[FullRangeMan]

I would stay away from Quicksilver amps, from my own experience,  he cannot maintain/repair his older units.  Once his amps get in need of repair, it's over.  Been down that road and not going back. FWIW.

In the late 1990s I remember Tamara Baker do a comment in TAS, there was a issue on a tested amp and some opinions about a model from this brand.

[sfox7076]

I just want the set of amps Freo-1 has (1625s that do 110 watts).  Where can you get those?

[2bigears]

 . Thanks for all the chimes guys. I do think its perfectly clear what I need to do.  Dam !
           

[Roger A. Modjeski]

I just want the set of amps Freo-1 has (1625s that do 110 watts).  Where can you get those?

I can make you a pair of monos or a stereo. I've been working with that tube since I was 16 year old. I made a AM radio transmitter with a 5 mile range with one.  Send me a message if you want one.

[Roger A. Modjeski]

Since the OP asked for amp suggestions, please elaborate on the 1 watt amp you'd prefer. 

I would recommend my RM-10 or my new 4 tube OTL. http://www.audiocircle.com/index.php?topic=121659.0

The power needed is more a matter of the listener. I rarely listen above 80 dB 90 dB peak so I would never even reach a watt with that speaker. However when I visited several listeners in the bay area I found they listened much louder than me, constantly hitting 99 dB peaks. Those levels hurt my ears!

There are excellent SPL meter applications for cell phones. I have one that shows peak and average. It's a lot better than guessing and fun to watch. There are also spectrum displays.

I really don't understand why the majority of these recommendations are for large amps when the post concerns a 91 dB speaker. And, why has no one asked how loud the listener likes his music and how far he sits from the speaker?  So I am asking.

[2bigears]

 .  Right on the money. I love it.  Like trying to go to a Doctor and the Doc asks no questions of how you eat or are you sleeping well. I do listen loudly on occasion and I sit about 8 feet from the speakers.  And like before , nothing but old time rock and roll with can be very dynamic.  Guitars of Pink Floyd to Ladies vocals.   It's our North American culture that we like headroom.  We think that more is better. I'm a prime example at 1.1KW's @ 4 ohms.  I think that's what my SS amp is. It's crazy anyway. Tube amps are a different animal to be sure. 

[Roger A. Modjeski]

.  Right on the money. I love it.  Like trying to go to a Doctor and the Doc asks no questions of how you eat or are you sleeping well. I do listen loudly on occasion and I sit about 8 feet from the speakers.  And like before , nothing but old time rock and roll with can be very dynamic.  Guitars of Pink Floyd to Ladies vocals.   It's our North American culture that we like headroom.  We think that more is better. I'm a prime example at 1.1KW's @ 4 ohms.  I think that's what my SS amp is. It's crazy anyway. Tube amps are a different animal to be sure. 

Thanks for your response. You really should try a lower power tube amp if you care about reproducing the excellent midrange (which no one has talked about) that you speaker is known to have.

Other than myself and Nelson Pass not many designers come out and tell you what has to be done in designing a high power amplifier. If one is designing for 10-20 watts it is easy to bias the amp in class A whether it be tube or SS. It is not easy or economical to make a 100 watt or larger class A amp. Excessive headroom is a misconception unless you are talking about single ended tube amps, and even then it's not the issue.

The common reply I get on the headroom question is that listeners think that 100x or 1000x headroom controls the speaker better. Well that's not what controls a speaker. Damping and the ability to deliver current controls a speaker. The Asmasphere was mentioned. It is a fine amplifier for what is can do but it cannot control a speaker no matter how big of one you get because it has very low damping and is current limited. No OTL I know of is suitable for a 4 ohm speaker unless it has a good autotransformer. BTW an autotransformer is quite different from a typical tube output transformer. It has much better bandwidth (mine is 200 KHz vs 60 KHz for a good Push pull transformer) lower losses and better bottom end.

