Latest krell saga

[KeithR]

Mep- do you have a local guy that Krell can pay to fix it?

 

[mep]

It is really unacceptable - this means a signal to noise ratio of about 75 dB against the specification of 120dB! Even the tubed Audio Research REF150 I am using has less than .001V in any of the channels. Was this measured without speakers?

Considering the expense and trouble to ship it, I would try to carry it to another place with a good mains supply, and measure it there.

That was measured with speakers attached. I took the measurements on the set of binding posts that aren't being used.

 

[microstrip]

That was measured with speakers attached. I took the measurements on the set of binding posts that aren't being used.

Can you repeat them with the speakers not connected? Just in case there is a grounding path between their negatives, creating a loop.

 

[mep]

I didn't know it was ok to turn on the amp with no load attached.

 

[microstrip]

I didn't know it was ok to turn on the amp with no load attached.

As far as I know it is not a problem. Specially because as you have shorting plugs in the input there will be no signals in the output. I have always burned in my solid state amplifiers in such way and never got problems.

 

[treitz3]

I didn't know it was ok to turn on the amp with no load attached.

I thought that was only the case with most tube amplifiers. If it's an issue with SS, then I'd be a little surprised.

 

[mep]

Can you repeat them with the speakers not connected? Just in case there is a grounding path between their negatives, creating a loop.

OK. No speakers connected: .007 left and .008 right. I shorted the probes together with the meter set to AC and it didn't null. It was .007 with the probes shorted. I also reconnected the speakers but unplugged the subs that are built into my speakers and powered the amp up andthere was no difference in the hum level.

 

[fas42]

OK. No speakers connected: .007 left and .008 right. I shorted the probes together with the meter set to AC and it didn't null. It was .007 with the probes shorted. I also reconnected the speakers but unplugged the subs that are built into my speakers and powered the amp up andthere was no difference in the hum level.

Interesting. My multimeter is nowhere of the quality of a Fluke, yet a figure of 0.007 is what I always get with shorted probes on AC -- is this a common figure?

At this stage it may be worthwhile slotting the amp into the system of a nearby agreeable friend, seeing if a completely different environment alters the behaviour ...

Frank

 

[microstrip]

Interesting. My multimeter is nowhere of the quality of a Fluke, yet a figure of 0.007 is what I always get with shorted probes on AC -- is this a common figure? (...)
Frank

Frank and Mep,

You have to scold your multimeters.
It is not possible to diagnose noise with such an high error in the multimeter.

 

[mep]

Which probably means the .007 and .008 AC readings aren't real if I can only null down to .007.

 

[FrantzM]

Frank and Mep,

You have to scold your multimeters.
It is not possible to diagnose noise with such an high error in the multimeter.

I agree ...

 

[mep]

I have had my Fluke 77 for over 30 years so I guess it's time for a new meter. In the world I live in, my meter would have been sent out at least yearly to be calibrated, but of course mine has never been calibrated since the day I bought it. It wouldn't be cost effective.

 

[fas42]

Of course, if you really want to know what's going on at the output terminals treat them as a source of an audio signal and record the noise using a PC sound card: then have a look using a virtual oscilloscope at what you have ...

Frank

 

[RBFC]

Mark,

Is there any physical damping (weight on top, etc.) that you can safely attempt to see if you can eliminate the hum?

Lee

 

[thedudeabides]

Hi mep,

I recognize that I'm a newbie on this site but have been involved with this hobby for some 30 years plus.

Perusing this thread and knowing what this can do to a music lover, is there a reason why you continue to try to resolve this issue versus selling and moving on?

At some point ................................?

GG

 

[LL21]

Hi mep,

I recognize that I'm a newbie on this site but have been involved with this hobby for some 30 years plus.

Perusing this thread and knowing what this can do to a music lover, is there a reason why you continue to try to resolve this issue versus selling and moving on?

At some point ................................?

GG

I can think of one reason to keep trying...because when the unit is otherwise breathtaking...if it just stopped that stupid buzz...you really want to fix it. Because if you go with another product that 'works'...you're back in the whole game of the treble, the bass, the soundstage...instead of 'its magic'...i like it just the way it is.

I went down this route on my Gryphon Antileon for a year...i ended up upgrading to Gryphon Colosseum...and finally got the Antileon fixed and sold it on recently in perfect working condition.

It is rare sometimes to find 'magic', and when you do and its 'just a buzz or a hum'...it can be worth the effort to fix it.

 

[mep]

Mark,

Is there any physical damping (weight on top, etc.) that you can safely attempt to see if you can eliminate the hum?

Lee

Lee-The answer is no. If I could get the schematic to this amp, I think the problem could be resolved. I have previously talked about a friend of mine who lives in WA and who is the most brilliant engineer I have ever met. I have been talking to him about this issue and here is one of the things he said: "I could easily believe that the magnetic field from that transformer is coupling into the input lines. Still though, if I had to bet it would be on the simpler problem of the supply filter caps, notably the ones associated with the front-end amps. We really need a schematic at this point."

The bottom line is that my friend is fairly certain (without seeing a schematic) that there is not enough filter caps on the front end of the amp.

 

[mep]

Hi mep,

I recognize that I'm a newbie on this site but have been involved with this hobby for some 30 years plus.

Perusing this thread and knowing what this can do to a music lover, is there a reason why you continue to try to resolve this issue versus selling and moving on?

At some point ................................?
GG

Yes, there is. I don't want to sell this amp to someone and have them be unhappy and complain and want their money back because it hums. I will have to disclose the hum and tell them they may or may not hear it at their house which will also cause me to have to lower my price. With all of my shipping and repair costs, I have well over $3K invested in this amp. Anybody want to buy it for $2K plus shipping?? If so, I will pack it up tomorrow. Please let me know.

 

[mep]

I agree ...

I bought a brand new Fluke 77 Series IV meter today.

 

[fas42]

Lee-The answer is no. If I could get the schematic to this amp, I think the problem could be resolved. I have previously talked about a friend of mine who lives in WA and who is the most brilliant engineer I have ever met. I have been talking to him about this issue and here is one of the things he said: "I could easily believe that the magnetic field from that transformer is coupling into the input lines. Still though, if I had to bet it would be on the simpler problem of the supply filter caps, notably the ones associated with the front-end amps. We really need a schematic at this point."

The bottom line is that my friend is fairly certain (without seeing a schematic) that there is not enough filter caps on the front end of the amp.

This is crazy -- basically saying the engineers at Krell back then when designing the beast couldn't pick that the amp was generating a bit of hum! Well, duuuhh ...

Frank