The future of preamps

I took a look at the statements in the manual for the Krell 700cx that pertain to DC. As someone having no dog in this fight, I would offer the following comments:

1)The relevant section on page 14 (pdf page 18) begins with the statement that:

The high DC output of tube preamplifiers may exceed the DC protection circuitry of Full Power Balanced amplifiers. Excessive DC level in a signal can damage amplifiers, speakers, or both. The coupling capacitors in Full Power Balanced amplifiers must be engaged when using a tube preamplifier.

Note that the statement does not refer just to tube preamplifiers having DC coupled outputs, it also encompasses the great majority of tube preamps that have coupling capacitors at their outputs. How are those preamps supposed to output "high DC"?

Also, note that when it refers to "the high DC output of tube preamplifiers," it does not make any reference to fault conditions. As if to say that all tube preamps routinely output high levels of DC, when operating normally. Which is nonsense, of course.

2)On page 19 (pdf page 23):

Q. My speakers are rated for 150 Watts. Are the Full Power Balanced 400cx or 700cx models too powerful for them?
A. No. A speaker seldom is damaged from overdriving. More often, damage occurs when an amplifier that lacks sufficient power is asked to handle heavy demand situations such as high playback levels. These amplifiers may have very high 8 Ohm power ratings, but in heavy demand situations they can be driven into clipping (in which DC current goes to speakers due to loss of amplifier power). Clipping can damage speakers.

This reflects a complete misunderstanding of how overdriving an underpowered amplifier can sometimes damage speakers. It has nothing to do with DC. The reason is that a clipped waveform has increased high frequency content relative to the original signal, which can damage tweeters.

All of the above doesn't speak well, to say the least, for the credibility of whoever wrote the statements in the manual cautioning against the use of tube preamps without the amp's coupling capacitors being in place.

3)I have participated extensively in these forums for more than five years, and I cannot recall a single instance in which an amp or speakers were reported as having been damaged by DC emitted by a tube preamp.

4)I second all of the comments by Charles about the credibility Ralph has established via his lengthy track record as a respected designer and manufacturer of very high quality equipment, and that he has further established as a result of his extensive contributions to these forums.

Regards,
-- Al

Al,
You are the man! At this point I don't know what more "need be said".
Charles,

01-02-14: Charles1dad
Al,
You are the man! At this point I don't know what more "need be said".
Charles,

Nothing more needs to be said, this is all simply a waste of cyberspace. Wc65mustang has this nailed down pretty well.

This guy is either a troll who likes to talk trash about tube preamps or an absolute idiot. Take your pick. I think we should take votes. This is the most absurd thing I ever heard; Have the manufacture give in writing that his preamp will not sh-t on his tube amp. Maybe I should have my Dentist give me in writing that the new crown he put in my mouth will never fall off, never break, or never have to be redone in my life time. Absolute nonsense. Ralph I would not sell this nut a preamp if he stood on his head and offered you double the retail price. If you do I warned you he will call you every day saying something isn't quite right and he thinks DC is poising his pets.

So far no one has pointed out the obvious so maybe it does not need saying, but a review of this thread and several others leads one to believe that George is "defending his turf" by talking trash about competitive active pre-amps. And I say this reluctantly, as an owner of one of his passive Lightspeed Attenuators. The LSA is in the opinion of many on this board (myself included), the biggest bargain in high end audio. However, it's not a replacement for a pre-amp if you have more than one source and it does lose out in SQ, to my ears, to actives at 10-20x the price. I do not have the technical know how to assess his claims vs Ralph's but if Almarg says that the marketing literature in the Krell manual is off the mark, then it is off the mark. He's an EE w no dog in this fight and a demonstrated track record of providing excellent interpretation of complex (to me anyways) technical and mathematical issues.

George, your generosity in making your product available at a bargain price and your intellectual property available to the DIY community is well known and exemplary. Unfortunately, you do not do your product or your reputation a service by trashing competitors. While many of us here know that you are "in the business", that should have been disclosed to the OP at the very least, to allow him to evaluate potential motivations.