New OpAmps don’t like Pink Floyd

Stew

I installed AD826 opamps in my Yamaha CD Player (CDC-745) and upgraded my SDA 2B’s a few months ago. All of my CD’s sound much better from bottom to top …. until I played Dark Side of the Moon with the volume turned up a bit, that is. There’s something on this CD that sounds like guitar strings vibrating, e.g. after the intro on “Time”. It's a lower midrange/upper bass sound. Hey guitar players; Can anybody help me with a better description than that? It never caused a problem before but it’s very pronounced with the new opamps and at approximately 9:00 on the volume dial, it sounded like the drivers were coming out of their frames and the roof was falling in. I had to make a dash for the amplifier since I don’t have one of those fancy remote control’s like Shack’s! Has anybody checked out the WAF for one of those?

Fortunately, everything sounds fine and I don’t think I damaged anything. I’ve never heard my 2B’s stressed before but it sounded like the drivers bottomed out. Could my amp have clipped at 9:00? It’s a Yamaha AX-550 integrated amp with 100 wpc and 170 wpc headroom into 4 ohms. If not, is it likely that the driver’s would bottom out at that power level? I know my electronics aren’t the greatest but they’re not that bad either. I’m going to play it, very carefully, through the Sony DVP-NS50PS DVD player hooked to my system and see what happens. Everything else sounds much better on the Yamaha/AD826 player but maybe less is better in this case. Does Pink Floyd wreak havoc with anybody else’s system?

BlueMDPicker

I always thought it was a synthesizer. Could be a guitar run through one. The notes rise and then breakup into a resonating distortion that decays.

Hmmm, odd that the opamps react so strangely.

madmax

That is very odd. Maybe there is a sub frequency thing going on that wasn't being re-produced previously? I guess we would have heard of that. Maybe some electronic mismatch somehow with the new op amp?
madmax

SCompRacer

No havoc here. I've been to 11 oclock with the tube amp with Time on my SRS 2's and don't need or want any more. Try Welcome to the Machine from the Wish You Were Here album next. I didn't think an op amp could make too much of a good thing.

heiney9

Personally, I've never thought DSOTM was all that great of a recording. Sure, for it's time it had some cool effects and sounds (the clocks especially), but overall it's pretty flat and lifeless especially on the bottom end (very muddy, no delineation). Also has some high energy 'siblance'. It lacks a certain "crispness". Certainly not the worst I've heard, but merely average, atleast from what I expect.

YMMV

H9

P.s. The above statement is not to be confused with todays crappy recordings. DSOTM doesn't suffer in that way.

EDIT:I'll add that I have the original Capitol release from the early 90's. Maybe later versions like the 25th Anniversary edn. are sonically better

SCompRacer

Try the DSOTM 2003 Hybrid SACD.

Normanality

SCompRacer wrote:

Try the DSOTM 2003 Hybrid SACD.

Agreed! I've heard this cd on Rich's setup and mine with the same tube amp pushing Carver AL III's and the sound could never be construed as "lifeless". Perhaps they did a better job remastering this time around.

Tour2ma

Agree the redbook is not the best, but the LP wasn't bad at all...

michael_w

Does the cdp have a variable output? Maybe you're clipping the actual cdp? I've never had any problems with dsotm (I have the new sacd one).

Stew

michael_w wrote:

Does the cdp have a variable output? Maybe you're clipping the actual cdp?

Hmmm.. That's a thought. It does have a variable output so I'll give that a try. Thanks for the suggestion.

Stew

Stew

madmax wrote:

Maybe some electronic mismatch somehow with the new op amp?

When I originally researched opamps, I found some info on the diyAudio forum. They suggest installing a small? bypass capacitor between the + and – power supply pins on some opamps to keep them from oscillating. The AD826 is supposed to be pretty stable, though, and a lot of people don’t use a bypass cap. There is one guy on that forum who insists you should always use a bypass cap. Time will tell but he could be right.

