Hi Janey - why not go point to point? Bride is so simple. See my site http://users.computerweekly.net/peted/bride.htm for pics etc. Enough 'big' parts to string the rest off no problem. Ensure you attend to earthing (star is good), keep it compact, you can't go wrong.
OK, so I used a scrap of perf board for the PSU, but even this is simple enough to go point to point - again use the 'big' bits to support the rest.
Hi to all of you guys and gals! I just built the BoZ preamp and it sounded marvellous when used in conjunction with the Leach Amp. Only one small problem, humming (50Hz) and buzzing (100Hz)! Levels of humming and buzzing are low, inaudible if your ears are more than 2 feet away from a loudspeaker in a quiet room. But it still bothers me. Measured values of the combined hum/buzz/any other noises using the Fluke 87 DMM was around 2.0mV at the speaker output of the Leach Amp. By itself, the Leach Amp is absolutely silent.
Earthing/grounding is achieved via a central bolt (star grounding). All external input grounds, circuit board ground and the ground for the dual volume control pot (2 wires, one for each channel) are grounded to this bolt. Quality shielded cable leads are used throughout for signals and I'm being careful to ground only one side of the shield.
Initially, the noise level was 2.0mV and 4.5mV (at the power amp output) on each channel respectively. After I shift the position of the ground wire for the noisier channel away from the ground wire of the quieter channel, both channels have noise levels of 2.0mV.
Is this normal? I wish some of you can help me. Components used are as specified, with the exception of the resistors, which I have used generic metal-film types.
Sorry for a long winded posting.......
PS: The transistors are HOT! Have to change the heatsinks 3 times just to feel comfortable with the temperature!
2 mv is a very typical figure for unbalanced lines
in an ordinary listening room. If you isolate earth
grounds from the AC line ground except at one component,
you can often reduce this, as it breaks ground loops.
Another alternative is balanced lines, where we often
see another 10 dB less noise.
Thanks Nelson. One further question, what are the absolute maximum levels for the BoZ in its original form as per your design ie input level and output level? I am just wondering whether I'm running into clipping problems.
The input of the circuit will clip at 4 volts peak,
but depending on the output loading, output clipping
can occur at about 15 volts peak, which is about 1.5
volts input peak.
I continue to recommend the use of both an input and
output potentiometer. My favored means of adjustment
is to place the output pot at max and set the input
pot to the loudest working setting you will want. Then
use the output pot for a day-to-day volume control.