Components group buy for Pavel Dudek's super Gainclone

[BNK]

Thanks for the update. One thing I was missing was the insulators for the LM4780. I was not able to find a suitable one from Mouser, ended up ordering a 1.375" square CPU Bergquist sil-pad from Digi-Key their number BER135-ND. Your quantities are more accurate also, the original BOM was for 2 boards and was short or over on some items. Good work!

Bob G.

What about these:
534-4671
534-4672
534-4673


http://www.mouser.com/search/Refine.aspx?Ne=1447464+254016&Ntt=*to220*+*mica*&Msb=0&Mkw=to220+mica&N=1323038+0

 

[BNK]

That heassink is perfect thanks BNK.

My pleasure, 007.

 

[jaybombalous]

I still don't get how to attach the LM4780 to the heatsink. I can't figure out if it needs to be isolated or not. I plan on attaching my heatsink with screws tapped to holes I drill in the heatsink. The holes on the board I will use are the ones adjacent to the VR's.

If I was to mount the heat sink at those two holes w/ no isolation washers, does that make the heatsink grounded. If it is grounded, then the LM4780 needs to be Isolated???

Please verify I am on the right track.

 

[bobgroger]

THe LM4780 case is at negative rail potential. If you do not isolate the chip the heatsink will be at ~-30 V. Aside from the obvious short circuit potential the heatsink might be a big antenna connected to the power supply. I plan to insulate mine. I am only waiting for transformers, as Antek was out of stock on the 300VA 22-0-22 ones. I am mounting heatsinks, regulators, and boards in the chassis this weekend. I may have to test with my 500VA 25-0-25 transformers for the BPA300 project.....

Bob G.

 

[peranders]

It's OK to have the big heatsink at negative potential. It's not a very sensitive spot the negative supply.

 

[BNK]

I updated the C24,C25 caps to United Chemicon 50V 15000uf.
Resistors should also be updated to Vishay according to Pavel's manual.

Bob,

Why did you choose the Xicon's?
Why did you went with resistors other than Vishay?

 

[bobgroger]

BNK,

I really did not put a lot of thought into component selection. I went with what was reasonably priced and in stock. Everyone should of course go with their preferences...

Bob G.

 

[BNK]

Bob,

I understand that upto your experience it won't make much of a difference?
I spent some time trying to find the exact caps (c24, c25) that Pavel suggested.
I didn't get any answer whether it would make a difference on the sound although as far as people go they even pay much on good caps (like black gates).

BNK

 

[bobgroger]

BNK,
My ears are not as sensitive as some people's. I can rarely hear a difference even when other people point it out. I wish I could. I even like the sound of Bose 901's...... Certainly you should use the exact parts list if you wish to experience exactly as Pavel intended.

Bob G.

 

[ppcblaster]

Someone Please explain

I updated the BOM a little.
In the included zip file there are two files:

1. updated BOM.doc - Mouser's bom.
To order just copy the first two columns and
paste them to mouser's BOM Importer (an
online tool that will convert the list to an
order).

2. basket.csv - farnell's (www.farnell.com) saved basket that
includes heat sinks, LM4780 & toroids.
Just login in farnell and load the csv file.

Still some parts missing from this BOM:
1. Spacers + mounting screws (so many options on mouser, any recommendation on size & screws?)

Not perfect but better.

I updated the C24,C25 caps to United Chemicon 50V 15000uf.
Resistors should also be updated to Vishay according to Pavel's manual.

Bob,

Why did you choose the Xicon's?
Why did you went with resistors other than Vishay?

I printed the original BOM and the update BOM. I just get confused comparing the two.

Is the update BOM. a total parts list to populate one board, or additional parts not on the original BOM? Please explain..

 

[jaybombalous]

updated to the name brand parts recommended in the original parts list. Not all parts can be found in one spot, digi key has more then the other websites I checked.

One thing mouser does not carry is the LM4780 chips.

 

[ppcblaster]

updated to the name brand parts recommended in the original parts list. Not all parts can be found in one spot, digi key has more then the other websites I checked.

One thing mouser does not carry is the LM4780 chips.

Is the updated bom a complete list to populate one board?

 

[BNK]

Is the updated bom a complete list to populate one board?

Almost.

