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Old 25th May 2003, 10:36 AM   #1
Nuuk is offline Nuuk  United Kingdom
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Default Increased gain for IGC

Given that the original Gaincard amp has a reputed gain of around 30, has anybody yet tried increasing the gain on the IGC higher than 20?

Or does anyone have any comments/caveats on trying this?
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Old 26th May 2003, 03:23 PM   #2
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Red face The gain

Hi Nuuk,
Long time no see.
Are you sure the Gaincard has a gain of 30?
My Gainclone, based on the Thorsten schematic, with some personal touches,
has a gain of 23 (220k / 10k + 1).
Anyway, my Gainclone seams to have exactly the same gain as the power amp seccion of my Nad amp.
So, it seams a more or less standard value for a power amp.
Even as it is, with the remote control the volume pot is very sensitive, as it always was.
I don't feel the need for more gain.
Keep in mind that pushing the gain also brings more noise, but you may not notice it.
If you use the Gainclone as an integrated amp (with volume pot and source selector), that may be another story and maby you would need a little more gain to go with some source components.
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Old 26th May 2003, 03:44 PM   #3
Nuuk is offline Nuuk  United Kingdom
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Hi Carlos, we must have been typing posts to each other at more or less the same time!

I am sure I read somewhere that the Gaincard had a gain of 30. I just wondered what people's thoughts were about trying a higher gain. Of coursse, the Gaincard is a non-inverting amp if that makes any difference!

The gain in my Arcam A60's is 27. On my own GC's I do sometimes feel the need for more volume on some quiet CD's BUT I will reserve judgement until I change the attenuator to one with values that don't 'upset' the gain of the amp.

I am also starting out on a new GC with a buffer and filter between volume control and amp based on the work of Joe Rassmussen and Pedja.
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Old 27th May 2003, 12:10 AM   #4
Asen is offline Asen  Bulgaria
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Nuuk

I'm interested in what results you will achieve with the buffer GC and the filter. Please post them here after that.

I tried a tube pre but my GC sounds worse with it. And it sounds rather soft even without filtering the highs. Unfortunately now I cannot find the time for experiments with buffers.
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Old 27th May 2003, 08:11 AM   #5
Nuuk is offline Nuuk  United Kingdom
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Quote:
I'm interested in what results you will achieve with the buffer GC and the filter. Please post them here after that.
Hi Asen, I will certainly post any results to this forum.

Meanwhile, if you have not done so already, you could read of Pedja Rogic's experiments with a FET buffer and filtering on HIS SITE .
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Old 27th May 2003, 09:46 PM   #6
Asen is offline Asen  Bulgaria
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Thanks Nuuk

I've read everything appeared in the net so far. The problem is the conclusions are controversial.

Quote:
However, bare 'clone has some smoothness which buffered gainclone at that moment partially still missed
So, I'll be waiting for your comment to be posted.

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Old 28th May 2003, 01:57 AM   #7
Pedja is offline Pedja  Serbia
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Hello Asen,

Quote:
Originally posted by Asen
I've read everything appeared in the net so far. The problem is the conclusions are controversial.
quote:
However, bare 'clone has some smoothness which buffered gainclone at that moment partially still missed
This is ok, now just keep reading further that page and you will find…

Now seriously, did you mean conclusions are controversial over the net or inside that my page? In fact, unfortunately, there are not much similar experiments around. So, since I guess you meant on my page, you should know, I posted my finding as I made experiments. Now, and that explicitly reads at my page a few times, I am very satisfied with what I made. That is the result of the process which was partially exposed publicly, and for now I will not hide how that process looked like.

In essence, there were two important points in making something better than thing I was started from. One was the low pass filtering and second was the buffer’s power supply (firstly I relied on the current sourcing only and partially that was mistake). I described what is necessary (minimum) in both areas to make the amp better than bare ‘clone. You have pictures, you have a schematic, you have a few different options for the filter, you have my claim it sounds better and you can believe it or not, but what is controversial?

Quote:
Originally posted by Asen
I tried a tube pre but my GC sounds worse with it. And it sounds rather soft even without filtering the highs.
More or less, I can agree. I also tried my tube preamp (used like preamp) and was not satisfied. But all this is not about the preamp, this is about the buffer which goes after the pot and before the output chip.

This is important… Low pass filter is intended exclusively to prevent unwanted behavior in the ultrasonic and not to filter the highs. This lpf does not work in the way it makes the tonal balance more acceptable or something like that (and hence somewhere is good, somewhere it is bad). High frequency roll-off is unwanted consequence of this filtering. Making of this lpf is mostly a matter of compromise: more effective filter sonically relates to the better soundstage and resolution, but yes, the sound also becomes more natural (i.e. naturally relaxed – less nervous); at the other side, things should be kept relatively proper in the frequency domain. Once more, the treble roll-off is not intended consequence. (Please note that the low passing filtering which works good here is not the rule that applies to the amps generally.)

And if one is scared of treble roll-off (in fact I am too), may I suggest low pass filter with the slope entirely over the audio range (in fact it was the first lpf I tried); difference should be audible enough.

About mentioned unwanted behavior of the chip, check:
http://www.diyaudio.com/forums/showt...564#post164564 , it is described at the end of the post #36 and in the post #37.

Pedja
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Old 28th May 2003, 08:23 AM   #8
Nuuk is offline Nuuk  United Kingdom
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Quote:
I've read everything appeared in the net so far. The problem is the conclusions are controversial.
Hi Asen, I'm not sure where you come from or if English is your native language (that's not a criticism). I would replace the word 'controversial' in your statement with 'conflicting'!

The problem is that we are all working with different equipment. I don't believe, unless we all use exactly the same hi-fi in standard size rooms, and listen to the same music (how boring) that you will see anything but 'conflicting' reports!

Also, DIY hi-fi is not an exact science and there is a lot of subjectivety involved.

The Gainclone design is a good example of this. Even with so few components we have still had thousands of posts debating the best method of reducing DC offset, whether to use a resistor on the output, whether to use a Zobel network, and now, whether a buffer is useful, if so what type, should we use filtering, if so how much. And I bet that will continue for some time to come!

I agree with you that sometimes it can make the hobby rather frustrating but then again, if it was as easy as following an exact 'recipe', it wouldn't be so much fun!

The only thing you can rely on is trying out something for yourself in your own system. And even then, you won't always be able to be sure if a modification is an improvement or not!

As somebody not trained in electronics, I say thank goodness for the likes of Thorsten, Pedja and Joe Rassmussen. But I don't expect them to 'spoon feed' me solutions. They show the way and it's up to us to use their information as best we can.

Yes, the amount of conflicting information can be confusing at times. But that's the price we pay for having it in the first place!
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Old 28th May 2003, 10:19 AM   #9
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Default There are no two equal Gainclones

And that's why we give our impressions, but they are always related to our particular Gainclone.
It has few components, but they make a difference in the final result.
The way you connect everything, where you place the components (the layout), the components you use, the PSU...
That's not so easy to generalize.
It's not a commercial product.
Everyone makes it different, even with the same schematic.
But that's the beauty of DIY.
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Old 28th May 2003, 10:13 PM   #10
jkeny is offline jkeny  Ireland
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Default Increased gain for IGC

What are the ramifications of the 1M feedback resistor J. Rasmussen uses in his IGC - he suggests lower feedback - has anybody tried this? What results.?
Pedja - good to hear the lp filter works. Anybody else tried similar?
John
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