Past Tense of -ar, -er, -ir verbs:

Past tense of -ar verbs follow a different pattern than past tense of -er/-ir verbs, which follow the same pattern., -er, -ir verbs follow the same pattern.

Past Tense of -ar verbs:

General transformation remains almost same as present tense.

Lesson 31: https://www.youtube.com/watch?v=ZwTPwRMjLD8

 

 base word = -ar (to do something) singular plural ( add s at end)
 I => First person -é (with accent)

-amos (same as present tense, figured from context)

You (informal) => Second person

-aste (te added compared to present tense)

-asteis (-is added to singular form instead of áis)

He, she, You (formal=> Third person

-ó (with accent. -o w/o an accent was the present tense for Singular First person)

 

-aron

 

Hablar => to speak

 base word = hablar (to speak) singular plural ( add s at end)
 I => First person

hablé

ex: Yo hablé => I spoke

hablamos (Same as present tense, figured out from context)

ex: nostros hablamos => We spoke

You (informal) => Second person

hablaste

ex: tú hablaste =>you spoke

hablasteis

ex: vosotros hablasteis

He, she, You (formal) => Third person

habló

ex: Ella habló => She spoke

 

hablaron

ex: Ellos hablaron => They spoke

 

Gustar => to speak

 base word = gustar (to speak) singular plural ( add s at end)
 I => First person

gusté

ex: te gusté me => you liked me

gustamos

ex: te gustamos => you liked us (same as you like us)

You (informal) => Second person

gustaste

ex: le gustaste te=> he liked you

gustasteis

ex:  ex: He liked you all => le (to him) gustasteis

He, she, You (formal) => Third person

gustó

ex: I liked the car => Me gustó el coche (here car is 3rd person, so gustó used)

gustaron

ex:I liked peoples => Me gustaron los pueblos

 

 

Past Tense of -er/-ir verbs:

General transformation for past tense remains almost same as present tense.

Link: https://www.youtube.com/watch?v=P1i5BrPAELU&list=PLv63dFTP4Sjq6knRsZQI-bTnRE38cZZoy&index=26

Link (lesson 35) => https://www.youtube.com/watch?v=oCT68wkVCNM

 

 base word = -er/-ir singular plural
 I => First person

-imos

You (informal) => Second person

-iste

-isteis

He, she, You (formal=> Third person

-ió

 

-ieron

 

Comer => To eat. Past tense is "ate".

 base word = comer (to eat) singular plural ( add s at end)
 I => First person

comí

ex: Yo comí manzana=> I ate apple

comimos

ex: nosotros comemos (we eat)

You (informal) => Second person

comiste

ex:

comisteis

ex: vosotros comisteis

He, she, You (formal=> Third person

comió

ex: Ella comió => She ate

 

comieron

ex: Ellos comieron

 

Haber => had. Past tense of has is had. It's used as an auxilary verb. Haber is an irregular form, and so doesn't follow regular -er table. For transformation purposes, base stem is "habí" (i with an accent), and the verb itself follow ar verb Present tense table (instead of Past tense -er table).Actually Haber changes to Habíar, and hence is an -ar verb. The only odd entry is 1st person singular which has -a instead of -o.

 base word = haber => Habíar (had) singular plural ( add s at end)
 I => First person

había (instead of -o, it ends in -a, so it becomes same as 3rd person singular)

habíamos

You (informal) => Second person

habías

habíaís

He, she, You (formal) => Third person

había

 

habían

 

Escribir => To write. Past tense is 'wrote".

 base word = escribir (to write) singular plural ( add s at end)
 I => First person

escribí

ex: Yo escribí => I wrote

escribimos

ex: nosotros escribimos (we write)

You (informal) => Second person

escribiste

ex: tú escribiste

escribisteis

ex: vosotros escribísteis

He, she, You (formal=> Third person

excribió

ex: Ella escribió => She wrote

 

escribieron

ex: Ellos escriben

 

 


 

 

-ir verbs: A lot of words ending in -ir are verbs and are called -ir verbs. ex: escribir => to write, etc. This is different than "ir" standalone verb that we saw above.The base word literally means "to eat". The transformation is same as "-er" verb, except for nosostros and vosotros. Here "emos" becomes "-imos" and "-éis" becomes "-ís".

