Great job!
After you have some time to listen, please share your views on how the Transcendars sound with/without cathode feedback.
I had both 3K and 5K Transcendars on mine and never felt the need to apply cathode feedback to them. I have Hammond 125ESE mounted up right now, and they definitely benefit from cathode feedback.
Not sure that a Simple SE should hiss; mine is tomb quiet.
Win W5JAG
After you have some time to listen, please share your views on how the Transcendars sound with/without cathode feedback.
I had both 3K and 5K Transcendars on mine and never felt the need to apply cathode feedback to them. I have Hammond 125ESE mounted up right now, and they definitely benefit from cathode feedback.
Not sure that a Simple SE should hiss; mine is tomb quiet.
Win W5JAG
Thanks to all for the compliments! 
Here's a link to the George's site:
http://tubelab.com/AssemblyManualSimpleSE/schematic_SSE.htm
So far, I like the 6CA7-EH. I haven't tried anything else for comparison, though. I've got the New Sensor KT88 (seen in post #7) and some old WWII era 6L6GA (post #12 & 13). I intend to try the KT88, but I don't dare stick in the 6L6GA with the kinds of B+ I've got right now.
I've thought about them, but again I'm worried the B+ from the Hammond is too hot. Of course, for $30 a quad, do I mind roasting a couple to find out?
My initial impression is that the Transcendars sound fantastic. Easily worth the $100 I spent on the pair. I did ask Gery to add the UL tap, and that's how I have them hooked up. The power tubes have screen grids, so why strap them as triodes? Figuring that's going to impact their damping, I went ahead and connected the cathode feedback too. I didn't install switches, but it's easy enough to rewire it without UL and feedback. Sooner or later, I'll get around to trying it that way. As they are now, the bottom end is very satisfying - no complaints here.
The hiss is nothing major, and not something you'd notice from the listening chair. You have to walk up to the speaker and put your ear to the tweeter to hear it. Regardless, it is there and it's noisier than my ST35. Perhaps I should try a different 12AT7? I've got a HP labelled GE in there now. Somewhere around here I've got a Telefunken. I guess I ought to go look for it. The overall high gain of the amp still seems a little weird to me, though. I can't help but wonder if I somehow swapped a set of resistors or something.
Tam Shaun said:
Here's a link to the George's site:
http://tubelab.com/AssemblyManualSimpleSE/schematic_SSE.htm
Zap said:
So far, I like the 6CA7-EH. I haven't tried anything else for comparison, though. I've got the New Sensor KT88 (seen in post #7) and some old WWII era 6L6GA (post #12 & 13). I intend to try the KT88, but I don't dare stick in the 6L6GA with the kinds of B+ I've got right now.
chrish said:
I've thought about them, but again I'm worried the B+ from the Hammond is too hot. Of course, for $30 a quad, do I mind roasting a couple to find out?
w5jag said:
My initial impression is that the Transcendars sound fantastic. Easily worth the $100 I spent on the pair. I did ask Gery to add the UL tap, and that's how I have them hooked up. The power tubes have screen grids, so why strap them as triodes? Figuring that's going to impact their damping, I went ahead and connected the cathode feedback too. I didn't install switches, but it's easy enough to rewire it without UL and feedback. Sooner or later, I'll get around to trying it that way. As they are now, the bottom end is very satisfying - no complaints here.
The hiss is nothing major, and not something you'd notice from the listening chair. You have to walk up to the speaker and put your ear to the tweeter to hear it. Regardless, it is there and it's noisier than my ST35. Perhaps I should try a different 12AT7? I've got a HP labelled GE in there now. Somewhere around here I've got a Telefunken. I guess I ought to go look for it. The overall high gain of the amp still seems a little weird to me, though. I can't help but wonder if I somehow swapped a set of resistors or something.
I never heard much music come from a tube (heating, crackling and poping, yes) but the OPT's WILL sing to you. Some are louder than others. You don't notice it with speakers kooked up because they are much louder.
That is the first place that I would look. The second place would be a noisy resistor. I have not had an amp hiss at me yet. Does the hiss change with the volume control? If so disconnect your input cables. If not, remove the 12AT7. If the hiss goes away the problem is in the 12AT7 circuit.
It could be the output transformers. I assumed it was the tubes.
I tripled checked every resistor, and they are all correct. I swapped out the GE 12AT7 for another GE. The results are pretty much the same. I noticed that at least two thirds of the hiss is coming from my Adcom preamp. If I switch it off, things are quieter. I hadn't noticed with my ST35 since it doesn't have as much gain as the Simple SE.
In all seriousness, I'm being fanatically picky about the hiss. I've been told I have ears like a dog, and I can hear a computer monitor that's been left turned on in another room across the house.
I'll try pulling the 12AT7 and power up the amp, but at this point I think there's not really a problem here. I might try to rig up a simple fixed voltage divider at the input to attenuate the input signal.
I tripled checked every resistor, and they are all correct. I swapped out the GE 12AT7 for another GE. The results are pretty much the same. I noticed that at least two thirds of the hiss is coming from my Adcom preamp. If I switch it off, things are quieter. I hadn't noticed with my ST35 since it doesn't have as much gain as the Simple SE.
In all seriousness, I'm being fanatically picky about the hiss. I've been told I have ears like a dog, and I can hear a computer monitor that's been left turned on in another room across the house.
