kdawg
Well-known member
But who carries any Clarostat dual/tri pots? Digikey has them as "discontinued", Newark has them at "Special Order" with 95 day lead time...
600 ohm T attenuators?
- Thread starter kdawg
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edanderson
Well-known member
[quote author="EP"]You will need 2- 500 ohms, and 1- 1k ohm.
Configuration 500-1000-500 ohm[/quote]
for a 500 ohm (close enuff to 600) config, the 1k will have to be a log/audio or what clarostat calls "Z" taper. otherwise the impedance and level change will not be how you want. also, a 1/2w rated pot could theoretically be burnt out by driving ridiculously large signals into it.
[quote author="kdawg"]But who carries any Clarostat dual/tri pots? Digikey has them as "discontinued", Newark has them at "Special Order" with 95 day lead time...[/quote]
this is the real problem. even if you could buy and disassemble 3 single 308 series pots from digikey or allied (cheaper), you would need a shaft long enough to go through all three. also the sections are held to each other and the bushing/back by rivets. you can cut them to disassemble, but you'll need very small screws and nuts to put the whole thing back together.
the only place i know of to get all the things you need for this endeavor is state electronics (potentiometer.com). and they won't sell you the parts for just one. they might sell you one completed assembly, but it won't be cheap.
ed
Configuration 500-1000-500 ohm[/quote]
for a 500 ohm (close enuff to 600) config, the 1k will have to be a log/audio or what clarostat calls "Z" taper. otherwise the impedance and level change will not be how you want. also, a 1/2w rated pot could theoretically be burnt out by driving ridiculously large signals into it.
[quote author="kdawg"]But who carries any Clarostat dual/tri pots? Digikey has them as "discontinued", Newark has them at "Special Order" with 95 day lead time...[/quote]
this is the real problem. even if you could buy and disassemble 3 single 308 series pots from digikey or allied (cheaper), you would need a shaft long enough to go through all three. also the sections are held to each other and the bushing/back by rivets. you can cut them to disassemble, but you'll need very small screws and nuts to put the whole thing back together.
the only place i know of to get all the things you need for this endeavor is state electronics (potentiometer.com). and they won't sell you the parts for just one. they might sell you one completed assembly, but it won't be cheap.
ed
edanderson
Well-known member
[quote author="kdawg"]I've also seen that Mallory has a T600 attenuator, but it seems hard to find - and expensive maybe? [/quote]
i supplied a few of these to forum members when i was able to find them cheap as surplus. they do work, but they are wirewound (so they can't be burnt out by high level signals), so they are stiff and the action is not smooth. also they are physically pretty large. SSLtech had some pics of his bloo-panelled mc76 kit that he did with the ones i sold him. at the >$100 price they go for new, i don't think they are a good option for most applications.
ed
i supplied a few of these to forum members when i was able to find them cheap as surplus. they do work, but they are wirewound (so they can't be burnt out by high level signals), so they are stiff and the action is not smooth. also they are physically pretty large. SSLtech had some pics of his bloo-panelled mc76 kit that he did with the ones i sold him. at the >$100 price they go for new, i don't think they are a good option for most applications.
ed
kdawg
Well-known member
so is this part of Purple's difficulty in fulfilling kits? What are they currently using for their input pot? And input transformers?
-kdawg
-kdawg
edanderson
Well-known member
it is a custom 70 series clarostat 3 deck pot with a two 500 ohm decks and one 1kZ deck. they aren't cheap, and we do have to wait for them to be made to order. we've had more problems with getting the meter and ratio switches than any other part.
we've used UTC O-12s with O-17s for input transformers in the past, just like original urei units. but getting them for a reasonable price on the used market is getting very difficult. soon we will be switching over to our own custom-wound input that will be a replica of the O-12.
ed
we've used UTC O-12s with O-17s for input transformers in the past, just like original urei units. but getting them for a reasonable price on the used market is getting very difficult. soon we will be switching over to our own custom-wound input that will be a replica of the O-12.
ed
kdawg
Well-known member
I've decided to play around with an Alpha dual 500 ohm linear pot as an attenuator. I know the tapers aren't correct, but is there a configuration as a input bridged T attenuator that will work with my 500:200 transformer? I though it would be worth a shot since it's a $2.50 part. Thanks
-kdawg
-kdawg
cannikin
Well-known member
how about one of these?
http://www.surplussales.com/Potentiometers/Audio/MiscPots.html
http://www.surplussales.com/Potentiometers/Audio/MiscPots.html
edanderson
Well-known member
http://gearslutz.com/board/showthread.php3?p=626569#post620358
this thread over at gearslutz shows the new bridged T attenuator that UA is having made by PEC (the same company that has been making their LA2 pots). someone could contact PEC about a group order, or people can call UA and try to get one as a replacement part. i don't have a part number, but hopefully if you call and ask for a 600 ohm bridged T attenuator, they should know what you're asking for.
ed
this thread over at gearslutz shows the new bridged T attenuator that UA is having made by PEC (the same company that has been making their LA2 pots). someone could contact PEC about a group order, or people can call UA and try to get one as a replacement part. i don't have a part number, but hopefully if you call and ask for a 600 ohm bridged T attenuator, they should know what you're asking for.
ed
It's a shame that not many people are making this stuff. There used to be so much of it.
I went over to Andy's garage the other day and he pulled out a whole box of old school attenuators, pots, bridge T's, H pads, audio taper CTS with detents, I couldn't believe all the different companies and models of stuff were in that box.
Now all you see is a box of Allen Bradlys at the surplus.
