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my_ref revC group buy (Mauro Penasa LM3886 design)

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#381
udailey said:
labeling for a few days now. WOW, not my idea of a lot of fun.
Well, I have been waiting for my B1 board to get here. Really looking forward to driving a pair of MyRefC with that.
Click to expand...

Can you start a thread on your MyRefC w/ the B1 buffer??? That's exactly what I'm doing and could use the tutelage. What are you using as a transformer for the B1?

I got in on the toolereg group buy, too.

😀
 
#382
Good move Marc. I am going to run mine off of two 9V batteries til I get the toolereg going. The toolereg threat has a list of parts and I think, not sure, transformer recommendations. Man at this low of wattage you could use some really nicely built tiny transformers. A potted transformer would be nice. Toroidal probably would be favored. Do you have your B1 board? Its an easy build. Get the article Papa wrote about it and read up. Its an easy read even for a novice, I think. Very good explanation of each individual part and why its there. You need 18V/0V or 18V/GND to run it. So just wire up your 9V batteries till your DMM says 18V and hook it up. Put a switch on the batteries. They will last a long long time.
Uriah
 
#383
#386
Apex Jr said:
I have some 24 V AC 1.2A wall warts just add a bridge
also in stock at $1.00..lot better than $20.00
but there only $3.95ea
Used in CATV use......

Steve @ Apex Jr
Click to expand...


Absolutely!!

As long as the mains voltage is not on the high side. 24 VAC rectified is 33.6 VDC.

The IC regulators are usually rated for 35VDC max input.

"* Vout: +18 V * Vin: +21 V min, +35 V max * Iout: 1 A * Case style: TO-220 "
 
#387
udailey said:
........ working on a little board to turn an unbalanced signal to balanced and back again to unbalanced. WHY? Well because when it goes into balanced for that short time it will remove the junk noise that came in on the input line and I don't have balanced inputs or outputs on my equipment.
Click to expand...
Am I misunderstanding something?
Surely, this is not right.
 
#388
udailey said:
Good move Marc. I am going to run mine off of two 9V batteries til I get the toolereg going. The toolereg threat has a list of parts and I think, not sure, transformer recommendations. Man at this low of wattage you could use some really nicely built tiny transformers. A potted transformer would be nice. Toroidal probably would be favored. Do you have your B1 board? Its an easy build. Get the article Papa wrote about it and read up. Its an easy read even for a novice, I think. Very good explanation of each individual part and why its there. You need 18V/0V or 18V/GND to run it. So just wire up your 9V batteries till your DMM says 18V and hook it up. Put a switch on the batteries. They will last a long long time.
Uriah
Click to expand...

Uriah,
I've read Nelson's article on the B1 -- very informative. I've also read the toolereg thread about twenty times and downloaded the hints document.

After looking at different options, I'm probably going to use an Amveco mini-toroid, manu ##62013 . It's 3.2VA rated at 30V when the secondaries are wired in series. In the toolereg thread they recommend specing 10V for regulation so 18V + 10V got me to ~30V.
 
#389
Marc,
Are you going to stick the B1 in its own case or will you put it in the case with the amps? Well anyway, you could take the voltage you need from the toroid you buy.
Maybe try this
http://www.herbach.com/Merchant2/me...AR&Product_Code=TM98XFR3088&Category_Code=XFR
The 19.5 volts will give 27.3DC then regulate down to 18V 🙂
Its cheap cheap cheap. Plus its an R core. Usually very expensive but very quiet.
Uriah
 
#390
Uriah,

I'd like to put the B1 in the case w/ the amps -- for a variety of reasons. I'm thinking of using aluminum dividers in the chassis to isolate the trafos from the amp and pre-amp sections I'm going to layout my enclosure in sketchup. Most likely the sides of the chassis will be wood with the components mounted to aluminum plates.

Thanks for the tips on transformers.

Marc
 
#392
The buffer belongs at the source not at the receiver.

