First Lm3886

[anatech]

Hi Stuey,

Interestingly, that won the Grand Prize for the best design idea for 2001...and the designer won $1,500!

That's the part that's killing me. This guy who designed the circuit did have an inventive idea for sure. The problem is that he didn't let safety stand in the way of his ideas. I sure hope he didn't have anyone put that circuit into operation!

As a subscriber to that magazine (EDN), would have hoped that they also judged the designs on whether they were acceptable or not if you actually attempted to pass equipment for safety certification. They normally have great ideas, thought provoking at least.

You know what this situation proves? Safety organizations are a necessary evil simply to protect everyone from others who simply can't see beyond the end of their pencil.

Hi PJPro,
Those are great looking buttons, but last time I checked, they were a tad bit expensive. Really nice switches though.

I think you have the right idea there. To take stock of what your overall plans are, and how you will work towards them through time.

As far as capacitors go, reasonable film types will be better than a tantalum or electrolytic. Stay away from stacked ceramic! Generally speaking, the lower the K of the dielectric is, the better sounding the capacitor should be - within reason. That is a very general guide. Also watch the dielectric absorption, that you want to keep low as well. Don't sweat it though, caps are easy to change, and you may find that the differences between some are not audible.

-Chris

[PJPro]

Originally posted by anatech
Hi PJPro,
Those are great looking buttons, but last time I checked, they were a tad bit expensive. Really nice switches though.

Agreed. But I want to get nice switches right from the start and avoid modifying the equally expensive front panels.

Originally posted by anatech

As far as capacitors go, reasonable film types will be better than a tantalum or electrolytic. Stay away from stacked ceramic! Generally speaking, the lower the K of the dielectric is, the better sounding the capacitor should be - within reason. That is a very general guide. Also watch the dielectric absorption, that you want to keep low as well. Don't sweat it though, caps are easy to change, and you may find that the differences between some are not audible.
-Chris

I assume you are refering to the input caps. OK. I'll have a browse, perhaps on other forums, to see what's being used. I'd rather hoped that others would have experimented and found ones which best suited the chip amp.....although I understand these things can be very personal.

Chris, do you have a view on the ferrite beads as recommended by infinia. I don't doubt his word. I'd just like a second opinion. Failing that, I'll just buy them and experiment. I'd also be grateful for a steer on the inductor.

Thanks.

[PJPro]

Originally posted by Stuey
I think these may suffice. They simply need the same footprint and ratings.

http://www.jaycarelectronics.co.uk/p...T&SUBCATID=754

Edit: I just realised the 2C2 is a DPDT and that photo on Jaycar is just indicative, so that IS the right one IMO. See the link below where the -2C2 is rated at 2 x 5A (ie. douple pole) and both types have the same photo. So I'd suggest the -1C1 is the SPDT variant 1 x 10A which is what you need. Note Jaycar used the same photo for the DPDT, cat no SY 4052.

http://www.dt.com.au/category.php?cat=ELECT:COMP:RELAY

Many of the Aussie electronics businesses (like ESP) buy from Jaycar wholesale (called Electus) further suggesting that this might be the one.

Stuey

Thanks Stuey. If I can track down something appropriate it'll help me narrow down a suitable component here in the UK.

[PJPro]

OK. The ESP soft start boards are ordered. I'll wait until I've read the accompanying notes before I start to order any of the required components.

[anatech]

Hi PJPro,

I assume you are refering to the input caps.

Yes.
Off the cuff, most plastic dielectric types will commit fewer sonic evils than electrolytic or ceramic types may. I was trying to give you the tools to determine your local availability and whatever the future holds. I was not trying to be cryptic at all.

Epcos does make some good ones for example.

Chris, do you have a view on the ferrite beads as recommended by infinia.

I fully support what he has said. My own experience over time confirms that this is the best approach. A ferrite bead is not going to cause sonic problems. There isn't enough current flowing here to cause any non-linearity to occur. Give the RF an easy path to ground and a more difficult path into your equipment.

I'd also be grateful for a steer on the inductor.

Inductor for where?
Generally speaking, if you are passing any DC current, you want a gapped (EI) core. If the current will be AC only, a toroid might be a good bet. There are instances where toroid transformers have problems in AC supply for power due to "effective DC " caused by line waveform distortion. Personally, anything to do with AC power gets an EI core part in my reality.

-Chris

[PJPro]

Originally posted by anatech
Inductor for where?
Generally speaking, if you are passing any DC current, you want a gapped (EI) core. If the current will be AC only, a toroid might be a good bet. There are instances where toroid transformers have problems in AC supply for power due to "effective DC " caused by line waveform distortion. Personally, anything to do with AC power gets an EI core part in my reality.

-Chris

Hi Chris.

See the following quotes for the history on this, which stemmed from the filtering power inlet modules and other sources of RF.

Originally posted by Juergen Knoop
......rf will enter your amp at the other 'inputs' (audio in + speakerout) too....

Originally posted by infinia
Output RF intrusion can be seen on ESP Fig 2 = L1+R5
http://sound.westhost.com/project19.htm

Originally posted by PJPro
infinia, do you happen to know what the L1 component is which ESP is using to filtering on the output?

Originally posted by Ted205
L1 is an inductor. Have alook at the lm3886 datasheet under reactive loading

Originally posted by PJPro
I've had a look for inductors. Can anyone have a recommend a particular type? Has anyone used one in their build? The data sheet seems to suggest the inductor is used to counter capacitance due to long speaker cable runs (mine will be short). Will they also serve a RF filtering function? Grateful for any views on inductors.

The datasheet can be found here, with the reference to inductors on page 20.

Hopefully the above quotes will give you a quick way to understand where I am coming from. Thanks for any advice you are able to provide.

[infinia]

1) L1 construction is in the ESP link I provided (handwound air coil around resistor body). Hang it off the PWB to the output jack or a standoff.
2) search DIYA -solid state forum for individual posts using terms like "inductor+zobel+RFI" if confused after reading go to step 3).
3) It's included in National Semis test circuits and it's the right output circuit/network to use consisting of 4 parts.
4) It looks pretty cool too.

[Stuey]

Originally posted by PJPro



Thanks Stuey. If I can track down something appropriate it'll help me narrow down a suitable component here in the UK.

Hi PJ,

That Jaycar link IS in the UK - it's their UK mail order site. That's why I tried their UK site (a mirror of the Aussie one). I think they have a presence there nowadays.

You'll get access to the ESP secure site once you've ordered. The page for Project 39 has VERY comprehensive info, including a very clear drawing of how to wire it up to the switch and IEC socket.

Cheers

Stu

[infinia]

2watt resistor with 11-12 Turns of magnet wire

[PJPro]

Originally posted by infinia
1) L1 construction is in the ESP link I provided (handwound air coil around resistor body). Hang it off the PWB to the output jack or a standoff.
2) search DIYA -solid state forum for individual posts using terms like "inductor+zobel+RFI" if confused after reading go to step 3).
3) It's included in National Semis test circuits and it's the right output circuit/network to use consisting of 4 parts.
4) It looks pretty cool too.

OK. Gotcha. Yeah, I like the idea of fabricating my own inductor. The chipamp has the 2R7 resistor and 0.1uF cap already...so I just need the 10R resistor with the copper coil.

Thanks Infinia.