the bass at around 18 -25 watts with a parallel SET or push pull but I'm sticking with SET amps for the moment. However, La Scalas are more efficient and 6-8 watt SET should be fine.

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Six watts should be enough for most listeners using a SET tube amplifier. From experience different 6 watt SET's are different when it comes to bass depending on tubes used. Certainly for bass lovers the more watts a PP (push pull) amplifier will have better bass but sacrificing the sweet mids and highs a SET makes. Of course exceptions to every rule.

Edited by henry4841
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On 8/9/2020 at 7:01 AM, henry4841 said:

From experience different 6 watt SET's are different when it comes to bass depending on tubes used.

 

The output tranformers also have a lot to do with it. My 2a3 amps have Magnequest iron and I get great bass.

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And perhaps power transformers also may make a difference with bass dynamics?  I don't know, just speculating.

 

Also, a person who was banned from this forum, but very bright and well informed, maintained that warm-up time was important for power transformers.

 

 

 

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Both Marvel and gayrc are correct. OPT's especially in SET's are considered important and you do need a power transformer large enough to supply the energy for bass response along with enough capacitance to store the power to be released. I have found Edcor OPT's to be excellent OPT's. Just be sure and order the ones that go low in the frequency range. The range is stated in specifications. 

 

I think when talking about warm up time is the rectifier tube being used. Unless you have some limiter in the power being feed to the transformer they are either on or off. Some rectifier tubes have longer warm up times than others. Then there are amplifiers that have a standby switch as well. 

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Welcome to the forum Henry.  It is nice to have another tube enthusiast participating.  
 

In regard to the Edcor OPTs, I believe they rate the frequency response at only 1 watt.  The response will decrease as power increases.  Other companies, like Hammond, specify bandwidth at full rated power.

 

 

Maynard

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On 8/12/2020 at 6:44 AM, henry4841 said:

I think when talking about warm up time is the rectifier tube being used.

 

My amps are monoblocks, and use Mullard GZ37 rectifiers. Although I get music within 30 seconds of powering on the amps, I haven't noticed much difference after 20 minutes on time.

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Yes, they are probably 98% after 20 minutes... depending on the music, I am too relaxed after that to really notice the difference. A couple hours in... sure, they are great.

 

Attached is the schematic for each

moondog_schematic.jpg

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Garyrc was talking PS transformer warm up time in post. The GZ34 is one rectifier tube that is slow about doing it's job and preventing a surge of voltage at turn on. It is not unusual to have close to 100V increase on the plates of tubes during turn on before the voltage goes down to the operating voltage. This increases the voltage rating needed for the filtering capacitors one must consider designing tube circuits. Tubes do need some warm up time before sounding their best and reach their operating temp though I have not noticed a dramatic difference in sound myself. Those with better hearing may.  

 

Marvel I like your 2A3 amp circuit. Nothing like true triode tubes when it comes to sound. 

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On 8/12/2020 at 6:09 AM, tube fanatic said:

In regard to the Edcor OPTs, I believe they rate the frequency response at only 1 watt.  The response will decrease as power increases.  Other companies, like Hammond, specify bandwidth at full rated power.

Maynard

I have never tried your favorite OPT, Hammond. Maybe the reason I like Edcor's is because I never use a steady 1 watt of power and of course the price difference. I have measured my power being used at my speakers when they were too loud for average conversation and have always found less than a watt of usage surging maybe just a little higher on peaks. Most of the time I use much less than a watt. One watt is a lot in my world. The beauty of Klipsch speakers. 

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5 hours ago, Jeffrey D. Medwin said:

  

 

It is not just the tubes warming up, the speaker voice coils need to come to operation temperature, the speaker suspensions limber up, as does all the magnetics, inside the amp. Warmup can take an hour, but if I " hammer " my system, usually the quickest is within 20 minutes, it gets 98% there, after a day or two on, 100%.   High end extension, freedom of playback, and ease of delivery into the room is what changes, and best of all,  it becomes mentally involving.  Altec 515B woofer and 802D drivers are used, very revealing drivers in a A7-8. 

 

 

 

FWIW Trivia:  When but a child, I attended many 70 mm roadshows, when they had tube amps (often Ampex made for Todd-AO).  We always arrived early (by unreliable bus) and I noticed that we could hear some very soft sounds from the speakers about 20 to 25 minutes before the overture started.  When we started visiting projectionists after the showing, the answer we got was that they were queuing up the soundtrack.We asked why they just didn't leave the amplifiers off until the sound was queued up?   They said the Todd-AO technical playbook advised warming up the amps for about 20 minutes.

 

* For the first two films, the sound was gorgeous, and, in some cities, was on a separate full coat 35 mm magnetic film, traveling at high speed, containing 6 soundtracks.  Later films had all 6 magnetic tracks on the main picture film.

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