khstudio

LA2A - Removing UnNeeded Parts???
« on: January 08, 2008, 09:40:25 AM »
I'm building a 2nd LA2A & NEVER used the STEREO ADJUST/R3 & LIMITER RESPONSE/R37 on my 1st one... they are always set FULL to one side.

I have no plans on linking 2 units together & want to know which parts can be removed, like the STEREO ADJUST/R3 & LIMITER RESPONSE/R37 + Any surrounding components that can be safely removed.

I read about this in the past but could not find the posts... CJ was one I remember mentioning unneeded parts.

Could someone shed some light on this for me? Please  :green:

The pots are 1meg but it doesn't look like I can just remove them & install 1meg Resistors.

Thanks
Kevin ~ KHStudio


CJ

LA2A - Removing UnNeeded Parts???
« Reply #1 on: January 08, 2008, 05:34:37 PM »
I am supposed to write that up and giving to Kev, who was unfortunately dispatched by a great white while snorkeling the barrier reef.
My full condolences to the Kev family and friends, he really did a lot for the DIY community.

The schematic for the strip down is in that monster LA2 thread somewhere.

Use octals, 6 or 12SN7, for a superior sounding product.
The Jensen mod to the output stage does very little, so that can stay stock.

I can dredge it up this evening if you can hang. And Kev is probably still alive, I was just trying to stir his ass out of bed, and into the DIY shed.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

khstudio

LA2A - Removing UnNeeded Parts???
« Reply #2 on: January 08, 2008, 07:49:06 PM »
I can hang... thanks man  :thumb:
...don't need this extra pot crap on the back for stereo adj.

I wasn't going to drift too far from stock, like changing tubes to 6 or 12SN7... although I LOVE those... & the 6sL7.

I was planning on setting it up like my first build:
Jensen Mod + 10K:600 out (Edcor XSM)
10k:10k in (Edcor XSM)
+ Change first tube to 12aY7.
.. I love the sound of that when I tried it in my 1st build.
Kevin ~ KHStudio

gary o

LA2A - Removing UnNeeded Parts???
« Reply #3 on: January 08, 2008, 07:49:17 PM »
Sorry tbut in but just a quicky CJ id like to do the 12SN7 thingy is there schematic anywhere cheers fellas


Gary O.

okgb

LA2A - Removing UnNeeded Parts???
« Reply #4 on: January 08, 2008, 07:58:07 PM »
He was a good guy , did allot for the comunity ,
remember the NEQ ?
GKB Audio / Greg Boboski

khstudio

LA2A - Removing UnNeeded Parts???
« Reply #5 on: January 08, 2008, 08:32:43 PM »
Quote from: "okgb"
He was a good guy , did allot for the comunity ,
remember the NEQ ?


Hey, thanks for the nice comments. :green:

...but I think he's talking about the other KEV.  :wink:
Kevin ~ KHStudio

CJ

LA2A - Removing UnNeeded Parts???
« Reply #6 on: January 08, 2008, 09:29:29 PM »
Let me get my website going, IPower Web switched platforms on me and moved all my stuff, now I can't link pics.

I tried to call the help line but it burne 60 minutes off my T Mobile, I love companies that make 10 million then hire two guys for support.
 :green:
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

LA2A - Removing UnNeeded Parts???
« Reply #7 on: January 08, 2008, 09:41:22 PM »
Hmm, seems to be working now after an "enable_ulr" was hacked in by yours truly.

Here is what a full octal chassis looks like, you can use the 6V6 for the 6BQ5 as they are the same tube, different package.

Round T4 can can never be crooked.

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

gary o

LA2A - Removing UnNeeded Parts???
« Reply #8 on: January 08, 2008, 10:04:04 PM »
Cool that looks great ..I like the sound of the 12AY7 too..

Can I just sub the 12SN7 ,,,once I solder in a octal socket that is ...do I need to change any component values.

PS cj I no you like to mess what cap do you have to op tran ..I have really big poly prop as big as yr t4b ..it sounds bigger.

Many many thanks

CJ

LA2A - Removing UnNeeded Parts???
« Reply #9 on: January 08, 2008, 10:13:47 PM »
Yeah, Bluebird scored these huge polys from Apex, weird, thay had two leadfs for the same foil, a foulr lead cap, mechanical I guess.

