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Other Stuff => Archived Manufacturer Circles => Music Reference => Topic started by: Roger A. Modjeski on 1 Feb 2013, 05:03 pm

Title: Breadboard project amplifiers
Post by: Roger A. Modjeski 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.
Title: Re: Breadboard project amplifiers
Post by: escultor on 3 Feb 2013, 04:42 pm
I will order the EM7 as soon is offered....Hopefully
Title: Re: Breadboard project amplifiers
Post by: Ericus Rex 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?
Title: Re: Breadboard project amplifiers
Post by: bummrush on 3 Feb 2013, 09:57 pm
Keep us posted. Interesting.
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski 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.
Title: Re: Breadboard project amplifiers
Post by: adydula on 5 Feb 2013, 12:51 am
Hello...

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

Lets build some stuff!!

Alex
 :D
Title: Re: Breadboard project amplifiers
Post by: Ericus Rex 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?
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski 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.
Title: Re: Breadboard project amplifiers
Post by: escultor on 8 Feb 2013, 09:30 pm
Looks like a great deal... any chance to get  the 5 watts ??
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski 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?
Title: Re: Breadboard project amplifiers
Post by: Ericus Rex on 10 Feb 2013, 12:55 am
Would the 5 watt version sound better since it's fixed bias?
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski 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.
Title: Re: Breadboard project amplifiers
Post by: steve f 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. 
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski 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.
Title: Re: Breadboard project amplifiers
Post by: steve f 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
Title: Re: Breadboard project amplifiers
Post by: escultor 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 ??
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski 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.
Title: Re: Breadboard project amplifiers
Post by: escultor 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...
Title: Re: Breadboard project amplifiers
Post by: Ericus Rex 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?
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski 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.
Title: Re: Breadboard project amplifiers
Post by: escultor on 13 Feb 2013, 03:39 pm

  I like the 10 watts , can you tell us more ...like cost in kit form
Title: Re: Breadboard project amplifiers
Post by: roberts4152 on 27 Feb 2013, 02:58 pm
  I like the 10 watts , can you tell us more ...like cost in kit form

I am also very interested in the 10 or 12 watt kit.  Including 8 and 16 ohm output taps would be a big plus for me.
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski on 16 Mar 2013, 08:32 pm
I am also very interested in the 10 or 12 watt kit.  Including 8 and 16 ohm output taps would be a big plus for me.

The transformers can be wound with taps. My best 10 watt is EM7 triodes push-pull with little or no feedback.

I also have a design that combines this 10 watt amp for the woofer with a Single Ended EM7 for the tweeter. Each amp is mono and includes the crossover at the input. Therefore one need run one signal cable to the amp beside the speaker and two short runs to the drivers. In any multi-way speaker the weakest link is the crossover that follows the amplifier as it has to handle low impedance drivers. Although some omit the series woofer choke due to its expense it is a big mistake to let the woofer roll off on its own as the response is very ragged in this region. It is far better to separate the frequencies before the power amps with simple resistor-capacitor filters. Then each amp and its output transformers can be optimized for its frequency range. A volume control is included to match the generally more sensitive tweeter with the woofer. This volume control is a handy way to change the tonal balance of the speaker at will. One of my customers who has this says he can't imagine living without it. He simply trims the highs based on what he hears on a particular recording to suit that recording. If you have never had this option, well you don't know what you are missing. Haven't you often wanted a little more or a little less treble from some recording?

This also fixes a common problem when driving a two way speaker with SE amps. Many two way speakers have impedance peaks or dips around the crossover point or some other place where the designer inserted a network to trim the frequency response to his desires. Since most SE amps have rather high output impedance this causes the speaker's response to be amplifier dependent. To hear what that speaker designer heard you would have to use an amp with his output impedance (Load Z/damping factor). Now, if we have a simple two way system (woofer and tweeter) we have two drivers whose impedance is generally more constant when seen directly than through a crossover. In this case the damping and difference in damping is far less critical. This is the correct way to do things and it's really quite simple. Do you know that most single drivers are constant impedance over their usable range due to the simple fact that they are mass loaded? This is what Rice and Kellogg realized in 1924 when they invented the moving coil loudspeaker for General Electric.

This is available for $1500 per mono two-way amp using 3-13EM7 tubes and 1-6BQ7 with solid state rectifier.  $1900 with a 5Y3/5AR4 family rectifier and choke input filter. Anyone making a two way speaker should consider this option over expensive exotic crossover caps and inductors. I think it demonstrates a lack of imagination to do things the conventional way (passive crossover at the speaker) when for about the same money it can be done a much better way.
Title: Re: Breadboard project amplifiers
Post by: corndog71 on 31 May 2013, 02:08 pm
While the base EM-7 kit is tempting I still would like a bit more power. 

