2stageEF high performance class AB power amp / 200W8R / 400W4R

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jwilhelm

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Joined 2014
vzaudio.com/
HYPERTUNE said:
Tested the M3 form tap in a piece of 10mm thick 6061 flat bar.

Set the speed to max and the clutch to min. Tapping went well, with the tap bottoming in the hole and the clutch slipping without tool breakage. Backed out full speed no problems. 10mm through hole no problem either. For lubricant I used "Tap Magic" but I'd say any lubricant would be fine.

The first few holes were drilled freehand, the last 2 (on the left) were done in a drill press. As you can see, the ones using the drill press gave a much better result. Due to the fact that the drill size is only .2mm smaller than the tap, any amount of wondering with the drill leaves you with no material to form the thread.

Bottom line: As long as you use a drill press for the holes and have an adjustable clutch, the form tap is very successful using a cordless drill.

I'm sending a "Care Package" to Toni with M3,4,5 taps and suitable drills.

PS: Note the made in Austria welder in the background ;)
Click to expand...

It's nice to see someone else figured out how to use a tap! Yes the drilling process is very important for the tapping process. I do mine in a milling machine. I have yet to find good quality thread rolling taps in my area though.
 
astx

astx

Member
Joined 2011
Paid Member
diyralf said:
You are using 11.9mA current. Isn't it to high? D.Self prefers 6mA.
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For SA2014 I use even higher VAS current: ~ 17mA. 2 stage EF OPS need more current from VAS in comparison to 3 stage EF OPS.
Don't know if this is "too high". My total LTP current is also very high - 6mA.
This allows me to use bigger compensation capacitors (easier to get) and reduce dependency of stray capacitance's.

BR, Toni
 
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A

AndrewT

R.I.P.
Joined 2004
thimios said:
What is the max.power supply voltage for SA 2014?
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Depends on speaker loading.
Assuming a 3pair output stage:
I'd suggest dual 35Vac for 4ohms. Dual 40Vac for 6ohms and dual 45Vac for 8ohms.
If you're using very high SOA transistors, then you may find you can increase the transformer voltage by one step:
dual 40Vac for 4ohms, dual 45Vac for 6ohms and dual 50Vac for 8ohms, with 4302/4281 and with very good cooling.
 
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astx

astx

Member
Joined 2011
Paid Member
No. The +/- 60V are from my 2 regulated PS maximum setting (per PS 2x30V in serial configuration).
If you use the described 650VA transformer and the big SA2014 PS pcb the rails are sagging to 62 - 65V if you play 220W continous. One monoblock PS uses 8 x 10000uf/100V lytics.
 
diyralf

diyralf

Member
Joined 2016
Hello Toni. I always find good suggestions in your post. What did you pay for the TAUSCHER-transformer? I suppose that was 1 piece? Is there a hum to hear? Since it is shed, is there any smell? Presumably it will not have primary / secondary shielding.
 
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astx

astx

Member
Joined 2011
Paid Member
I've ordered 6 pieces 600 VA custom made. Total cost incl. shipping was about 850 EUR. But you get them only B2B. Quality is very good. Mechanical hum only, if DC on AC line is present. No smell. Shielding can be ordered if wanted.
If you want B2C custom made transformery you can try toroidy.pl for example.

BR, Toni
 
astx

astx

Member
Joined 2011
Paid Member
I have other experience: my custom made transformers in a stainless steel pot housing from toroidy.pl look very professional at a reasonable price. Maybe another company is able to deliver the same custom made transformers at a lower price. But we can discuss this in an extra thread where you can summarize all B2C toroid manufacturers.

BR, Toni
 
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