Vox Kensington V1242 "G" tuner.

[vintagekiki]

It's not a solution to use integrated circuit in vintage amplifier.
Amplifier must be authentic. Any modifications must be appropriate time production.
If you decide to use integrated circuits (this is no vintage solution), it's so much better to use Mostek MK50240 top octave frequency generator instead of CD4060.
About value tone G.
International standard for the tone A is 440Hz, but used frequency from 441 to 445Hz. Frequency tone G depends on the chosen standard for tone A.
Value frequencies G 195.998 Hz or 195.997718 Hz depends on the accuracy of calibration instrument which is measured frequencies. In the amateur measurement conditions we can only talk about approximate values.

[R.G.]

I feel I need to preface my remarks with the following. I bear no animosity to you, vintage. I'm just expressing my opinion, heavily salted with what I know to be facts. I try to say when I'm stating an opinion. If something is a matter of opinion, your opinion and mine are of equal value, and I respect that. Facts are just that, facts, and not susceptible to opinion. Mother Nature doesn't care what I think about natural law and her other Rules. They just are.

It's not a solution to use integrated circuit in vintage amplifier. Amplifier must be authentic. Any modifications must be appropriate time production.

I believe that this is your opinion, and it is certainly valid for any amplifiers you own. As for my amplifiers, I much prefer that they work than that they are all original but cannot be made to work correctly. For my amplifiers, I will make them work correctly, whether the perfect vintage part can be obtained or not.

My opinion is that an amplifier that cannot be made to work correctly has value only as a piece of sculpture might - worthwhile for how it looks, and any emotional attachment it has, but not useful as a tool for making music. I personally cannot afford to keep pieces of sculpture that do not function.

So for my amplifiers, I choose to make them work, however that is done. I have gone to some extraordinary lengths to make them work. I include in this learning how to wind the peculiar and unavailable driver transformers inside the power amplifiers in the Thomas Vox amplifiers. I'm in the middle of testing a replacement for the Thomas Vox Royal Guardsman driver transformer. However, I do not accept (for my amplifiers; your opinion may be different) that I cannot make an amplifier work because I can't get the correct "vintage" part.

And I'll extend the same offer to you as I have to others. If you have a Vox amp that cannot be made to work properly because a vintage part is not available, I'll be happy to buy it from you at a suitably non-vintage price.

If you decide to use integrated circuits (this is no vintage solution), it's so much better to use Mostek MK50240 top octave frequency generator instead of CD4060.

You are correct in that an integrated circuit is not a vintage solution. However, it does work, and is both cheaper and potentially more accurate than the original solution.

In my opinion, when you decide to use an integrated circuit, you must choose which way to proceed. The MOSTEK MK50240 is a great solution. But it has some problems. The first one is availability. There may be someplace to buy MK50240s. I have one in my workshop that I'm saving for the right application. It's been there for 20 years, waiting.

If you have to buy an MK50240, I'm not sure where you could find one; worse, if you found one, it would be very expensive. I do know that the MK50240 has not been made for decades, and the only actual price I found for it just now was US$33, and that was for a "replacement", not the actual part. The MK50240 uses a 2.00024MHz crystal to generate the top octave of the musical scale, starting with divide by 239 to get C at 8269.2Hz. The top octave A is 7043.098Hz, four octaves up from A = 440Hz. It provides G at 6270.3448Hz, which is five octaves up from G=195.998Hz and six octaves up from G = 97.9988Hz, which is the fundamental of the high G string on a bass.

So if one could find an MK50240, one would still have to either use a 2.00024MHz crystal (a 2.0000MHz is close enough) to get the top octave then divide down by five or six octaves to get the right frequency, or one would have to find a lower crystal; 1.00MHz, 0.5000MHZ, 250kHz, or 125kHz. Or both. A second divider chip to do several octaves down is probably cheaper than a sub-1MHz crystal (I think! I'd have to look it up.) and the dividers can be had for under US$0.50. The CD4024 works, as do the CD4040 and CD4060.

As a matter of preference I personally would prefer to just use the CD4060 and tune the oscillator to it.

Hmmm. This made me think. I wondered if there happened to be a crystal that would make the CD4060 come out right on frequency. It can take a crystal for a frequency element too. And it turns out there is. 97.998859Hz times 1024 is 100350.8316Hz. You can actually get 100,000 Hz crystals! Mouser Electronics lists one for US$0.76, one for $1.00 and one for $1.58, the last being a 20ppm tolerance.

But that's not exact. 100,000 is not equal to 100,350.8316. But it is only 0.350816 low, and that corresponds to our 6 cents of error. So you actually could use a CD4060, a 100kHz crystal, and come out with 97.9988Hz at less than the perceptible error for musical tuning. Note that because you're using a 4060, you also get the six octaves up from 97.9988 at the same time, so you can also get 195.9977Hz, 391.995... and so on. So it give you the choice of turning out the original frequency or the correct frequency. Wow. I didn't expect that would work out.

