Group order of non-inverted LM3875 pc boards? Anyone interested?

[Anorgan]

So what is there to order besides LM and resistors?
I'm interested in some binding posts (speaker and RCA), 5KOhm stereo pot.

 

[BrianGT]

To those thinking about getting boards, if you need hardware, read on.

If you're a Cardas fan, the 2nd annual Cardas bulk purchase is well under way. If you're interested see this thread in the trading Post Forum and the WIKI Page for details.

I have already started to send order confirmation emails to those that already placed their orders.

I will be accepting requests for the price list up until Wednesday, the 25th at 12 midnight EST.

PS: I will delete this post after Wednesday.

So what is there to order besides LM and resistors?
I'm interested in some binding posts (speaker and RCA), 5KOhm stereo pot.

See the above quote from Rodd for the binding posts and rca jacks. I am not going to include them in my kit order.

As for the potentiometer/attenuator, if anyone finds a decent deal on one, I will consider adding it to this order. I am looking to see if I can get some 20k stepped attenuators for mine, like the one in the picture that i posted a few posts back.

--
Brian

 

[idex]

Brian,

Can you edit your 1st post to include the wiki? I think that help those who are new to the thread.

Matt

 

[JCoffey]

OK, I put in my order.

 

[jlh28]

Re: Re: stepped attenuator

If you want the uninsulated version, put it in the Comments field, and I will see what I can do later. It might cost a few dollars more.



I started this group order less than 24 hours ago, and it has gotten big quite fast. I am going to wait a few more days, and see how large the demand gets for this. I haven't decided where I am going to source the parts from, as it will be determined by the quantity. I will work out the details of this, hopefully by the end of the week.

The Wiki is currently only a preliminary interest survey, and I will use this to look at the demand, and put together a kit and pricing structure.

Once the pricing and details are worked out, I will put together a shopping cart system on my website. I will be accepting money via paypal, once I work this whole thing out.

I can get some help from local friends in putting this thing together, as it seems like it will get larger than I imagined.

--
Brian

Sorry, I was referring to the stepped attenuator that you used on the gainclone that you posted.

 

[moe29]

Brian,

I hate to add another part, but a heat pad would be nice to have
in the package for the LM3875.

What do you think of this Digi-Key Part?

BER180-ND Bergquist Heat Sink Pads.

I've used the Sil-Pad 900-S material with MOSFETS in other amps
and it works well. The above part seems to fit the dimensions of
the LM3875. A quantity of 100 would make them 0.59 cents a piece.

I was thinking for addional parts like this, if they weren't included
in the buy, we could make up a reccomended parts list for buyers
to obtain on their own.

Like that On/Off switch that incorporates the AC Inlet (and fuse?),
one of those would be nice to have too!

 

[Variac]

Brian, OK I know this could become a PITA for you, and the amount of money maybe a hassle, but when you get these bulk rates of over a hundred, you can include parts that some people might not prefer, but they wil be so cheap that it really doesn't affect the bottom line much.

I suggest that you don't try to satisfy everyone. If they want a parts kit they can order one or two variations, A standard model and a deluxe. If they end up with a few parts they don't want, it only costs them a couple of dollars more and they have some extra stuff in their parts boxes.

I'd much prefer a very complete kit, and end up with a few parts I decide not to use, than to have to order a few parts separately.
If you only have 2 kits then making up the packs would be a lot easier. 5 variations will make you insane, but people will try too make you do it!!!



The total cost will still be a lot lower than ordering a small quantity of all the parts at the low quantity rates and paying shipping..

The only pieces that is probably not a good idea to include are the transformers, heatsinks, probably the pots are a problem too- mono?, stereo? high quality? , low? stepped?

also- don't need silpads if it is the insulated version.



Mark

 

[BrianGT]

Brian,

I hate to add another part, but a heat pad would be nice to have
in the package for the LM3875.

What do you think of this Digi-Key Part?

BER180-ND Bergquist Heat Sink Pads.

I've used the Sil-Pad 900-S material with MOSFETS in other amps
and it works well. The above part seems to fit the dimensions of
the LM3875. A quantity of 100 would make them 0.59 cents a piece.

I was thinking for addional parts like this, if they weren't included
in the buy, we could make up a reccomended parts list for buyers
to obtain on their own.

Like that On/Off switch that incorporates the AC Inlet (and fuse?),
one of those would be nice to have too!

The insulators would probably be a good idea to include with the order. I will consider this, when I finalize the order. I don't think that the Corcom power entry module should be included in the order, since it is rather expensive ($15 for one, $11 each for 25, $10 each for 50).

My goal is to get the cost at around $50 for the pcbs and for all the parts for the pcb and power supply pcb. This would be for 2 channels. I want to get 2 channels and one power supply board on a single 3" x 2.5" pcb, that is scored for easily breaking it apart.

I am trying to set realistic goals, and minimize the parts count for the boards, as I don't want to overwhelm myself, having to stuff 20+ different kinds of kits for 100+ different people would not be fun.

--
Brian

 

[chris ma]

Absolutely...

Brian, OK I know this could become a PITA for you, and the amount of money maybe a hassle, but when you get these bulk rates of over a hundred, you can include parts that some people might not prefer, but they wil be so cheap that it really doesn't affect the bottom line much.

