Search found 13310 matches
- Wed Apr 08, 2009 12:48 am
- Forum: Technical Discussion
- Topic: JTM45 problem
- Replies: 23
- Views: 5195
Re: JTM45 problem
So exactly what are we hearing in the clip? Given the assumed purpose of these resistors would the distinctive ripping sound be a breaking into and out of a parasitic oscillation that is triggered when the signal amplitude is high? And, why did it not occur previously? Do the inter-electrode capacit...
- Sun Apr 05, 2009 6:01 pm
- Forum: Dumble Discussion
- Topic: Etching a board set for my HRM build...
- Replies: 49
- Views: 5229
Re: Etching a board set for my HRM build...
Great, thanks! Where does the test point connect to?
MPM
MPM
- Sun Apr 05, 2009 9:19 am
- Forum: Dumble Discussion
- Topic: Etching a board set for my HRM build...
- Replies: 49
- Views: 5229
Re: Etching a board set for my HRM build...
ic, I doubt that it's because nobody looked... I made copies and (virtually) populated them with parts to figure them out. It all made perfect sense to me. It would be great to see the HRM board annotated if you don't mind posting it. I'm not focused on HRM amps just now, but I'm interested in the e...
- Sat Apr 04, 2009 1:03 pm
- Forum: Technical Discussion
- Topic: capacitor value question
- Replies: 10
- Views: 1782
Re: capacitor value question
Bypassing the cathode resistor increases the stage gain, typically about 5-6 dB. It creates a shelving effect where a transition from the un-bypassed gain to the higher bypassed gain occurs over about a decade (a factor of 10 in frequency). The value chosen determines the frequency range over which ...
- Sun Mar 29, 2009 3:20 pm
- Forum: Garage Talk
- Topic: Fender AB763 Tremolux caper
- Replies: 12
- Views: 5453
Re: Fender AB763 Tremolux caper
A kit is also nice but, you'd miss on the smell... Tell me about it! I love the smell when I open up my 67 Deluxe Reverb. Glad I'm not the only one. :D Not by a long shot, I'm sure. A while ago I was at the local Guitar store with my son and pointed out a '59 5E3, saying that it was probably a grea...
- Sun Mar 29, 2009 2:19 pm
- Forum: Technical Discussion
- Topic: Schematic and parts list for DC heater supply?
- Replies: 131
- Views: 22829
Re: Schematic and parts list for DC heater supply?
Also, the cap looks like it is sitting between the two heater lines, whereas in my head I was thinking that the + from the cap would go to the heaters, and the - would head to ground. This is different than what I've seen... The cap is across the 6.3V on the heaters because you need a store of char...
- Sat Mar 28, 2009 9:40 pm
- Forum: Technical Discussion
- Topic: Schematic and parts list for DC heater supply?
- Replies: 131
- Views: 22829
Re: Schematic and parts list for DC heater supply?
Here's another incarnation; this one is from the Marshall 4001 Studio 15. I have an '88 4001, so I can say that it works fine and has held up well.
MPM
MPM
- Thu Mar 26, 2009 11:31 am
- Forum: Technical Discussion
- Topic: Substitute for 6SC7 in preamp?
- Replies: 2
- Views: 11188
Re: Substitute for 6SC7 in preamp?
Info here: http://thetubestore.com/earfenam.html I just Googled 6SC7 substitute. The chance of finding something with the same pin-out looks slim, but since it's a homebrew, you could rewire it to use another type. 6SL7 is a replacement (with rewiring) but you are looking for more than that... check...
- Wed Mar 18, 2009 8:29 pm
- Forum: Technical Discussion
- Topic: Load Line, Q-Point, and Frequency Response in Excel
- Replies: 44
- Views: 14477
Re: Load Line, Q-Point, and Frequency Response in Excel
You only have to provide the anode characteristics data table (plate curves), by digitizing the plot from the data sheet for the tube you want to add. You will want to put this data into one of the blank “cust” (custom) areas on the device library sheet so that it will be accessible by clicking the ...
- Wed Mar 18, 2009 12:01 pm
- Forum: Technical Discussion
- Topic: How to calculate voltage drop
- Replies: 17
- Views: 6559
Re: How to calculate voltage drop
This is the graph, with the three cases plotted. I picked a cathode resistor of 1.7K because that matched the Va (plate voltage) of the first case, then held it constant. The intersection of the cathode load line (purple) with the anode load lines defines the idle points. Note that the plate voltage...
- Wed Mar 18, 2009 2:26 am
- Forum: Technical Discussion
- Topic: How to calculate voltage drop
- Replies: 17
- Views: 6559
Re: How to calculate voltage drop
That's fine for the example case where the voltage drop across the plate resistor and the resistance are both known. The second part of the question was: what happens if you change the value of the resistor? You know the current for the example case, but with a different value for the plate load res...
- Tue Mar 10, 2009 5:34 am
- Forum: Garage Talk
- Topic: www.valvewizard.co.uk
- Replies: 16
- Views: 5476
- Tue Mar 10, 2009 1:19 am
- Forum: Technical Discussion
- Topic: Gas fueled tubes
- Replies: 6
- Views: 1211
Re: Gas fueled tubes
Thanks for the explanation, Wayne. I don't know much about it, but I think with only 4 characters in his call sign, this cat has been around a while.
MPM
MPM
- Tue Mar 10, 2009 1:00 am
- Forum: Dumble Discussion
- Topic: Equivalent for NTE 452
- Replies: 22
- Views: 4507
Re: Equivalent for NTE 452
Naw, the idea is a good one but the d-pre is not a great bit of engineering. I really like what adding 10 to 15dB of gain on the front end does for single pickups. The second sucky side of it is a phase inversion, but that is fixable as well. What is the disadvantage of the phase inversion? Seems l...
- Sun Mar 08, 2009 3:34 pm
- Forum: Technical Discussion
- Topic: Gas fueled tubes
- Replies: 6
- Views: 1211
Re: Gas fueled tubes
that guys got to much time on his hands..is the flame just taking the place of the heater then? and no vacuum obviously Cute. The cathode is heated by the flame, so the flame is doing the job of the heater, and since a visible flame is ionized gas, that must be allowing electron flow and substituti...