Getting ready to build a modded 16LS kit(canceled)
I got a 16LS kit for Christmas. Kinda got me hooked on Hifi again, obsessed honestly. Didn't take long to update the transformers with edcor cxpp25-5K. Then switch it to UL. Transformers were selected from a thread here. Only output option on that is 8 ohm output. I misunderstood, or someone misspoke, and thought that would give me 4 ohm output. So I built 4 ohm speakers. Tubes want 10K ohm plate load, and it's a parallel push pull design. So it's really 8 ohm out. I still think I'm getting very good results.
So I want to design an amp since I was given a pair of ESLs and they seem to need 100W. I want to do a lot of playing before I try a build with ppp kt88s. But that's a subject for later. And only if I can fix the ESLs.
The 16ls kit is on a pcb and is hard to mess with. I decided to start with it's design and use things I already have and make a few changes. 12vdc heater supply, negative bias instead of this shared cathode bias. Mostly I want it point to point so I can get leads on things, hooking scope probes to this is plain scary. I'm trying to get a solid understanding of how exactly UL is working. Maybe I'm stupid but it keeps me awake at night.
I have a few questions.
Since I have 25W transformers, and the current design puts out 16W. I was planning to use 6 12AQ5s instead of 4 6AQ5s since they're cheap and I have a 12VDC supply for the heaters. It'd drop the output impedance, plus the charts say the tube would like a little more primary for minimum distortion. That would give me 150mA current(with the same bias point, it's 100mA now). From looking at the ratings for other cxpp25 transformers I thought this was safe.
I contacted edcor and they replied this transformer is 120mA max AC+DC. I was going to stay class A. How critical is this max current? I didn't think transformers saturate in PP. More voltage isn't an option. Bias each tube a little lighter?
Should I scrap this idea all together? Or just go ahead with neg bias and stay with 4 tubes per channel? Was hoping to get a good 24W amp and then bi-amp the speakers I built.
Thanks
Cory
I got a 16LS kit for Christmas. Kinda got me hooked on Hifi again, obsessed honestly. Didn't take long to update the transformers with edcor cxpp25-5K. Then switch it to UL. Transformers were selected from a thread here. Only output option on that is 8 ohm output. I misunderstood, or someone misspoke, and thought that would give me 4 ohm output. So I built 4 ohm speakers. Tubes want 10K ohm plate load, and it's a parallel push pull design. So it's really 8 ohm out. I still think I'm getting very good results.
So I want to design an amp since I was given a pair of ESLs and they seem to need 100W. I want to do a lot of playing before I try a build with ppp kt88s. But that's a subject for later. And only if I can fix the ESLs.
The 16ls kit is on a pcb and is hard to mess with. I decided to start with it's design and use things I already have and make a few changes. 12vdc heater supply, negative bias instead of this shared cathode bias. Mostly I want it point to point so I can get leads on things, hooking scope probes to this is plain scary. I'm trying to get a solid understanding of how exactly UL is working. Maybe I'm stupid but it keeps me awake at night.
I have a few questions.
Since I have 25W transformers, and the current design puts out 16W. I was planning to use 6 12AQ5s instead of 4 6AQ5s since they're cheap and I have a 12VDC supply for the heaters. It'd drop the output impedance, plus the charts say the tube would like a little more primary for minimum distortion. That would give me 150mA current(with the same bias point, it's 100mA now). From looking at the ratings for other cxpp25 transformers I thought this was safe.
I contacted edcor and they replied this transformer is 120mA max AC+DC. I was going to stay class A. How critical is this max current? I didn't think transformers saturate in PP. More voltage isn't an option. Bias each tube a little lighter?
Should I scrap this idea all together? Or just go ahead with neg bias and stay with 4 tubes per channel? Was hoping to get a good 24W amp and then bi-amp the speakers I built.
Thanks
Cory
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Your plan of taking on a kit to learn on before tackling 100W is a good one, but IMHO throwing that much effort and $$$ at modding the 16LS kit is not worth it. I would just look for a different kit as your 1st project.
Well the 16ls is done built, and I actually got good results. I was just trying to use the edcor transformers again. Parts wise I need about 60 in parts to build it. Wasn't planning on ending up with a 16ls, hoped to get something better this time.
Not sure the Edcor is a good choice for 3 pairs of 12AQ5's, because neither the UL tap % nor the maximum current rating seems like a good match.
Is the ideal UL tap percentage published somewhere? I looked and didn't find it.
Thanks
Cory
Hate to resurrect a long dead thread of mine. I was looking at output transformers again and noticed that similar comparable transformers are rated around that 120mA point, but they are per side. With some online calculators I figured it would be pretty hard to ever get the rated 25W in class A with that spec.
So is this rating 120mA per plate lead? I've read through their support forums and saw my exact question " is that total? Or per side?" answered with a simple "yes". I emailed edcor and haven't gotten a response yet, not sure if I should be hopeful after the forum question. But it brings me to another question on the wording of AC + DC, that would imply to me that it's B+ current.
Thanks for any advise
Cory
So is this rating 120mA per plate lead? I've read through their support forums and saw my exact question " is that total? Or per side?" answered with a simple "yes". I emailed edcor and haven't gotten a response yet, not sure if I should be hopeful after the forum question. But it brings me to another question on the wording of AC + DC, that would imply to me that it's B+ current.
Thanks for any advise
Cory