[disc4]

Is it normal for the Odyssey cases to be hot to touch and measure 30 degrees F above ambient temperature with no sound playback for 8+ hours?

My Stratos HT3 (two PCBs) measures 105F with usage and the same temperature with no sound for 8 hours.  There is good air flow and the units are not on top of each other.  My Kismet in Khartago (smaller) case is also around 105F after playing for several hours and 95F after no sound for 8 hours.

Our Stratos Kismet Stereo does not have this issue and is cooler to the touch.  I realize the HT3 generates more heat as it is packed to the brim inside.

Both HT3 and Khartago were calibrated over the past few days (0 offset, 19.5 to 20mv Kismet, 19 bottom board of HT3, 17.5 top board of HT3).  The stereo HT3 board was recently replaced.

[geerock]

Sounds too hot to me.  I don't get near that heat when they are playing.

[hi_watt]

Interesting, as my Khartago's don't get as hot as I'd expect them to as they idle. I hope Klaus chimes in asap.

[charmerci]

. I hope Klaus chimes in asap.

Much better to call.

[klaus@odyssey]

BIAS !!!!!!!!!!!!!

[geerock]

BIAS !!!!!!!!!!!!!

And there you have it!

[disc4]

Klaus has replied that he will be exchanging the HT-3 PCB at issue - thanks again Klaus!

As a note both amps were biased as specified on these forums 19.5 to 20mv Kismet, 19 bottom board of HT3, 17.5 top board of HT3. These values move slightly while I am measuring them, I assume due to fluctuations in line voltage.

Also all channel offsets were correctly set to 0 mv, +/- 1 mv.  The Khartago has been powered on for many months (outside of power outages) and I confirmed the offset remained at 0 mv when I checked it this week, and bias remained as noted above.

The new stereo board of the HT-3 was the culprit for that amp.  After everything was iteratively biased / offset at 0, the left channel became very hot after a day (as measured on the metal heat sink inside) and I could no longer set the offset on the bad channel (it was far off from 0 mv, would not budge from about 300 mv or so from my memory).  Soon after, I heard crackling sounds in the associated speaker and shut it off immediately.

On the Khartago, I occasionally hear some low volume, high pitch sounds for a few seconds.  Not sure if it's line noise or some component (capacitors?) near end of life and causing increased heat.  I have a multimeter, Rigol oscilloscope, and IR temp. sensor if anyone had any troubleshooting steps.

[klaus@odyssey]

The new stereo board of the HT-3 was the culprit for that amp.  After everything was iteratively biased / offset at 0, the left channel became very hot after a day (as measured on the metal heat sink inside) and I could no longer set the offset on the bad channel (it was far off from 0 mv, would not budge from about 300 mv or so from my memory).  Soon after, I heard crackling sounds in the associated speaker and shut it off immediately.

-----------------------------

This is an older amp and I exchanged the board with another used one and added some upgrades...however,  obviously there was an issue.......keep in mind that for the exchange,  I simply can't put in a new one,  so a used board has to do......of course I test everything out,  but again,  it's used and it worked and biased out fine when it left here....if the issue remains,  you'll have to test your Av unit for DCV offset.





On the Khartago, I occasionally hear some low volume, high pitch sounds for a few seconds.  Not sure if it's line noise or some component (capacitors?) near end of life and causing increased heat.  I have a multimeter, Rigol oscilloscope, and IR temp. sensor if anyone had any troubleshooting steps.

-------------------

Could be....could also be AC  or if you have tubes,  then tube related issues...sometimes it's simply a charge from the carpet or the actual air in your room........

[disc4]

As an update, there are still issues with the heat of the Kismet in Khartago.  The case is currently 20 degrees F above ambient temperature (measured on sides and top of case with an IR thermometer), still hot to the touch. 

Any advice would be welcome.  Does the thermal material touching the heat sink require periodic replacement?  Any other ideas?  The Odyssey audio sounds so good from that amp that I am loath to change anything!

I have not recently heard the low volume, high pitch sounds for a few seconds with the Khartago.

No tubes are in my playback chain. 