Link: Same video fo -er verb above has -ir verb explanation.

 

 base word = -ir (to do something) singular plural ( add s at end)
 I => First person -o (same as -er)

-imos (instead of -emos)

You (informal) => Second person

-es (same as -er)

-ís (instead of -éis)

He, she, You (formal=> Third person

-e (same as -er)

-en (same as -er)

 

Ex: Below are few examples of -ir verbs that follow the pattern above.

escribir => To Write: The Spanish verb escribir is an -ir verb translated in English as “to write”. It looms similar to word "scribe" in English which referred to a person employed to make written copies of documents. Basically writing things by hand. Below is the table based on above transformation.

 

 base word = escribir (to write) singular plural ( add s at end)
 I => First person

escribo

ex: Yo escribo => I write

escribimos

ex: nosotros escribimos (we write)

You (informal) => Second person

escribes

ex: ¿tú escribes espanol? => Do you write spanish? => We usually omit " tú", so more common is ¿escribes espanol?

escribís

ex: vosotros escribís

He, she, You (formal) => Third person

excribe

ex: Ella escribe => She writes

 

escriben

ex: Ellos escriben

More words:

  • abrir => to open, Opposite word is cerrar => to close. Adj form is: abierto(s)/abierta(s). ex: The door is open => la puerta está abierta
  • aburrir => to bore. This word is very commonly used in past tense, or in gerund (-ing) form with both forms adding -ida/ido as conjugation. You may think of word "bored", "boring" as an adjective too, so aburrido/aburrida used aa an adjective.
    • ex: The movie is boring => la peculia es aburrida (used an as adjective, i.e movie is nice, movie is bad, etc)
    • ex; I'm bored => estoy aburrida/aburrido. Used in past participle form (i.e I had been bored, or I was bored, already happened), or you can also think of bored as an adjective (i.e I'm happy, I'm sad, etc).
  • cambiar => To change or to exchange something. ex: I want to change my hair color => yo quiero cambiar el color de mi pelo (change color of my hair)
  • coincidir => to agree (remember as to coincide or come together), diferir => to differ or disagree.
  • decidir => To decide
  • dormir => to sleep. It's similar to "dormant" so implies being dormant or sleepy. Opposite word is despertar => to wake
  • mentir => to lie.
  • ocurrir => To occur
  • recibir => To receive. Opposite of this is enviar => to send
  • repetir => to repeat. From English word, repeat.
  • sentir => to feel. Similar to Sentiment or feelings. Sentir is also used to mean "to feel or to be sorry", i.e sentimos => We are sorry for ..
  • seguir => to follow (like to follow signs, follow someone). It's mentioned on many road onstruction sign boards.
  • permitir => to allow. From English word, permit.
  • vivir => to live. Opposite word is "morir" which means "to die". morit sounds like morbid, which means dead. Noun derived from vivir is "vida" => Life. Viva is a 3rd person imperative verb, meaning live (see in imperative verb section)

 

The personal "a" (pronouned "aa"):

In short, personal "a" is used after the verb, if the verb is being done to a person. More details on this in video above (for "-er" verb).

ex: I see Maria => Yo veo a Maria. "ver" is an -er verb which means "to see". So, for "I see", it should have been "yo vo", but it's that "irregular verb", which translates to "veo". Reason might be that "vo" is too short of a word, so "veo" was kept.

 

 


 

 

-er verbs: A lot of words ending in -er are verbs and are called -er verbs. ex: comer => to eat, etc. The base word literally means "to eat". The transformation is same as "-ar" verb, except that instead of "a" in transformation, we use "e".

