35V drop across the reg is still fine. Don't bother raising the reg's Vin in case you like the sound together with your pre. Let us know if it will bring perceivable subjective changes. How did you supply the DHT pre till now? Passive filtering?
I don't think so. This isn't a power stage but I'm driving a line transformer and it seems to sound best in this set up around 30mA. Vp is much lower than some have used. If I remember it right, Larry Moore recommended running the 10Y at 425Vp-k/35mA ! !
I'm running it in a old chassis that has been used a hundred times. The last few tubes have had to put up with power supplies made from the same old parts. This time it's 350VAC>Bridge> LCLC > One LC per channel> OT primary.
(The only thing purpose built for the 10Y's at this point are the heater supply boards from Rod Coleman which I'd highly recommend. I was running LT108- based current regs before this and am really surprised that you can net such an impressive qualitative improvement from there to here.)
I've noticed that if I set up the Simplistic regs and then shut down, when I fire everything up again the regs just sit there with only the CCS Vref voltage difference below the B+ at the output. I have to play with the trimmers again to get them to move. My first thought is that maybe the regulator doesn't like working straight into the reactance of the OT. I'll try a cap across the output to see if that changes it.
Sound ? It's very good but the shift in the tube's op point is too much to be able to make a flat A-B comparison. Fine detail is everywhere - both structural and tonal - yet no sense of dryness or analytic sound. This is all just impressions but it's my guess if I get them running a little more predictably that they'll be excellent.
It better has some ESR. It will surely bring the zero phase cross much lower and maybe like the OT a bit more.
P.S. Go ahead and modify to the newer recommended reg. No point in matching the old. The new one is better in sonics also.
It is as you say master. The left channel decided the low esr cap was just the ticket to freedom and is now gone on holiday. B+ on that side is now a steady and non-negotiable 74.5VDC.
The strangest part of it is that it sounds very nice. I think I've found a new op point for 10Y line stage tubes.
Now to figure out what exactly blew on that board . The heat sink was stone cold . . . . .
The strangest part of it is that it sounds very nice. I think I've found a new op point for 10Y line stage tubes.
Now to figure out what exactly blew on that board . The heat sink was stone cold . . . . .
OK. I'll build the new version as soon as I can get the 2SK
It wasn't the mpsa . . .
Any reason you can think of why a two LM336-5 reference diodes (for a 10V ref) in place of the 3 LEDs wouldn't be a good idea? It's what I had on hand and seemed to be a simple choice.
I'll pull the rest of the transistors and see how they are. I'm quickly learning why a roomy layout is a good idea for an experimental board especially when it comes to using small sand parts.
It wasn't the mpsa . . .
Any reason you can think of why a two LM336-5 reference diodes (for a 10V ref) in place of the 3 LEDs wouldn't be a good idea? It's what I had on hand and seemed to be a simple choice.
I'll pull the rest of the transistors and see how they are. I'm quickly learning why a roomy layout is a good idea for an experimental board especially when it comes to using small sand parts.
Hey All,
I'm building a PAS 3 using some good used boards that I found on eBay. I used Joe Curcio's phono equalization modification and replaced all the caps with new high quality ones. The Chassis is a PAT 4. The transformer is a Hammond 369 EX. I used one 190 tap and the 50 volt bias tap on the other side. With a bridge rectifier, a choke input using a JJ dual cap. I have 368VDC and .001-.000 ac volts ripple. I need to get down to 330VDC for the line board and 210VDC for the phono board. I spoke with DIGIKEY about MOSFETs but they seem to be either too much amperage or too little voltage. Would zener diodes accomplish this? Is there a simple high voltage regulator I could build?
And how much of a window would there be on these voltage supplies to the boards? I ask this question because if I use the end taps of the transformer, (380VAC), I end up with 574VDC without a load. I could simply divide this @ 61/39 to get 350 and 223. Is this a stupid idea?
As ever, thanks for any help you might provide, Kevin
I'm building a PAS 3 using some good used boards that I found on eBay. I used Joe Curcio's phono equalization modification and replaced all the caps with new high quality ones. The Chassis is a PAT 4. The transformer is a Hammond 369 EX. I used one 190 tap and the 50 volt bias tap on the other side. With a bridge rectifier, a choke input using a JJ dual cap. I have 368VDC and .001-.000 ac volts ripple. I need to get down to 330VDC for the line board and 210VDC for the phono board. I spoke with DIGIKEY about MOSFETs but they seem to be either too much amperage or too little voltage. Would zener diodes accomplish this? Is there a simple high voltage regulator I could build?
