Harrison Ford Filter Feeler

[G-Sun]

Now, the question is:
Should I
1) Hard bypass the hicut, or
2) Should I mod R3, R4, R5 and R8 to compensate for the lack of 50k pots, using 3,4k-4k resistors? Will that take me in the right direction regarding cutoff-frequency?

 

[Marcocet]

Now, the question is:
Should I
1) Hard bypass the hicut, or
2) Should I mod R3, R4, R5 and R8 to compensate for the lack of 50k pots, using 3,4k-4k resistors? Will that take me in the right direction regarding cutoff-frequency?

Tough call.

Personally, I'd imagine that the throw of the filters is part of what causes people to talk about how good they sound. It's a very simple, practically low-fi design. As you awesomely demonstrated, when you take the unit out of bypass even with the filters all the way open you get a nice little presence and bottom boost. Good old loudness curves, subjectively better sounding.

 

[G-Sun]

As you awesomely demonstrated, when you take the unit out of bypass even with the filters all the way open you get a nice little presence and bottom boost. Good old loudness curves, subjectively better sounding.

You're right. I didn't notice the boost myself, but looking again it's there, both for hi and low.

 

[Marcocet]

I'm not trying to talk you out of modding the points Just saying that I've tried to look at it as a cool facet of the design rather than an imminent flaw. You should certainly be able to make them into cleaner sounding units if that's what you want them for. My first vote would definitely be going with an earlier thought in this thread and swapping out that TL074. That thing's kinda nasty.

 

[dandeurloo]

Is there a list of IC's that are good options for replacements?  I have a feeling a slightly newer op amp might have even more clarity and punch.

 

[G-Sun]

I'm not trying to talk you out of modding the points Just saying that I've tried to look at it as a cool facet of the design rather than an imminent flaw. You should certainly be able to make them into cleaner sounding units if that's what you want them for.

Well, Id really prefer to have one bypass for each filter, or a possibility to get them out of the way.
So, that's what I'm hoping for with the modding -adjust the cutoff max/min to be able to use one without the other.

 

[dandeurloo]

I just wanted to post about some knobs.  Marc found them and I ordered some to test and they work great.

They are from Selco and take a while to get but the fit is right for my panels and AML pots!  They also look very nice.

P/N: S111-004BLACK - Knobs
P/N: C110BLUE - End Cap
P/N: RED - End Cap


Hope that helps anyone who is looking.  Thanks Marc for the good find!

 

[Sleeper]

Is there a list of IC's that are good options for replacements?  I have a feeling a slightly newer op amp might have even more clarity and punch.

I had some THAT 1240 and THAT 1646 chips that I used on the front end, they drop in in place of  the INA and DRV chips.  I like those better for starters. 
I have one set that uses  OPA2604's on a little daugtherboard, because I had a 22 volt supply in that box.  they sound dandy.
I'm also liking TLE2072 (or maybe its 2074... they make duals and quads)  these sound great. also a pretty much straight drop in replacement for other chips.  these are great, they cost a couple of bucks.  worth it.

Hey I've got the strange weather boards.  They bench tested great, but somehow when I put them in to a case and wired em up they were still working.  Not when I started patching in from real gear though... I just opened this up and it looks like the input and output pins are if not mislabeled at least labelled in a strange way. grrrrrr  confusion.
gotta recheck my data sheets. 
resoldering now.

 

[Volume11]

Will these boards be available again in the near future, please? 

 

[dandeurloo]

They are now.  I have them and the cases in stock!

 

[minor_glitch]

Hey, do you guys think this supply from diypartssupply would be a good option for this project?
http://diypartssupply.com/index.php?main_page=product_info&cPath=2&products_id=34
Wonder if the big caps would fit in the 1u case...

 

[G-Sun]

Hey, do you guys think this supply from diypartssupply would be a good option for this project?
http://diypartssupply.com/index.php?main_page=product_info&cPath=2&products_id=34
Wonder if the big caps would fit in the 1u case...

Guess so.
How many units are you planning to have in one rack? Just the filters?

 

[minor_glitch]

Guess so.
How many units are you planning to have in one rack? Just the filters?

Yeah, just doing 8 filters in Dan's case.

 

[G-Sun]

Guess so.
How many units are you planning to have in one rack? Just the filters?

Yeah, just doing 8 filters in Dan's case.

http://wiki.nimbleswitch.com/Currrent_Draw

Ok, so that's 8 x 20 mA = 160mA

 

[straypacket]

So, noob question - single rail, or dual rail PSU? 

I am assuming single, since 15volts is the only rating specified in this thread...

 

[G-Sun]

So, noob question - single rail, or dual rail PSU? 

I am assuming single, since 15volts is the only rating specified in this thread...

Dual

 

[straypacket]

Thanks G-Sun.  Do you know of a concise, noob-oriented explanation of n-rail power supplies as they apply to our DIY audio world?

 

[dandeurloo]

Hey Guys I am gonna do another run of these cases.  So I should have more in stock in a few weeks.

Thanks

 

[G-Sun]

Thanks G-Sun.  Do you know of a concise, noob-oriented explanation of n-rail power supplies as they apply to our DIY audio world?

I use JLM AC/DC kit a lot (3 rails)
http://www.jlmaudio.com/shop/index.php?_a=viewCat&catId=6
But I've seen some good other suppliers as well.

 

[straypacket]

Thanks again - I will check out JLM.

Another question - this time regarding applicable dual-gang potentiometers.  The pots on the AML site would be prohibitively expensive, due to overseas shipping.

Would the following part, available at Mouser be an acceptable substitute?

http://www.mouser.com/ProductDetail/Alpha-Taiwan/RV122F-20-15F-A50K/?qs=sGAEpiMZZMtC25l1F4XBU1Dxzr6mc3JGVMfH0qeg68U%3d

Also - the BOM calls for 50k linear - but the recommended AML pot is marked as reverse log - are these interchangeable?

Finally, I just put in my order for the case+pcbs, so maybe I'll have some build pics soon... I still have to finish my GSSL though (kicking myself for not seeing the SB4000 first).