Rebuilding XOs with new electronics

[bfish]

Originally posted by Old Guy:ROTFL. Coward!

<font size="2" face="Verdana, Helvetica, sans-serif">It's just that there aren't many like you who can debate an issue without getting personal.

My cowardice comes from spending too many years with a hateful b**ch. I spent more than one miserable night hiding from her on the roof (it was down to that or killing her). Finally cut my losses, gave her everything I had and sent her packing. Shoulda done it sooner.

Yep, copper's copper, though I'll occasionally splurge for the tinned variety for solder applications.

FWIW, I think cap stability has improved considerably since we went to school. I've checked lots of 20-yr-old caps that were still right on the money, especially the better Spragues and CDEs (which Altec used a lot of). I've bought nothing but Spragues and Nichicons for years. Often, you can get a 100-lot for a few $, and pick through them for the EXACT values you need, then sell the remainder so others can do the same, and you either get your money back or even make a buck.

[GM]

Greets!

Yeah, for the life of me I can't remember the company names, but when I retired in '94 there was only one company making cap containers, one for the chemicals, and a couple for the paper/foil/whatever innards left 'standing' IIRC, and none were name brands (at least in the USA), with only a few assembly companies around the world, so which product got what brand name attached to it depended on its QA score, like CRT tubes or basic ckt. boards, etc, churned out by the currect low bidder.

GM

[Old Guy]

Mostly for the engineering geeks among us, or the terminally curious. The Capacitor Book is a good thing to skim.

http://www.faradnet.com/

[bfish]

Your cap comparison link is a good one, GM, and it made me realize I should probably clarify my ramblings further (collective groan). There definitely ARE differences in the TYPE of capacitor you use (i.e. PIO, polyester, mylar, etc), something I perhaps mistakenly assumed everyone knew. What I intended to downplay was the signifigance of the BRAND of caps selected (i.e. Sprague, Solen, Auricap, etc), particularly to point out that one needn't spend the big $ that many brands of "audio" caps command, particularly when equivalent or superior caps of the same type and quality are available for much less. Also, my references to 'paper-bodied' caps do not include PIOs (paper-in-oil), which aren't housed in paper bodies. Paper-bodied caps (which haven't been made in years that I know of) are at the bottom of the totem pole, while PIOs are at or near the top. While we like to think of audio gear as being extremely complex and demanding of its' components, most modern capacitors are designed for Mhz and even Ghz applications, and are loafing at the Khz apps we disscuss.

As Old Guy noted, the best cap is no cap. Taken a step further, IMO, the best music is live music, which removes the recording manipulations, most of the signal paths, and most of the compromised reproduction equipment. Taking live music "to go" forces us to deal with all these compromises and to live with the results. My crusade is aimed at knocking the blocks out from under those that would attempt to overcharge for compromises that offer no advantages.

[gamalot]

Great discussions and lots of excellent info but I probably should have been more clear in the purpose of my thread.
I can't find old XOs for my Model 19 clones at a reasonable cost.
I am thinking about having a friend build a pair of XOs that do the same exact electronic functions of the old but use new parts.
These need not say Model 19 or 1201-8A on them but they do need to do the same to the signal and reproduce the same resulting sound.

I am a complete bafoon with electronics hence employing a friend to do this build- he is a complete bafoon with cabinetry so it works for us both.

I get lost when he starts asking questions that he needs to know to build these, Ie; What is the inductance and impedence of the three coils?
Are these first order, second or third? Is there a Zobel or other filter? what are the octive steps of the XOs?
All greek to me so I can't help him do what I need done.
My thought is to build them useing the best available parts today but then he throws all these curve balls at me that I can't hit.
Guess I should stick to playing with my wood and leave the electronics to you guys but I do need some help to pass on the info to him.

What would a tech who is building 1201-8A XOs need to know to be able to build them from scratch. Is this info available or can anyone provide it to help me out here?

Thanks again and I do enjoy all the friendly bantar even if there is some ducking going on.
Gary

[bfish]

Hi, gary,

Sometimes you just have to move one little rock to start a landslide.

Everything one should need to build a repro M19 XO can be found here, courtesy the work of Jeff Markwart;

http://home.earthlink.net/~jmarkwart...1201-8aRev.pdf

[gamalot]

Thanks bfish but i get confused easily with this stuff and all the questions.
Not knowing or understanding how to read these schematics, is info such as first, second or third order, octive slopes like 12Db/18Db and values such as coil inductance and impedence contained in this schematic?

Could his questions be because my friend who claims to be a tech just does not know how to read these any better then I do? In this case, maybe I should look for another tech?????

Gary

[Old Guy]

Originally posted by gamalot:
Could his questions be because my friend who claims to be a tech just does not know how to read these any better then I do? In this case, maybe I should look for another tech?????

Gary

<font size="2" face="Verdana, Helvetica, sans-serif">If he can't find those answers from the schematic you should look for another tech.

Those answers should be obvious to a competent HOBBYIST, let alone someone who is trying to pass as a tech. Don't want to offend your friend, you just are not going to get what you want from him.

[GM]

Greets!

Sounds like it's time for a little 'tough love' since for him to duplicate a functional equivalent of a specific XO he doesn't need to know the point/slope or anything else that's not on Jeff's schematic, so trust your friend to do it at your own financial peril IMO.

WRT cost, quality costs either in $$ and/or in size and/or in time spent, so unless you're prepared to use large A/C motor run caps where possible and make your own inductors to minimize it, this won't be a cheap DIY project by most folk's standards.

GM

[GM]

Greets!

The problem with caps is that unless they're PIO, they ring, and IIRC Altec was using polyprops by then, though not sure if foil or film, so to ~replicate the original's sonic signature you'll have to find out what they were and duplicate them as close as practical, ditto with inductor specs. Then there's the trim pots........... good luck with that particular 'can o' worms'.

GM