If 0.01% (-80dB) is generally inaudible as some sources say, then you can use it to the full. Its still below 80dB when it does nearly rail to rail. You can even use +/-20V and an OPA2604 that takes such rails (better with a tiny sink on it) if you want near 40VPP swing.
Hi Salas,
I'm just about ready to power up my pre but before I make a mistake I want to run the trafo wiring by you. I'm using an Antek AS0518 which has two sets of 18v secondaries. I plan to run dual mono for the PSU, your PSU has a spot for the center tap in the AC in. Do I just hook the secondaried to the AC in as in option 1 in the attached pic, or do I need to wre the trafo to have a centertap like in option 2 and get two trafos ?
Thanks,
Paul
I'm just about ready to power up my pre but before I make a mistake I want to run the trafo wiring by you. I'm using an Antek AS0518 which has two sets of 18v secondaries. I plan to run dual mono for the PSU, your PSU has a spot for the center tap in the AC in. Do I just hook the secondaried to the AC in as in option 1 in the attached pic, or do I need to wre the trafo to have a centertap like in option 2 and get two trafos ?
Thanks,
Paul
Attachments
I managed to get my DCSTB power supplies up and running and measured +-17,1 V and +-17,4 V from the outputs without load, so I'm going to leave it there. I also loaded the PSU with 2x66ohm (~2x4,6W) load on one channel and the voltages were rock solid.
At first I had my Q1 and Q3 mixed on the other channel as I didn't notice they were MJE15031 and MJE15030 types. Luckily I didn't break anything, but the voltages were +-27 V on the screwed up channel... Just to remind people to be extra careful following the guide and schematics and not to haste as I did!
At first I had my Q1 and Q3 mixed on the other channel as I didn't notice they were MJE15031 and MJE15030 types. Luckily I didn't break anything, but the voltages were +-27 V on the screwed up channel... Just to remind people to be extra careful following the guide and schematics and not to haste as I did!
Attachments
According to my measurements the voltage changed from 17,4V (no load) to 17,1V (66ohm), but it was very steady. My load resistors were the limiting factor and they became quite hot as I had only two 33 ohm/3W resistors to use. So only about 5 min loading and allready the resistors were smelling quite bad. 😱
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That's very normal. Vbe loss gets more. So after the psu success and the nice lights here comes the preamp assembly time.
Hi Salas, regard to the Ca,Cb-can the value changes 0.1-.47?. I have plenty of those but not 0.15 as specified per bom guide. TIA.
Quan
Quan
What typo? Can't 0.01% distortion factor be also expressed as minus 80dB distortion attenuation?
100% = 0dB
10% = -20dB
1% = -40dB
0.1% = -60dB
0.01% = -80dB
0.001% = -100dB
0.0001% = -120dB = 1ppm
just to prove I got it wrong again.
Sorry.
10% = -20dB
1% = -40dB
0.1% = -60dB
0.01% = -80dB
0.001% = -100dB
0.0001% = -120dB = 1ppm
just to prove I got it wrong again.
Sorry.
Just some info for builders sourcing parts:
From mouser dn2540 came very well matched. All were between .01v of each other when measured across 6.8r resistor. Measured 1.08v for 160ma ish bias. Out of 5 devices they measured between 1.07 and 1.08v with 6.8r resistor. Nice.
Bc560 required about a dozen devices to get 4 with a hfe match within 5%.
I have not tested the bf256b. Will probably do that when it's in the circuit and adjust resistor values accordingly.
Here is some in progress pics. The case is too small, I know. Psu is lm317/337 followed by a cap multiplier that will sit on the sink opposite of the amp board.
From mouser dn2540 came very well matched. All were between .01v of each other when measured across 6.8r resistor. Measured 1.08v for 160ma ish bias. Out of 5 devices they measured between 1.07 and 1.08v with 6.8r resistor. Nice.
Bc560 required about a dozen devices to get 4 with a hfe match within 5%.
I have not tested the bf256b. Will probably do that when it's in the circuit and adjust resistor values accordingly.
Here is some in progress pics. The case is too small, I know. Psu is lm317/337 followed by a cap multiplier that will sit on the sink opposite of the amp board.
