PPA and Gain Switch
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ipodstudio

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OK, I've been listening to the full monty almost constantly since I got it and my first impression of the gain switch is very positive. I'm only using the HD 650s with this amp, yet even with these it's fun to have when listening late at night at very low volumes. It just puts the punch back into the music at those low volumes. I think I'll only use it for about 10% of my listening, possibly less, but it's darn useful to have.
If you use it at higher volumes I don't personally enjoy the affect as it becomes too in ya face, but some might. Just some thoughts so far...
 
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guzzler

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do you mean the bass boost? that's different to a gain switch

g
 
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Oddball

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ipodstudio got a special "Full-Monty" PPA that has a gain switch plus all the other add-ons in his sig and we're all jealous.
 
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ipodstudio

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Quote:

Originally Posted by guzzler
do you mean the bass boost? that's different to a gain switch

g



Nope, the full monty doesn't have bass boost; it was replaced with a gain switch...


Look in my signature..
 
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ipodstudio

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Quote:

Originally Posted by Oddball
ipodstudio got a special "Full-Monty" PPA that has a gain switch plus all the other add-ons in his sig and we're all jealous.


YES!! I knew one day I would make someone jealous!!
 
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guzzler

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could you explain what exactly it's function is? to say you use it at low levels to put some punch back in makes it sound like a bass boost to me, all a gain switch will do is change the output volume for a given input, ie putting more punch as you put it would be cranking up the volume??

cheers

g
 
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ipodstudio

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Quote:

Originally Posted by guzzler
could you explain what exactly it's function is? to say you use it at low levels to put some punch back in makes it sound like a bass boost to me, all a gain switch will do is change the output volume for a given input, ie putting more punch as you put it would be cranking up the volume??

cheers

g



It just brings the sound forward, seeming to magnify the content. It feels like a voice that was previously stood right in front of me is now whispering right in my ear and stops me wanting to crank the volume up in order to hear more detail.
 
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doobooloo

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Are you sure the bass boost is "on" by default?

Changing the gain shouldn't affect the sound signature unless bass boost is on. My PPA has both gain switches and bass boost, and without bass boost on, the gain switch merely "lowers" the volume level, but if the bass boost is on the relative level of bass boost becomes much more powerful at low gain.
 
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adhoc

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sounds more like it has something to do with adjusting gain for high/low impedance headphones.
 
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aos

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An actual gain switch would just change the amplification factor of the amplifier. Meaning, you would get the same effect by rotating your volume control. The idea is to allow finer volume adjustment by being able to exercise the whole range of the volume control instead of just a small portion. For example you plug in low impedance phones and find that only first 1/3 of the volume control range is usable as it becomes super loud. Gain switch could be set to reduce the gain and now you'd be able to use volume control all the way up to, say, 80%. That's all it is. It would not change the sonic signature of the amplifier at all. From your description it sounds like it's not a gain switch. Perhaps impedance switch? Adding a resistor in series with output?
 
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ipodstudio

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Quote:

Originally Posted by aos
An actual gain switch would just change the amplification factor of the amplifier. Meaning, you would get the same effect by rotating your volume control. The idea is to allow finer volume adjustment by being able to exercise the whole range of the volume control instead of just a small portion. For example you plug in low impedance phones and find that only first 1/3 of the volume control range is usable as it becomes super loud. Gain switch could be set to reduce the gain and now you'd be able to use volume control all the way up to, say, 80%. That's all it is. It would not change the sonic signature of the amplifier at all. From your description it sounds like it's not a gain switch. Perhaps impedance switch? Adding a resistor in series with output?


aos, you'r exactly right. It is just a gain switch and does exactly what you said. It just feels like it brings the music forward to me. I need to write clearer and try to explain better but it's been a long week
 
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doobooloo

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Quote:

Originally Posted by ipodstudio
It just feels like it brings the music forward to me.


But like aos said... the thing is, technically it really shouldn't even feel like it's different... unless the actual volume levels at the two different settings are different... Are you sure there isn't something more?

The thing is with my PPA the gain switch does exactly nothing other than change the volume level... Well, there is the noise issue since I am using the crappy Elpac wallwart...
but other than that, I can't really hear a difference.

But then, who am I to say what your amp should sound like...
I keep forgetting that this is hi-fi business we're all in.
 
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fewtch

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Quote:

Originally Posted by doobooloo
But like aos said... the thing is, technically it really shouldn't even feel like it's different... unless the actual volume levels at the two different settings are different...


I thought about this awhile, and am not so sure. With a higher gain, the pot is attenuating more voltage (am I correct?) to output the same volume level. Couldn't this theoretically affect the sound in some way? It's an analog control, subject to some irregularities at different settings. Also, anything in the circuit between the gain resistors and headphone jack is subject to a higher voltage.
 
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doobooloo

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Quote:

Originally Posted by fewtch
I thought about this awhile, and am not so sure. With a higher gain, the pot is attenuating more voltage (am I correct?) to output the same volume level. Couldn't this theoretically affect the sound in some way? It's an analog control, subject to some irregularities at different settings. Also, anything in the circuit between the gain resistors and headphone jack is subject to a higher voltage.


Hmm... you have a good point there. The pot plastic/carbon resistive film isn't the most hi-fidelity material out there, so yeah having more of that stuff directly in the signal path would probably be detrimental to the sound?

I don't know about the gain resistors being subject to higher voltages though - aren't resistors (especially the higher-grade types that are used by many DIYers) pretty consistent across the voltage range that we're interested in?

But yeah... interesting point... maybe I should do some A/B-ing with my own PPA...
 
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adhoc

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Quote:

Originally Posted by ipodstudio
aos, you'r exactly right. It is just a gain switch and does exactly what you said. It just feels like it brings the music forward to me. I need to write clearer and try to explain better but it's been a long week



sounds like the midrange got boosted a little.
 
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