• Please note that Audiokarma will be offline briefly for updates early on Monday morning, September 28th.

Passive Pre

Why does it make a difference? Just that it presents a low load to the source when the resistors are on the backside of the pots?
 
Not sure what the difference is, but it went from "off" to mildly loud instantly. Not good. I seriously thought I'd screwed up the project. Thank goodness for easy fixes!
 
partsconneXion

Use the link from the list of AK sponsors below. They're a great little outfit with a nice selection of stuff. You get great service, an order confirmation, and prompt shipping from Canada. Shipping isn't off the charts, either.
 
Yeah, I don't really know what I mean... :stupid:

I meant to say that it "gets loud fast." I've since made some circuit changes in the amp I was testing it on, and the pre behaves normally now. You can totally disregard that previous statement.
 
Nice.

I have a couple of these cases I have been hanging on to. I knew a project would come up for them! :)
 
Just built one of these preamps and WOW! I really didn't think I would like the passive pre without the tone contriols but I dont miss it at all!. BTW I switched R1 to 20k ohm and I get a little better control of the volume. Everything else is the standard Rat Shack fare. 2 100k ohm alpha audio tapers, 1/2 watt carbon resistors and standard RCAs and a plastic project box. This is my first ever scratch built audio component! I've reworked a few crossovers and they have been rewarding, but this thing is kind of enlightening! I now hear what everyone is talking about and I think I'm going to have to build a power amp next! I can only imagine what this would sound like with quality components.

Here is my setup: (pictures as soon as I find my camera)

Yamaha CR 1020 (decoupled, using power amp section)
Harry Haller's Passive Pre
Large Advents (restored U3 model on home built stands)
Sony PS x500 w/ AT440MLA (ran through Yamaha phono section/tape out to pre)
BPC JVC CDP (ran through Yamaha aux input/tape out)
 
Right on, twist72! I'm looking forward to the pictures.

I'm considering building this pre right into my main amp. It uses a 100K stereo volume pot wired in standard configuration. I'd like to hear if there's a difference.
 
Well, I can't find my digital camera. I must have lost it in the move( however that happens). Ill break out my Russian Leica copy and take some pics later this week.

Anyways I bypassed the preamp on my Accurian amp and ran the passive into it. It sounds fine but the volume is very low when maxed out, at least half of the volume if I just run my source into the Accurian itself.

Could this be because I used 20k resistors instead of the 11k? I really don't understand how all this stuff works yet so please be gentle! :)

BTW the Accurian Amp is impressive considering its cost. I'm playing a Disco 79 studio sampler through it straight up with no pre and it has some definite thump. Granted I'm running Large Advents. I bet it would sound better with more efficient speakers.
 
Well, I can't find my digital camera. I must have lost it in the move( however that happens). Ill break out my Russian Leica copy and take some pics later this week.

Anyways I bypassed the preamp on my Accurian amp and ran the passive into it. It sounds fine but the volume is very low when maxed out, at least half of the volume if I just run my source into the Accurian itself.

Could this be because I used 20k resistors instead of the 11k? I really don't understand how all this stuff works yet so please be gentle! :)

BTW the Accurian Amp is impressive considering its cost. I'm playing a Disco 79 studio sampler through it straight up with no pre and it has some definite thump. Granted I'm running Large Advents. I bet it would sound better with more efficient speakers.
 
twist72 said:
It sounds fine but the volume is very low when maxed out, at least half of the volume if I just run my source into the Accurian itself.

Could this be because I used 20k resistors instead of the 11k?
Click to expand...
Sounds plausible.
 
Moved this post from Redboy's thread because I realized it made more sense here. This is the original design, except with two mono pots. I used 15k resistors because I had them. I nominate myself for the ugliest, most haphazard, and free-ist. The pots, wires, and resistors are from an old & broken realistic PA amp that I got for free. The case and RCA jacks are from a crappy broken dvd player that was $15 new. It works just fine. Incidentally, this is the first thing I've ever made with my soldering iron. What a start, eh? :thmbsp:
 

Attachments

  • kdk_0167.jpg
    kdk_0167.jpg
    56.4 KB · Views: 233
  • kdk_0178.jpg
    kdk_0178.jpg
    47.6 KB · Views: 181
Last edited:
hi

just built a passive pre haller design using 100k alps pot sounding very good, i would now like to introduce a 6 way 2 pole rotary switch could anyone give me a step by step guide on how to do this
thanks
 
Rick Chinn offers some excellent information about designing and building your own passive attenuator on his website:

http://www.uneeda-audio.com/passive/preamp.htm

Note well the discussion of the input and output impedance of the volume control itself, as noted earlier by Ashok. For solid state amps with a 20K to 30K input impedance, a 5K pot is just about ideal, though harder to find than 10K.

BTW, he also has a link to the AES Laws for Audio Engineers, which I find amusing:

http://www.aes.org/sections/pnw/laws.htm

Cheers,

Otto
 
kriss said:
hi

just built a passive pre haller design using 100k alps pot sounding very good, i would now like to introduce a 6 way 2 pole rotary switch could anyone give me a step by step guide on how to do this
thanks
Click to expand...

You will connect the interior switch contacts to the inputs of your volume control. The respective outer connections on the rotary switches (check with continuity tester) will go to your input jacks.

I assume you won't switch input grounds, so just tie them together and to volume control and output grounds.

Cheers,

Otto
 
thanks for the reply,perhaps my question was'nt so clear, i am ok inserting a switch in a standard passive pre but the haller design is different only the output and earth terminals are used on the 100k pot and 11k resistors are used across the phono input and phono output, so just need to know where to insert switch
thanks
 
One channel shown; repeat for the other channel using contacts in the other pole of the 6 position switch.

6selector.jpg
 
You must log in or register to reply here.
Back
Top Bottom