Search found 336 matches
- Tue Apr 23, 2024 10:30 pm
- Forum: Technical Discussion
- Topic: Output Transformer formula?
- Replies: 13
- Views: 624
Re: Output Transformer formula?
load line is tangent to the 100% Pa max curve ? Help me see that. You're going to have a hard time seeing that because the JJ curve is actually for 12W instead of the 14W label. With 450V and 12W, R comes out to 16.875k so that 4.219k would be used for the class B load line. The line will run from ...
- Tue Mar 26, 2024 6:21 pm
- Forum: Technical Discussion
- Topic: Deluxe Reverb Build
- Replies: 20
- Views: 926
Re: Deluxe Reverb Build
Here is a straightened-out Concert Series schematic. There isn't really a Concert II, but everybody uses that designation because all of the other ones are "II's".
- Tue Mar 19, 2024 4:50 pm
- Forum: Technical Discussion
- Topic: Rivera-style modded Fender Modded Deluxe
- Replies: 4
- Views: 476
Re: Rivera-style modded Fender Modded Deluxe
... but what the hell are those boxes with the little plus sign? Those are VTL5C1 light dependent resistors (LDR). They have an LED and a photocell inside them. When the light from the LED hits the photocell, the resistance of the photocell plummets. VTL5C1-5C4 PerkinElmer.pdf Fender Deluxe Reverb ...
- Sat Mar 16, 2024 11:56 pm
- Forum: Technical Discussion
- Topic: Need help creating Bias Supply from HT
- Replies: 9
- Views: 590
Re: Need help creating Bias Supply from HT
Hello, I'm in the planning stage of building an amp with the foundation being the 5F6-A. I've got a great power transformer that I'm going to use, however it doesn't have a bias supply tap. I have Merlin's book on both preamps and power supplies, but I'm still struggling to understand the precise s...
- Sat Mar 16, 2024 10:51 pm
- Forum: Fender Discussion
- Topic: Can someone explain this connection
- Replies: 2
- Views: 461
Re: Can someone explain this connection
The bias is connected to the oscilator circuit. Just trying to understand what is happening here and why. Sometimes the neon lamp in the LDR unit will remain lit when the LFO stops unless you put the LDR driver tube into cut-off. If the neon lamp remains lit, the Intensity control acts like a volum...
- Wed Mar 13, 2024 10:46 pm
- Forum: Technical Discussion
- Topic: Tweedle Dee PI - LNFB and trimmer
- Replies: 38
- Views: 2303
Re: Tweedle Dee LNFB
So I built the thing and got an open loop gain of 1.824 with no regard for significant figures. Using this in the closed loop equation above, I calculated a closed loop gain of 1.766. The observed closed loop gain was 1.774, pretty close. The observed gain reduction was 1.774/1.824 = 0.973 = 0.24dB....
- Wed Mar 13, 2024 10:24 pm
- Forum: Technical Discussion
- Topic: Tweedle Dee PI - LNFB and trimmer
- Replies: 38
- Views: 2303
Re: Tweedle Dee LNFB
I'm not really following much of that, so I took off in my own direction. The cathodyne already has 50% NFB, 30.2dB of gain reduction, before the 3.3M local NFB thing. CF 11 PNG.png So I used the gain without the 3.3M local NFB as the open loop gain. I used this cheat sheet for the closed loop gain....
- Sun Mar 10, 2024 8:31 pm
- Forum: Technical Discussion
- Topic: Tweedle Dee PI - LNFB and trimmer
- Replies: 38
- Views: 2303
Re: Tweedle Dee LNFB
For the TD I'm also interested in the differential gain because I am only trying to find the equivalent input resistance, Rin. So, by taking the resistances of the plate and tail and balancing them, rendering them equal, I have a "close enough" factor I can use in the object of the exercise, which ...
- Sun Mar 10, 2024 8:05 pm
- Forum: Technical Discussion
- Topic: Tweedle Dee PI - LNFB and trimmer
- Replies: 38
- Views: 2303
Re: Tweedle Dee LNFB
Before we can determine the bootstrapped value of Rg and hence the effective input resistance ( Rin ) using the bootstrap formula below we need to find the value of the differential gain ( A ) PI equations (1) bootstrap formula.jpg The formula for differential gain takes the 'total output voltage, ...
- Sun Mar 10, 2024 4:55 pm
- Forum: Technical Discussion
- Topic: Help with circuit
- Replies: 18
- Views: 497
- Fri Mar 08, 2024 2:57 am
- Forum: Technical Discussion
- Topic: 2024 Monkeymatic Liverpool (nontraditional)
- Replies: 48
- Views: 2217
- Thu Mar 07, 2024 6:28 pm
- Forum: Technical Discussion
- Topic: 2024 Monkeymatic Liverpool (nontraditional)
- Replies: 48
- Views: 2217
Re: 2024 Monkeymatic Liverpool (nontraditional)
I had a chance to swap in an LND150 in place of 12AX7 first gain stage with no other mods in an existing build, and was happy with the results. So I'm going ahead with this Liverpool (nontraditional!) build, using LND150 as first gain stage, thereby eliminating one preamp tube. Layout first. First ...
- Tue Feb 27, 2024 8:41 pm
- Forum: Technical Discussion
- Topic: Tube effects loop
- Replies: 9
- Views: 453
Re: Tube effects loop
I guess I'd have to see your math. I used a mu of 100 and an internal anode impedance of 62.5k for the 12AX7. I used a mu of 17 and an internal anode impedance of 7.7k for the 12AU7. The external cathode resistance is 2.2k in parallel with the 10k pot for a total of 1.8k. The 1M grid leak resistor ...
- Tue Feb 27, 2024 8:38 pm
- Forum: Technical Discussion
- Topic: Tube effects loop
- Replies: 9
- Views: 453
- Fri Feb 23, 2024 10:04 pm
- Forum: Technical Discussion
- Topic: Tube effects loop
- Replies: 9
- Views: 453
Re: Tube effects loop
It's not about the gain per se. The 12DW7 optimizes the driver and recovery functions. The AX side provides high gain for the recovery signal. The AU side provides a low impedance output capable of driving the cable without high frequency loss due to cable capacitance. You might want to check my ma...