Here is a circuit with a bunch of mods, XLR jacks, 100 K plate resistors for less harshness, R3 Lim and Stereo pots removed, the 1 Meg on the EL driver is it's replacement, a gnd lift, never wired this, so buyer beware, but no big if one wire is off, unless it explodes, which is unlikely unless you are me.
I think I had an XLR polarity issue by yhe pic title, so if anything is amiss, it be the XLT polarity.

http://vacuumbrain.com/The_Lab/LA2/LA2B_XLR_flip.jpg
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


khstudio

LA2A - Removing UnNeeded Parts???
« Reply #10 on: January 09, 2008, 01:03:40 AM »
Cool man.

I've been chewin on it for a little while & have a few observations/Questions:

C12 = .001 looks to be redundant since it normally goes across the 1meg (R37) which is normally shorted out which would short out that cap as well.
So in other words, not needed.
On your schematic, it's dead up in the signal path. Theres already a .02 coupling cap.

The ARCO (C14) is missing across (R30) 47k.
It's been a long time since I built my 1st LA2A so I don't remember exactly but I found that this cap DOES affect the frequency response (I think when compressing) even though the pots are fully clockwise.

R37 (Limiter Response) does look like it can be completely removed like you have it.
Kevin ~ KHStudio

khstudio

LA2A - Removing UnNeeded Parts???
« Reply #11 on: January 09, 2008, 01:48:15 AM »
I whipped this up. Let me know if you see any errors.

Kevin ~ KHStudio

CJ

LA2A - Removing UnNeeded Parts???
« Reply #12 on: January 09, 2008, 02:18:49 PM »
cool, i will splice that in.

the 12sn7 might need a different plate resistor, i think thats where i left off on this project, and maybe a diferent cathode resistor, but go for the 6012 and you do not have to F with it, just usee 100 k plate r.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Cainester

LA2A - Removing UnNeeded Parts???
« Reply #13 on: January 09, 2008, 10:59:35 PM »
sorry to go OT,
but did something happen to Kev?

CJ

LA2A - Removing UnNeeded Parts???
« Reply #14 on: January 10, 2008, 01:15:38 AM »
no, we are (me) just spreading rumors to see if he takes the bait,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

cannikin

LA2A - Removing UnNeeded Parts???
« Reply #15 on: January 10, 2008, 04:20:59 AM »
Quote from: "CJ"
no, we are (me) just spreading rumors to see if he takes the bait,


well you had me on the hook,  I was about to do a search in the Brewery for the scoop on Kev.

Thanks god its a hoax, and damn you CJ - I'm a sucker!!  :?

Anyway, the one that I really want to remove is that damn switch!  
tried a DPDT but I messed it up....  have to revisit that one
Tube limiters..yum!

CJ

LA2A - Removing UnNeeded Parts???
« Reply #16 on: January 10, 2008, 04:45:16 AM »
I hate that switch!

Why not hard wire the VU onto the output xfmr?
No way to mess that up.
Plus, who says "I think I am going to compress the guitar part 3.5 db."

No way, you don't even want to look at the meter, it will prejudice your ears.
Turn the knob and look away, right?
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Kid Squid

LA2A - Removing UnNeeded Parts???
« Reply #17 on: January 10, 2008, 05:43:45 AM »
Hiya Chaps,

Done away with the Stereo link facility on mine, I'll try to find the drawing of what i done - don't think it was rocket science  :wink:
CJ - going to be all octal on the next one  :grin:
any T4B's hanging around..........

Regards,
Steve :thumb:
It is not the same as 4+12, nor is it the same as 4+8, but 4+12 IS the same as 4+8+12....

http://www.facebook.com/LazyLizardLabs

khstudio

LA2A - Removing UnNeeded Parts???
« Reply #18 on: January 10, 2008, 08:44:47 AM »
Quote from: "cannikin"


Anyway, the one that I really want to remove is that damn switch!  
tried a DPDT but I messed it up....  have to revisit that one


Good point... I remember wiring that switch on my first 2 point to point LA2A's & didn't like it either.
The +10 is just useless.

DPDT should work... I'm using the DRIP LA2A PCB this time & he has it set up for a DPDT. (Very nice PCB by the way)
Reading this post made me realize  I don't have to deal with that switch this time. :green:
Kevin ~ KHStudio

okgb

LA2A - Removing UnNeeded Parts???
« Reply #19 on: January 10, 2008, 08:57:49 AM »
Hey Kev , i don't want to go there but shouldn't you wait til easter ????
oh wait maybe thats PRR

 What xfmrs & optical are you using [ that is available these days ]
GKB Audio / Greg Boboski


 

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