Present Tense:

Link: https://www.youtube.com/watch?v=P1i5BrPAELU&list=PLv63dFTP4Sjq6knRsZQI-bTnRE38cZZoy&index=26

 

 base word = -er (to do something) singular plural ( add s at end)
 I => First person -o

-emos

You (informal) => Second person

-es

-éis

He, she, You (formal=> Third person

-e

 

-en

 

Ex: Below are few examples of -er verbs that follow the pattern above.

Comer => To Eat: The Spanish verb comer is an -er verb translated in English as “to eat”. The noun "comida" meaning "food" is derived from this. Below is the table based on above transformation.

 

 base word = comer (to eat) singular plural ( add s at end)
 I => First person

como (como also means to like)

ex: Yo como manzana => I eat banana

comemos

ex: nosotros comemos (we eat)

You (informal) => Second person

comes

ex: ¿tú comes carne? => Do you eat meat (carne is similar to carnivore)? => We usually omit " tú", so more common is ¿comes carne?

coméis

ex: vosotros coméis

He, she, You (formal=> Third person

come

ex: Ella come => She eats

 

comen

ex: Ellos comen

 

Desire, Ability and Obligation verbs: All 3 are -er verbs and are one of the most used words in talks. They are discussed under irregular verbs

  • tener => have: to have or have to. Under irregular verbs. 
  • querer (kay-rer) => want:  Under irregular verbs.
  • poder => can  Under irregular verbs.

 

  • hacer => to do/to make : Under irregular verbs.
  • haber => has/have :This is discussed under participle form of verb.

 

Other -er verbs:

  • aprender => to learn. ex: we learn spanish =>  nosotros aprendemos español => we may leave "nosotros" as is common, so just "aprendemos español"
  • comprender => To comprehend or understand. Another verb "entender" is synonym to this.
    • Ex: No comprendo => I don't understand. (1st person as -o)
    • Ex: ¿Comprendes? => Do you understand?¿ (You is left out as is common, -es implies 2nd person)
    • Ex: I don't understand everything you say => yo no entiendo todo lo que tú dices. (entender stem is "entiend")
  • creer (CRE-ER) => To think or believe. Another similar word crecer, means "to grow".
    • We believe in God => Creemos en dios (el dios => the god, la disoa => the goddess)
    • I grew up in India => yo crecÍ en India
  • prender => to switch on
  • barrer => to sweep. ex: ¿Quién barre? => who sweeps?
  • nacer => to born. ex: I was born in India => yo nacÍ en India
  • romper => to break something. Adjective "roto" means broken.
  • vender = to sell (comprar=> to buy). vendedor => salesperson (vende is to sell, so related to sales)

 


 

Audio Bus interface

This section talks about communication i/f to xfer audio data. The audio genrating source are microphones, while speakers deliver that audio. In the past, microphones and speakers used to be analog sensing device, and their chip output was analog signal. However, analog signals being iprone to interference on PCB are never a preferred solution. So, now these microhones/speakers have a lot of analog logic on these chips itself, along with digital circuitry that can drive out these audio signals in digital binary format(string of 1's and 0's).

There are many different standards for transmitting digital audio data from one place to another. Some formats, such as I2S, TDM, and PDM are typically used for inter-IC communication on the same PC board. Others, such as S/PDIF and Ethernet AVB are primarily used for data connections from one PCB to another through cabling.

Audio BandWidth: Typical Audio data is sampled at 8KHz to 192KHz. It has 8bit to 32 bit resolution. For 8Khz and 8 bit resolution, we need 8k*8=64kHz bus frequency, or as high as 192k*32=6Mhz. As such, a lot of these interfaces don't need to run faster than few MHz.

Techincal doc by Analog Devices about I2C, TDM and PDM => https://www.analog.com/media/en/technical-documentation/technical-articles/MS-2275.pdf

I2S:

I2S is called Inter IC sound, and is the most common  digital audio format used for audio data transfer between ICs. The I2S standard was introduced by Philips Semiconductors (now NXP) in 1986 and was revised in 1996

Philips was bought NXP, and so bty he spec is mainatined y them here: https://www.nxp.com/docs/en/user-manual/UM11732.pdf

The attached diagram shows the waveform/connections.

