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altec 1678c mod..direct out/gain control..AUDIO SAMPLES!
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the finger genius
re-cappin' neve


Joined: 15 Nov 2006
Posts: 746

PostPosted: Tue Oct 06, 2009 9:47 am    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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
re-cappin' neve


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PostPosted: Tue Oct 06, 2009 7:44 pm    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CT2239-ND
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You may quote me.

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gabe real
takin' a dinner break
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Joined: 27 Mar 2007
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Location: riverside, california

PostPosted: Wed Oct 07, 2009 4:10 am    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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
re-cappin' neve


Joined: 15 Nov 2006
Posts: 746

PostPosted: Wed Oct 07, 2009 7:27 am    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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?
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That said, what I'm gettin' at is, perfectionism is for the truly defective.

You may quote me.

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gabe real
takin' a dinner break
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Joined: 27 Mar 2007
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Location: riverside, california

PostPosted: Wed Oct 07, 2009 1:16 pm    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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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blessu123
audio school


Joined: 15 Aug 2010
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PostPosted: Sun Aug 15, 2010 9:25 am    Post subject: 1678 mod newby question! Reply with quote

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
dead but not forgotten


Joined: 31 Dec 2004
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PostPosted: Fri Aug 20, 2010 9:40 pm    Post subject: Re: 1678 mod newby question! Reply with quote

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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PostPosted: Fri Aug 20, 2010 9:42 pm    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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.
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Jim Williams
tinnitus


Joined: 03 Jun 2006
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Location: beautiful Carlsbad, CA

PostPosted: Sat Aug 28, 2010 1:07 pm    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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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vowan
audio school graduate


Joined: 30 Jun 2009
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Location: Saint Petersburg,ru

PostPosted: Sun Mar 20, 2011 8:47 pm    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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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PostPosted: Mon Mar 21, 2011 8:42 pm    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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.
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vowan
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PostPosted: Thu Mar 24, 2011 12:19 pm    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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 Smile
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vowan
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PostPosted: Thu Mar 24, 2011 12:55 pm    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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.

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 6:35 pm; edited 1 time in total
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stupid_life
ass engineer


Joined: 01 Jul 2010
Posts: 45

PostPosted: Tue Mar 29, 2011 5:39 pm    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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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PostPosted: Wed Mar 30, 2011 6:31 pm    Post subject: Re: altec 1678c mod..direct out/gain control..AUDIO SAMPLES! Reply with quote

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.
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