[tanchiro58]

Tan

Just curious - how does your BYOB sound compared to your modified Sun 2A3? Which do you prefer?

Best Regards
Dennis

Dennis,

Now I prefer the BYOB amp over my Sun Audio 2A3 SET amp after modifying it . It has now the sweetness and blooming of the tube but it has also the fast deeper bass. 

Tan

I do think you can get very good bass from tubes, but it needs more careful matching with the speaker.

Zybar is absolutely correct. My push-pull 300B monoblock amps were built with R-cores output transformers and they drive my custombuilt speakers with JBL D131 woofers easily with plenty of bass. I got the push-pull 211 monoblock amps which drive easily this pair of Infinity in this picture.

[zacster]

I'll give my contrary opinion on one facet of this debate.  Solid State amps are NOT more reliable than tube amps.  Quite the opposite. 

When I have a problem with my tube amps, I can open it up, trace it, swap tubes around, do a lot of troubleshooting.  If it is a bad tube, you replace the tube.

When I have a problem with my SS amps, I replace the fuse and hope for the best.  I may try to replace a cap as a guess.  But if a transistor burns out, fuggedaboudit.  And in the last 3 months, 2 of my SS amps have died.  In fact, every SS amp I've ever owned has died.

My 40 year old ST-70 is still kicking, albeit with a completely modded circuit.  My 6 month old T-amp is still alive, and a cheapo Sony HT amp from about 6-7 years ago still works but sounds horrible.  I've lost an AR (Acoustic Research, not Audio Research), a NAD, A Creek, a Pioneer, and I don't know how many SS devices of other uses.  They are NOT reliable. 

I was at the HE Expo in NYC last spring and went from room to room.  I could immediately tell whether they had SS, PP pentode tubes, or single ended DHT.  SS sounded clinical, PP sounded bloomy, and SE sounded sweet but lacked oomph.

My ST-70 has been modded to use DHT 6B4G class A in PP operation.  I guess this is like Tan's amp, or are those parallel PP monoblocks?  That would be yet another topology.  But 8 300Bs?  That's a lot of money for the tubes even for JJ, never mind WE!

[tanchiro58]

But 8 300Bs?  That's a lot of money for the tubes even for JJ, never mind WE!

Zacster,

The push-pull 300B monoblock amps (20W output) had kick-assed the AN Ongaku once when we compared them before side by side. Do you see the picture above the owner of the Infinity speakers had sold his Mark Levinson 30H after listening to the push-pull 211 monoblock amps  which were also in the picture.

[lazydays]

I was much like Wayner - preferring tube preamp driving SS amps - the 3 dimensional nature was good.  But 10 seconds in to hearing a SS pre-amp driving mono tube amps and I was sold on that combo instantly.

In my case I went from a Dynaco PAS-4 (tube preamp) happily passing it to Odyssey Khartago Extreme amps to something I've even happier about now.  It has nothing to do with Odyssey offerings - which are superb SS amps (the best SS amps that I ever owned)

The lowest level signals, especially if you enjoy vinyl (typically, 1/20th to 1/400th or less voltage than CD outputs) beg for as clean a step-up as possible.  If you pass that to a capable tube amp(s) (that is, one that is capable of driving your speakers with adequate headroom for peak passages) you have ultra-quiet step-up that can only be achieved with solid state with the purity and  3 dimensionality that tubes bring to your music.

SS preamps seem to provide a 'backbone' of sorts to the music that I haven't been able to approximate with tube preamps.....even those that have been solid state regulated.

If you have tube amps that are either tube or solid state regulated (not rectified), you achieve considerably more chest-thumping bass 'tightness' that is usually the domain of solid state amps.

