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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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17th Apr 2019, 1:08 pm | #21 | |||
Heptode
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 617
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Re: Building a little practical audio amplifier for experimentation
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13th May 2019, 5:56 pm | #22 |
Heptode
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 617
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Re: Building a little practical audio amplifier for experimentation
As Mr Time, the "Implacable", has no mercy of this humble mortal, I'm advancing very slow with this project, as usual. Anyway I have done some advances that I want to share with you. It is already working althought I have not tested it with audio nor a speaker, just a 1kHz signal from my signal generator. The sine wave was clean for a power of about 3W, which is more than enough for what I want. I powered a 10 ohms dummy load.
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13th May 2019, 9:02 pm | #23 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,578
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Re: Building a little practical audio amplifier for experimentation
That is a very impressive construction method....looks like a piece of restored military kit! Well done!
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18th May 2019, 7:56 pm | #24 |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
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Re: Building a little practical audio amplifier for experimentation
I'm probably mistaken about this, but looking at R9, the phasing connections of the O/P transformer and the grid-anode phase relationships of the valves, isn't that feedback via R9 in-phase with any signal appearing on the grid of the first triode - thus increasing the chance of instability?
Al. |
18th May 2019, 11:17 pm | #25 |
Pentode
Join Date: Oct 2018
Location: Coventry, West Midlands, UK.
Posts: 220
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Re: Building a little practical audio amplifier for experimentation
The feedback is going to the cathode of the input stage so it needs to be in phase with the signal on the grid in order to produce negative feedback.
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5th Jul 2019, 3:26 pm | #26 |
Heptode
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 617
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Re: Building a little practical audio amplifier for experimentation
I'm advancing very slow on this project due to lack of available time. Anyway I have begun to build the input block with the three different plugs, which will be connected in "star".
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30th Jul 2019, 9:31 pm | #27 |
Heptode
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 617
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Re: Building a little practical audio amplifier for experimentation
On last weekend I did some advances on this project. I mounted the shield between the transformers and the signal lines (input conectors and volume potentiometer), and also put the input connectors on their place. I played music with the amp for the whole weekend althought it is not finished yet. I have to build the front panel and the built-in speaker cabinet. See some pictures
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23rd Sep 2019, 2:44 pm | #28 |
Heptode
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 617
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Re: Building a little practical audio amplifier for experimentation
This weekend I was able to resume working on this little project. Mr Time the "implacable" has been implacable with me but now I have been able to go on with this. I built the rest of the chassis, but I wasn't able to built the built-in speaker cabinet as the speaker that I have is too big, and there is no roon inside the chassis. I will go to my "war reserve" to find a flatter speaker to fit inside. Anyway I used it this way on weekend.
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8th Oct 2019, 2:55 pm | #29 |
Heptode
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 617
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Re: Building a little practical audio amplifier for experimentation
Finally I found a suitable speaker and I fitted it inside the amplifier. It's from an old Soviet TV.
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11th Oct 2019, 4:45 pm | #30 |
Heptode
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 617
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Re: Building a little practical audio amplifier for experimentation
Yesterday I used this amplifier the whole day. It worked nicely, and it's now fully operational
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11th Oct 2019, 5:39 pm | #31 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,667
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Re: Building a little practical audio amplifier for experimentation
Good work mate, hope you have some brighter paint to paint than your usual battle ship grey or 70's nylon shirt brown : ) A nice bright orange would look well.
Andy.
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11th Oct 2019, 8:47 pm | #32 |
Heptode
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 617
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Re: Building a little practical audio amplifier for experimentation
A phosphorescent pink or violet would be nice too, don't you think?
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12th Oct 2019, 2:22 am | #33 |
Banned
Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 2,704
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Re: Building a little practical audio amplifier for experimentation
I must say Miguel, you do make a beautiful job. I must agree with Andy however
Soviet grey can be a bit over whelming. Superb job however. Did the 807 and valve base come in handy ? Best regards Joe |
12th Oct 2019, 4:27 pm | #34 | |
Heptode
Join Date: Mar 2017
Location: Cedar Grove, Wisconsin, USA.
Posts: 823
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Re: Building a little practical audio amplifier for experimentation
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Ours and your home improvement stores have just about any color paint in any finish you desire. Possibly, not the same there. Fine job done there. Too bad you couldn't fit a larger speaker To do justice to the EL84 output valve and the larger output transformer. Dave, USradcoll1, always interested! |
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14th Oct 2019, 12:18 am | #35 |
Heptode
Join Date: May 2005
Location: Adelaide, South Australia
Posts: 541
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Re: Building a little practical audio amplifier for experimentation
Good job I'm sure you are pleased - while grey may not be the brightest colour around, paint, no matter the colour always improves the look of a project.
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14th Oct 2019, 2:05 am | #36 |
Octode
Join Date: Jul 2011
Location: Staffordshire Moorlands, UK.
Posts: 1,479
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Re: Building a little practical audio amplifier for experimentation
Miguel,
Please do not pay any attention to those who would make trivial comments about "Soviet" paint colours. One does not judge a book by its cover. Your amplifier build is superb and I am sure you will have many happy hours listening to it. Best wishes, Steve.
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14th Oct 2019, 9:20 am | #37 |
Heptode
Join Date: Feb 2011
Location: Southend, Essex, UK.
Posts: 803
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Re: Building a little practical audio amplifier for experimentation
Miguel, trust you and yours are well.
Your amplifier looks superb and I am sure it will stand you well for all of its up and coming projects! Most test amplifiers I am sure remain at no more than a breadboard stage of assembly and get used that way for years. Yours is a proper build. (I'd be tempted to leave it unpainted!!) Alan |
14th Oct 2019, 9:50 am | #38 |
Heptode
Join Date: Sep 2010
Location: Hythe, Hampshire, UK.
Posts: 632
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Re: Building a little practical audio amplifier for experimentation
Miguel,
Really nice to see proper 'homebrew' equipment, you have done an excellent job and should be proud of it! All the best, and keep up the constructing! |