NOS Mallory capacitors for Rhodes Piano

[diagrammatiks]

no one is going to be able to help you until you actually measure the cap values in the preamp you like.

[Jazz P Bass]

I want to see this here Rhodes on a test bench.
Hooked up to a scope.
The fact that the new caps changed the frequency response of the CIRCUIT means the CIRCUIT can be tailored to your 'taste'.

[Steve Conner]

I just wasted 10 minutes of my life listening to those sound clips on the good system.

Yes, the two Rhodes sounds seem to be different, although it's hard to tell because of all the other crap that JM Fahey pointed out. If you want to demonstrate the difference between two sounds, why are you doing your best to hide the difference by playing the thing through a bunch of effects pedals, EQing the difference away with the tone knobs, and sticking on a cheesy backing track? Play the thing solo with no effects and the controls set the same on both channels.

To me the second one sounds clearer with more high end. It has that bell-like tone that I associate with the Rhodes. The first one sounds grungy like a Wurlitzer 200 played through its built-in speakers.

I stand by my original assertion, the crappy dried-up leaky old caps are distorting the sound somewhat, and you just like that thick, grungy sound. You fixed the other channel, and now it sounds too clean because it's working properly.

When I was 8, my parents were blasting "Pictures At An Exhibition" on a huge stereo, and not the Emerson Lake & Palmer version either.

[gbono]

Poor angel.
Just leave him alone, will you?
I think he by now has learnt not to disagree with Daddy.
We are experienced grownups and, at a distance, are already getting quite fed up with you.
That pressure on a small child must be unbearable.
LEAVE HIM ALONE.
You have been warned.

Amen brother

[Skiroy]

I just wasted 10 minutes of my life listening to those sound clips on the good system.

Yes, the two Rhodes sounds seem to be different, although it's hard to tell because of all the other crap that JM Fahey pointed out. If you want to demonstrate the difference between two sounds, why are you doing your best to hide the difference by playing the thing through a bunch of effects pedals, EQing the difference away with the tone knobs, and sticking on a cheesy backing track? Play the thing solo with no effects and the controls set the same on both channels.

To me the second one sounds clearer with more high end. It has that bell-like tone that I associate with the Rhodes. The first one sounds grungy like a Wurlitzer 200 played through its built-in speakers.

I stand by my original assertion, the crappy dried-up leaky old caps are distorting the sound somewhat, and you just like that thick, grungy sound. You fixed the other channel, and now it sounds too clean because it's working properly.

When I was 8, my parents were blasting "Pictures At An Exhibition" on a huge stereo, and not the Emerson Lake & Palmer version either.

You are absolutely right. I only put the crappy back up tracks because as a recording noobie I have come to realize that you have to listen to things within a mix to know if it works. I spent no time to mix the backing track but I used sounds close to what I normally like. Just by my limited experience it seemed everytime I liked a sound by itself when I put it in the mix I didnt like it then. And the alot of the sounds I didnt like soloed sounded good in the mix. For example synths that by them selves sounded to harsh and cheesy in the mix cut and fit. But anyways you guys are correct and I will try to re record the VV cap version flat like the other and play the same chords.

You are also correct about the fact that I did like the grungy sound better because that is what I like. In fact I got this exact year 1975 for its grungy sound its know for. It was just too grungy.

[Skiroy]

no one is going to be able to help you until you actually measure the cap values in the preamp you like.

You are absolutely correct. I am working on this. I know it can be frustrating trying to communicate things you fully understand to someone who is clueless about your skill. I am a Automation Maintenance Tech. and I also design do some Automation design and it can be frustrating dealing with people on the plant floor that have no idea the complexities if some of the issues I face everyday. So I want to thank people like you and others that have stayed off their high horse to come down to my level. Understand I was perhaps biten off more than I could chew and had to learn basic theory of all this as I was and as I am going. I have do some Mic customizing,rack mounted some old Yamaha pres and repaired studio monitors but it was always through getting the info online but never understanding what I was doing. I was trying to avoid it as I have a problem with wanting to know everything and dint want to plunge into the deep abyss of electronics theory but it seems I have to. But anysways everything always told me that I was in over my head I pulled off. Recently, I calibrated an Oberheim OB-XA and it was a insane learning curve. I was bashed online about to just ship it to a Tech. ,but I finally got it down.The point is I apologize for my stubbornness and thank you for being patient. And I really never get the few that take the time to post when they are annoyed with the poster or "over" the subject. Just go do something else or ignore the little lnik. You know you dont have to click on it. You let some text on a little screen by someone you dont know or will never meet get to you about a subject they dont know about? Come on.

