Khartago Kismet amps and Allen Wrenches, DC Offset & Bias...

Chops · « **on:** 23 Sep 2015, 10:05 pm »

I've had this amp going on 2 years now and have yet to open it because out of my several sets of allen wrenches, I don't seem to have the right size. Can someone verify and let me know what size is needed? I'd really appreciate it!

Many thanks in advance!

JackD · « **Reply #1 on:** 23 Sep 2015, 11:37 pm »

Chops

Try 5/64 that is what most use for hex head case screws.

Charles Calkins · « **Reply #2 on:** 23 Sep 2015, 11:47 pm »

Are the hex screws SAE or metric? As you know there is a difference. Do you have both SAE and metric Allen wrenches?

Cheers
Charlie

Chops · « **Reply #3 on:** 24 Sep 2015, 01:03 am »

JackD... I'm certain I've tried that one before, but I'll try again when I get a chance.

Charles Calkins... Yes, I have both sets, and have tried all of them. No dice. Again, when I get a chance, I'll try them out again.

Thanks guys!

Tomy2Tone · « **Reply #4 on:** 24 Sep 2015, 01:09 am »

My wrench set has the 1/8 Allen and it's an exact fit for my Stratos cases.

Tomy2Tone · « **Reply #5 on:** 29 Sep 2015, 03:52 pm »

Hey Chops, were you able to find an Allen that fits?

Chops · « **Reply #6 on:** 3 Oct 2015, 12:54 pm »

Quote from: Tomy2Tone on 29 Sep 2015, 03:52 pm

Hey Chops, were you able to find an Allen that fits?

I couldn't sleep much last night, so I've been up since around 4am (went to be shortly after 2). I just now saw your question so I shut down the system and pulled the amp.

1/8" Allen is too small, 5/32" is too big, and none of the metrics fit. I noticed one of the screws was loose and I was able to remove it by hand with my fingers! Then with an almost perfect size Torx bit, was able to remove the other three with very very little effort. I just barely touched them and they spun freely.

Anyway, here's the "guts" pics finally. Now I can call up Klaus and go through the re-biasing of this amp. And please excuse the dust. That'll all be cleaned up shortly.

I imagine this will be one of the bits I'll be tweaking...

germay0653 · « **Reply #7 on:** 4 Oct 2015, 03:17 pm »

I need to call Klaus. When I purchased my Khartago monos, in 2010, he couldn't could fit the reference SL caps on the PCB. I do have them near the heatsinks so I wonder if they were able to make smaller versions that fit on the board. I've been meaning to call him, just haven't gotten around to it, about the newer faceplate as I have the ones with only the LED and would like to get the newer version. Also saving my pennies for an HT-3 to replace an aging ADCOM GFA-5503 heat radiator.

gregfisk · « **Reply #8 on:** 4 Oct 2015, 04:55 pm »

Chops, is that flex conduit running of over the PCBs? If so, I assume it is being used as shielding?

marflao · « **Reply #9 on:** 4 Oct 2015, 05:32 pm »

Quote from: Chops on 3 Oct 2015, 12:54 pm

Interesting that the cables which are connected to the RCA sockets are a mix of two Gronebergs (Quattro Ref and TS premium).
Thought either one or the other?!

Chops · « **Reply #10 on:** 4 Oct 2015, 05:45 pm »

Quote from: gregfisk on 4 Oct 2015, 04:55 pm

Chops, is that flex conduit running of over the PCBs? If so, I assume it is being used as shielding?

Yes, it's what Groneberg uses on their TS-Premium line of cables. I'm sure it provides some kind of shielding.

Chops · « **Reply #11 on:** 4 Oct 2015, 05:48 pm »

Quote from: marflao on 4 Oct 2015, 05:32 pm

Interesting that the cables which are connected to the RCA sockets are a mix of two Gronebergs (Quattro Ref and TS premium).
Thought either one or the other?!

Yeah, I don't quite get that either. Unless that shielding was added or taken away for some reason.

marflao · « **Reply #12 on:** 4 Oct 2015, 05:52 pm »

Quote from: Chops on 4 Oct 2015, 05:48 pm

Yeah, I don't quite get that either. Unless that shielding was added or taken away for some reason.

If I remember correctly Klaus said once that a TS Premium would be too heavy for that distance. That´s why I have a quattro ref in my cyclops for this connection.

But maybe things have changed

bunky · « **Reply #13 on:** 4 Oct 2015, 09:22 pm »

TS Premium cable without the shielding is the same color as the Quattro reference.

Chops · « **Reply #14 on:** 4 Oct 2015, 10:15 pm »

You can see much better in this pic that it is in fact the Quattro Reference cable. I guess for whatever reason Klaus felt it necessary to add shielding to them.

marflao · « **Reply #15 on:** 5 Oct 2015, 09:17 am »

Quote from: bunky on 4 Oct 2015, 09:22 pm

TS Premium cable without the shielding is the same color as the Quattro reference.

Quote from: Chops on 4 Oct 2015, 10:15 pm

You can see much better in this pic that it is in fact the Quattro Reference cable. I guess for whatever reason Klaus felt it necessary to add shielding to them.

Thank you both for clarifiaction.

Chops · « **Reply #16 on:** 7 Oct 2015, 03:42 pm »

You're welcome, sir!

klaus@odyssey · « **Reply #17 on:** 8 Oct 2015, 05:47 am »

The shielding is part of the TS Premium system...I can add some mantle on the Quattro if so desired, but wouldn't do for the whole length of the cable, as it becomes rather stiff and heavy...have done so in the past a few times, but rather not....also, all depends on the rest of your system,,,,,,.......sometimes it's even better to use the lower Series III as an input cable....balance, balance, balance, synergy, synergy, synergy, experience, experience, experience.....however, for the output cables the mantle is awesome, and quite often I used it over Quattro, which I kind of prefer in the amps......kind of.

Chops · « **Reply #18 on:** 17 Oct 2015, 02:27 am »

Thanks to a little extra guidance from Klaus over the phone tonight, I finally got around to re-biasing my amp.

Measuring offset first, the left ch was at 1.0 mV, right ch however was way up at 9.5 mV! I kept the left ch at 1.0 mV and got the right ch down to around 1.0 mV as well. After that, I moved on to the bias. The left ch was at 18.8 mV while the right ch was at 19.9 mV. Both are now on the hot side of 21 mV, about 21.1 - 21.2 mV. I'll leave it like this until tomorrow sometime and I'll check things again and adjust as necessary. I have no clue how the right ch offset ended up that high. Strange.

All I can say is that the sound is a tad fuller and smoother, and more importantly, output level between both channels are now even! Finally.

Chops · « **Reply #19 on:** 21 Oct 2015, 04:41 pm »

Well there haven't been any replies here since my last post, but figured I'd post a follow up...

So here I am revisiting the offset and bias again this morning. Offset was back up around +2 mV on both channels, and bias up around 23-24 mV. Keep in mind, these measurements are in a constant state of flux, about +/-1 mV in either direction. Such as the offset... I reset it as close to 0 mV as possible, but it constantly swings anywhere between -01.3 mV all the way up to +01.8 mV. It does this on either channel. I don't know if this is typical or if these little blue adjustment pots simply suck. I mean, I've been sitting here nearly 30 minutes monitoring both channels and there's just about a full 3 mV swing. That just doesn't seem right to me.

I honestly don't know how much of a voltage swing is acceptable on this amp. I know Klaus always says it's impossible to achieve 00.0 mV, and that's understandable, but is 01.5 mV plus or minus acceptable?

In a few minutes, I'll be revisiting the bias... Again.