FIXME ATTACH DIAGRAM --

 

I2S devices can either be in Master or slave mode. Master always drives Clock and Channel Select. Data can be driven either by Master or slave. There are 3 wires for I2S:

  1. Clock => SCK (serial Clk) or BCLK (Bit clk). Master drives SCK.
  2. Channel Select => WS (Word select) or LRCK (Left Right clk) or FS (Frame Sync). I2S can carry 1 or 2 channels of data. That channel is selected via this line, and it also serves to synchronize the frame (i.e it indicates start/end of current frame). 0= Left channel, 1=Right channel. It's better to think of WS as "Frame sync", as when you have > 2 channels, then WS will be a pulse, and in that case, it will indicate start of new frame. Master drives WS.
  3. Data => SD (serial Data) or SDATA, SDIN, SDOUT. Either Master or slave may drive SD. However, SD is unidirectional - either master or slave drives it, but has to be configured beforehand as an i/p or o/p.

Apart from 3 wires, it may have variations where following lines are added. These signals are not part of spec, but added by certain companies for their product (and commonly supported).

  1. Master clock => MCK (typically 256 x LRCLK) = commonly included for synchronizing the internal operation of the analog/digital converters. Master drives MCK along with WS.
  2. Multiplexed data line for upload => Having dedicated SDAT lines for i/p and o/p. So, instead of 1 SD pin, we have 2 separate data pins with fixed direction => SDIN and SDOUT.

 

TDM:

When we talk about I2S, we are usually talking about legacy mode I2S as explained above. I2S can also operate in a Time Division Multiplexing (TDM) mode. We use this when we want to xfer more than 2 channels of data. That is not supported by legacy I2S. We can have multiple data i/p or o/p pin with 1 set of SCK and WS (might need multiple WS?). This will solve our problem of transmitting multiple channels. But that will increase the number of pins in system. Instead we want to use single data line for transferring audio signals from all channels. This is where TDM spec comes in. There is no standard for TDM interfaces, so ICs have their own slightly-different flavor of a TDM implementation. Since TDM has no spec, a common implementation includes all 5 signals used in I2C above: BCLK, LRCK, SDIN, SDOUT and optional MCK.

A TDM data stream can carry as many as sixteen channels of data and has a data/clock configuration similar to that of I2S. Each channel of data uses a slot on the data bus that is 1/Nth the width of the frame, where N is the number of channels being transferred. A TDM frame clock is often implemented as a single bit-wide pulse (rather than I2S’s alternating High and low for left and right channels). So, at start of WS pulse, we send fixed width of data for all N channels one after the other (called a frame), and then start of next WS pulse, we send next bits of data for all N channels and so on. Thus we avoid having multiple Data Lines. Clock rates are higher here at multi MHz (although < 25MHz) as multiple channels are supported on a single data line, so higher BW needed.


TDM is commonly used for a system with multiple sources feeding one input, or one source driving multiple devices. In the former case, each TDM source shares a common data bus. The source must be configured to drive the bus only during its appropriate channel, and tri-state its driver while the other devices are driving the other channels.

 

PDM:

PDM is another variation of I2S, where 2 channels are supported by using only 2 wires => Clk and Data. 2 PDM sources drive a common Data Out (DOUT) line which feeds into the PDM receiver's DIN line. A clock generated by the system master can be used by two slave devices, which use alternate edges of the clock to output their data on a common signal line.

PDM basics:PDM is Pulse Density Modulation. Here Audio data amplitude is represented via only 1 data line, by modulating the density of 1's and 0's to indicate higher or lower amplitude. When more 1's aretransmitted, then it's indicating a higher amplitude, and when more 0's are transmitted, it's indicating a low amplitude.

https://users.ece.utexas.edu/~bevans/courses/rtdsp/lectures/10_Data_Conversion/AP_Understanding_PDM_Digital_Audio.pdf

A PDM-based architecture differs from I2S and TDM in that the decimation filter is in the receiving IC, rather than the transmitting IC. The output of the source is the raw high sample rate modulated data, such as the output of a Sigma-Delta modulator, rather than a decimated data, as it is in I2S.

