Get sixty pcs so to be conservative in the hfe gamble. When scoring a high averaging hfe batch the good ones are plenty. High beta brings better % pairing easier. If happy with the batch and you know how many good pairings it produces, get some more from the same source later but soon in case you have plans that they will be needed.
Average hfe ones are no slouches though. But we are never happy when we know there might be something bit better out there. Anyways, let us know how you liked the mod.
Yes, I'll report back. But it will take some (too long) time. First I have to receive the transistors here, with luck in 2 weeks, if not, after Christmas. Than I need them to measure and match, then... you know it. But I'll report back, when I have it in my system for a few weeks and tested it thoroughly.
Cheers,
Matthias
Cheers,
Matthias
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You would get them faster from the U.S.:
BC32740BU ON Semiconductor | Discrete Semiconductor Products | DigiKey
BTW Tea can you add a BC327-40 mod kit option of two 5% Hfe pairs and a 12 pins cut piece 0.1 inch female header for interested builders to can listen for what is it all about BC327 vs BC560 as Q1 Q2 and decide what they want right off the bat? Is it easy at all, or your 327s are a pain to sort and match ?
Yes. I will come up with a few options. I am not a fan of cutting those headers. I buy them in little 3 set combos.
It can kind of be like tube rolling I guess.
Hi folks,
I am attempting to build this preamp. It is my first project more complicated than a power supply. I have successfully built the DCSTBs - 17.49 & 17.44 volts. One channel of the DCG3 seems ok, although lower than I'd expect (103 mv with 7.7 ohm R10). The other channel doesn't work. I've re-flowed the solder, to no avail. I'm not sure how to proceed with trouble shooting. Any advice would be appreciated! Thank you.
I am attempting to build this preamp. It is my first project more complicated than a power supply. I have successfully built the DCSTBs - 17.49 & 17.44 volts. One channel of the DCG3 seems ok, although lower than I'd expect (103 mv with 7.7 ohm R10). The other channel doesn't work. I've re-flowed the solder, to no avail. I'm not sure how to proceed with trouble shooting. Any advice would be appreciated! Thank you.
Hi
First of all see about the small semis making sure that you didn't put some transistor in a JFET's place or vice versa. Then check that your MOSFETS are the right types in the right designations and that the C6 C7 capacitors are correctly oriented also. Post a picture of your DCG3 populated PCB if you can so we can inspect for something maybe obviously wrong.
First of all see about the small semis making sure that you didn't put some transistor in a JFET's place or vice versa. Then check that your MOSFETS are the right types in the right designations and that the C6 C7 capacitors are correctly oriented also. Post a picture of your DCG3 populated PCB if you can so we can inspect for something maybe obviously wrong.
There isn't a part that seems obviously put in a wrong place or reversed. Is there a chance your R8s are 3.33k instead of 33k? There's also a stray copper strand at the second pic's C6 rim near the power input, better clear that away.
Verify as many resistors values as you can. Also active parts characteristic operation DC voltages, Vgs in FETS & Vbe in transistors, make a pass list. Passable are about 2 or more volts in M3 about 4 volts in M1 M2 about 0.6V in BJTS and 0.75V to 1.1V for J3 (Q5) across R3. Also inspect the other side of the PCB for accidental things like a joint not done or a solder bridge created or too much flux residue especially around the MOSFET gates.
Verify as many resistors values as you can. Also active parts characteristic operation DC voltages, Vgs in FETS & Vbe in transistors, make a pass list. Passable are about 2 or more volts in M3 about 4 volts in M1 M2 about 0.6V in BJTS and 0.75V to 1.1V for J3 (Q5) across R3. Also inspect the other side of the PCB for accidental things like a joint not done or a solder bridge created or too much flux residue especially around the MOSFET gates.
Absolutely...but i'm always looking for the «little something more»
i think i will focus on building the current version first....
Update
Just a quick update to say that my DCG3 is up and running - it was indeed the extra earth wire from the amp audio ground to the iSelect OV out point that caused the diodes to blow, thanks Salas for the correct diagnosis!
Initially I replaced the diodes and got it working without the earth short but found that I had quite a bit of mains hum if I turned the volume right up (no music playing!) - this was on all inputs. Remember this is still breadboarded so the audio earth is kind of floating, when my chassis arrives next week I'll earth it properly with a loop breaker from audio earth to protective earth. In the meantime, I found that taking DC from under the second big cap on one DCSTB positive rail and using that to power the iSelect board (diodes removed) cut out nearly all of the hum at max volume, so I'm happy with how it's playing at the moment.
This pre sounds amazing! I've got way more bass than I had before and the degree of rhythmic control and detail are superb. Sound stage is wide, deep and rock steady - huge thanks to Salas for the design and Tea for the excellent group buy and component matching
I'll post some pics of the finished article, just don't hold your breath, it may take a while!
Just a quick update to say that my DCG3 is up and running - it was indeed the extra earth wire from the amp audio ground to the iSelect OV out point that caused the diodes to blow, thanks Salas for the correct diagnosis!
Initially I replaced the diodes and got it working without the earth short but found that I had quite a bit of mains hum if I turned the volume right up (no music playing!) - this was on all inputs. Remember this is still breadboarded so the audio earth is kind of floating, when my chassis arrives next week I'll earth it properly with a loop breaker from audio earth to protective earth. In the meantime, I found that taking DC from under the second big cap on one DCSTB positive rail and using that to power the iSelect board (diodes removed) cut out nearly all of the hum at max volume, so I'm happy with how it's playing at the moment.
This pre sounds amazing! I've got way more bass than I had before and the degree of rhythmic control and detail are superb. Sound stage is wide, deep and rock steady - huge thanks to Salas for the design and Tea for the excellent group buy and component matching
I'll post some pics of the finished article, just don't hold your breath, it may take a while!