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Thomas white LPGc questions
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Author Thomas white LPGc questions
fonik
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PostPosted: Sat Feb 25, 2012 4:27 pm    Post subject: Reply with quote Add User to Ignore List

a while ago i tried feeding back the summed out to the input. the result was a very harsh resonance, very noisy. maybe i should try inverting it? or as you said: just using a single out...
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Ianh
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PostPosted: Sat Feb 25, 2012 6:42 pm    Post subject: Reply with quote Add User to Ignore List

fonik wrote:

i am not sure if you wanted to use a linear or an log VCA. i did not have the time to test this in depth...

I suppose alot of the fun of using an external vca would to have both options. Thanks again! Im very excited about this.
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astroschnautzer
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PostPosted: Mon Feb 27, 2012 10:43 am    Post subject: Reply with quote Add User to Ignore List

fonik wrote:
a while ago i tried feeding back the summed out to the input. the result was a very harsh resonance, very noisy. maybe i should try inverting it? or as you said: just using a single out...
Ok, would you want to try it? I havent't got mine panelized yet and would like to implement resonance to my panel if it works...
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fonik
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PostPosted: Mon Feb 27, 2012 4:19 pm    Post subject: Reply with quote Add User to Ignore List

astroschnautzer wrote:
fonik wrote:
a while ago i tried feeding back the summed out to the input. the result was a very harsh resonance, very noisy. maybe i should try inverting it? or as you said: just using a single out...
Ok, would you want to try it? I havent't got mine panelized yet and would like to implement resonance to my panel if it works...

i tried it with the sum out, at least. inverted does not do much. non-inverted it does too much. it sounds a little bit like frequency modulation (ring mod), depending on the settings. depending on the frequency of the incoming signal there is only a very small range of feedback that sounds like resonance. very easily you get these hardsyncing/ringmod sound. interesting, alas, not what we want.
ATM i cannot try single outs. would have to open up the cabinet and all, which i don't have the time to these days.

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astroschnautzer
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PostPosted: Mon Feb 27, 2012 4:50 pm    Post subject: Reply with quote Add User to Ignore List

fonik wrote:
astroschnautzer wrote:
fonik wrote:
a while ago i tried feeding back the summed out to the input. the result was a very harsh resonance, very noisy. maybe i should try inverting it? or as you said: just using a single out...
Ok, would you want to try it? I havent't got mine panelized yet and would like to implement resonance to my panel if it works...

i tried it with the sum out, at least. inverted does not do much. non-inverted it does too much. it sounds a little bit like frequency modulation (ring mod), depending on the settings. depending on the frequency of the incoming signal there is only a very small range of feedback that sounds like resonance. very easily you get these hardsyncing/ringmod sound. interesting, alas, not what we want.
ATM i cannot try single outs. would have to open up the cabinet and all, which i don't have the time to these days.
Ok, I will try the individual outs and see what happens, I so much would love to have this function...
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fonik
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PostPosted: Mon Feb 27, 2012 5:10 pm    Post subject: Reply with quote Add User to Ignore List

astroschnautzer: check PM!

(we are very off topic right now)

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nihilist
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PostPosted: Mon Feb 27, 2012 5:14 pm    Post subject: Reply with quote Add User to Ignore List

Not sure if anyone else has experienced this.
BUT
I built a dual LPG and it was working fine,
then last week the output level has "sharply" decreased
and is giving off a hum, due to not being grounded.

SO, I am not sure why it was working just fine,
and isn't now...

Anyone?

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bsmith
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PostPosted: Wed Mar 07, 2012 6:43 pm    Post subject: Reply with quote Add User to Ignore List

Newb diy'er confused trying to order shit alert!
Ordered a couple boards and I'm going to build some other things before I get to these but I'm trying to build a project in mouser for parts - a few things are challenging me..
Going by the list with part #'s specified in DJ Thomas' bundle of docs there are these polystyrene caps that are obsolete, and all similar rated polystyrene film caps are as well. Specifically:
Polyester Film Capacitors 250volts .1uF
and
Polyester Film Capacitors 63V 1.0uf
and then also this resistor:
Carbon Film Resistors - Through Hole 4.7Mohms which is backordered 14 weeks out.
Can anyone recommend parts that would work or a way to approach this?
Sorry if these are dumb/easy questions - just getting going with this stuff.

