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Till E. -- Passive preamp [message #40618] Wed, 12 March 2003 08:30 Go to next message
Vandough is currently offline  Vandough
Messages: 7
Registered: May 2009
Esquire
Hello all, I posted a little over a week ago to Mr. Till E. about his fried Foreplay and the volume control he put together to replace it. Mr. Till E. stated that the sound of the Goldpoint volume control was "better" in some ways than the Foreplay (at least with the Paramours). Knowing the following and popularity of the Foreplay. This cought my attention and I began looking around at the passive preamp designs and reading about them.

Well, in doing some searches I stumbled across a reference to the DIY Audio site (diyaudio.com) and there I found a "simple passive preamp" that is built from Radio Shack parts for about $20.00. I promply printed up the instructions and went to Radio Shack and bought the parts. Put the volume control together in a couple of hours and was very impressed.

Let me first say that I do not like the control of the attenuator. It has very poor control and gives a gain of 0 watts at 6:00 to about 50 watts or more at the 8:00 postition. In my opinion this is very poor. I do not know if changing the resistor values will change this at all, but this is the design that I followed.

Now the good part; by hearing (or not hearing) the simplified signal path. I am impressed, what we have here is a volume control, a couple resistors, some short length of wire (30awg RS magnet wire) and some RCA jacks. Now I understand the the following of the passive preamp. If this kind of sound can come out of a $20.00 box then I am sure that with higher quality parts that even better things will come.

I get more detail, more air, more dynamics because it is very quiet. Just music, no coloring of the sound. It will reveral the quality of the up and downstream components.

You should try it out just to see how simple and cheap it can be done. I will be making one with better parts down the road. I will likly use a Goltpoint or DACT stepped attenuator, some bette RCA's and maybe some different wire and resitors.

Till E. , thanks for getting me interested in this passive thing and I'm with ya on this one.

Adcom SLC 505 Passive Preamp [message #40620 is a reply to message #40618] Wed, 12 March 2003 12:30 Go to previous messageGo to next message
BrianG is currently offline  BrianG
Messages: 35
Registered: May 2009
Baron
Try finding an old Adcom SLC 505 passive preamp on eBay. The Adcom units of that time period were very well constructed. There is plenty of space "under the hood" to add any active electronics if you want an active/passive preamp combination. In fact there is a slide switch on the back of the unit that changes it from a passive preamp to an switchbox that could be adapted to switch from passive to active. The last one on eBay went for less that $40.00 here:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3011222048&category=14974

Good hunting!

Brian

Re: Adcom SLC 505 Passive Preamp [message #40636 is a reply to message #40620] Fri, 14 March 2003 04:41 Go to previous messageGo to next message
Vandough is currently offline  Vandough
Messages: 7
Registered: May 2009
Esquire
Thanks for the info, I kinda got the hankering for the DIY thing at this time.
google search [message #40638 is a reply to message #40636] Fri, 14 March 2003 09:10 Go to previous message
Sam P. is currently offline  Sam P.
Messages: 307
Registered: May 2009
Grand Master
for "build passive preamp" yields an article on the DACT company site that is good starter material. I've seen several DIY passive preamp schematics on the web over the years...one caveat was the power amp needing to be over 50K input Z, which leaves out most of my sand amps:) Sam
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