If you add a powered subwoofer(s) to the mix - you're further relieving your tube amp of the heaviest bass duties and you can achieve some smile-inducing bass heft and 'tightness' back into the sonic realm 

So, SS preamp and tube amps for me - an unlikely electrical match as tubes typically step-up voltages better and solid state better develops current (all the better to drive most complex speaker loads).  The more you simplify your speaker loads, the more tolerant of tube amps your system will be - and you can enjoy the excellent pairing of a SS pre-amp and tube amp(s) more completely

If you're into vinyl especially, you might want to turn your Odyssey / Candela up on it's conventional head and try it...I've never been happier 

My current system:

Bell Dual Mono Integrateds (10 watt tube units powering 6.5" mid-woofers and tweeter)
Mitubishi DA-C20 working as SS phono preamp and providing AM/FM
Gallo TR-1 (100 watt) subwoofer (dedicated below 80hz)
Linaeum Tower speakers (80hz and up)

CD is run straight into the Bell's....the added liquidity of all tube seems to benefit CD playback.

 

as long as I've been fooling around with audio equipment it has always been a known thing to never ever drive a tube amp with a solid state preamp. I've tried it three times and it was less than bad. But on the opposite side it's a nice combo to drive a solid state amp with tubes. Why I don't know for sure, but I've always been able to tell the difference easilly.
gary

[zacster]

No doubt they sound nice, I just choke at the cost of all the tubes.  4 6B4G tubes cost all of $130, whereas even cheap 300Bs go for over $200/pair, and WE are 850/pair. 

Maybe this isn't quite in the same league but I did a similar thing with my modded Dynaco.  I brought it to a Bottlehead group meeting, which is almost all SE amps but not all Bottlehead, and the Dynaco was played more than any other amp.  Nothing else sounded as good.  I'm basically an amateur at DIY but I was able to put this together with a little forum help.  Push-pull gets a bad rap from all of the UL pentode implementations done from the 1950s, like the ST-70, but can sound really nice when done right, no NFB, class A, DHT, tube rectified, good coupling caps (or IT). 

[TheChairGuy]

Gary / lazydays,

It's all about the speaker your driving.  The Linaums have but an inductor on the woofer and the simplest of simple crossover on the tweeter.  Not much current, a significant betterment that a solid state amp brings to the audio 'party', necessary to drive them. 

Simpler really is an understatement when using tube amps driving speakers successfully.

No crossover whatsoever are an even more tempting option in the future 

John

[lazydays]

Gary / lazydays,

It's all about the speaker your driving.  The Linaums have but an inductor on the woofer and the simplest of simple crossover on the tweeter.  Not much current, a significant betterment that a solid state amp brings to the audio 'party', necessary to drive them. 

Simpler really is an understatement when using tube amps driving speakers successfully.

No crossover whatsoever are an even more tempting option in the future 

John

John,
The post I made was from what I've been told by various amp manufacturers in the past.
This went all the way from the Accuphase folks to Conrad Johnson. The other post I made about impedence curves is just something I happened upon, and may not be all perfect, but my ears say it's so.
    About a year or so ago I was in the hunt for a nice lightly used pair of Meadowlark Herons (I'd just missed the last pair the factory had for half price!!). The reason why? I wanted that tube friendly impedence curve to use with my Odyssey Mono SE's. And who knows down the road I may happen upon a deal on a pair. I did order a pair of the new Lorelei II's from Odyssey, and as soon as I get my living room finished we'll be listening to them. The cross overs will be slightly tweeked on these speakers, and as usual I speced WBT connectors all the way around. Will they sound as good as a pair of Herons? I have no idea. Would either of these two speakers sound as good as the Maggie 3.6's I originally wanted? Doubt it. Still what I'm really implying is that some amps can be voiced to have a "tube like sound", but most will not. If I ever sell my monos, I'll be back with tubes again. But I really doubt I'll be in the hunt for a new amp in the near future. I pretty close to what I desire in my down stairs system (two more pieces in the source, and I'll leave it alone). After that it's a complete rebuild of the upstairs system (it's all tubed) as everything is getting tobe very dated.
gary

[TheChairGuy]

Gary - yup, my hunt for the perfect solid state amps ended with Odyssey, too.  I was rediculously happy with the Khartago (stereo) unit I first bought...the Khartago Mono Extreme's Klaus made up for me were overkill, however.

