Jump to content

Little Sweetie Forum amplifier project


henry4841
 Share

Recommended Posts

With the 560 ohm resistor in the power supply and 100mA load I'm getting only 217v on the node feeding the output transformer. 

 

To get the full rated output power of the circuit and the 200v across the 6Y6 plate to cathode Henry is going to have to reduce the 560 ohm value down to around 120-150 ohms. That should put the supply feeding the OPT around 250v which will give the spec Maynard is calling for.

 

I think there was some confusion to reading the schematic and people forget that power tube plate voltage is reading to ground and subtract the cathode voltage, plus the voltage drop across the primary of the OPT.

 

 

Link to comment
Share on other sites

21 hours ago, captainbeefheart said:

With the 560 ohm resistor in the power supply and 100mA load I'm getting only 217v on the node feeding the output transformer. 

 

To get the full rated output power of the circuit and the 200v across the 6Y6 plate to cathode Henry is going to have to reduce the 560 ohm value down to around 120-150 ohms. That should put the supply feeding the OPT around 250v which will give the spec Maynard is calling for.

 

I think there was some confusion to reading the schematic and people forget that power tube plate voltage is reading to ground and subtract the cathode voltage, plus the voltage drop across the primary of the OPT.

 

 

I knew there were additional voltages, but I was being lazy and figured Henry would fill in the blanks. 

Link to comment
Share on other sites

19 minutes ago, Curious_George said:

I knew there were additioanl voltages, but I was being lazy and figured Henry would fill in the blanks. 

 

Ya I wanted to reiterate the entire situation because I have a feeling he was shooting for 200v B+ and not 250v, hence the larger dropping resistor. Maynard should have added more voltage references on the Schematic but he probably assumed an amp builder would know?

Link to comment
Share on other sites

Morning guys. I need to try and explain what I am trying to teach here. I am just a kit builder. You put me in a room with those guys yesterday talking about designing and they were to ask me what I thought I would have to say "no English." As a kit builder, which I hope some of you become, you will have to trust that whoever designed the circuit you are trying to put together has already done the paper work and the testing after he built the amplifier before he published his design. In other words if I worked at an electronic place I would be on the floor stuffing boards, soldering or something like that. I would not go near the designing room. These days, with few kits available, you have to put your kit together yourself. I am just one who if you assemble all the parts together and give me some instructions I want to take on the challenge of putting them together and see if I can make them work. Your instruction now is going to have to be the schematic. I am trying to teach you how to read a schematic where you will have instructions. Everything you need is in the schematic to put these parts together. Over the years, I started putting kits together in my 20's, I like to think I have advanced a little in that I now have a signal generator and scope to do some checking on the circuits after building the kit. With a scope you can check the power supply circuit and see what your DC looks like at the plate of the tubes if you choose to. I usually do not do that though trusting that the designer has already done that and thinks the DC is clean enough for his design. About all I do with my scopes, I now have 4 of them, is check the signal to make sure it looks good and there is nothing nasty there to see. That is about all I know how to do with a scope. I just always wanted a scope when I was young but those things were expensive back then the reason I have four of them. Now there are some really decent scopes you can buy rather cheap at todays money. These new digital scopes can do so much, almost make your coffee in the morning. I must say it is nice to have those experience builders looking over my shoulder making sure I am not making mistakes. But trying to understand some of the things they were writing made me tired. I just know a little of the electronic language. I get lost around those guys pretty quick when they start talking the things they were talking about. Good to have really smart guys on the forum though. Try and learn something from them. In other words be smart and use them. 

 

You potential kit builders really need a Mouser parts list with numbers where you can just buy all your parts just by typing in the numbers. I am going to try and do that for you this morning since I am up early. Then you can order the other parts needed like RCA input and speaker out things, terminal strips etc from places like Tubedepot. 
 

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

The other page. Best I can do. Not very computer savvy when it comes to scanning pages and saving them. Hope someone can do better. I do have the project saved at Mouser and if you make an account at Mouser I can forward the project a more legible way and where you can just click on buy project and get all the parts I have listed. I did not do much part quality choosing generally picking the best price. You have to trust that a big electronic warehouse does not want to sell inferior parts and the ones offered are good quality. At least one hopes so and I have never had a problem with any parts failing for that reason from Mouser. I usually order more than one of the cheap parts not wanting to pay shipping if I loose one of those cheap ones having to pay $10 shipping for a 10c part. 

 

Almost forgot, don't cuss me too much if I have made a mistake with this list costing you shipping getting something else I missed or made a mistake with a part. 

Scan4.PDF

  • Thanks 1
Link to comment
Share on other sites

Many of the power supply and other questions were previously raised by former forum member xxJPMxx in the original thread, and answers were provided.  
 

If the amps are constructed as mono units with the specified parts, the only voltage reference really needed is the plate to cathode voltage of the 6Y6.  We can safely assume that the other voltages will follow.  The reference point for specified electrode voltages in manufacturer tube data is always to the cathode in tubes having one.  
 

In the original thread, John Lumley posted his power supply variant which some may find interesting and informative.  And, former forum member wdecho posted his FFT measurement of the amp which is interesting as well.