I have opened up the Khartago to re-verify bias and offset which are correct.  Currently the line voltage is 109V and the bias is down to 16mv for this Kismet board (AC has ranged from 109V to 118V per recent measurements with a Kill A Watt meter.).  Seems like the bias varies as the line voltage changes.

What thermal interface material is used with the 2SA1216+2SC2922 transistors?  After about 10 years maybe it needs to be reapplied. 

The inner heat sinks measured 120F, then went down to 108F after the top case was open for a while.

[WarmColors]

As an update, there are still issues with the heat of the Kismet in Khartago.  The case is currently 20 degrees F above ambient temperature (measured on sides and top of case with an IR thermometer), still hot to the touch. 

Any advice would be welcome.  Does the thermal material touching the heat sink require periodic replacement?  Any other ideas?  The Odyssey audio sounds so good from that amp that I am loath to change anything!

I have not recently heard the low volume, high pitch sounds for a few seconds with the Khartago.

No tubes are in my playback chain. 

I have opened up the Khartago to re-verify bias and offset which are correct.  Currently the line voltage is 109V and the bias is down to 16mv for this Kismet board (AC has ranged from 109V to 118V per recent measurements with a Kill A Watt meter.).  Seems like the bias varies as the line voltage changes.

What thermal interface material is used with the 2SA1216+2SC2922 transistors?  After about 10 years maybe it needs to be reapplied. 

The inner heat sinks measured 120F, then went down to 108F after the top case was open for a while.

Any updates? I purchased the Stratos have not received it yet. I will need to keep an eye out on this on my amp if it were to get hot.

[disc4]

No updates yet on the Kismet in Khartago.

I installed the replacement PCB from Klaus and it seems to have an issue.

With no inputs connected but with speakers always connected to all 3 outputs, there is a low buzzing sound coming out of the left speaker channel.

With inputs connected to the left and right channel (testing with both a high end dac, then disconnecting the dac and trying with a battery powered audio device connected only to the stereo inputs of the HT3 and no other device), both channels emit a buzz audible from about two feet away. 

With inputs connected to the left and center channel, no buzz.  Same (no buzz) with the right and center channels.

I am well aware of ground loop causes and DC interference from other devices, but the HT-3 is connected to the same outlet as my Kismet in Khartago, which does not emit a buzz and has all the same speaker models and wiring.  I also connected it to another outlet with the same results. 

My original board in the HT-3 did not have this issue (no wiring or anything else has changed besides the replacement PCB).  So the problem seems to be isolated to the replacement stereo board.

I have made sure that the black ground wire is soldered to the new board; the separate black ground wire remains soldered to the center channel board.

[WarmColors]

No updates yet on the Kismet in Khartago.

I installed the replacement PCB from Klaus and it seems to have an issue.

With no inputs connected but with speakers always connected to all 3 outputs, there is a low buzzing sound coming out of the left speaker channel.

With inputs connected to the left and right channel (testing with both a high end dac, then disconnecting the dac and trying with a battery powered audio device connected only to the stereo inputs of the HT3 and no other device), both channels emit a buzz audible from about two feet away. 

With inputs connected to the left and center channel, no buzz.  Same (no buzz) with the right and center channels.

I am well aware of ground loop causes and DC interference from other devices, but the HT-3 is connected to the same outlet as my Kismet in Khartago, which does not emit a buzz and has all the same speaker models and wiring.  I also connected it to another outlet with the same results. 

My original board in the HT-3 did not have this issue (no wiring or anything else has changed besides the replacement PCB).  So the problem seems to be isolated to the replacement stereo board.

I have made sure that the black ground wire is soldered to the new board; the separate black ground wire remains soldered to the center channel board.

Have you been able to get ahold of klaus?

[Oystein]

I am a little late to join this "party" but I also see an increase of heatsink temperature during the hot summer days.

While the room temperature is normally around 20-21 Celcius but during a hot summer (outside up to 36 Celcius) the living room heats up to 27-28 degrees.
During these hot days I can touch the heatsink but barely for longer periods so I guess the heatsink will reach well over 50 Celcius.

I did hide the equipment (WAF) as can be seen on the pictures below. The plywood shelf has openings exactly onder the heatsinks so it helps the airflow.
But the whole wooden construction above acts like an umbrella keeping the heat there as the warm air is difficult to get rid of.

