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dadod 25th July 2012 07:44 PM

TT amp, 200W/8ohm, 701W/2ohm
4 Attachment(s)
Here is my attempt to construct more powerful amp:
200W on 8ohm load
375W on 4ohm load
701W on 2ohm load
This amps is combination of ThermalTrak and standard ONSEMI power transistors. OPS is a Triple containing two TT pairs and two standard power transistors of the same family. As the power supply is of the same importance (maybe even more) as the amp itself I used Capacitance multiplier situated close to the OPS and the input stage. Input stage and OPS could be powered from different main power supply or from the same one. To facilitate use of the Baker clam input stage capacitance multiplier has 4 to 5V higher output then the OPSís capacitance multiplier. As a bonus OPSís capacitance multiplier contains a loudspeaker protection circuitry.
Those are simulated results:
ULGF = 1.3MHz
RL = 4ohm, Pout=320W
THD1k = 2ppb
THD20k = 0.96ppm (0.90ppm, RL = 8ohm)
THD50k = 13.42ppm
THD100k = 0.014%
RL = 4k, THD20k = 0.81ppm
PM = 61 degree
GM = 15dB

The main goal is to have very short connection between OPS and dedicated power supply. The amp circuitry is quite close to may previous TT amp, and that one plays music for some moths with no problem at all and nicely too.

dadod 25th July 2012 07:48 PM

2 Attachment(s)
Here is OPSís C multiplier with the loudspeaker protection. On the main amp schematic OPSís C multiplier was simplified with no loudspeaker protection shown.
No PCB design was not atempted yet.

dadod 25th July 2012 07:51 PM

No PCB design was atempted yet, sorry for my bad English.

MagicBox 25th July 2012 07:52 PM

Cool to see more people go to greath lengths and detail to create their own pet amp. Good numbers too! Almost sounds like you had a peek at the Power Supply Reservoir Size thread too ;)

Are you close to actual prototype creation or you still have to make the real schematic? (I don't regard simulation schematics the real schematic, so much is omitted ususally)

Edit: Your capacitance multipliers look very interesting; mind you if I would try to incorporate it in my design and see what results it yields?

dadod 25th July 2012 08:00 PM

Nothing is omitted here(except main power supply with big caps, similar as I used in my other TT thread) and my actual firs TT amp is very close to the simulation stability wise, distortion was not measured as I donít have the tool yet(planning to use PC and good sound card but always something else is more important).

MagicBox 25th July 2012 08:18 PM

Nice, in my schematic there are some parts omitted, most notably decoupling / reservoir caps onboard. When it comes to distortion measurements I was in the same boat as you. I did some research into audio analyzer software and one remarkable piece came out of it: Virtins' Multi-Instrument.

It's not free, it does its job very well (including soundcard calibration and native distortion cancelling) and yields pretty accurate results when used with a decent soundcard. I used the ASIO4ALL driver as the soundcard interface for the tool. I used it to measure MF80, my 80-watts 4Ohm amp, yielding a 10K THD of around 0.00017%. Don't mind the increasing distortion the lower the frequency, the amp has now a big enough feedback cap ;)

Note: When I tried MI, it was rather buggy, so that may be prohibitive to actually buying it for the price ($100 back then)

dadod 25th July 2012 08:27 PM

Look here too, its well reviewed audio software.

dadod 25th July 2012 08:31 PM

Sorry, here ARTA Home

MagicBox 25th July 2012 08:42 PM

Thanks, I'll check it out this weekend I think. I still have the probe attached to MF80 so it'll be quick to hook it up again to the soundcard and see what results I get and will post back when I have some.

dadod 26th July 2012 05:30 AM

1 Attachment(s)
Here is OPS's capacitance multiplier power simulation for one MJL4281 transistor at 4 ohm load.
It uses triple EF configuration to complement the same of the OPS.

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