I have a studio mixer. You can see below the type of opamp (phono pre amp they implement (njm4580)
Please evaluate how good this design is from sound quality perspective, to see if it is worth to replace phono section with better sounding design.
Mixer power supply is +/- 17.5Vdc.
I use this mixer for listening to vinyl with MM cartrige. Sound quality is important here.
1. Is this a single opamp type with active eq?
2. What are advantages/disadvantages of this topology?
3. It is interesting to note that max voltage on this opamp is 18v. Mixer runs at 17.5v. Maybe this maximizes the SQ of this njm4580
thanks,
Herman
Please evaluate how good this design is from sound quality perspective, to see if it is worth to replace phono section with better sounding design.
Mixer power supply is +/- 17.5Vdc.
I use this mixer for listening to vinyl with MM cartrige. Sound quality is important here.
1. Is this a single opamp type with active eq?
2. What are advantages/disadvantages of this topology?
3. It is interesting to note that max voltage on this opamp is 18v. Mixer runs at 17.5v. Maybe this maximizes the SQ of this njm4580
thanks,
Herman
Hi,
Can't see the circuit, but change the 4580 to 5332.
Cheap, simple and effective.
rgds, sreten.
Can't see the circuit, but change the 4580 to 5332.
Cheap, simple and effective.
rgds, sreten.
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To correct a typo that means an NE5532N or the premium version NE5532AN. If you are going to take out the 4580 you can fit an 8 turned pin IC socket on the board in its' place - giving you the option to audition other devices and make comparisons. The 5532 types will drive a 600 ohm load. The LM833N is not quite up to that but it is even cheaper and has a slightly better noise specification. If you use a socket make sure the indent on the socket faces the same direction as the one on the chip.
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This is a similar circuit to the one in my Herald Electronics RA88a disco mixer. Except the capacitor values are a tenth of these, and the feedback resistor is 1 megohm. That makes for a pretty good sound, but people on here told me by buying more expensive 10x capacitors and cutting the resistor a tenth it would hiss less. Bought the parts but haven't torn into it yet. I replaced 4558, which were hissy, with 33078, which isn't. I don't know the 4580 is all that bad, Peavey uses a lot of them in mixers for condensor microphones, which are very low level like MM cartridges. I can't evaluate 5532, my East Coast usual sources only sell 5532 in 14 pin packages which don't fit in anything audio. If I want to spend $12 shipping from the West Coast for one type of op amp, I might try some, but the $.038 33078's sound fine, a few LM4562 are in the parts box for $2 each, why go backwards in time.
BTW I own a "legendary" Dynaco PAS-2 tube preamp with magnetic phone, it has one advantage over the RA88a op amp mixer on MM cartridge using speakers, the hum is a little less on the PAS-2 than the RA88a. The PAS-2 had metal film resistors over 91 kohm installed 2011, new electrolytic caps, silicon instead of selenium heater rectifier, and polyester capacitors since one of the paper ones failed. Now the PAS-2 is a bit brighter than it should be with the plastic capacitors, so the RA88a is actually flatter response now IMHO unless I cut the treble tone control some on the PAS-2.
BTW I own a "legendary" Dynaco PAS-2 tube preamp with magnetic phone, it has one advantage over the RA88a op amp mixer on MM cartridge using speakers, the hum is a little less on the PAS-2 than the RA88a. The PAS-2 had metal film resistors over 91 kohm installed 2011, new electrolytic caps, silicon instead of selenium heater rectifier, and polyester capacitors since one of the paper ones failed. Now the PAS-2 is a bit brighter than it should be with the plastic capacitors, so the RA88a is actually flatter response now IMHO unless I cut the treble tone control some on the PAS-2.
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From the perspective of SQ, the power supply details are crucial but they aren't shown on the schematic.
One point of particular interest is the loading on the RIAA stage at high frequencies. Its fairly heavy (27n - 10n - 100R - 470uF) meaning a large amount of supply noise gets generated. If this isn't reduced by judicious decoupling the sound will suffer.
One point of particular interest is the loading on the RIAA stage at high frequencies. Its fairly heavy (27n - 10n - 100R - 470uF) meaning a large amount of supply noise gets generated. If this isn't reduced by judicious decoupling the sound will suffer.
