The active loading looks like the following. The first top triode and second bottom triode could be replaced by resistors or CCS like 10M45 from IXYS...
The autobiasing is done with an AB-4 from Pavel -> Module AB-4 for 4 tubes, PP & PPP amps, requires 6.3VAC & bias supply from the amps circuit, with TTL error signal output. TES
The autobiasing is done with an AB-4 from Pavel -> Module AB-4 for 4 tubes, PP & PPP amps, requires 6.3VAC & bias supply from the amps circuit, with TTL error signal output. TES
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Thanks! I may well go down this autobiasing route too. Interesting to see how you use the TTL error signal.
How are you using the stacked toroids?
Meh. The whole thing should draw around 200W if it's all turned on... 60W of which is to light up the tubes...
The power section is switchable, so it an be used as a line stage only, and the phono stage will only light up when it's set to phono to save the tubes/electric power. I'm only going to switch power to the heaters of the phono stage, the B+ will be always present.
I've started wiring the heaters up...
The power section is switchable, so it an be used as a line stage only, and the phono stage will only light up when it's set to phono to save the tubes/electric power. I'm only going to switch power to the heaters of the phono stage, the B+ will be always present.
I've started wiring the heaters up...
I've been using this... Works fine @70c with no ventilation, too 
AC-DC 100-240V to 36V 5A 180W 50/60HZ Power Supply Switching Board Modul I2 | eBay
AC-DC 100-240V to 36V 5A 180W 50/60HZ Power Supply Switching Board Modul I2 | eBay
I have a very similar unit which was made for 24 volts. I was using it for the power source, and battery charger in a portable PC that I made. It got uncomfortably hot when charging the batteries and running the PC at a medium workload. There were a total of 14 X 18650 lithium ion battery cells in the computer, which could turn into a small bomb if the power supply malfunctioned so I replaced it with a "medical grade" unit rated for 180 watts. It did run considerably cooler, but cost nearly $100 VS the $20 unit it replaced......I live in a wood house. I call it an insurance policy.
The unit I pulled out will wind up running some 26LW6's or 25DN6's. I haven't decided which yet. I will build a PSE amp running around 30 WPC. That's a pair of 26LW6's per channel, or probably 4 X 25DN6's. The 26LW6's cost me about $10 each some time ago, and I only have a few. The 25DN6's were $55 for 120 of them. I can afford to blow up a lot of them.
The unit I pulled out will wind up running some 26LW6's or 25DN6's. I haven't decided which yet. I will build a PSE amp running around 30 WPC. That's a pair of 26LW6's per channel, or probably 4 X 25DN6's. The 26LW6's cost me about $10 each some time ago, and I only have a few. The 25DN6's were $55 for 120 of them. I can afford to blow up a lot of them.
Years ago I did a six channel amplifier for home theatre use with 6AS7G(6N13S) outputs, and 6SL7(6N9S) volt-amp/concertina front ends. I had (total) 6 watts in the front end heaters, 2 watts in front end plate current, 5 watts in gas tube shunt regulation for the front end, 95 watts in output heaters, and 120 watts in output plate current. 228 watts dissipation for six channels of tube power, at 7~8 watts output per channel. That amplifier felt like a space heater.
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This bad boy ran one 845 tube in class A2 SE per channel on 1050 volts. I ran the Chinese tubes at 100 mA or more, but stayed around 70 mA on the $$$$ vintage tubes.
The amp made a very nice sounding 30 WPC but burned 500 to 600 watts in the process. No good in Florida where I could barely keep the house cool. 70 of that was in the heaters of those two "light bulbs."
I haven't fired it up since we moved to cold country because we have curious grandkids and there is exposed 1050 volts on those tube sockets, and all sorts of live stuff on the PC boards. A rebuild has been on my project list for 5 years......
The amp made a very nice sounding 30 WPC but burned 500 to 600 watts in the process. No good in Florida where I could barely keep the house cool. 70 of that was in the heaters of those two "light bulbs."
I haven't fired it up since we moved to cold country because we have curious grandkids and there is exposed 1050 volts on those tube sockets, and all sorts of live stuff on the PC boards. A rebuild has been on my project list for 5 years......
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I built that nearly 15 years ago because I had a bunch of old 211 and 845 tubes that I got for free, and I got a pair of OPT's on Ebay from a guy who would later just take people's money and ship nothing. The rest of the parts were from stuff that I had on hand. The wood base was obviously meticulously crafted from some fine pine that I picked up in the street after a hurricane. The metal base was salvaged from a rather bent up interstate sign also found after the storm. It was I-69 which doesn't run anywhere near Florida, so I'm guessing it came from the party house about 2 blocks down the street.
Those tubes were commonly seen in some high end Japanese amps and some $$$$Audio Note, both called "Ongaku" but bearing no electrical similarities. Power was about 25 WPC in A1. I could get 30 WPC in A2 even down to about 30 Hz at 70 mA with the old tubes. I could crank up the current and make almost 40 WPC at 5% THD, but it caused saturation in the lower frequencies, and might have been the cause of a blown 5AR4.
The same tubes could indeed make over 200 watts per pair in push pull AB2, but a pair of 36LW6's can make that much power in AB1 on a more realistic B+ voltage into a more realistic OPT impedance....but I don't need to tell you that.
In post #438 of Pete's Engineers amp I managed to squeeze 504 watts from 4 X 35LR6's which are smaller than the 36LW6. I have collected the parts to make a stereo version for a 1KW tube amp. Yet another project that sitting in boxes waiting for me to build it.
Posted new P-P power amp design
Those tubes were commonly seen in some high end Japanese amps and some $$$$Audio Note, both called "Ongaku" but bearing no electrical similarities. Power was about 25 WPC in A1. I could get 30 WPC in A2 even down to about 30 Hz at 70 mA with the old tubes. I could crank up the current and make almost 40 WPC at 5% THD, but it caused saturation in the lower frequencies, and might have been the cause of a blown 5AR4.
The same tubes could indeed make over 200 watts per pair in push pull AB2, but a pair of 36LW6's can make that much power in AB1 on a more realistic B+ voltage into a more realistic OPT impedance....but I don't need to tell you that.
In post #438 of Pete's Engineers amp I managed to squeeze 504 watts from 4 X 35LR6's which are smaller than the 36LW6. I have collected the parts to make a stereo version for a 1KW tube amp. Yet another project that sitting in boxes waiting for me to build it.
Posted new P-P power amp design
Holy.
Living.
F- f- f- fuuuudge...
Heaty, meaty, big and (hopefully not) bouncy.
Mongo impressed!Sounds like my first DIY amp, a 12V6 PP affair driven by a 12SL7 input/phase inverter. OPTs were from a Heathkit AA-151 my brother literally found in the mud at a dump. The wooden chassis was made from maple sourced from the finest of pallets, and the top and bottom plates were handcrafted from "aircraft-grade" aluminum alloy (metal "appropriated" from road signs blown down in a windstorm).
Sounded pretty good though.
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