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Old 10th September 2008, 11:58 PM   #1
ojcool is offline ojcool  United States
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Default What stereo Pot for Gainclone?

Can anyone recommend a good stereo pot for volume control for a gainclone? How much affect on sound does Pot selection make?
I will giving this amp signal from a laptop or Ipod if that makes a difference.

It's just a brianGT two channel 3886 with the snubber.

I'm just looking for a really good sounding amp for casual listening to a variety of music. Prob run a M T M style speaker. Maybe a powered sub as well.
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Old 11th September 2008, 12:27 AM   #2
DC Dave is offline DC Dave  United States
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I have had good luck with this one from Jaycar. The affect on the sound is similar to any of the components in the circuit, and is very subjective. You might also want to try the ~$5 Alps pot from Radio Shack for comparison.

http://www1.jaycarelectronics.co.uk/...Max=&SUBCATID=Click the image to open in full size.
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Old 11th September 2008, 12:31 AM   #3
lineup is offline lineup  Sweden
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Is it Inverted Gainclone ??
or the 'standard' from National datasheet NON-Invereted config ??



For the inverted, the Thorsten Loesch variant, that was very popular, you can get issues using one pot in front of input

For non-inverted this issue may not be quite as big.

Any case, when you do put one pot in front of one power amplifier input, you have to consider the in & out impedances.
As bringing another 'resistor' into play, in this case the potentiometer, will effect the signal & often frequencies, that do reach the input transistor.

To overcome this, many Gainclone builders use Buffered Input of the power chip.
This is seen BOTH in Tube Buffered gainclones and in JFET Buffered gainclones

Some more good reading here, at Nuuk website:
Building a buffered Gainclone chip amp
Building a *vale-buffered Gainclone chip amp

* should read Valve-Buffered Gainclone = Tube Buffer

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Lineup
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Old 11th September 2008, 12:41 PM   #4
AndrewT is offline AndrewT  Scotland
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Hi,
a buffer added to the source output that can drive any combination of cable and attenuation pot helps sound quality.
A buffer at the input of the chipamp allows any attenuation pot to perform without having a deleterious effect on the input of the chipamp.
Omitting either of these buffers will make selection of the attenuator and the design of the chipamp considerably more onerous. Many more compromises must be accepted if you go this route in search of improved sound quality.
Read Peter Daniel for his views on minimalist interconnection.
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Old 12th September 2008, 08:03 AM   #5
ojcool is offline ojcool  United States
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What other option do I have to control to volume? These are the Non Inverted 3886 kits from BrianGT. I am running just the one power supply but I have another power supply kit. Are you guys saying that I should use one power supply for each of the chipamps but use the same transformer to power each power supply?

I'm an electronics idiot and can say I don't really understand how any of this works, I just wanted to build a good sounding amp. The BrianGT kit instructions talk about putting a Pot on the input to control volume I did wonder why you could not put the pot on the feedback circuit instead of the feedback resistor and use that to control the amp gain and therefore the volume.

Either way if someone could just tell an electronics idiot what exactly to do to finish this amp project I would really be in your debt. I thought my only option was to use a pot on the input.
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Old 12th September 2008, 08:20 AM   #6
AndrewT is offline AndrewT  Scotland
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read the datasheet.
The stability of the chipamp is affected by the gain.
National say it is stable if the gain is over 10 (+20dB).
That would be the minimum gain you could use for minimum volume.
It would be just 6dB to 12dB below maximum.
= broken eardrums or broken speaker or broken amplifier or any combination thereof!
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Old 13th September 2008, 11:59 PM   #7
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ALPS - 27

10$/Each
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Old 14th September 2008, 02:53 AM   #8
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Thumbs up nobles/Alps

I would use Alps/Nobles potentiometers.
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Old 15th September 2008, 11:02 AM   #9
ojcool is offline ojcool  United States
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Well I guess I decided not to use a Pot on the input if I don't have to.
If I'm using an Ipod to provide my signal and it has a volume control, I can just use that correct?


Also, the torid transformer I have has 16.2v secondaries. That will still work right, it just won't have as much wattage output? I don't need it to be exceptionally loud. Or do I need to get another transformer?


I was going to hook it up like this. Apex Jr Torid hookup
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Old 31st July 2009, 01:40 PM   #10
gychang is offline gychang  United States
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Quote:
Originally posted by DC Dave
I have had good luck with this one from Jaycar. The affect on the sound is similar to any of the components in the circuit, and is very subjective. You might also want to try the ~$5 Alps pot from Radio Shack for comparison.

http://www1.jaycarelectronics.co.uk/...Max=&SUBCATID=Click the image to open in full size.

small for stereo looks ideal to me but is there a source in US?

gychang
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