I find 33078 to be an O.K. chip for my own needs, this and some 1988 LM833's which sound sweeter than the current production ones - I am waiting on an order for some more 33078's. I have a couple of NE5532AN or N in my collection and LM4562's.
I won't be ordering any more of these.
On Semi do a surface mount 14 pin job it is included on the NE5532 datasheet but the prefix is SE. It could be that NE5532 were once available in dual in line packages and it could be the supplier has acquired a lot of obsolete stock.
I see comments on the actual opamp. How about the fundamental design of the phono stage. One opamp with active RIAA? Is this a good idea, other than low cost? As far as audiophile DIY designs most seem to go for discreet or opamps with passive Riaa.... Is there a good reason for that?
Herman
Herman
Unwittingly the packaging for the 4580 chip the E suffix was not disclosed by the original post and the circuit was posted some time after the discussion had gotten under way. I spotted this only after I had made a couple of posts myself.
That leaves the discussion back where it started - about surface mounted 8 pin dual IC operational amplifiers.
The circuit uses series feedback, a characteristic of which is that the gain can never be less than one. The RIAA curve requires that the frequency is 20 dB down at 21215 hertz and the output continues to fall with increasing frequency beyond that to zero at some point. The gain factor of one mitigates against this. Some designers add an RC network at the output to keep the response on this course.
It may be practical to do this with your circuit if you don't mind cutting some tracks and soldering the components on the back of the board.
Please evaluate again
As mentioned in the original post, I would ask an experienced builder/designer to evaluate the attached phono diagram in terms of sound quality capability
What I am looking for is general advice such as: this design is good at this and this... or is doomed to never sound very good because... or is optimized for low noise with no regard to sound quality, etc...
I hope you get my point.
This advice will help me decide:
1. should I stick to the original design (because it is good) but try different opamp.
2. modify this design to a reasonable extent
3. scrap this phono all together and insert a better design
The goal: exceptional sounding phono section, with little compromise. I know this phono section does not "have it all" in terms of sound because I compared it to others.
Additional Notes:
From my listening tests, this phono is quiet, has dynamic, balanced sound but is noticeably lacking in detail and spaciousness reproduction, roughening up the delicacy of music, hardening the highs.
With all the expensive, high end solid state or tube phono stages out there this circuit seems extremely basic. What in this circuit gives it the sound quality it possesses?
On the other hand, what sound qualities do the more elaborate designs possess compared to this circuit?
thank you,
Herman
As mentioned in the original post, I would ask an experienced builder/designer to evaluate the attached phono diagram in terms of sound quality capability
What I am looking for is general advice such as: this design is good at this and this... or is doomed to never sound very good because... or is optimized for low noise with no regard to sound quality, etc...
I hope you get my point.
This advice will help me decide:
1. should I stick to the original design (because it is good) but try different opamp.
2. modify this design to a reasonable extent
3. scrap this phono all together and insert a better design
The goal: exceptional sounding phono section, with little compromise. I know this phono section does not "have it all" in terms of sound because I compared it to others.
Additional Notes:
From my listening tests, this phono is quiet, has dynamic, balanced sound but is noticeably lacking in detail and spaciousness reproduction, roughening up the delicacy of music, hardening the highs.
With all the expensive, high end solid state or tube phono stages out there this circuit seems extremely basic. What in this circuit gives it the sound quality it possesses?
On the other hand, what sound qualities do the more elaborate designs possess compared to this circuit?
thank you,
Herman
Hi,
Replacing the 4580 with a 5532 will make the mixer
likely as good as its ever going to get, given the
rest is TL07X based, a common "hifi" combination.
There is nothing wrong at all with single stage RIAA in this case.
Things might improve looking at the power supply and general
layout issues, this sort of thing is easier to get wrong than right.
(Including connector / switching issues, can be a real pain.)
If you have a suitably high quality and expensive vinyl source
and the rest of the system to match, no it won't do as a phono
/ line stage, because its basically level 1 studio quality, i.e.
amateur recording / decent live quality, nothing special.
However if the vinyl source and system are pretty mundane,
no exotic phono / line stage will make much real difference.
rgds, sreten.
Replacing the 4580 with a 5532 will make the mixer
likely as good as its ever going to get, given the
rest is TL07X based, a common "hifi" combination.
There is nothing wrong at all with single stage RIAA in this case.
