PINT Observations
Mar 29, 2006 at 2:00 AM Thread Starter Post #1 of 103

darkisz

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OK, I'm sure there are a few people chomping at the bit for some user feedback on the PINT. I put on together on 3/26, so I guess I'll take a stab at it...

Please be warned, I do not have 'Golden Ears' and my comments on the sound are just my opinions...but first I'll start with comments on the build.

Having never tried SMD before the PINT, I made sure to view Tangent's excellent video, and warmed up by mounting some SOICs on Browndogs. I was nervous, but it ended up being easier than I anticipated. I was using a Weller WP25 with a ST5-ND tip. I also picked up some quality tweezers that I believe made everything much easier.

Parts were almost straight off Tangent's list, with most components ordered from Digi-Key, I got resistors and case components from Mouser. I chose the 560uf cap for the electrolytic, and I mis-ordered the 75ohm resistor for R1 (got750k
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) so I substituted a 100ohm. I used 2x8397 for opamps. I set the gain for the default value of 6. I used 2x GP 8.4v/170mah batteries.

Casing went pretty smoothly. I used a Penguin Mint tin and drilled with a stepped drill bit. It ended up looking pretty much like the pics on Tangent's page, with the exceptions that I mouned an LED next to the volume knob and there's more slack in my wiring.

Pics (for those that didn't see it in the 'Post your Builds' thread):



So, how does it sound? Again, I can't stress enough that I don't consider myself qualified to give an accurate answer to this question. However, I'll try to express my opinion sufficiently. Equipment used for comparisons was 320kb MP3s from my Nano with SIK line out, and dt-770-80s for my comparisons against a C-moy with gain of 7 and the Hornet on high gain setting.

Compared to a C-moy with 2132 opamp, the PINT sounds great. The C-moy sounds thin and there is very little weight behind the notes. The PINT delivers tighter and better sustained bass, and the highs in the PINT are considerably smoother. Decay sounds more natural as well. The one place where the C-moy won was the noise floor. I was surprised how much hiss came from the PINT when I didn't have music playing. With lower impendance cans (I tried my PX200's, 32ohm) the hiss is very noticeable at gain of 6, almost to the point of annoyance. I will probably build my next PINT with a lower gain, since my dt770-80's are the highest impendance cans I have, and am interested in what other peoples observations are regarding the noise floor, as my problem could very well stem from some fault with my assembly.

I was quite surprised how well the PINT held up next to the Hornet. Aside from the hiss issue, I found it much harder to identify the differences between the two amps. With the PINT vs C-moy, the amps had different sound signatures, but the PINT and Hornet sound quite similar. I give the Hornet a slight edge in the bass department, and it generally sounded a smidge cleaner. For costing me ~1/6 the price, the PINT makes an admirable showing next to the Hornet.

I haven't had time to sufficiently test battery life yet, but I'll try to keep track and get back with that.

So, there you have it. I hope you found my observatons on the PINT somewhat informative.
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Mar 29, 2006 at 2:08 AM Post #3 of 103

jbloudg20

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I have mine built as well, but I can't case it until I go home this weekend. I used NJM4556 opamps (for battery life) but I will probably build another using some 8397's.

Good work, though!
 
Mar 29, 2006 at 2:15 AM Post #4 of 103

Teerawit

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Quote:

Originally Posted by firefox360
Interesting review! Could the PINT be the poor man's Hornet?!?!
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I'll let you know when my PINT is finished
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Mar 29, 2006 at 2:31 AM Post #6 of 103

kramer5150

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Quote:

Originally Posted by spike33
Nice review! How bout a comparison between PINT and pimeta?



Pint -VS- Mint... anyone??

Garrett
 
Mar 29, 2006 at 3:43 AM Post #7 of 103

amb

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Quote:

Originally Posted by darkisz
The one place where the C-moy won was the noise floor. I was surprised how much hiss came from the PINT when I didn't have music playing. With lower impendance cans (I tried my PX200's, 32ohm) the hiss is very noticeable at gain of 6, almost to the point of annoyance.


The AD8397 is actually a very low noise opamp. All the noise you hear are entirely due to the high resistor values used in the feedback loop. If you build the PINT without input coupling caps and use resistor values as in the Mini³ amp, you'll find that the noise floor to be a non-issue.
 
Mar 29, 2006 at 5:19 AM Post #9 of 103

darkisz

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Quote:

Originally Posted by amb
If you build the PINT without input coupling caps and use resistor values as in the Mini³ amp, you'll find that the noise floor to be a non-issue.


