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the Pimeta-V2 thread - Page 9

post #121 of 551
12/9/09 at 11:01pm
I think you should get something like this:



To be honest I've got the check if it actually outputs a signal. It powers up, but it has been in the basement for a *long* time.

Pre-post edit - I just Googled this thing - it apparently runs on tubes.
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post #122 of 551
1/10/10 at 9:27pm
I'm not getting the correct values when testing the power supply in step 11 of the step by step assembly guide. It appears the voltage isn't being split. Here are the voltages I'm getting with a slightly used 9v battery:
OPALR V- -8.77 V+ -.56
OPAG V- -8.77 V+ -.56
TLE2426 COM -8.77 OUT -4.66 IN -.56
I also measured the + and - pins of the power caps and got -8.77 on the negative pins and -.56 on the positive pins. Any ideas on what would cause this? I have no idea where to go from here other than maybe replacing the tle2426.
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post #123 of 551
1/10/10 at 10:29pm
Thread Starter 
anyone want any signal generator chips?

I found some old (very old) 8038 chips. anyone remember those? those used to be good (sort of) way back when.

new chips are MAX038 (from what I've read). but I have some IC8038's in DIP form in case anyone wants any
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post #124 of 551
1/11/10 at 2:26am
I just remeasured the voltages and on OPALR and OPAG and got
4.09 for V+ and -4.09 for V-. I used a different spot the board to
measure the input ground IG. This time I used the area in the
scratchpad marked IG. Previously I was measuring from where the
input ground IG is right by IL and IR. I also measured this time by
using the top of the board so I could just stick one probe in a DIP
socket and the other probe in the hole marked IG in the scratchpad
area. When I use the bottom of the board I have a harder time
with the measurements because the probes want to move around
the soldered connections causing the voltage measurements to jump
around. I think my original issue with the voltages was just with me
not being able to hold the probes still enough.
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post #125 of 551
1/13/10 at 1:42am
Alright, I think I'm going to build one of these babies.

If I am, I would build it in the standard Serpac case with the 9V battery cover. Could someone give me tips on picking parts to strike a nice balance between SQ and battery life? I imagine that I would use this amp maybe 50% home, 50% on the go. Good battery life would be a plus.

Thanks.

edit: actually, good battery life isn't THAT important because I would use rechargeable batteries. Maybe if it could last 15-20 hours, I would be happy.
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post #126 of 551
1/13/10 at 5:08am
Quote:
Maybe if it could last 15-20 hours
You are going to have to leave the buffers out to get anywhere close to that .. otherwise you are looking at closer to 4 hours with a single 9 volt NiMH battery.
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post #127 of 551
1/13/10 at 8:49am
With a 500 mAh LiIon "9V" rechargeable, you might get close to 10 hours. That runs the cost up due to the special battery and equally special charger, though.

As for parts advice, I've said pretty much all I have to say in the docs. Hint.
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post #128 of 551
1/15/10 at 5:11pm
Just finished my pimeta. I only have a couple of hours of listening time
on it but i'm loving it. I've only heard this amp and a cmoy I built and
i'm really impressed with how good music sounds at low volumes with
this amp. I can't believe there is so much impact at low volume levels.

I didn't class A bias so I'll have add that later. I'm really curious to see
if there any sonic differences with the class A biasing. Just ordered a
tread today to hookup to the pimeta. It will fun to see how it sounds
with a tread vs 9v battery.

Thanks for a great amp Tangent. I wish I didn't have to work tonight so I could stay home and play with my new toy.
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post #129 of 551
1/15/10 at 6:39pm
Quote:
Originally Posted by Skoalman View Post
i'm really impressed with how good music sounds at low volumes with this amp. I can't believe there is so much impact at low volume levels.
Yeah, the LMH6321 is a studly little thing. Much better than the BUF634.

Quote:
Thanks for a great amp Tangent.
You're welcome! Thanks for the review.

Quote:
I wish I didn't have to work tonight so I could stay home and play with my new toy.
Listen at work?
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post #130 of 551
2/9/10 at 12:44am



Just finished the main stuff on the amp. Parts selection and assembly was straightforward with tangentsoft's guides, and soldering took just a few hours. When it came time to test out the amp with headphones, I was greeted with glorious music, no troubleshooting required. It surprised me considering how much of a klutz I am with this kind of stuff.

Right now I'm just powering it with a 9V battery, but I do have a tread I need to finish.

I think I will stick it in a case after a round of tests coming up.
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post #131 of 551
2/9/10 at 12:47am
Oh I forgot, I used an OPA2132 and an OPA132 for the ground channel. Gain of 3. I think I may bump it up to 5 to ensure that I can achieve earsplitting levels with any headphone.
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post #132 of 551
2/9/10 at 7:11am
Nice!

On the gain, what cans were you testing with, and where was the knob in clock terms?
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post #133 of 551
2/9/10 at 4:33pm
Monster beats Solo - These headphones are very sensitive, so I keep it around 11 o'clock for massive sound.

Klipsch S4 - Even more sensitive, 9-10 o'clock.

Grado SR-80 - Much less sensitive than either of the above, so I crank it to around 12.

Sennheiser HD580 - Also around 12.

The amp is more than loud enough right now, but I could see myself using quieter sources in the future (and I've been listening to mostly hip hop lately. Classical/jazz music is quieter and I could use some more knob travel to be comfortable).
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post #134 of 551
2/9/10 at 7:33pm
Okay, just realize that the higher the gain, the higher the noise floor. Raise it too much and you can get audible levels of hiss, especially with the more sensitive headphones.
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post #135 of 551
2/9/10 at 10:48pm
Quote:
Originally Posted by tangent View Post
Okay, just realize that the higher the gain, the higher the noise floor. Raise it too much and you can get audible levels of hiss, especially with the more sensitive headphones.
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