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My Redboy/Harry Haller Passive Attenuator

Rockyhill

Rockyhill

AK Subscriber
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Just completed my version of the Redboy/Harry Haller passive attenuator.

Alps Blue Velvet 100k pot
11K Shinkoh Tantalum film resistors
Connex RCA jacks
Solid Core Gold Plated "AU" 22.5Ga Wire
Hammond die cast aluminum case

Home made knob from 3/4" mahogony. Used a 1.75" hole saw, cut 2 pieces, glued togeter. Rubbed with tongue oil.

Case was painted with gloss black paint. That was a bitch since I don't like to use spray paint in the cellar and the garage is still cold here in Maine. Will repaint when the snow's gone and the black flies are in abundance!


It sounds great. Temporarily using it connected to 'Main In' on my 2235B. It will ultimately pair with a small tube amp, laptop and Sony XDRF1HD tuner.
 

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Nice work, how much was that case?

I have made a few of those for testing chip amps, the benefit is they don't add anything to the sound like a powered pre can, good or bad. you really hear the different characteristics between amp designs
 
Looks good!!

I used the exact same Hammond chassis, when I built my passive preamp a few years back.
I put in a pair of RCA jacks as inputs, and added an ON-OFF-ON switch to hook-up my Magnavox CD player and Sansui tuner.
Plenty of room in that Hammond chassis.

Steve
 
Hammond case

AltecDarpa said:
Nice work, how much was that case?

I have made a few of those for testing chip amps, the benefit is they don't add anything to the sound like a powered pre can, good or bad. you really hear the different characteristics between amp designs
Click to expand...

The case was $24.08 US (plus shipping) through Mouser. I wanted the black powder-coated but it was back-ordered. I should have waited. Painting was such a PITA!
 
Tone vs no tone

I know this is a very controversial subject, but just spending the weekend using this confirms my opinion that having tone contol is important to me. My CD collection reveals the vast differences in sound quality among discs made from 60's and 70's music compared to 80's, 90's and newer. Maybe it's my 50's vintage ears, but that's what I believe.

2013 edit: I find I don't need tone when the rest of the system is reproducing sound the way I like it.
 
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looks great :thmbsp:

i am wondering how far the volume knob gets turned for quiet or loud settings? how does this compare to the preamp it replaced?
 
roger2 said:
looks great :thmbsp:

i am wondering how far the volume knob gets turned for quiet or loud settings? how does this compare to the preamp it replaced?
Click to expand...

For low volume listening it's at ~8 o'clock; high level it's at 10-11. All sources are connected to a Grant TubeDAC-11, which is functioning as a pre. I was using that exclusively as the volume control but due to an imbalance of output at low levels from the DAC I added the attenuator. (When the DAC volume is at 7-9 the left channel is lower than the right. Grant says this is expected behavior). So now I set the DAC volume at 1-2 o'clock.

As far as sound quality, I had been using a 20+ year old Adcom GTP-500 II. I considered recapping but upon opening the case I realized it would be quite the project due to the complexity of the various PCB's. I find the sound more open and expansive with the Adcom removed. Voices and strings are more natural. I use the tube-out from the DAC and find it a better match for my ST-35. I tried the SS-out but it was brighter - most likely due to the EMITs in the Infinity's.

I had been thinking about building a new tube pre but I'm quite happy with this setup - for now, anyway. You know how this hobby works
 
mhedges said:
Very nice!

Can you post a wiring diagram?
Click to expand...

series_shunt_pot_schematic.JPG


Have also posted this schematic in my original post linked to by Redboy.
 
ashok said:
series_shunt_pot_schematic.JPG


Have also posted this schematic in my original post linked to by Redboy.
Click to expand...

Thanks!

So since the pot is just being used as a variable resistor, does it matter which end you connect, other than which direction you have to turn the volume knob?
 
vinylkid58 said:
Thanks for bumping this up. I built one of these yesterday, using some parts on hand. Sounds great with the CD player, but doesn't work as well with the phono stage.

jeff
Click to expand...

You'll need a phono preamp. This is just a line level attenuator.
 
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