WHats this mean? Simply that we now have to go through hassles to get what was once available by the truckload.
I went over to Andy's garage the other day and he pulled out a whole box of old school attenuators, pots, bridge T's, H pads, audio taper CTS with detents, I couldn't believe all the different companies and models of stuff were in that box.
Now all you see is a box of Allen Bradlys at the surplus.
WHats this mean? Simply that we now have to go through hassles to get what was once available by the truckload.
kdawg
Well-known member
Ed - I got a few of these from UA a few months ago (I talked to Tom), apparently they are charging $80 a piece for them but I got them down to $50. After shedding a few tears at that price, I did receive them and they are indeed the PEC pots you mentioned. I also managed to call PEC with the pot part number, and they indeed have them but will not sell to the public without UA's consent because it is a proprietary part. They also have a 2500 piece minimum I believe.
I'm not sure what the best solution is for this - I have to say the Gyraf 1176 used with UTC input transformers and this pot makes such a difference, the range of input feels right now - a lot more finer adjustment around the 10 o'clock position area.
-kdawg
I'm not sure what the best solution is for this - I have to say the Gyraf 1176 used with UTC input transformers and this pot makes such a difference, the range of input feels right now - a lot more finer adjustment around the 10 o'clock position area.
-kdawg
adrianh
Well-known member
yu-all people are driving me nuts.
Simple measure the pot exactly the P E C one.
Make a drawing for max physical size.
Give them the tapers and electrial specs.
You may need to get their catalog or specs
of a standard product.
The document you send them should
back them into a corner so the only part
that meets the specs is the other part they are selling.
Be sure you place a special part number (your special number)
Then with that drawing they will be building the exact same part
for 2 companies. And they are actually building 2 custom parts.
Just get a company setup to buy them.
Simple measure the pot exactly the P E C one.
Make a drawing for max physical size.
Give them the tapers and electrial specs.
You may need to get their catalog or specs
of a standard product.
The document you send them should
back them into a corner so the only part
that meets the specs is the other part they are selling.
Be sure you place a special part number (your special number)
Then with that drawing they will be building the exact same part
for 2 companies. And they are actually building 2 custom parts.
Just get a company setup to buy them.
ap123
Well-known member
Is the idea here that if I can find a way to gang three pots together I can build my own t600 bridged attenuator? I looked at the 1176 schematics and see the attenuator but can't figure out how they'd actually be wired. Can someone tell me which 3 pots I need? Can this really be done if you manage to gang the three pots (with resistance and taper)? I'm a bit unclear after reading this thread.
kato
Well-known member
AP123, there's a way to make your own T-attenuator from a dual ganged pot - like on the earlier Purple MC77's, or with a tri-ganged pot - like on the current MC77s. (I'm sure you read that already in your searching.)
The schematic you posted looks like the dual-gang version - which is the one you should probably build because it's a lot easier to find a dual-gang pot than a 3-gang.
Here's a screenshot of the 2-ganged version from the Purple schematic:
The schematic you posted looks like the dual-gang version - which is the one you should probably build because it's a lot easier to find a dual-gang pot than a 3-gang.
Here's a screenshot of the 2-ganged version from the Purple schematic:
NewYorkDave
Well-known member
Look at a table of values for series and shunt arms in a bridged-T attenuator and you'll see you'd need a special pot to do it. This has come up a few times before... The short story is, you can't do it with an off-the-shelf pot.
ap123
Well-known member
This thread is one big emotional rollercoaster.
In the 2-gang version from the purple schematic, R1 is a 2-gang 1k audio taper?
NewYorkDave, can I ask: what would you do if it was your 1176?
In the 2-gang version from the purple schematic, R1 is a 2-gang 1k audio taper?
NewYorkDave, can I ask: what would you do if it was your 1176?
NewYorkDave
Well-known member
Listen... The series and shunt arms are NOT the same value and NOT the same taper. It's not an off-the-shelf pot.
If you don't mind steps, there's THIS.
This has been discussed here many times. Here's just a couple of threads to start:
http://www.groupdiy.com/index.php?topic=4937&highlight
http://www.groupdiy.com/index.php?topic=3497&highlight
If you don't mind steps, there's THIS.
This has been discussed here many times. Here's just a couple of threads to start:
http://www.groupdiy.com/index.php?topic=4937&highlight
http://www.groupdiy.com/index.php?topic=3497&highlight
nerd
Active member
So, Your saying if you took an off the shelf dual pot and broke it open intending to swap the elements from different pots, you would not be able to find the correct elements becuase the taper is not a standard linear or audio taper?
NewYorkDave
Well-known member
I said the dual pot you need is not an off-the-shelf part. You're drawing conclusions beyond what I said.
Anyway, that's all I'm going to say on the subject. (Remember, this has come up several times before). Like I said, study the table of values for a bridged-T attenuator and you'll figure out which way to go--you'll know if what you're thinking of doing is feasible or not.
Just as an aside: I am getting so sick of hearing about 1176 and SSL bus compressor clones. I wish there was a separate forum for them. :?
Anyway, that's all I'm going to say on the subject. (Remember, this has come up several times before). Like I said, study the table of values for a bridged-T attenuator and you'll figure out which way to go--you'll know if what you're thinking of doing is feasible or not.
Just as an aside: I am getting so sick of hearing about 1176 and SSL bus compressor clones. I wish there was a separate forum for them. :?
NewYorkDave
Well-known member
enthalpystudios
Well-known member
very nice scan... handy chart indeed, thanks dave