Stew

BlueMDPicker wrote:

I always thought it was a synthesizer. Could be a guitar run through one. The notes rise and then breakup into a resonating distortion that decays.

Thanks, Much better description than mine! If it turns out to be oscillations in the opamps, maybe the "resonating distortion" sets it off. I'm hoping michael_w's solution works.

steveinaz

Your CD output level should be set to max. There is sort of a "vibrational sound" to the chord you are talking about, I know exactly the passage you are describing. I think what you're hearing is normal--maybe the new opamps display a little higher resolution of detail?

sda2mike

ok....i'll do it...i'll be the one....what's an 'op amp'?

BlueMDPicker

Here you go.

Stew

steveinaz wrote:

Your CD output level should be set to max. There is sort of a "vibrational sound" to the chord you are talking about, I know exactly the passage you are describing. I think what you're hearing is normal--maybe the new opamps display a little higher resolution of detail?

The opamps I’m using are a lot more detailed (i.e. higher resolution) than the originals. I really like the way they sound on everything else. With the new opamps and roughly 9:00 on the volume knob, you can actually see the cones vibrating and it sounds like the speakers are on the verge of self destructing. I don’t want to recreate the Pink Floyd concert where they intentionally blew the cones out of large, pretend speakers.

Stew

sda2mike wrote:

ok....i'll do it...i'll be the one....what's an 'op amp'?

What BlueMDPicker said. Opamp rolling (trying different opamps) in the output section of CD players is a popular upgrade on the diyAudio forum.

Tour2ma

Is it possible that in this case it's a sonic feedback issue?

That's what an analog guy would look for reading this. Don't know about OpAmps, but it seems like I've read where some digital components also are subject to this as well.

EDIT: Or the CDP is producing this part of DSOTM for the first time and the feedback is getting to more sensitive, mechanical CDP parts, e.g., the transport.

Stew

Tour2ma wrote:

Is it possible that in this case it's a sonic feedback issue?

That's what an analog guy would look for reading this. Don't know about OpAmps, but it seems like I've read where some digital components also are subject to this as well.

EDIT: Or the CDP is producing this part of DSOTM for the first time and the feedback is getting to more sensitive, mechanical CDP parts, e.g., the transport.

It does sound kind of like feedback. Maybe the spikes I just installed on my speakers are contributing to feedback in the CDP? I'll try some foam rubber or similar under the CDP.

SKsolutions

I think that Michael_W might have had something. If you changed the opamp you might have to adjust the output settings. The same setting (volume) on the dial might translate differently to this high gain opamp. Your (line out) level shouldn't be that different with a new opamp though as they are voltage limited by the supply. You said that you didn't solder in a bypass Cap when you installed it, and this being a feedback design amp, you might be experiencing feedback or clipping when you are trying to reproduce this particular harmonic. Try the output volume, some isolators, and then maybe install the Caps. Just my guess, both better and worse than some. I know I'd want to find out because it could happen unexpectedly anytime you play a new disc.
GL
Sean

Stew

SKsolutions wrote:

you might be experiencing feedback or clipping when you are trying to reproduce this particular harmonic. I know I'd want to find out because it could happen unexpectedly anytime you play a new disc.
GL
Sean

Bingo! I used AD826 opamps based on advice from the diyAudio forum so I asked for their help on this problem too. Here's a summary of what they told me:

High speed opamps can be prone to oscillation. The AD826 is extremely fast (50 MHz) but usually trouble free. Even though oscillations are usually radio frequency, they can sometimes cause the dc biasing to go haywire and cycle at low frequencies. Old-timers used to call it "motorboating" because that's what it sounds like. I don't claim to fully understand their explanation, but "motorboating" describes the sound exactly. Scary!!

