[klaus@odyssey]

1.  124 V...this is exactly why I am so hot on the issue of biasing.....124 to, let's say a standard 120 V setting is HUGE !!!!   Huge in any amplifier design btw. 

2. Synergy with the Maggies is one of the 2 best I've ever found...just awesome...

3.  22 +  mV  would be a bit too much for my own personal taste,  but because there are dozens and dozens of different tweaks and upgrades out there in my nearly 7000 amps,  they also behave different in different systems,  et al.....

4.  Honestly,  don't listen to others about what's best on the test points...use your own ears,  and float your own boat......


VOTE !!!  AND STAY SAFE !!!!

[arfan]

Thanks again Klaus. Good to know and appreciate your opinion on the  maggies and Odyssey amps, it helps to hear an expert on the subject and reinforces what I'm hearing.
When you Say too much on the bias setting, are you referring to a warmer setting? I have an Audible Illusions M3B Tube pre newest update and the match gives goose bumps to these old ears.

[klaus@odyssey]

In general and for most amps:

-  higher bias = rounder, fuller, more bass

- lower bias the opposite = faster, leaner, more detail oriented as a result


that's why I optimize the bias according to the tonal balance of the speakers,  within reason......but yes, if you want to get the absolute maximum of what's possible in the amp,  then we'll have to bias it just right....if that falls off,  then so does the sound.  That's also why it's a good idea to have me to adjust for a new owner if bought used,  and that's why I'm banging my head against the wall  when there's an idiot complaining about a used amp's performance when the bias is obviously off.

Again,  I can just go ahead and bias the amp 2-4 mV less than optimum,  but that's not really in my blood.....if you can go to 11,  then go to fukking 11 !!!!

[brad1138]

I do want to check/adjust the bias in my Stereo Kismet in Khartago case. This appears to be the place to request the instructions. My Moabs love a warm amp, and as cool (temp wise) as my Kismet runs, I think it might be worth the check.

Klaus you already have my email, PM me if needed. (no rush)

Thank you!

PS, always go to 11!    https://www.youtube.com/watch?v=KOO5S4vxi0o

[brad1138]

that last little bit was what i was missing.

since it looks like many have asked, and i finally have complete instructions, i built an image to help everyone out.
by the way, to adjust the offset it is much easier if you have a ground lead that you can clip into the board. you might want to pick one up before you start.

Again, thank you for that.

On the stereo version amps, wouldn't it be fine to just read bias from the speaker terminals? You wouldn't need a clip.

[brad1138]

My bad, I read that wrong, You can read offset from spk terminals, not the bias. (Not the positive anyway)

[brad1138]

OK, I am fairly sure I have my head around it. It would have been easier if not for typos and contradictions in the posted instructions. Also the difference between mono and stereo complicate it a bit.

Johns nice picture is great, but it says TP6/7 when I am pretty sure he meant TP5/6.

The 1st part for the written instructions say to use TP1/2 & TP5/6, with no mention of TP3/4 or TP7/8. Then towards the bottom, it says use TP3/4 and TP7/8 and ignore TP1/2 & TP5/6....

I really don't know for sure which is correct, and why not use all 4 per side?

I think Johns picture instructions are the most easy to follow, short the typo.

If anyone could offer clarification on which TPs to use, that would be great.

It seems clear that you can connect the negative DVM lead to the negative speaker terminal, and leave it there for all testing (per side). The positive would go to the corresponding positive speaker terminal for offset and the "TPs" for Bias adjustment.

Thanks for the help, I am REALLY not trying to be obnoxious. 

[klaus@odyssey]

OK,  Brad et al,

You only use 1 test point per side....!!!!!!!!!!!!!
Either TP  3 or 4 on one side,  and either 7 or 8 on the other....you only use the one with the highest value per side of the board and completely ignore the other 3 of that side !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

On another note,   Brad,  your Candela is ready to go !!!!

[brad1138]

OK,  Brad et al,

You only use 1 test point per side....!!!!!!!!!!!!!
Either TP  3 or 4 on one side,  and either 7 or 8 on the other....you only use the one with the highest value per side of the board and completely ignore the other 3 of that side !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

On another note,   Brad,  your Candela is ready to go !!!!

OK, thank you again. I understood you only use one, but you check 2 at first to verify which one is higher.

I spoke with Klaus on the phone just a few hours ago, he clarified to use the red speaker terminal, which is ground, for bias adjusting.  I always have it in my head that black is ground, so that confused me a bit.

[brad1138]

I just spoke to Klaus again for reverification. Red is not ground (I called him after I verified that with an ohm meter), but it is what is supposed to be used along with TPx for bias adjusting.