And how much of a window would there be on these voltage supplies to the boards? I ask this question because if I use the end taps of the transformer, (380VAC), I end up with 574VDC without a load. I could simply divide this @ 61/39 to get 350 and 223. Is this a stupid idea?
As ever, thanks for any help you might provide, Kevin
One LM329 would be easier and would create around 2.9V/R1 current setting, for a less toasty R1. Also just a DN2540 for a CCS as a whole, if contracting the parts count is paramount, can do. I wrote before you can use a J201 just as well if the K170 is the inventory problem. 1Meg Rref and 1k trimmer with the J201. Only the reference resistor will be much bigger due to much less reference current. But it will be climbing up to Vo slower during start up if you like that.
The one in the previous page. Some say that the MJE350 took them to 340V output in this reg although described as a 300V part. You could look for a 400V PNP also. 10-20V drop across the regs will keep them steady.
Thanks Salas, I found some 2SK's and will get some. Thanks also for the additional transistor info. I don't have much experience with them so anything you have to add is education for me.
. . . . . Got the boards back up and running with no cap across the output and so far they seem very good. Clear without any harshness - but I find the sand stuff pretty fidgety - I'm not used to the gain and it takes a while to understand why what didn't work yesterday is working today . . . . .
. . . . . After listening for a while the sound suddenly became tame. LF is considerably improved/tighter but highs are rolled off - my wife says it sounds great for restaurant or hotel lobby listening - acchhhh ptui!
(later. . . .) 22uF clipped in across the Simplistic's output makes a considerable improvement. So reckon there's something going on in the interaction with the output transformer. I need more/deeper knowledge of reactance and filters and I guess an upgrading of test gear capabilities.
Looking forward to trying your new circuit in a week or so.
Thanks !
PS. Left the post while I went to do some dishes. Leaving the music going while working I can now say this is sounding very fine. ! ! !
MJE5731A - is good to 375V and sounded better in the few times I used it to replace an MJE350.
Reacting badly yesterday and not today smells like a possible layout change when you serviced it? Taming out of the blue sounds like a thermal issue. Is the TO-92 MPSA near to the heatsink? A mini sink finned hat for it would help until you will make the newer one with K170 ref and TO-126 MJE error amp. In general these regs aren't made for powering output transformers, but if you can marry it to some application it is worth it. The newer one has been reported successful with spud and headphones amps with OPTs. Good luck & regards. Keep us posted.
Hey all,
I moved the filter choke to between the rectifier and the first filter cap. Then I put a 20k resistor between the first two caps. At this point in the rail I have 360 volts. Dynaco shows 355 here. That should be close enough. And since it is at this point that the supply diverges to the two different boards. From here on I'll stick with Dynaco's schematic. A 47k resistor to the phono board. And a 10k to the line stage.
But my general question here is what is the purpose of one of these regulated power supplies? Exactly? I built a regulated DC supply for the heaters in my 8b copy (using an LM317 from radio shack). And while it limits voltage it doesn't "hold up the voltage" during line changes. These MOSFET regulators seem complicated. And will they keep the set output even when line voltage drops?
And also, rather than put voltage regulation into each chassis. Wouldn't it make more sense to build one big regulated supply to plug all the components into? And does anyone here have plans for such a supply?
I realize these are amateur questions, but then I'm an amateur.
Kevin
I moved the filter choke to between the rectifier and the first filter cap. Then I put a 20k resistor between the first two caps. At this point in the rail I have 360 volts. Dynaco shows 355 here. That should be close enough. And since it is at this point that the supply diverges to the two different boards. From here on I'll stick with Dynaco's schematic. A 47k resistor to the phono board. And a 10k to the line stage.
But my general question here is what is the purpose of one of these regulated power supplies? Exactly? I built a regulated DC supply for the heaters in my 8b copy (using an LM317 from radio shack). And while it limits voltage it doesn't "hold up the voltage" during line changes. These MOSFET regulators seem complicated. And will they keep the set output even when line voltage drops?
And also, rather than put voltage regulation into each chassis. Wouldn't it make more sense to build one big regulated supply to plug all the components into? And does anyone here have plans for such a supply?
I realize these are amateur questions, but then I'm an amateur.
Kevin
1. To supply the tubes circuits with stabilized HT voltage supply.
2. To improve the sound of the tube amplifiers.