My speakers are sooooo easy to drive and I listen at fairly moderate levels most of the time...that moving to the Extreme's was overkill for me. For others, it may have been and probably are, necessary to drive their speakers more authoritatively.  For me, a Khartago (stereo) was good enough....and it was indeed good.

But, 10 seconds in to hearing my first mono tube amps I knew it was game over for SS amps for me. Benign impedance curves surely help...but I think quite minimal or NO crossovers whatsoever seem to be the way to go for tube amps   

At least, that's been my experience thus far. Still experimenting, of course.... 

John

[Bob Reynolds]

This is a generalization, but the biggest difference to me between SS and tube amps is the output impedance. Tube amps typically have a much higher output impedance which will have a much larger interaction with the speaker. Thus, finding an amp/speaker pair is much more difficult.

For high output impedance amps, we have a case of the tail wagging the dog -- the impedance curve of the speaker determines the frequency response of the amp.

[george_k]

Solid state amps very little warm-up time/effect compared to tubes.

Actually solid state amps take a long time as well, I was told by a Naim dealer that their amps take about 2 days to reach optimal operating temperature from a sonics perspective. He said that they should never be turned off. I also read this online somewhere (can't remember where) when I was considering the acquisition of a Nait 5i.

I've also read that Class D amps take a while to reach their optimal operating temperating when starting from a cold startup. I guess this explains why the Jeff Rowland ice power amp I had for a short while didn't sport an on/off switch...all it had was a power connector and 2 cardas binding posts (I really don't think the cost of adding a switch was an issue for the company).

[underdog64]

Tube advantages:

1.Easier on highs and mid (less fatigue-especially important if ordinary cd is format of choice since cd is almost always lacking in depth and highs are often bright,edgy)

2.Can customize use of tubes (tube roll to get better mids,highs or bass etc)on most models

3.Imaging is most life like.Many digital amps  and expensive solid state can sound smooth or liquid but can't match the "in the room" presence tubes provide

4.Coolness factor-always wanted a fireplace in my living room but didn't have the money to add it 

5.Could be wrong on this but well known tube amp brands seem to hold their value better than many solid state and definately more than digital (which technology is evolving rapidly)

Solid State advantages over tubes:

1.Can integrate bass with mids better or have tighter bass.This can be fixed somewhat with purchase of autofomers (which change speakers impedance -up) or matching with a speaker that has a flat impedance curve

3.Tubes can (but not all time) cost more than SS and tubes are more expensive to maintain (due to cost of tubes)

4.Tube amps most often need to be placed on floor or require seperate stands from audio rack.

5.Tube amps must be biased every so many hours of use-although many now are self biasing

5.Some tube amps (single ended class a and otl) can warm room as much as 15 degrees -not good in Phoenix where I live

[bhobba]

1.Easier on highs and mid (less fatigue-especially important if ordinary cd is format of choice since cd is almost always lacking in depth and highs are often bright,edgy)

Not always. 
http://www.audiocircle.com/index.php?topic=46870.msg420534
'The LifeForce was the first solid state amp to totally kill off my long held, subconscious feeling that I would ultimately end up with a tube amp'

Admittedly it took the designer, Hugh Dean, years to perfect it.

Thanks
Bill

[Duke]

Bob Reynolds wrote:

"This is a generalization, but the biggest difference to me between SS and tube amps is the output impedance. Tube amps typically have a much higher output impedance which will have a much larger interaction with the speaker. Thus, finding an amp/speaker pair is much more difficult.

"For high output impedance amps, we have a case of the tail wagging the dog -- the impedance curve of the speaker determines the frequency response of the amp."

