Op Amp Rolling

[olieb]

Fosi asked me to send a video of the problem, so I recorded this. Here it is, in case anyone here can shed some light on this issue.

That might be EXACTLY what Amir was talking about in respect to "messing with the design" and others mentioning problems of stability that can lead to oscillations.
But you know that already. And what is the risk? Maybe the amp and opamp, maybe a speaker. That's not nice, but it is not going to burn your house down, will it?

So lets look on the bright side.
With the stock opamps all this nice whistling would probably be lost for good. Who knows, with a bit of drift in some part of the circuit you might even hear a full symphony. Isn't that what everybody wants: an amp that acts like a musical instrument? Great improvement in sound, no doubt!

 

[Joe Smith]

Sure sounds like oscillation to me...I would not use those particular op-amps, if I cared about my speakers...!

I have used 4562 op-amps in place of the stock 5532 amps, also Burson V5i op-amps...no clear improvement, no veils lifted, but they seem stable and cause no problems with my Aiyima amps...

 

[olds1959special]

That is a horribly unstable amplifier. Stop using it now if you value your speakers. Your problem is you have no idea what energy it is putting out at ultrasonic frequencies** - that you can't hear, but can possibly toast your tweeters.

EDIT - or just put the stock Opamps back in.

**And that might be continuous, based on the rising pitch in your video.

I got a reply from Fosi. They said the amp is an older model, and isn't fully compatible with MUSE02. So I will stop using it.

I don't have the original op-amps.

"The previous BT20A PRO is not fully compatible with MUSE02, and there will be this kind of current noise. Do you have the ability to add a 22PF capacitor at coordinates C14/C54?"

 

[olds1959special]

I want to replace the op amps to fix this amp. I asked what I could try. The response from Fosi was:

"Yes, you can try LME49720 ,OPA2134PA , SPARKOS LABS SS3602 Discrete dual channel Op Amp, Ss2590, RM4559,OP249, AD827 etc."

Which of these should I try first? Where is best place to get them?

 

[Joe Smith]

I want to replace the op amps to fix this amp. I asked what I could try. The response from Fosi was:

"Yes, you can try LME49720 ,OPA2134PA , SPARKOS LABS SS3602 Discrete dual channel Op Amp, Ss2590, RM4559,OP249, AD827 etc."

Which of these should I try first? Where is best place to get them?

Frankly, I would stick with what was originally in there, as it's generally only golden-ear people who seem to hear differences. What was the original spec - 5532s?

In the US, I know you can get 5532s and 4562s from Mouser or Digi-Key and be sure they are genuine. Not expensive. Probably they have 2134s as well.

Sparkos, you can order direct from them. Expensive, far more than the cost of the amp. Some people swear by them. It's a road I chose not to go down.

 

[DonR]

That might be EXACTLY what Amir was talking about in respect to "messing with the design" and others mentioning problems of stability that can lead to oscillations.
But you know that already. And what is the risk? Maybe the amp and opamp, maybe a speaker. That's not nice, but it is not going to burn your house down, will it?

So lets look on the bright side.
With the stock opamps all this nice whistling would probably be lost for good. Who knows, with a bit of drift in some part of the circuit you might even hear a full symphony. Isn't that what everybody wants: an amp that acts like a musical instrument? Great improvement in sound, no doubt!

"It's very musical."
"Really? Which instrument does it play?"
"What?"

 

[LTig]

I got a reply from Fosi. They said the amp is an older model, and isn't fully compatible with MUSE02. So I will stop using it.

I don't have the original op-amps.

"The previous BT20A PRO is not fully compatible with MUSE02, and there will be this kind of current noise. Do you have the ability to add a 22PF capacitor at coordinates C14/C54?"

Ha, I knew it.

I want to replace the op amps to fix this amp. I asked what I could try. The response from Fosi was:

"Yes, you can try LME49720 ,OPA2134PA , SPARKOS LABS SS3602 Discrete dual channel Op Amp, Ss2590, RM4559,OP249, AD827 etc."

