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1	Original Projects and Builds / Other Builds and Projects / Rowe/AMI R-4359 beautification project on: Feb 8^th, 2021, 8:36pm
Started by Administrator \| Post by Administrator
I'm building Tube Amps, and I can't stop! In addition to building a small amplifier based around Russian military tubes and a Chinese SMPS, I have been accumulating parts to build a EH 7591a based amplifier. The Output transformers will come from a Rowe/AMI R-4359 amp chassis that came from a jukebox. The original amp was based on 7868 tubes. 7591's and 7868's are electrically very similar, just in a different basing and envelope, so I also plan to stick with the R-4359 schematic fairly closely. Output Transformers, and the basic circuit design of each channel is where the similarities to the Jukebox Amp will end. The amplifier will be built in a rack-mount chassis (which is also surplus). I am not using the Power Transformer, 5AUG Rectifier tube or any of the original power supply circuitry. Instead, the needed voltages for the tubes will come from a combination of Switch Mode Power Supplies, as I have done for my other projects. A 20Amp rated SMPS will provide 12VDC from a 100-240V input. The 12VDC (at lots of Amps) will power a significantly modified Chinese Inverter module along with a rectifier, filter, and feedback system of my own design. This will provide approximately 380VDC to the plates of the EH 7591a's. Other modular SMPS's will provide the ~6.3V needed for the 7591's heaters, and a +/- output for the tube biasing circuit. It will also contain a high performance DAC to allow USB Audio, as well as Optical and Coaxial SPDIF inputs. Of course there will be straight analog inputs, too. A digital, audio grade relay board will allow push-button switching between the digital inputs and 3 analog inputs. It will also have a VFD Spectrum display on the front panel. Yes, it's an ambitious project, and it has to wait for other projects ahead of it, but in the meantime, here is a rendering so that you can at least see some artwork:
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2	Original Projects and Builds / Other Builds and Projects / 6П14П Amplifier build on: Feb 8^th, 2021, 8:12pm
Started by Administrator \| Post by Administrator
One of several projects in work here at Linuxslate, is a basic tube amplifier built around actual Russian military surplus 6П14П (6P14P) tubes, and a Chinese SMPS that is at least theoretically made specifically for tube power amplifiers. Here is a picture of the amplifier during a recent "glow test". While it looks pretty complete, nothing is wired except the tube heaters. The area that looks like a window or display will house an LED VU meter. I have discussed the particular power supply used in this project on my "Modern Power for Tube Projects?" thread on AudioKarma, and I will not reproduce it here. The unit in question can be found on sites such as AliExpress by searching for "tube amplifier switching power supply". This is the 250W version. The short version is that the SMPS will produce the appropriate voltages for a modest tube power amplifier, but is struggles to power the heaters of these 4 power tubes, and since the feedbacks of all of the outputs collectively feed the drive (primary) of the SMPS, it will not produce the correct voltage unless all outputs are loaded appropriately. In order to take the picture above, I had to use a 1.5K ohm power resistor to load the B+ (300V) output. In reviews on AliExpress, others have mentioned that the transformer at the center of the SMPS gets very hot with even a moderate load. At least in theory, this power supply should have some benefits for someone looking to build a small tube amp project on a budget. The SMPS itself sells for about $40-$45 (not counting shipping), and has the advantage of operating from 100 - 240VAC. That means that your project will not only work anyplace in the world, but it should have consistent behavior even if the line voltage changes. So While at this time, I cannot recommend this power supply, the build shall go on. I plan to work at a very leisurely "hobby" pace, so I wouldn't recommend compulsively reloading this page looking for an update. I also have a couple other Tube Projects going on. You can Read about a larger, more powerful SMPS 7591 Tube Amplifier build here, and Read about a concept for the "Does Everything" Tube Table Radio" in this thread. (Links to be added soon).
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3	Original Projects and Builds / Other Builds and Projects / Re: Malachite DSP - SDR Radio Receiver on: Jan 18^th, 2021, 6:56am
Started by Administrator \| Post by Rod
Thanks for the great information you have shared. Using the above information, I was able to upgrade from (the supplied) 1.0c to 1.10a. It's a great little device, and getting better with firmware upgrades.
