I have a dbx 2231 EQ that I use to tune a home HiFi system to a Harman curve at my listening position using REW. I bought this having seen the results of testing and a favorable review by ASR, and I’ve found that I presently prefer this to the DSP route that I used previously. Powered by a filtered conditioner and using balanced connections, this EQ is dead quiet in this system and I have noted no perceptible degradation in signal integrity, separation, or soundstage.
That being said, having observed audible improvements made by various discrete class A op amps (e.g. Sparkos, Burson, etc.) in the output stages of DACs, that makes me curious if op amp rolling may have an effect in this EQ. The architecture employs (4) NE 5532s on the input and output stages, and (32) NJM 4560s in the constant Q bandpass filters. One might speculate as to why these particular op amps were used, certainly cost was a factor, and I’m surprised the filters aren’t the 4560DD low noise versions although no noise is apparent, not audible noise anyway.
Having both newer Sparkos and Burson discrete op amps on hand, I felt this may make for an interesting exercise. I asked Andrew Sparks for his opinion, and he suggested trying the output and input parts first. Swapping the four NE5532s on the inputs and outputs involves just a bit of effort on my part to remove the four solder-through NE5532 ICs and replace with DIP8 sockets that I have on hand. On the other hand, swapping all those filter op amps for discretes would be prohibitively expensive even if the PS were up to it, and I'm not as optimistic that newer IC op amps would justify the hassle of swapping all those NJM 4560s, even for experimental purposes, although I found one person who did this about 10 years ago.
Any thoughts, intuition, hallucinations, etc., on this subject are appreciated.
That being said, having observed audible improvements made by various discrete class A op amps (e.g. Sparkos, Burson, etc.) in the output stages of DACs, that makes me curious if op amp rolling may have an effect in this EQ. The architecture employs (4) NE 5532s on the input and output stages, and (32) NJM 4560s in the constant Q bandpass filters. One might speculate as to why these particular op amps were used, certainly cost was a factor, and I’m surprised the filters aren’t the 4560DD low noise versions although no noise is apparent, not audible noise anyway.
Having both newer Sparkos and Burson discrete op amps on hand, I felt this may make for an interesting exercise. I asked Andrew Sparks for his opinion, and he suggested trying the output and input parts first. Swapping the four NE5532s on the inputs and outputs involves just a bit of effort on my part to remove the four solder-through NE5532 ICs and replace with DIP8 sockets that I have on hand. On the other hand, swapping all those filter op amps for discretes would be prohibitively expensive even if the PS were up to it, and I'm not as optimistic that newer IC op amps would justify the hassle of swapping all those NJM 4560s, even for experimental purposes, although I found one person who did this about 10 years ago.
Any thoughts, intuition, hallucinations, etc., on this subject are appreciated.
After spending substantial amounts of money on Burson type stuff, you will absolutely be convinced there will be audible improvements... In reality however, nothing will improve, as a carefully set up DBT will tell.
So, my honest answer is: no, those replacements are BS, unless the original circuitry used incorrect Opamps for the job at hand.
But I am afraid that is not the answer you are looking for.
So, my honest answer is: no, those replacements are BS, unless the original circuitry used incorrect Opamps for the job at hand.
But I am afraid that is not the answer you are looking for.
I owned and used Behringer DEQ2496 a lot for linearizing fullrange loudspeakers and subwoofers.
It is full of 4580 op amps. There is an option of pass through for this Digi EQ and on / off did not show any change in sound.
So even with loudspeakers of high resolution I could not hear any difference. A change of op amps would at best bring no difference but the risk of damaging a functioning gear if only one op amp de soldering and soldering on would not success.
With a headphone amp I did op amp rolling between NE5532, OP 4580, TL072 and LM4562 only the old 072 was detectable due to a bit more distortion. However this was not a blind test and the circuit was not optimized for any type of these op amps - the usual problem for op amp rolling is that sometimes the circuit is adapted to the used type of op amp if the manufacturer did its job well. Op amp rolling in such a situation is not doing justice to different type of op amps.
It is full of 4580 op amps. There is an option of pass through for this Digi EQ and on / off did not show any change in sound.
So even with loudspeakers of high resolution I could not hear any difference. A change of op amps would at best bring no difference but the risk of damaging a functioning gear if only one op amp de soldering and soldering on would not success.
With a headphone amp I did op amp rolling between NE5532, OP 4580, TL072 and LM4562 only the old 072 was detectable due to a bit more distortion. However this was not a blind test and the circuit was not optimized for any type of these op amps - the usual problem for op amp rolling is that sometimes the circuit is adapted to the used type of op amp if the manufacturer did its job well. Op amp rolling in such a situation is not doing justice to different type of op amps.
Today I consider the 4580 as a neutral piece of amplifying gear doing its job correctly if used to specification by the manufacturer after my headphone listening test. It sounded in this circuit the most neutral.
Thank you for telling me about your experience with the DEQ2496. The oldest versions of my EQ used 4558 in the filters. The 4560 was an update for later models, and the 4580 I believe is an updated 4560 with both available in "DD" low noise versions. This EQ also has a button to bypass the filter circuit, and I do not hear a change in sound with the 4560. Again, because there are so many filters, I do not see replacing so many ICs as practical for experimentation.
Here is a thread on mods. And the claim of "poor" performance at 19 and 20 khz IMD tests. Some tweaks did not change this.
https://www.diyaudio.com/community/...-mod-what-can-50-do-to-deq2496-part-1.282346/
I had some very revealing fullrange drivers at work for testing the Behringer and distortion beyond 5khz is not very detectable by the ear.
However the ear is very sensitive to amplitude distortion. And here an EQ is doing wonders!
A fault of 2 db in the high frequencies with one octave or more on the long run can make you mad.
Although many think they cannot hear 20kz it was clearly audible if you popped up 20khz on the Behringer up by several decibels. And you could easily reach the stage where it was not funny to have too much output at this frequency.
https://www.diyaudio.com/community/...-mod-what-can-50-do-to-deq2496-part-1.282346/
I had some very revealing fullrange drivers at work for testing the Behringer and distortion beyond 5khz is not very detectable by the ear.
However the ear is very sensitive to amplitude distortion. And here an EQ is doing wonders!
A fault of 2 db in the high frequencies with one octave or more on the long run can make you mad.
Although many think they cannot hear 20kz it was clearly audible if you popped up 20khz on the Behringer up by several decibels. And you could easily reach the stage where it was not funny to have too much output at this frequency.
They may be unity gain buffers for each band.
Check output and - pin for short as they are connected together for buffer duty.
Check output and - pin for short as they are connected together for buffer duty.
True, and the end result may be minimally impactful, so I'm not going to prioritize those.
Attached here is a snapshot of one of the filters. You can make more sense of this than me. I also discovered that in addition to an NE5532 on each input and output buffer as I reported previously, I discovered there is an NJM4560 on the input gain control for each channel. I suspect this would be a good candidate for experimentation.
I've done that in the past using OPA1602 as i had a lot of them. The result was very good but I don't think that using NE5532 would be any different
You replaced all the filter op amps? Which EQ? I don't think I would consider going through all that trouble unless I noted an improvement with discretes on the input gain and input and output buffer positions. If I did experiment with the filters, it would be ICs, not discretes, and with 32 of them, the cost would need to be reasonable. That may not leave many worthwhile options, so it's only a secondary consideration at best.