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Author Topic: Color Me Transparent  (Read 4744 times)
FredT300B
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« on: January 22, 2007, 03:48:47 PM »

That's what my upstairs system is saying after I replaced the tube amp with a simple 25K ohm Goldpoint attenuator in a gray Hammond chassis. I still need to "Wardsweb" it with a wood front, etc., but the sound is really good for the $140 cost. It's not a good match for the Paramours because their input sensitivity is so low, but with the high sensitivity Monarchy Class A amps I'm listening with the volume set about halfway.  Grin

For those who haven't been following Goldpoint's progress with their stepped attenuators, the 1% Dale resistors on their older attenuators have been replaced with 0.1% surface mount devices on their new Mini V design. The SM devices also permit a smaller size that's not much bigger than an Alps blue velvet pot.

Look here for a picture of the just completed "passive" preamp.

http://fredt300b.smugmug.com/gallery/132868#124847918
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AliG
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« Reply #1 on: January 22, 2007, 09:56:49 PM »

Fred,
  Nice job!!!!  You have just made a passive equivalent to a $1000 Placette!!! I need to go to Home Depot to get some soldering gears fast. Grin

Rgds
barry
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FredT300B
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« Reply #2 on: January 23, 2007, 04:44:24 AM »

Thanks. As one would expect, it has better synergy with some amps than others. I would want to use a tube preamp instead with a bright mid-fi solid state amp, but with my Assemblage 300B tube amp that already sounds "tubey" it's perfect.

I built it for use with my class A zero feedback Monarchy SM-70 Pro's, that have a very sensitive input and 100K input impedance. With these it's much better than the tube preamps I was using, all of which have 20dB gain and must be set at the lowerst possible levels. With the tube preamps and 94dB sensitive speakers I was hearing too much tube sound. With a passive the system is dead quiet.
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FredT300B
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« Reply #3 on: January 23, 2007, 07:36:15 AM »

I need to go to Home Depot to get some soldering gears fast. Grin
barry

Barry, if you're serious about doing some DIY, this passive is a good place to start. I got a new MCM Electronics sales flyer in the mail, and the Tenma adjustable soldering station #21-7945 is on sale for $28.89. It's best to get a heat-adjustable soldering tool that will work with fine circuit boards and large point-to-point connections too. You should also get a smaller tip to complement the one that comes with it.

I have an extra 7X5X2 Hammond chassis on hand with the RCA's already installed, and I have some extra alder wood to make a front panel, all of which you can have. I'll even trim and install the wood front panel and drill the hole for the Goldpoint attenuator. Of course you will have to solder the attenuator yourself, or it won't sound nearly as good to you. (I call that the proud momma syndrome - our moms saw beauty and intelligence even in ugly amd dumb babies like we were).  Roll Eyes

If you order a Goldpoint attenuator you will need to consider the input impedance of the amp you will be using with it. If it's 50K or more a 25K attenuator will work best. If it's less than 50K you probably should get at 10K.

Here's the final version, but with the front panel not yet oiled.
http://fredt300b.smugmug.com/gallery/132868#124989633
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AliG
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« Reply #4 on: January 23, 2007, 08:16:32 AM »

I just checked MCM website.. out of stock!!! Huh
 

I need to go to Home Depot to get some soldering gears fast. Grin
barry

Barry, if you're serious about doing some DIY, this passive is a good place to start. I got a new MCM Electronics sales flyer in the mail, and the Tenma adjustable soldering station #21-7945 is on sale for $28.89. It's best to get a heat-adjustable soldering tool that will work with fine circuit boards and large point-to-point connections too. You should also get a smaller tip to complement the one that comes with it.

I have an extra 7X5X2 Hammond chassis on hand with the RCA's already installed, and I have some extra alder wood to make a front panel, all of which you can have. I'll even trim and install the wood front panel and drill the hole for the Goldpoint attenuator. Of course you will have to solder the attenuator yourself, or it won't sound nearly as good to you. (I call that the proud momma syndrome - our moms saw beauty and intelligence even in ugly amd dumb babies like we were).  Roll Eyes

If you order a Goldpoint attenuator you will need to consider the input impedance of the amp you will be using with it. If it's 50K or more a 25K attenuator will work best. If it's less than 50K you probably should get at 10K.

Here's the final version, but with the front panel not yet oiled.
http://fredt300b.smugmug.com/gallery/132868#124989633
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Wardsweb
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« Reply #5 on: January 23, 2007, 10:13:58 AM »

Other online electronics shops:

partsexpress.com

digikey.com

mouser.com
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AliG
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« Reply #6 on: January 23, 2007, 10:18:08 AM »

I found one.. cheap..  Grin

http://www.skycraftsurplus.com/index.asp?PageAction=VIEWPROD&ProdID=880

Looks just like the Tenma.. should I pull the trigger??

Apparently, huge dealership markup is not only confined to audio industry..LOL.
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FredT300B
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« Reply #7 on: January 23, 2007, 04:56:00 PM »

I found one.. cheap..  Grin
Looks just like the Tenma.. should I pull the trigger??

Yes, for $20 what do you have to lose?
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