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4	Original Projects and Builds / Other Builds and Projects / Re: Malachite DSP - SDR Radio Receiver on: Jan 17^th, 2021, 3:22pm
Started by Administrator \| Post by Administrator
Firmware 1_10a Quick Look report. Refer to the Change Log. Observations: There is not a setting for the sensitivity of the encoder wheels as previously reported. That was based on a miss-reading of the translated Russian in the change log. Other than putting the encoder wheel direction options on a single button, there is no noticeable change in encoder operation. I have no idea what the Note referring to "wheelbarrow" is supposed to mean. The Auto Scan feature for FM tuning would be a great idea, except it doesn't work. We have many strong stations in the area, but in trying with both a whip antenna and my outside wire antenna, numerous scans found exactly zero stations. There is now a function to change the color of the FM "Retro" scale. It's nicely implemented with little "preview" icons. I'm not sure if that was in 1_0f or not. The bandwidth shadow now reflects the currently set audio bandwidth. I don't remember this working before, but I may have just not noticed it in previous firmwares. Yes the spelling of "Standard" is correct, but with the nomenclature as-is, it is still not going to be intuitive as to what that setting does without reading it in the manual. They have improved the nomenclature for some of the RF Gain Settings in the "HARD" menu. There is a PREAMP Enabled/Disabled setting, and a PRE Gain setting. Does the PRE Grain setting adjust the gain of the Preamp? if so (as one would think), then why are those 2 settings not near one another? One of the Gain settings (the one closest to the Preamp button) has been changed to "ATT", but I am still confused. Does the Preamp attenuate the signal?! Maybe I need to read (translate) an updated manual, but it is still far from user-friendly. The HARD menu should be updated so that the order of the functions having to do with RF gains/attenuation follow the flow of the signal left to right. The other buttons should be moved to accommodate this. A picture is worth 1000 words, so here is a picture that shows the concept of what I am thinking of. Note that this is a 5 minute drawing for illustration only, not the exact implementation. I tried to be consistent in capitalization (Ahem), and to suggest alternative nomenclature in some places. I did not refer to the schematic or MSI001 datasheet while making this drawing. Blocks may not be in the right order. The signal path line could be animated to show the Preamp being in the circuit or not, Alternatively, a red "X" could simply be drawn to show the path that is not active. What is important is the button order. The signal path line would be completely optional.
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5	Original Projects and Builds / Other Builds and Projects / Re: Poor Man's version of the Monster GO DJ on: Jan 17^th, 2021, 1:57pm
Started by Administrator \| Post by Administrator
The folks that run the local True Value Hardware Car Shows continue to hire me to DJ, and I continue to bring my PM GO DJ as a "Back UP". I am also bringing a Samson L1200 Professional Mixing Console. Yeah, that's overkill for a neighborhood Car Show, but in addition to being able to use more than one microphone, I can also have the PM GO DJ and the Stanton SCS.4DJ connected simultaneously. This gives me 4 player decks, as well as the other features (such as Bluetooth) of the PM GO DJ without switching or downtime. In fact I find myself using my PM GO DJ more than the Stanton SCS.4DJ. This isn't a conscious decision just so I can use the device I designed and built. I really find myself naturally or subconsciously gravitating back to the PM GO DJ. There are a few reasons for this: -- The larger text on the player modules that comprise the PM GO DJ. I'm not a young DJ. I can read the small text on the Stanton, but having the larger text on 2 separate screens is much easier for me. -- I don't have to continuously