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Bryston 4B SST clone
Bryston 4B SST clone
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Old 6th June 2019, 04:13 PM   #21
Aatto is offline Aatto  United States
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Bryston 4B SST clone
thanks, chalky for your well detailed progress report, i bought the same boards and am buying components little by little. will keep following up on this thread
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Old 17th June 2019, 07:45 PM   #22
chalky is online now chalky
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More progress. I've attached a photo of my nearly completed power supply and protection board. I'm going to fix heatsinks to the bridge rectifiers, and make up a couple of solid state relay pcbs to replace the loudspeaker protection relays. I'll make them with the same footprint and connections as the mechanical relays so that they are a drop in replacement on the main pcb. Initially I'll make them up on small pieces of perfboard and then later on I'll do proper pcbs.
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Old 25th June 2019, 07:52 PM   #23
chalky is online now chalky
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Got perfboard prototype of the solid state relay for loudspeaker protection finished today. It uses an Avago ASSR-V621-302E photovoltaic opto coupler together with a pair of FDP083N15A mosfets ( 150 V, 117 A, 8.3 mΩ ) in the "standard" circuit found all over this forum. The ASSR-V621 leds are connected in series and the photovoltaic outputs in parallel. I use a 680R series resistor to give a led current of 15mA. The polarity of the coil connections to the relays is immaterial for mechanical types but it matters for the solid state version. Unfortunately the designer of the main power supply/protection pcb has not been consistent in his choice of coil polarity connections and so two versions of the solid state relay are required - each with a different polarity for the "coil" connection. The module simply drops into the pcb in place of a mechanical relay.
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File Type: jpg BrySsr01.jpg (135.5 KB, 556 views)
File Type: jpg BrySsr02.jpg (129.6 KB, 525 views)
File Type: jpg BrySsr03.jpg (133.8 KB, 505 views)
File Type: jpg BrySsr04.jpg (127.6 KB, 485 views)
File Type: jpg BrySsr05.jpg (137.1 KB, 105 views)
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Old 6th July 2019, 01:39 PM   #24
amplidude is offline amplidude  Denmark
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Hello again.
Chalky I see you're making progress, despite you been sick, work also stalled here due to work overload and sickness, well my boards are almost finished, just missing a few parts, input works fine, also psu board, I decided to make it 4 channel with bridging option, I got my hands on a fat 2kw toroid to power the beast, now my worries are finding a suitable large chassis to contain it all, pretty sure it's going to cost the tip of a jet plaine, anybody got it working yet?.
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Old 6th July 2019, 01:44 PM   #25
amplidude is offline amplidude  Denmark
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Default Bryston 4bsst

A few pics..
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File Type: jpg 20190706_151636.jpg (760.2 KB, 191 views)
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Old 6th July 2019, 04:16 PM   #26
chalky is online now chalky
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Hi amplitude nice looking build. I notice that you've used the nice looking Russian emitter resistors but they're 0.2R rather than the 0.33R resistors specified in the BOM. Bryston themselves use 0.3R. I wonder if it matters much? I remember that you had problems powering up your amplifier modules - have you made any progress on this front? I'm building two separate stereo amps as I use active crossovers with my loudspeakers. Should make a start on my amplifier modules in the next couple of days.
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Old 6th July 2019, 04:55 PM   #27
amplidude is offline amplidude  Denmark
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Hi..
Regarding the emitter resistors, yes they are a little bit lower than specd but I don't think it matters that much, they are pretty accurate and the pcb traces might add a 0.1 ohm on top. I bought a big load of cold war resistors and silver micas, for little money, I hope their parts are as good as their vodka,

The power up as you mentioned is fixed faulty zener. I really like an update when you get modules running, by the way smart idea with your ssr relay as a plugin for regular relay, smart thinking, I might wanna copy your idea if the beast is working satisfactorily
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Old 6th July 2019, 05:18 PM   #28
chalky is online now chalky
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I haven't tested the SSR in a real amp yet but its works fine on the bench switching both ac and dc. The mosfets are FDP083N15A ( 150V, 117A, 6.85 mΩ on resistance ) and the photovoltaic optocoupler is ASSR-V621. Easy, but fiddly, to make on a small piece of perfboard. I'll take some pictures when I make the next one.
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Old 6th July 2019, 05:23 PM   #29
amplidude is offline amplidude  Denmark
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Sounds good.. I'll bet they work.. btw what's their current capability?

You stated the current... my bad..
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Old 6th July 2019, 08:29 PM   #30
chalky is online now chalky
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Had a look back at the power amp schematic and I notice that lower values of emitter resistors will mean that the output stage current limiting will kick in later than it would with 0.33R emitter resistors. This won't affect the power amp in normal usage but might result in output transistor destruction if its overdriven. Reducing the values of R26-R29 ( currently 300R ) should restore current limiting to the same point as with th 0.33R emitter resistors.
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