I don't have any idea what type circuit is on the filament boards that Tent Labs sells. But My amp went from a mild hum to dead silent with 106 spl speakers by switching to them. You can't tell its turned on without sticking your head inside the speakers. I am using D3a driver tubes and they have AC on the heaters but are silent as well.
I have an existing pair of 811A monoblocks which I want to add the Rod Coleman v9 heaters to the DHT 811A tubes. I have the parts, specced for 4A with a raw DC supply and just received some 100VA transformers to power the heater circuit. It's just that I want to make sure I'm doing everything right.
The amps are inspired by the MJ magazine Cathode feedback design and executed by Belgian firm Aquablue. They have three stages EF86-KT66-811A into Lundahl LL9202 OPTs.
If we look at the transmitter tube, this is the schematic. Now the part I highlighted is actually a 100 Ohm pot (WX14-11) to adjust the bias.
In the Coleman Reg application notes, I read the following:
Do I need to add the Rk of 1 Ohm additionally?
The amps are inspired by the MJ magazine Cathode feedback design and executed by Belgian firm Aquablue. They have three stages EF86-KT66-811A into Lundahl LL9202 OPTs.
If we look at the transmitter tube, this is the schematic. Now the part I highlighted is actually a 100 Ohm pot (WX14-11) to adjust the bias.
In the Coleman Reg application notes, I read the following:
Now am I correct in that I leave the pot in the circuit but disconnect one end of it (positive filament)?
Do I need to add the Rk of 1 Ohm additionally?
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A quick question that would help me outlining a future project: Is the range of the trimmer large enough to use the same regulators for both 7,5V 1,75A and 6,3V 1,92A filaments without changing any components?
Standard versions go all the way to 7A.
If that's not enough, they are also able to parallel perfectly, even if the currents are not matched. There is no voltage control to get in the way; the currents simply add like Kirchoff tells them to.
See Bob's "Mid Life Crisis" for an example using the 833A (10A at 10V)
No problem. It's within adjustment range. The voltage does not make any difference.
Excellent, thanks!
I have a pair of V8 regulators here that I bought from a friend who used them in a 3A5 linestage. R1 appears to be 4,7 ohms, and each board has one plastic cased power transistor and one with a metal tab. As far as I can understand from the "Versions V1 to V8, general applications note" these should be the transmitter version, intended for >10W filaments?
I finally took the time to rebuild the PSU for my 6S4S PP amp. The HV supply remains the same (Hammond 370LX, 4* 6AU4GTA and a CLC filter) but the filament supplies using 400/24V industrial control transformer (operating at 230V for minimum mechanical noise) followed by cLCLC filters with Lundahl LL2772/3A input chokes.
I could have built a nice amp using IDH tubes and decent budget iron for the price of only the input chokes but this time everything is electrically and mechanically quiet and the amp itself is almost eerily detailed.
I could have built a nice amp using IDH tubes and decent budget iron for the price of only the input chokes but this time everything is electrically and mechanically quiet and the amp itself is almost eerily detailed.
@Rod Coleman : Hi Rod! I have an amp using V8 regulators and I want to change the output DHT bias to a CCS and an ultra path cap. Does it matter if the CCS goes from filament + to ground and ultra path C from filament - to B+, or should they get connected the other way around? Or can they get connected either way?
Is there a chance the CCS in the regulator might get upset by the bias CCS? What would I look for in that case?
Thank you for your support!
Is there a chance the CCS in the regulator might get upset by the bias CCS? What would I look for in that case?
Thank you for your support!
Not yet, perhaps one day😀
My next order there will be a pair of LL3720/40mA for a future 4P1L class A2 SET project.
I just finished a budget version using Edcor OPTs and Hammond plate chokes and even that one sounds quite marvellous, I can only imagine what that tube is capable of mated with proper iron.
Hi!
The regulator usually does not care about the anode and cathode circuits, providing the Filament Raw DC is floating and there is no circuit path across the filament.
So the signal cap and the DC cathode current return should go to the same side of the filament. You can try either side for best sound.
Post a circuit drawing, if you would like more comments.
I fthe cathode voltage is high compared to chassis, it is often better to avoid the TO-220 mounting hole for metal-flange Q5. Instead use a clip, or make up a fixing bracket of yor own, to apply pressure to the body of the Q5.
Thanks for the feedback.
"If the cathode voltage is high compared to chassis, it is often better to avoid the TO-220 mounting hole for metal-flange Q5. Instead use a clip, or make up a fixing bracket of yor own, to apply pressure to the body of the Q5."
I have had issues trying to dc couple an amp with V8 regulators that were at 130V to heatsink/PE where the output stage drew excessive current. With another dc coupled amp using V9 regulators riding on 300V there were no issues.
"If the cathode voltage is high compared to chassis, it is often better to avoid the TO-220 mounting hole for metal-flange Q5. Instead use a clip, or make up a fixing bracket of yor own, to apply pressure to the body of the Q5."
I have had issues trying to dc couple an amp with V8 regulators that were at 130V to heatsink/PE where the output stage drew excessive current. With another dc coupled amp using V9 regulators riding on 300V there were no issues.
You must be really strong or going on a third hernia, judging by all that iron 😉
I'm working on a 4P1L SET as well at the moment, for headphones though. Still looking for the OPT, but probably need something custom as I want a 10K primary and 32 or 35 ohm secondary. I looked at the LL2765AM but the 4K6 impedance is on the low side to my taste, and was still thinking over getting a placeholder from toroidy.
Looking forward to seeing your work on that 4P1L amp.
BTW: using @Rod Coleman 's V9 for the 4P1L filament 🙂 Hi, Rod!!!