What’s On the Bench Tonight (OBT)

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WOBT - June 12, 2021: Well not exactly a bench, but this is what’s on my desk. CAD production drawings for a new product that needs review - a hybrid tube/SS headphone amp I have developed with Jhofland in collaboration with Living Sounds Audio. It’s going to be quite a head turner I think. The HyperDrive-2 will have 3 selectable inputs, a preamp output, a tube buffer stage, fully protected outputs and anti thump logic control via a microcontroller for graceful power up and shutdown. It will drive 2w into 32ohms and make clean, engaging and transparent sound, and will come encased in a beautiful custom thick, aluminum powder coated chassis. This is a preliminary render - a few cosmetic details still need to be worked out (upside down volume dial):
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Agree, nice work Anand ;)

I had a bit of time myself to sling a little solder Sunday afternoon on my bench. This is the LuFo amplifier verification build. Once I receive the IMS adapter’s loaded with LU1014D’s I can proceed.
 

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WOBT - June 11, 2021: The LuFo PCBs are here! I’m going to start populating them. These boards are impressively huge. JPS64 did superb job. We have a few silkscreen errors but that’s the point of verification builds. We work out all the bugs before releasing proven-to-work designs for all to enjoy.


Did I mention that I ordered these monoblock chassis? Will be 3 weeks or so before they get here.

Hi

Any link to these monoblock chassis?

cheers
 
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That’s a neat project Nigel, a scope is an essential tool in DIY and amazing to see that you can make one from scratch using an ADC and a Pic MCU!


Thanks, Peppenino for the link to the dual monoblock chassis. It’s a beast! I was thinking since it has two dual 5Ux350mm deep heatsinks each, one could make a balanced LuFo amp - the SuSyLu, which can make up to 100w of SE Class A power with only 28v single rail. Predicted distortion at 1W has gone done from 0.01% to 0.0007% in this configuration.
 
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Studying this schematic some more on the desk / computer sim tonight. The transformer is center tapped so if the DC bias current flows from two legs to the center tap, the field cancels and you don't have to worry about saturation. Having the ability to generate 80Vpp from a single 28vdc rail still intrigues me - it just seems fantastical, but that is the property of stored magnetic energy in a transformer.
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The Blue trace is the postive phase leg, the Red trace is the negative phase leg, and the Green is the difference applied at the balanced drive output to the speaker. We can see that there is 80Vpp into 8ohms (100w rms) from a 28Vdc single rail PSU.
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Time flies – halfway to next Xmas and only now Dibya's TDA7293 Xmas amp is on my bench. But great to be slinging some solder again. I was looking forward to winding my own inductors, but in the end it was frustrating. But not as frustrating as the mixed up BOM from my local supplier who managed to send some wrong components – substitutes for out-of-stock stuff. Had to re-order some caps. So, this amp will be on the bench for some time until I have all the components.

After all this trouble I sincerely hope this amp (with a gazillion more parts) will sound better and de-throne my trusted $2 TDA7297 amp who has been giving great service for the last 4 years.
 

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Hi Twocents,
Nice work on your Xmas amp build! The inductor looks great! If you are asking if this Xmas amp will beat the Lunch money amp, I have no doubt you will be very happy with the result. It’s a superb amplifier. One of the best chip amps I have heard. The sound is very neutral yet engaging, with nice bass impact. I have been using it for past 5 days and really enjoying it. I am driving it with a new solid state buffer hybrid preamp with a tube interstage buffer. Basically a BTSB with an ECC88 SET buffer. Complete with SSR muting and anti-pop features.
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