This is partially correct, and I can certainly understand how the situation looks this way.   It did to me too until I started designing loudspeakers intended to work well with a wide range of amplifiers, and found out things aren't as simple as they seemed.  I had assumed that a solid state amp outputs the same power regardless of the impedance curve, overlooking the commonly-known characteristic of solid state amps doubling their rated power out into a 4 ohm load and halving it into a 16 ohm load.  You see, most solid state amps approximate a constant voltage source - in other words, the wattage they put out goes up as the impedance of the load goes down.  The output power varies inversely with a speaker's impedance swings.  Let's look at an example:

Suppose we have a speaker with a 32 ohm peak in the bass region, then the impedance falls to 4 ohms at 200 Hz, then rises to 16 ohms in the 3 kHz crossover region, then remains at about 8 ohms above that.  I'd probably call this a "6 ohm" speaker.  Let's look at what happens when this speaker is driven by a solid state amp, putting out 2.83 volts (equal to 1 watt into an 8-ohm load):

Into that 32-ohm peak in the bass region, the amp is putting out 1/4 watt.  Then it's putting out 2 watts at 200 Hz, 1/2 watt at 3 kHz, and 1 watt above that.  Assuming the speaker is aimed at solid state amp owners, it's up to the designer to take all of this into account - and this is routinely done, no problem.  But, my point is this:  Typical solid state amps DO NOT put out the same power regardless of the speaker's impedance!  It only seems that way because most speakers are designed to be used with solid state amps.

Tube amps (and transformer-coupled solid state amps) usually approximate a power source - that is, they deliver nearly constant wattage regardless of the speaker's impedance curve (as long as the speaker's impedance stays within the proper range for that amplifier).   Such an amplifier would deliver approximately the same power across the roller-coaster impedance curve described above, and probably would not be a good choice with that speaker assuming it was "voiced" for a voltage-source amplifier.  However, some speakers are at their best with an amplifier that acts as a power source - including electrostats and many high-efficiency speakers.

A few tube amps (and recent Nelson Pass designs) have very low damping factors (high output impedances) and approximate a current source - that is, their power output increases into a high impedance load and decreases into a low impedance load, but in practice they're usually about halfway between being a power source and a current source.  In the real world, we might expect a high output impedance tube amp to deliver 2 watts into that bass impedance peak, 1/2 watt into the lower midrange dip, 1.5 watts into the midrange peak and 1 watt at high frequencies.   Note that this is a 4-to-1 difference into the bass impedance peak compared with the solid state amp's output.  I have measured this much difference (6 dB) on bass impedance peaks when going from a high damping factor solid state amp to a low damping factor OTL tube amp.  This can be either a blessing or a curse, depending on the speaker's design.

You may have realized that the foregoing implies the smoother a speaker's impedance curve, the wider variety of amplifiers it will work well with.  Such has been my experience.

So to recap, the power output of a typical constant-voltage-approximating solid state amp actually changes significantly depending on the speaker's impedance, but most modern speakers are designed with this in mind.  Still, some of the most interesting loudspeakers work better with amplifiers that more closely approximate a constant-power source.

Duke

[Bob Reynolds]

Bob Reynolds wrote:

"This is a generalization, but the biggest difference to me between SS and tube amps is the output impedance. Tube amps typically have a much higher output impedance which will have a much larger interaction with the speaker. Thus, finding an amp/speaker pair is much more difficult.

"For high output impedance amps, we have a case of the tail wagging the dog -- the impedance curve of the speaker determines the frequency response of the amp."

This is partially correct, and I can certainly understand how the situation looks this way.   It did to me too until I started designing loudspeakers intended to work well with a wide range of amplifiers, and found out things aren't as simple as they seemed.  I had assumed that a solid state amp outputs the same power regardless of the impedance curve, overlooking the commonly-known characteristic of solid state amps doubling their rated power out into a 4 ohm load and halving it into a 16 ohm load.  You see, most solid state amps approximate a constant voltage source - in other words, the wattage they put out goes up as the impedance of the load goes down.  The output power varies inversely with a speaker's impedance swings.  Let's look at an example:

Yes, that's correct -- low output impedance amps are constant voltage sources. All that means is that the output impedance is so low there is no significant voltage drop across it relative to the drop across the load.

