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Little Sweetie Forum amplifier project


henry4841
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12 hours ago, Curious_George said:

I like the IEC solution for a few reasons;

  1. If the cord is damaged, you can easily replace it. 
  2. If you move or sell the product and it goes to a different country, you can easily switch cords for said country.
  3. It kinda gives the associated piece of electronic gear that extra level of professional look.

I typically use the IEC inlets that have the fuse holder and appropriately rated power switch built in as well. Everything I build is heavy, it is nice to not have to fight a cord while moving amps around when necessary.

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Hey you other builders, I want to make this thread a group teaching lesson for a beginner to be able to build an amplifier. Let's settle on this design. One reason is Maynard is a long time member of this forum and a friend of mine who talked me into joining this forum a few years back. What do you builders think of this design? It uses a simple SS PS supply and has 2 stages of amplification. I like 2 stage SET amplifiers to build. There are some 1 tube builds but most SET's have a pre stage and a power stage. I like to think a 2 stage sounds better. It is simple with very few parts of which many such as Nelson Pass thinks sounds best. Fewer is better KISS. Uses 200V DC to make power instead of many designs that are 400V's +. Self biasing where a beginner does not have to do any adjustments when finished. No need for them to stick their fingers in a running amplifier. I want others to join in to explain how they go about building an amplifier from a schematic. The days of cheap audio kits with detailed instructions are few these days. A person that may be interested in building a tube amplifier is left trying to do so using a schematic. Let's all of us try and teach how to do it like we are teaching our teenage kid who is interested in electronics and wants to build something. Klipsch speakers and electronics sorta go together. Let's face it we all like electronics. I like to break this schematic into sections. The most complicated schematic is a bunch of different sections joined together. I am using sections instead of the word circuits, KISS. This amplifier has 3 sections. The PS section and two audio sections using two tubes. The critters around the rectifier and the two tubes are there to make the rectifier section and the two tubes work. The PS section which I have already put together has 7 critters. There is a bridge rectifier, I think a bridge rectifier is easier for a beginner to work with, and has 4 pins. the two center pins are for the AC from the transformer to hook to. One of the other pins is marked + and I hooked a + pin of a capacitor to the + pin of the rectifier. Then connected a resistor to the same + pin of the cap. Then another cap + pin to that resistor and this is where one will get the + first to the OPT's transformers then the plate of the power tube 6Y6. The DC coming from the rectifier is not clean enough and these caps and resistor clean the DC up along with the OPT as an inductor where is will be clean enough for the 6Y6 to use. Then I hook another resistor to the 2nd + pin of that cap and the other end of the resistor will go to the + pin of another cap. This is where the power for the 6SJ7 plate will go. The resistor serve two purposes, clean the signal and drop the voltage to what is best for the tubes. The values of the critters are on the schematic. The last critter a resistor will go from the 3rd cap to ground to bleed off the voltage a cap holds even when the amp is turned off. Look at the PS section of the schematic and see if my description makes any sense. All the - pins will joined together and connected to the Star Ground point. My Star Ground is going to be a 2" to 3" piece of 14gauge wire. All grounds of the amplifier will connect there.

 

If another builder can explain it better than I have done you are welcome to join in and tell your way. I want this thread  to be all the builders on this forum putting their heads together and helping a beginner build something. It is my wish now for the other builders to explain in simple terms how the pre tube stage is put together using 8 critters counting the pot making that stage work. Remember KISS when explaining. Where a kid can understand. Help an old man explaining so much and  from typing and take it from here. Taking it in stages makes building much easier and simple. The pre stage, circuit, is only 6 critters that have to be connected correctly. One does not have to know what the critters, parts, do to build this amplifier. They just need to be put in the correct spots. If I have made any errors in describing the PS section please point it out. Let's just have some fun for everyone. 

 

PS: I started this thread but do not consider mine. I want it to be a group project much like the Honey Badger A/B amplifier project at diyaudio.com. Where some of the best minds came together and designed, built, an amplifier that is supposed to sound as good as a 10 grand A/B amplifier. But lets just stick with this simple circuit and make it a beginner build project. 

 

Almost forgot. I am leaving off R1 and C1 from my build. That is Maynard's design he calls the ear bleed circuit. At lest that is what I think he calls it. I do not think I need it but it can be added later if the highs are too bright for your taste. 

