Not sure which board design you are working with - but here are the original NP and I think the latest Prasi board schematic. Also is a BOM, not exactly spec'd to either board, but easy enough to change the small/medium transistors to those listed on either schematic. Note that the original NP schematic has R3 as 100r, which sets the gain at ~60, pretty high. I have tried 475r, 750r and 1k which set the gain at 46, 29 and 22. In the end I picked 750r, since that's the gain on most of my other amps and pairs well with my Preamp.
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Any serious deviations from what Prazi posted in the PDF above? I am about to start building (finally) my AB100....
I don't see any huge issues - you will need (2) of the 1N5404 (your list only has 1 in quantity, but any 3-4A diode will work, I chose the cheapest and works fine.
I preferred to go off the actual schematic, because those transistors I had on hand (MJE340 (Q5), MJE350 (Q6), KSC3503, KSA1381, BC547, BC557). I just printed out the schematic and went through and made the order on Mouser and crossed them off as I put them in my cart, or pulled from my stash.
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Just double checking all my parts and noticed various opinions on what R3 should be.
I have 1K for R3 and 10R for R35 as per the Prasi schematic?
Will this be alright?
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You should have no issues using 1k, I am personally used both and settled on 750r, but honestly didn’t hear any difference with either gain setting so I left it with 750r.
What difference would any of these make as the 1R emitter resistor?
The KOA Speer BPR58CF1R0J Current Sense Resistors - Through Hole 1 Ohm 5W 5% 350ppm and Vishay / Dale CPF31R0000DKB14 Metal Film Resistors - Through Hole 3watts 1ohms 0.5% have been suggested, but I don't have either.
I have the Ohmite Wirewound Resistors - Through Hole 5W 1 ohm 1% already.
Thank you,
David.
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To avoid an additional order, I would try the Ohmmits you have on hand. NP also said earlier anything from 0.33 - 1r emitter resistors is fine - if you have a MOX resistor of those values on hand. I used metal oxide 0.47r 3 watt
I use the cheaper option linked all the time and haven’t had any issues.
I use the cheaper option linked all the time and haven’t had any issues.
@bullittstang
Does resistor composition (Wirewound vs. Metal Film vs. Metal Oxide vs. Current Sense Resistors) matter?
Or how close should they be matched, 1% vs. 5% vs. something else?
Does resistor composition (Wirewound vs. Metal Film vs. Metal Oxide vs. Current Sense Resistors) matter?
Or how close should they be matched, 1% vs. 5% vs. something else?
I think it depends on the stability of the amplifier design. Metal oxide tends to be pretty stable, with reasonable cost. Metal film is likely the more stable, however at a much higher price. Wire-wound is the cheapest, but again for most designs is perfectly fine, may have more heat drift of the value.
5% or less is fine, no matching needed.
5% or less is fine, no matching needed.
If you are using Prasi designed boards 10r is correct, he changed R35 to be part of the output network for any potential oscillation.