I understand that the capacitance changes the frequency curve. I noticed that the 5MFD and 50MFD caps in the VV are 4.7MFD and 47MFD. And like I said I am working on reading my old caps because I see the importance of this fact.

But
1. I read that generally a higher value means a warmer/darker sound due to a slight high frequency roll off. But with these values is it that sensitive?

2. And typically when a cap degrades does it usually increase or decrease its capacitance? It was said that as they dry out they become more like resistors which I would think that its ability to hold a charge would decrease making its capacitance go down. But I know there is the ESR factor which I am still trying to understand.

I like the grunge yes but defined grunge if that makes sense. I first had to get slapped across the face with the fact that I am going to have to understand more of the fundamentals behind this,then convince myself that I want to go go as far into troubleshooting my own equipment to the point I was going to have to acquire an O scope and a tool to read capacitance. But I think I am ready to take that plunge. Plus what better circuit to start on than one as simple as a Rhodes pre,right? HA HA HA.

[Steve Conner]

A few companies make LCR (inductance, capacitance, resistance) meters that will read both capacitance and ESR of a capacitor. Extech make one that is popular with the pickup winders here.

They're kind of pricey, so hopefully you can borrow one.

Now let's say you measure one of your old caps with a device like this. It says 5uF on the label, but the LCR meter says 2uF and an ESR of 100 ohms. So, where that capacitor was in the circuit, you put a 2uF with a 100 ohm resistor in series.

Another thing that would be useful is to measure all the DC voltages in the circuit with an ordinary digital multimeter. Compare the mojo channel and the sterile one. If you have a schematic with the voltages printed on it, compare them both to that. If you see big differences (more than 10% say) then investigate the reason. Maybe one of the old caps is leaking DC and throwing the voltages off, and a cunningly placed resistor across one of the new caps will emulate it.

Why do I keep posting in this thread? I don't even work in audio, I design industrial electronics for a living. But I'm obsessed with vintage audio gear and why it sounds the way it does. I believe there is always a scientific reason for "mojo" and that you can have it along with reliability and consistency, using sensibly priced modern parts. Except for germanium transistors, I have to concede that those sound pretty bitchin' in a Fuzz Face.

The difference between the two Rhodes sounds was quite subtle. Maybe if you re-record them like we suggested, it'll stand out more.

[Bruce / Mission Amps]

Okay is it ,"In my Head" guys? I think not. I am not a player I am a engineer guy. These tracks have only 1-3db limiting and nothing else. You tell me which one sounds more authentic to you. To me its obvious. One sounds like an old record,but a little mud I wish to get rid of without EQing and the other sound too clean. Like something I could just get with a keyboard.

But you tell me.

BlindSightProductions's sounds on SoundCloud - Create, record and share your sounds for free

That was VERY hard to isolate the actual Rhodes. The second tracking sounded just a tiny bit better to me but the first one has a slightly soft furry edge to it that makes it sound a little sleepy.

[Skiroy]

but the first one has a slightly soft furry edge to it that makes it sound a little sleepy.

Exactly. Furry and sleepy is a good description. It has a more dreamy quality to it and the tremolo sounds smoother to me.

For any intrested
Guitar Tone Capacitors, part 1: Evaluating Material Types - YouTube

Anyways how would the decoupling caps effect the tone when it comes to ESR or degradation? Could these cause crossover distortion? Listening to my original caps soloed I hear distortion at times. Mostly in the upper register. I thought I paid attention to not clip anywhere. But how does the Rhodes preamp work as far as input clipping. It is a preamp so I dont know if the volume know is the input or the output. But what would prevent the input to the preamp(harp) from clip the preamp if Im pounding the keys?

[Skiroy]

Okay guys I finally got my meter. The results are in. The four 5MFD caps read:
6.89MFD,6.24MFD,6.07,6.62 MFD. I guess my ears were correct hearing a warmer/darker sound being that the higher capacitance values usually mean the highs are rolled off some. But I assume that they are all working if the meter is getting a steady capacitance value.