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jumunius
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PostPosted: Wed Mar 07, 2012 7:52 pm    Post subject: Reply with quote Add User to Ignore List

bsmith wrote:

Going by the list with part #'s specified in DJ Thomas' bundle of docs there are these polystyrene caps that are obsolete


I think you mean polyester. At least the ones you call out as being obsolete are polyester.

For Polyester Film Capacitors 250volts .1uF try this one. (Note that the voltage rating seems unnecessarily high, but that's not necessarily bad, so I matched it.)

For Polyester Film Capacitors 63V 1.0uf try this one.

And for this one, Carbon Film Resistors - Through Hole 4.7Mohms, try this one.

Quote:
Can anyone recommend parts that would work or a way to approach this?
Sorry if these are dumb/easy questions - just getting going with this stuff.


No problem, we all gotta start somewhere. As for a way to approach this, next time you run into this problem, use the "Show Similar" feature. To do this, look at any of the links you posted, then look at the spec list that is posted at that page. Uncheck the manufacturer (AVX, Xicon, etc), and then check off all the important specs (you'll learn this over timeO. For a cap I'd keep Product Category, Capacitance, Termination Style and if it's there, Lead Spacing at least. I might leave voltage unchecked to give myself more options. (You can use a higher voltage rating if you can't find a good choice in the spec'd voltage.) Then click "show similar" and check your results. You can further refine your search results with other filters, including lead spacing.

And I hate to say it, but in some ways, the best way to learn how to order parts from Mouser is to make some mistakes. If you plan on sticking with DIY, plan on that, and figure there will ALWAYS be another order to make.
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negativspace
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PostPosted: Wed Mar 07, 2012 8:19 pm    Post subject: Reply with quote Add User to Ignore List

You can also shift-click in the Mouser category lists to select multiple categories for a search - so click 35v, 50v and 63v + 1.0uF with polyester caps for example. From there click on 5mm lead spacing + radial and see what you have left.
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bleeps
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PostPosted: Wed Mar 07, 2012 8:33 pm    Post subject: Reply with quote Add User to Ignore List

Hitching a ride on bismith's question: Does a specified lead spacing affect anything other than fitting into a particular PCB layout? In other words, is it okay to sub something with a different spacing if that's what you have on hand provided all other specs are compatible?
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bsmith
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PostPosted: Wed Mar 07, 2012 8:34 pm    Post subject: Reply with quote Add User to Ignore List

Thanks so much guys - this is a project that's quite a ways off, have a bunch of other very cool things closer to the level I should be working on to make my way up to these - wanted to at least get the boards in case they became unobtainable. Thanks for the mouser hunt tips - sometimes it kind of seems to present me with an easy way to get related parts and sometimes not - or something.
I don't know where the hell I pulled 'polystyrene' from!

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gwaidan
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PostPosted: Wed Mar 07, 2012 8:54 pm    Post subject: Reply with quote Add User to Ignore List

bleeps wrote:
Hitching a ride on bismith's question: Does a specified lead spacing affect anything other than fitting into a particular PCB layout? In other words, is it okay to sub something with a different spacing if that's what you have on hand provided all other specs are compatible?


As long as they physically fit into the board that's all that matters

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lordofthebored wrote:
Any news on this yet? I just sold all my other modules of this type so I could replace it with this different implementation of the same thing!
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jumunius
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PostPosted: Wed Mar 07, 2012 11:47 pm    Post subject: Reply with quote Add User to Ignore List

gwaidan wrote:
As long as they physically fit into the board that's all that matters


True. Although one can be a bit too cavalier about this as well. On one of my first projects I accidentally ordered a handful of 1/2w resistors and various ill-fitting caps. I learned a lot of lessons the hard way there:

1) if you have an oversized resistor in a tightly packed row of resistors, you will either mount it above or below the other resistors, which means that if you have to desolder anything for troubleshooting/modding you may have to desolder neighboring components as well.

2) a 10mm or 2.5mm polyfilm cap might fit a 5mm space on your board well enough, but it's leads might be too small to reach easily, which can lead to soldering problems. (You can often just solder a clipped resistor lead to one of the legs of course, but that can be dodgy too.)

3) sometimes an oversized component will also have oversized leads (as in, too thick a gauge!). So then maybe you have to drill out your PCB's holes, which is especially dodgy.
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cleaninglady
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PostPosted: Sat Mar 10, 2012 7:46 am    Post subject: Reply with quote Add User to Ignore List

jumunius wrote:
bsmith wrote:

Going by the list with part #'s specified in DJ Thomas' bundle of docs there are these polystyrene caps that are obsolete


I think you mean polyester. At least the ones you call out as being obsolete are polyester.