I'd much rather work on an RM-10 or an unbalanced version of the RM-200.  Just the transformers and schematic would probably be the most economical for me.  Then I could take my time getting the rest of the parts.
Title: Re: Breadboard project amplifiers
Post by: IkeH on 31 May 2013, 08:17 pm

Hi Roger,

Sorry I have been bit out of touch with hifi and I just noticed this post.
I am definitely interested purchasing "your best 10 watt EM7 PP" DIY amp kit.   I would hope you can offer one that is simple and with options for upgrades.
I would like power transformer that can be wired for input voltage where ever you may be (i.e. 120V, 230V etc.)  I would  prefer output taps at 4 and 8 ohms.
 
Ike
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski on 1 Jun 2013, 04:22 pm
Hi Roger,

Sorry I have been bit out of touch with hifi and I just noticed this post.
I am definitely interested purchasing "your best 10 watt EM7 PP" DIY amp kit.   I would hope you can offer one that is simple and with options for upgrades.
I would like power transformer that can be wired for input voltage where ever you may be (i.e. 120V, 230V etc.)  I would  prefer output taps at 4 and 8 ohms.
 
Ike

With those options the kit built on a breadboard would be $900 per amp.  I would provide but not mount the power inlet, switch, input and output connectors. You would have nothing to buy but the material to make the case of your choice. I am also offering the amp complete in a wood case for $1200 each.

Is anyone interested in just parts and a schematic?
Title: Re: Breadboard project amplifiers
Post by: IkeH on 2 Jun 2013, 03:49 pm
Hi Roger,

Thanks for the quick reply.  I also watched your youtube video on EM7 amp as well as the video on preamp.  I really appreciate that you were able to explain the subjects in a very simple way that non-technical person (like me) can understand.   I hope you would keep on going.

I have a question, What would be the difference between "kit built on a breadboard" vs parts and schematics in terms of what are included  and the price?   

Thanks,
Isaku

Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski on 2 Jun 2013, 06:22 pm
The parts are the same in both cases. The breadboard is built and tested but on a board, not in an enclosure. By mounting and soldering the input, output and power connectors the builder will have a complete working amp in a case of his choice.

Parts and a schematic means the builder gets a box of parts, resistors marked on a piece of cardboard, the rest the builder is required to identify and wire up as per a schematic. With no detailed instructions the builder needs to have considerable experience.
Title: Re: Breadboard project amplifiers
Post by: poseidonsvoice on 2 Jun 2013, 10:21 pm
The parts are the same in both cases. The breadboard is built and tested but on a board, not in an enclosure. By mounting and soldering the input, output and power connectors the builder will have a complete working amp in a case of his choice.

Parts and a schematic means the builder gets a box of parts, resistors marked on a piece of cardboard, the rest the builder is required to identify and wire up as per a schematic. With no detailed instructions the builder needs to have considerable experience.

Parts and schematic is fine for me as long as you are accessible for any trouble shooting that may arise.

Best,
Anand.
Title: Re: Breadboard project amplifiers
Post by: jtwrace on 2 Jun 2013, 11:12 pm
Parts and schematic is fine for me as long as you are accessible for any trouble shooting that may arise.

Best,
Anand.
What?  You're a pro!!!   :thumb:
Title: Re: Breadboard project amplifiers
Post by: poseidonsvoice on 3 Jun 2013, 01:37 pm
Parts and schematic is fine for me as long as you are accessible for any trouble shooting that may arise.

Best,
Anand.

I just saw the video. It's very well done. I agree, it's an excellent venue to teach the basics of tube design and to clear out all the misconceptions - of which there are too many!

Oh...and also count me in as interested in your 10 watt push pull design, that is 4 times more than your 2.5 watt design, and is more suitable to my system. Just schematic, matched tubes and transformers. Everything else I can get. "Barebones" kit. Handholding from our guru, Roger, is optional!  :wink:

Best,
Anand.
Title: Re: Breadboard project amplifiers
Post by: usp1 on 3 Jun 2013, 03:54 pm
This sounds very interesting. Several of you mention seeing a video, but I can't find a link. Can someone post a link please?

Thanks.
Title: Re: Breadboard project amplifiers
Post by: Ericus Rex on 3 Jun 2013, 05:37 pm
This sounds very interesting. Several of you mention seeing a video, but I can't find a link. Can someone post a link please?