I am planning to widen the openings in the shelf and install 2x 80mm fans flush with the plywood for each heatsink and run these fans by a simple thermostat (ambient temperature)
Running 80mm fans at reduced speed should make them silent and still creates enough airflow to cool the heatsinks.

During the warm days I can really notice the increased bias current by increased bass (it has a positive temperature coefficient - the warmer it gets the higher the bias current).


My home setup:



The equipment visible when the lower beam is removed (Odysset Khartago stereo positioned 90 degrees CCW for better access to the terminals)





The shelf before it got installed:



Speaker cable installation:

[klaus@odyssey]

There seems to be some confusion about the bias / heat here....

- the Stratos usually runs about 5 - 10 degrees above room temperature,  the Khartago 10 - 20 degrees.
- the reason why we ask all of you guys to measure the house voltage is so that I can set up the amps for absolute 100 % performance....this means that I set up the bias at the upper range,  knowing that the amp doesn't get much above that envelope because I have the voltage measurements at hand...


- if I don't have the voltage info,  then I usually set it up at 10 % less bias at 120.5 V,  which seems to be the average in all of the thousands of measurements I received.   This ensures a safety range if the actual voltage would exceed that 120.5   However,  higher house voltage also means that the bias gets up....higher bias = more heat.... meaning that the actual bias in turn would get close to the maximum / optimum...however,  if the voltage drops well below the 120.5 V,  then the bias will also go down,  making the amp less "rich and emotional",  but will also result in stone cold operating temperatures........

However,  that 10 % less bias also means that the performance of the amp is not at 100 % optimum, but safe.


Of course only higher bias = higher heat is concern-able,  but the Sanken transistors take quite a  beating before quitting......rule of thumb here is that if you can't touch the top of the Khartago or the heatsinks of the Stratos,  then it needs rebiasing.....

Now,  as to Joe  / Disc4,  he did measure the bias,  and the amp is perfect....again,  temps will come down some in the winter,  and yes,  ventilation is of some concern with the Khartagos,  but a non-issue with the Stratos cases...


And nope,  our amps aren't special in this regard,  it's just that other companies don't tweak it out to the extreme as we do....and yes,  every amp has to be biased, of course...and yes,  bias changes the sound quality big time.

[WarmColors]

There seems to be some confusion about the bias / heat here....

- the Stratos usually runs about 5 - 10 degrees above room temperature,  the Khartago 10 - 20 degrees.
- the reason why we ask all of you guys to measure the house voltage is so that I can set up the amps for absolute 100 % performance....this means that I set up the bias at the upper range,  knowing that the amp doesn't get much above that envelope because I have the voltage measurements at hand...


- if I don't have the voltage info,  then I usually set it up at 10 % less bias at 120.5 V,  which seems to be the average in all of the thousands of measurements I received.   This ensures a safety range if the actual voltage would exceed that 120.5   However,  higher house voltage also means that the bias gets up....higher bias = more heat.... meaning that the actual bias in turn would get close to the maximum / optimum...however,  if the voltage drops well below the 120.5 V,  then the bias will also go down,  making the amp less "rich and emotional",  but will also result in stone cold operating temperatures........

However,  that 10 % less bias also means that the performance of the amp is not at 100 % optimum, but safe.


Of course only higher bias = higher heat is concern-able,  but the Sanken transistors take quite a  beating before quitting......rule of thumb here is that if you can't touch the top of the Khartago or the heatsinks of the Stratos,  then it needs rebiasing.....

Now,  as to Joe  / Disc4,  he did measure the bias,  and the amp is perfect....again,  temps will come down some in the winter,  and yes,  ventilation is of some concern with the Khartagos,  but a non-issue with the Stratos cases...


And nope,  our amps aren't special in this regard,  it's just that other companies don't tweak it out to the extreme as we do....and yes,  every amp has to be biased, of course...and yes,  bias changes the sound quality big time.

Klaus how backed up on orders are you? Is the wait time almost two months?

[disc4]

As an update the third PCB replacement is working perfectly so far with no buzzing - thanks to Klaus for his time and help throughout the process!

