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deafbykhorns

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  1. Depends on listening levels if no more than 10 watts needed, go SET, if you like concert levels, get a good PP amp with EL34s, 6L6 or KT88
  2. Try a 26 or a 01A preamp fpr some real magic
  3. I have a pair of these, been sitting in the closet for 10yrs....
  4. Download LTSpice and start reading and studying other schematic topologiesIf interested, I can give you a Dropbox link to all the support files I've gathered the past year. I had similar equipment you have 10-15yrs ago. Once you figure out how to build a $10,000 amp for a fifth of the price you'll be hooked. I built an amp that has more features than most production amps which will drive up the cost but well worth the $$$ since it will outperform these amps (if executed properly).
  5. That was the idea and focuses more on the glowing tubes. The copper plate gm70's look really sweet
  6. Almost 12 months to design, gather parts and build a high voltage amp. Trust me, I learned manufacturers earn every penny! This is my third scratch build and consists of a 76-300B-GM70 IT coupled driver for A1 to about 22 watts and A2 to about 40 watts 400v and 1200v supplies which is more than enough to kill Coleman filament supplies Custom chassis from Landfall Systems Arduino control for monitoring, soft start and standby Sounds like a gigantic 300B amp on my Khorns Pure SET magic with no feedback
  7. Wasn't audiogon sold because it wasn't making a profit? They try to make a percentage but there's ways around that It's still better than EBay and not a bunch of craigslist flippers using magic markers on scratches
  8. Looking for a pair of these, hopefully someone has a pair laying around 16 ohm preferred
  9. What do you think, this is a quick Sim of something I had in mind
  10. Your heat sinks getting hot are the transistors biasing on, thats a problem See below definition of taper Resistance–position relationship: "taper" Size scaled 10k and 100k pots that combine traditional mountings and knob shafts with newer and smaller electrical assemblies. Note the "B" designating a linear taper. The relationship between slider position and resistance, known as the "taper" or "law", is controlled by the manufacturer. In principle any relationship is possible, but for most purposes linear or logarithmic (aka "audio taper") potentiometers are sufficient. A letter code may be used to identify which taper is used, but the letter code definitions are not standardized. Newer potentiometers will usually be marked with an 'A' for logarithmic taper or a 'B' for linear taper. Older potentiometers may be marked with an 'A' for linear taper, a 'C' for logarithmic taper or an 'F' for anti-logarithmic taper. The code used also varies between different manufacturers. When a percentage is referenced with a non-linear taper, it relates to the resistance value at the midpoint of the shaft rotation. A 10% log taper would therefore measure 10% of the total resistance at the midpoint of the rotation; i.e. 10% log taper on a 10K ohm potentiometer would yield 1K at the midpoint. The higher the percentage the steeper the log curve Linear taper potentiometer A linear taper potentiometer (linear describes the electrical characteristic of the device, not the geometry of the resistive element) has a resistive element of constant cross-section, resulting in a device where the resistance between the contact (wiper) and one end terminal is proportional to the distance between them. Linear taper potentiometers are used when the division ratio of the potentiometer must be proportional to the angle of shaft rotation (or slider position), for example, controls used for adjusting the centering of the display on an analog cathode-ray oscilloscope. Precision potentiometers have an accurate relationship between resistance and slider position. Logarithmic potentiometer A logarithmic taper potentiometer has a resistive element that either 'tapers' in from one end to the other, or is made from a material whose resistivity varies from one end to the other. This results in a device where output voltage is a logarithmic function of the slider position. Most (cheaper) "log" potentiometers are not accurately logarithmic, but use two regions of different resistance (but constant resistivity) to approximate a logarithmic law. The two resistive tracks overlap at approximately 50% of the potentiometer rotation; this gives a stepwise logarithmic taper. A logarithmic potentiometer can also be simulated (not very accurately) with a linear one and an external resistor. True logarithmic potentiometers are significantly more expensive. Logarithmic taper potentiometers are often used in connection with audio amplifiers as human perception of audio volume is logarithmic.
  11. Change the horns and use a JBL 2404 tweeter, make the crossover mod your last choice. The horn/tweeter will be more dramatic than just the crossover/tweeter. I almost sold my Khorns before doing this mod (i did the crossover mod first)
  12. Bingo! I use a 1-1/2 amp quick blow and change it out to 4 or 5 for the "burn in" test (depending on the amp). "To each his own", I guess its not that much different than changing out light bulbs...... Duder- Back to the subject, what did you find?
  13. Ok, you win, the topology of those amps need a current limiter...... I should of said "most amps"....a variac is still a valuable tool for me. BTW, I have repaired many M and PM series Carvers and who the heck uses a DC300? I used my last one as a boat anchor. There's a reason why they call it "DC" in the 300 if you know what I mean.
  14. Your dead wrong.....a variac has many uses and is overall a better way to monitor things assuming you had one with a meter. You also have an inrush of current with a cold bulb (lower resistance).It's simply a poor mans variac and for the novice or occasional trouble shooters.
  15. Like you, I'm self taught in repairs, I started 30 years ago and now scratch building tube amps. You'll hit many bumps in the road but will learn quickly. Buy yourself a variac too, it will save you from burning up new parts. Especially with setting bias
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