After adjusting USSA 5,let it cook for 3Hours ,while keeping an Eye on it every half Hour.It didn`t move much .After realizing that Temperatur didn`t get very high,I went for 65mV with a Temperatur of ca 38C°.Today let it cook again for 3 Hours and readjusted Offset on one Side,just a little.Hooked it up to Stereo right now and had a short listen.Very promising.Dead Quiet,very Detailed,seperatet from Speaker,not shure about Bass at the Moment.Let it Burn.
regards DT
regards DT
Patience....patience, let it break in. USSA-5 is generally a warmish, full-bodied and detailed amp; it does it all.
Taccodude
The current must be equal for positive and negative part of the input stage circuit. P3 and P4 setting must be verified and properly adjusted as per section 8.7 of manual. Doing so if it was not rightly adjusted will impact dc offset and bias thus rerun section 9 of manual. In the worst case you may have to rerun section 8.18 if the calculated resistor values significantly change with different voltage applied following P3 or P4 setting change.
But you can simply start by measuring voltage of section 8.7 for now and report your values here.
Fab
The current must be equal for positive and negative part of the input stage circuit. P3 and P4 setting must be verified and properly adjusted as per section 8.7 of manual. Doing so if it was not rightly adjusted will impact dc offset and bias thus rerun section 9 of manual. In the worst case you may have to rerun section 8.18 if the calculated resistor values significantly change with different voltage applied following P3 or P4 setting change.
But you can simply start by measuring voltage of section 8.7 for now and report your values here.
Fab
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Yes it can be tested with all parts mounted. Heat is coming from output mosfet and set by output bias current. Output bias current is set by P1 and P2. Heatsink should not be cool. You need more than 1.2A of output bias current and higher is better. I target about close to about 50C heatsink for a class A amp. You should adjust for at least same temperature as your F5.
Fab
Fab
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taccodude,
What is your bias set at? How much offset? More importantly have you check the bias after many heat cycles and warmed up?
I've had amps projects where the bias drops very low, in those cases an overly "cool" sound is what you get. No warmth whatsoever.
Cheers,
Enchilada guy (aka ggetzoff)
75mV would be 1.5A bias. No issues as long as your heatsink can support it. Start with 1.3A and then if too low, bring it to 1.4A and see what it gives you for sound each time. You will find the right balance for sure. Class A amps love heat.
Thanks
Do