 


 

MEMS Microphone:

MEMS (Micro-Electro-Mechanical Systems) microphones come in a package (just like other chips). There may be analog or digital MEMS microphone. Analog ones produce an output voltage that is proportional to the instantaneous air pressure level. They have just 3 pins => VDD, Gnd and Output Voltage pin. This output pin is connected to a microcontroller on a PCB, which processes this analog o/p and produces bits. AIn a digital microphone, the whole circuitry to process the analog o/p and produce digital bitstream is put in a single package. So, it's lot better performance in terms of noise immunity.

Basic intro: https://www.edn.com/basic-principles-of-mems-microphones/

Digital Microphone Teardown: https://www.signalessence.com/blog/mems-microphone-teardown

There are 2 separate dies inside a digital mems microphone:

  1. Microphone die: This die has the microphone accoustic sensor. This is made using same semiconductor production lines that is used for making transistors. Layers of different materials are deposited on top of a silicon wafer and the unwanted material is then etched away, creating a moveable membrane and a fixed backplate over a cavity in the base wafer.  The sensor backplate is a stiff perforated structure that allows air to move easily through it, while the membrane is a thin solid structure that flexes in response to the change in air pressure caused by sound waves. MEMS microphones need to have a hole in their package to allow sound to reach the acoustic sensor. 
  2. ASIC die: This die is a digital/analog ckt that has a charge pump to place a fixed charge on the microphone membrane.  The ASIC then measures the voltage variations caused when the capacitance between the membrane and the fixed backplate changes due to the motion of the membrane in response to sound waves.  An ADC inside the ASIC converts the voltage variations into digital format for processing and/or transmission. Finally o/p is sent out in digital format using I2S, TDM, PDM. PDM data is captured by separate microcontroller/processor, which then decides what to do with it. Typically it converts PDM into PCM via dedicated hardware filters or in software and then it finally plays on speakers.

 

The microphone accoustic sensor itself is on silicon wafer, fabricated on semiconductor production lines using highly automated processes. Layers of different materials are deposited on top of a silicon wafer and the unwanted material is then etched away, creating a moveable membrane and a fixed backplate over a cavity in the base wafer.  The sensor backplate is a stiff perforated structure that allows air to move easily through it, while the membrane is a thin solid structure that flexes in response to the change in air pressure caused by sound waves.  

Precious Metals - Gold, silver:

I'm not a big fan of buying gold/silver, etc for investment purpose. Nor buying it for showoff.

History:

Good article on historical gold and silver statistics is here .

Gold vs paper currency

Before Gold came into existence as currency, people used barter system to sell/buy things. This involved exchanging items with each other. Since this was very inefficient process, gold came into the process as a medium of currency. Gold mining has been taking place from about 5000 B.C. , so it has been about 7000 years, since gold has been used in some form as a currency or asset.

Gold has been used as a currency, since it's very easy to store, can't be produced artificially  and also limited in quantity. It's 20 times heavier than water, so 1 litre cube of gold = 10cmx10cmx10cm weighs 20kg, as compared to water of 1kg. So, at today's price of $2K/ounce, that 1 litre cube of gold would cost about $1M. Since it's limited in quantity and only exists in mines, no one can produce it artificially. Any thing that could be produced artificially by man, could not be used as currency. As such, gold was used as currency, and people had confidence that only so much gold was available.

