Tried it again and the 8ohm taps definitely sound better all day long compared to the 4ohm taps. Who knows?
Tube Watts vs. Solid State Watts - Any credence?
I've heard numerous times that Tube watts are not the same as Solid State watts when it comes to amps running speakers. For example, a 70 watt tube amp provides more power than a 140 watt solid state amp. Is there any credence to this or just sales talk and misguided listeners? If so, how could this be? One reason I ask is a lot of speakers recommend 50 - 300 watts of amplification but many stores have 35 watt tube amps or 50 watts tube amps running them. More power is usually better to run speakers, so why am I always hearing this stuff about a tube watt is greater than a solid state watt?
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- 120 posts total
10-10-15: Djfstthere's a good explanation for it as stated in my earlier post. I guess you missed reading it?? Bifwynne, yeah LOL! ;-) @Bombaywalla ... do you understand the term "[o]utput stage coupling is a combination of “ultralinear” and Audio Research’s patented “partially cathode-coupled” topology ..."?? I have a rough understanding of ultralinear .... No clue about "partially cathode-coupled” topology. Any idea??well, this is a serious case of the blind leading the lame but I'll give it a shot. I hope that somebody who knows more steps in.... 'ultra-linear' is a global negative feedback technique where, in a tetrode (4 active electrodes) or a pentode (5 active electrodes), some part of the output (usually present on the anode or plate) is fed back to one of the screen grids of the tube. The amount of output signal fedback depends on the tube type (KT88, 6550, 6V6, etc). David Hafler has patent on this where he fed back 43% of the # of primary xformer turns to the screen grid to linearize his amplifier. What this global negative feedback did was reduce output distortion, reduce output impedance & raise the output power to near-pentode levels. 'cathode-coupled' is a tube amplifier topology where the input tube is cathode coupled to the next gain stage tube. here are some pix for you to look at (you can drag your mouse over the pix without any harm. Click on the pix at your own risk!) http://www.bing.com/images/search?q=cathode+coupled+amplifier&qpvt=cathode+coupled+amplifier&qpvt=cathode+coupled+amplifier&FORM=IGRE the 1st pix itself should be good enough to allow you to visualize what I wrote. In the pix the 2 tubes are strongly coupled as there is a deliberate connection between the 2 cathodes. The issue with this amp is that the cathode of the input tube is at a very different voltage than the cathode of the 2nd tube. So, this amplifier becomes very sensitive to power supply variations & noise. Thus, I'm *assuming* (you know this goes!! ;-) )that ARC has a patented technology where they partially couple the 2nd tube to the 1st tube so that they can make the cathodes of both tubes operate at nearly the same voltage while still transferring the input signal to the 2nd tube to amplify it. I could be out on a limb here..... |
tube amps have no bass hence it's power mostly applied towards mids and highs while the solid state amps go full range. 70w of tube amp power will scream out louder on mids and highs, while same of solid state will cover full range and will have substantially lower volume vs tube. otherwise power is just product of voltage and current not just watts. |
Thanks Bombaywalla ... but what is the purpose of partial cathode coupling. Is it a form of local negative feedback?? Does it ameliorate some of the adverse affects associated with NFB that Ralph has written about, e.g., TIM distortion that raises the level of odd ordered harmonics?? ARC has used this type of topology for many years. |
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