[nomad0677]

Quote:

Originally Posted by bichi /img/forum/go_quote.gif #1. 33087: MC33078 - originally made by Motorola, division sold to ON Semiconductor - Creative usually uses this opamp for MIC-IN - datasheet: http://www.onsemi.com/pub_link/Collateral/MC33078-D.PDF #2. 75179B: SN75179BP - Texas Instruments, Differential Driver/ Receiver Pair, balanced transmissions - datasheet: http://www.ti.com/lit/gpn/sn75179b #3. 4556A: NJM4556A - New Japan Radio, high-gain, high-output opamp, usually used for headphone drive capability - datasheet: http://semicon.njr.co.jp/njr/hp/file...o?_mediaId=147

Thanks bichi. I assume that #3 is my headphone opamp and LM4562 would be a good replacement for that?

And which one of the remaining mystery IC's is for RCA?

I will be back with IC numbers in a moment.

Edit: IC numbers on both IC's are the same

33078
Z512

 

[Random Murderer]

Quote:

Originally Posted by ReTiCuLe /img/forum/go_quote.gif Thanks Random & Bichi. Now that all my questions are answered I'm going to give the old card a whirl later on, after work. Btw, how fragile are the oAMPs to static electricity? I've never wore a wrist band soldering psx's, xbox's back in the day and actually had something fail on me.

just touch your computer chassis or a cold water pipe before handling them.

 

[bichi]

Quote:

Originally Posted by nomad0677 /img/forum/go_quote.gif "...Thanks bichi. I assume that #3 is my headphone opamp and LM4562 would be a good replacement for that?..."

Can't speak from personal experience, I don't have your bay-device and don't regularly listen with X-FI, direct to headphones.

- some headphone users have replaced 4556A's with LM4562/49720 and had no problems, while others complain about low-levels.
- depends on headphone impedance and SPL sensitivity. (note: 4556A's output drive current is spec'ed at about 70ma and LM4562/49720 is 26ma)
- eboy2003 is a headphone user, using an external tube amp and has experimented with different opamps. He might have a reliable opinion on LM4562/49720 direct to headphones.

National Semi LM4562 Datasheet:
http://www.national.com/ds.cgi/LM/LM4562.pdf

 

[Random Murderer]

Quote:

Originally Posted by bichi /img/forum/go_quote.gif Can't speak from personal experience, I don't have your bay-device and don't regularly listen with X-FI, direct to headphones. - some headphone users have replaced 4556A's with LM4562/49720 and had no problems, while others complain about low-levels. - depends on headphone impedance and SPL sensitivity. (note: 4556A's output drive current is spec'ed at about 70ma and LM4562/49720 is 26ma) - eboy2003 is a headphone user, using an external tube amp and has experimented with different opamps. He might have a reliable opinion on LM4562/49720 direct to headphones. National Semi LM4562 Datasheet: http://www.national.com/ds.cgi/LM/LM4562.pdf

if you're using high-end headphones you should use an amp anyway.
i'm only using sr80's and i still don't plug them directly into my sound card.

 

[ReTiCuLe]

I'm interested to know which oAMP is best for Headphone's as well.

Currently using Audio Technica ATH-A700's most comfortable can's I've ever owned while sounding great 8).

 

[ReTiCuLe]

Sigh. Only sound in the Left ear once again.

Could it be Vista to cause only sound in the left ear? I read somewhere this mod isn't vista friendly a while ago.

 

[nomad0677]

Quote:

Originally Posted by ReTiCuLe /img/forum/go_quote.gif Sigh. Only sound in the Left ear once again. Could it be Vista to cause only sound in the left ear? I read somewhere this mod isn't vista friendly a while ago.

I have had no Vista issues with the mod on 4 cards now.

 

[Random Murderer]

Quote:

Originally Posted by ReTiCuLe /img/forum/go_quote.gif Sigh. Only sound in the Left ear once again. Could it be Vista to cause only sound in the left ear? I read somewhere this mod isn't vista friendly a while ago.

my guess is that there's a severed trace around the opamp. that happened to me...

 

[bichi]

Quote:

Originally Posted by ReTiCuLe /img/forum/go_quote.gif "...I'm interested to know which oAMP is best for Headphone's as well..."

And for others pondering the same question...
- there are no "one answer fits all" and also subjective, ie., personal taste
- technicals need to be considered (headphone impedance, SPL (sound pressure level @ voltage), opamp drive capability, etc.)
- common trade off is better sonic performance vs. headphone "loudness/level" (solved with external headphone amp)

Basic opamp stuff with part numbers, opinions and test results:

Notes on Audio Op-Amps - (headphone centric)
Notes on Audio Op-Amps

D.Self: Designing with Opamps
Opamp Design

D. Self: Heavy Loads (headphones)
Opamp Design

 

[eboy2003]

I'm building a dual AD1955 external DAC w/ I2S support. Unfortunately AD1955 only supports 256fs, 512fs, 768fs, and need to change the settings via MCU. I plan to mod my SB0550 to direct output I2S signal via RS422 interface. Does anyone know SB0550 in bit-perfect mode use 256fs or 384fs for 16bit 44.1K CD audio?

