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1.5 ohm resistor in series with speaker

Tripqzon

Tripqzon

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Saw this thread Q & A with Bob Carver posted by TNRabbit yesterday and am wondering if anyone has tried this trick in their system(s)?

Bob Carver states in Part 1 and discusses it more in the beginning of Part 2 that you can make any good quality amp sound like a tube amp by inserting a 1.5 ohm resistor in series between the positive terminal of the amp and the speaker. Also, turn up the bass control from 12 o'clock to about 12:30 or 1 o'clock. That will get you to about 80% of what a tube amp sounds like. He also states you can get even closer if your speakers are bi-amp capable by leaving the shorting bar between the negative terminals of the speaker and replacing the shorting bar between the positive terminals of the speaker with the resistor. That way the resistor will only affect the high frequency driver(s). Of course there is more to it than that so you can watch the video for more detail.

I'm sure Bob knows what he's talking about but I would like to hear some thoughts from others who have tried this.

Paul
 
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Not being familiar with the "sound" of tube amplifiers, but having read enough to have an idea of how it should differ from solid state "sound", I would not think this that this would do it.

As already stated, series resistance will bump up the sharpness of the driver's resonance peaks and lower their apparent efficiency. This will most likely throw-off the enclosure alignement and result in boomier bass.

So "tube sound" is about boomy bass? I would not think so. I think it is a result of the harmonics added to the original signal, giving it a distinctive sound.

az
 
After watching the video, I think that Bob Carver was suggesting something neat to try, to see if you liked it. His tone was more along the lines of one who likes to experiment and tinker and share with others, rather than suggesting that this outmoded tube amplification.
 
He's very optimistic if he really quotes 85%. Altering the DF with a series resistor might get you half-way there, with stereotypically "over-rich bass" and "rolled off highs" which, I think, are present only in some designs. Although the above applies to most tube amps I've heard (usually negated with very sensitive speakers that tend to be somewhat over-damped), many I've heard have very tight and satisfying bass, with clear and extended high-end. Regardless, that's only 50%. The other half is a certain illusion of depth in the midrange that is much more difficult to emulate. A solid-state amp must be very well designed, indeed, (and usually very expensive) to duplicate that.

I've heard solid-state amps that do a fair good job of recreating the positive attributes of a tube amp (usually reinforced with the positive attributes of a sand amp) that have reasonably high DF (>100). Although not to be taken as gospel, the common theme among these solid-state units is that they generally have high slew rates, wide bandwidth, and have a purely DC signal path.

Other amps that come close to stereotypical "tube sound" are output-capacitor coupled receivers from the late 1960's and early 1970's. It would appear that they accomplish this in a manner closer to Mr. Carver's method.

Still, the best way to get tube sound, unsurprisingly, is to use tube amps.

It does make me chuckle inside when even ardent supporters of solid-state design seem to still hold the tube as some sort of gold-standard. A well designed and good sounding amp is just that, regardless of how it gets there. Personally, I don't care if it's a single-ended triode or a class D with 20 output devices per channel- how it sounds in my room, with my speakers, to my ears is what is important. If you're trying to duplicate the sound of one with the other, you're better served just going with what sounds better to you.
 
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M Jarve said:
Still, the best way to get tube sound, unsurprisingly, is to use tube amps.

It does make me chuckle inside when even ardent supporters of solid-state design seem to still hold the tube as some sort of gold-standard. A well designed and good sounding amp is just that, regardless of how it gets there. Personally, I don't care if it's a single-ended triode or a class D with 20 output devices per channel- how it sounds in my room, with my speakers, to my ears is what is important. If you're trying to duplicate the sound of one with the other, you're better served just going with what sounds better to you.
Click to expand...

AMEN!:yes:
 
So the general consensus is that this would be a waste of time and effort.

When one of the participants asked Bob if he was talking them out of buying his amps he says that part of the enjoyment of listening is the emotional part of it and there was nothing like seeing the tubes glowing to stir your emotions. He also states that this mod will get you close to the sound of tubes. So it sounds like just the glow of the tubes will convince some people that tubes sound sweeter than solid state. I'm not stating that this applies to all music fans but he didn't do a good job of convincing me to go out and buy his tube amps when a simple mod could get it close.
 
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I don't think it would be a waste of time or effort. The hobby is all about trying new things and experimenting. You're only out about $5 worth of resistors if you don't like it.
 
Years ago, I did this on a pair of Avid 110 speakers with 1 Ohm, 10 Watt wirewound sandbar resistors. If rolling off highs very slightly is all it takes to make a good SS amp sound like a tube amp, then I have to say it was a smashing success.

