Connect the 8 Ohm resistor again and then put your speaker in parallel with it. perform your tests again and see how the original test levels into the 8 OHM resistor alone were most likely WAY higher than you would listen to a speaker.
Most of the time people rarely get above a couple of watts RMS listening to a speaker in "normal" listening.
Most of the time people rarely get above a couple of watts RMS listening to a speaker in "normal" listening.
Sure it is. I can only measure with a DMM, but it's ripple at the output is ridicoulusly small. A very stable 5v psu.
Ray, in that little zip file Regi came up with he has the schematic. Its just an LM338 with a big heatsink (that part matters a lot but is relative to the size of the device), .1uf film or tantalum from each leg to ground, a thousand uF on input and 100uf on output if I recall. You can look at the LM317 datasheet and replicate the schematic where they use protection diodes. Then, put the caps in. Its super stable. I use the same one at home as a bench supply and its solid. If I have for instance 4.9VDC I can see it stable and unmoving at 4.92134VDC Just an 'off the cuff' number but thats how stable I can measure it. Unmoving.
The 8Ohm resistor does not replicate an 8Ohm speaker. An 8Ohm speaker with an AC signal into it will vary between maybe as low as 2Ohms to as high at even 40Ohms. Look at a speaker datasheet and you will see that it only 'averages' 8Ohms over the 20-20k frequency range.
Uriah
The 8Ohm resistor does not replicate an 8Ohm speaker. An 8Ohm speaker with an AC signal into it will vary between maybe as low as 2Ohms to as high at even 40Ohms. Look at a speaker datasheet and you will see that it only 'averages' 8Ohms over the 20-20k frequency range.
Uriah
Speakers are reactive loads and are frequency dependent. That is why they have an impedance specification and not resistance.
Not correcting Uriah, just building off his statement...
Good sight! yes, supply is being tapped from the main filter capacitors of the DCB1, aprox. +17v IIRC. Then it is regulated down to +5v with a regulator I mounted on a piece of vectorboard. This is the "official" psu for the LDR kit of the group buy. The schematic is posted some pages back, but just ask for it and I will repost, no worries
Someone (I think was Dario) posted a link to an Ebay seller that has available very cheap and nice built simple regulator boards with adjustable voltage.
Uriah, I didn't use the 1000uF input capacitor because I am tapping it from the DCB1, so it already shares a 4700uF cap from it. But yes, I used 0,1uF film cap from each leg to ground.
Is anybody interested in a stereo kit? I have a partial. It has 2 boards, 2 LM3886, all resistors except 1R 1/4W Metal Film. No Caps No Actives. Luckily if you are after the ultimate BOM ... Tom and Dario are still changing the game on this amp and the capacitor shoot out is still very live. This gives you a good start on the kit with parts that wont change and the actives, which you need to source, will not change either. Well, its all thats left so if you are on the fence you already waited to long, dont wait this little bit longer and totally miss out. $35.. Not bad huh?
LDR attenuator Instructions
First, boards are still available.
Second, here are instructions for how to build that mount and balance board to have yourself an LDR attenuator.
Lightspeed Instructions
First, boards are still available.
Second, here are instructions for how to build that mount and balance board to have yourself an LDR attenuator.
Lightspeed Instructions
Link to More Pics of Chassis
Finally I got what I needed. Remember that Chassis I was talking about a while back? Well, it is a really nice chassis but I wanted it to be perfect for the MyREFC so I got a bottom plate made for it. It perfectly matches the MyREFC boards and the 160VA toroids I have been selling. You can also fit easily a 250VA in the center and if you offset the 300VA about a quarter of an inch it will fit as well. This thing is ready to go. If you guys want them I am asking 165 each plus shipping. I think its safe to say this should remain US or Canada. Elsewhere would be silly for shipping costs, but if you must have one I will try to ship to other countries, just assume shipping will probably be 50+ to countries outside the US.
I only have 10 of these. One for me, one for Sonidos, leaves 8 of them and another half of those have been requested but I need to check and see if those folks are still interested. So 4-8 available.
Dimensions are 14" wide, 12" deep, 3.5" tall.
All screw holes in plate perfectly match the chassis. No drilling needed at all.
I think it will fit a large fllat rate USPS BOX!
Uriah
Finally I got what I needed. Remember that Chassis I was talking about a while back? Well, it is a really nice chassis but I wanted it to be perfect for the MyREFC so I got a bottom plate made for it. It perfectly matches the MyREFC boards and the 160VA toroids I have been selling. You can also fit easily a 250VA in the center and if you offset the 300VA about a quarter of an inch it will fit as well. This thing is ready to go. If you guys want them I am asking 165 each plus shipping. I think its safe to say this should remain US or Canada. Elsewhere would be silly for shipping costs, but if you must have one I will try to ship to other countries, just assume shipping will probably be 50+ to countries outside the US.
I only have 10 of these. One for me, one for Sonidos, leaves 8 of them and another half of those have been requested but I need to check and see if those folks are still interested. So 4-8 available.
Dimensions are 14" wide, 12" deep, 3.5" tall.
All screw holes in plate perfectly match the chassis. No drilling needed at all.
I think it will fit a large fllat rate USPS BOX!
Uriah
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The idea of "warm" changes with each person.
Greater than room temperature, yes.
Hot enough to make touching a concern, no.
In general the LM3886 DOES run warmer in this implementation due to the 318 being in the feedback loop.
But it is not more than a few degrees (C or F).
That IS a really nice case and I am happy to see that the back was silkscreened and has the balanced input hole stamped already. It looks very professional.
Do you think it possible to additionally purchase the RCA/balanced switch that bolts right in? I am assuming that switch would be of reasonable quality.
Does anyone have a favorite RCA female, XLR plug, or speaker terminals they particularly consider a good value? I want higher end looking stuff that reeks of value not snake oil.
Heat sinks on the side. Barredboss, on ebay, would be a likely candidate for supplying sinks. Any thoughts on dimensions from his offerings? I am a firm believer in cooler is better.
Would additional holes need to be drilled, top and bottom, to allow proper convection across the sinks?
Heat sink on the side eliminates capacitor shielding of the transformers. Will the trafos need to be shielded to keep noise low? They look awfully close to the signal path.
Any recommendations on stand off type and size would be appreciated. Mouser numbers would really rock.
Uriah, do you you plan to stuff one of these cases? It would be comforting to us newbie builders to have an experienced hand/mind evaluating such a completed project.
Regardless of the answers to the above questions, sign me up! Those are some nice looking cases that are just what this build needs.
Well done, Again!
rick
I've tried some chinese ones and I think that CMC USA makes very good ones:
RCA: CMC-805-2.5F
Binding Posts: CMC-858-S(G)
You can find them easily on eBay
I've also the pure copper versions of those and for sure they sound better, I don't know if the double cost is justified... it depends on how you value things...
If you don't mind using metric hardware in the attached 1.02 BOM you'll find them
Sure, these are the ones with the best price/performance relation I've tried:
NEUTRIK|NYS367-9|HEMBRA, FONO, CHASIS, BLANCO | Farnell España
and its matching pair:
NEUTRIK|NYS367-2|HEMBRA, FONO, CHASIS, ROJO | Farnell España
more colors are available
regards,
regi
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