switch between the "Waveform" display and the "Browse" screen like I do on the Stanton. I actually think it is about the same number of button presses to cue up the next track, but on the PM GO DJ it's all on the same screen. That makes it ergonomically easier. -- As previously mentioned, the Chinese media players are very quick at moving through the tracks. The Stanton skips, and does not scroll smoothly. Lastly, I'm beginning to think that my PM GO DJ actually sounds better than the Stanton SCS.4DJ. Yeah, OK -- I know the response to that. I'm not an un-biased, or objective observer here. It could be totally opposite. Also, I generally connect the the PM GO DJ to 2 channels of the Samson mixer, and the Stanton to the "CD/Tape" input. All of the EQ controls for the 2 channels are set to null, and the pans are set so that each channel is properly mixed by the Samson, but it's possible that the Samson just does not have as good a quality components on the CD/Tape input as it does on the actual mixer channels. Obviously more objective testing (and a far more objective tester) would be needed to determine if there really is a perceptible difference one way or the other. A few more notes on this: ~~The PM GO DJ players will play FLAC files,~~ which the Stanton will not. Using High quality FLAC files will make a difference in the sound as compared to an MP3. Objective or otherwise that is an objective fact. ~~However, very few of the files loaded onto the PM GO DJ's SD cards are FLAC. 90+ percent of them are the identical MP3 files loaded onto the Stanton.~~ Actually none of them are FLAC. I attempted to load some FLAC files, and they would not show up in the Media Players. As of right now, I don't think this actually will play FLAC files. It may still play other lossless formats such as WAV. Another Edit: Sorry to keep changing the story on this, but here is the issue: The Chinese Media Players will play FLAC files. However, the players are limited to 24 bit samples. The FLAC files I was attempting to play were 32 bits/sample. They would probably work fine if I used ffmpeg to reduce the depth to 24 bits/sample, but of course that would probably "hurt" the file (reduce fidelity) almost as much as just re-encoding it as a high bit rate MP3. It's also an objective fact that there is a lot more digital circuitry on the Stanton between the digital source files, and the output jacks. I'm not sure if the Stanton implements it's tone control in a DSP environment, or with analog components. I can tell you that I don't remember seeing groups on OP amps and analog circuitry. I also know that the Stanton is very slow at scrolling, scanning media, etc. It seems very limited on computing power for the job at hand. If the Stanton is trying to do a lot of real time signal processing on a system that seems to be somewhat limited, then it is very likely that my PM GO DJ really does sound better.
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6	Original Projects and Builds / Other Builds and Projects / Re: Malachite DSP - SDR Radio Receiver on: Jan 13^th, 2021, 5:46pm
Started by Administrator \| Post by Administrator
There is a new firmware out, and George and the other developers are listening! FW 1.10a is available at the usual location. Be sure to check the Change Log (Contains both Russian and English). I won't have time to load this firmware for several days, but it seems like they continue to improve the Malachite SDR, and have fixed more of the issues that I mentioned in my "Bugs and Criticisms" List (Post #8 and Post #9 of this thread.) I won't post the change log here, but among the updates are fixes/improvements to some of the things I have mentioned: -- Spelling of the word "Standard" in the HARDware menu. -- Settings for the sensitivity of the encoders. There is also a new Splash screen, and updates in the "Retro" Broadcast FM display for auto search, and easier moving between stations. If you have tried FW_1_10a, and would like to comment, please register by emailing "john" at this domain, and I will create an account for you.
