Mauro Penasa's INV GC/REF GC group buy.

[Russ White]

I don't see the inductor listed for the REF design, only the NIGCWIPS.

 

[Russ White]

I believe even for the NIGCWIPS the inductor is optional(might have to change the value of the output resistor as Mauro states here.

 

[BrianDonegan]

You know, I saw it in the pic at the beginning of the GB thread, and just assumed it was there. I guess not. No problem then.

 

[Russ White]

Brian, After looking for a while it seems everything is as it should be with the BOM and schematic from post #58 of the "REF" thread. I was just having a serious brain fart.

Cheers,
Russ

 

[earsandeyes]

Can you describe the smell of a brainfart to me?

Perhaps you can post a ***.WAV that we can play over the amp to compare our sonic impressions.

It is great work that you are doing guys!!!

 

[BrianDonegan]

Here's the BOM. I think it's complete (went over it again this morning and made a few fixes).

Raw price per kit is $56.25.

This does not include:
- shipping charges from the vendor to me,
- the price of bags and boxes for packing the orders,
- the shipping out to you.
- PayPal fee (2.9% + $0.30) per order

This is a little lower than before, and the kit price will be ammended. I have been trying to think of how to accurately get a shipping price from the vendor before actually ordering. I think I will simply estimate $7.50 per vendor.

So 7.50 * 2 = 15/15 = $1 per order.

Currently we are at $56.25 + $1 = $57.25 per kit + paypal + shipping

 

[BrianDonegan]

The Wiki has been updated.

http://www.diyaudio.com/wiki/index.php?page=Mauro+Penasa+GC+Parts+GB

 

[Russ White]

Great work Brian. Thank you so much!

One small typo in the parts list. The"LM319N" should be "LM318N". No big deal since we have the schematic, but it is a critical part. The digikey part number is correct.

This is a very good price for a kit like this.

Cheers!

 

[BrianDonegan]

Corrected BOM. Fixed part number of LM318.

Also, I wanted to point out that I selected the TF (insulated) version of the LM3886 so that finding insulator pads would not be an issue.

 

[Russ White]

I think using the LM3886TF package is a wise choice. Finding good isolators can be a pain because some have better thermal qualities than others.

 

[Kravchenko_Audio]

Good on one side bad on the other

The TF package is much more limited in it's ability to dissiapte heat. As such it can't be pushed as hard as the T package. There are good junction temperature curves in the data sheet.

MArk

 

[Russ White]

When you add a good insulator/isolator (which you will almost always need) to the T package's heat dissipation is comparable to if not worse than the TF package. But if you really want it, maybe Brian will accomodate you.

 

[Kravchenko_Audio]

Point Taken

You are correct Russ.

THere are differences in the curves to suggest that the full pack version does warm up faster and cool off slower even with an almost the same thermal transfer number. The note to read is the derating factor if I remember right.

THere is only going to be some difficulty if the heatsink is on the small side and the amp is driven hard with a power supply voltage nering the max. Keep to around 30 volts after rectification or after the regulator and you will be just fine.

MArk

 

[BrianDonegan]

I think the schematic for this version of the amp specified 24VAC, which results in 33.6VDC for the rails.

Speaking of heatsinks, would anyone be interested in including them in the kit? Here's what I was thinking:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=31489&item=7527192673&rd=1&ssPageName=WDVW

Have him cut 3" pieces. One piece for each amp (3 x 5 3/8 inches). 3" would be $4.38 each, plus shipping charges out course. Could go to 4" for $5.84 each.

 

[Russ White]

I think the schematic for this version of the amp specified 24VAC, which results in 33.6VDC for the rails.

Speaking of heatsinks, would anyone be interested in including them in the kit? Here's what I was thinking:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=31489&item=7527192673&rd=1&ssPageName=WDVW

Have him cut 3" pieces. One piece for each amp (3 x 5 3/8 inches). 3" would be $4.38 each, plus shipping charges out course. Could go to 4" for $5.84 each.

That sound like a great idea! If 4" can dissipate enough heat I would be in for that.

 

[Gmorris]

Would anyone be interested in these heatsinks?

I'll most likely be using the sinks on the left (cut to size) for this project. I have some extras I'm trying to get $15/pair for....or maybe trade towards the kit?

 

[earsandeyes]

3" or 4"

I am in for either 3" or 4".
Probably 3" will do.

E&E

 

[BrianDonegan]

Anyone else want to offer an opinion of heatsink size/have interest in them? I can add it to the Wiki and consider it seperate from the main kit.

 

[BrianDonegan]

Wiki updated with heatsink information and added to the grid. Just testing interest for now.

 

[mauropenasa]

Any informations:

I have found any numerations not correct on the BOM and have corrected it ( only the serigraphy references, the quantities are correct ).I attach the corrected version to verify. I Creed that you did a good work, Brian.

LM3886 T now TF: The T version ( not iso ) has theoretically a better ability of dissipate of the heat ( internal ) toward the heatsink. In my LM3886 circuit it has to dissipate " theoretically " a lot of energy if the load is 4 ohms. This calculations however I am in " sinusoidal continues power" that doesn't exist in the ordinary music. I have done my test with the "T" type (not iso), but I believe that for an "moderate" use goes well the TF type ( iso ) for the reasons lists from Russ...

Heatsink: I Suggestion to use a type with 1-1.2 °C/W of Thermal Resistance, with vertical development ( like NS- AN1192 by BR100 mod. )

Ciao

Mauro