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Little Sweetie Forum amplifier project


henry4841
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There are many on this site more educated, smarter and more talented than myself that I like to ask questions to learn more. I am just an old man that lives by himself with his dog that likes playing with electronics. It all started in my 20's when there were many electronic kits you could buy and assemble yourself. I once built a B&W television from a kit and it worked! Surprised me. At least it worked on VHF. My normal day is waking early with decafe and oatmeal then a walk around the neighborhood with my GF who lives down the street. Then if I feel like it and have no chores to do around the house to spend a few hours in the morning working on some electronic project of mine. Then lunch, nap and later listening to music or watching TV if I can find something that makes me happy. This is how I spend my retirement. Life is good. 

 

I started this thread for those that may have an interest themselves in the process of building a nice sounding amplifier at a low a cost as possible using good parts. It is not cheap being that good iron is expensive these days. Maynard designed this amplifier and him and I like the sound it makes. One will hear what Maynard and I like if they decide to build this amplifier. When you buy any good audio product whether electronics or speakers you are going to hear what a designer or team of designers have got together and decided this is what sounds good to them. At least you hope that is what is done and not something just thrown together for a price point to sell. It is really that simple. This design of Maynard's sounds as good as anything I have built in tone, vocals and soundstage. It makes decent bass for most but for those that like strong low bass put a dedicated piece of audio gear that makes good bass called a sub and you will have a system as good as I have heard lacking nothing. That is those that like the SET tube sound. No perfect pair of speakers or amplifier for everyone. I like it. Maybe it is that it uses a pair of NOS power tubes. Tubes made in that day were made by the giants of the electronic industry. The new production tubes are made by small companies for a limited market. Not like the era when tubes ruled.

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10 minutes ago, henry4841 said:

Got a little more done this morning. The drudgery part of a tube amplifier build, drilling holes. Will clean it up and start again Monday. At least that is my plan. 

 

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I love cutting & filing the hole for the IEC power socket... NOT. However, it looks great when it is done. 

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10 minutes ago, Curious_George said:

I love cutting & filing the hole for the IEC power socket... NOT. However, it looks great when it is done. 

I do not think I have ever cut the IEC hole to my satisfaction. The worse part of making holes for me. This is probably the best one I have done. Just drilled a big hole and used a jig saw. When the IEC connector is installed in this hole it is going to look the best I have ever done. Covers all the rough looking edges. All the other holes are done with standard bits and step bits. Sometime referred to Christmas tree bits. 

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4 minutes ago, henry4841 said:

I do not think I have ever cut the IEC hole to my satisfaction. The worse part of making holes for me. This is probably the best one I have done. Just drilled a big hole and used a jig saw. When the IEC connector is installed in this hole it is going to look the best I have ever done. Covers all the rough looking edges. All the other holes are done with standard bits and step bits. Sometime referred to Christmas tree bits. 

I'm a bit more anal, I cut it small then file it to the shape of the IEC socket. Just me. 

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I'm sorry but some of the young guys on this site might.

 

I do plan on detailing how I go about building an amplifier though. Try to be step by step. May not be the correct way but my way. I like to keep it simple. Anyone on this site that can do handyman chores around the house or do some repairs on their car should be able to build an amplifier such as this simple one just from the schematic. I can point to the parts I used and where to buy them and I am thinking of making a parts list at Mouser where all one has to do is buy what is on the list to get the correct part to make this amplifier. I have done it before for some young guys on some other audio projects. Maynard has a list on his schematic on the parts needed. I just need to add Mouser's part number. The Chassis came from Amazon and the tubes and special tube parts came from Tubedepot. I hope more of these little gems are built. One can stick their chest out and tell their friends "I built that." No real electronic experience is needed. Just the basics skills anyone with common sense can learn. My reason for doing this is other sites have had members doing this very thing which I enjoyed following along. Just want to pass it along here. Having fun with something to do is my reason. 

 

Let's all get along on this thread and have some fun and possible learning something from an old man.  

 

PS:  Almost forgot. One way to get around that IEC cutting out is to do what Maynard just told me he does. From his pen:   I get around the IEC socket dilemma by using a hard wired cord and strain relief.

 

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Mike Stehr does great builds. I admire the work he does. Glad to see him join in the fun. 

 

Just a reminder, let's be friends and get along on this thread. This site is not a diy one so I am want to keep this thread here in the Garage section where the people in charge of this forum may let this thread continue. I am going to use the KISS system when describing this build as best I can. Keep it simple stupid for those that do not know what the KISS system is. A lot of companies have the KISS sign in their engineer room for their designers and engineers to remember. I like simple. One reason I like this design. Simple, works and sounds as good in the midrange and highs as anything I have buiilt. And easy to build point to point. I like simple when it comes to diy electronic projects. More complicated circuits need a pcb board made for the components to make them practical. I have been watching a teacher of electronics at a college and one the first points he makes is what he is teaching is another language. The language of electronics. If I use a word you do not understand you can google it for more in formation. For example I may say star ground. Google amplifier star ground and you will find the info for what it is. It is the one place that all the grounds of the amplifier are attached. This will prevent ground loops that cause noise. This is the best time I have seen for someone to learn and enjoy electronics. When there is so much info online and youtube videos to watch and learn. When I first started playing with electronics it was much harder to learn. One pretty much had to take a at home course or find and read books on electronics. I am self taught so if I can do it you can too if you have the desire. 

 

When I make a mistake on this thread, I make mistakes, plenty of them, please use a constructive way to point it out. Let's try and keep it positive.