Suppose we have a speaker with a 32 ohm peak in the bass region, then the impedance falls to 4 ohms at 200 Hz, then rises to 16 ohms in the 3 kHz crossover region, then remains at about 8 ohms above that.  I'd probably call this a "6 ohm" speaker.  Let's look at what happens when this speaker is driven by a solid state amp, putting out 2.83 volts (equal to 1 watt into an 8-ohm load):

Into that 32-ohm peak in the bass region, the amp is putting out 1/4 watt.  Then it's putting out 2 watts at 200 Hz, 1/2 watt at 3 kHz, and 1 watt above that.  Assuming the speaker is aimed at solid state amp owners, it's up to the designer to take all of this into account - and this is routinely done, no problem.  But, my point is this:  Typical solid state amps DO NOT put out the same power regardless of the speaker's impedance!  It only seems that way because most speakers are designed to be used with solid state amps.

Yes, for a constant voltage source the current supplied will be determined by the impedance of the load and the power dissipated will vary as described by Ohm's Law.

Tube amps (and transformer-coupled solid state amps) usually approximate a power source - that is, they deliver nearly constant wattage regardless of the speaker's impedance curve (as long as the speaker's impedance stays within the proper range for that amplifier).   Such an amplifier would deliver approximately the same power across the roller-coaster impedance curve described above, and probably would not be a good choice with that speaker assuming it was "voiced" for a voltage-source amplifier.  However, some speakers are at their best with an amplifier that acts as a power source - including electrostats and many high-efficiency speakers.

How does that work? Can you provide more details?

A few tube amps (and recent Nelson Pass designs) have very low damping factors (high output impedances) and approximate a current source - that is, their power output increases into a high impedance load and decreases into a low impedance load, but in practice they're usually about halfway between being a power source and a current source.  In the real world, we might expect a high output impedance tube amp to deliver 2 watts into that bass impedance peak, 1/2 watt into the lower midrange dip, 1.5 watts into the midrange peak and 1 watt at high frequencies.   Note that this is a 4-to-1 difference into the bass impedance peak compared with the solid state amp's output.  I have measured this much difference (6 dB) on bass impedance peaks when going from a high damping factor solid state amp to a low damping factor OTL tube amp.  This can be either a blessing or a curse, depending on the speaker's design.

You may have realized that the foregoing implies the smoother a speaker's impedance curve, the wider variety of amplifiers it will work well with.  Such has been my experience.

So to recap, the power output of a typical constant-voltage-approximating solid state amp actually changes significantly depending on the speaker's impedance, but most modern speakers are designed with this in mind.  Still, some of the most interesting loudspeakers work better with amplifiers that more closely approximate a constant-power source.

Duke

Unfortunately or not, the amplitude vs frequency response is measuring voltage. So for a low output impedance amp, its frequency response will not be influenced by the impedance curve of the speaker and thus, will be more widely applicable than a high output impedance amp.

The "power paradigm" promoted by Ralph Karsten (Atma-Sphere) is interesting and I agree that if we plotted power vs frequency, we'd get a different picture. I have a hard time understanding the notion of a constant-power source. Since the impedance of the load varies, does that imply that both the voltage and current vary so that the power dissipated remains constant? How does that work?

[Wind Chaser]

This thread is starting to get very interesting...

[Duke]

Thanks for replying, Bob.

It is my understanding that amps made by Atma-Sphere, Wolcott, deHavilland, and McIntosh approximate a power source - that is, they deliver fairly close to constant power over a limited impedance range.  There are probably other examples as well that I am not familiar with.   One of these is an output transformerless tube amp, one is a push-pull transformer coupled tube amp, one is a single-ended triode transformer-coupled tube amp, and one is a transformer-coupled (or more precisely autoformer-coupled) solid state amp.  I'm not electrical engineer enough to know why these amps have this characteristic. 

Based on my own measurements, in practice the little Atma-Sphere S-30 sort of approximates a current source amp with some speakers.

Note that last time I checked I still hadn't attained "infallibility", so I may well be mistaken in some of this.  Having thus made my disclaimer, next I'll concede that insofar as the voltage amplitude vs frequency output of a solid state amp is independent of the load, it's fair to say that the amp's frequency response - referenced to voltage! - is also independent of the load.  However, its power vs frequency response is definitely load-dependent! 