Somewhere down the line, paper currency came into existence. Governments said that they will issue paper currency, which would be as good as gold. However, no one would believe in paper currency, as it was just a piece of paper. So, in order to make it work, it was backed by gold. That meant that the government would only issue paper currency in exchange for gold. So, let's say there was 1000 gram of gold in that country that was in circulation, then the govt would issue 1000 papers (assuming 1 paper was assigned value equal to 1 gram of gold). These 1000 papers would be held by the govt in treasury, and wouldn't be given to anyone. Now, whenever someone came with 1 gram of gold, govt would give him 1 piece of paper. That meant that the total amount of currency in circulation was still the same (999 gram of gold and 1 paper currency). Similarly, if more people came to exchange their gold with paper currency, govt would get more and more gold in exchange for these papers. After there is sufficient confidence in the system, most of the money in circulation would be paper currency, with an equivalent amount of gold sitting in the government treasury.  That gave confidence to paper currency, as it was conceptually equivalent to gold, but instead of carrying gold around, you could exchange this gold for paper currency from the issuer of paper currency, and then carry paper currency around, which was much easier. At any given point of time, if you wanted to get your gold back, you could take your paper currency to the govt and get an equivalent amount of gold.

There is no clear statistic on total amount of gold mined since the advent of civilization. According to the link at top, total amount of gold ever mined is 5.5B ounces or 165K metric tonnes (1 metric ton is 1000 kg). About 10% of the gold ever mined has been lost, used or unaccounted, so there's about 5B ounces or 150K ton of gold in circulation today. This article suggests that total amount of gold that is mined every year since 1995 is about 80M ounces or 2500 Metric tonnes.  World gold production peaked at 2.6K ton in the year 2001, and has been declining since then. In the year 2010, it was at 2.4K ton. Assuming $2K/ounce of gold price, that's $150B of gold that is mined every year. More than 50% of the gold ever mined has been mined in the last 50 years, and 90% of the gold ever mined has been mined since 1850. So, Gold supply is increasing by about 2% every year on an average. The aggregate un-mined known reserves of all the world's gold mining companies is approximately 45K tonnes as mentioned here . So, at current pace, somewhere around 2030, all of the known gold reserves will be exhausted, and then gold supply will increase very slowly.

Of this 150K ton of gold that has been mined, 50% is consumed in jewelery by mixing gold with other metals as copper, etc which results in 22k, 18k, 14k or 10k purity gold as pure 24k gold is too soft to be used in making any jewelery. 40% of gold is consumed as investment in gold coins, bars, govt reserves, etc and remaining 10% is consumed in industry for making solders, IC connections, medical uses, etc.

Indian households hold about 18K ton of gold, which is about 12% of all the gold in the world ever mined. Most of it is held in form of jewelery. Some estimates, put the amount of gold owned by Indian households to be 25K to 30K ton, which would be about 20% of all gold.

Governments hold gold in their reserves too, as bank's reserve assets. About 30K ton or 20% of gold is held by various governments. As of 2010 end, US Fed has the largest gold reserve at 8K ton (5%), Germany 3.5K ton, Italy and France 2.5K ton each, China and Switzerland at 1K ton each, Russia, Japan, Netherlands and India each at more than 0.6K ton of gold. IMF (International Monetary fund) holds about 3K ton, while ECB (European Central bank) holds about 0.5K ton of gold.

Gold is also held privately in stocks/funds . These funds actually buy physical gold on your behalf, when you buy such stocks. As of 2011, 2.5K ton or 2% of gold is held in such funds. The most widely traded such exchange traded fund is SPDR gold ETF (ticker GLD), traded in US stock market. It has about 1.2K ton of gold held in its stocks.

Aside from 40% of gold accounted above, 10% of the gold is in industrial materials. So, the remaining 50% of the gold ever mined is in various countries as household jewelery, gold coins, bars, etc (excluding indian households).

Gold producing countries:

The world’s top five gold producing countries mine about 50% of gold of the total mined output of 2.4K ton. Countries producing about 2/3rd of total gold production in world are as follows: China - 370 ton (15%), South Africa- 275 ton (11%), Australia - 250 ton (10%), USA - 250 ton (10%), Peru - 210 ton (9%), Russia - 160 ton (7%), Canada - 105 ton (5%). By comparison, India produces only about 2.5 ton or 0.1% of total gold produced every year. South Africa was the largest producer of gold for many decades, producing over 800 tons every year, but all easy pickings have been done, resulting in precipitous decline of new and existing gold mines. So, it's getting more difficult and expensive to mine new gold. While gold mining cost were around $200/ounce at start of 2000, they are now over $700/ounce and going higher each year. This ABN AMRO paper has good statistics on gold mining costs. Still at prices over $2K/ounce, it's still profitable business.