Now the results of the other are:

The one 1 MFD read: 2.3MFD
The four 50MFD read:79.3 MFD,62.5,62.3 and 72 MFD
The 2 100 MFD read: Now these for some reason I have trouble reading. They look like they are charging to get a 3 and 1 nano farad reading for a few seconds on my digital LCR/multimeter but then say "OL". Maybe because they are 100MFD-15V caps. Perhaps this meter is for caps 25V and above. So I dont know if they are bad or just incompatible with my meter,but the resistance on them read 4 Ohms for a few seconds then go to "OL". But doesnt that indicate they are not shorted? I thought when they climb to a resistance and hold for a second then go to "OL" that means they are good?

But these are all the mallory Aluminum Electrolytics. These are all the white axial ones that are apparently the only ones to worry about because the Vintage Vibes cap replacement kit only includes their caps to replace these in. Now like someone mentioned above only the four 5 MFD caps are in the signal path so I dont know what it means for the sound in regards to the capacitance variation in the decoupling Caps. And if the 100 MFD are in fact bad what would that mean in this circuit? The Schemo was posted earlier in this thread.

Thankx.

[J M Fahey]

Nice video.
Much better than the earlier one you had posted, where he changed capacitors but only activeted the tone pot for 1 or 2 seconds and then play with it on 10, negating the cap effect.
Here I hear differences in tone, and all of it attributable to the pot resistance, not the caps.
On 10 they have nil effect (obvious) .
On 7 there is a slight effect.
On 5 they start to be noticeable.
On 1, maximum treble cut, muddying, "mellowing", you name it.
Anyway, asI said, the big change is directly related to the pot resistance value, capacitors themsalves do always the same.
I was surprised because I expected the "Tropical Fish", being a rated 50% higher value, would be noticeably different than the others, but it was practically the same. Didn't expect that.
Any very slight differences in brightness, attack etc, came from , obviously, having a Human playing.
Small variations in finger pressure, hand speed, playing slightly towards the headstock or the bridge, etc.
Somebody answered that how he gripped the pick had an influence too.
A guitar tone capacitor really is not the best way to test caps, because the sound does not go *through* them, but, some of it gets shorted to ground, a very indirect path test.

As of what you are measuring, those values hint at good capaitors.
They are very consistent, within 10% of each other, and only 20% above nominal value.
Incredible.
Remember that usual Factory spec for electrolytics is "-50% / +100%"
These are *way* tighter.
Why don't you measure the WV supplied ones ?
Comparing them will be interesting.
Good luck.

[Gtr_tech]

[QUOTE=Skiroy;249738]

Im trying to get there but this is giving me a problem.

Stratcaster & Capacitor.wmv - YouTube

Pay no attention to those cork sniffers. They're going by misinformation spread via the net....not by readings from test equipment. The more you start swapping parts out over and over, the more you will tear up the traces on those old boards. Those will be harder to track down than some Magic Mojo(r) brand caps....

[Skiroy]

Nice video.

As of what you are measuring, those values hint at good capaitors.
They are very consistent, within 10% of each other, and only 20% above nominal value.
Incredible.
Remember that usual Factory spec for electrolytics is "-50% / +100%"
These are *way* tighter.
Why don't you measure the WV supplied ones ?
Comparing them will be interesting.
Good luck.

What about the 100 MFD any reason why my multimeter wont read it? And what would variation in capacitance in decoupling caps do to the circuit? I now know decoupling caps basically keep the voltage buffered and noise free,so why a variation in capacitance here change anything sonically like how a change in capacitance in the audio path changes the frequency range?

Perhaps certain capacitance values in certain places in the decoupling circuit would introduce slight harmonic distortion which could be part of the "furry" sound I like?

And perhaps going with a 6 MFD would be closer to the sound I want for the 4 caps in the signal path?

Would there be an audible difference frequency wise from a 4.7MFD to 5MFD? Or from a 5MFD to 6MFD?

[Chuck H]

Ahhh...

The most important thing you can take from this thread is that there are significant differences in the components of the two channels you are comparing, not only because of value, but also because of failure. In fact, the supporting circuitry for the two channels (that you haven't changed parts of) is also likely to be significantly different. Note that this difference would be there regardless of the capacitors you changed in the one channel.

