I saw the #91 circuit board, by ny gul, and heaavy outputs (Bd139…). I can’t find it - is this stille there and available? I also like the 15V zeners on the opamp to prtectthem from a higher Vb (like I plan to use).
Is the 100R feedback resistor the one to be changed to increase the gain? I tested the circuit in my system and the volume (with pot at 5 o'clock) is VERY low.
Hi guys
if you want to squeez out the best performance of this pcb/kit please read the thread and deside which change you want tot do.
kr
chris
if you want to squeez out the best performance of this pcb/kit please read the thread and deside which change you want tot do.
kr
chris
For all who wondered if the opamp could be left out for certain applications?
I removed the opamps of my cheap Chinese R2R DAC and also the one on this board to drive the discreete part directly of the resistor ladder and it works like a charm.
After fiddling with all sorts of DAC chips and output stages this is exactly the sound I was looking for. Natural organic with clearly defined imaging and something I did not expect, almost scary dynamics via my Sennheiser HD540 headphones. Bass precision and slam are the best I have heard so far.
Some have reported that on low impedance amps the sound quality takes a hit with the Accuphase clone.
If that's the case I highly recommend to put a tube pre behind it.
I had opened a thread with my test setup but there is very little response.
I removed the opamps of my cheap Chinese R2R DAC and also the one on this board to drive the discreete part directly of the resistor ladder and it works like a charm.
After fiddling with all sorts of DAC chips and output stages this is exactly the sound I was looking for. Natural organic with clearly defined imaging and something I did not expect, almost scary dynamics via my Sennheiser HD540 headphones. Bass precision and slam are the best I have heard so far.
Some have reported that on low impedance amps the sound quality takes a hit with the Accuphase clone.
If that's the case I highly recommend to put a tube pre behind it.
I had opened a thread with my test setup but there is very little response.
I blown a resistance of a MOFI C-3850 that since today was perfectly working. I measured the output of the toroidal (220 Vac --> 10-0-15 Vac) and is 17.8 Vac being the mains at 248 Vac (!). How can I regulate the mains (or transformer output) to avoid such instability?
Hi
you have a DC voltage regulator on board, so a regulation of your mains is not needed.
btw. it is normal that the main network has not always 230VAC.
chris
you have a DC voltage regulator on board, so a regulation of your mains is not needed.
btw. it is normal that the main network has not always 230VAC.
chris
IEC Norm 230Volt, +-10 % in europe...207-253 volts possible. If you get 248 vac you perhaps live near at a power station ?
Peter
Peter
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Sorry to bother. After a successful testing suddenly a resistance (see circled 22R) got burned soon after I powered up the board.
Anyone knows what's happening?
Anyone knows what's happening?
I guess your transistors after the opv is damaged and that burn the resistor.
De solder and check them
Look at post 497... Nice View for PCB and components
Kr Chris
De solder and check them
Look at post 497... Nice View for PCB and components
Kr Chris
Hello again, after a long time...too many projects...
My very little voltage regulater board had arrived a few days ago from China. The voltage regulators are not isolated to the heatsink and there is no thermal paste. Done two changes, isolated and used a bit thermal paste for better cooling.
Took out the LM7815/7615, big capacitors and the rectifier and made little new connections on the mofi board.
I bulit a mistake in by soldering the new connections. Ground and - were shorted...stupid..searched for half an hour to find this connection. 🙄
I am using a OPA1612 now (like it very much). I had to solder on a small pcb adapter.
With the OPA 1612 i get a wonderful (heavy, dark) bass, better than every Opa i used before. I like the OPA1612 more than LM49720/LM462.
The best news is..the white noise, i had before on my speakers, is gone now. Deadly silence.😀
Perhaps one of the original voltage regulators was a bit faulty. I got different rail voltages, not much, 14,97 volts to 15,02 volts. That could not be the reason.
No matter now it sounds very good. The C3850 can easyliy drive a headphone, like my DT990, with 250 Ohms.
Happy now with this little preamp...🙂
Greets
Peter
My very little voltage regulater board had arrived a few days ago from China. The voltage regulators are not isolated to the heatsink and there is no thermal paste. Done two changes, isolated and used a bit thermal paste for better cooling.
Took out the LM7815/7615, big capacitors and the rectifier and made little new connections on the mofi board.
I bulit a mistake in by soldering the new connections. Ground and - were shorted...stupid..searched for half an hour to find this connection. 🙄
I am using a OPA1612 now (like it very much). I had to solder on a small pcb adapter.
With the OPA 1612 i get a wonderful (heavy, dark) bass, better than every Opa i used before. I like the OPA1612 more than LM49720/LM462.
The best news is..the white noise, i had before on my speakers, is gone now. Deadly silence.😀
Perhaps one of the original voltage regulators was a bit faulty. I got different rail voltages, not much, 14,97 volts to 15,02 volts. That could not be the reason.
No matter now it sounds very good. The C3850 can easyliy drive a headphone, like my DT990, with 250 Ohms.
Happy now with this little preamp...🙂
Greets
Peter
Attachments
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I didn't like the fact that such a good preamp was set up with these 7815 regulators. I also want to buy this board and make setup like yours or maybe even better ( I have sigma 22 and Jung super regulators ,I think they will be much better than lm7815 and better than lm317/337 boards.
hi unmut1011
please dont forget that Peter=Kleinhorn made a new PCB ith LM317/Lm337 included.
thanks Peter !
kr
chris
please dont forget that Peter=Kleinhorn made a new PCB ith LM317/Lm337 included.
thanks Peter !
kr
chris
Looks very good Peter.
As good as those 1612/1656 are (been through many) at the end there is no getting around discreete opamps. Even the cheap Chinese ones exhibit more dynamics, better clarity, and 3D soundstage.
Best in order are: Sparkos SS2590 by a margin, Burson V7V and close behind the Chinese SX52B.
Greetings Klaus
Hi..
today evening i will take the C3850 clone with me to a regular table. A well known one has ordered a few (!) empty pcb's. I know he owns different opa's, much expensive opa's. I hope he shares his experiances...(but it can take a lot of time he finishes his project) 🙂
I have tried different Opa as Opa 1642, AD8599, Opa 627, LM4562, LME49990 (double), does not work correct. In the moment the Opa 1612 was the best i had in stock.
Greetings
Peter
today evening i will take the C3850 clone with me to a regular table. A well known one has ordered a few (!) empty pcb's. I know he owns different opa's, much expensive opa's. I hope he shares his experiances...(but it can take a lot of time he finishes his project) 🙂
I have tried different Opa as Opa 1642, AD8599, Opa 627, LM4562, LME49990 (double), does not work correct. In the moment the Opa 1612 was the best i had in stock.
Greetings
Peter
My project with a protodac and coax to i2s. Dead silent, a good combination. No major changes other then 2000uf on the input and 480r on the feedback.