 

I agree with Henry that his build thread should be kept on the non-technical side.  His implementation has worked very successfully and anyone emulating his work should expect to obtain similar results.  
 

I suggest starting a new thread for improvements to the original design for those more technically inclined.  Suggesting changes to the design based on calculations without experiencing the original is analogous to a chef wanting to improve a recipe without tasting the original form.  
 

Maynard


 


 

 

  • Like 3
  • Thanks 1
Link to comment
Share on other sites

32 minutes ago, tube fanatic said:

Many of the power supply and other questions were previously raised by former forum member xxJPMxx in the original thread, and answers were provided.  
 

If the amps are constructed as mono units with the specified parts, the only voltage reference really needed is the plate to cathode voltage of the 6Y6.  We can safely assume that the other voltages will follow.  The reference point for specified electrode voltages in manufacturer tube data is always to the cathode in tubes having one.  
 

In the original thread, John Lumley posted his power supply variant which some may find interesting and informative.  And, former forum member wdecho posted his FFT measurement of the amp which is interesting as well.

 

I agree with Henry that his build thread should be kept on the non-technical side.  His implementation has worked very successfully and anyone emulating his work should expect to obtain similar results.  
 

I suggest starting a new thread for improvements to the original design for those more technically inclined.  Suggesting changes to the design based on calculations without experiencing the original is analogous to a chef wanting to improve a recipe without tasting the original form.  
 

Maynard


 


 

 

I agree, we should keep to the original intent of building this amp as designed.

 

However, I must disagree about the lack of voltages on the schematic. A schematic with voltage references is a very handy thing when troubleshooting. It is also just good practice. You should know you can't assume anything when building and for new builders, measuring a voltage to ensure everything is working correct can be very helpful and reassuring.

 

Each node with a relevant voltage should be indicated. It does not cost anything other than a few extra moments annotating it. 

 

 

  • Like 3
Link to comment
Share on other sites

11 minutes ago, Curious_George said:

I agree, we should keep to the original intent of building this amp as designed.

 

However, I must disagree about the lack of voltages on the schematic. A schematic with voltage references is a very handy thing when troubleshooting. It is also just good practice. You should know you can't assume anything when building and for new builders, measuring a voltage to ensure everything is working correct can be very helpful and reassuring.

 

Each node with a relevant voltage should be indicated. It does not cost anything other than a few extra moments annotating it. 

 

 

Sure helps having voltage readings on schematics of old receivers I work on. A good technician can fix most repairs of electronic equipment with just a multimeter checking voltages.  

  • Like 1
Link to comment
Share on other sites

4 hours ago, henry4841 said:

Guys this is the best I can do scanning the parts list at Mouser. I hope someone that knows how better makes sure I have it right and maybe make a spreadsheet. 

Scan2.JPG

Scan1.PDF 86.75 kB · 1 download Scan3.TIF 1 MB · 1 download

I will volunteer to create a parts list spreadsheet. It may take a little time because there may need to be a little back and forth to make sure I get it correct, but I don't get the sense that there is a huge rush.

  • Thanks 1
Link to comment
Share on other sites

10 minutes ago, CWelsh said:

I will volunteer to create a parts list spreadsheet. It may take a little time because there may need to be a little back and forth to make sure I get it correct, but I don't get the sense that there is a huge rush.

That is great news !!!!!!!! It will be wonderful for a beginner builder. A first timer really needs numbers he can order parts by. You do not know how much I am going to appreciate this. The only goal for this thread is to get some newbies building there own amp. PM if you need any help with selections or errors I have made. Thank you, thank you, thank you. 

Link to comment
Share on other sites

3 minutes ago, henry4841 said:

That is great news !!!!!!!! It will be wonderful for a beginner builder. A first timer really needs numbers he can order parts by. You do not know how much I am going to appreciate this. The only goal for this thread is to get some newbies building there own amp. PM if you need any help with selections or errors I have made. Thank you, thank you, thank you. 

I'm thrilled to have something to contribute to this project. I have zero experience building tube amps, so I'm following this thread and trying to learn. Spreadsheets, on the other hand, I can do...LOL

  • Like 1
Link to comment
Share on other sites

1 minute ago, billybob said:

Earlier on, the @The DudeDude replied about a spreadsheet that can be exported on the Mouser website.

I will check that out. I have some ideas in mind for what I think I would like to see as a beginning builder, but having something to start with would be a huge help. Thank you for the heads up!

  • Like 1
Link to comment
Share on other sites

2 minutes ago, CWelsh said:

I will check that out. I have some ideas in mind for what I think I would like to see as a beginning builder, but having something to start with would be a huge help. Thank you for the heads up!

Here is a BOM you can use for a template. Just to give you an idea. Change as desired. 

300B Stereo Amp BOM_v1.0.0_010722.ods

Link to comment
Share on other sites

14 minutes ago, CWelsh said:

I will check that out. I have some ideas in mind for what I think I would like to see as a beginning builder, but having something to start with would be a huge help. Thank you for the heads up!

Yes, please let know what you find. Thanks!

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...