On the subject of the heat issue:  through some extensive testing it seems that one of the two Plitron transformers in the Stratos HT-3 seems to be in need of replacement. 

With that transformer disconnected from the center channel board (and just the new stereo board plugged into the other transformer), the amp is cool to the touch, but I heard buzzing and would measure high temperatures whenever the "not good" transformer was plugged in.  The center board worked well on its own while the stereo board was with Klaus, with no buzz or other issues while connected to the "good" transformer. 

There was also buzzing in the speakers with the "not good" transformer plugged into the new stereo board, but no buzzing with the other transformer connected to the new stereo board and the center board disconnected. 

[klaus@odyssey]

Clarifications here:

-  Yes,  of course I tried to help out,  even going so far in sending several boards,  with the last one actually taking a $ hit....but had to be done,  it's just the right thing to do

- I've never had the amp here to check it myself...not easy...

- This was a used amp,  and somebody somehow seemed to have "worked "  on it....

-  And yup,  transformer...these are the original Plitrons.  Talk about reliable.  Really weird that one acts up,  but then again,  I have a replacement for Joey.........

[disc4]

Good news, the replacement transformer worked and now my HT-3 issues appear to be resolved!  I will post an update if there are any further notes.

So in summary the excessive heat and buzzing in the Stratos HT-3 appear to have been a product of a failing PCB and transformer.  Replacing those two components seems to have fixed these issues.

Thanks again to Klaus for his help!

[disc4]

Two year update / importance of seasonal household voltage changes affecting the biasing:

As an update my Odyssey equipment has worked well over the past two years.  Thanks again to Klaus for his attentive support.

An important note - without a power conditioner, it may be beneficial to rebias your amp between winter and summer seasons if your utility company has big swings in voltage levels between seasons and you want to maximize sound quality.  In my area the power moves from the high 100s (in the summer when everyone has their air conditioning on) to ~120v in the winter.

Recently I noticed that my setup with an Odyssey Kismet in Khartago case amp had lost some of its sound quality.  The sound in the frequency area of 1 khz became bloated by about 3-4db (per my testing with equalization on music I am familiar with) and the rest of the frequencies during music playback seemed off, most noticeably for male vocals.

I checked my amp and the bias and offsets were both off significantly, presumably due to my last setting the amp in the summer two years ago (if one had to pick only one biasing time, maybe bias only in the winter?).  Klaus specified 19.5 to 20mv for Kismet boards and my amp registered about 25mv and an offset value not close to 0mv (maybe it was 5mv, don't remember).  I then updated the bias and offset to the correct numbers but the sound still wasn't right. 

I waited a day and the bias and offset numbers had drifted, so I did the bias and offset again and now everything is back to the great sound quality of before.  So the biasing is definitely not something that should be done over one day only and the results may take 24 hours (or more?) for audible sound quality improvements.

I am glad that everything is up and running.  I was worried a cap replacement was needed (the Kismet in Khartago amp was made in early 2014).  I inspected the caps and there are no outward signs of wear, though I have not tested them with an ESR or in any other way. 

Klaus has noted on another thread that "power supply caps are electrolytic.  They simply dry out over a period of time,  and while they survive for longer than that,  they do exhibit audible degradation because of that,  and yes,  I do recommend replacing any ps electrolytic caps after 7-10 years" - I wonder how one would describe the audible changes in a dried out capacitor that still functions, so one can know when to replace these caps in an Odyssey amp.

Is rebiasing recommended every number of months or every year?  Would there be drift in an amp even if the line voltage remained constant?  Maybe a power conditioner or UPS, to keep a more consistent 120v, would be beneficial, unless these degrade the sound quality more than the change in line voltage?

***12/16 update - unfortunately the Khartago did not keep its bias setting.  After being stable for a couple hours and performing well, today the amp was back up above the 20mv recommendation; it was at 31mv and this is having been powered on without playing any sound since the previous day and with a small fan pointed at the unit overnight.  Also I noticed that the bias changes significantly when I turned on a fan above the unit, moving down 5mv or more within a minute.  The following day 12/17 the bias moved up less, to 22.5mv, and 12/19, the bias was around 26mv each side.

I wonder if these symptoms usually mean the 10 power supply caps need replacement?