If I may throw out a few numbers for consideration. If one makes a SS amp that produces 30 watts one can use high current transistors and bias them high without producing a lot of heat. Lower voltage transistors can handle much more current than high voltage transistors. A 30 watt amp needs only 25 volt rails for 8 ohms and less than 20 volts for 4 ohms. Transistors are very happy at those voltages. Your amp has about 100 volt rails. When you play music at 1 watt peak that's just 2 volts on the speaker and 98 volts on your transistors at half an amp which is 49 watts on the transistors. On a 20 volt rail amplifier its only 18 volts on the transistors at half an amp or 9 watts. I assure the transistors are much happier at 9 watts than 49 watts. Go up to a few watts and the numbers get rapidly worse for the big amp while getting better for the smaller one.  The numbers only get good for the big amp at full power which you will never reach.

With all respect to SS amp designers they have one other big problem which is current delivery and short circuit protection. Now that we know (and I hope you believe me) that current and damping are important, what has to be done to protect the more fragile high voltage transistors? It turns out that at voltages over 30 V all bipolar transistors have a second breakdown region that limits their current to very low levels. That is why high power amps have so many output transistors in parallel (which is not good for midrange detail). One has to protect these from shorted speaker leads so there is current limiting. Unfortunately this current limiting is also looking at the voltage it is putting on your speaker and puts out less current at low voltages which is precisely what we don't want. High power amplifiers like to be used at high power and have significant problems driving difficult loads at low power. Because of their current limiting few of them can drive electrostats or any speaker with a reactive load. Reactive loads look like shorts to load line current limiters.

The downside of power headroom is that most large amps don't sound so great at one watt because of what the designer had to do to make a high power amp. Thanks to Nelson for naming his work "First Watt". So much of the detail of music is in that first watt. When one gets a really clean system going I find that listeners actually turn the volume down because now they hear all the music without having to turn it up. There are speakers out there with very low sensitivity that need big amps, but your speaker is not one of them.

[JLM]

Just ordered PrimaLuna Dialogue Premium integrated from Upscale Audio.  Stereophile class A rated, lots of tube related safeguards, auto-bias extends tube life), rolls EL34, KT88, KT120, etc., 32 - 43 wpc at 8 ohms, MSRP $3400.  I have similarly rated speakers, so I'll let you know how it works out in a few weeks.  PrimaLuna also sells power amp version that can be used in stereo or monoblock mode and a HP version with double the number of output tubes (from 4 to .  Check out the reviews.

The old adage is that tube watts equal double the number of solid state watts.  I'm an old fart and listen like one (to mostly small ensemble classical/jazz) but like a occasional Led Zeppelin sort of fix.  Am a firm believer in amps maintaining a commanding grip on the speakers (lots of headroom) for improved resolution and driver safety.  Have used 7 wpc, 40 wpc, and now 100 wpc solid state on these speakers.  The 7 wpc did an amazingly respectable job but moving up to the 40 wpc turned the speakers from polite dinner guests into NFL linebackers in tuxedos.  The 100 wpc hasn't added much.

Keep in mind that watts versus dB's is a logrthymic relationship, so doubling the power only adds 3 dB and going up by a factor of 10 times the wattage only adds 10 dB (a doubling of apparent sound pressure levels).  So going from 7 wpc (8 dB of gain) to 40 wpc (16 dB of gain) should sound nearly twice as loud, but going from 40 wpc to 100 wpc (20 dB of gain) is roughly half again as loud).  But we don't listen to specifications and the real world is harder to define than by simple numbers, that's why I say "commanding grip" and "improved resolution" (imaging and detail).

Yes, as Roger mentions, damping factor is my concern with the PrimaLuna as I tried a tube amp with my speakers years ago and got alot of bass flab.

[Roger A. Modjeski]

Just ordered PrimaLuna Dialogue Premium integrated from Upscale Audio.  Stereophile class A rated, lots of tube related safeguards, auto-bias extends tube life), rolls EL34, KT88, KT120, etc., 32 - 43 wpc at 8 ohms, MSRP $3400.  I have similarly rated speakers, so I'll let you know how it works out in a few weeks.  PrimaLuna also sells power amp version that can be used in stereo or monoblock mode and a HP version with double the number of output tubes (from 4 to .  Check out the reviews.

