Recent content by tekuhn

  1. tekuhn

    Introducing the Gillespie W-5M

    I completed the change on one of the amps tonight. I haven't tested yet to make sure it's still quiet, but will tomorrow. I did connect the audio ground to the chassis ground using a "loop breaker" circuit which consists of a 10Ω 5W resistor, two 1N5401 diodes, and a .1uF capacitor - all in...
  2. tekuhn

    Fisher 400 toggle switch options

    I used these from Switchcraft. They fit perfectly, but the slide is slightly shorter, so it doesn't protrude through the faceplate as far. It is also black and not burgundy like originals. I seriously thought about cutting the face of the slide off of the originals and splicing them on to the...
  3. tekuhn

    Introducing the Gillespie W-5M

    So, I've been thinking about your statement, and I'm considering doing this for at least a couple of reasons. I am finding that I really dislike the non-detachable cord, no matter how cool I think the black/white cloth covering looks. I also did some RTA frequency scans of one of the amps last...
  4. tekuhn

    Determining pre-amp tube operating points

    I totally get that, unfortunately, I find very little for the WE 396A dual triode. I'm feeling pretty good about the process now, so I think I will just wire something up and see how it sounds.
  5. tekuhn

    Determining pre-amp tube operating points

    Thank you both - that's helps.
  6. tekuhn

    Determining pre-amp tube operating points

    I've read that in calculating total plate circuit resistance, that you include the value of the external plate load resistor as if it was in parallel with the internal plate resistance provided by the charts. I don't understand that because it certainly appears to be in series with it. I'm a...
  7. tekuhn

    Determining pre-amp tube operating points

    Tom, you might find this interesting. My wife and I were browsing a local antique/junk store this weekend, and I noticed a test meter of some sort on the shelf. As soon as I saw Burr-Brown on it, I know I was going to buy it - and it was cheap to top it all off. It has 6 "D" batteries in it and...
  8. tekuhn

    Determining pre-amp tube operating points

    Thank you for that! So, I need to determine how much gain I need, and then calculate the B+ and plate resistor needed to achieve that gain at the desired quiescient plate voltage. I need to choose a cathode resistor that will achieve a positive cathode voltage sufficient enough that will allow...
  9. tekuhn

    Determining pre-amp tube operating points

    I understand how to look at tube performance charts and find a good operating point within the linear portion of the curve, but what are the best practices when it comes to B+ and plate load resistor? For example, a higher B+ and larger resistance, or a lower B+ and a lower resistance can...
  10. tekuhn

    Amplifier Performance Testing

    I guess my main concern was that if the DUT was not loaded in the same way it would be in actual use, that such measurements might not reflect the way it will actually perform. I can see that it would be easy enough to load the output of a preamp with a 50K (or whatever is appropriate) resistor...
  11. tekuhn

    Amplifier Performance Testing

    Looking at the pro-audio USB music interfaces, many of them have combination inputs that will accept an XLR mic level signal or 1/4" TRS. On the 1/4" input, some have switchable impedance of >1MΩ +, for direct instrument level signals or ~40K-60KΩ for normal line level signals. Some are strictly...
  12. tekuhn

    Amplifier Performance Testing

    I had an internal EMU-1212M which is based on the 0404 card. It was very good, but I couldn't get streaming music to play with it at higher resolutions.
  13. tekuhn

    Amplifier Performance Testing

    Thank you - not having any issues with hardware or software, I was just hoping to find a nice summary of USB interfaces showing performance data and optimum configurations, etc.
  14. tekuhn

    Amplifier Performance Testing

    @trobbins - Are you aware of any threads that summarize the process of using REW for testing any better (more concisely) than the one I posted above? It does seem to ramble a bit. I am thinking of buying an external USB DAC/sound card so that I can use a laptop. It seems like most of what's...
  15. tekuhn

    Amplifier Performance Testing

    I found this thread on DiyAudio that looks informative - 63 pages long :biggrin:. That should keep me busy for a while. https://www.diyaudio.com/community/threads/howto-distortion-measurements-with-rew.338511/
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