I do have another PINT board, and this does sound very tempting, but I don't trust myself to figure out the correct values. I think what you're saying is to jumper the C1 position, and use lower values for R2, R3, and R4? It looks like the Mini³ has 1.2k and 6k for R3 and R4 for a gain of 6. I'd like to set gain to 4 to get a bit more travel from the pot, so I was thinking maybe 1k/3k? How does R2 fit into it? Tangent says in the parts selection that R2 should be 10x the pot value (which is 10k, making R2 100k, like in the PINT schematic), but in the Mini³, R2 is 1k? Does it have to do with Mini³'s R1, which the PINT doesn't have?
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I should probably spend more time reading Art of Electronics and less time building stuff I don't understand.
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Mar 29, 2006 at 6:41 AM Post #10 of 103

shimage

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Quote:

Originally Posted by darkisz
but in the Mini³, R2 is 1k? Does it have to do with Mini³'s R1, which the PINT doesn't have?
confused.gif


I should probably spend more time reading Art of Electronics and less time building stuff I don't understand.
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amb also has 100k for "R2" (it's his R1). I thought that Tangent's website was pretty good and explaining things, but if you need more, read the section on non-idealities in H&H; I forget what he calls it ... I think it's chapter 7?
 
Mar 29, 2006 at 6:46 AM Post #11 of 103

amb

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Quote:

Originally Posted by darkisz
I do have another PINT board, and this does sound very tempting, but I don't trust myself to figure out the correct values. I think what you're saying is to jumper the C1 position, and use lower values for R2, R3, and R4? It looks like the Mini³ has 1.2k and 6k for R3 and R4 for a gain of 6.


Install 1KΩ resistors in place of C1 on the PINT (this would correspond to R2 in the Mini³. PINT's R2 is actually Mini³'s R1 (100KΩ).

Quote:

I'd like to set gain to 4 to get a bit more travel from the pot, so I was thinking maybe 1k/3k?


You want to make the value of R1 || R2 to be close to R3 || R4. Since we have R1 || R2 ~= 1KΩ, R3 || R4 should also be about 1KΩ. The 6KΩ || 1.2KΩ accomplishes that for a gain of 6, but to get a gain of 4 you should use R4 = 4.7KΩ and R3 = 1.5KΩ. This will give you the lowest possible DC offset.

Quote:

How does R2 fit into it? Tangent says in the parts selection that R2 should be 10x the pot value (which is 10k, making R2 100k, like in the PINT schematic), but in the Mini³, R2 is 1k? Does it have to do with Mini³'s R1, which the PINT doesn't have?
confused.gif


PINT does not have the equivalent of Mini³'s R2, but you "fix" that by putting a resistor in place of C1. PINT's R2 is Mini³'s R1. Btw, the Mini³ R1 and R2 designations follow the precedence set with the M³ amp, but is reversed from that of the Cmoy, Pimeta and PPA. At least all our R3 and R4 are consistent...
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Mar 29, 2006 at 12:41 PM Post #12 of 103

darkisz

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Thanks for the info! I'll give this a go on my next one.
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Mar 29, 2006 at 8:17 PM Post #13 of 103

morsel

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Quote:

I was surprised how much hiss came from the PINT when I didn't have music playing. With lower impendance cans (I tried my PX200's, 32ohm) the hiss is very noticeable at gain of 6, almost to the point of annoyance.


Tangent has suggested the presence of input capacitors on the PINT are optional, but the PINT documentation uses them and the commensurate high impedance gain resistors as the default configuration, resulting in unacceptably high noise levels, especially for low impedance headphones.

Many people will build or have already built their PINT using this default configuration, which is really unfortunate, as the amp has the potential to be much quieter. I recommend all PINTs use 1K resistors instead of C1 and 1.2 & 6K gain resistors instead of 120 & 600K.

Note that a leaded (not SMD) 1/8W 1K resistor replaces C1.
 
Mar 29, 2006 at 9:16 PM Post #14 of 103

jbloudg20

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Quote:

Originally Posted by morsel
Tangent has suggested the presence of input capacitors on the PINT are optional, but the PINT documentation uses them and the commensurate high impedance gain resistors as the default configuration, resulting in unacceptably high noise levels, especially for low impedance headphones.

Many people will build or have already built their PINT using this default configuration, which is really unfortunate, as the amp has the potential to be much quieter. I recommend all PINTs use 1K resistors instead of C1 and 1.2 & 6K gain resistors instead of 120 & 600K.

Note that a leaded (not SMD) 1/8W 1K resistor replaces C1.



Looks like I'll take your advice on my next build.
 

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