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Go-Vibe V7 arrived! - Page 4

post #46 of 101
9/19/07 at 3:41pm
Thread Starter 
Quote:
Originally Posted by dw6928 View Post
I spent a couple of minutes a/b the Move and the GV7. The Move is superiorby a bit, better warmth, bass and engaging soundstage but only a bit. The amp section of the Move is very special which shows how good Norms V7 is. The V7 blows away all of my earlier versions of his amp. Like twice as good as V5. I keep looking down at it in amazement. It has great dynamics and punch, terrific clarity and well rounded bass, it powers my D2000s at 10:00, effortlessly. It is really unfortunate they are unavailable to others. Does anyone remember what the battery life expectancy is on a regular 9V battery?
See, I would probably disagree with that. I haven't heard the Move but it uses the same AD8610 opamps that were in the V6. To me, it sounded very bloated in the bass/midbass, whereas the AD8397 have a more neutral and accurate response. I guess it's all personal preference though.

One thing I did notice about the V7 last night.... It's transparency really shines only when plugged into the 12V adaptor. As soon as you unplug the adaptor and run on the rechargable battery, the sonic transparency drops a bit, I'd say about 35%. The details and air close in a bit, as well as the soundstage. But I almost always use the adaptor anyway.
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post #47 of 101
9/19/07 at 3:51pm
The Move uses dual opamps and whatever Jan Meier did with the rest of
the board makes the amp (to me) sound a good bit better than the GV7 (which
I have grown very, very fond of). Try to find one and a/b them. I think you will see the difference.
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post #48 of 101
9/19/07 at 5:30pm
Could anybody resolve the type of the TI op-amp in the GV7? I can't read it from the picture. I guess this part does not tolerate voltages below 9V which appear when the battery discharges some. AD8397 can work from 3V but the TI definitely not. It's a good step forward anyway, if a portable amp gets the AD8397. Probably the first one to offer this was Dr Xin.
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post #49 of 101
9/19/07 at 5:44pm
Quote:
Originally Posted by majkel View Post
I guess this part does not tolerate voltages below 9V which appear when the battery discharges some.
What? What gives you that idea? I don't think any builder would put an y opamp in with a spec'd minimum voltage of 9V, like an OPA2107 for example.

It looks like the OPA690.
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post #50 of 101
9/19/07 at 7:23pm
Thread Starter 
Quote:
Originally Posted by dw6928 View Post
The Move uses dual opamps and whatever Jan Meier did with the rest of
the board makes the amp (to me) sound a good bit better than the GV7 (which
I have grown very, very fond of). Try to find one and a/b them. I think you will see the difference.
You might be right. Are you using the 12V adaptor with the GV7 though? There is a big difference in quality WITH the adaptor and WITHOUT the adaptor. The way I've rated it is WITH the adaptor, which isn't always a good thing considering it is a portable amp.

I won't be getting a Move. As soon as I get my tax refund, I will be getting an Opera, which I'm sure is a good deal better than both.
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post #51 of 101
9/20/07 at 10:00am
Quote:
Originally Posted by holland View Post
What? What gives you that idea?
I saw many bugs in DIY designs publicized worldwide.

Let's assume it's OPA690. This means you have 310mA per channel capability, and 190mA capable ground channel. Does it make sense?
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post #52 of 101
9/20/07 at 12:31pm
Quote:
Originally Posted by IPodPJ View Post
You might be right. Are you using the 12V adaptor with the GV7 though? There is a big difference in quality WITH the adaptor and WITHOUT the adaptor. The way I've rated it is WITH the adaptor, which isn't always a good thing considering it is a portable amp.

I won't be getting a Move. As soon as I get my tax refund, I will be getting an Opera, which I'm sure is a good deal better than both.
No 12v adapter here. I have a Heed/Microdac for non portable issues so I am using 9v only. I found with the Move that the 12v adapter was negligible at best in increasing s/q. That may be very different with the GoVibe. You are moving not up the ladder but to another playing field with the Opera. I have heard it. It is nothing short of magnificent. Good luck with it.
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post #53 of 101
9/20/07 at 1:13pm
Quote:
Originally Posted by dw6928 View Post
No 12v adapter here. I have a Heed/Microdac for non portable issues so I am using 9v only. I found with the Move that the 12v adapter was negligible at best in increasing s/q. That may be very different with the GoVibe. You are moving not up the ladder but to another playing field with the Opera. I have heard it. It is nothing short of magnificent. Good luck with it.
I've never heard any difference in sound quality with or without the 12v adapter with any portable amp. I bet anyone who claims otherwise already expects the result and will fail a double blind test. Even with my stax sr001, the adapter only makes the sound louder, not better.
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post #54 of 101
9/20/07 at 2:06pm
Quote:
Originally Posted by majkel View Post
I saw many bugs in DIY designs publicized worldwide.

Let's assume it's OPA690. This means you have 310mA per channel capability, and 190mA capable ground channel. Does it make sense?
What's that got to do with 9V, as you stated in your post. You're going off on a different tangent with the reply.