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Forgot to mention another reason I like this design. It uses NOS tubes. They are highly valued for their sound quality. Here is a pair of WE 300B tubes for someone with deep pockets I ran across. Someone will purchase them to put in their SET amplifier that probably only makes a few watts. https://www.tubedepot.com/products/nos-western-electric-300b-black-plate-1961-matched-pair  This designs uses probably the cheapest NOS audio tubes you will find. Probably purchased by someone not in the USA. 

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8 minutes ago, Shakeydeal said:

So maybe I missed it and I'm too lazy to read the entire thread again. But who has signed up to have an built? Or are you guys just prototyping right now?

 

 

I just wanted to build another tube amplifier and chose this one for a forum project the reason being I already have one among all the other tube amplifiers I ever wanted when I was younger. Reason for offering to sell after building. Mine is already spoken for when and if it is ever finished. I say when because at my age and health one never knows. Tomorrow is not promised to us. No money will be exchanged until it is finished and ready to ship. 

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1 hour ago, henry4841 said:

Almost forgot. I am leaving off R1 and C1 from my build. That is Maynard's design he calls the ear bleed circuit. At lest that is what I think he calls it. I do not think I need it but it can be added later if the highs are too bright for your taste. 

R1 / C1 form a low-pass filter to approximately 7.2kHz. This is essentially a treble cut circuit if you want to use the Little Sweetie for midrange duty or if you want to contour the high-end to your liking. 

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17 minutes ago, henry4841 said:

Who knows someone with deep pockets may offer a builder on this forum $10,000 to build one with the best parts available. Nothing like joking early in the morning. 

I spent $16,000 for a new roof, but it does not sound quite the same. The rain is now softer sounding.

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Wish one of you smarter guys would make a spreadsheet of the Mouser part #'s for the parts needed for this build. Mouser can be intimidating for someone without electronic knowledge. I have the invoice of what I ordered to get you started. I have found one mistake on my order. I ordered 560ohm 1/2w resistor where I actually needed a 560/3W one. Already noted in the build. I probably did not need to buy many of the parts being I stock quite a bit for repair work and other builds but to get a record of what is needed I tried to make it for a record to pass along.  

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50 minutes ago, henry4841 said:

Wish one of you smarter guys would make a spreadsheet of the Mouser part #'s for the parts needed for this build. Mouser can be intimidating for someone without electronic knowledge. I have the invoice of what I ordered to get you started. I have found one mistake on my order. I ordered 560ohm 1/2w resistor where I actually needed a 560/3W one. Already noted in the build. I probably did not need to buy many of the parts being I stock quite a bit for repair work and other builds but to get a record of what is needed I tried to make it for a record to pass along.  

Maybe not an Excel spreadsheet is desired or required as even a Word program document could suffice. Can always create a PDF for download of a list.

Off the mark here?

 

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22 minutes ago, billybob said:

spreadsheet of the Mouser part #'s

I believe you can create a build sheet within Mouser's web site and export to Excel and post it here.  Its been awhile, but I did something like this for either the Little Darling or the Little Spud. 

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7 minutes ago, The Dude said:

I believe you can create a build sheet within Mouser's web site and export to Excel and post it here.  Its been awhile, but I did something like this for either the Little Darling or the Little Spud. 

Had forgotten about those 2

builds. 

That could make things more convenient. Thanks!

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1 hour ago, Islander said:

 

Shingles, shakes, or steel?

Shingles. I would like to have bought a steel/metal roof, but the price was a lot more than I was willing to spend. Plus, I had to save some money for my future in ground pool. 

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A little progress made this morning. When drilling in aluminum I always have to do some clean up work on the other side. A cheap small grinder from Harbor Freight makes quick work of the ones you can get to. Drilled some more holes as well for ventilation.  

P1030986.JPG

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More work done this morning. The switch is not tightened down, reason for crooked. You have to be able to turn it to fasten wires. Will install the transformers in the morning and possible start wiring it up some. All for today. I do not want to make it work. Just fun guys, do not want a job. 

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44 minutes ago, henry4841 said:

A little progress made this morning. When drilling in aluminum I always have to do some clean up work on the other side. A cheap small grinder from Harbor Freight makes quick work of the ones you can get to. Drilled some more holes as well for ventilation.  

P1030986.JPG

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This tool works great for deburring these holes. https://www.amazon.com/gp/product/B001O5YSXU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

51c7IV3j1-L._SL1500_.jpg

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If one can manage to flip the chassis over, you can use the stepped bit to de-burr the bottom side of the diameters drilled. Make sure the piece being drilled is strapped down to something, as the stepped bit can be rather aggressive. 

 

It's a bit more spendy, but I like using stainless screws.

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