 

This is Maynard's amplifier, not mine. I just built it. I have never designed a circuit of any kind. I have an idea of how to do it but no desire to do so. I leave that up to the young minds that like that sort of thing. I am a long time member of the diyaudio.com site. But the guys there can get way over my head when discussing circuits. It is all I can do to know what long tail pair and constant current sources are. Very talented individuals there. My dog woke me up early this morning having to go outside so I am doing some rambling early this morning. 

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This is the bud box I am using to build this project. https://www.amazon.com/dp/B005T58XIC?psc=1&ref=ppx_yo2ov_dt_b_product_details  A good one and as cheap as I have found. The theme of this build. Good parts at the best price.

 

The power transformer I am using is this one. https://www.antekinc.com/as-1t200-100va-200v-transformer/   I like toroidal power transformers and this one is shielded to boot. Always a plus. Again good one at the best price I have found. 

 

The OPT's are at Mouser. https://www.mouser.com/ProductDetail/546-125CSE  This is the first build I have done using these transformers. Maynard likes them so I expect them to work as good as the Edcor's I have been using for years. I am trying to get away from the long build time of the Edcor's. Looking at them they look fine. As big as the 10 watt Edcor's and actually weigh a little more. Being practical OPT's are just wire wrapped around an iron core. I see no reason for them not to sound as good as Edcor. Tubedepot.com just started carrying the Hammond 125DSE for just a little more money. https://www.tubedepot.com/products/hammond-universal-single-ended-tube-output-125dse  Do not let the frequency response quoted by Hammond of their transformers scare you. They are rated at full power, 8 watts for the c's and 10 watts for the d's George Anderson tested the 125CSE's and found them really good. http://tubelab.com/articles/component-testing/budget-output-transformers/   This is the frequency response George found at 1 watt.   "Specs at 1 watt: frequency response is 11.7Hz to 42.9KHz with 50mA"  50ma is what Maynard designed this amplifier to bias at and 1 watt is what if makes. 

 

The rest of the parts came from Mouser, Amazon and Tubedepot. Below is the bits I used to make the holes. They came from Harbor Freight. Cheap and good enough. I use a drill press but it can be done with a hand drill. 

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You will need a few pieces of equipment if anyone decides to build this project. I have been using this soldering station for a number of years. I am on my second one the last one giving me good service and a lot of hours. https://www.parts-express.com/Stahl-Tools-STSSVT-Variable-Temperature-Soldering-Station-374-100

You sill also need solder of course. Get the 60/40 solder. Yes the one with lead. The non lead solder takes skill to use and not worth the bother for such a little amount required in electronic work. More problems result from poor cold solder joints than any other problem with builds. You want to make a good mechanical connection first then heat both parts enough to melt the solder and not the iron melting the solder onto the parts. Do not be afraid of overheating components. They are hard critters to destroy. The new tiny components used these days are placed on a board on a solder pad by a robot. with the solder already there. Then they are put in an oven and heated enough to melt the solder on the pads underneath the part. Those parts are real tiny. If one sneezes looking at one good luck ever seeing it again. Of course you can burn a component up but you are more likely to not flow the solder than to destroy a component. I cannot remember ever overheating a component soldering where it did not work. You will also need a multimeter, preferable auto ranging. Even a very cheap one will be accurate enough for this. I have some $5 ones that still work as good as the expensive ones I have. Test every resistor before installing it with the meter. Less chance of making an error this way. There is no adjustments that need to be made after assembling this amplifier. No reason for you to be inside the amplifier poking around while it is on and hot. I do recommend building a light bulb current limiter. https://www.youtube.com/watch?v=wRFRwOnLsZI   Not hard to build and parts can be had at a hardware store. With it you will not see smoke if you make a mistake. Other than these things you will need what most every handy man around the house has as far as tools go. I hope there are those that follow through and build one of these amplifier. 

 

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Henry brings up a good point... a good soldering station. My preference has always been Weller. Only because I have the most experience with them and parts are cheap & easy to come by if you need them. I currently have a WES51. I have had it for about 10 years and it is still going strong. The new(er) one to replace it has a digital display WE1010NA, but other than that, it should be the same great iron/station. 

 

Weller is not the cheapest, but they are great products. They get up to temperature extremely fast and the temperature regulation is unmatched. 

 

Soldering tips are also nominally priced, so that is a plus. 

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I am going to try and proceed as though anyone that is following knows little if anything about building an amplifier. So the more experienced electronic members will have to be patient and or contribute on this thread your way of doing it. I want others to join in on the fun. This project is not all about me. Just my way. I want others to contribute too. We have many talented builders here. Someone here can try and answer any questions arising during this build. So ask away if you are interested. 

 

As said before I am going to use the KISS system. I want to try and get more people involved in diy amplifier building. Fun and rewarding with our speakers. Those wonderful SET tube amplifiers only speakers like ours can really enjoy. Most of those other brands need more power before they wake up. I got my scanner working again this morning so I can publish papers without having to take pictures of them. I lose the software for the scanner every time windows updates. 

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19 hours ago, henry4841 said:

One way to get around that IEC cutting out is to do what Maynard just told me he does. From his pen:   I get around the IEC socket dilemma by using a hard wired cord and strain relief.

I usually prefer a hard wired power cord. The only benefit I get from the IEC cord is to swap out different lenghts, but I don't even do that.

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14 minutes ago, Khornukopia said:

I usually prefer a hard wired power cord. The only benefit I get from the IEC cord is to swap out different lenghts, but I don't even do that.

A good way to get a power cord to do it this way is buy a computer cord and cut the end off for it to be hard wired to the amplifier. They are plentiful and cheap. 

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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.
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