Well 'problem' solved in part. I have managed to connect the pre-amp section to the power section of the BK MF1000, ignore the red highlighted area
the bump at 50 Hz this is essentially measurement error with a unit driven by a PC and a poor DAC, look at the green section
Green line DAC with no connections and nothing on - you can see the 50Hz measurement error
Black line 500 connected with the normal mains cable so just the normal BPSP 500
Blue line 500 connected with the ring main not AV electric connection (no sockets left on this line for the test) so still just BPSP 500
Red line the 500 pre feeding the wiring BK1000 amp !! So BPSP 500 pre and MF1000 power
QUIET when runing through the 500 pre and as I know from removing the Frequency Contour control it seems all due to this circuit
I will do a little more listening BUT A-B just listening to the 1000 vs the 500 the 500 sounds quite a bit better (it’s 1.8db louder so I will adjust via the DSP and re-compare)
So next will be
Some light at the end of the tunnel
Maybe…..
Anyone have any knowledge of swapping out the BUZ900/905's for the Exicon 10N20's seems the Exicons might be better units ?
the bump at 50 Hz this is essentially measurement error with a unit driven by a PC and a poor DAC, look at the green section
Green line DAC with no connections and nothing on - you can see the 50Hz measurement error
Black line 500 connected with the normal mains cable so just the normal BPSP 500
Blue line 500 connected with the ring main not AV electric connection (no sockets left on this line for the test) so still just BPSP 500
Red line the 500 pre feeding the wiring BK1000 amp !! So BPSP 500 pre and MF1000 power
QUIET when runing through the 500 pre and as I know from removing the Frequency Contour control it seems all due to this circuit
I will do a little more listening BUT A-B just listening to the 1000 vs the 500 the 500 sounds quite a bit better (it’s 1.8db louder so I will adjust via the DSP and re-compare)
So next will be
- A-B to see if the 500 sounds better at identical volumes
- Add the spare caps to the one working 1000 amp and see if this helps (the caps are 20 years old but do measure okay) another 4 is £50...
- Do more reading on the MOSFETs as the original BUZ 900/905’s are only available in the old stock market at £30 each. I do need to ‘match’ an need to understand this more the 500 uses a similar unit https://www.exicon.info/PDFs/ecf10n20.pdf and these are available but they are not evidently a direct replacement so I need to read more - Claude ! These are £19 each. There are 12 in each amp, so to do all is expensive and I dont know how they age and what the differences are that £500 right there…. but perhaps the TO-247's will be okay at £5 each
- Talk to Tom at BK to see if I might be able to buy the 500 interconnect board and then build a LPS to run them, or think about building a frequency contour circuit - But I know this will be hard and I need a pre as the 42 seems noisy (yes even after adjusting the responses in this unit)
- Carefully think through is this is the right path these amps will have cost over £1k if I venture forward and need the SO2 transistors and so on - But there is always the reality that you cant reverse the current investment made
Some light at the end of the tunnel
Maybe…..
Anyone have any knowledge of swapping out the BUZ900/905's for the Exicon 10N20's seems the Exicons might be better units ?