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Old 31st October 2006, 12:23 PM   #1
Bonsai is offline Bonsai  Taiwan
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Default Ovation Amp

Here are some pictures of my amp (which I have called the 'Ovation 250'). Its a fully complementary design and this week end I finaaly got it running and driving my B&W703's. I spent 18 months designing it and prototyping over the last 3 or 4 years in between doing an MBA and moving to Japan recently. Final product you see here uses DSTHP PCB's. +-75 volt rails, 2.5KVA transformer and 100mFD of smoothing. I got the case from Fischer Elektronic (not impressed - it is a bit crude - I will send them some feedback) and still have to get a final front panel made. Uses 5 pairs MJL21193/94 per channel.

I fired it up and just used my iPod to try it out. Sounded very good to my ears (but I am biased) and compared to my Marantz PM68.

There is still a bit of refinement to do to - e.g. correct errors on the control board (this is uController based and does in-rush current limiting, thermal protection, DC offset, clipping indicator, output relay control), and a small mod I want to make to the VAS stage. The power supply will also be cleaned up. I expect these things to take another 3-6 months - I'm pretty busy at the minute.

I learnt a lot from this project about audio power amps - my background is in industrial electronics - linear systems design (TC amps, A-D, SMPS etc).

I have circuits in an Excel spread sheet but they are >100kb - I'll post them if someone tells me how to get them onto the forum.
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Old 31st October 2006, 12:24 PM   #2
Bonsai is offline Bonsai  Taiwan
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Default Ovation Amp

Picture 2
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Old 31st October 2006, 12:27 PM   #3
Bonsai is offline Bonsai  Taiwan
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Default Ovation Amp

Picture 3
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Old 31st October 2006, 12:28 PM   #4
Bonsai is offline Bonsai  Taiwan
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Default Ovation Amp

Picture 4.

I forgot to add - it weighs 70 pounds.
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Old 31st October 2006, 12:38 PM   #5
mikeks is offline mikeks  United Kingdom
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Default Re: Ovation Amp

Quote:
Originally posted by Bonsai

I have circuits in an Excel spread sheet but they are >100kb - I'll post them if someone tells me how to get them onto the forum.
Upload here, and post link.
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Old 31st October 2006, 12:39 PM   #6
Bonsai is offline Bonsai  Taiwan
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Default Ovation Amp

Picure 5 - backside view. I used 2 sets of spkr terminals per channel.
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Old 31st October 2006, 12:42 PM   #7
Bonsai is offline Bonsai  Taiwan
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Default Ovation Amp

Picture 6. Output Inductor a bit OTT, but I'll sort that out in the next week or so.
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Old 31st October 2006, 01:17 PM   #8
Bonsai is offline Bonsai  Taiwan
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Default Ovation Amp

Circuits

Front end and VAS
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Old 31st October 2006, 01:22 PM   #9
Bonsai is offline Bonsai  Taiwan
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Default Ovation Amp

Here is the output stage.

note that changes have been made to the SOA protection circuit (value changes to the resistor networks to bases of Q206 and Q200). Emitter ballast resistors are now 0.22 Ohms.
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Old 31st October 2006, 01:25 PM   #10
Bonsai is offline Bonsai  Taiwan
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Default Ovation Amp

Attached this time
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