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  1. linuxslate

    LG Dukebox

    I don't see a thread for this, so I figured I'd start one. Apparently, LG is going to introduce a Vacuum Tube smart speaker at CES (Consumer Electronics Show) next week. The device is reported to actually have "Tube Audio". Quoting the linked Engadget article: "Neither the DukeBox or the...
  2. linuxslate

    Cerwin Vega E-712 Fix

    Since at least someone else has these speakers, I'll post an update on mine: A few days ago, I powered on my Home Made 7591 tube amp. It sounded really flat - I immediately knew something was wrong, so (after panicking) I realized that it was the left speaker that sounded flat. -- Same as...
  3. linuxslate

    Magnavox 8802 Very Low Volume

    The resistor mentioned in post #37 should be replaced, not just soldered. If it is "butt soldered" (just pushed toward the terminal and solder applied) it will be subject to cracking. Thermal changes, vibration, etc. will eventually break the joint. A tube amp at rest -- Isn't. If the broken...
  4. linuxslate

    Cerwin Vega E-712 Fix

    Apparently, this place is not exactly teaming with CV fans. Since I didn't get a response, I had to go with what I know (or think I know). As mentioned, I did not like the cheap electrolytics on the original CV crossover boards. Also, trying to replace all/most of those electrolytics...
  5. linuxslate

    Cerwin Vega E-712 Fix

    Bumping a 10 Year old thread, but I am looking for some advice. I purchased a pair of CV E-712 speakers in relatively good condition (or so I thought). I also got a CV center channel speaker that I do not plan on using at the moment. They all look good. Foam is good. No tears, dryness, etc...
  6. linuxslate

    6EU7 Grid to ground resistor

    I know less now than I did a few minutes ago. I was recently working with exactly this -- the input of a Maggie 9304, and I also noticed the choice of 470K. I considered changing them to 1M, but in the end, I decided that there was no practical difference. This is how I used to think of it...
  7. linuxslate

    Can you see what's wrong with this amp?

    ...And I thought I was being Cheesy because I put green LED's in the HV cage of my latest build. There is a lot to be said for the "looks" factor in peoples renewed interest in tube amplifiers. It's a lot like the interest in "restomod" or retro-look vehicles. People don't buy the new Ford...
  8. linuxslate

    Power supply breadboarding

    As @spantou01 mentions, a load to simulate a tube power amp ends up needing to disapate a lot of power. Of course you can use massive power resistors (probably attached to a heat sink), but this can get expensive. I design and build Switch Mode Power Supplies for tube power amplifiers. To...
  9. linuxslate

    Sold Good Amp, Bought Ugly Amp. What Do I Build?

    I changed the value of R3 to 2700 ohms, and made sure both channels have the same value components. I also installed the feedback caps (C10 -- value as shown), and decided to button it up for now. Here are the official "Glamor Shots" of this project: It generally sounds great and has...
  10. linuxslate

    Simpson 1000 tube tester?

    Just another note about the Simpson 1000. The tube list seems horribly inaccurate. There are significant differences between various versions, and all of them have mistakes/differences even in very common tubes such as the 12AX7. The roll I got with mine is dated November 1960, and has...
  11. linuxslate

    The Transistor

    "In terms of the total number of transistors in existence, it has been estimated that a total of 13 sextillion (1.3×1022) transistors have been manufactured worldwide between 1960 and 2018." -- Wikipeidia -- https://en.wikipedia.org/wiki/Transistor_count - Last paragraph in the section at the...
  12. linuxslate

    Ukraine 6P14P’s finally came!

    The numbers probably refer to plate current and gain (gm?) as measured on the old Soviet L3-1 or L3-3 tube tester. As long as your Eico HF-81 is in reasonable operating condition, you should not have to worry about bias, as the Eico HF-81 is cathode biased, which is sometimes called "automatic...
  13. linuxslate

    Sold Good Amp, Bought Ugly Amp. What Do I Build?

    It's been a while since I shared an update on this project. Lots of other things I'm playing with here, including other tube amp projects, and 2 tube testers that I've at least fixed, if not restored. First, here is a picture of the back panel -- just because I haven't shared this yet, and...
  14. linuxslate

    Simpson 1000 tube tester?

    Old thread (only 13 years), but I just got a Simpson 1000 from a "Certain Popular Auction Site". Bumping it here so that AK has "One stop shopping" for info/discussion of this tube tester. I bought it because of the brand name, and the fact that it does do more than just a regular cathode...
  15. linuxslate

    This used to be an HH Scott Stereomaster 345 Receiver

    There is some awesome iron in that thing. Good 2nd life for it. Nicely done.
  16. linuxslate

    SCOPE INTERPRETATION HELP

    It would be unusual for a resistor to change in value from 53k to 83k. Also, The polarity of the meter is going to matter due to the presence of semiconductors. You can lift a leg to check it (usual warnings about possible PCB damage apply) Checking some of the voltages in the area would...
  17. linuxslate

    SCOPE INTERPRETATION HELP

    Somebody is probably going to correct that -- Phase adjust? -- but if each channel is not set up correctly, the result could still be the same -- a difference in power between channels.
  18. linuxslate

    SCOPE INTERPRETATION HELP

    We can't tell much from those pictures. It could be 2 identical sine waves offset slightly from one another, or it could be 2 since waves of different amplitudes. Since you mention balance and volume, I assume that the original problem was a balance issue, or difference in volume between the...
  19. linuxslate

    DIY tube amp...troubleshooting sparking rectifier tube

    Making sure you have a valid power supply before you ask it to supply power to anything is a good troubleshooting plan. Also make sure all capacitors are rated high enough for the voltage they will see. Those 300B's run a lot of voltage, and need very high rated capacitors. If you do as...
  20. linuxslate

    Velleman k8098 audio analyzer kit?

    Scrap above project. I was planning on using Metal film resistors (The things in a TO-220 case, but missing a leg). I have since read that these devices are easily blown by transient loads. Even though what I was planning would have been rated at 60W, and I was only planning on using it with...
  21. linuxslate

    Velleman k8098 audio analyzer kit?

    I picked one of these up someplace -- To be honest, I cannot even remember where. I think I got it from a vendor at the "Worlds Longest Yard Sale" a few years ago. I'll also be honest in that I had no idea what it was when I bought it. I just knew it had something to do with audio, and it had...
  22. linuxslate

    Tube amp topologies

    It is correct that most (I would say all contemporary) solid state amps don't have output transformers, but generally speaking, the voltages involved in solid state amps are low, and there is no reasonable failure of a SS amp that is going to put lethal voltages on the speaker terminals (or any...
  23. linuxslate

    Sold Good Amp, Bought Ugly Amp. What Do I Build?

    I didn't think of that at all --- These just happened to appear in my parts bins. . I was actually thinking of 6P3S-E (6П3С-Е)'s. Maybe a big box with 4 of them per channel, basically a P-P-P version of the referenced RCA schematic. I'm now confident that I can make an SMPS that can provide...
  24. linuxslate

    Sold Good Amp, Bought Ugly Amp. What Do I Build?

    Engineering is always a compromise. I don't like compromise. ...So I compromised. I didn't feel that the change from 200K to 220K would make a lot of difference on the load on the PI; But going to 270K worried me, especially with my experience with (used) 7591 family tubes. 240K is also a...
  25. linuxslate

    Superior Instruments TD-55 Tube Tester

    I said I would post updates on this Tube Tester (Superior Instruments TD-55) Just a note for safety. As mentioned, this tube tester does not have an isolation transformer. This means that the Top Cap clip is by default connected to one side of the AC plug. Given that the plug is not...
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