It is normal to specify a transformer for a regulated supply where
Vac= reg Vdc, i.e for 18Vdc use an 18Vac transformer. It would do no harm to use a 20Vac or 21Vac transformer.

A 3VA 30Vac transformer has an AC output current maximum of 100mA. It will run at it's maximum temperature if you take this much out in continuous duty.

When you use a capacitor input filter the output from the filter is almost exactly half the AC rating of the transformer.

I suggest that the transformer run at <=50% of maximum rating for continuous duty.
So the 3VA 100mA transformer should have a maximum continuous DC current of <=25mA.
Is 3VA big enough?
 
#393
marc brown said:
Uriah,

I'd like to put the B1 in the case w/ the amps -- for a variety of reasons. I'm thinking of using aluminum dividers in the chassis to isolate the trafos from the amp and pre-amp sections I'm going to layout my enclosure in sketchup. Most likely the sides of the chassis will be wood with the components mounted to aluminum plates.

Thanks for the tips on transformers.

Marc
Click to expand...


Par-Metal has the "20 series" chassis that you can get internal dividers for. I use them to section off the pwr and signal sides.

In fact I think a picture is earlier in this thread...
 
#396
udailey said:
I think I would wire the B1 to have a power switch and turn it on after you turn on the amp. Not sure, someone could chime in. I wouldnt want that inrush current hitting my B1. That is, if you get power from the amps transformer.
Uriah
Click to expand...


CL60 and I would assume a voltage regulator would ensure no current rush.
 
#397
TOROIDS and AMP KITS PLEASE READ

Guys/Gals
The toroids look like they will fit in a 12x12x5.5 Flat Rate Box for Steve to mail to me. These are 12.95 each. At 3.6" x 2.1" per toroid we could get them in 18 per box. That leaves only 1 inch each way in three dimensions so one half inch of packing material on every side but none inbetween if he stacks them 9 on bottom 9 on top. Thats the cheapest but I dont like it. Better to pack 3 in a row on their side so that the toroids are all right up against each other with maybe a piece of cardboard inbetween them but no stacking. This way you have 5 rows of 3 with cardboard inbetween and some packing material on all sides. Then the mounting material would probably all come in one separate box. So I think all in all shipping to me will cost about one dollar per toroid, which I will pass on to you all. So your total, which you will see shortly, will include $22 per toroid plus shipping to you of 9.80 for a flat rate box plus one dollar per toroid for shipping to me.

=================

If you have an amp kit/kits already paid for your total will include $22 per toroid plus the one dollar per unit shipping to me and if you paid only 4.80 shipping to Peter then there will be an additional 4.50 shipping charge to cover the difference in cost for the upsizing to the flat rate box. If you paid 9.80 shipping to Peter you will only be charged for the toroids plus one dollar each for my shipping expenses.
Uriah
 
#399
Billy,

I thought about using the NS10 w/ my RefC. But then again, I like all of Nelson Pass' designs.

I finally settled on the B1 because of its simplicity. The power supply for my B1 is modeled after the NS10. Amazing how timeless a good circuit is.

Marc
 
#400
TOROID INVOICES

TOROID INVOICES SENT
If you didnt get an invoice by tonight then start emailing me.
Probably the GB threads are not the best place for a million questions. Hopefully its all spelled out and understood by now but for clarity's sake:
Toroids x $22 each
Toroids x$1 each for shipping costs to me
Price of shipping added. If in AMP group buy also and already paid shipping I subtracted that amount from the 9.80 Flat Rate Box fee.
TOTAL it all up and multiply by 1.03 to cover paypal expenses.

SO, for example 2 toroids
2x22 = 44
2x1=2
9.80 shipping
----
57.47

If you were in GB for AMPS and your shipping was 4.80 and you already paid that then

2x22 = 44
2x1=2
9.80-4.80 =5 shipping
Now multiply x 1.03
----------
52.53

Unfortunately I charged everyone in the GB .53 to little. Well, thats a $26 sting to me. Ouch. If you read this maybe try to put that in your invoice.
Thanks
Uriah
 
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