Clon C-3850

[chermann]

Hi again

i want to restat this project and wnat to simulate with LT spice. i do not change anything but i have got the strange error.

Error:
Expected device instantiation or directive here.
.set prb=0

??

Help please

kr
chris

 

[STOXX]

You should share your ASC file when talking LT SPICE.
Your OpAmp is likely hanging you up but I see lots of odd stuff there.

 

[chermann]

thx Stoxx...will try it

 

[chermann]

🙄 😒

its nor working...not good as morning starter 😆

 

[STOXX]

That asc file is working. All you need to do is swap the transistors and opamp to ones in your library and it should be a bingo. Then make changes to the schematic after it is stable.

 

[AndrewGM]

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

Hello Peter

I'm a bit late sorry !
I am very interested in how you did this conversion to use external regulation.
I've enlarged your picture to an impossibly large size to try and see your links on the pcb where the 7815 and 7915 were.
I mean the pieces of wire / bridge links soldered in place where the regulators once were.
If you can explain it I'll try it straight away - the LM317 must be be quieter than 78xx - a great idea, bravo.
Any other wire links to consider as well ?

Many thanks

A

 

[chermann]

Hi Andrew

7815 make a connection (bridge) of both outer pins (IN / out)

7915 made the connection/bride between the middle pin and the "right" pin

kr
chris

 

[Kleinhorn]

Hi Andrew,
you have to make 4 connections. Two at the regulators. You will see the thicker lines if you have soldered out. As Chris wrote, input and output is bridged at the regulators. The next two connections you have to make at the rectifier.The two holes left and right must be shortet. I used little silver wire, 0,8 mm.
Be sure that the wire bridges are a little bit higher over the PCB. If not you can shorten something...

Greets
Peter

 

[AndrewGM]

That's a much better picture Peter - thank you.
I can do that and I will very soon.
I'll let you know how it goes too - very much appreciated

 

[AndrewGM]

Thank you also to Chris ( Chermann ) very helpful explanation too.
I'll get on with it soon and post pics

 

[ilorev]

Found in an old magazine and found it interesting

 

[STOXX]

Cool

 

[trungdtmc]

Hello, i ordered a kit and tried it out to see how people were interested.
First, i didn't use the LM78/79xx LDO ICs and powered it from the Jung Superpower circuit. I also reduced its gain by 10dB by changing the feedback resistor to 220R.
On my desk there were some opamps so i changed and measured. the results are in the pictures below

 

[chermann]

Without make connection at the 78xxx/79xx like post668? its working?

 

[STOXX]

Nice work.
The million dollar question; do you like the sound?

 

[trungdtmc]

Without make connection at the 78xxx/79xx like post668? its working?

i didn't pay attention to the post, i connected it by observation and it works normally

 

[trungdtmc]

@STOXX yes, i quite like it, currently i'm using the SMSL D6s DAC to listen (although the source in my tests doesn't use it) but when combined with this Pre-amp it gives a more intimate sound feeling

 

[MrHifiTunes]

@trungdtmc do you hear difference between the opams? What is your preference?
I see some good opamp don't prefer so well maybe some compensation is needed for their high operating frequency.

 

[chermann]

@trungdtmc
You really need the gain of 10dB?. try to set the gain down and measure again...
kr
chris

 

[trungdtmc]

@trungdtmc do you hear difference between the opams? What is your preference?
I see some good opamp don't prefer so well maybe some compensation is needed for their high operating frequency.

Since listening can't be as fast as measuring i can't say much yet, there is just a slight difference when switching between 5532d and 1612a, i have to listen more
@chermann ok, i will try