Every set of instructions posted in this thread says to use ground and TPx for bias THAT IS INCORRECT. He asked me to post that here, and he may chime in about it also.

[brad1138]

OK, I bought a 2nd Multimeter to compare and make sure they were both accurate.

Klaus recommends bias between 18 and 24 mV, my Kismet was 12 mV on both sides  . The offset was about 3 mV on left chan and 13 mV on right. Both within an acceptable margin. I am going to aim for 21 mV and 0 mV and see how it it sounds, then go from there.

[klaus@odyssey]

Anybody trying to do this on your own,  CALL ME  FIRST !!!!!!!

[Hooge]

Old thread here but it's a gem. I successfully just biased my 12 year old Khartago. One side was at about 18 mV and the other was about 21 mV. I assume this amp was biased at 21 mV at one time. I am trying the 24 mV and love the sound, just a touch warmer. Sounds fantastic. Love this amp! Thanks!

[LeadEars]

1.  124 V...this is exactly why I am so hot on the issue of biasing.....124 to, let's say a standard 120 V setting is HUGE !!!!   Huge in any amplifier design btw. 

While I'm waiting for my used Khartago Stereo SE to arrive, and knowing I'll need to check the bias on it - my home voltage is averaging 124.5v for the past few days - just out of curiosity, will the ~21mV value typically go toward -18mV or toward -24mV as the mains voltage increases?

Thanks - I'm digesting all this as best I can while waiting...

Mark

[LeadEars]

It might help if I rephrase my question, especially now that I have my Khartago set up & have started letting it "charge" - the sound is already incredibly better than my old Adcom GFA-555, but more on that later...

What I'm asking is: Assuming the amp was biased for 120v, if the mains voltage changed to 125v, without re-biasing, would the sound shift towards "warmer/fuller" or "colder/leaner"?

[LeadEars]

I hate to bump this, but I'd still really like an answer to the question....

[Hooge]

Ive been using AI for questions like this. Here’s what AI says:

Yes, an increase in house electricity from 120V to 124.5V (a ~3.75% increase) will affect the bias current of your power amplifier.

Because your amplifier's power supply transforms the incoming AC voltage into higher internal DC voltages (B+), a higher input voltage generally results in higher plate/collector voltage. This typically increases the bias current, causing the amplifier to run hotter.

Here is the breakdown of the impact:

Will it affect the bias?
Yes, the bias current will increase. If you biased it at 120V, it will now be running at a "hotter" bias point.

Will it sound leaner or warmer?
The increased bias/voltage usually leads to a warmer, slightly thicker, or more saturated sound, especially in tube amplifiers.

Risks? A 4.5V increase is generally within acceptable limits for well-designed equipment, but it may cause the amp to run noticeably hotter, potentially shortening tube or component lifespan.

Recommendation:
It is highly recommended to re-measure the bias with your meter to ensure it has not exceeded the maximum recommended dissipation for your tubes/transistors. If the voltage in your area is consistently high, you may need to bias the amplifier while the voltage is at 124V-125V, or consider using a voltage stabilizer.

[klaus@odyssey]

AI,  heh ???

But yes,  higher bias results in warmer, hotter output devices.....which results in "warmer" more bass oriented sound with lessened dynamics and detail information.........

There is a rather narrow deviation in bias settings,  where the "optimum" setting drifts into an audible decrease of sq.  I can only speak of the amps that I have had experience with,  but figuring that every amp has to be biased,  it seems universal.  There is a "perfect" optimal setup point,  and any changes from that will ultimately affect the sound...that's why I'm quite maniacal abut customers providing their voltage readings.
And,  of course,  by custom biasing pretty much every single amp out there (out of the 8000 + amps I've made so far probably 98 % of them were custom biased)  there is a chance that 2nd hand users might get an amp where the bias for that new owner is off...sometimes wayyyy off,  which also results in...let's say less than stellar performance.....


On the other hand,  with decreased bias you'll end up in a more "information"  oriented sound,  where, if severe enough of a drop in mV's,  the full bodied magic kind of disappears.......

Tube owners know all about that in most cases,  but the same applies to ss as well.........

[LeadEars]

Thank you for the info!  As a previous owner of tube amps, I was aware of how important bias is, but never knew which direction in mains voltage did what.  I've been monitoring my voltage at home for weeks now, and it's pretty stable at 125.6v, more than the 124v I thought at first.

I bought a used Khartago Stereo SE recently & love the sound, and I have no idea what it was biased for, but odds are it was for a lower voltage, of course, so I'd like to re-bias it myself.  In the meantime, I was just wondering what to expect, in other words, which direction it would go when re-biased...

Thanks again!