Which of these should I try first? Where is best place to get them?

If the original is the NE5532, then these. The LME49720 is the best replacement regarding SINAD. It's 6 times faster and I would not use it without measurements, but since Fosi recommends it it should not be unstable. Both are so cheap that shipping is more expensive then the price of the chips.

 

[SIY]

since Fosi recommends it it should not be unstable.

Famous last words. They're selling a gimmick to deal with a parity (and commodity these days) product.

I want to replace the op amps to fix this amp. I asked what I could try. The response from Fosi was:

"Yes, you can try LME49720 ,OPA2134PA , SPARKOS LABS SS3602 Discrete dual channel Op Amp, Ss2590, RM4559,OP249, AD827 etc."

Which of these should I try first? Where is best place to get them?

Stick with the original, none of the others will give any actual improvement. Digikey, Mouser, Newark are all reliable go-to suppliers.

 

[olds1959special]

I found a local electronics parts store (not many of those left) that sold the NE5532P op-amps, so I got two and put them in. No more weird sounds at startup, and the sound is OK.

Edit: also ordered OPA2134PA to try.

 

[olds1959special]

I really don't like the sound of the NE5532P op-amps in my Fosi BT20A PRO. I can't wait to try the OPA2134PA's instead. Are there any others worth trying in the list (LME49720 ,OPA2134PA , SPARKOS LABS SS3602 Discrete dual channel Op Amp, Ss2590, RM4559,OP249, AD827)?

 

[beefkabob]

I really don't like the sound of the NE5532P op-amps in my Fosi BT20A PRO. I can't wait to try the OPA2134PA's instead. Are there any others worth trying in the list (LME49720 ,OPA2134PA , SPARKOS LABS SS3602 Discrete dual channel Op Amp, Ss2590, RM4559,OP249, AD827)?

You may as well replace your power cable too while you're at it. The last 6 feet are the most important, I was told.

 

[Great Sun Jester]

 

[SIY]

I really don't like the sound of the NE5532P op-amps in my Fosi BT20A PRO. I can't wait to try the OPA2134PA's instead. Are there any others worth trying in the list (LME49720 ,OPA2134PA , SPARKOS LABS SS3602 Discrete dual channel Op Amp, Ss2590, RM4559,OP249, AD827)?

Since the sound of the DAC with any properly functioning replacement opamp will be the same, you may want to either sell the DAC or use non-digital sources.

 

[olds1959special]

You may as well replace your power cable too while you're at it. The last 6 feet are the most important, I was told.

I can hear a difference and am asking a serious question, about sound and compatibility. I guess you can’t hear the difference between op-amps?

 

[beefkabob]

I can hear a difference and am asking a serious question, about sound and compatibility. I guess you can’t hear the difference between op-amps?

It's called a placebo.

 

[olds1959special]

Since the sound of the DAC with any properly functioning replacement opamp will be the same, you may want to either sell the DAC or use non-digital sources.

You’re wrong. You can’t hear the difference between op-amps?

 

[olds1959special]

It's called a placebo.

I know what I’m hearing. You’re wrong. I know I’m right, because I can clearly hear the difference. Not everything affects the sound, power cables don’t, and USB isolators have not made a difference. But op-amps do.

 

[SIY]

You’re wrong.

If an opamp oscillates or is noisy in a circuit, you can hear that. But this isn't the case here.

 

[olds1959special]

If an opamp oscillates or is noisy in a circuit, you can hear that. But this isn't the case here.

Yea, but the sound of the op amp when playing music is worse to my ears.

 

[beefkabob]

I know what I’m hearing. You’re wrong.

Show me measurements that there's an actual, perceivable difference in sound, or show me the statistically real blind testing results. It's all a placebo. Psycho-acoustics are real. Actual sound differences in opamp rolling? Nah, only if something is broken or incompatible. Fosi has been known to make broken equipment, though.