Edit:

I don't know the full specs of the capabilities. It's not published. First off, AD8397 @ 10V outputs a max of 250mA with a 12ohm load, and it might linear drop from there. I haven't been able to find the graph. OPA690 sinks 190mA with a 100ohm load. It needs to sink the current that the headphones consume. It's *plausible* that headphones won't use 250mA at 100ohms, nor at 16ohm. What the OPA690 sinks with a 16ohm load, I don't know. I would need to put a test jig to test it, but I don't have equipment that is accurate enough right now. I will get to that point in time, but it's not in my possession right now.

Since you've seen so many bugs with DIY designs, why don't you post about it in the DIY section? If you know something you should share it instead of intimating issues and keeping quiet. The DIY community should want to know. It's possible that people in the DIY community have tested this. Again, share.
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post #55 of 101
9/20/07 at 2:24pm
I did a quick calc of P = I^2 R. AD8397 outputs 1W. OPA690 sinks 3W. So, no, I don't immediately see a problem. Again, it depends what the actual characteristics are. OPA690 also sinks a short circuit current of 250mA. Given those, I can probably linearly interpolate the 16-ohm value, assuming it is linear, but I won't.

If you know more, please follow up.
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post #56 of 101
9/20/07 at 2:25pm
Quote:
Originally Posted by holland View Post
What's that got to do with 9V, as you stated in your post. You're going off on a different tangent with the reply.
There is no issue with the OPA690 (I belive this is it) and voltages as low as 5V. I thought you realized that I have read the datasheet. Guys wrote that the amp works better from 12V than 9V so I posted my guess. It's no longer applicable.

Regarding my "bugs" remarks, I posted my suggestions regarding PINT and PIMETA at least twice. A guy was asking about PIMETA tweaks so I answered. I guess there haven't been any new posts since that time. Regarding my own design, I think I will reveal it someday but not at this time. It's still evolving and getting better because of some ideas that I come to from time to time.

If we talk about current efficiency - your assumptions might be right but there is audibly better drive when you use 310mA against 190mA op-amp, and I'm not talking about the sound signature as commonly understood. I tested OPA2690 a couple of months ago against AD8397. Besides the fact that OPA2690 for normal operation on the channels has to be pretty well compensated against offset, it pushed audibly less power to PX100's, save bigger cans.
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post #57 of 101
9/20/07 at 2:29pm
Quote:
Originally Posted by majkel View Post
There is no issue with the OPA690 (I belive this is it) and voltages as low as 5V. I thought you realized that I have read the datasheet. Guys wrote that the amp works better from 12V than 9V so I posted my guess. It's no longer applicable.
I added some on edit, but we're getting off topic for this thread. Interesting discussion though, but more befit for DIY section. To recap, I don't really see an issue at this point in time. I would need real world characteristics to see, as maximums may not be achieved. If you do, please explain.

I see, wasn't sure where the 9V came from. I don't really know what you read or haven't.

Edit: Oops, it looks like when I hit quote it was different that what I read, so ignore.
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post #58 of 101
9/20/07 at 2:50pm
Quote:
Originally Posted by majkel View Post
Regarding my "bugs" remarks, I posted my suggestions regarding PINT and PIMETA at least twice. A guy was asking about PIMETA tweaks so I answered. I guess there haven't been any new posts since that time.
I'll search for it. I honestly haven't paid much attention to PINT and PIMETA. It can be considered, before my time in terms of awareness of these designs.

Quote:
Originally Posted by majkel View Post
If we talk about current efficiency - your assumptions might be right but there is audibly better drive when you use 310mA against 190mA op-amp, and I'm not talking about the sound signature as commonly understood. I tested OPA2690 a couple of months ago against AD8397. Besides the fact that OPA2690 for normal operation on the channels has to be pretty well compensated against offset, it pushed audibly less power to PX100's, save bigger cans.
I'm not sure I understand. What do you mean by "audibly less power" and "audibly better drive"? Power should be measurable on the load. I'm not sure how I could qualify that audbily, I would think it would clip in some form or overheat the opamp(?). I don't have a PX100. I would love to pull some figures, but I don't have the test equipment and jig set up for it. Since you're designing your own part (for sale I presume?) you may have the necessary equipment already.

I look forward to see what you unveil.
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post #59 of 101
9/20/07 at 3:54pm
@holland, I see you prefer maths so, assuming AD8397 might go as high as 4.5V peak from 12V +- power supply, on 16 ohms you can sink/source:
4.5V / 32 ohm = 140mA, regardless it's loud, crazy, and so on... People might do what they want and have inefficient headphones.
... having 2 channels you need 2 * 140mA = 280mA sink/source from the ground channel, unless you build a ground channel railed with capacitors on the output and make it's bandwidth DC only. That's not great to make it so slow.
Regarding "audible" - just try and answer yourself. It's a fact that when you get close to the upper limits of a part, the distortions rise like hell and dynamics disappear.

I have to agree with one statement anyway
Quote:
we're getting off topic for this thread.
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post #60 of 101
9/20/07 at 4:07pm
Quote:
Originally Posted by majkel View Post
Regarding "audible" - just try and answer yourself. It's a fact that when you get close to the upper limits of a part, the distortions rise like hell and dynamics disappear.
LOL, no thanks. I understand the distortion at the limits. I'll wait till I get measuring equipment. That's way too loud for me to even try to listen for distortion or I would need to find some really inefficient headphones. My most inefficient pair are MB Quart QP55x headphones, which really aren't that bad for efficiency.
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