sorry the late hour Salas, I wanted switching from BC560 to BC237-40, but my provider only has stock of BC237. And can't find any datasheet on BC237-40. I suppose is the same. May I buy safelly BC237 ?
It lives at the first attempt! Music coming from my lash up rig via an old Yamaha AV amp, some 20 year old Denon speakers and a CD player that is older than my daughter who's 22! Maybe tomorrow I'll jump right in and connect it to my main rig, cont foresee any problems but I'll leave it playing on repeat all night so it gets a bit of a burn in. Thanks Salas.
I now have the DCG3 hooked up to my main system, it’s super quiet, not a bit of hiss or hum from the speakers. I do however have a pretty major problem, I have just got waaaaaaaaaaayyyyyyyyyyyyy too much gain! I’m currently using just the power amp section of my Perreaux Eloquence 250i and I can use to about 8 o’clock on the pot and it’s very loud. Checked the manual and I have 28.8dB of gain in the power amp - how low can I take the gain on the dcg3 (currently set to 3 with a 1k) without causing any issues?. Long term plan is to get a different amp but what’s the best approach to reduce the gain in the time being?
What value are you using for R6? Build guide has comments on page 3, item 4.
Less resistance at R6 should reduce gain, with the caveat that unity gain isn't possible.
Less resistance at R6 should reduce gain, with the caveat that unity gain isn't possible.
I believe 500R is lowest possible value. My lazy man test would be to put another 1K on R6 to get to 500R to see. Salas would have to validate that is lowest possible value.
You can hang a resistor from the source input to the potentiometer input. Choose R same as volume potentiometer. This creates sort of a virtual potentiometer with double the input resistance and only half way can be put out via the wiper ( middle pin). The virtual pot turns only half while your knob turns full. And easily reversible too[emoji106]
Although an input voltage divider is possible, it's better to fix the gain lower via R6. Not to narrow the bandwidth with inevitably higher source impedance. Since this circuit isn't input buffered. Can go down to 500R R6 as mentioned. The amplifier's gain is high enough, maybe the speakers are sensitive enough also? Anyways, when in a loud combination the background is still reported quiet after adding 3x, that surely points to a good preamp build.
I'll try and source some Dale 499 ohm in the UK to lower the gain. A quick google pops these up, Salas can you confirm these are what I need? Vishay Dale CMF55 resistor 1% 50ppm 499ohm - Audiophonics
I also have 4 BC327-40 all with 499-502 hfe so I'll pop them in as well.
I also have 4 BC327-40 all with 499-502 hfe so I'll pop them in as well.
Those resistors are fine, same as the kit's others. That change will bring your gain down to 2/3 of what's now. You will probably like the alternative current mirror transistors too.
You need insulation pads and insulation grommets for each MOSFET to that sink. The sink itself can be fixed non insulated to the chassis.
Hmmm what would you recommend... The Bc560 or the Bc327-40?
I'm not sure until now.... Since there were both in my package
I'm not sure until now.... Since there were both in my package
