Hey everyone trying to replace some parts in a bass guitar onboard preamp from 1998
any idea if I can change the electrolytic caps to film?
and can I change the op amp for a
TLE2082
any idea if I can change the electrolytic caps to film?
and can I change the op amp for a
TLE2082
No reason you couldn't other than size - would they fit on the board? I suspect they would be huge.
What do you hope to gain from the op amp swap? The2062 is a low current type isn't it? Would your 2082 also be low current? Battery life is an issue.
What do you hope to gain from the op amp swap? The2062 is a low current type isn't it? Would your 2082 also be low current? Battery life is an issue.
Most of the electrolytic capacitors in that circuit are 22uf, and I think, as Enzo says, you would find them impractically large.
There are some electrolytic capacitors designed specifically for audio signal path use by Elna and Nichicon, so if you felt the urgent need to upgrade, you might consider those.
There are some electrolytic capacitors designed specifically for audio signal path use by Elna and Nichicon, so if you felt the urgent need to upgrade, you might consider those.
It is a Bass Guitar, so a limited range instrument.
No need for Bass response below lowest string frequency produced, some 40Hz, nor higher frequency than highest significant harmonic of the highest note, so some 5kHz.
So any "improved" Op Amp will be wasted, except if you get a lower noise one, but nothing beyond.
It is not a Hi Fi preamp where minimum spec to deserve that label is ruler flat from 20Hz (which you don´t have) to 20kHz (neither) .
Hi Fi preamps often boast of even more extended response, say 2 or 5Hz to, say, 50kHz or 100kHz, mainly to guarantee perfect response in the Audio band, not needed here.
Same about aiming to sub-zero distortion: in fact string Musical Instruments can benefit from "a little" distortion even when used nominally "clean", or sound is often labelled as "boring clinical", go figure.
Tubes are well liked , in part because they introduce some nonlinearity (a.k.a. distortion) to add some "flavour".
Of course it doesn´t hurt having a cleaned and flatter Op Amp, simply you won´t enjoy any audible "improvement"
For the same reasons, it is not worth going to film caps, besides the obvious size problem.
In a nutshell: using "better parts" often leads to no or minuscule improvement, the REAL improvement comes from bettering THE DESIGN.
Of course, anybody who can solder can replace parts, now to improve the design requires knowledge and experience, so it´s not very popular.
For example, that Millenium preamp has a somewhat crude design which has a real effect on sound and quality, yet you are not addressing that by any means.
visible errors (or at least areas to improve):
1) "the most important Op Amp is the first one" since it processes the weakest signal .... but those are active pickups, there is at least one Op Amp embedded in each one (fed by that 18V rail), yet you can´t touch it, not even see it, it´s potted inside, let alone replace it with a better one.
2) it uses a crude Blend pot.
Normal pots get signal at the hot terminal, which exits through the wiper, which among other things allows for a relatively constant load to signal source , as low as possible output impedance (for a passive part) and when set to 0 shorts the output, for lowest hum and noise.
None of that here where signal enters through the wiper and exits through "hot", so:
* signal source gets variable (and always too low) load, including shorting it when set to 0 and very very low load when set to lower levels.
* network output impedance is high over most of the travel, and maximum when both pickups are set for same level (50%) .... which is a very common setting.
* which leads to problem #3:
3) Baxandall tone controls need being fed from as low an impedance as possible for best results, but here signal comes from that cheesy Blend pot network.
It would improve if a buffer were inserted between them, I show the best place for it.
4) tone control Op Amp shows a treble murdering network: R102//C105.
220k plus 470pF have a turnover frequency of 1500Hz 😱
In practice somewhat higher because the whole EQ network is in parallel with R102, and it uses 50k pots, but hey, that will severely mask any possible "improvement" brought by using "better parts".
In a nutshell: real improvements are far away from what an average user can do, because they are achieved at the design bench.
Part swapping is justified only if VERY old or incompetent parts are present, say replacing a very noisy 741 by a more modern one, or dried up caps by fresh ones, not much beyond that.
No need for Bass response below lowest string frequency produced, some 40Hz, nor higher frequency than highest significant harmonic of the highest note, so some 5kHz.