To RNG: Hey, I finished the design... You need a CD4060, a 100kHz crystal, two 12pF caps, and about four resistors.

International standard for the tone A is 440Hz,

You are absolutely correct. The frequency standard is A=440Hz. I use A = 110Hz, exactly two octaves down in my work because (a) it's **exactly** 1/4 of A = 440 and (b) it's handier in guitar work. But 440.000000 is the standard. Starting two octaves up at A=440 still gets you to low G on a bass guitar of 97.9988... Hz. You just have to traverse two more octaves to get there.

but used frequency from 441 to 445Hz. Frequency tone G depends on the chosen standard for tone A.

Historically, and up to the present day, many soloists tend to pitch their instruments a bit sharp to "stand out from the mix" and have done so for centuries. In the 1400s through 1800s, orchestras and organs crept higher and higher in pitch as a result.

Value frequencies G 195.998 Hz or 195.997718 Hz depends on the accuracy of calibration instrument which is measured frequencies. In the amateur measurement conditions we can only talk about approximate values.

This is correct. If you start at a different place, you end up in a different place. Modern frequency measuring instruments tend to be crystal controlled, and have un-trimmed errors in the 20-30ppm range, about 0.002% to 0.003%. This is true even for cheap frequency measuring devices. Some are worse, certainly, but the basic accuracy of a frequency measurement device depends primarily on the timing source.

The underlying mathematics of one octave being a frequency ratio of 2.0000000000 and one even-tempered semitone being the twelfth root of two, about 1.059463... and the value for a cent do not change with any change in starting place, though.

I very much respect that your opinions are worth entirely as much as mine. In between the facts, there is always room for opinion and personal preference. I try to keep the two separated, and sometimes do better, sometimes worse.

So summing up this long winded reply:
- Your opinion is that vintage amplifiers must be repaired with only vintage-era parts.
- I believe that I would rather have an amplifier work than be vintage but not work because I can't get a vintage part.
- MOSTEK MK50240 can be used to generate the right frequency for the tuner.
- MK50240 is rare and expensive.
- CD4060 can generate the correct frequency, and can be either LC-controlled or crystal controlled.
- The current even tempered musical scale frequency standard is A = 440Hz, not A = 110Hz.

[vintagekiki]

Not a word about vintage or no vintage parts. When I rebuild vintage amplifiers, does not change anything in the schematics. Replaced only faulty components with new, rewind burnt transformers, repair inductor is not problem, when you have a core with high Al factor, but original schematics is original schematics and does not change. Deviation from the original schematics is some new amplifier in old chassis.
It is a great mistake to expect from the vintage amplifier, the sound of modern current production. Vintage amplifier has a vintage sound.
I respect your opinion, but I see no reason for long detailed answers. Maybe we do not understand because of my poor language. I go back to thread Vox Kensington V1242 "G" tuner.

[R.G.]

And as I said, I respect your opinion. I wish you luck with your work.

[redneckgeek]

I am 66 years old. I went to my first electronics school in 1964. My father was an engineer. I grew up around electronics. I still spend time searching online for anything I can find that he was involved in. Throughout the years I've taken other courses in electronics, (and I've forgotten the same stuff twice or three times). My passion is working on music stuff. I can get just as happy with a Fender tweed or old Vox amp as well as I can with a digital effects unit. Sometimes I spend ten or fifteen hours studying about things knowing my customer could never actually pay for it. So thanks to all of you for your input. I'm enjoying it all. When I make the decision to fix or builsd something I'll be sure to document it and share it with you. Thanks again.

[p1_ind]

I have a Vox Kensington that I am working on. I can not get the scans of the schematics to come up. Does anyone have these saved somewhere. I would be very grateful!
I am mainly interested in the tone section as I want to replace the line reverse switch (which after I replace the caps and add a 3 prong cord I won't need) with a DPDT slide switch to change capacitor values in the tone circuit so it can be used on bass and guitar better. Thanks in advance.

[vintagekiki]

Vox Kensington V1242 schematics

http://bee.mif.pg.gda.pl/ciasteczkowypotwor/SM_scena/VOX/Vox%20Kensington%20Power%20Amp%20Schematic.pdf

http://bee.mif.pg.gda.pl/ciasteczkowypotwor/SM_scena/VOX/Vox%20Kensington%20Preamp,%20Power%20Supply%20Schematic. pdf

http://bee.mif.pg.gda.pl/ciasteczkowypotwor/SM_scena/VOX/Vox%20Kensington%20Preamp%20Schematic.pdf

[p1_ind]

Thanks vintagekiki!

That helps quite a bit. Now I have to pony up some money for new grill cloth.