[BUILD] 1176LN Rev D DIY

[edanderson]

edit: mako's analysis is correct, but it is more complicated than it seems.

ed

 

[Lowfreq]

Cool, thanks Ed. :thumb:

Ideally I'd like to have the correct transformer and a T attenuator, but for now I'll just work with what I've got.

Thanks for the info

 

[tommypiper]

Thanks Ed, Mako and everyone. Great discussion, interesting project.

I'm looking at this. It seems fairly straight forward. (Thanks NYDave)

[quote author="JdJ"] NYD's Bridged T Schem[/quote]

Also, seems like the PECs might be available according to Ed's earlier post today. Perhaps in less than 50 pieces too.

Then there's experimenting. I mean, why would you need to have 600 ohm on the inputs today anyway?

 

[strangeandbouncy]

Guys,

Thank you all for your replies, but perhaps I am not expressing myself properly. on the rev D diagram, there are more ""coils" than can be derived from a 600:600. So which do i ignore? brn to blk, whtblk to whtred, or grey to violet?. surly only one pair is valid. since x to y is the output?


I do hope I am not missing the wood for the trees.


All the best,


AndyP

 

[mnats]

[quote author="strangeandbouncy"]on the rev D diagram, there are more ""coils" than can be derived from a 600:600. So which do i ignore? [/quote]
Since you're a fan of the Rev D, you won't ignore any of the windings and will just get the correct iron just hook it up as shown. But if you were to use a 'normal' transformer, you would short the black to brown terminals as described earlier (or you won't have any power going to the line output stage), connect your primary to white/black and white/red, then use your secondary as normal. Since you wouldn't have a feedback winding, the grey and violet pads would not connect to anything.

 

[strangeandbouncy]

Mnats,

thank you. I was just wanting to lash up the output until the correct output tranny is available.


Many thanks,


AndyP

 

[tommypiper]

What was the original input transformer ratio used 1.5:1?

cheers.

 

[dissonantstring]

hi tommy,
the original used a UTC 0-12 ouncer in reverse on input.
-grant

 

[gevermil]

500:200 ohms

 

[tommypiper]

Where do we find a UTC 0-12 diagram?

cheers

 

[Sleeper]

First, MAKO, the boards are great, got mine nearly stuffed, and thanks for the psu boards!! I'll run some relays etc. off of those. cool.

I've been looking over all the provided links regardingthe attenuator and i have a few questions still...

OK, so the dual pot approach is complicated because of the special Z taper (rev. log going in 2 directions) required. AND Ed Anderson says a 1/2 watt pot might get burned by high level signals.

Can a dual 1k be modified as below to get the taper... or will this raise havoc with our actual input and output impedences... I've used this a few times to change the law of a pot and it worked pretty well in simple unbalanced gain controls, not sure if floating this will cause problems.

more info. here
http://www.elby-designs.com/documents/tailoringpotentionometers.pdf

NewYorkDave's bridged-t looks pretty good. It's not continuously variable, but my input sources mostly have some output control, enough to do the fine tuning.
BUT? I know pots are more easily toasted, but if a 1/2 watt pot might get burned, how come there are 1/4 watt resistors in the (purple diagram) t-attenuator? Can I use 1/4 watt resistors in the stepped bridged-t?

Thanks
Kelly

 

[Sleeper]

For the short term, problem solved...look at this clarostat CIBT43-600, Bridged T-Pad Potentiometer.
Kelly





Looks like they have about 25 more of these - 29.95 each
http://cgi.ebay.com/ws/eBayISAPI.dl...MEWN:IT&viewitem=&item=230002096428&rd=1&rd=1

 

[dissonantstring]

[quote author="tommypiper"]Where do we find a UTC 0-12 diagram? [/quote]
here:
http://www.waltzingbear.com/Schematics/UTC.html
found this on uncle CJ's meta pages. 2nd page of pdf. file.
check page 4 of the pinout diagrams and look for diagram AG.
regards,
grant

man, i haven't checked the transformer meta pages in a while...uncle CJ has been busy! everyone should check it out! :thumb: great job CJ!! :guinness:

 

[tommypiper]

Thanks for the UTC link. I'll have to check out CJ's activities.

Thanks to Sleeper for the heads up on the bridged Ts on ebay. Looks exactly like the two deck on the Purple schematic. Is it really the right one? They're going fast.

 

[kazper]

I snatched up all I could afford at the moment (1) and there was 14 left
Payed for it refilled the coffee cup and came back to the forum and went to look again and now looks like 6 units left..

 

[kato]

And when 6 became 5:

[quote author="ebay"]The seller ended this listing early because the item is no longer available for sale.[/quote]

 

[tomcat]

Strange. There was 1 more available. Was...

 

[Sleeper]

Wow guys, those went quick.
I should-a bought them all and sold them to you all at a profit.
Kidding-wink:
I have one of the clarostat datasheets and schematic wise the cibt is exactly the same as the PurpleAudio dual pot bridged -t. I hope they work as well it appears they should.

One word of caution, I got a box once with a bunch of the clarostat attenuators- many different part numbers, l-pads, ladder attenuators etc.
they are most likely about 1 1/2 inches round, this could cause you trouble on stereo 1176 panel layouts.

I'm still curious if the solution I posted above might work. Like I said, I've used a resistor to change a potentiometers law before, but I don't have a scope that lets me make a graph or sweep and really see what happens if it is done that way. I've changed linears to audio taper this way and they feel much better and sound ok. I'm curious if pots modified this way would track ok.

Kelly

 

[tommypiper]

The Clarostats sale is still active. 5 left.

 

[strangeandbouncy]

Mnats,


my boards arrrived this morning. Wonderful, and SO fast!



BUT :shock: :sad:


There appears to be a mistake or fault. I was stuffing my first board and checking as `i went, and found a dead short across R37(470k). The un-populated board is exactly the same, which by my reckoning. means that the input to the control amp is shorted. Plase forgive me if I am wrong, but . . . .

Has anyone actually completed one yet?


Help!


ANDyP