Finally made a LM1875 amp

[Sparky OR]

If you use silicone insulators, do you still apply heat sink compound? Thanks

 

[AndrewT]

the thermal compound is there to eliminate air from the interface.

If the surfaces are "hard" then compound must be used eg. mica, metal, Kapton etc.

If one of the surfaces is "soft" then the insulator itself fills all the gaps thereby eliminating the air.

 

[Nuuk]

I have updated the GC FAQ section on DD to show how to isolate the chips from the heatsink. You can see that here .

 

[fizzsweden]

Dont know if this is the appropriate place to ask this question, but i followed the link from chipamp.com, and is planning on ordering PCB/kit from there, so please correct me if im wrong ...

I have a question regarding the PS, and the large caps (10000 uF 50v Panasonic TS Capacitors (35mm x 30mm low profile)) ... Is it possible to replace them with 15000uf 63v ELNA? (see the attached picture)
Thanks in advance!

 

[AndrewT]

63V caps are a waste for a chipamp PSU.

They are more expensive and they are bigger.
Use 35V or 40V or 50V smoothing caps as appropriate for your chosen transformer.

 

[fizzsweden]

63V caps are a waste for a chipamp PSU.

They are more expensive and they are bigger.
Use 35V or 40V or 50V smoothing caps as appropriate for your chosen transformer.

I dont mind the size, and the reason for using them would be that I already own them ..

 

[androuski]

Hi everybody,
I've done a LM1875 stereo integrated gainclone from the chipamp LM1875 kit a few months ago :

http://www.homecinema-fr.com/forum/...=29900625&p=172360324&hilit=LM1875#p172360324

Now I would like to convert it in two separate mono blocks, so I'm wondering about the way I should wire the PSU ; can I wire each way with its own PSU leaving a part of the PSU board wireless as it appears on this photo ?

http://www.chipamp.com/images/lm1875-1.jpg

Thanks

 

[BoilermakerFan]

Hi everybody,
I've done a LM1875 stereo integrated gainclone from the chipamp LM1875 kit a few months ago :

http://www.homecinema-fr.com/forum/...=29900625&p=172360324&hilit=LM1875#p172360324

Now I would like to convert it in two separate mono blocks, so I'm wondering about the way I should wire the PSU ; can I wire each way with its own PSU leaving a part of the PSU board wireless as it appears on this photo ?

http://www.chipamp.com/images/lm1875-1.jpg

Thanks

To be true monoblocks, they need separate transformers and separate PSUs per chip. You would just need to use two smaller toroids and buy a new PSU board.

 

[androuski]

Yes I know I need a second PSU board and a second transformer, but I'm looking for something like a wiring diagram ; PSU is designed for stereo, so what shall I do with the part of the PSU unused ?

 

[AndrewT]

[two amplifiers powered from one PSU} - [one amplifier] = monoblock amplifier.

Which part of the PSU is left unused?

 

[androuski]

On psu board there is two +, two - and two ground, to feed two power boards in stereo configuration, so in mono configuration there is a part of those connexions that is left unused, just as it appears on the image below, where you can see mono configuration... I wonder if it can run like this as a finished product...
I hope I made me clear

 

[BoilermakerFan]

On psu board there is two +, two - and two ground, to feed two power boards in stereo configuration, so in mono configuration there is a part of those connexions that is left unused, just as it appears on the image below, where you can see mono configuration... I wonder if it can run like this as a finished product...
I hope I made me clear

Looks like the connections are just paralleled, shouldn't be a problem at all. I know on others LM3875s, you can power two amps from one PSU board or run dual PSUs. Shouldn't be an issue to have unused points. Have you tried to contact BrianGT? I sent him a PM and email and he hasn't replied to either. Probably use my spare LM3875 PSU and wire my LM1875 P2P.

 

[androuski]

Thanks
Is that mean that power capacity - I don't mean voltage, of course - is increased in mono configuration if the same 160 va 18 v transformer feed one power board instead of 2 ?

 

[korben69]

The Va rating will be divided in two if you feed two amps : 1 transfo / 1 PSU / 2 Amps.
It will be fully dedicated to one amp if you use real Dual Mono : 1 transfo / 1 PSU / 1 Amp.
1 x 160Va/18v gives +/- 8A, so 80Va/Amp for 2 boards.
Using 2 x 160Va/board will deliver 160Va/board.

 

[androuski]

Thanks,
now all is clear

 

[AndrewT]

Hi,
I can now see the spare pad V- next to the white output lead.
Yes, it looks like the PSU board has the option to power two amplifiers.
Expect performance to improve slightly when only one amplifier is fed from one PSU.
Similarly expect performance to improve slightly when one PSU is fed from one transformer.
And Finally, expect performance to improve slightly when each transformer+PSU+Amplifer is inside it's own separate chassis/casing This is a Monoblock configuration.

 

[androuski]

That's what I'm going to do... I've sent a mail to chipamp commercial contact to ask if I could order a single PSU kit, I'm waiting for their reply. The increased VA rating is a good thing for my project because those little monoblocks are going to feed a d'appolito pair of speakers, with two mid-woofers paralleled, which is more demanding than a single mid-woofer...

 

[AndrewT]

you could go further and drive each part of the crossover from a Monoblock.
Finally separating the paralleled drivers and feeding each of them from it's own amplifier.

 

[androuski]

Indeed,
that would be great,
but that means building another amp for biamping and buying 3 transformers,
which is far from my budget... Two

 

[AndrewT]

yes, that route is not necessarily good value for money.
There are certainly many other ways to improve the sound quality within your set budget, but monoblocking every driver is not one of them.

But, if you believe the amplifier you already have cannot be improved upon and you are looking for further improvement what other options move towards that target?