Progressing - Low Power Desktop Amp
Posted 19th April 2013 at 09:49 AM by BuildMeSomething
Updated 25th April 2013 at 08:36 AM by BuildMeSomething
Updated 25th April 2013 at 08:36 AM by BuildMeSomething
Holiday: Bad weather to a point it was near impossible to take a steady photograph due to the gusting winds. Hiding from the winds meant poor vantage points, very much non-idealistic for photographing landscapes.
Digi-key: The order turned up on the Monday morning, roughly 10 minutes before leaving. The PSU boards must have arrived mid week, a neighbour had those...
The parts order was enough components for one power supply and one amp. The PSU is assembled but untested as yet. The toroidal and 10K Alps RK27 are to be ordered from RS Components later today.
PCB issues: C1-C6... this is where trusting the people who generate default libraries for FreePCB falls down and my inexperience shows. Lead diameter on the caps is 28MIL, default part through-hole diameter is 28MIL... Each lead needed a quick file to reduce its width enough to fit the board. No other issues to report.
I don't think I could have made the overall size of the board smaller without making it more difficult to assemble. Part placement works well, any layout changes would result in slightly shorter traces to ground for one or two parts [1-2mm].
Now waiting on the Amp boards to be fabricated and sent out...
Update [13-04-20]: Toroidal & Alps pot are on their way, hopefully arriving Monday morning. Was growing a little impatient to see if the power supply works. For first power-up, it was hooked to a 2x18V 15VA toroidal. All good news, works fine, no blown or overheating components. Step one complete... Possible issue with the heatsinks not being capable of dissipating enough heat generated by peak currents under full load conditions without becoming extremely toasty... should be OK under a constant current draw based on AmpsRMS from both channels.
Had a look at chassis for this and have my eye on a couple from an e-bay supplier who has been used before. Once everything is known to be working OK, the chassis will be ordered...
Also looking at speakers to go with this. So far Tannoy's 601P studio monitors are favourite. However, there is a strong desire of making a speaker using the Fostex FF125WK full range driver. UK based Wilmslow Audio do the driver and Fostex designed BR cabinets in flat pack form, at a similar price to the Tannoy...
Been playing quickly with TrueRTA, but need a [calibrated] mic & usb interface to use it correctly for room analyses. Currently use Foobar 2K & ODAC for playback of WAV files ripped direct from my CD's. Just installed a VST Wrapper and EasyQ for room EQ duties...
Update [13-04-22]: Fortuitously, the toroid and volume pot arrived just as I opened the front door to leave for work. The toroid has now been arc welded to the PSU's AC inputs... dam, those wires are thick! The chosen chassis' internal measurements are 200mm(W) x 300mm(D) x 86mm(H). It'll all be a nice fit with a little room around each section. Plus, as my metalwork skills are some what lacking, Front Panel Designer has come in very handy for creating a custom heatsink for the amp's PCB. I might go with the more expensive fancy design, light the inside of the case and get a clear acrylic top for the chassis... But first I need the amp PCB's, which are on their way. Furthermore, it needs to be built and tested, both which will be done before ordering the chassis and heatsink.
Update [13-04-24]: Just waiting on things to arrive. Thought it'd be good to make some cheap speakers to help test the amp once its up and running. Liked the idea of a quick and easy build using foam board. Two £3 8 Ohm 3" FR no-name drivers are on their way courtesy of e-bay, plus a ten pack of A3 sized foam board from Amazon (£8). With glue, speaker wire and terminals, it shouldn't cost more than £25... Cabinet will be based on the micro Fonken, designed for the FF85WK FR driver.
Digi-key: The order turned up on the Monday morning, roughly 10 minutes before leaving. The PSU boards must have arrived mid week, a neighbour had those...
The parts order was enough components for one power supply and one amp. The PSU is assembled but untested as yet. The toroidal and 10K Alps RK27 are to be ordered from RS Components later today.
PCB issues: C1-C6... this is where trusting the people who generate default libraries for FreePCB falls down and my inexperience shows. Lead diameter on the caps is 28MIL, default part through-hole diameter is 28MIL... Each lead needed a quick file to reduce its width enough to fit the board. No other issues to report.
I don't think I could have made the overall size of the board smaller without making it more difficult to assemble. Part placement works well, any layout changes would result in slightly shorter traces to ground for one or two parts [1-2mm].
Now waiting on the Amp boards to be fabricated and sent out...
Update [13-04-20]: Toroidal & Alps pot are on their way, hopefully arriving Monday morning. Was growing a little impatient to see if the power supply works. For first power-up, it was hooked to a 2x18V 15VA toroidal. All good news, works fine, no blown or overheating components. Step one complete... Possible issue with the heatsinks not being capable of dissipating enough heat generated by peak currents under full load conditions without becoming extremely toasty... should be OK under a constant current draw based on AmpsRMS from both channels.
Had a look at chassis for this and have my eye on a couple from an e-bay supplier who has been used before. Once everything is known to be working OK, the chassis will be ordered...
Also looking at speakers to go with this. So far Tannoy's 601P studio monitors are favourite. However, there is a strong desire of making a speaker using the Fostex FF125WK full range driver. UK based Wilmslow Audio do the driver and Fostex designed BR cabinets in flat pack form, at a similar price to the Tannoy...
Been playing quickly with TrueRTA, but need a [calibrated] mic & usb interface to use it correctly for room analyses. Currently use Foobar 2K & ODAC for playback of WAV files ripped direct from my CD's. Just installed a VST Wrapper and EasyQ for room EQ duties...
Update [13-04-22]: Fortuitously, the toroid and volume pot arrived just as I opened the front door to leave for work. The toroid has now been arc welded to the PSU's AC inputs... dam, those wires are thick! The chosen chassis' internal measurements are 200mm(W) x 300mm(D) x 86mm(H). It'll all be a nice fit with a little room around each section. Plus, as my metalwork skills are some what lacking, Front Panel Designer has come in very handy for creating a custom heatsink for the amp's PCB. I might go with the more expensive fancy design, light the inside of the case and get a clear acrylic top for the chassis... But first I need the amp PCB's, which are on their way. Furthermore, it needs to be built and tested, both which will be done before ordering the chassis and heatsink.
Update [13-04-24]: Just waiting on things to arrive. Thought it'd be good to make some cheap speakers to help test the amp once its up and running. Liked the idea of a quick and easy build using foam board. Two £3 8 Ohm 3" FR no-name drivers are on their way courtesy of e-bay, plus a ten pack of A3 sized foam board from Amazon (£8). With glue, speaker wire and terminals, it shouldn't cost more than £25... Cabinet will be based on the micro Fonken, designed for the FF85WK FR driver.
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