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7	Linuxslate.com Reviews & Commentary / Review Discussions / Re: IdealRatio Rodnik 3 Portable Radiation Detecto on: Dec 30^th, 2020, 11:04am
Started by Administrator \| Post by Administrator
Here's another "Have I Found Anything Radioactive?" I did: In this picture, my IdealRatio Rodnik 3 is showing approximately 50x background a few centimeters from a rather unremarkable looking rock. Based on a (very) little research I did while writing this post, I believe this may be a specimen of coffinite. Before you ask why I would own something that is highly radioactive, and with a name that has a close association with death, I should mention that coffinite is named after American geologist Reuben Clare Coffin. The name of the mineral is just a coincidence of a rather unfortunate last name. While coffinite does contain uranium, the name was not meant to portray this mineral as any more or less dangerous than any other naturally occurring mineral that contains radioactive elements. The assumption that the stone in the picture is coffinite is based on pictures from a Google Images search that seem to show similar grayish rocks with traces of yellow crystals. In addition, coffinite is the 2nd most prevalent uranium-containing mineral, so simple statistics show good odds that it is in fact coffinite. So how did I come to posses this bit of hyperactive nature? I would have never found this stone without my IdealRatio Rodnik 3. I was at my local flea market. There are 2 vendors there that specifically sell crystals, stones and minerals, but this rock didn't come from them. I did buy a piece of tumbled green apatite from the larger vendor. I learned that green apatite seems to generally be more radioactive than blue apatite. I also purchased a tumbled malachite stone - not for it's radioactivity (it isn't radioactive), but for the name association with another project covered here on Linuxslate.com. Having passed the crystal/stone vendors, and in fact reached the very end of the market, I came across a man with several full tables of random rocks, as well as quite a lot of abalone shells. I don't remember if it was something the seller said, a sign or label, or just the general look of the various rocks, but I got the impression that the rocks were from the Western United States. I waved my Rodnik 3 over the boxes, and it gave a flew clicks over a specific corner of one box. Of course random events of cosmic or local nature can cause a momentary jump in counts, so I waived the counter over the same area again, and again it reacted. I picked up some rocks in that part of the box, but when held away from the box, my Rodnik 3 began to decrease back toward a normal background reading. With some of the rocks moved away, I again held the Rodnik 3 over the box. It began a steady stream of beeps followed almost immediately by the alarm mode. Something in the box was "hot", and the other rocks had basically been shielding it. So you basically know the full story. The source of the radioactivity was the small stone pictured above. I paid the man $3 and took my rock home with me (but not in my pocket.) If I see the same vendor again, I will ask him if he knows any more about were the rocks came from.
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8	Original Projects and Builds / Other Builds and Projects / Re: Malachite DSP - SDR Radio Receiver on: Dec 5^th, 2020, 12:08pm
Started by Administrator \| Post by Administrator
Firmware 1_0f Update and Quick Look report. My Malachite DSP SDR Radio is in it's new case. I like the style and layout of my new case very much. Unfortunately, I had a lot of stupid mistakes while making it, and the paint didn't come out as nicely as I would like, but it is functional. Even when compared to the factory built (Chinese) unit I had, mine is more functional, and very nice to hold and use. In addition to the new case, a firmware update has also helped make mine far more functional. I have to say it directly: The Malachite SDR has never been better. Loading FW_1_0f As of this writing, FW_1_0f is only available as a .hex file. I used the official STM DfuSe v3.0.6 Demo DfuFileMgr.exe under WINE to convert the .hex file to .dfu. Yes, there are Linux utilities that will do this, but using DfuFileManager was a quick, easy, GUI way to do it. After that, I installed the DFU file as described in Reply #4 of this thread. Quick Look Review of FW_1_0f Here's a few quick observations after playing with FW_1_0f for just a few minutes: They have removed the press 3 times to turn on function of the STBY/Wake switch. Even a quick press of the button will turn on the radio. I think a long press is the correct answer (like almost everything else) but for now, we are back to a quick press. It still must be long pressed to turn off the radio. I like the new "Retro Look" tuning dial for the FM broadcast band (Shown Below). This display replaces one of the WB FM Mux spectrum displays. It makes the radio much more user friendly for just casual FM tuning/listening. Some of the "Ghost" signals/interference is gone. While in just the few minutes I played with it, I cannot say that all of the phantom interference and reflections are gone, it seems to be a significant improvement. The Radio is now far more useful for general listening. Note that this was my first and most significant complaint, and I will amend my bug list in Reply #8. My first complaint on my 2nd page of bugs was about scratchy sounding squelch. It may be a by product of fixing the above, but it seems that there is some improvement. Various other fixes as mentioned in the Change Log. New Retro Look FM Tuning scale
