Gainclone building thread based on BrianGT's boards

[kestrel200]

And in cas you missed it the 1st time here's what the chassis looks like.

 

[NealG]

Neal, where do you join the output of one reg with the ground of the other reg to make the ground?

Hi Carlos, I join the two regs together and take a single wire back to the star earth.

From the regs to the amps goes around 10~15cm of wire.
What cable do you use?

I have about the same, 12cm from the regs to the amp chips. I am using multicore 24 strand 0.2mm (24/.2) wire for the supply rails and ground returns.

Thank you for highlighting the datasheet notes, I wiil try an input bypass cap as my main reservoir caps are about 8cm away from the regs.

I agree about the recommended values the sound is

Neal

 

[LTK]

Well its almost finished, I just got the psu board for the buffer to do and a few other bits.
What sort of speaker cable are you guys using with the regulated clone?

 

[troystg]

GC pwr miss-hap

HEY Brian-

I bought some 3 amp slo-blo fuses today, and they survived the pwr up.

I then measured the dc offset on the speaker leads, and had -2 volts DC on one, and 32 volts DC on the other..

I guess I need to order a couple more LM 3875TF chips... .



Thank you in advance,

Troy

 

[carlosfm]

Something's wrong there.
You are putting a stronger fuse, you may your trafo.

 

[Peter Daniel]

Carlos ,

Don't forhet he's in US and current draw is double what you have in Europe

 

[BrianGT]

Re: GC pwr miss-hap

HEY Brian-

I bought some 3 amp slo-blo fuses today, and they survived the pwr up.

I then measured the dc offset on the speaker leads, and had -2 volts DC on one, and 32 volts DC on the other..

I guess I need to order a couple more LM 3875TF chips... .

Thank you in advance,

Troy

Troy,

Start by removing the outputs from the rectifier pcb (power supply pcb), and measure the voltages from V+ to PGND- and V- to PGND-, to make sure that you have the transformer wired up properly.

Once you verify that the voltages are correct, we can proceed from there. I can send you some new chips if the power supply voltages appear to be correct.

--
Brian

 

[carlosfm]

Carlos ,
Don't forhet he's in US and current draw is double what you have in Europe

I know, Peter.
But he blew some 2.5A fuses.
Now he put in a 3A fuse and it doesn't BANG!
With those voltages on the output, something is definitely wrong.
If he lets that thing powered on for a little longer than a few seconds, he may the trafo and the fuse will be intact.
I think it was a wise advice.

 

[fdegrove]

FAST & SLOW....

Hi,

1) 2.5 amp fast blow fuse big enough?

I bought some 3 amp slo-blo fuses today, and they survived the pwr up.

Cheers,

 

[carlosfm]

Oh...
I didn't notice that...

 

[fdegrove]

Hi,

Oh...I didn't notice that...

In case you haven't noticed...Portugal beat Spain tonight as well.

And get that beer out of the freezer before the bottles burst, Carlos....

Cheers,

 

[carlosfm]

Oh yes Frank, I noticed.
Check this:
http://www.diyaudio.com/forums/showthread.php?s=&postid=421389#post421389

 

[Lurien]

Whats the best way to get in touch with Brian GT? I've sent him a few emails, however I have yet to recieve a reply.

The reason I need to contact him is because I placed an order recently, however I believe I gave the wrong shipping address.

Thanks,

Lurien

 

[Illusus]

He usually responds to email very promptly. Maybe he's away or swamped, I'm sure he'll get back to you soon.

 

[BrianGT]

Whats the best way to get in touch with Brian GT? I've sent him a few emails, however I have yet to recieve a reply.

The reason I need to contact him is because I placed an order recently, however I believe I gave the wrong shipping address.

Thanks,

Lurien

Sorry for the delay. I updated the address on your order, and I forgot to reply to your message.

Let me know if you need anything else.

--
Brian

 

[troystg]

Best way to reach Brian?

Hi!!

Are you kidding...? Brian is telepathic.

If you even think about posting he is at his keyboard read to respond!..

If it didn't take up so much energy, I would wonder if he never sleeps..


Hey Brian, I will measure the voltages on the amp board, but I'm pretty sure the chips are toast.

Please just let me know how much to paypal for a replacement set.. And I am more than happy to try TS'ing in the mean time.



Thanks again,

Troy

 

[NealG]

Hi Carlos,

Been through the regulator output cap values again this eve. But this time with an input bypass cap! Adding the input cap has stabilized the amp. Note to anybody implementing the regulated supply: Don’t forget the input bypass cap on the regulator!!

All reg output cap values are now stable and after going through .47/.22/.1/.047 and back again! Twice! I thought the .1uF sounded best in my system, I liked the .22 before, the .047 was just too bright for me, so cheers! Gotta go as I think a certain football team are playing tonight and if they win will play Portugal in the next round!


Neal

 

[carlosfm]

Hi Carlos,
Been through the regulator output cap values again this eve. But this time with an input bypass cap! Adding the input cap has stabilized the amp. Note to anybody implementing the regulated supply: Don’t forget the input bypass cap on the regulator!!

That's it, Neal!
I have the bad habbit to always bypass near the chips...

 

[joensd]

Hi,
just soldered the first kit together.
Can it be that the schematic is a bit different to the PCB?
In the Kit-users guide R2 goes directly from IN to GND; on the PCB it does after R1.
If I missed a recent discussion about that please ignore.

Thanks again for the effort Brian!

Regards
Jens

 

[BrianGT]

I thought I would revive this thread, with a picture of how the optional zobel network can be installed on the current pcbs:

An externally hosted image should be here but it was not working when we last tested it.

The components that are intended to be used are:
0.1uF BC polypropylene: Digikey BC2054-ND
2.7uF 2w panasonic metal film: Digikey P2.7W-2BK-ND

As you can see in the picture, I accidently ordered the 3w resistors. The 2w resistors mount on the bottom of the pcb quite nicely. The 3w resistors have a bigger spacing, so I put them on the top of the pcb.

I will test the amp and see what kind of difference the Zobel makes. I also mounted the feedback resistor on the pcb, to see if I can notice any change.

Just some ideas for experimentation. I haven't tried the Zobel yet so try at your own risk.

--
Brian