And if it is power (wattage) that drives a loudspeaker, then the frequency response of the voltage-source amplifier + loudspeaker combination is indeed sensitive to the loudspeaker's impedance curve, because that impedance curve is modulating the amplifier's wattage output, and it is wattage into the speaker at a given frequency which determines how loud the speaker plays at that frequency.

I think it's justifiable to focus on wattage (not voltage) into the loudspeaker because wattage is the most precise and direct description of the electrical energy going into the speaker that is then converted (or transduced) into acoustic energy - and that acoustic energy can also be expressed in watts. 

I think I could back up my position by making frequency response measurements of a speaker driven by a voltage-source-approximating amplifier and a power-source-approximating amplifier, assuming the latter maintains that characteristic over the impedance fluctuation range of the loudspeaker.

Let me know if you see any obvious (or subtle) mistakes that I'm making. 

Thanks,

Duke

[Steve Eddy]

Tube amps (and transformer-coupled solid state amps) usually approximate a power source - that is, they deliver nearly constant wattage regardless of the speaker's impedance curve (as long as the speaker's impedance stays within the proper range for that amplifier).   Such an amplifier would deliver approximately the same power across the roller-coaster impedance curve described above...

Except that's not what tube amps do.

Yes, a typical tube amp is rated at approximately the same power on the 2 ohm tap as on the 4 ohm tap as on the 8 ohm tap, etc. But that's not the same as delivering constant power regardless of the speaker's impedance curve.

For any given tap, the amp will deliver a varying amount of power to the loudspeaker depending on the speaker's impedance curve, no differently than a typical solid state amp.

se

[bhobba]

Hmmmmm.  Technical differences.  It has been years since I was into circuit design, but off the top of my head, I would say one difference is valves have an inherently much higher input impedance than tubes, and if I remember correctly, transistors are basically current amplifiers - valves voltage amplifiers.  But if I also remember correctly, FET's have many of the characteristics of valves.  I suspect that each can be made to sound a lot like the other with appropriate circuit topologies. 

Frank Alstine's take seems to be tubes have greater overload capacity - which considering their voltages makes sense:
http://www.audiocircle.com/index.php?topic=38021.msg%25msg_id%25
'The "Fet Valve" name is just our verbage in describing our patented circuit topography of a valve (Brit name for a vacuum tube) and a power mos-fet in a clever loop that provides the high input voltage overload capability of the tube, and the low output impedance and high drive current of the mos-fet, and blazingly fast bandwidth and absolute stability to boot. No it is not a "poor mans Moscode" inasmuch as we are not attempting to drive the high gate input capacitance of a power mos-fet output circuit with the poor current drive and high output impedance of a tube.  In the Fet Valve designs, the tube looks only at "air" and the linearity is at least 10 dB better than when driving a load.  It works pretty darn well.'

But I have also heard him say the audible difference is rather subtle.

Thanks
Bill

[bhobba]

Hmmmmm.  Technical differences.  It has been years since I was into circuit design, but off the top of my head, I would say one difference is valves have an inherently much higher input impedance than tubes, and if I remember correctly, transistors are basically current amplifiers - valves voltage amplifiers.

Of course that should be 'valves have an inherently much higher input impedance than transistors'.

Sorry
Bill

[Duke]

Hi Steve,

Boy am I outta my league now.   

You said, "For any given tap, the amp will deliver a varying amount of power to the loudspeaker depending on the speaker's impedance curve, no differently than a typical solid state amp."

Okay, looks like was I right about the solid state amp's power output being modulated by the speaker's impedance curve.

But.... what you're saying here implies that a loudspeaker driven by a tube amp, and that same loudspeaker driven by a solid state amp, will have the same frequency response - right? 

Because, I have seen frequency response curves that say otherwise.  They were generated by Earl Geddes.  They are on his computer (if he saved them) not mine, but I think I can show the same thing.

Did I misunderstand something?

Duke