I presently have those same 1 Ohm 10 Watt sandbar resistors in place in my speaker lines, but it's to raise the total system impedance from 3 Ohms to 4 for my stacked KEFs. This time, however, I noticed no difference in treble response... this could be due to there being no real perceivable difference, or else my ears have gotten worse over the past 20 years (most likely).

Tom

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Curiosity has got the best of me. I'll give it a try for the "fun of it". I will more than likely do it as Bob suggests by inserting the resistor so it does not affect the woofer. Now I need to wait for the resistors to arrive.

I'll take measurements of the response from 1kHz up with and without the resistors from my seating position and post them afterward. Should be interesting, or maybe not. We'll see. Not sure how it will affect the HPM-100's.
 
OvenMaster said:
Years ago, I did this on a pair of Avid 110 speakers with 1 Ohm, 10 Watt wirewound sandbar resistors. If rolling off highs very slightly is all it takes to make a good SS amp sound like a tube amp, then I have to say it was a smashing success...
Click to expand...

I would think that you'd want to use noninductive resistors for best results.
 
Someone needs to mention the great Stereophile debacle where Bob adjusted the transfer function of his amplifier to match another amplifier Stereophile selected. They, Stereophile, couldn't tell the difference between the two amps. Stereophile refused to publish the results as was agreed before hand.

Bob knows something about these things. How accurate his 85% estimate is is a matter of opinions. Maybe he is being optimistic. We probably don't know.
 
I think that Stereophile actually has that in their archives. I think that they're perversely proud of their whole role in that imbroglio with "Sideshow Bob" Carver.

http://www.stereophile.com/features/708/index2.html

you might find this letter from the late Harvey "Dr. Gizmo" Rosenberg interesting, too.
http://www.stereophile.com/asweseeit/487awsi/index1.html
http://www.stereophile.com/features/113/index1.html

This might be of interest too (although it's a somewhat different topic)
http://www.stereophile.com/asweseeit/673awsi/index.html

The thing y'all should remember about tubes ("versus" transistors) is that tubes are phenomenally linear amplification devices. Transistors are fantastically nonlinear devices (they want to be switches). One must play to the devices' strengths. One can certainly make good sounding amplifiers using either as the active devices, but the topologies of the two circuits (tube vs. ss) will likely be very different.
 
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I once read that the main "signature" of a tube amp is the predominant even order harmonics in contrast to a balanced mixture of even and odd order harmonics on solid state amps (which in different words means that less odd order harmonics make a sweeter sound).
 
IIRC, tubes are low order even and transistors are high order odd. That was a long time ago, about 15 or 20 years. Transistor amps have improved greatly since that statement.

To Mhardy, I wasn't a subscriber when that went down. I had misunderstood what happened. But the fact that Bob could do what he said gives a little credence to the OP's statement.

And I will read all of the links. I'm a big fan of Gizmo!

I wholeheartedly agree about the linearity of tubes (if you select the right part of the curve) and the switch aspects of transistors.
 
Dr. Gizmo (as far as I can tell) pretty much single-handedly drove the resurgence of interest in DHT SE amplifiers, at least in the US.

As to the even/odd order harmonic distortion... this is NOT a tube/transistor difference; it is a single-ended/push-pull difference. Even-order harmonics cancel out in a push-pull amp; but not in a single-ended amplifier. Tube amps tend to have proportionately more lower-order harmonic distortion. Put those two factoids together, and the even/odd order fallacy just seems to spring up.

http://www.audiokarma.org/forums/showpost.php?p=2905128&postcount=31

Note: so the pitch known as "concert A" in music has by convention a frequency of 440 Hz. That's the A above middle C for those as musically challenged as I. Folks would call the base frequency of 440 Hz (A440, aka "A4") a "fundamental" (tone) if you struck that key on the keyboard. Double that frequency is 880 Hz. You might be tempted to call that the "first harmonic" but it is in fact referred to as the second harmonic (which is the first even order harmonic distortion product of the fundamental). 880 Hz is also the fundamental frequency of "A5", i.e., the "A" note one octave above A440. Needless to say, if you have a single-ended amplifier (tube or solid state) with a significant amount of second harmonic distortion, the result will be "euphonious" -- the note and its partner one octave up. Is it accuracte? No. Is it pleasant to hear? Yes.

http://en.wikipedia.org/wiki/Piano_key_frequencies
http://en.wikipedia.org/wiki/A440
 
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