So any "improved" Op Amp will be wasted, except if you get a lower noise one, but nothing beyond.
It is not a Hi Fi preamp where minimum spec to deserve that label is ruler flat from 20Hz (which you don´t have) to 20kHz (neither) .
Hi Fi preamps often boast of even more extended response, say 2 or 5Hz to, say, 50kHz or 100kHz, mainly to guarantee perfect response in the Audio band, not needed here.
Same about aiming to sub-zero distortion: in fact string Musical Instruments can benefit from "a little" distortion even when used nominally "clean", or sound is often labelled as "boring clinical", go figure.
Tubes are well liked , in part because they introduce some nonlinearity (a.k.a. distortion) to add some "flavour".
Of course it doesn´t hurt having a cleaned and flatter Op Amp, simply you won´t enjoy any audible "improvement"
For the same reasons, it is not worth going to film caps, besides the obvious size problem.
In a nutshell: using "better parts" often leads to no or minuscule improvement, the REAL improvement comes from bettering THE DESIGN.
Of course, anybody who can solder can replace parts, now to improve the design requires knowledge and experience, so it´s not very popular.
For example, that Millenium preamp has a somewhat crude design which has a real effect on sound and quality, yet you are not addressing that by any means.
visible errors (or at least areas to improve):
1) "the most important Op Amp is the first one" since it processes the weakest signal .... but those are active pickups, there is at least one Op Amp embedded in each one (fed by that 18V rail), yet you can´t touch it, not even see it, it´s potted inside, let alone replace it with a better one.
2) it uses a crude Blend pot.
Normal pots get signal at the hot terminal, which exits through the wiper, which among other things allows for a relatively constant load to signal source , as low as possible output impedance (for a passive part) and when set to 0 shorts the output, for lowest hum and noise.
None of that here where signal enters through the wiper and exits through "hot", so:
* signal source gets variable (and always too low) load, including shorting it when set to 0 and very very low load when set to lower levels.
* network output impedance is high over most of the travel, and maximum when both pickups are set for same level (50%) .... which is a very common setting.
* which leads to problem #3:
3) Baxandall tone controls need being fed from as low an impedance as possible for best results, but here signal comes from that cheesy Blend pot network.
It would improve if a buffer were inserted between them, I show the best place for it.
4) tone control Op Amp shows a treble murdering network: R102//C105.
220k plus 470pF have a turnover frequency of 1500Hz 😱
In practice somewhat higher because the whole EQ network is in parallel with R102, and it uses 50k pots, but hey, that will severely mask any possible "improvement" brought by using "better parts".
In a nutshell: real improvements are far away from what an average user can do, because they are achieved at the design bench.
Part swapping is justified only if VERY old or incompetent parts are present, say replacing a very noisy 741 by a more modern one, or dried up caps by fresh ones, not much beyond that.
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What was can I increase treble response ?
Clarity not shrill
and how would I throw a buffer? If I replace the balance control with an EMG ABC it has a buffer builr in
I apologize for the posts but. I’m really great full ! I’m looking at pursuing electronics and I’m just learning
1) those parts are fine and will work well.
Which does not mean sound will change appreciably.
2) preamp is already flat enough for the signal it is receiving, if you want more high end you must add equalization.
A "bright" control (boost everything >1600Hz), a Presence control (same but starting at 800Hz), or a peak between 2500 and 4500Hz (your choice).
3) If you really want to experiment, build an external 4 band parametric filter and enjoy, those are really powerful and allow fine tuning.
Of course, use fresh roundwound strings.
A unity gain buffer can be very simple, and sit between blend and tone controls, prblem is youbare cloning the original Peavey PCB which is full of components and tracks wall to wall, not much free space there, and you are limited because it must fit your current Bass cavity, that´s why I suggest you build it as-is so it fits and anything else is external, housed in a pedal box or even in a rack type cabinet.
In a nutshell: given your requirement, clone that PCB as is, I mentioned some PCB design packages allow you to open an image or picture on screen, such as the fuzzy image shown in the Service Manual (which is fuzzy on purpose, to avoid cloning) and redraw your own using it as a guide.