This has already been suggested so I'll make this short and sweet. The age of the caps changes their operation. No new cap can do that for you, so in this regard all new caps are created equal. The only way to KNOW what sounds good about the channel you like is to measure all parameters on every component exclusive to that channel. To make the other channel sound the same you could then build circuits to simulate any age related differences between the old components and the new ones. This means you need to measure resistors as well. And voltages. Even decouplung caps that are only in the power supply can affect the sound. Anything exclusive to the channel you like needs to be measured. And not just for value. You also need to measure ESR and leakage. To the circuit a new capacitor just looks like a capacitor. But the old capacitor looks like a capacitor in parallel with a resistor and then in series with another resistor. So you need to measure the capacitor value, it's ESR and it's leakage in order to design a new circuit that does what the old capcitors are doing.

There is no point in complicating the issue further with questions about diodes, which new capacitor is most like the old ones or what different values do to the sound. In a situation as complicated as yours the only thing you can do is scientifically break it down to it's constituate parts and reconstruct it with currently available materials.

Another possible answer would be to simply rebuild the whole piano so that it's working like new and then make much simpler overall modifications to alter the sound by ear until you like it. The this would be a much simpler and more repeatable circumstance to deal with in the future.

Again, please stop complicating the issue. All you need to know about this problem is written in this thread. The exception being that a reasonable hobby level understanding of electronics will be needed to understand the significance of what posters here are trying to tell you.

I hope you find piano bliss.

[J M Fahey]

Agree and add, answering your new questions:
1) your multimeter probably reads up to 100uF and that unit (remember +100%/-50%) is over that.
Multimeters do not actually measure capacitance (as in a Bridge) but apply a certain current to it for a given time and measure Voltage across their terminals.
Then calculate the uF value.
Obviously yours takes "too much" to charge (because it's over 100uF) and your multimeter quits, showing Over Range (which is true).
2) decoupling caps usually have a minimal influence in sound, simply because they are usually overkill, and in that case it's good "Engineering practice".
Nobody will design "on the edge".
Imagine a decoupling leg calls for, say, 1.2uF in a certain place, by calculation.
If you use less you have more hum than acceptable, or , even worse, instability and motorboating which would alter the sound.
*Any* designer will certainly use 4.7uF or 10uF , and a few will slap 100uF there.
Why?
Because they cost about the same !!!!!!!!!!
Believe ,me, I design and sell amplifiers for a living, and, unfair but true, *cost* is the most important "technical" and "sound" parameter in a competitive world, yet I, like all others, use the larger values there.
And, more to the point, a capacitor used in a tone control or as a bypass capacitor needs a certain calculated value, no more or less, but on decoupling caps, the more the merrier.
So by sheer size they are removed from the sonic equation.
The only exception is in the main filtering cap(s) at the PSU, the largest and most expensive in the amp, where using too much means spending too much or using too much space, but ... in a Preamp? , no ($) problem. !!
And no distortion in decoupling caps, their function is different.
3) *measured* 6uF *means* a 5uF label. It's well within tolerance.
And putting a rotary switch and substituting the original one with, say, 4/5/6/7 uF won't change the sound.
I don't have the circuit present but it will mean that the low frequency cutoff will vary from, say, 10Hz to 6Hz , way below the audible range.

Back to the main problem:
4) your caps are fine, don't know why you would want to change them, leave as-is.
5) if you have 2 preamps,, and they do not sound the same: it's possible, why not?, but they have about, say, 100 components each.
Focusing *exclusively* on 4 electrolytic capacitors is not the answer, by a long , very long shot.
6) if you want to turn the "cold" one into the "warm/fuzzy" one, forgive me, but you won't.
You won't be able to find *all* the original parts.
If you do they will be different (as you have already tested) because of normal manufacturing tolerances
Even if they were exactly the same value when just made (30 years ago), now they have drifted *differently* because some of them lived in a working, hotter (as in temperature) preamp, while the NOS ones were unconnected, sleeping in a box, in a dark and fresh (and probably humid) place.
7) If I may suggest something, if you are unhappy with your sound, keep your piano for now but at a very relaxed pace start hunting for a Rhodes (yes , a full one, not just a preamp) which sounds "just right".
Buy it, sell yours, so you'll recover most of the expense, and be happy.
Good luck.