I'll try pulling the 12AT7 and power up the amp, but at this point I think there's not really a problem here. I might try to rig up a simple fixed voltage divider at the input to attenuate the input signal.
So, here's my thought for using the 6L6GA tubes. It basically involves switching out the C1 cap, which will give me a choke input power supply. If I believe PSUDII, I'd expect to get right around 450 volts with C1 in the circuit and about 305 volts without it.
Does anyone see any big problems with my idea? Am I going to end up with high voltage on traces too close together?
Does anyone see any big problems with my idea? Am I going to end up with high voltage on traces too close together?
- Cut the trace marked with an 'X', between C1 and R2.
- Do not install R1.
- Do not install FREDs.
- Solder a short jumper wire (~ 4") at the end of the R1 pad which leads to C1.
- Attach other end of jumper wire to FRED solder pads leading to SW1-O2.
- Install SPST switch between SW1-O1 and SW1-O2.
- For a capacitor input power supply, attach the choke between L1-O1 and L1-O2. Close SW1.
- For a choke input power supply, attach the choke between L1-O1 and SW1-O1. Leave SW1 open.
I think that your idea will work.
I have done a choke input Simple SE, but I did it differently. I used two chokes. The PC board was assembled according to the instructions. I cut the trace in the same location that you have marked. The board was then wired up normally including the choke and supplemental capacitor (if desired). The additional choke is added between the SW1-O1 terminal and the L1-O2 terminal. This puts the choke in the circuit where you just cut the trace. You can then wire a switch across the choke to disable it.
This allows the original CLC filter to remain in place and a LCLC filter to be used for choke input.
I have done a choke input Simple SE, but I did it differently. I used two chokes. The PC board was assembled according to the instructions. I cut the trace in the same location that you have marked. The board was then wired up normally including the choke and supplemental capacitor (if desired). The additional choke is added between the SW1-O1 terminal and the L1-O2 terminal. This puts the choke in the circuit where you just cut the trace. You can then wire a switch across the choke to disable it.
This allows the original CLC filter to remain in place and a LCLC filter to be used for choke input.
Hmm... playing with PSUD2, it seems the 1.5H choke might not be a good choice. It gives me lots of warnings about exceeding the rectifier's max PIV rating, and the output waveform looks weird (ugly). Nothing much less than 3H seems like a safe bet, especially if the load current drops a bit from the 140ish mA I'm pulling now. Probably something to do with that whole critical inductance thing.
I'm guessing right now that my best choice might be something like a Hammond 159S - 4H and 65 ohms. Sticking a NTC device (like a CL90) on the primary side of the PT might not be a bad idea, either.
I'm guessing right now that my best choice might be something like a Hammond 159S - 4H and 65 ohms. Sticking a NTC device (like a CL90) on the primary side of the PT might not be a bad idea, either.
I was using a surplus 8H choke in my setup. The critical inductance requirement must be met for a choke input filter to work right. It is far better to have too much inductance than not enough. The Triad C-14X (6H 150 ohms) may work OK. It is cheap ($15) but UGLY, you need to hide it. I found some end bells from an old power transformer that fit after removing the mounting bracket.
The CL90 is a good thing and I have them in most of my amps. I have recently started using two of them one goes in series with the power transformer primary. This softens the initial surge caused by cold tube filaments. The second CL90 goes in series with the HV center tap. This makes life easier on the 5AR4 when it has to charge up some empty caps while it is still warming up. Recent new production 5AR4's seem to be a bit weak in this area.
The CL90 is a good thing and I have them in most of my amps. I have recently started using two of them one goes in series with the power transformer primary. This softens the initial surge caused by cold tube filaments. The second CL90 goes in series with the HV center tap. This makes life easier on the 5AR4 when it has to charge up some empty caps while it is still warming up. Recent new production 5AR4's seem to be a bit weak in this area.
I loaned a Simple SE to a friend who normally listens to a multi gigawatt home theater system. He plays movies, MP3's and CD's. He connected the Simple SE in place of his front 2 channels amps. He was not impressed with the tube sound saying that it wasn't loud enough, and the thunder didn't come out right.
He did report a strange occurrence. When he played a movie that he had played multiple times before that contains a gunplay scene his cats ran from the room and hid. This did not happen with his big box rig.
Ty, great you got it working. FWIW, I used switches for cfb and UL/triode, and far prefer triode with no cfb. UL sounds punchier at first, but the effect is tiring after some time. I am using the James OPTs and Omega XRS single driver speakers (93 dB sensitivity). I'm sure with your OPTs and speakers things will be different, but I've heard this from some others as well, so rigging up switches to compare might be a good idea. I'm keeping UL for when I want the power, but I will take cfb out of the circuit entirely.
Also, I'm using the new issue Tung Sol 6550 power tubes and am very impressed with their neutrality and soundstaging capabilities. The whole system just disappears.
I had some hum at first, but I used a short 12g wire to connect the Simple SE chassis to my preamp chassis, and this eliminated all but the faintest trace of noise.
Dave
Also, I'm using the new issue Tung Sol 6550 power tubes and am very impressed with their neutrality and soundstaging capabilities. The whole system just disappears.
I had some hum at first, but I used a short 12g wire to connect the Simple SE chassis to my preamp chassis, and this eliminated all but the faintest trace of noise.
Dave
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