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I'm noticing many different stances on the values/types of parts used within the amp section of the gainclone.1) I noticed in the beginning of Thorsten's posts that he suggested 4.7uF blackgate non-polarized. Now it seems like 2.2uF mylar? What about voltage rating? Not quite sure what's the case here.
2) Bypassing the resistor (220K?) connected to the positive input terminal of the opamp is a .1uF cap? Of what type? Does this value also vary? What about voltage rating?
3) Concerning the zobel: Is everyone calculating different values for their zobel network? I see a schematic on the gainclone discussion board that has a zobel network with values of 1 ohm and .22uF...from the very very little I know about zobels from attempting to understand posts here on them, shouldn't the resistor value be approximately 1.25 times the DCR of the speaker? Am I missing something here? surely the person doesn't have a .8 ohm speaker. I'm totally clueless on the zobel aspect here. Also, was a concensus reached on what type of cap to use for the zobel? Going polypro. and compromising signal length or using smaller sized caps? Again, voltage rating would be appreciated.
Please do not refer me generally to the gainclone discussion board, I've already been there and read every post. Now if you are going to direct me to a specific post where I may have missed some key info, that's fine. I really would like to get the ball rolling on this project but can't exactly do that without knowing the parts necessary to order. I have read cfraser's gainclone page, but wanted to know if there's any disagreement with the suggested parts listed.
I greatly appreciate it!
Andy
Follow Ups:
nt
Hi,> 1) I noticed in the beginning of Thorsten's posts that he suggested
> 4.7uF blackgate non-polarized. Now it seems like 2.2uF mylar?Well, people complained about cost and availability of BG's. Different capacitors sound different. Choose your poison.
> What about voltage rating?
Anything really, there should be no DC. If you want to be super safe in case the Amp fails use a Voltage above the maximum PSU Rail Voltage.
> 2) Bypassing the resistor (220K?) connected to the positive input
> terminal of the opamp is a .1uF cap? Of what type?Whatever sounds best to you.
Now I personally would not use any input coupling cap, use a much lower gain and arrange a lot of things different. My suggestions for the "inverting mode" gainclone included a maximum amount of "safety" so it would be reliable to make for inexperienced DIY'ers. Much freakier designs sound better but may misbehave, worst case while blowing up the speakers they are connected to!!!!
> 3) Concerning the zobel: Is everyone calculating different values
> for their zobel network?Probably. I usually leave them off on the Amp and just use a suitable series resistor. I treat Zobels and series inductors etc more components that should be integrated with the speaker cable than be part of the Amp.
The classic Zobel that works well is 10 Ohm & 0.1uF.
> Also, was a concensus reached on what type of cap to use for
> the zobel? Going polypro. and compromising signal length or
> using smaller sized caps?Small size matters more, mylar is fine.
Later T
Since I was working on my gainclone power supply today, I'm in the gainclone mood. BTW, this is a very sonically significant area in which to spend some effort, JIC I didn't mention it in the webpage...I can't really help you with the Zobel, and frankly, I haven't noticed much difference when playing around with it, but YMMV. Even leaving the Zobel out works just fine with my speakers and short cables. I'm still leaving it in though, with the smallest lead distance polyprop I could find.
I hope I really didn't convey the impression that I was recommending specific parts. What I really wanted was for people to e-mail me the parts they actually used with a note re the sound. This hasn't happened, but I realise this is pretty normal. Much easier to post to a discussion forum, but I was hoping to collect lots of info so people could pick and choose from what's been tried, and have an idea of what to expect.
The "problem" with a gainclone is that practically anything will work, from a functional POV, though the sound may not be great. The chips are extremely forgiving as long as PS voltages are within spec. However, I still recommend following the 47 Labs philosophy, to again take advantage of known results as much as possible.
** Keep the parts count low and the electronic distances short **
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