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  #1  
Old 05-03-2008, 01:39 PM
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Foneman13 Foneman13 is offline
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Dynaco ST-410 ....... OMG !!!

While waiting to receive a Knight integrated tube amp, and a Kenwood tube receiver, both purchased to feed my original Heresy's .....the Audio Fairy hooked me up with a super clean Dynaco 410 for $50 ----I KNOW !!!!----
how blessed am I ??!??....
So, I hooked it up with my Advent receiver as a pre-amp, and NOW I understand how BIG POWER shows up at low volume levels.....
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  #2  
Old 05-03-2008, 04:09 PM
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Nice. I'd love to score a Dynaco power amp. $50 is a steal for one of those.
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Old 05-03-2008, 10:20 PM
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Can you explain? 1 watt is 1 watt.
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Old 05-03-2008, 10:45 PM
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Quote:
Originally Posted by Tromatic View Post
Can you explain? 1 watt is 1 watt.
NO, I can not explain it !!!!...


Can you?....I am certainly interested in understanding this experience....Are you implying that I am fallen subject to the
PLACEBO EFFECT ?




Not that there is anything wrong with that
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  #5  
Old 05-04-2008, 02:21 AM
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No, trying to understand how having big watts on tap translates to low volume.
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Old 05-04-2008, 02:30 AM
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Marantz 500 Marantz 500 is offline
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The amplifier's damping factor has to do with it:

"UNDERSTANDING DAMPING FACTOR
Loudspeakers have a mind of their own. You send them a signal and they add their own twist to it. They keep on vibrating after the signal has stopped, due to inertia. That's called "ringing" or "time smearing."
In other words, the speaker produces sound waves that are not part of the original signal.
Suppose the incoming signal is a "tight" kick drum with a short attack and decay in its signal envelope.
When the kick-drum signal stops, the speaker continues to vibrate. The cone bounces back and forth in its suspension. So that nice, snappy kick drum turns into a boomy throb. Fortunately, a power amplifier can exert control over the loudspeaker and prevent ringing. Damping is the ability of a power amplifier to control loudspeaker motion. It's measured in Damping Factor, which is load impedance divided by amplifier output impedance. Let's explain.
If the speaker impedance is 8 ohms, and the amplifier output impedance is 0.01 ohms, the damping factor is 800. That's a simplication. Since the speaker impedance and amplifier output impedance vary with fre-
quency, so does the damping factor. Also, the impedance of the speaker cable affects damping. Thick cables (with low AWG) allow more damping than thin cables with (high AWG). The lower the amplifier's output impedance, the higher the damping factor, and the tighter the sound is. A damping factor of 1000 or greater is considered high. High damping factor equals tight bass.

How It Works
How does an amplifier control speaker motion? When the loudspeaker cone vibrates, it acts like a microphone, generating a signal from its voice coil. This signal generated by the speaker is called back EMF (back Electro Motive Force). It travels through the speaker cable back into the amplifier output, then returns to the speaker. Since back EMF is in opposite polarity with the speaker's motion, back EMF impedes or damps the speaker's ringing.
The smaller the amp's output impedance, the greater is the effect of back EMF on the speaker's motion. An amplifier with low output impedance does not impede the back EMF, so the back EMF drives the loud-
speaker with a relatively strong signal that works against the speaker's motion. When the speaker cone moves out, the back EMF pulls the speaker in, and vice versa. In short, the loudspeaker damps itself through the amplifier output circuitry. The lower the impedance of that output circuitry, the more the back EMF can control the speaker's ringing.
To prove it to yourself, take a woofer that is not connected to anything. Put your ear next to the cone and tap on it. You might hear a low-pitched "bongggg" if the speaker itself is poorly damped. Now short the
speaker terminals and tap again. You should hear a tighter thump.
Damping factor varies with frequency. As you might suspect, damping factor is most important at low frequencies, say 10 Hz to 400 Hz."
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  #7  
Old 05-04-2008, 04:24 AM
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What does a high WPC rating have to do with damping?
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  #8  
Old 05-04-2008, 07:30 AM
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A more powerful amp usually has a much higher damping factor than a lower-powered one.
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  #9  
Old 05-04-2008, 07:39 AM
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You may have learned something. The very clean wide bandwith Dyna will grossly outperform most any tube amp.
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  #10  
Old 05-04-2008, 08:11 AM
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thanks Marantz

Very well explained!
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Old 05-04-2008, 08:17 AM
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The only thing wrong with the explaination is the speaker wire negates the whole theory of the damping factor having much control over the sound. Speaker wire resistance is many magnitudes higher than the amps source impedance. This makes the effective damping factor in the whole system very low regardless of the amps very high damping factor.
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Old 05-04-2008, 08:36 AM
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Doesn't that depend on the length and properties of the speaker cables used? And wouldn't an amp with a low damping factor to start with be affected in the same way by speaker cable resistance, lowering damping factor even more?

I am no expert, I just find that there IS (can be) a big sound quality difference using a more powerful amp compared to a smaller one, even if you're not playing very loud, and the damping factor explanation seemed to make sense to me.
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Old 05-04-2008, 08:42 AM
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Well yes but the great qualities of a super amp are realized with regular zip cord speaker cable. 3 meters of 16 gauge adds about .4 ohms. Your explaination of damping factor is great but I don't think it is the reason super amps sound so great. Of couse some tube amps have damping factors of 10 or so. This can't be good for tight quality bass.
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  #14  
Old 05-04-2008, 08:44 AM
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Quote:
Originally Posted by Foneman13 View Post
So, I hooked it up with my Advent receiver as a pre-amp, and NOW I understand how BIG POWER shows up at low volume levels.....
Ignoring the Damping Factor wars, which has been well-discussed elsewhere, back to the thread......

That sense of effortlessness from a big amp can be quite compelling, especiallly if its your first experience with it and with efficient speakers like yours Foneman, it will be even more pronounced.

While I still like my tube amps, I do like hooking up the old, road-weary Hafler P500 (250wpc) occasionally to my JBL or UREI studio monitors for fun. Its a nice effect but can, and will likely, wear off over time.

If you choose to keep the Dynaco, however, get it serviced as there are old parts in there. At the least, fuse your speakers.

Cheers,

David

Last edited by dshoaf; 05-04-2008 at 11:53 AM. Reason: spelling - doh!
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  #15  
Old 05-04-2008, 08:54 AM
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I can't really choose between high power SS and tubes, so I use both in different systems/rooms. I find that my Quad II amps and my Dynaco ST70 are great for listening to classical and jazz, but they dont't excel when it comes to pop/rock music, at least in my system. For pop/rock I much prefer my Kenwood Basic M2, Nikko Alpha 440 or Marantz 170 DC power amp. And I do have too many amps (can't use them all at the same time)... I was on the verge of buying a Dynaco ST410 a month ago, but the deal fell through - seems to be a cool amp!
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