Thanks.


http://www.youtube.com/user/MusicReferenceAudio/videos
Title: Re: Breadboard project amplifiers
Post by: acresm22 on 3 Jun 2013, 05:43 pm
Roger, is the breadboard 2.5 watt EM7 project the exact same circuit design as the initial crop of EM7 amps that MR produced about 6-7 years ago?
Title: Re: Breadboard project amplifiers
Post by: usp1 on 3 Jun 2013, 09:00 pm

http://www.youtube.com/user/MusicReferenceAudio/videos

Thank you!
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski on 4 Jun 2013, 04:21 am
Roger, is the breadboard 2.5 watt EM7 project the exact same circuit design as the initial crop of EM7 amps that MR produced about 6-7 years ago?


Yes it is the same amplifier without the casework.
Title: Re: Breadboard project amplifiers
Post by: steve f on 14 Jun 2013, 08:12 pm
The video shows an amp with single output taps. Can you have both 4 and 8 taps on a kit version? I would personally find a single tap a bit limiting.

Steve
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski on 20 Jun 2013, 09:48 pm
The video shows an amp with single output taps. Can you have both 4 and 8 taps on a kit version? I would personally find a single tap a bit limiting.


Steve

As it turns out with this amplifier the difference between 4 and 8 ohms is very small. Therefore I decided not to put on a 4 ohm tap, However a 2 ohm tap represents enough difference to be noticed and that could be made available.  The 2 ohm tap would have half the voltage and twice the current. If someone insists on a 4 ohm tap (.707 of the secondary winding) a special pair of outputs can be wound for $150 up charge.

The interest in the kits has been very small. Until that interest increases they are on the back burner. If I get 5 orders I will make the kits available at $750 on a breadboard as per our price list.
Title: Re: Breadboard project amplifiers
Post by: steve f on 20 Jun 2013, 10:09 pm
 I'm the only person who wants to build a custom case for an EM-7?  That's a shame.
Steve
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski on 21 Jun 2013, 02:40 am
I'm the only person who wants to build a custom case for an EM-7?  That's a shame.
Steve

It appears so Steve. I am also surprised. We have come down a long road from the Heathkits I grew up on. I think its really a sign of the times. In the 1960s there weren't so many things taking one's attention and there weren't so many audio products and people wanted to learn about how things worked. I think most kits were built for the acquisition of electronic knowledge, ability to repair one's own equipment, the cost savings and the fact that it really was a hobby. The good kits were designed by good engineers. Many tube amplifiers from large companies like ARC and CJ don't even come close to the performance of the better kits and their construction makes them very difficult to service. To make matters worse audio has largely become jewelry and many audiophiles believe more in voodoo than science.
Title: Re: Breadboard project amplifiers
Post by: steve f on 22 Jun 2013, 04:38 pm
Okay guys,
I can't be the only audiophile out there who enjoys building things. Roger has posted that he needs to sell about 5 of these semi-kits to make it a feasible. So come on. Join in the fun.   :D


Steve
Title: Re: Breadboard project amplifiers
Post by: steve f on 29 Jun 2013, 05:56 pm
Wow, nobody else is interested. Okay, I'll forget all about EM amps and start saving for the RM 10 instead.

Steve
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski on 29 Jun 2013, 06:59 pm
I am making a pair of EM7 monos for a customer. If anyone else wants any of the EM7 series amps now is a good time to order them. Some customization is possible such as XLR inputs, outputs, wood and finish options. If I get several orders for complete EM7 2.5 watt/ch amps or kits I will make both available. To order contact musref.roger@gmail.com

Price list: http://ramlabs-musicreference.com/pricelist.html
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski on 30 Sep 2013, 08:33 am
We recently shipped a customized breadboard EM7 to a happy customer. We added a volume control for him.
Title: Re: Breadboard project amplifiers
Post by: vinylrules on 19 Oct 2013, 06:41 pm
Hi Roger, I've just signed up and am navigating my way around the site. Wondering if you've ever thought about a truly low powered OTL amplifier. Since typical OTL amps require lots of output tubes, which leads to inevitable increases in heat and cost and also tends to reduce reliability, it seems like someone would have tried making a 5 or 10W OTL for the high impedance / high efficiency loudspeaker crowd.
Title: Re: Breadboard project amplifiers
Post by: Roger A. Modjeski on 22 Oct 2013, 09:41 pm
Hi Roger, I've just signed up and am navigating my way around the site. Wondering if you've ever thought about a truly low powered OTL amplifier. Since typical OTL amps require lots of output tubes, which leads to inevitable increases in heat and cost and also tends to reduce reliability, it seems like someone would have tried making a 5 or 10W OTL for the high impedance / high efficiency loudspeaker crowd.

This question comes at an opportune time as I am in the process of designing such an amplifier. So far I have something with two output tubes and one driver tube per channel. It can provide 0.7 amps into any load up to 100 ohms. Into 8 ohms that is not much power, similar to an SET but at much lower distortion and better damping. Into 100 ohms its 25 watts. Is this what you have in mind?