Things might improve looking at the power supply and general
layout issues, this sort of thing is easier to get wrong than right.
(Including connector / switching issues, can be a real pain.)
If you have a suitably high quality and expensive vinyl source
and the rest of the system to match, no it won't do as a phono
/ line stage, because its basically level 1 studio quality, i.e.
amateur recording / decent live quality, nothing special.
However if the vinyl source and system are pretty mundane,
no exotic phono / line stage will make much real difference.
rgds, sreten.
See post 6 above - HF hardness is a giveaway for high frequency power supply noise.
Or radio frequency pickup via magnetic input.
There is no filter on the input of your phono stage only 100 p.f. of capacitance to load the cartridge. Some cartridges notably Ortofon specify a higher capacitance load and although the leads from the player to the input will add capacitance it is not always enough. You would need to check on the specifications for your cartridge and measure work out the capacitance in the leads by themselves. You would investigate that before thinking about a passive filter on the phono input. Magnetic cartridges can have a peak in their response if they are not damped with the correct capacitive load.
To go a little further, magnetic cartridges are resonant devices and use of this is made of that property to extend the frequency response at the top end of the audio range.
There is no filter on the input of your phono stage only 100 p.f. of capacitance to load the cartridge. Some cartridges notably Ortofon specify a higher capacitance load and although the leads from the player to the input will add capacitance it is not always enough. You would need to check on the specifications for your cartridge and measure work out the capacitance in the leads by themselves. You would investigate that before thinking about a passive filter on the phono input. Magnetic cartridges can have a peak in their response if they are not damped with the correct capacitive load.
To go a little further, magnetic cartridges are resonant devices and use of this is made of that property to extend the frequency response at the top end of the audio range.
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Hi,
In my youth I religiously mucked about with capacitive loading,
it makes a difference, but not much unless its very wrong.
Similarly the lack of series feedback ability to maintain the
the RIAA rolloff into ultrasonics is completely irrelevant,
(possibly useful for CD4), unless the design is awful.
rgds, sreten.
In my youth I religiously mucked about with capacitive loading,
it makes a difference, but not much unless its very wrong.
Similarly the lack of series feedback ability to maintain the
the RIAA rolloff into ultrasonics is completely irrelevant,
(possibly useful for CD4), unless the design is awful.
rgds, sreten.
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someone already commented about the HF rolloff correction needed for good accuracy.
for single opamp designs, you also have to worry about having sufficient open loop gain to keep distortion low at the gains you select. i did not review the opamp specs or the values in your design to check for any concerns on that front.
for low noise, it's recommended to use low impedance feedback components. however, those can load the output more and can drive distortion up, especially at higher frequencies when the op amp gain diminishes and the capacitive impedance gets lower, etc. some people add a buffer after the op amp to deal that. i'm not familiar with the NJM4580; just the same, i'd probably use a (genuine, as in watch out for fakes) nice jfet input part like the OPA627 or OPA827 for a mm cartridge. also, i'm not the biggest fan of electrolytic coupling caps, especially unbiased.
and oh yeah, don't use a sleazy power supply; give it something nice.
🙂
single op amp RIAA preamps can sound ok. mcintosh has done it for years and they're still in business. i think their top line solid state preamp uses the "lowly" NE5534A as the gain stage. 🙂
have fun & hope this helps...
mlloyd1
for single opamp designs, you also have to worry about having sufficient open loop gain to keep distortion low at the gains you select. i did not review the opamp specs or the values in your design to check for any concerns on that front.
for low noise, it's recommended to use low impedance feedback components. however, those can load the output more and can drive distortion up, especially at higher frequencies when the op amp gain diminishes and the capacitive impedance gets lower, etc. some people add a buffer after the op amp to deal that. i'm not familiar with the NJM4580; just the same, i'd probably use a (genuine, as in watch out for fakes) nice jfet input part like the OPA627 or OPA827 for a mm cartridge. also, i'm not the biggest fan of electrolytic coupling caps, especially unbiased.
and oh yeah, don't use a sleazy power supply; give it something nice.
🙂
single op amp RIAA preamps can sound ok. mcintosh has done it for years and they're still in business. i think their top line solid state preamp uses the "lowly" NE5534A as the gain stage. 🙂
have fun & hope this helps...
mlloyd1
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