no need for extreme power 150w at 8ohm or close.
This old torodial has some history so i can not scrap it and i need to do something with it other than scrap.
I am torn between cheap class-d irs2092 or SS amp.
This old torodial has some history so i can not scrap it and i need to do something with it other than scrap.
I am torn between cheap class-d irs2092 or SS amp.
2x55Vac transformer would give you around 250W at 8ohm. A singel 500VA is a little bit small for a 2 ch amp. But it will work. Slewmaster 5pr output. or a SA2014 would fit the bill.
During quarantine, I had enough time to rewind a toroid from 2x30V to 4x15V for a small dual mono amp. Not as difficult as it might sounds.
so 77 v peak, 75 v after rectification.
I'm using a 520 va single winding 72 v transformer to power 2 channels of AX6. Single 3300 uf rail cap gets me 70 w average for 5 seconds on both channels. 8 ohm speakers.
I regulate down from 72 v to 69 with 5 parallel TIP142 driven by a 72 v stack of zeners. .33 ohm emitter resistors to share the current. Pentium II heatsink on the regulator.
So put your windings in parallel, regulate down to 69, provide plenty of heatsink for your single pair MJ15003 output transistors. Or if you are a techno/disco/house fan with low crest factor, put dual output transistor pairs. MJE15028/29 drivers will handle 2 pairs. I use MJE15028 equivalent for VAS too - all drivers & vas with heat sinks. I've got OT's remote from driver board on their own heatsink.
Retro Amp 50W Single Supply - Page 22 - diyAudio
The Class D board I bought from parts express wanted 19-24 vdc for power supply. Have none of those with more than 1 amp output, boards are orphans.
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Here to find: 2stageEF high performance class AB power amp / 200W8R / 400W4R
The output voltage is higher as recommended but if you drive the amp only with 8R load the transformer will deliver the needed power for a 200 - 250W peak @ 8R.
Don't forget the higher power dissipation also in Input/VAS stage - you need bigger/longer SK75 and SK76 heatsinks.
BR, Toni
Using a beefy driver transistor for the VAS has all sorts of issue - firstly the collector-base capacitance is huge (not even on the datasheet) and very non-linear, adding distortion and reducing bandwidth, secondly the Early effect is likely quite large, adding distortion again.
The requirements for a nice well-behaved VAS is high gain, high bandwidth, small Early effect (ie very high Early voltage), and very low Cbc (so the Miller compensation cap can dominate and be linear). A VAS transistor with more than 100mA current rating is immediately a suspect choice.
Checkout the KSA1381E/KSC3503E devices, 300V, TO126 package, 150MHz GBP, 2--3pF or so output capacitance. The E and F gain bins are the one's to go for.
Hey Mark an FYI, current production of ksc3503/ksa1381 do not have the same hfe bin types available. Only one bin for each, D & E. We have been using them for our VAS and buffers for the DH-220C design. The distortion numbers are near immeasurable, so in theory hfe matching makes sense but in reality it does not seem to matter unless maybe you use no feedback. I have some old Sanyo 2sc/2sa with the same E grouping, to try out to see if I can measure any differences, but I doubt it, don’t think I can measure low enough with my current test gear.
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No offense or disregarding on the suggestions above intended, just another idea: The Honeybadger would also do, just buy the beefiest output devices (MJL4281A/4302A or MJL3281A/1302A, afaik).
Best regards!
Best regards!
The sky is falling! Wear a concrete hat!
I'm using GE D44R2 TO220 VAS and MJE15028/29 drivers, and AX6 doesn't sound bad. Other than a little more hum my AX6 sounds just like my CS800s which quotes .003% HD. That's on SP2-XT speakers, with a 14 khz limit ears. All those transistors are Ft 30 mhz. TIP41c/42c lacked highs.
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