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
taccodude,
Good to hear that the amp is up and running. Keep us posted on the progress. Any pics? 🙂
Good to hear that the amp is up and running. Keep us posted on the progress. Any pics? 🙂
Strange P/S capacitor setup - it looks like a CCCRC with Siemens caps. Any benefits of doing this?
Duh! I'm looking at this backwards, with the hidden transformer at the 'front', so it's CRCCC, yes?
After listening to USSA5 for a couple Days now ,I can say it is a really good Amp.Clean.lot of Resolution,deep Bass Resolution too.The only Thing I`m missing is some Body for Piano,Voice...Can this be bettered by choosing other Input Cap or Resistors in some Places? Any Advice?
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.
I ran mine without input cap, I get to hear more details and clarity.
As my preamp already has a d.c. blocking cap at the output. Will tune them to 1.25A bias soon. Still burning in.... as of now it still my favourite power amp.
As my preamp already has a d.c. blocking cap at the output. Will tune them to 1.25A bias soon. Still burning in.... as of now it still my favourite power amp.
If P3 and P4 are not adjusted right ,would it degrade the Sound? How can I control that in the finished Amp ?
ggetzoff, I let the Amp run 12Hours a Day,for 5 Days now,I think it won`t change that much any more.
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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DC Offset is very good and stable,I just wondered if that can be tested, with all Parts installed because I didn`t mount them.I just wonder if something is wrong because it is pretty cool,my F5 was a lot warmer.
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)
In Post 703 You can see everything,including Temperatur.Checked it today and is still the same.
37C is very low as a class A heatsink temperature. Is it really taken at hottest point of heat sink?
Fab
Fab
Yeah, definitely... I would run it between 45C and 50C (closer to 50C). If you have a good heatsink and room temperature permits it, you can safely push it just under 55C. I'm running mine at around 50C at 1.3A bias.
Do
Do
In the Back of Heatsink is a little Hole where I measure.So I can do what,just push it to 70-75mV and watch Temperatur ?
Regards DT
Regards DT
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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