Altec 1628a Mods - and 1674 and 1678 .....

wkrbee · Post by **wkrbee** » Mon Jul 17, 2006 6:07 pm

A Japanese brand at least 25 years old.They were used in a VSK88 varispeed box for the 80-8,(.5 inch 8 track recorder).The last 9 pcs.They just wanted to get rid of them.I have a bunch of small 50k pots.Would they work OK for the pad pots?

RodC · Post by **RodC** » Mon Jul 17, 2006 9:21 pm

50K would prob work fine. I have to get some pics of the last one I did, I hope to update my site soon.

RodC · Post by **RodC** » Sat Aug 05, 2006 9:18 am

From chris in another post but want to update this thread:

RodC wrote:
@?,*???&? wrote: A side-note here too for Rod. Your suggested mod was perfect for the Altec 1678 btw. The units still need pads, but I picked up these 3-position pad barrels from Shure and am uber happy with this. I do have a second un-modded unit now if you're interested.
Cool, I would love to hear one of those units. Have you been following my thread that we discussed these units on? I added gain pots to my 1628a units so now I can adjust the gain and the output level. I can record quiet drum OHs, Dirty toms, or blasting guitar cabs with them.

Placing a smaller resistor across 101, 201... may sound better than a pad on the mic. This would cause the mic to see a more constant impedance.

You could replace it with a 100K pot and have a variable pad, but then you would have to mount it.

chrissss · Post by **chrissss** » Thu Sep 28, 2006 2:03 pm

minor update:

finished all the mods i can concieve of on my 1628a:

individual unbalanced outs (i only have 3 cans in the thing)
phanom power switches (for 4 of the channels / in case i get another can)
25k gain pots (as described by rod)
replaced filter caps
replaced hipass cap

result:

well after all that i've decided i'm not thrilled with the sound. it works really well for some low fi midrangey vocal stuff, but there is virtually no low end. i'm not sure if that's an interaction thing (the unbal outs go to the inserts on my soundworkshop 1600) or if there are still caps i need to hit up, but there don't seem to be any other caps in the signal path. In comparison the SW pres have way more low mids than the altec, and the Shure m67 pres have way more low lows than the altec, so i don't know. . . .

RodC · Post by **RodC** » Thu Sep 28, 2006 2:13 pm

Thats strange, I record bass drums, toms and bass cabs with mine all the time, Seems to have plenty of low end. Usualy I end up rolling off some of the lows.

Does yours have the 1588c cans?

Have you tried it without using it in the inserts?

RodC · Post by **RodC** » Thu Sep 28, 2006 2:18 pm

One more thing, you stated you replaced the hipass cap, are you talking about the cap that is switched in and out by the Switch? If so, I would just put a jumper across that, or put the switch in the Out position.

A.David.MacKinnon · Post by **A.David.MacKinnon** » Thu Sep 28, 2006 10:48 pm

Someone mentioned somwhere in this discussion that if you're running these thing as direct outs you should replace the output volume for each pre with a 1meg pot. Or some thing like that.
The theory is that the stock pot buggers up the impedance at anything but full volume. Maybe this is the reason your's has no bass.

chrissss · Post by **chrissss** » Fri Sep 29, 2006 11:27 pm

yeah, it's got the 1588c cans in it. the hp caps i replaced were the switchable ones and they're off on two out of three of the channels. I wonder if it's because i'm going into the inserts, but on the board the tape ins are supposed to be balanced, (it's also a touch reach cable wise). I don't remember the tape in's on the board sounding much better, but i'm on the road so i can't check it again. i should probably have tried going directly into the digi002.

chrissss · Post by **chrissss** » Thu Nov 08, 2007 10:31 pm

Hey,

Just a heads up, I'm back and I tested it going directly into the 002. It definitely does have low end. Must have been the way I had it going through the board.

A/Bed it with a modern pre, a focusrite isa220, which i generally don't like, but it was the easiest to patch in.

with a 58 the altec had more low end and was a bit softer than the 220. I definitely preferred it.

I tried it with an sm7 (one of my favorite vocal mics) and it didn't have enough gain to do much of anything. i also tried it with a 4033, but i don't think it could supply enough phantom power or something. the 4033 was distorted. I have an outboard phantom supply that I'll try it with as soon as i can find the power adapter for it!

chris

chrissss · Post by **chrissss** » Thu Nov 08, 2007 10:37 pm

oh, also, i A/Bed the altec's direct outs (from the individual 1588c) against the balanced output of the automixer and found that it had a bit less bass and more mids and highs through the outputs of the automixer itself. Going through the balanced output, there was enough gain to supply the sm7 too. That was obviously much brighter.

RodC · Post by **RodC** » Fri Nov 09, 2007 5:06 am

chrissss wrote: i also tried it with a 4033, but i don't think it could supply enough phantom power or something. the 4033 was distorted. I have an outboard phantom supply that I'll try it with as soon as i can find the power adapter for it!

chris

They only supply 15V phantom power.

bibleboy3 · Post by **bibleboy3** » Sun Jan 25, 2009 9:02 am

has anyone got any more info on the 1628?? also whats the difference between the versions of the 1588 cans I do know the "C" version is capable of phantom power and the "A & B" can't pass phantom but what other differences remain??? a schematic would be awesome!!

Bill

Message Board

Altec 1628a Mods - and 1674 and 1678 .....

1628 mods

Who is online