Harry3,
Can you mark up the schematic with what you are proposing?
Do you mean make R13 2k2 and get rid of the 100R? The 2k2 acts with C4 as a filter, whereas the 100R is a gate stopper, which probably isn't needed as the 2k2 is already there. However, it matters where the node to the filter cap is located. I think you can leave R13 where it is but ok to get rid of the 100R at R4.
Can you mark up the schematic with what you are proposing?
Do you mean make R13 2k2 and get rid of the 100R? The 2k2 acts with C4 as a filter, whereas the 100R is a gate stopper, which probably isn't needed as the 2k2 is already there. However, it matters where the node to the filter cap is located. I think you can leave R13 where it is but ok to get rid of the 100R at R4.
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Hi Hallcon,
I just checked and it looks like I totally messed up and just forgot to send your order. Let me help make this up to you... I will throw in a free Desktop SE Class A (DCA) amp PCB for your troubles. I will send it out tomorrow via priority mail.
Cheers,
X
I just checked and it looks like I totally messed up and just forgot to send your order. Let me help make this up to you... I will throw in a free Desktop SE Class A (DCA) amp PCB for your troubles. I will send it out tomorrow via priority mail.
Cheers,
X
2. For the main MOSFET Drain resistors R117/118 and R137/138, please use high quality metal thin film as well. I only had thick film on hand, so once again, you may see significant improvement in distortion over my verification build if you choose this. I would start with the 2R7 values to get 115mA. If you really want 145mA then use 2R2 and that will be the maximum capability of the Traco Dc-DC (315mA for both channels).
X - found an inconsistency.
Thin or thick film for these ones (R117/118 and R137/138)? BOM lists thick for these (and that's what I ended up ordering), but you advise thin in the quoted post.
Thanks
IMO - thin film resistors are generally the best you can get. They are stable, tight tolerance, low PPM, non magnetic and are made of good quality raw material etc etc...
Some people like carbon resistors because they have their own "signature" sound.
You choose your poison
Some people like carbon resistors because they have their own "signature" sound.
You choose your poison
On the feedback resistors (R16/107) and MOSFET source/drain power resistors (R115/116/117/118) especially, use either carbon film or metal thin film. If you use metal oxide thick film here, it tends to generate the unpleasant third order harmonic distortion. I have measured it and it is not insignificant. But only in places where there is a significant amount of AC-signal current induced heating. Some people argue that gate stoppers (R113/114) for MOSFETs should be carbon as well.
To be safe, use all metal thin film if you want. It will cost a bit more but will be safe and low distortion. The carbon thin film on the key feedback and ground shunt resistors will have a smoother ("less etchy metallic") sound.
To be safe, use all metal thin film if you want. It will cost a bit more but will be safe and low distortion. The carbon thin film on the key feedback and ground shunt resistors will have a smoother ("less etchy metallic") sound.
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ahh gotcha - thanks X thanks Harry3!
Guess I'll be ordering some thin film / MELF 2R7 & 180R carbon resistors to muck about with.
2R7 backordered @ RS until March, so I guess I'll have it running on the thick film until then, carbon TH available for next business day delivery
Guess I'll be ordering some thin film / MELF 2R7 & 180R carbon resistors to muck about with.
2R7 backordered @ RS until March, so I guess I'll have it running on the thick film until then, carbon TH available for next business day delivery
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