You can even use some "graphic" design software such as Corel Draw, Photoshop or some 2D CAD to trace and redraw that fuzzy PCB image, then you thermal/toner transfer it or print a transparency and use photosensitive PCB.
But you need a clean black-on-white image first.
Which does not mean sound will change appreciably.
2) preamp is already flat enough for the signal it is receiving, if you want more high end you must add equalization.
A "bright" control (boost everything >1600Hz), a Presence control (same but starting at 800Hz), or a peak between 2500 and 4500Hz (your choice).
3) If you really want to experiment, build an external 4 band parametric filter and enjoy, those are really powerful and allow fine tuning.
Of course, use fresh roundwound strings.
A unity gain buffer can be very simple, and sit between blend and tone controls, prblem is youbare cloning the original Peavey PCB which is full of components and tracks wall to wall, not much free space there, and you are limited because it must fit your current Bass cavity, that´s why I suggest you build it as-is so it fits and anything else is external, housed in a pedal box or even in a rack type cabinet.
In a nutshell: given your requirement, clone that PCB as is, I mentioned some PCB design packages allow you to open an image or picture on screen, such as the fuzzy image shown in the Service Manual (which is fuzzy on purpose, to avoid cloning) and redraw your own using it as a guide.
You can even use some "graphic" design software such as Corel Draw, Photoshop or some 2D CAD to trace and redraw that fuzzy PCB image, then you thermal/toner transfer it or print a transparency and use photosensitive PCB.
But you need a clean black-on-white image first.
The 220k is in shunt with the Bax network, is deliberately "much higher" than the Bax. It just sets DC bias. Note that the 470pFd becomes in-shunt with the 0.01uFd (10,000pFd) in the Bax, suggesting top rolloff about 4 octaves higher than tone turnover, maybe 30kHz.
I'm not impressed with the Blend pot shorting-out the preamps because I'd be sure Peavey put some impedance in there.
I'm not fond of Peavey but most of their stuff is/was much better than users say.
I get sticky on these. What is the existing signal to noise ration and how much improvement are you expecting? And better audio quality and response? What does better mean? Flatter? Less flat? more dynamic range?
https://soundcloud.app.goo.gl/abcJ1Cxw9mw5N4ft5
https://soundcloud.app.goo.gl/J7HCvquthf432UnR8
I’ve done the caps with Nichicon muse in the and it worked super well!
I just have one extra and I wanted to experiment
Before and after
Using a video, playing bass. And a screenshot at the first sight of signal held
I heard a difference enough
I was just looking to see how I can better improve everything overall
fact I’m sure the easiest options to just find a replacement
I’m actually working with a cirrus preamp
Not the millennium
Among peavey bass players these preamps are desirable and out of stock/ discontinued
I would like to clone the preamp but I’m just getting started I’m not sure where to take this
I like the smaller form factor with leads I can use to the pots as I know spiders are hard to find
https://soundcloud.app.goo.gl/J7HCvquthf432UnR8
I’ve done the caps with Nichicon muse in the and it worked super well!
I just have one extra and I wanted to experiment
Before and after
Using a video, playing bass. And a screenshot at the first sight of signal held
I heard a difference enough
I was just looking to see how I can better improve everything overall
fact I’m sure the easiest options to just find a replacement
I’m actually working with a cirrus preamp
Not the millennium
Among peavey bass players these preamps are desirable and out of stock/ discontinued
I would like to clone the preamp but I’m just getting started I’m not sure where to take this
I like the smaller form factor with leads I can use to the pots as I know spiders are hard to find
Ok then what’s your advice for making sound appreciate more?
Change the 22UF to bi polar? Or use ceramic caps?
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if I don’t need blend..
Should I remove C104?
As in a single active pickup wired to the preamp
volume bass middle treble
Should I remove C104?
As in a single active pickup wired to the preamp
volume bass middle treble
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And added:
If you quote me, please quote in full, you missed:
I said "1+2+3", you are correcting me and saying "no! NO! the answer is 3+2+1" 😉
And that´s my point, having high impedance signal sources is BAD for straight driving a Baxandall network.
That preamp would benefit from a buffer exactly where I suggested.