Poll

What is the interest in making simple amps and preamps

I would like to make a simple line preamp
5 (11.9%)
I would like to make a simple 2-10 watt power amp
19 (45.2%)
I would like to make a phono stage
5 (11.9%)
I would like to make a MC head-amp for my existing phono system
1 (2.4%)
I am intersted in projects up to $300
2 (4.8%)
I am interested in projects up to $600
0 (0%)
I am interested in projects up to $1000
6 (14.3%)
I am interested in projects up to $1500
2 (4.8%)
I am interested in projects above $1500
2 (4.8%)

Total Members Voted: 42

Breadboard project amplifiers

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Roger A. Modjeski

Breadboard project amplifiers
« on: 1 Feb 2013, 05:03 pm »
I am working on some DIY projects where I provide all the electrical parts and in some cases these parts are already connected into a working and tested amplifier. I will make a video to show them and what you can do to make them into a finished project. The projects that are already tested come on a unfinished plywood base and the user simply hooks up input, output and power.

The first that I plan to offer is the 2.5 watt/ch EM7 amplifier. It comes on a plywood base that holds together the aluminum amplifier sub chassis (supplied wired), the output transformers and parts for the power supply (transformer and filter caps). The video will make this clear.

At this point I want to know how many here would like these or know others who might. I want to give my members here first call before I expose it to the DIY web sites.

escultor

  • Jr. Member
  • Posts: 9
Re: Breadboard project amplifiers
« Reply #1 on: 3 Feb 2013, 04:42 pm »
I will order the EM7 as soon is offered....Hopefully

Ericus Rex

Re: Breadboard project amplifiers
« Reply #2 on: 3 Feb 2013, 09:52 pm »
Would this be the exact 2.5 EM7 (sans lovely wooden chassis) you were making a few years back?

bummrush

Re: Breadboard project amplifiers
« Reply #3 on: 3 Feb 2013, 09:57 pm »
Keep us posted. Interesting.

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #4 on: 5 Feb 2013, 12:37 am »
Would this be the exact 2.5 EM7 (sans lovely wooden chassis) you were making a few years back?
Yes  it is the 2.5 EM7. I will have the video up soon along with a suggested speaker project that went with it using the FE-103 driver.

adydula

  • Full Member
  • Posts: 1301
Re: Breadboard project amplifiers
« Reply #5 on: 5 Feb 2013, 12:51 am »
Hello...

Just looked at your gallery.....AG1Q here!!

Lets build some stuff!!

Alex
 :D

Ericus Rex

Re: Breadboard project amplifiers
« Reply #6 on: 7 Feb 2013, 05:42 pm »
Just saw the new video.  Looks like a nice simple design!  Have you worked out pricing for the amp?  Could you supply it as parts and allow the buyer to assemble it for some added fun/learning?  If so, what would then be the parts price?

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #7 on: 7 Feb 2013, 06:49 pm »
Just saw the new video.  Looks like a nice simple design!  Have you worked out pricing for the amp?  Could you supply it as parts and allow the buyer to assemble it for some added fun/learning?  If so, what would then be the parts price?

You are the first to find it. Here is the direct link to the EM7 video. http://www.youtube.com/watch?v=7qg9ot20EdA   It is about 12 minutes. We now have 5 videos up.

I have it on the MR price list at $750 for the ready to play unit on a 1/4 inch bare high quality particle breadboard with a bare drilled top which helps keep fingers and dust out.

If someone wants to build it from a schematic with loose parts I can provide that for $350 plus $40 shipping. If they want the 1/4 inch top and bottom drilled, not painted is $50.

In both cases a pair of matched tubes is included.

escultor

  • Jr. Member
  • Posts: 9
Re: Breadboard project amplifiers
« Reply #8 on: 8 Feb 2013, 09:30 pm »
Looks like a great deal... any chance to get  the 5 watts ??

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #9 on: 9 Feb 2013, 07:38 pm »
Yes, I developed and sold many 5 watt/channel units. They are a bit more complex as they require fixed bias and a pot to adjust it. This also adds a bias supply and a bigger power transformer. If there is enough interest I can make that available. However that's only 3 dB more listening level... is it worth the trouble?

Ericus Rex

Re: Breadboard project amplifiers
« Reply #10 on: 10 Feb 2013, 12:55 am »
Would the 5 watt version sound better since it's fixed bias?

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #11 on: 10 Feb 2013, 03:40 am »
Would the 5 watt version sound better since it's fixed bias?

When driven hard it will by comparison to cathode bias. With cathode bias the tube current goes down due to charging of the cathode capacitor making the bias more negative. However the distortion is rather large at this point. SE amps are not meant to be driven into clipping.

steve f

  • Full Member
  • Posts: 349
Re: Breadboard project amplifiers
« Reply #12 on: 10 Feb 2013, 02:31 pm »
Roger,

This sounds like a great project to introduce new audiophiles to your products, and/or a project for a bunch of us old guys to share with the next generation. Sto lat.