My current half-done 1955pro dac, it supports balance out, but i will only set up for unbalanced rca output. Use 4 opa627 for I/V, 2 LME49710 TO-99 for LPF.

 

[eboy2003]

Quote:

Originally Posted by bichi /img/forum/go_quote.gif - eboy2003 is a headphone user, using an external tube amp and has experimented with different opamps. He might have a reliable opinion on LM4562/49720 direct to headphones.

LM4562/49720/49870 can drive headphone reasonably well unless you are using high impedance ones like hd-650. To my ear, when using hd-597 on SB0550 with LME49720 TO-99, the sound is a little bit too analytical, and the highs are harsh in some records. Driving through tube amp give much warm, musical sound, but I loose a little bit dynamics.

 

[ReTiCuLe]

I haven't found any broken traces. What looks wrong? Nothing is crossing over or touching with the meter.
This is the old card btw. the Xtreme Music.

Bichi perhaps if I solder where the oAMP legs are right now on the board and put them to the corisponding caps instead that would help? Also do I need to short out the capacitors? The problem is the sound in the Right Channel is very dim, you pretty much can't hear it.

I decided to re-solder all the oAMP connections well, that didn't help either lol.


If I can't get this working, anyone have confidence in repairing it? I would of course pay you for your services.

 

[bichi]

Quote:

Originally Posted by ReTiCuLe /img/forum/go_quote.gif "...Bichi perhaps if I solder where the oAMP legs are right now on the board and put them to the corisponding caps instead that would help? Also do I need to short out the capacitors? The problem is the sound in the Right Channel is very dim, you pretty much can't hear it..."

- has to be a connection issue of some sort
- bad solder joint
- solder bridged under chip
- pad/trace short under chip
- SMT component moved (open or shorted) where you soldered wires
- cannot tell from your picture (not near enough detail)

 

[bichi]

Hardcore SB0550 Modders/AudioPhools Connecting External, Hi-Power, wide-band, Analog Amplifiers

- depends on PC power-supply, motherboard PWM/filtering, ground quality, etc.
- predominant 250khz, 125~350khz noise spectra present, +12, +5, +3.3 rails to chassis ground (~91avg mVrms)
- results in 250khz, ~12avg mVrms, switching noise, SB0550, Line-Out

Measurement:
- Fluke 97, battery, therefore, no ground-noise issues
- SB0550, Line-Out, LME49720, 1khz sine @ 250mVrms, 47kohm load
- ~25mVpp noise @ 250khz

External Amplifier: LM3886 GainClone
- fast calc: gain: 25, therefore, 25mVpp noise x 25 = 625mV, ~0.07w @ 6ohmavg
- actual: 800mVpp, 152mVrms

Quick Solution:
- 250khz classic, passive Twin-T notch filter (predesign work for possible active LTC1059 notch)
- fc = 1 / (2 pi R C)
- problem: -3db fc point must not affect 20khz
- goal: Q of 6~10, to effectively kill 250khz noise
- must use NPO/COG capacitors, 1% resistors, low-noise, for stability and Q quality

Subjective:
- subject to debate, since some will argue 250khz is above audio range and is of no consequence
- secondly, others will argue reducing bandwidth above 20khz reduces "sound quality"
- appears to have measurable harmonic effects in audio band
- sounds good, LM3886 gainclone feeding B&O BeoVox MC120.2 speakers, Sennheiser HD-414SL and HD-414 Classics (headphones not primary playback)


REFS:
Scope, 250khz Noise, SB0550 Line-Out:
026-LM3886-SB0550-1kz-250khz-Noise-1200 - eSnips, share anything

Scope Results, LM3886 Amp Output, before and after, idle:
027-LM3886-5.11k-82p-before-after-1200 - eSnips, share anything

Scope Results, LM3886 Amp Output, 7khz @ 500mVrms, Filter IN/OUT, zoomed
032-LM3886-SB0550-250khz TwinT-before-after-800 - eSnips, share anything

RMAA v6.06 Summary Results, before and after, ~5Wattsrms out, at headphone voltage divider:
028-LM3886-250k notch-compare-RMAA-1200 - eSnips, share anything

Picture, notch filter, prototype PCB, SMT:
029-LM3886-250khz Notch Quick Proto-1200 - eSnips, share anything

Schematic, filter and LM3886 amplifier:
030-LM3886-250k Passive Notch-schem-001 - eSnips, share anything

LM3886 Amp, surplus case, pre-final/proto installation (sloppy):
031-LM3886-ProtoPreLayout-001 - eSnips, share anything


eboy2003:
- nice to see you crawling around, hands and knees at HSC Surplus LOL!
- what did you find on your outputs, SB0550 and tube amp, with your new scope?
- sound quality impact with SMT 1206 resistors?

 

[the.oldman]

ok trying my second x-fi mod did the opamp cap ers paper put back into comp and windows doesnt see it. the cap is a fk 1000uf 16v blackgate is this enough to power the card? i thought i'd try something diff and yes I reseated the card and tried diff slots my fatality red led is lit so the card is getting power any ideas?