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9	Original Projects and Builds / Other Builds and Projects / Re: Malachite DSP - SDR Radio Receiver on: Dec 4^th, 2020, 5:06pm
Started by Administrator \| Post by Administrator
It's been a while since I've updated this thread, but I haven't lost interest in my Malachite SDR. Here's a few Headlines: I Sold One of my Malachite DSP SDR's at the Melbourne Florida Hamfest. New Home-Made Case for my Remaining Receiver How to Add a separate Standby/Wake Switch to Chinese Malachite DSP SDR Boards New Firmware Released I Sold One of my Malachite DSP SDR's at the Melbourne Florida Hamfest. As will become obvious from the remainder of this post, the one I sold was the one that came built into a basic metal case. I currently have only the one that I originally purchased as just a bare board. New Home-Made Case for my Remaining Receiver I have built a new case for my Chinese made bare-board Malachite DSP SDR. The case I had was hastily made from a clear, brittle plastic. It was poorly designed, not very nice looking, and it was developing cracks in several locations. I have made a new one out of Lexan. Pictures and basic plans for the new case are shown below: Note: The Link to the actual plans is below. The picture above is only for reference. Note: Back Panel is not shown in the picture above. This design is much thinner than my previous case and contains a front-firing speaker. http://linuxslate.com/Malachite_Case_Design_2.pdf A few notes about the plans: 1. All measurements should be considered approximate. Measure your own board, and make dimension changes as needed. 2. The screen is extremely delicate. Do not attempt to force it into a case. I added foam weather stripping around the screen cutout. 3. Due to the layout of the Chinese boards, both the bottom (base) as well as the top (antenna) side need to be removable for board access. The drawings above are being provided as Open Source. If someone could convert them to files appropriate for a laser cutter or other automated production, it would be much appreciate. Please provide the drawings in a standard non-proprietary format. I will post them here also as Open Source, and I will credit the name or organization that converted them. Please register by sending an email to "john" at this domain, or simply attach the files. How to Add a Separate Standby/Wake Switch to Chinese Malachite DSP SDR Boards The Power/Wake/Standby button on most Chinese boards is a tiny SMT push button. Given the frequent use of this button, and the difficulty in making a homemade case that allows it to be operated in a convenient manner, it is in many cases desirable or necessary to wire up a parallel separate push button. Note: It is strongly suggested that readers reference the schematic prior to attempting the modification detailed here. The Schematic can be found at: https://yadi.sk/d/4ZgsrswxYClG1Q Select the file [Scheme, BOM.rar]. As seen in the lower left of Page 3 of the schematic, The button Is connected via a simple debounce/filter circuit from the +3.3V CPU power to the CPU Wakeup pin (Pin 7). While removing the existing SMT switch, and simply soldering leads to the original switch pads is an obvious possibility, I chose not to do this for several reasons: Desoldering/Soldering access to the original switch is made difficult by it's proximity to (almost underneath) the screen. I did not consider removing the screen due to the potential for damage. Destructively removing the switch could result in damage to the pads and lifted traces. I would like to leave the board with as little modification as possible. For my case design, it was desirable to have the leads exit from the component side of the board, not the screen side. So the best solution was to find R39, R44, and R45, as well as any close connection to the 3.3V_CPU line. In the picture below, I have circled the common point of R44 and R45. I soldered a lead to the end of R45. (Top end in picture). The smaller circle shows the +3.3V side of what I believe is C83. I soldered the other lead there. (Left end of component as shown in the picture.) I simply attached short leads to a small JST connector. The other side of the JST connector is soldered directly to the separate switch. This allows the board to be easily removed. Note: While there is no signal on the leads, it is best practice, especially in an RF device to keep any leads as short as possible. New Firmware Released I save the most important for last. Our friends over in Russia have released firmware FW_1_0f. Note that as of this post, it is released only in .hex format. He did not provide a DFU file. The release notes mention significant fixes to some of the issues I have pointed out in previous posts. Once I get my Radio installed in it's new case, I will attempt to load this version "f" firmware, and I will amend the previous posts as appropriate. As always, get the official firmware files from: https://yadi.sk/d/4ZgsrswxYClG1Q Reminder: Registration is required for all firmwares other than the test firmware. Instructions for registering can be found here: http://www.cqham.ru/forum/showthread.php?41449 (NOTE: Russian Language. Use Chrome's translate function, or other online translator.) That's all the News Headlines for now. Happy listening!
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10	Original Projects and Builds / Other Builds and Projects / Re: Poor Man's version of the Monster GO DJ on: Nov 20^th, 2020, 7:04pm
Started by Administrator \| Post by Administrator
Finally -- As promised -- The demonstration video:
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