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How does my Dynalo BOM look?

post #1 of 7
9/15/10 at 1:07pm
Thread Starter 

I'm hoping someone could take a quick look over these two orders that I'm about to place on Mouser/Farnell. These are the last of the parts I need and I had to make some substitutions with the caps and LEDs - just seeking some reassurance that everything looks within spec when compared with the BOM on djgardner's site. Of course if you have any suggestions I'd be happy to hear them.

 

Mouser Basket

 

Farnell Basket

 

Ps. The part quantities don't match up since I'm buying to build two boards and in some cases I've added surplus for matching.

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post #2 of 7
9/15/10 at 2:08pm

As discussed in the other thread, biasing works better to swap the 499ohm biasing resistors out for 620 or 650 ohm. I would add 8 620ohm to see which value wroks better.

 

What gain are you setting each board up for ?


Edited by bada bing - 9/15/10 at 2:17pm
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post #3 of 7
9/15/10 at 3:16pm
Thread Starter 

Good catch. I forgot to add those extra resistors to the order - I plan to use 620ohm type Dales as you say.

 

In terms of gain, I'll be driving 650s so I wanted a fairly high value. Since the default is 11 I plan to use 2K resistors with the 10K resistors from the original BOM to obtain (10 / 2) + 1 = 6 which I gather is effectively 12 in balanced drive.

 

Thanks to you personally for your help in all the threads I've posted on this topic. 

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post #4 of 7
9/15/10 at 9:28pm

Curious as to why you went with RN60C 0.1% resistors for some, but not all? 7.5K, 1K, 3.32K. These are all used in the biasing network for the VAS stage, and should require as much attention as the others? If I recall your previous thread(s), you were asking if it were better to pay for 0.1% or buy 1% in a greater qty and match? Also, for the servo opamps, OPA134s are somewhat overkill. I've always used TL071s (and headamp used these as well at least for awhile). You don't need an audio opamp here. Also the cap for the servos... not sure I would use the ceramic you have selected. Mouser carries the normal Panasonic stacked film cap: 667-ECQ-V1H334JL

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post #5 of 7
9/16/10 at 2:15am
Thread Starter 

Unfortunately they don't look to have any stock in until mid-November (here in the UK at least), any alternatives that you could suggest? How about this Kemet cap (1457709 on Farnell)?

 

Thanks for the suggestions.
 

Quote:
Originally Posted by Pars View Post

Also the cap for the servos... not sure I would use the ceramic you have selected. Mouser carries the normal Panasonic stacked film cap: 667-ECQ-V1H334JL

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post #6 of 7
9/16/10 at 10:40am

They do have the 0.27uf version in stock (ECQ-V1J274JM) This will shorten the integrator time constant slightly, but shouldn't have any detrimental effects.

 

Or how about this one from Farnell...1744830

 

EDIT: wrong value on 1st link


Edited by Pars - 9/16/10 at 2:56pm
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post #7 of 7
9/18/10 at 10:47am
Thread Starter 
Okay, I placed the order today for the Dynalo parts, a Sigma22 power supply and Epsilon12 board. In the end I followed Pars' recommendation for the servo cap, upped the biasing resistors to 620ohm and decided to use 0.1% resistors all round (a mix of same-spec Dales and Holcos) because, well, it can't hurt.



The PCBs came through from AMB today so I can start sizing a case design and pestering the university for access to the electronics lab and engineering rooms! Thanks for your input all.
Edited by Bizzel - 9/18/10 at 10:49am
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