Steve

PS: How about providing suggested step by step assembly instructions like Heath & Dynaco did so many years ago? In this day of digital cameras and printers, costs would be minimal, and the benefits priceless. 

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #13 on: 10 Feb 2013, 06:39 pm »
Roger,

This sounds like a great project to introduce new audiophiles to your products, and/or a project for a bunch of us old guys to share with the next generation. Sto lat.

Steve

PS: How about providing suggested step by step assembly instructions like Heath & Dynaco did so many years ago? In this day of digital cameras and printers, costs would be minimal, and the benefits priceless.
My intent in offering this kit is twofold. One is to educate which is what the video is about. For that task, YouTube is a wonderful use of the internet and I am thankful for the this tool. The other is to provide a very good amplifier at a very good price by letting the owner do the casework, which is often half the cost of modern audio components.

Those step by step manuals from Heath took hundreds of hours of prep which I don't believe would be much faster today. A computer can help you write a book but you still have to write the book and do the research. Kits were their main business, however it is not mine. They also had hundreds of people to "kit up" the parts in a very efficient manner of their own creation. The last facility they built was 100,000 square feet. That's how well things were going then. From 1960 to 1970 I got a kit for my birthday and one for Christmas and bought several myself. I must have built 20 kits including Knight (Allied Radio) and Eico.  Now there is not one single major kit company.

I believe members like Ericus Rex can build from a schematic and although that was not my original intent I will make the parts available. My intent is to offer a wired and tested kit for users to finish to their taste. In either case you are getting a circuit design and parts that exceed what others are offering. As I pointed out in the video, some designers are using LEDs to bias a tube and I have explained why this is not a good idea. In later videos I will go into parafeed output stages, the theory behind ElectraPrint's "Ultrapath" that was developed by Western Electric, the reasons why SE output transformers have a gap, where the other half of the sine wave comes from as the tube cuts off.

Although Heath and Eico had great instructions,  many of their circuit designs left a lot to be desired. When I was 16 I built an Eico Cortina amplifier which was a nice amp, however when switched to mono playing records there was a great deal of distortion. I fixed this by putting a 4.7 K isolating resistor on the output of each phono preamp so that one would not try to drive the other. I wondered how at 16 I was fixing a design made by skilled engineers at a major kit company.

steve f

  • Full Member
  • Posts: 349
Re: Breadboard project amplifiers
« Reply #14 on: 10 Feb 2013, 10:40 pm »
I understand. I've assembled various kits, including a modern OTL. I only once wrote an assembly manual. It was just a few pages, done as a favor for a guy who claimed to be a woodworker. I designed a speaker for him. He insisted on his ability to follow instructions to the letter. As you already know, it took longer to write and draw than it would have taken to just build everything for him. The kicker was that after over five years later, he never built them, and asked for his money back! Maybe no good deed goes unpunished is a truth, not just a figure of speech.

This little amp will meet the needs of a lot of people. I look forward to more videos.

Steve

escultor

  • Jr. Member
  • Posts: 9
Re: Breadboard project amplifiers
« Reply #15 on: 10 Feb 2013, 11:33 pm »
Yes, I developed and sold many 5 watt/channel units. They are a bit more complex as they require fixed bias and a pot to adjust it. This also adds a bias supply and a bigger power transformer. If there is enough interest I can make that available. However that's only 3 dB more listening level... is it worth the trouble?

  OK how about mono blocks ??

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #16 on: 12 Feb 2013, 05:33 pm »
  OK how about mono blocks ??

Monoblocks are not a problem. Their cost is about twice as much due to duplication of the chassis and power supply.

escultor

  • Jr. Member
  • Posts: 9
Re: Breadboard project amplifiers
« Reply #17 on: 12 Feb 2013, 06:09 pm »
Monoblocks are not a problem. Their cost is about twice as much due to duplication of the chassis and power supply.

 OK will order them...

Ericus Rex

Re: Breadboard project amplifiers
« Reply #18 on: 12 Feb 2013, 08:42 pm »
Monoblocks are not a problem. Their cost is about twice as much due to duplication of the chassis and power supply.

Would these be the 12 watt EM7 amp?  Or are we talking 2.5 watt monos with 1 tube per chassis?

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #19 on: 12 Feb 2013, 11:02 pm »
Would these be the 12 watt EM7 amp?  Or are we talking 2.5 watt monos with 1 tube per chassis?

The power transformer and the bracket that holds the tubes are set up for 2 tubes. Might as well use two tubes per amp. Since each tube has a driver and output the outputs would be connected in parallel and the extra driver could be used at a preamp tube to make an integrated or high gain power amp.

I have also made a no-feedback triode push-pull monoblock which can take balanced or unbalanced inputs. It puts out about 10 watts.