[niksh]

Tangent, I ordered 2 sets of Pimeta2 PCBs and parts on Aug 15. According to the tracking no LK074729587US, it has been shipped out on Aug 16. However, until today, I have yet to receive the goods. Usually it only takes about 2 weeks for shipment from US to Malaysia. I have contacted the local post office but they are unable to check since it is under ordinary mail and treated as normal letter. I would appreciate if you could trace the transaction at you end. Thank you.

 

[tangent]

Sorry, but I can't trace it from this end, either.
 
To get international tracking, you would have had to use Express Mail, which is faster, but about twice as expensive as Priority Mail.
 
From the few reports I get back, two week deliveries are normal, but I have also seen it take longer, even a month.

 

[niksh]

Ok then, I wait another week or two. Then what? I have to place another order. Is it insured? Thank you.

 

[tangent]

Don't worry about the package being lost. That is a very rare thing in my experience. Delays in international mail, however, are not rare at all.

 

[niksh]

Thanks for the reply. I will wait for the board, better late than sorry.

Btw, back to C4 issue, I have read the doc, but it does not mentioned anywhere about the size ot tant caps. You only mentioned that easiest to use are 7343 surface-mount caps. It is better to use the same size i.e 6.8uF or can I go for 47uF tant or larger, does it make any different.

 

[tangent]

When you asked about the size, I assumed you meant the physical size, not the capacitance.
 
As to that, the capacitor dielectric doesn't change the advice: 1 to 10 uF is a good range for C4.

 

[niksh]

Thank you for your reply. FYI, I finally received the Pimeta V2 PCB and I am really impress with the quality.
It is the best that I that I have seen so far. Btw, I am still using Pimeta V1 and I really enjoy listening to it.
I hope the V2 will be an upgrage.

 

[firefish15]

LMH6321 product change notice.
 
I recently receive an email from Mouser that the manufacturer has published a product change notice for the LMH6321 . Can the new chip still be used in the Pimeta without any changes? Attached is the data sheet Mouser sent me.
 
 
 
 

 

[jpaul64]

Working on my version of the Pimeta...
 

 

[tangent]

Quote:

I recently receive an email from Mouser that the manufacturer has published a product change notice for the LMH6321 . Can the new chip still be used in the Pimeta without any changes? Attached is the data sheet Mouser sent me.
 
 

 
I had a copy of the original datasheet on hand. According to DiffPDF, that PDF is identical to the original, except for the two TI pages added to bookend the original NatSemi document.
 
Unless that change notice said anything other than a datasheet change, that may be enough to explain it.
 
I suppose it's possible there is a process change happening, as chips move from a NatSemi foundry to a TI one, but since the datasheet hasn't changed, it hasn't changed the chip's operating parameters.

 

[firefish15]

Thanks Tangent, paul64. Just want to be sure that the LMH6321 can still be used without any modifications.

 

[jpaul64]

... finished!
 
 
   
 

 

[jpaul64]

I will try to reduce the dimensions of the board. I will replace the relays with AQW612S to reduce the overall power (µC had brown mode). Perhaps smaller SMD components?
 

 

[niksh]

Hi Tangent. Thank you for the PCB and Alps Vol which were delivered last week unopened. It takes only 8 days compared to 42 days last time. I have completed my Pimeta V2 and I am so happy that it works the first time. I am using OPA 227/2227PA and I have to get use to the tremendous bass it produces compared to V1 using AD8610/20. I changed to OPA134/2134 but I dont like the sound, too laid-back. Most probably the OPA227/2227 are still new need time to settle down. Here are the photo for both V1 and V2.

Presently I adjust the bias to 1 mA and max it can go only up to 1.3 mA with OPA227/2227. Both the opamp and buffers are warm. Btw what is the optimum bias. I saw in some thread someone mentioned the optimum bias in the range of 3 mA to 5 mA. Thank you.

 

[tangent]

Quote:

It takes only 8 days compared to 42 days last time.

 
Yes, international mail delivery time is quite variable. Your previous delivery time is well outside the normal range, but it's not the first I've seen to take that kind of time, either.
 
 

Most probably the OPA227/2227 are still new need time to settle down.

 
Op-amps don't change in sound over time. Your mind may change over time, though, as your preferences develop.
 

I have to get use to the tremendous bass it produces compared to V1 using AD8610/20.

 
 
Yes, a lone LMH6321 is a better headphone driver than a lone SO-8 BUF634, as you've done.
 
It also looks like your PIMETA v2 has a bit more rail capacitance, which would help with the bass, if true.
 
 

what is the optimum bias. I saw in some thread someone mentioned the optimum bias in the range of 3 mA to 5 mA. Thank you.

 
It depends on the chip.
 
The only reason to go higher than you currently can is with uncommon chips like the AD843 where you're having to overcome an already-high bias point.
 
For many chips, even 1 mA is vastly more than needed to achieve a change in operating point.