"Mr. ED" Non-Inverting monobloc chip amp group buy.

[Russ White]

Ok folks,

I have been recieving emails out my ears for PCBs for my "Mr. ED" design.

Well, I can't really blame you, it is a great sounding amp.

I would propose we try a group buy. If I get at least enough orders for 20 boards I will go ahead and order some PCBs for us all to enjoy... Here is the low down...

Each board is a monobloc amp which has everything required on the PCB except the trafo.

The original thread about the design can be found here:
My NI chipamp Mark-II - Mr. Ed :)

This is a truly powerful chipamp with 10,000uf capacitance per rail and great clarity and speed, absolutely a very transparent and non coloring amp. You will notice there are no snubbers, and none are needed to achieve results you will have to hear to believe. This amp is very energetic and alive.

Certianly it would be a trivial task to add snubbers, but just try it as it is first, I think you will agree it is first rate.

The supply byapssing is very good, and a large number of variations are possible on the PCB. Ceramics or film, your choice.

The integrated power supply is extremely quiet because it is designed in a way to minimize EMI noise from the bridge and AC lines by placing those pieces of the circuit behind the the 10,000uf caps.

RF noise rejection is aided by the addditon of the optional low pass filter on input, and the optional zobel is there for those who wish to you use it, and I must admit I think it does help, especially with 4ohm speakers.

DC offset will be extremely low (<2mv on my amps) due to the implementaion of Ci as per the LM3886 datasheet, so the design is safe for nearly all speaker types.

The grounding scheme is very sane, with no nasty ground loops if built as indicated.

The GB would be for the 30mm 10kuf ps cap version which will also work for 25mm caps such as those 35V 12Kuf caps at apexjr.

The pricing would be as follow...

$9.50 for each mono PCB. So a pair is $19.00US.

No PS board needed!

Shipping would be $5.00 for continental U.S. and $6.00 for international orders regardless of the number of boards you purchase as long as I can ship USPS global priority. I request that all international orders please email me prior to ordering to ensure accurate shipping cost.

So if you would like this PCB GB please post your interest here.

Cheers!
Russ

[maf_au]

Hi Russ,

Put me down for 'at least' 2 boards. (and parts kits)

Once I have my Mauro up and running, I'll decide what I need

Russ, you were saying that this amp sounded at least as good as your Mauro when you first assembled it. Now that it has been running for a while, what do you think of the sound quality between them?

Michael

[Russ White]

Hi Michael, there is a difference in sound between non-inverting designs and inverting for sure.

I think you may be talking about my comments about my other (inverting-not) design, but this conversation is still worth having.

And Mauro's REF design is a hybrid inverting design where the LM3886 is really acting like a sort of voltage follower(at least as my feable mind understands it). And I must say there has never been anything like it to my knowlege. It is a great sounding amp, if a little finicky.

This design tries to take the best aspects of the non-inverting designs that I have seen and built and combine them into one monobloc amp. With a generous helping of knowlege gained from Mauro thrown in.

There are certain tradoffs with every topolgy. One nice thing about non-inverting Lm3886 circuits is the nearly non-existant penalty for high impedance input. That is a huge plus, especially if you use or need decoupling caps on input, or if you have a low current source like certain DACs.

I certainly also have a soft spot in my heart for inverting chipmaps because while input impedance must remain lower for good results (thus requiring more driving current) the results indeed are worth it as long as you design for that. So really, I like both!

In short, I believe this amp is a solid non-inverting design with high input impedance, but still very clean transparent sound. I think it is a proven approach. And the parts count is nice and low.

This is the kind of amp you can be sure just about anything could drive, and sound great with many types of speakers down to 4 ohms.

Cheers!
Russ

[naz]

Heya... I would love to get my hands on a pair of these boards if they are going to be selling soon looks like another fun project

Naz

[Russ White]

Originally posted by naz
Heya... I would love to get my hands on a pair of these boards if they are going to be selling soon looks like another fun project

Naz

Hi Naz,

Once I get commitments for 20 pieces I will make the order, it will be something like two weeks from that point when they will ship.

Cheers!
Russ

[Brian Donaldson]

Count me for 6. I've been wanting to make a cheap 6 chanel amp for all of the ceiling mounted speakers in my house.

[peranders]

Originally posted by Russ White
Once I get commitments for 20 pieces I will make the order..

Why don't you put a wiki page? Just copy on old one and change in the right places. Don't forget to change linked files. If you check my sig and group buy direction you'll be able to get some useful tips.

[Russ White]

Originally posted by peranders

Why don't you put a wiki page? Just copy on old one and change in the right places. Don't forget to change linked files. If you check my sig and group buy direction you'll be able to get some useful tips.

Thanks peranders. I will do that.

[jackinnj]

If you are sending them out to be produced why not use both sides of the board? This will give you the benefit of true star grounding on the verso -- you can dispense with the jumper. You can also create a power plane on the verso which ties to the star ground.

[Russ White]

Originally posted by jackinnj
If you are sending them out to be produced why not... etc.

Well, really because I am quite happy the way it is. Thanks for the comment anyway.

The single side copper helps keep the cost down just as it did for Mauro's boards.

Also, there already is a true star ground.

I am not after a redesign, after all, if it aint broke....

Only two short jumpers, and with 22 gauge wire it carries more current than a .15" 2oz track.

Cheers!
Russ