The old adage is that tube watts equal double the number of solid state watts.  I'm an old fart and listen like one (to mostly small ensemble classical/jazz) but like a occasional Led Zeppelin sort of fix.  Am a firm believer in amps maintaining a commanding grip on the speakers (lots of headroom) for improved resolution and driver safety.  Have used 7 wpc, 40 wpc, and now 100 wpc solid state on these speakers.  The 7 wpc did an amazingly respectable job but moving up to the 40 wpc turned the speakers from polite dinner guests into NFL linebackers in tuxedos.  The 100 wpc hasn't added much.

Keep in mind that watts versus dB's is a logrthymic relationship, so doubling the power only adds 3 dB and going up by a factor of 10 times the wattage only adds 10 dB (a doubling of apparent sound pressure levels).  So going from 7 wpc (8 dB of gain) to 40 wpc (16 dB of gain) should sound nearly twice as loud, but going from 40 wpc to 100 wpc (20 dB of gain) is roughly half again as loud).  But we don't listen to specifications and the real world is harder to define than by simple numbers, that's why I say "commanding grip" and "improved resolution" (imaging and detail).

Yes, as Roger mentions, damping factor is my concern with the PrimaLuna as I tried a tube amp with my speakers years ago and got alot of bass flab.

Perhaps you should read the measurements section of the review given here. http://www.stereophile.com/content/primaluna-dialogue-premium-power-amplifier-measurements. From a very high (unusable) output impedance of 14 ohms the lowest that JA found was around 4 ohms which makes a miserable damping factor of 2 at best and 0.5 at worst (yes one can have damping less than 1). Looking at the graphs the amp has a lot of distortion and the transformers saturate at low frequencies. At one watt the bass distortion is 1% and although JA feels it is benign he doesn't mention the fact that there will also be large amounts of intermodulation distortion (IMD). Large IMD is no problem untill there is some bass. Its not that the bass gets a 2nd harmonic added, its that the nonlinearity produced by the bass causes all the rest of the music to be modulated by that bass wave. No bass, no problem, but then that's rather limiting isn't it. I think IMD needs much more attention and it is something I discuss in all my presentations.

Another way of looking at the damping problem is to view the response plots, figures 1 and 2. Given that most speakers are voiced with decent damping factors of 10 or more you will not be hearing your speaker as designed. Expect some pretty un-even response and no woofer control at all. The reviewer used 16 ohm Altec speakers. One should know that speakers of that vintage do not require high damping like modern speakers do. They were designed for low damping amplifiers of the 1950's and have fairly constant impedance curves and very good internal damping. Modern speakers rely much more on high damping amplifiers because that is what we have these days. The day that Edgar Villchur invented the closed box speaker changed the world of amplification and what amplifiers needed to do. Although I have great respect for Stereophile I find it odd that a component would get class A status from a listening test on a speaker that is no longer available, that is no longer typical of current speakers that most of us wouldn't even want.

Remember class A rating is based largely on the impressions of the reviewer in his particular system and hardly or not at all on measurements.

Here is a clever reader's reply at the end of the review online. Correct me if I am wrong; but shouldn't this be called PrimaChina?

[2bigears]

 .  Well, I see a few real important things here. Lets look at the speakers,and type of music played and
           how loud, preamp compatibility, ,,, can one hit on all aspects with a tube amp ? 

[sfox7076]

I can make you a pair of monos or a stereo. I've been working with that tube since I was 16 year old. I made a AM radio transmitter with a 5 mile range with one.  Send me a message if you want one.

PMs sent (one with an appology for not realizing your history). 

[2bigears]

 .  Rodger,, if we can have a friendly audio-nut talk on the ph ,, I would very much enjoy..
             Pat Paradis. 

