Andrew: Also, I just got confirmation from Primrose that my transformer build has been added to the assembly line W/O . 120V - 850VA primary ; 2 x 45V loaded(47.xx unloaded) -401VA secondaries (per your tip on tapped vs untapped)
Thanks again!
Thanks again!
I know this probably varies among builders, but given prices are so similar between a lot of the resistors (within a couple cents), are there some brands that should be avoided? I've been picking "cheap" resistors with the tightest tolerance based on the recommend specs in the BOM.
EX : if Resistor "A" was 820R, 1%, 1/4 watt, metal film and
and Resistor "B" was 820R, 5%, 1/4 watt, metal film
and both were priced at $0.145 CAD; I would pick with the 1% regardless of brand...
For an extra couple of cents per piece I could use all one brand, etc. I'm just not informed on brands of passive components 🙂
EX : if Resistor "A" was 820R, 1%, 1/4 watt, metal film and
and Resistor "B" was 820R, 5%, 1/4 watt, metal film
and both were priced at $0.145 CAD; I would pick with the 1% regardless of brand...
For an extra couple of cents per piece I could use all one brand, etc. I'm just not informed on brands of passive components 🙂
Also consider Temperature Coefficient of Resistance. (TCR). How the resistance changes with regard to temp. And of course the resistor has to fit the board.
Thanks Evan.
1) Is it fair to say if the resistors are rated up to 150C, @ 1% that the TCR is good? I know there is a formula to calculate it, but I was just being lazy in the spirit of time 🙂 .
2) how would one be sure of sizes for fitment.... ? lol
Note: I have been ordering radial/ axial leads
1) Is it fair to say if the resistors are rated up to 150C, @ 1% that the TCR is good? I know there is a formula to calculate it, but I was just being lazy in the spirit of time 🙂 .
2) how would one be sure of sizes for fitment.... ? lol
Note: I have been ordering radial/ axial leads
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Go for 1% where available.
FWIW, I used Xicon resistors from Mouser for all the low wattage types and and very happy with the sound of my HB. Some say they can hear a difference going to Vishay-Dale RN60 or RN65 military grade resistors. Maybe I'll build a set of HBs otherwise the same as my current amp and see if I can hear a difference.
FWIW, I used Xicon resistors from Mouser for all the low wattage types and and very happy with the sound of my HB. Some say they can hear a difference going to Vishay-Dale RN60 or RN65 military grade resistors. Maybe I'll build a set of HBs otherwise the same as my current amp and see if I can hear a difference.
I see the mouser site doesn't allow you to select by size. I have noticed some of the mil. spec. resistors are quite large for their power rating.
A 1% resistor probably has a good tcr rating. This is a criteria you can use for sorting on the mouser site....Not super critical though.
A 1% resistor probably has a good tcr rating. This is a criteria you can use for sorting on the mouser site....Not super critical though.
Mouser and Digikey both are selling a lot of smaller package resistors. These normally run quite a bit warmer than normal size resistors. They may cause board browning when dealing with 1/2 Watt or 1 Watt.
If interested, there is a very good article in Linear Audio Volume 1 on resistor non-linearity. The inexpensive 1/4W Xicon measured better than other metal film resistors.
"Resistor non-linearity - there's more to Ohm than meets the eye" by Ed Simon
"Resistor non-linearity - there's more to Ohm than meets the eye" by Ed Simon
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That's because a MIL-spec 1/4 watt resistor is a derated 1/2 watt industrial resistor.
Most of the 1/4 watt resistors in the HB dissipate a few milliwatts. You shouldn't run into heating problems with them.
Glad to hear that I unintentionally bought nice stable resistors. 🙂
I think most designers only run resistors at maximum 10% power dissipation to keep them from getting warm.
Very Interested! Thanks for the link! I will have a read through the article tomorrow when I have some time.
That explains some of the 1/2 watt notes I was seeing on my "cheapest" selection 🙂
🙂 Thanks for the info
That's interesting. I wonder if that is regulated by any standard for claims.
In PAs I use Chinese 1W 1% metal resistors bought in packs of 20-25 for each value saving enough money to use Caddocks in Zoebel and Dale low noise low inductance resistors where it makes sense and 5W low inductance in the ouput section. 2W if needed is made out of two 1W 1% Chinese resistors in parallel. Special resistor cases are very rare.
Luckily where I live there is no interference within a few km radius from anything except for residential neighbours and my audio room and home theatre are on separate 16A circuits.
cheers,
Luckily where I live there is no interference within a few km radius from anything except for residential neighbours and my audio room and home theatre are on separate 16A circuits.
cheers,
I've been using Newark's Multicomp house brand metal films for 20+ years for normal 1/4Watt needs. Out of curiosity I've checked resistance of some resistors I've had in service for 20 years. Still within 1%.
Anything larger is usually a little better grade. Anything in the output section is usually flameproof, especially Zobel resistor.
$0.145 is not cheap.
I pay £1.60 to £2.10 per hundred for 600mW 1% 100ppm/C metal film.
Cheap would be $0.01 to $0.02 each.
But, if those meet specification, then they are good and cheap.
The Canadian dollar is in the crapper, but that's the single unit price at Mouser US as well. Buy 1,000 at a time the price drops to $.018. Digikey has better pricing but a clunkier search engine.
I think Tim was referring to cheap in relation to other parts of his project, not necessarily that he had found the best value on resistors.
I think Tim was referring to cheap in relation to other parts of his project, not necessarily that he had found the best value on resistors.
Thanks for the tips guys!
This is what I meant 🙂
Also. My dad just told be he has a vast selection of "electronic bits and pieces" down to his house that I can have. Like thousands. Lol, will have to see what's there!