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Old 29th March 2012, 07:29 AM   #1
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Default Reduce Output Volume

I have a Jolida 302b amp that has been modified I bought six years ago. I just started to get into modifying my equipment. So I barely know what I'm doing. I decided to change the volume pot for the stock to a Goldpoint 24-step attenuator. I read on a site the stock one was 50K so I ordered one. Well when I opened up the machine it was a 100K pot. Will this make much of a difference? It is now louder with the knob point to the same area. Regardless of the pot I would only turn it up maybe a 1/4 before it is plenty loud. I'm in a fairly small room 6 feet away from the speakers. With the new attenuator I move it up 3 steps and it's loud enough at night through the CD Player. Through the computer I can get make finer adjustment by adjusting the computer output volume. Is there something I can do that will reduce the the level so that I will turn up the pot 7 to 10 to before it starts getting too loud. I'm think if I put a resistor somewhere that may work.
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Old 29th March 2012, 07:54 AM   #2
sesebe is offline sesebe  Romania
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Hello,

Can you post a schematic for you amplif?
Without a schematic it is dificuld to find a god answer to you questions.
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Old 29th March 2012, 08:13 AM   #3
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schematic here.

Volume control is a basic potential divider, so the 50k should not make a difference in real world application.

Only thing i can imagine is that the stepper is not a log or pseudo-log device...

If its really bugging you and you NEVER use 10, you could put a fixed resistor in the input leg - say, 20k... That will ensure you can never get to more than 5/7 of full volume as well as quietening down everything else (but by a smaller ratio)...
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Old 29th March 2012, 08:40 AM   #4
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by steven2583 View Post
Is there something I can do that will reduce the the level so that I will turn up the pot 7 to 10
to before it starts getting too loud. I'm think if I put a resistor somewhere that may work.
Hi,

Yes there is. Simply add a series resistor, 47K should be fine.

rgds, sreten.
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Old 29th March 2012, 09:33 AM   #5
DF96 is offline DF96  England
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Quote:
Originally Posted by steven2583
I just started to get into modifying my equipment. So I barely know what I'm doing.
It is much easier to ruin something than improve it, unless the original designer was incompetent or severely constrained by cost. You need to understand your equipment, so do a lot of reading before you switch on the soldering iron.
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Old 29th March 2012, 03:53 PM   #6
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I was digging around the goldpoint's website and I found a page that had some resistor recommendations to reduce the volume. It looks like the first 5 steps move from up by 10 dB, then 6 db, 5 db, 4 db, and then once past 10 o'clock it moves up in 2 db steps. So I will drop it down by 20 db and I will have a little better control on the volume.
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Old 29th March 2012, 06:01 PM   #7
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Now I'm looking for resistors and I notice they come in 1/4, 1/2, 3/4, 1, 2 watt. How do I know what part of a watt I need.

Goldpoint says I need a 44.2K and a 5.52K resistor. Any recommendiations?
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Old 29th March 2012, 07:24 PM   #8
DF96 is offline DF96  England
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For a normal line level attenuator 1/4W is fine.
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Old 29th March 2012, 08:18 PM   #9
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One possibility is just substituting the first two tubes with lower gain equivalents. 5751 for V1, maybe, and E180CC or 5965A for V2. Why attenuate more when you can just drop the unneccessary gain...

I've used both E180CC and 5965A in place of a ECC81/12AT7. It's basically almost a drop in replacement in most circuits, but has lower gain. The brightest side to this is that cheap NOS is available. Plus you don't have to heat the soldering iron at all.
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Old 29th March 2012, 08:55 PM   #10
DF96 is offline DF96  England
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Does the 302b have global NFB? If so, reducing valve gain won't affect circuit gain very much.
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