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Stepped Attenuator

post #1 of 31
Thread Starter 
Hello,

I built a 12 step attenuator. I used six 2.2K resistors and five 7.5K resistors. (per channel) I get somewhat natural (logarithmic) volume control.

The resistors are connected in series. Unfortunately, ladder attenuators require such effort and money. Besides, getting the precise values for the ladder is extremely hard.

Noice level is very low and made the overall sound more cleaner. I like it fine.

Only bad thing is that rotary switches are costly (31 USD!!). So if you can afford it, building stepped attenuators is fun and worth it.

Note this rotary switch must have "shorting" contacts.

The resistors must be high quality. I used RN55's. Riken might have too much carbony sound to it. You should choose resistors which are as transparent/tasteless as possible. I would like to use NS-2B bit could not afford them :<

Tomo

P.S. I got me some 24 step rotary switches from my hush-hush connections I will try this out and tell ya how this one turn out.
post #2 of 31
Hehe, sometime, I'm going to have to find out what/where these connections are

I just placed an order yesterday for a digital pot, the DS1802 mentioned in a thread recently brought back from summer 2000. I'm going to have to resort to the momentary toggle rather than a rotary switch with spring return since the only one I found that I could order from the same place as the DS1802 was very expensive.

I'm just looking forward to close channel matching
post #3 of 31
Thread Starter 
Hey,

If you spend time on the net, you will find some cheap ones as I have. You do not need to be "The One" and modify the fabric of reality to get rotary switches at reasonable prices.

I was itching to do something over last weekend and tested the hypothesis that stepped attenuators are better alternative to Noble pots. Cost was justified by recent influx of mil-spec rot switches into my inventory.

Tomo (is not Neo)
post #4 of 31
I have toyed with the idea of using a Digital Pot with the 1802 chip as sugested by Apaheared. I have been resistent to using this technology because of the added Noise and Distortion. I like the Idea of Close Channel tracking, This is most importent with headphones. Conventional Pots, Evean the Finest Alps have tracking imbalances that is noticable to me. The Stepped switched Attinuator is at the Moment the Most attractive to me. So I would like to hear all your views on thest alternatives from those that have used Eather or better yet Both types?
post #5 of 31
Although pricy, the goldpoint attenuators are excellent.

http://www.goldpt.com
post #6 of 31
Doc B has 12-step (3dB per step) DIY attenuator kit for $40.

http://www.bottlehead.com
post #7 of 31
Goldpoint uses ELMA switches, which are well known. Their shipping price (out of US and registered, but still just plain old regular USPS) is however outrageous - US$23 for something that small and light!?
post #8 of 31
Thanks Guy's Will check into these. NowWhat about the DS-1802 Aparheared, Any one?
post #9 of 31
ppl, go check your mailbox Monday. I sent you one. Try it. Then you can tell us your own opinion.
post #10 of 31
Ya Know one Thing i Like about This New Site Is The v-Bulliton Software. Ya-Know Who'w Responding and low and Behold My old Frend Mr Apheared, Thanks I will Try one In My Latest Still On Board Only Havent Drilled The case Yet Cut A peice Of Extruned Aluminium From An old Skylight I have Laying around, Looks Real Professional When Done. BTW if Ya have Any TLE2624 Virtual Gnd Drivers I need One I fried One In one Channel Of This New amp That uses A couple of Them in Addition To My Present Inhancements, But Simulate to a 25 Db Power supply Rejection ratio vs my Old way, Whitch BTW gave me an added 70-90 Db Depending upon Actual Components. It is A True Dual Mono With Separate 16 Cell AAA Packs on each Channeling. Good News The Massive Capacitor 15K used on the OPamp Only Rails has been Reduced To 100 Uf With No Loss in Sonics In fact I thing It may sound Quicker Than Befor.Any How ill mail Ya Schematic I would Attach But not on The PC that's on.
post #11 of 31
Thread Starter 
Hello,

I heard about two types of digital attenuators. One, the chip essentially becomes the rotary switches connected to external resistors. Two, the chip contains the resistors also.

DACT also makes stepped attenuators. These only comes in Series version however uses very low noise chip resistors. They boasts that their attenuators have extremely low inductance and what not and are transparent.

Shallco, Electroswitch and Seiden makes switches that are good for audio attenuators. But these are all costly. Please keep this secret among HeadWizers. Mil-Spec Rot Switchs are equally good or may be better. ... (Think about it carefully, it is much important for our attack helicoper pilots to be able to accurately select options in their missions, than for audiophile to drool over the music.)

Tomo

P.S. Correction: Please replace the present tense in the previous sentence to the past tense. ...
post #12 of 31
Quote:
Originally posted by Tomo
Hello,

I heard about two types of digital attenuators. One, the chip essentially becomes the rotary switches connected to external resistors. Two, the chip contains the resistors also.

DACT also makes stepped attenuators. These only comes in Series version however uses very low noise chip resistors. They boasts that their attenuators have extremely low inductance and what not and are transparent.

Shallco, Electroswitch and Seiden makes switches that are good for audio attenuators. But these are all costly. Please keep this secret among HeadWizers. Mil-Spec Rot Switchs are equally good or may be better. ... (Think about it carefully, it is much important for our attack helicoper pilots to be able to accurately select options in their missions, than for audiophile to drool over the music.)
Tomo Hi good to hear from you again. Thanks for theadvice Since my Amps keep getting more accurate and the parts quality going up in all areas the Volume control is the Last put Most importent Place for Me to Finnish up my latest amp.
Tomo

P.S. Correction: Please replace the present tense in the previous sentence to the past tense. ...
post #13 of 31
So what should one be looking for in the rotary switches? How many poles do you need for dual channels? What does "shorting" refer to?
post #14 of 31
Shorting, also known as Make Before Break (MBB)... means just that... as you switch from one setting to the next, it makes the connection to the next switch pole before disconnecting the connection to the previous pole... it makes a 2-pole short.

Non-shorting a.k.a. Break Before Make (BBM) does not... your switch dangles in space as it passes from one pole to the next... no connection.

For most things that we do, you always want to use shorting ones. Crossfeed selectors, bass boosts, and attenuators... minimizes the audible "pop" (and non-shorting leaves things in a bad state - you might hear some silly/nasty things holding the switch between poles) You still may hear a glitchy sound, usually from contact bounce (see electromechanical relay documents for a great description).

ppl, heh sheesh, what is it with people asking me for TLE2426s?!? I'm gonna buy a palette of them and hand em out as Christmas gifts! They're only $1.25 or so in Q:1, I guess everybody always forgets to order them when ordering everything else. (it's the most asked Q: hey apheared, do you have..)
post #15 of 31
Those must be popular.I started out With TLE's aplenty Must indeed get more. My Circuit works with the one Missing Or shall i say removed Because it now joines your AD-825 in the Semiconductor Afterlife. However I am sure having Both Channels matched as i started out Diong would sound Better.
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