What is missing is:
1. LM4780 - you can get it at digikey or farnel.
Farnel also let you choose suitable mica isolator for the
LM4780.
2. Mica Isulators for the LM4780 & VR1-2.
3. Screws & spacers/standoffs (you can get them at mouser/digikey but I haven't chosen the right ones yet - any recommendations by other members?).
4. Heat sink (Farnel has perfect one, you can also get suitable from Apex Jr., ebay etc.).
5. Toroidal transformer (Piltron is recommended - 300va 18-25V, Farnel also has suitable ones).
6. I'm not sure about the case Bob have chosen (optional) as to my calculations it won't fit the board and the toroidal transformer.

 

[ppcblaster]

Thank You

Almost.

What is missing is:
1. LM4780 - you can get it at digikey or farnel.
Farnel also let you choose suitable mica isolator for the
LM4780.
2. Mica Isulators for the LM4780 & VR1-2.
3. Screws & spacers/standoffs (you can get them at mouser/digikey but I haven't chosen the right ones yet - any recommendations by other members?).
4. Heat sink (Farnel has perfect one, you can also get suitable from Apex Jr., ebay etc.).
5. Toroidal transformer (Piltron is recommended - 300va 18-25V, Farnel also has suitable ones).
6. I'm not sure about the case Bob have chosen (optional) as to my calculations it won't fit the board and the toroidal transformer.

Thank you, now I understand, to submit a Bom for a quote, I can just submit the update.bom times two for the two boards I have, two LM4780's and Isolators, and Transformer.

How was the 18-25V selected? Is this the maximum this chip can handle? 24 X 1.4 = about 35Vdc ?

Also I see VR1-2, is that LM7812 and LM7912?

Please advise..

 

[BNK]

Re: Thank You

Thank you, now I understand, to submit a Bom for a quote, I can just submit the update.bom times two for the two boards I have, two LM4780's and Isolators, and Transformer.

How was the 18-25V selected? Is this the maximum this chip can handle? 24 X 1.4 = about 35Vdc ?

Also I see VR1-2, is that LM7812 and LM7912?

Please advise..

VR1 7812 L7812CP
VR2 7912 L7912CP

You need one transformer per board.
It depends on how you want to use the board.
If you want to run it stereo (60-80W) or bridged mono (120-140W).
stereo - 25V to 28V AC(60W - 80W) X 1.414 would give 35V to 40V DC
mono - 18V to 24V (120W-140W) X 1.414 would give 25 to 34V DC

I intend to use it bridged mono with 18V toroid. I would also like to try it with 25V toroid and also on stereo.

 

[BNK]

You can also order everything from digikey.
I'm sure that if you will send the original BOM from Pavel's document to their customer service, they will gladly make an order for you (I didn't try it but it seems reasonable).
Mouser & farnel (mostly for european countries) would also be happy to assist you.

 

[ppcblaster]

Re: Re: Thank You

VR1 7812 L7812CP
VR2 7912 L7912CP

You need one transformer per board.
It depends on how you want to use the board.
If you want to run it stereo (60-80W) or bridged mono (120-140W).
stereo - 25V to 28V AC(60W - 80W) X 1.414 would give 35V to 40V DC
mono - 18V to 24V (120W-140W) X 1.414 would give 25 to 34V DC

I intend to use it bridged mono with 18V toroid. I would also like to try it with 25V toroid and also on stereo.

I have a difficult time understanding bridged mono from stereo,

by mono does it mean the signal comes out of one end of the chip and back into the second half of the chip to be amplified again, producing 120W-140W?

 

[ppcblaster]

This one?

You can also order everything from digikey.
I'm sure that if you will send the original BOM from Pavel's document to their customer service, they will gladly make an order for you (I didn't try it but it seems reasonable).
Mouser & farnel (mostly for european countries) would also be happy to assist you.

 

[BNK]

Re: Re: Re: Thank You

I have a difficult time understanding bridged mono from stereo,

by mono does it mean the signal comes out of one end of the chip and back into the second half of the chip to be amplified again, producing 120W-140W?

Nope.
According to the LM4780 diagrams (It's the first time I look at it) the two opamps inside the chip work together (rather than one per channel) to produce the signal. One is connected to the + and one to the -.

 

[jaybombalous]

Thats exactly how it works, One half of the chip (dual chip) produces one half of the sound wave, the negative half and the positive half. Representative by the need for dual power rails.

If u make it stereo, then u are using both chips(dual chip) separately to reproduce the full sound wave, both the negative cycle and the positive cycle. This will amplify two channels, where bridged only makes use of one channel, because u need to use the negative and positive terminals of separate channels connected to one speaker.

When in bridged mode, u need to reverse one of the input signals, that way u are amplifying the negative side of cycle and not the positive cycle on both chips.

Sry for the noob explanation, buts that how I understand it.