They told me that bypass caps wouldn't fix this problem and the only real solution is to find a lower speed opamp. I ordered some AD823's (16 MHz) and they should be here in time to try this weekend. The AD823's should sound similar to what I have but trade a little detail for more smoothness. This may be a good tradeoff as the AD826's sound great but are really detailed. I also ordered some OPA2134's (8 MHz) just to see what they sound like. The OPA2134's are little brothers to the OPA627's that many seem to love. OPA627's undoubtedly sound better (and cost a lot more) but the OPA2134's should be similar enough to get the idea. I'm going to try all four of each and then two of one, two of the other and see how it affects the sound. If I can get a similar sound to what I have with no "motorboating", I'll be a happy camper!

F1nut

Hmmmm...another reason not to buy cdp's with opamps.

heiney9

F1nut wrote:

Hmmmm...another reason not to buy cdp's with opamps.

Or anything for that matter....opamps in amplifiers aren't the best design idea either.

madmax

A very small cap (0.001uF) from the output pin to the + input pin will lower their speed a bit and remove the feedback. Assuming this really is your problem.
madmax

Stew

madmax wrote:

A very small cap (0.001uF) from the output pin to the + input pin will lower their speed a bit and remove the feedback. Assuming this really is your problem.
madmax

Is it output to + input or - input? I've seen both suggested. I assume that two caps would be required for a dual opamp.

I'm going to try some different opamps first. If that doesn't work or I can't get the sound I'm looking for, I may try caps. If so, I'll probably have more questions first.

Thanks for the reply.

heiney9

Posted for informational purposes:

I found this on another website, may or may not help

FWIW

H9

Many components use ICs called op amps as audio amplifiers. Earlier op amps have very poor sound quality, especially if misused. Some engineers with a strong background in ICs and op amps learned that they could improve sound if they replaced slow, noisy, low slew-rate, or otherwise bad op amps with better ones. Some less informed people tried doing the same thing and made the sound worse.

One pitfall with op amp swapping is that some op amps are more prone to unwanted oscillation than others. The faster the op amp, the more likely it will cause an unwanted oscillation, which will really damage the sound. For that reason, Joe may succeed in replacing 741 op amps with 5534 op amps in his gear, and you may fail. It is dependent on design, layout, etc.With the new video type op amps, the power supply requirements may be different.

As technology and design expertise improves, audio op amps get better and swapping is getting less and less useful. Newer op amps are displacing yesterday's best, and sound surprisingly similar to straight wire.

Still, there are different op amps for different purposes. Bipolar op amps are ideal for preamplifiers where noise is critical. The OP-27, OP-37, LT1028, and LT1115 are very well received for phono preamps, head amplifiers, and microphone preamplifiers. Bipolar op amps are also more practical for signals with low source impedance.

FET devices like the OPA604 and OPA2604 have higher slew rate, higher bandwidth, and lower input current. These op amps are better for line-level inputs and high source-resistance signals. Some amplifiers, like the OP-37 and LT1115 achieve higher bandwidth by using less internal compensation. These amplifiers are not unity gain stable, and should not be used in circuits with low closed loop gain or large feedback capacitors.

Some of the better op amps for audio as of today include (* means highly recommended):

Single


Dual

AD845*


AD842

AD847


AD827

AD797*


NE5535

NE5534


NE5532

OP-27


AD712

LT1115*


LM833

AD811


OPA2604*

AD841


OP249*

HA5112*


LT1057


LT1028


AD744


SSM2016




With op amp part numbers, there is a lot of room for confusion. Here is a guide to the numbers that is often accurate:

Op amp part numbers start with a manufacturer's prefix:

* Analog Devices uses AD
* Burr Brown uses OPA
* Linear Technology uses LT
* Motorola uses MC
* National uses LF and LM
* PMI uses OP
* Signetics uses NE and SE
* TI uses TL

This can be confused because if TI copies a Signetics op amp, they may assume the Signetics prefix, or they may use their own. Fortunately, if the part numbers are the same, circuitry is almost exactly the same, as is the performance.

The next thing in the part number is two, three, four or five digits. This is invariably the key to the part. If the numbers are the same, the parts are almost surely the same. For example, an LM357N and an LM357J are electrically identical and sound the same.

