Does anyone care to ask an amplifier designer a technical question? My door is open.

What can I expect to pay for a recap (plus any normal servicing)? I can actually drop off the amp at Krell myself (they are an hour or so away).

While it might be old enough that some of the filter capacitors could be getting near failure, that is not the problem here. Filter caps don't make static noise. Is this problem in both channels or just one? If one, I would suspect the input transistors.

My pre amp is a Conrad Johnson Classic II. Output is 200ohms.
The Krell input 47K--despite this, I am using an attenuator before the amp inputs.

The input impedance has nothing to do with whether you need attenuation or not, FWIW. I'd get an estimate from Krell before deciding your course.

When an amp specifies a maximum current what exactly does that mean and how is it relevant? On another thread there's discussion of an amp that has max current of 29 amps and puts 100 watts into 8 ohms. Since 29 amps would be a whole lot more than the current into 8 ohms at 100 watts or into any normal load this must have some other relevance. 

Power is equal to volts times amps and is also equal (thru Ohm's Law) to current (squared) times Ohms.
In this case, to make 100 watts into 8 ohms, you divide 100 by 8 and take the square root, which is about 3.4 amps. That's all thats needed to make 100 watts if the load is 8 ohms and it makes no difference what kind of amplifier it is. So what is the 29 amps??

Let's do the math the other way- 29 squared is 841 watts if into a 1 ohm load, but if this amp can double power as impedance is halved, clear down to 1 ohm, the wattage would 800 watts, not 841! The math can't lie about stuff like this, so clearly if the 29 amps is real, it has to be something else. Often it is- its the amount of current that can flow if the power supply is shorted for 10 milliseconds. Mostly that's a measure of storage that the capacitors in the power supply have and probably does not say much about how the amp measures or sounds. Also FWIW, there are tube amps that have that much 'current'. IMO, the 'current' (please note quotes) is often a misleading figure as current can't exist without voltage no way no how.

Whose thread is this?

@atmasphere It is in no way an excuse for bad specs- and in fact our amps have some pretty good specs (if proper measurement technique is used, which means **don’t ground a speaker terminal during testing**, which is the mistake that almost everyone except Charles Hanson made/makes). I suspect you didn’t read the paper at the link very carefully, since you claimed that you read it, yet still with the remonstrations!

Do you think I am so stupid as to ground floating outputs. GEEEEZ Get off my back. I go into the balanced input of the Soundtech. Ive given your amplifier every opportuinty to meet your specs and it just does not. Would you like to send me one that does?

Ive measured you feedback to be less than 0.1 db with an 8 ohm load. I simply disconnected the feedback and the meter moved less than 0.1 dB. Is that how you measure it? Output regulation is about 9 dB at 450 mA idle and is certainly idle dependent.

Distortion I can never get below 1% unless I really want to heat up the tubes.

Ive read you paper to death and makes little sense to me or anyone skilled in the art. Rather than me keep reading it how about you work on re-writing it. Im happy to help.

The history of the 6SN7, has nothing to do with its current use. Shall we publish the 6SN7 application notes for the whole RC series? Will the writing make it a better tube?

All I know about your amplifier is that if I add 12 dB of feedback it sounds a lot better to everyone that has come to hear it. Perhaps you have not tried this much. Because the amp has good stability it takes this feedback nicely and gets us under 1% THD and a regulation of 3 dB vs 9 dB. Makes the QUAD 57 sound really nice in brushes, clean tuneful bass, clear vocals. Why are you so opposed to feedback? Ive read Crowhurst, he taught me how to make good transformers.

I dont go looking for amps to modify, other people modify my amps. All they do is put in silly fast rectifiers. WOW. People modify cars. If 12 dB of feedback makes the M-60 sound better to all the people I have demonstrated if for then it does for them. Look, It seems we have hit a nerve here, lets be nice and lets all try to make better amps and less story.

Actually Roger, I did that earlier. You must not have read the post?
The loading is for the benefit of the preamp, if its sensitive to RFI. If not, no loading is needed. IOW if you need loading to deal with brightness, the preamp has a problem with RFI. The loading resistor detunes the tank circuit caused by the cartridge and tone arm cable and thus knocks out the RFI caused by the tank circuit when driven into excitation by the energy of the cartridge. Here’s a couple of links that address this in greater detail; the link to the What’s Best forum includes posts by Jonathan Carr, a noted designer of LOMC cartridges. The one to Jim Hagerman’s website has some of the math and some charts that show whats going on:
http://www.hagtech.com/loading.html
https://www.whatsbestforum.com/threads/cartridge-loading-a-misnomer.15077/

I read both links. The first is common knowledge and nothing about RF. The second is long so if there is something in particular you want to me to read please quote it here. Are we playing "Wack A Mole' here?

Im really tired of RF being the devil for everything. Usually if there is RF sensitivity you will hear an AM radio station. If there aint no radio coming in there aint no RF. Lets get real please.

Power is equal to volts times amps and is also equal (thru Ohm's Law) to current (squared) times Ohms.
In this case, to make 100 watts into 8 ohms, you divide 100 by 8 and take the square root, which is about 3.4 amps. That's all thats needed to make 100 watts if the load is 8 ohms and it makes no difference what kind of amplifier it is. So what is the 29 amps??

HI, I was involved in that discussion about the Benchmark amp. Some of us were trying, without much luck, to advise the owner not to bridge the amps into his speakers. Then we got into current. Then the whole thing fell apart and I left. 

To answer your question. 100 watts at 8 ohms is 40 volts peak. If you have an electrostatic or other speaker that goes down to an ohm or two you will need a lot of current to play trumpet music at full level. You may need 40 amps to get your 40 volts at 90 degree phase and most amps will be very unhappy. The Beveridge ESL required 1500 VA to play Miles. There was no way to get that through a reasonable transformer so we made Direct Drive 3000 volt amplifiers that provided 1/2 amp of current. 

@oldtecg05
 Whose thread is this?

I thought it was mine. I dont mind a bit of controversy as long as its Gentlemanly and with some sense of humor. Its the sense humor that I find lacking.