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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escultor

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Re: Breadboard project amplifiers
« Reply #20 on: 13 Feb 2013, 03:39 pm »

  I like the 10 watts , can you tell us more ...like cost in kit form

roberts4152

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Re: Breadboard project amplifiers
« Reply #21 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.

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #22 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.

corndog71

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Re: Breadboard project amplifiers
« Reply #23 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.

IkeH

Re: Breadboard project amplifiers
« Reply #24 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

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #25 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?

IkeH

Re: Breadboard project amplifiers
« Reply #26 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


Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #27 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.

poseidonsvoice

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Re: Breadboard project amplifiers
« Reply #28 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.

jtwrace

Re: Breadboard project amplifiers
« Reply #29 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:

poseidonsvoice

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Re: Breadboard project amplifiers
« Reply #30 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.

usp1

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Re: Breadboard project amplifiers
« Reply #31 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.

Ericus Rex

Re: Breadboard project amplifiers
« Reply #32 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

acresm22

Re: Breadboard project amplifiers
« Reply #33 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?


Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #35 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.

steve f

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Re: Breadboard project amplifiers
« Reply #36 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

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #37 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.

steve f

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Re: Breadboard project amplifiers
« Reply #38 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

Roger A. Modjeski

Re: Breadboard project amplifiers
« Reply #39 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.