I suggest that you don't try to satisfy everyone. If they want a parts kit they can order one or two variations, A standard model and a deluxe. If they end up with a few parts they don't want, it only costs them a couple of dollars more and they have some extra stuff in their parts boxes.

I'd much prefer a very complete kit, and end up with a few parts I decide not to use, than to have to order a few parts separately.
If you only have 2 kits then making up the packs would be a lot easier. 5 variations will make you insane, but people will try too make you do it!!!



The total cost will still be a lot lower than ordering a small quantity of all the parts at the low quantity rates and paying shipping..

The only pieces that is probably not a good idea to include are the transformers, heatsinks, probably the pots are a problem too- mono?, stereo? high quality? , low? stepped?

also- don't need silpads if it is the insulated version.



Mark

The idea is not to hunt for parts from different supplier. Once the package arrive I can light up my soldering iron


Keep the kit generic and make it easy on yourself, you already do us a big favour on the PCB.

Chris

 

[BrianGT]

Re: Absolutely...

The idea is not to hunt for parts from different supplier. Once the package arrive I can light up my soldering iron


Keep the kit generic and make it easy on yourself, you already do us a big favour on the PCB.

Chris

I am looking forward to having this amplifier in kit form for myself as well. I have several friends wanting their own gainclone amplifiers. I love an amplifier that you can build in several hours.

--
Brian

 

[Variac]

I love an amplifier that you can build in several hours.

That should be the motto and driving philosophy

 

[Peter Daniel]

I'm not completely sure about it, but my today's experiments indicate that insulated case (plastic encased) sounds probably better

 

[elizard]

I'm not completely sure about it, but my today's experiments indicate that insulated case (plastic encased) sounds probably better

As always I respect your opinion. Plus it is a lot easier dealing with the insulated cases when you have the option to. As well, seeing the chip doesn't require some amazing heatsinking needs, using an insulated vs. non-insulated chip isn't much of a problem.

 

[net-david]

Brian,

What about the possibility of getting a transformer from Victoria Magnetics. Special deal on a volume purchase?

David

 

[moe29]

from reading posts in the past, it seems the VM sells at the lowest
cost already - group purchases don't bring the cost down. The
guy has to make a living!

They could maybe arrange a special order# so that they know
exactly what transformer to make, and it could cut down on the
lead time - meaning we might get them a little bit faster.

Brian has had lots of dealings with them, so he'd know for sure.

 

[moe29]

Even with an insulated case, don't you still need a heat pad, just
for better heat transfer between the chip and the heat sink?

 

[Sheldon]

.

I suggest that you don't try to satisfy everyone. If they want a parts kit they can order one or two variations, A standard model and a deluxe. If they end up with a few parts they don't want, it only costs them a couple of dollars more and they have some extra stuff in their parts boxes.

I'd much prefer a very complete kit, and end up with a few parts I decide not to use, than to have to order a few parts separately.
If you only have 2 kits then making up the packs would be a lot easier. 5 variations will make you insane, but people will try too make you do it!!!

Mark

I like this approach too, if you're game. The cost is not so much an issue for me, as is convenience. After all, these have a very high cost/performance ratio as is. I don't mind paying extra for the convenience(I'd go for the corcom). Prepay is fine too, so you're not financing us and I don't have any problems with you cooking in some profit for your efforts.

Sheldon

 

[Variac]

Hey Moe 29,
all you need is some heatsink grease no heat pad reqd. In fact the heatpad adds more heat resistance, so is more likely to cook the chip.

 

[BrianGT]

from reading posts in the past, it seems the VM sells at the lowest
cost already - group purchases don't bring the cost down. The
guy has to make a living!

They could maybe arrange a special order# so that they know
exactly what transformer to make, and it could cut down on the
lead time - meaning we might get them a little bit faster.

Brian has had lots of dealings with them, so he'd know for sure.

If people want a common transformer, I can call John and nail down the specifications, and it can be referred to the "Gainclone transformer that Brian ordered".

Even with an insulated case, don't you still need a heat pad, just
for better heat transfer between the chip and the heat sink?

No, you do not need a heat pad between the 2 surfaces for the insulated chips, but I did use some heatsink compound when I used the insulated chips. I did read that the non-insulated chips have better heat transfer characteristics, so I will stick to these for now.

I like this approach too, if you're game. The cost is not so much an issue for me, as is convenience. After all, these have a very high cost/performance ratio as is. I don't mind paying extra for the convenience(I'd go for the corcom). Prepay is fine too, so you're not financing us and I don't have any problems with you cooking in some profit for your efforts.

Sheldon

I will work out some kits and pricing at the end of the week. I looked into getting pcbs made today, and I am going to go for a 1-week production time frame. As for the prepay, this would work best, due to the large amount of money that I would have to put on my credit card, which would probably max it out.

Does anyone have any numbers for the cost on international shipping? I am willing to do this, as it is paid for. I have filled out custom forms for mailing stuff to Canada and the UK before.

--
Brian

 

[PHR]

Thanks for the effort

I am for 6 Kits (added to the wiki page)

Thanks

PHR