[poseidonsvoice]

Perhaps you should read the measurements section of the review given here. http://www.stereophile.com/content/primaluna-dialogue-premium-power-amplifier-measurements. From a very high (unusable) output impedance of 14 ohms the lowest that JA found was around 4 ohms which makes a miserable damping factor of 2 at best and 0.5 at worst (yes one can have damping less than 1). Looking at the graphs the amp has a lot of distortion and the transformers saturate at low frequencies. At one watt the bass distortion is 1% and although JA feels it is benign he doesn't mention the fact that there will also be large amounts of intermodulation distortion (IMD). Large IMD is no problem untill there is some bass. Its not that the bass gets a 2nd harmonic added, its that the nonlinearity produced by the bass causes all the rest of the music to be modulated by that bass wave. No bass, no problem, but then that's rather limiting isn't it. I think IMD needs much more attention and it is something I discuss in all my presentations.

Another way of looking at the damping problem is to view the response plots, figures 1 and 2. Given that most speakers are voiced with decent damping factors of 10 or more you will not be hearing your speaker as designed. Expect some pretty un-even response and no woofer control at all. The reviewer used 16 ohm Altec speakers. One should know that speakers of that vintage do not require high damping like modern speakers do. They were designed for low damping amplifiers of the 1950's and have fairly constant impedance curves and very good internal damping. Modern speakers rely much more on high damping amplifiers because that is what we have these days. The day that Edgar Villchur invented the closed box speaker changed the world of amplification and what amplifiers needed to do. Although I have great respect for Stereophile I find it odd that a component would get class A status from a listening test on a speaker that is no longer available, that is no longer typical of current speakers that most of us wouldn't even want.

Remember class A rating is based largely on the impressions of the reviewer in his particular system and hardly or not at all on measurements.

Here is a clever reader's reply at the end of the review online. Correct me if I am wrong; but shouldn't this be called PrimaChina?

Excellent points Roger. I have seen few, very few tube designers taking a stab at lowering IMD. It's a very real problem.  The few that I know of working on the problem include yourself and Jack Elliano.

Best,
Anand.

[Freo-1]

Excellent points Roger. I have seen few, very few tube designers taking a stab at lowering IMD. It's a very real problem.  The few that I know of working on the problem include yourself and Jack Elliano.

Best,
Anand.

Terms such as Transient Intermodulation Distortion (TID) and Intermodulation Distortion (IMD) get referenced a lot.  Here are definitions of the two items.  TID is a major reason many solid state amps often don't sound so hot compared to a well designed tube unit. 



TID Definition:
Transient intermodulation distortion, or TID/TIM, occurs in amplifiers that employ negative feedback when signal delays make the amplifier incapable of correcting distortion when exposed to fast, transient signals.

IMD Definition:
Intermodulation Distortion, or IMD is an amplifier or pre-amplifier specification that measures non-harmonic frequencies added to the signal. IM distortion is the result of two or more signals mixing together that are not harmonic frequencies. These signals mix to create additional non-harmonic frequencies that are undesirable. Using the same middle C note example from above, if an amplifier creates a non-harmonic frequency of 300Hz along with the fundamental frequency of 440Hz, a third frequency of 740Hz will be reproduced (440 + 300), and 740Hz is not a harmonic of 440Hz. Thus, it is termed intermodulation distortion because it is between harmonic frequencies.
 

[2bigears]

 .  Amp builders terminology .. I gotta admit I would like to try a 200.. 
            But,,,, always a dam butt ! Ha. Will it mate with the pre ? How do you
               even begin to know ? 

[Freo-1]

.  Amp builders terminology .. I gotta admit I would like to try a 200.. 
            But,,,, always a dam butt ! Ha. Will it mate with the pre ? How do you
               even begin to know ? 

Not that difficult.  The preamp out to power amp input impedance needs to be at least 10 to 1 ratio.  In other words, the input impedance for the power amp needs to be at least ten times higher than the output impedance of the preamp.  Some audiophiles like it closer to 20 to 1 to get a flat frequency response.  The other item to look at is power amp gain vs. preamp gain.  Most systems actually have too much gain between the preamp and power amp.

