Hi Bigun,
I'm looking at building a pair of the TGM7 to replace the GB150D boards (well 1 board as the other is missing) in a chassis. Bit of detail here: First DIY (sort of) Amplifier
Sorry to ask what may be an obvious question - the BC556 / BC546 have been 'obsolete' for some time, although you seem to be able to purchase via the Worlds favourite auction site.... Not sure if these items are 'genuine' or not?
Is there a substitute that you would recommend (from Digikey perhaps) that would be suitable?
I'm looking at building a pair of the TGM7 to replace the GB150D boards (well 1 board as the other is missing) in a chassis. Bit of detail here: First DIY (sort of) Amplifier
Sorry to ask what may be an obvious question - the BC556 / BC546 have been 'obsolete' for some time, although you seem to be able to purchase via the Worlds favourite auction site.... Not sure if these items are 'genuine' or not?
Is there a substitute that you would recommend (from Digikey perhaps) that would be suitable?
I have 2 fully built GB150 boards if anyone wants them... Currently doing Holton builds which are a bit more plug and play.
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You might be in the wrong thread - the TGM7 is a SOTA board design with surface mount, parasitic oscillation suppression and simplified thermal management. Nothing like the original boards from Greg.
BC546/556 obsolete? Well perhaps some manufacturers have changed names and brands but the product is still out there if you look around.
e.g. BJT & Bipolar Transistors RS Components
e.g. BJT & Bipolar Transistors RS Components
I just finished 4 ska150 boards, and I bought bc546c bc556c from diotec, they all have hfe between 450-565.
Remember Greg mentioned (a while ago) that if can't find "c", just buy a large number of 'b', then measure the hfe, use the highest. It's very possible that you could find hfe between 400-500 in 'b' class
Hi Bigun,
are some specific modifications required to run a 4R load with this amp? I used your LTSpice (VFA) schematic to run a simulation with 8R and 4R. With 4R, voltage during negative period is clipped at around -24V.
I changed the 5v6 zener to 12v and it seemed ok, the output waveform looked clean. I am not sure if that is ok or no, not that i know what i'm doing.
I like the form factor of TGM7, i was thinking to make a 4 channel amp and make a test with an active crossover.
are some specific modifications required to run a 4R load with this amp? I used your LTSpice (VFA) schematic to run a simulation with 8R and 4R. With 4R, voltage during negative period is clipped at around -24V.
I changed the 5v6 zener to 12v and it seemed ok, the output waveform looked clean. I am not sure if that is ok or no, not that i know what i'm doing.
I like the form factor of TGM7, i was thinking to make a 4 channel amp and make a test with an active crossover.