Gold consuming countries:

In 2011, there was demand for about 4K ton of gold. Gold is not consumed in the true sense. 2K ton (50%) was consumed in jewelery, 1.6K ton (40%) in investment (1.4K ton in bars/coin, while 0.2K ton inETFs), and remaining 0.4K ton (10%) in industrial applications. Note that before the bull run of gold (year 2003 and before), about 80% of gold demand was for jewelery, 10% for investment and 10% for industrial applications. So, the rising price of gold has generated a lot of demand for gold as an investment. Since annual production of gold is about 2.4K, while demand is 4K, the shortfall is made up by recycling scrap gold, as well as by sale of gold by Banks around the world. The world’s largest consumer of gold is India, at 800 ton (20%), then China at 500 ton (12%), and a distant third is USA at 125 ton (3%). Rest all countries consume less than 100 ton, and consume roughly in line with what they produce. Gold demand has fallen significantly for all countries except India and China, since 2003 as prices for gold went up by a factor of 5. India's gold import was 1K ton in 2011, a record high.

 


 

Buying/Selling Precious Metals = Gold, Silver, Platinum, Palladium:

Gold/Silver coins are the best way to buy these precious metal, as they may be gifted to others. Platinum and Palladium and two other metals, that are considered alternative to gold, and are highly traded. However, we'll be looking at gold/silver only. There are few terms that we need to know before rushing to buy these.