[2bigears]

 .  Well thanks .. I guess I'm on a #'s search about now. Sounds easy ..   Ha
            So pre-amp-speaker must all be within borders of each other to transmit properly ..
                     

[Roger A. Modjeski]

.  Amp builders terminology .. I gotta admit I would like to try a 200.. 
            But,,,, always a dam butt ! Ha. Will it mate with the pre ? How do you
               even begin to know ? 

Will it mate? Yes, in most cases all preamps and poweramps are compatible much more so than poweramps and speakers.  What is your specific concern?

As to the 10 to 1 ratio of impedance, I disagree that it is necessary or even helpful. Most systems will work fine with 2 or 3 to 1 as long as sufficient current and voltage are available.  I think 20 to 1 is hard to obtain and pointless. But once audiophiles hear there is a ratio there is not stopping till one gets to infinity. BTW if anyone wants to try infinity here's how. In most tube amplifiers the grid return resistor to ground is the only load. It is typically 100K ohms but in many cases it could be 1 Meg ohm. If your preamps has some resistor on the output and they all do, you can take out the grid return resistor in the power amp and have infinite input impedance. However you can't do that with a transistor amp.

I do agree that most systems have too much gain and we make an attenuator that goes between the pre and power amp on the power amp end of the interconnect to reduce excessive gain and the noise that is usually present.  The attenuator can also help unload the preamp if that is a concern. Most preamps can drive a 10K load and most poweramps are above that.

[nnck]

Thanks for your response. You really should try a lower power tube amp if you care about reproducing the excellent midrange (which no one has talked about) that you speaker is known to have.

Other than myself and Nelson Pass not many designers come out and tell you what has to be done in designing a high power amplifier. If one is designing for 10-20 watts it is easy to bias the amp in class A whether it be tube or SS. It is not easy or economical to make a 100 watt or larger class A amp. Excessive headroom is a misconception unless you are talking about single ended tube amps, and even then it's not the issue....

The downside of power headroom is that most large amps don't sound so great at one watt because of what the designer had to do to make a high power amp. Thanks to Nelson for naming his work "First Watt". So much of the detail of music is in that first watt. When one gets a really clean system going I find that listeners actually turn the volume down because now they hear all the music without having to turn it up. There are speakers out there with very low sensitivity that need big amps, but your speaker is not one of them.

Roger- Very interesting discussion going on here in regards to high-powered vs low-powered amps and damping factor/current limitations. Makes me wonder what sort of implementations you used on your higher-powered amps (such as the RM-200II) to give it proper damping and to keep it from being current-limited as you say many other higher-powered amps are.

Is there a way for you to give some figures on the amount of damping and available current in your low-power vs high-power designs (RM10 vs RM200)?

[Roger A. Modjeski]

The RM-200 is unique in that it automatically and effortlessly goes from class A to AB1 to AB2. That means the driver is able to take the grids into the positive region for extra current by being direct coupled to the output tubes.  Most tube amps have just the current and voltage available for the stated load and do  not drive the grids positive. For 100 watts that means 40 volts peak and 5 amps. The RM-200 delivers a few extra amps as needed when the speaker impedance drops below the rated load of the tap. Most amps deliver less power as the load drops and that overheats the tubes. The worst thing you can do to most tube amps is load them below the tap impedance. The best thing you can do I call "light loading" which is to go in the other direction using a tap of lower impedance than the speaker. That is why the RM-200 has 4 impedance taps at 8.4,2,1 ohm. It also was one of the first amps to achieve 100 watts with one pair of output tubes without stressing the tubes.

The RM-10 on the other hand does not have an AB2 region as the output tubes are capacitor coupled as most amps are. However it does produce twice the power of typical EL-84 amps by virtue of a very high plate voltage and low screen. It is the only EL-84 amp that does that. 

All my amps have a damping factor around 10 as less would cause a lot of speaker interaction, more wouldn't help much and would make the amp unstable. Most amplifiers I have measured with higher damping can be made to mis-behave on difficult loads.

I am only interested in designing new circuits and applications that have not been done before. There are plenty of companies who are building the same old stuff as everyone else.