altec 1678c mod..direct out/gain control..AUDIO SAMPLES!

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the finger genius
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Post by the finger genius » Tue Oct 06, 2009 6:47 am

Gabe, Rod, or Pogo, I don't suppose you might have a parts list / ordering info? I'm extremely new to this, and I'm hoping to avoid ordering things which won't fit.
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the finger genius
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Post by the finger genius » Tue Oct 06, 2009 4:44 pm

After going through the original thread, I was thinking of ordering these. Any feedback?

http://search.digikey.com/scripts/DkSea ... =CT2239-ND
vvv wrote:
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You may quote me.
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gabe real
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Post by gabe real » Wed Oct 07, 2009 1:10 am

hello, i think 25k pots wont get you the input adjustment your looking for.
i used 1k pots due to the pot replacing a .5k resistor.
i was advised about this by RodC too.

i just went down to the local electronics supply and dug around
till i found something. i had to drill the holes bigger but no big deal.
the faceplate is pretty thin, its more of a decorative thing.

try to look for 1k pots on digikey.
they have a online chat help center.
ebay has some stuff too.

hope this helped.

pogomuse - cool, i might try that out.

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the finger genius
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Post by the finger genius » Wed Oct 07, 2009 4:27 am

Cool thanks a lot for the info. And thanks for the inspiration, I've wanted to do something like this forever, this post (along with Rod's) and especially all the pictures made me feel like I can do it. So is it ok to just use the 6mm shaft diameter pots, since you had to drill anyway?
vvv wrote:
That said, what I'm gettin' at is, perfectionism is for the truly defective.

You may quote me.
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gabe real
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Post by gabe real » Wed Oct 07, 2009 10:16 am

yeah, that should be fine. you can always measure the whole and get the right size.
you are going to have the hardest time with the thread size, not the shaft size.
so dont get too stressed out on the diameter. it took maybe 10 minutes to drill
all 8 wholes with a hand drill.

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1678 mod newby question!

Post by blessu123 » Sun Aug 15, 2010 6:25 am

Hey guys, awesome post!
I have a green 1678 not a,b,c. Does anyone know if I can do the same mod. I love the way these sound!

Thanks so much

blessu123

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RodC
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Re: 1678 mod newby question!

Post by RodC » Fri Aug 20, 2010 6:40 pm

blessu123 wrote:Hey guys, awesome post!
I have a green 1678 not a,b,c. Does anyone know if I can do the same mod. I love the way these sound!

Thanks so much

blessu123
The 1678 green is the same as the black, I think this was made during the green to black transition.
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RodC
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Post by RodC » Fri Aug 20, 2010 6:42 pm

the finger genius wrote:Gabe, Rod, or Pogo, I don't suppose you might have a parts list / ordering info? I'm extremely new to this, and I'm hoping to avoid ordering things which won't fit.
Man Im sorry I didnt reply to this, If you need me in the future email me or PM me. I get into really busy sections and loose time to follow the forums.
'Well, I've been to one world fair, a picnic, and a rodeo, and that's the stupidest thing I ever heard come over a set of earphones'

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Post by Jim Williams » Sat Aug 28, 2010 10:07 am

Now try some audio mods. Replace that 5534 and it's leaf socket. Use a Millimax or similar machined socket. Add a pair of .1 uf mono ceramic caps from pin's 4 and 7 to ground on each 5534.

Try these superior opamps: LME49710NA, LME49990, OPA1610, LT1357CN, AD8597, ADA 4898-1, ADA 4627-1. These are precision opamps with very low DC offsets. With the AD parts you can short out the gain set coupling cap for direct coupled sonics. Some are SOIC only, use Brown Dog or Aries adaptors to mount surface mount parts.
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Post by vowan » Sun Mar 20, 2011 5:47 pm

Hello!
Thanks for an interesting post.
I have acquired 1678 and now I begin it to mod.
About gain and volume all is clear.
By default filter HPF works only on a mix, but not a line out .
Whether it was possible to whom to re-direct that HPF on 1678 on a direct output?
Regards
Vladimir

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RodC
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Post by RodC » Mon Mar 21, 2011 5:42 pm

vowan wrote:Hello!
Thanks for an interesting post.
I have acquired 1678 and now I begin it to mod.
About gain and volume all is clear.
By default filter HPF works only on a mix, but not a line out .
Whether it was possible to whom to re-direct that HPF on 1678 on a direct output?
Regards
Vladimir
Welcome to the board. If you follow these instructions the HPF should work. The signal is taken from the level control which is after the filter.
'Well, I've been to one world fair, a picnic, and a rodeo, and that's the stupidest thing I ever heard come over a set of earphones'

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Post by vowan » Thu Mar 24, 2011 9:19 am

OK, I see.
I will try in the near future.
Simply I checked changing nothing and have thought of it.
Now I waiting pots and knobs to begin installation.
I have already checked up all an input/line output and using exterior pad-20 in avoidance overloads have recorded solo a sax, on what the sax-player has told that the sound turns out 70's :)

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Post by vowan » Thu Mar 24, 2011 9:55 am

Except 1678, I use 1592a as 4 channel mic pre.
I took a signal directly from a lug of a potentiometer of each channel and have deduced from on the back panel on the installed terminal.
From the terminal with the help of jacks I send on 4 linear inputs of Digi002.
Thus is 8 mic inputs.
Image
Usually it is necessary to reduce gain with exterior pads -10-20dB, and then to increase an accepted signal on Digi002 having turn on +4.
I thought to implement gain also, as in Altec 1592b.
But I use 1588a, and they unfortunately haven't gain control on pin 2.
Whether there is other way, except how to buy others preamps B or C series?
Or it is possible to change schematic of 1588?
Last edited by vowan on Tue Mar 29, 2011 3:35 pm, edited 1 time in total.

stupid_life
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Post by stupid_life » Tue Mar 29, 2011 2:39 pm

anyone have a line on a good, cheap +12v to +18v supply? what should I build/buy? I have a unit with the 1588 pres these have with a faulty PS and I would rather just put them in a seperate enclosure.

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RodC
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Post by RodC » Wed Mar 30, 2011 3:31 pm

vowan

I'm not too familiar with the 1588a, you will prob be better off with an inline pad before the preamp. (between the mic and the xlr input)

Most of these were designed for spoken voice and overload pretty easy.
'Well, I've been to one world fair, a picnic, and a rodeo, and that's the stupidest thing I ever heard come over a set of earphones'

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