  • Weight (in troy oz): The most common weight for these coins is 1troy oz (31.1g). NOTE: it's NOT 1 oz, as 1 oz is only 28.3g. We quote Gold/Silver in troy oz in USA and in international markets. Coins may be more than 1 troy oz in weight, as they have to be mixed with other metals to make them more durable. Many reputed mint companies will guarantee that gold/silver content itself is 1 troy oz. Most commonly seen with gold coins, where the weight of gold coin is 5-10% more than 1 troy oz, to give you 1 troy oz of gold.
  • Spot Price: Spot price is the price at which gold/silver is sold in huge commodity markets. Usually you have to pay a premium over the spot price to buy these from online merchants, as they have shipping costs, credit card costs, insurance cost, etc. No one can sell you physical gold/silver etc for spot price, as they will lose money doing that.
    • 2023: As of 2023, spot price for 1 troy oz of metals is: Gold = $2K,silver = $20, Platinum and Palladium = $1k. Coins for 1 oz sell for 2%-5%
  • Purity: Gold/Silver also have a purity noted on them, which specifies how much of the weight is pure gold/silver. Generally, these coins are mixed with other metals to make them more mintable. It's common to see gold/silver coins mixed with other metals. In India most coins are sold at 92% purity (i.e only 92% of the weight of the coin/bar is precious metal, the other 10% is less precious metal as Silver,Copper, etc). But they are priced as if it's 100% gold/silver. Gold/Silver purity is noted in karats. karats indicate the proportion of precious metal out of a total of 24 karats. 24 karats is 100% pure gold, So, a 22 Karat gold is 22/24=91.67% gold content. Most places sell gold at 18 karat or 22 karat purity. Here in US, all sorts of coins are sold with different purity levels. Purity is also noted in "spine". Four nines (99.99% or 0.9999) is called four spine. Three nines (99.9% or 0.999) is called three spine. A lot of coins that are minted by individual companies are 3 spine, that's 99.90%. Typically four spine is a little more valuable because there is more gold. Chinese gold pandas are 3 spine, for example. Us liberties or Buffalos are 4 spine.
  • Minting Companies: Companies may mint their own coins, and sell them. These don't have that lure, as you these are NOT considered currency. US Mint ( branch of Treasury Dept of US govt) has the authority to mint coins and sell gold, silver, Platinum and Palladium coins in different sizes. It doesn't directly sell to general public, via sells them via it's authorized sellers. These US Mint Coins are highly sought after, as they are internationally recognized as being of highest purity, backed by US govt and have legal tender value just like US currency (i.e 1 Dollar Gold coin has $50 written on it, meaning US govt will pay you $50 if you decide to use it as a legal tender. No one does it, since market price of that coins is lot higher at $2000) and may be included in Retirement (i.e. IRA) accounts too.
    • Link to US Mint coins: https://en.wikipedia.org/wiki/Coins_of_the_United_States_dollar => For Gold/Silver coins, the gold reference is "American Eagle" coins. They have guaranteed 1 oz of gold/silver with 3 or 4 spine purity. However, they carry premium over spot price.
      • American Gold Eagle (AGE): These are the only gold coins that you should buy as they may usually be bought with only 2% premium over spot price of gold. One thing to note is that these coins have low purity of 91.67% (22/24*100) as it's 22 carat gold. It has 3% Silver and 5.67% copper. However, it still contains 1 troy oz of gold, as the total weight of coin is 1.091 Troy oz, with 1 troy oz of that being gold. It's very durable, but less shiny than other coins which are 99.9% pure gold.
      • American Buffalo (AB): These were first minted in 2006, and are the only 24 karat gold coins with 99.99% purity offered by US Mint. These were offered to compete with pure gold coins offered by Canadian and Australian Mintage. Since these have no other metal content, their weight is 1 troy oz. They are more delicate and easy to chip, or get their gold brushed off.So, they have to be kept in a box or package.
      • American Silver Eagle (ASE): ASE are composed of 99.9% silver and 0.1% copper. These coins usually sell for $3-$4 over spot price of silver. You may buy other Silver coins (NOT ASE) by other minters which may be only $1-$2 premium over spot price. But expect to pay at least 5% over spot price, which makes it lot more difficult to make as much profit when selling (compared to gold).
    • Other Govt Mint coins: Government of many countries around the world also mint gold/silver coins. Some of the popular ones are Canadian Gold Maple Leaf (GML) coins with 99.99% purity, South African Krugerrand Gold coins of 22 Karat (Same as AGE with total weight being 1.09 oz), Australian Kangaroo coins produced by Australian Mint and Britannia coins produced by British Royal Mint. They are all guaranteed by the respective Governments, so are equally safe.
    • I would personally prefer to only buy AGE, and not bother with any other gold coins. They are very liquid, and easy to buy/sell. For Silver coins, since the premium for ASE is 20% over the spot price, I would prefer to buy it local minting companies, which sell it to you for 5%-10% over the spot price. You easily lose 2%-3% in gold and 5%-10% in silver each time you buy/sell compared to spot price. As for my recommendation, you should never ever sell anything you buy. So, just buy and keep it forever !!

Below are few merchants where you may buy these. 

EBAY: I used to buy them on ebay before 2014, as at that time they allowed you to buy gold/silver using ebay GC, which you could regularly get on discount for 5%-20%. So, that was a pretty good deal (easy 5%-20% profit). Since 2014, they stopped accepting GC for buying any precious metals. Now, there's no reason to buy on ebay. Actually you should avoid buying on ebay, as ebay has gone downhill, and still going that path. Lots of other retailers offer much better service at the same price.

COSTCO/WALMART: As of 2023, 2 biggest retailers - Walmart and Costco have started offering Gold/silver coins. Costco usually have gold coins on sale from time to time with only $30-$40 over the spot price of Gold. Silver coins go less on sale. However, their American Eagle silver coins usually sell for only $2 over spot price per coin, which is a decent markup (Not a bad deal, as other retialers usually have > $2 markup on these coins). Walmart has gold/silver coins via 3rd part sellers. One of the most reputed 3rd party sellers is "APMEX", but you may buy from any 3rd party sellers, as Walmart stands behind the product. Whenever I've Walmart GC to burn, I usually end up buying these gold/silver coins.

Shipping is always free, item is non returnable, and you can pay with credit card, and earn points (1%-2%). 

 


 

 

DEALS:

 

Costco:

 

Walmart: