AKM 4393 vs. AKM 4396 why bother? - Page 4 - diyAudio
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Old 21st October 2010, 08:27 PM   #31
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Default Removing the AC coupling caps

Hi Guys
Can you help a NOOB out?
I'd like to try these 96's on my digital recorder outs but I haven't a clue which cap/s are the AC coupling caps the literature says you can eliminate?

I've attached a schematic (blowup) around the chip for CH 1 & 2.
I would assume I could bypass C142/C141 and C144/C143?
I am curious what C146/C147 are there for?

If I remove C142/141 and C144/143, then the outs will go into ADA4627-1's (schematic also attached) - really like the sound of this op amp.

I was intending to leave the analog out circuit section alone and just upgrade the C414 to a Panasonic FM 100uf/25V (only cap that will fit 6.3mm dia space).

Do you see any issues doing that?

Thanks and Best
F5
Attached Files
File Type: pdf D-A .pdf (77.6 KB, 105 views)
File Type: pdf Analog OUT.pdf (62.6 KB, 121 views)
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Old 22nd October 2010, 12:47 AM   #32
Jaimo is offline Jaimo  Canada
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Default Capacitor-less output circuit

Here's a link to a circuit I built for my DEQ after changing to a AK4396...

AK4396: best solution for output stage

Check out post #98
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Old 22nd October 2010, 01:26 AM   #33
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Wow!
Thanks Jaimo
I am just excited to see the same number of components!
Hello SMD world....here I come ...gulp!!!
How did you come up with those cap and resistor values? Is that Op Amp specific or do you think your values would work better than what's already on my circuit board (For ADA 4627-1)?
So if I read your circuit correctly, I can eliminate C414 and R417 after the Op Amp?
All the Best
F5

Last edited by fleximan5; 22nd October 2010 at 01:36 AM.
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Old 22nd October 2010, 04:28 AM   #34
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Funny enough, a buddy of mine is working on taking this -10db output to +4db via transformers (no clue when I'll see that though).
At this point I will take this -10 into a +4 daughter board that is sold as an extra for the recorder.
Sorry for the probably inane questions but I really don't know anything yet (head is still spinning from all the capacitor study I did! LOL)
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Old 22nd October 2010, 11:01 PM   #35
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Hey Jaimo
So I talked to my buddy and he recommends getting a bread board, O scope , variable resistors and such so I can check output with various input voltages of the original circuit. Then I need to tweak things with the new op amp/circuit to match that.
Do you agree?
Just curious, how did you pick the OPA2604 and did you do as described above?
Even if you go from FET to FET, BJT to BJT style op amps, do you still need to test as described?
I am dying to try and just drop a dual ada4627-1 into your circuit and be done but what do you say?

Thanks and Best
F5
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Old 24th October 2010, 10:18 PM   #36
Jaimo is offline Jaimo  Canada
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Join Date: Oct 2005
Default Good regulated PSU's make good sounding op-amps!

Quote:
Originally Posted by fleximan5 View Post
Hey Jaimo
So I talked to my buddy and he recommends getting a bread board, O scope , variable resistors and such so I can check output with various input voltages of the original circuit. Then I need to tweak things with the new op amp/circuit to match that.
Do you agree?
Just curious, how did you pick the OPA2604 and did you do as described above?
Even if you go from FET to FET, BJT to BJT style op amps, do you still need to test as described?
I am dying to try and just drop a dual ada4627-1 into your circuit and be done but what do you say?

Thanks and Best
F5
Regarding Bread Board - I'm not a fan. IMO BB is okay for simple digital circuits but I have had several bad experiences with poor connections, stray capacitance etc. Instead, I use a proto-typing board and hard solder my connections and pay careful attention to wire routing and PSU arrangement, etc. A good electronics store will have a wide range of prototyping boards that allow you to build up and tweak a circuit that you can use as your final product. (saving you the need to get a printed circuit board made up)

I used an OPA2604 in a Kenwood KT7500 that I tweaked and loved it's sound quality. For my DEQ, I built up a cct on a prototyping board using the AK data-sheet design and tweaked the resistors until my output level was satisfactorily low. This was initially intended as a temporary fix until I found some good transformers but the sound quality was good enough for me to make this a permanent tweak.

Since the op-amp in your circuit comes highly rated, you would probably do better by building a better regulated psu before "rolling" op-amps. Take a look at the many threads on low impedance regulators in the diyaudio forums.
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Old 25th October 2010, 03:02 PM   #37
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Ah. Thanks Jaimo
Then you concur with my buddy on the PSU thing! Although, he didn't put it quite the way you did.
Nice to know my insatiable desire for the best drove me out of control again! LOL

I've been practicing with SMD and feel quite comfortable. I might just have to try your 2604 circuit out on a channel though. If I do, I'll post what I qualitatively hear.

Not sure what to do with all these 4627-1s now...:-P
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