Next is a letter or two indicating the op amp package and possibly how it has been tested and what tests it passed. Unfortunately, manufacturers haven't standardized these letters. Fortunately, you almost never care. If it is a dual-inline (DIP) package and you are replacing a DIP, you shouldn't have to worry whether or not it is ceramic or molded. Likewise, you rarely care if it has 100uV offset or 4mV offset for audio. Finally, you don't care if it wasn't tested at elevated temperatures because you will use it in your house, inside well ventilated gear.

So in general, an NE5532J is a TL5532N, and an AD827JN will sound the same as an AD827LD. If you aren't sure about some detail, call or write the IC maker and ask for a data sheet on the parts in question. They will always send data sheets for free, and these data sheets contain details on the various part numbers, internal circuitry, and electrical characteristics.

Stew

I installed AD823 opamps and the problem is solved! The sound is very close to the AD826's I previously installed but a little smoother and no oscillation!! I'm looking forward to spending some more time listening to these but my initial impression is that they sound as good as, if not a little better than, the AD826 (and much, much better when the AD826's are "motorboating").

heiney9 wrote:

One pitfall with op amp swapping is that some op amps are more prone to unwanted oscillation than others. The faster the op amp, the more likely it will cause an unwanted oscillation, which will really damage the sound. For that reason, Joe may succeed in replacing 741 op amps with 5534 op amps in his gear, and you may fail. It is dependent on design, layout, etc.

Exactly! Even when they work correctly, the sound will be different in different players depending on the design (DAC, output stage, etc.). That's why opamp rolling (trying different ones) is popular.

Here's a few links on opamp reviews if anybody's interested:

http://tangentsoft.net/audio/opamps.html
http://www.rock-grotto.co.uk/opamp.htm

These are both for headphone amplifiers but still applicable.

There's also a lot of information at diyaudio.com and audioasylum.com if you search.

Stew

I did some critical listening last night. My CD player has four opamps in the analog output section. The first two convert the balanced signal from the DAC to an unbalanced signal which then goes to a low pass filter. The last two opamps are the output buffers. With four AD826's, my system had more punch and detail (but oscillated ocassionally). With four AD823's, mids and highs were a little smoother but I lost the punch and bass response. I tried two AD826's for balanced to unbalanced and two AD823's for output buffers. This combination gives me the punch, bass, detail, and smoothness - with no oscillation.

Now I'm actually glad the output buffers oscillated. I would have been content with the way four AD826's sounded but this combination sounds noticeably better.

george daniel

sda2mike wrote:

ok....i'll do it...i'll be the one....what's an 'op amp'?

Mike, thanks for stepping up and asking, I too, was wondering,,, wtf is an op-amp, now I know. Do all cdp's have these? Can anyone name a few that don't? I have an older Rotel cdp 865bx,and was thinking about upgrading in the future.

heiney9

george daniel wrote:

Mike, thanks for stepping up and asking, I too, was wondering,,, wtf is an op-amp, now I know. Do all cdp's have these? Can anyone name a few that don't? I have an older Rotel cdp 865bx,and was thinking about upgrading in the future.

It's my understanding that opamps which are essetially IC (integrated circuits) are used in the input and output sections of cdp's. Most older and newer high end players use actual discrete transistors usually in class A. Opamps IMO, are a bit of short cut and cost cutting tool. A well designed "front end" of a cdp or DAC, etc., does not use opamps. Many here may argue that opamps are just as good as discrete transistor circuit's I'm not one to agree. They are used in other circuits as well. Opamps are used to amplify signals, buffer signals, integrate signals, differentiate signals, sum multiple signals. In a very broad sense opamps are a very low cost way to replace a transistorized curcuit, it also saves space. They are used in headphone amplifiers, portables, etc.

See this link for a basic explanantion.....much better than I could hope to do.

http://web.telia.com/~u85920178/begin/opamp00.htm

As far as your Rotle having opamps, not sure.

H9

george daniel

H9--thanks,makes sense to me(now), I appreciate the reply