AudioCircle
Industry Circles => Odyssey Audio => Topic started by: KeithGB on 23 Jul 2017, 12:53 am
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Greetings all,
Can anyone tell me where I could get a copy of the bias intructions for the Stratos stereo amp?
Thanks in advance,
Greg
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Have you tried contacting Odyssey?
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Instructions PM sent KeithGB. Same for both Mono and Stereo because it the same board and the same process.
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Can I get a pm on the instructions as well ,(germay0653)
Thank you in advance, Burt...
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Have you tried contacting Odyssey?
I did. Klaus was unavailable. Thanks.
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Instructions PM sent KeithGB. Same for both Mono and Stereo because it the same board and the same process.
Got it!
Thanks so much, Germay.
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PM sent Delta77!
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Thanks Germay
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Thanks Germay
could you be kind enough to send me the Bias instructions also for future use , I already sent you a PM
thank you.
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PM sent A_shah!
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@germay0653
thank you
A_shah
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Hello,
I purchased a used stereo Stratos amplifier and would like to check the bias setting.
I was searching for this procedure and came across this thread. Germay0653, could you send me the proper biasing information also? I would really appreciate the info.
I believe my Stratos is an older version it has the green pcb, Sanyo NP caps, Goguen transformer and 4 Odyssey 15000uf caps off board.
Thanks.
Vinny
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Does anyone have the Stratos amplifier bias procedure they could send me??
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I'm sure this is a little past due, but it sure would be nice if Klaus whipped up a very professional looking guide for mono and stereo amps biasing. It seems enough people are comfortable with doing their own amps just need a little direction on where to do what
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+1
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I recommend placing a real phone call to Klaus about the bias procedure, emails are hit or miss. After speaking with him about my antique Stratos Stereo amp, I've decided to refurbish it myself.
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There is no difference in the procedure for mono vs stereo. Mono is both channels bridged so both need to be adjusted the same as you would for stereo.
Instructions for biasing
The amplifier should be at operating temperature. If you've been playing music, wait perhaps 10-15 minutes for everything to "settle down".
The board is basically two channels, bridged into a monophonic amp, and essentially there are two "sides" to the board corresponding to the left and right channels in the stereo versions.
First check the output offset, which is the voltage between pads 6 (+) and 5 (-). The (+) wire going to the speaker cable terminal on the back of the amp is on pad 6. Set the DVM to 200 mV DC, put the positive lead of a DVM onto 6, negative lead onto 5, and adjust the trim pot way at the opposite end of the board (not the one in the middle) to zero out the offset. Don’t worry about small offsets, say 1 mV or less.
Repeat for the other channel, with the negative lead on pad 5, positive on 7.
Now, go back to the other side, negative lead on pad 5 or other convenient signal ground, and check TP 5 and 6 to see which one has the highest value (they will be slightly different). This time, use the trim pot in close to TP 6 to set the bias, using the TP point that had the higher voltage, to be about -21 mV. Repeat on the other side, checking TP 1 and 2, and use the trim pot near TP 2. Be careful not to short anything to the power transistor case which I think is grounded.
Then check the offset values again as they may have changed slightly, recheck the bias, etc.
The bias controls the "voicing" of the amp. -18 will be colder, -24 mV will be warmer. Klaus recommends -21 mV as a starting point.
Per Klaus himself:
Make sure that you have the red probe on the speaker out, and only use that part of the board for biasing, as the board is true mirror image...then move the probe into the other post and bias that part of the board...for offset, probe - goes to opening 7 or 8 (ground of the unused speaker outs on the board)...offset pots are the 2 close to the face plate, get the offset close to 0 mV....then for the actual bias go only into TP's 3, 4, 7, and 8...ignore the others, and use the one on each side with the higher value....pots are next to the transistors.......20 mV's....again, PLEASE make sure that you move the red probe from side to side, as the 2 sides of the board right through the middle act independently !!!!!!!!!!!!!!
walk away from it, come back after 10 minutes, check, and repeat if necessary until it is stabile........
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Sorry it took so long but we had to prepare our house for sale, it sold in 1 day and then had to move out all within a three week period. If your familiar with a DMM and the topology of the board it can easily be done. If you unsure, just send the amp to Klaus as he provides that service for his owners.