For Polyester Film Capacitors 250volts .1uF try this one. (Note that the voltage rating seems unnecessarily high, but that's not necessarily bad, so I matched it.)

For Polyester Film Capacitors 63V 1.0uf try this one.

And for this one, Carbon Film Resistors - Through Hole 4.7Mohms, try this one.

Quote:
Can anyone recommend parts that would work or a way to approach this?
Sorry if these are dumb/easy questions - just getting going with this stuff.


No problem, we all gotta start somewhere. As for a way to approach this, next time you run into this problem, use the "Show Similar" feature. To do this, look at any of the links you posted, then look at the spec list that is posted at that page. Uncheck the manufacturer (AVX, Xicon, etc), and then check off all the important specs (you'll learn this over timeO. For a cap I'd keep Product Category, Capacitance, Termination Style and if it's there, Lead Spacing at least. I might leave voltage unchecked to give myself more options. (You can use a higher voltage rating if you can't find a good choice in the spec'd voltage.) Then click "show similar" and check your results. You can further refine your search results with other filters, including lead spacing.

And I hate to say it, but in some ways, the best way to learn how to order parts from Mouser is to make some mistakes. If you plan on sticking with DIY, plan on that, and figure there will ALWAYS be another order to make.


I just emailed Thomas and also David Brown the other day about these High Spec capacitors ; both of them said it was going to make very little difference. I was going to buy them but after speaking to these guys , I just used Ceramic caps for everything apart from Electro's.

In regards to the Carbon Film 4.7M Resistor ; i just used a 4.7M Metal Film .5W.

Is there a discernable difference anyone can point out in this case ?

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Last edited by cleaninglady on Sat Mar 10, 2012 9:10 am; edited 1 time in total
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e-grad
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PostPosted: Sat Mar 10, 2012 8:06 am    Post subject: Reply with quote Add User to Ignore List

cleaninglady wrote:
I regards to the Carbon Film 4.7M Resistor ; i just used a 4.7M Metal Film .5W.

Is there a discernable difference anyone can point out in this case ?


You just have used a higher quality resistor [hence the difference in price hihi ].

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cleaninglady
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PostPosted: Sat Mar 10, 2012 9:15 am    Post subject: Reply with quote Add User to Ignore List

e-grad wrote:
cleaninglady wrote:
I regards to the Carbon Film 4.7M Resistor ; i just used a 4.7M Metal Film .5W.

Is there a discernable difference anyone can point out in this case ?


You just have used a higher quality resistor [hence the difference in price hihi ].


Yeah i know , it's what i had on hand.

But sound difference ? Anyone ?

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e-grad
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PostPosted: Sat Mar 10, 2012 9:42 am    Post subject: Reply with quote Add User to Ignore List

cleaninglady wrote:
But sound difference ?


None.

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PostPosted: Sat Mar 10, 2012 10:38 am    Post subject: Reply with quote Add User to Ignore List

cleaninglady wrote:
I just emailed Thomas and also David Brown the other day about these High Spec capacitors ; both of them said it was going to make very little difference. I was going to buy them but after speaking to these guys , I just used Ceramic caps for everything apart from Electro's.


While I'd generally recommend taking the advice of David Brown and Thomas White over anything I say, are you sure you understood them correctly? My understanding is that you can use C0G or NP0 rated capacitors in place of film, but not true with just any ceramic capacitor. And for values like 1uf, I don't even find a C0G/NP0 at that capacitance... these are usually available for smaller values. I'm not even sure you'd save much money if you are buying C0G/NP0 as compared to standard film caps. (And you can probably shop around and get cheaper film caps, I just pick WIMA reflexively since there are so many options out there and I know WIMA are decent quality.) The big savings comes when compared to polystyrenes etc.

Now in the case of the .1uf caps, those are just decoupling caps, and ceramic is a great choice there (and I don't think temperature rating is so critical there). I was just matching to the specs of Thomas' BOM.

Even David Brown uses several film capacitors throughout his build. He does use ceramics for decoupling, of course.

Quote:
In regards to the Carbon Film 4.7M Resistor ; i just used a 4.7M Metal Film .5W.

Is there a discernable difference anyone can point out in this case ?


Yes, physical size! But if it fits, then no worries.
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