More parts came today. The 3 knobs I will be using. I will be using one of these four led lit on/off switches. Just not sure which one. There are 2 different sizes and each size is either a lit ring or a lit power symbol.
Hi fully_articulated, I need the chart with the info for setting the B+ voltages with the PS-21. Regards, Cambe
Hi Cambe. Unfortunately I've lost the manual for the PS-21 and don't have a scan of the table! You can use this formula though: Vout = 1.25(1+[R6 + R7]/R5) R5 is 249 Ohm so with a bit of messing around we can see what B+ the values of R6 & R7 will make. For instance, two 30K resistors is about 300V 1.25(1+[30000+30000]/249) = 302V In my build I wanted 210V which was produced with a 20K & a 22K resistor: 1.25(1+[20000+22000]/249) = 212V What B+ voltage are you after?
Hi fully_articulated, My PS-21 was gift from a friend a while ago. I have misplaced the manual too! Probably from looking at it so much! Thank you! That formula is exactly, what I am going to use. I have a few tube line stages I want to use the PS-21 with: Aikido Octal 6SN7 linestage - 300V 6N1P linestage - - 280V 12B4 linestage - - 200V
The problem with long capacitior leads is that they will have an inductance that at the very least will attenuate high frequencies. In some cases they might also induce hum or cause instability in the circuit. Anything longer than 1.5mm is not desirable. I learned this the hard way...most of those fancy caps are hard to integrate due to their size. Far better to use standard Polys..
Frustrating weekend. Seemed like one step forward and two backward. Nonetheless, here are the latest pictures. Doesn't look like much but a lot of time invested on the front and rear panels and wiring. Casing is still wrapped in duct tape to protect it from getting scratched.
If your weekend involved drilling all those holes in the front and rear panels then I'm not surprised it was a bit frustrating. I haven't come across a DIYer that enjoys the metalwork side that much. I find I always hit a rough patch toward the end of a project, when it all seems a bit futile. Anyway, it's looking good. Can't wait to see the finished product. PS - is that a 4U chassis?
Yes it is. Here are some links to the case and the extras. Slimline 4U Chassis Baseplate (Galaxy, Dissipante, Slimline, Pesante) Slimline Substitution: Top or Bottom Cover Anti-Vibration Feet (4 pieces) Last but not least, before final assembly, I will be taking the front and rear panels to an engraver so the inputs, outputs, volume and power can be put on.
The "unsuspected" frustration came from things like having to move the volume control standoff because the extension shaft/collar was interfering with one of the tubes and then finding out the extension shaft was now too short. Or from finding out the input/power relay board had 130 ohms of resistance between the line and neutral. I have used these exact boards on at least 2 occasions and never had a problem. The drilling I knew was gonna be a pain in the butt.....and it didn't disappoint. At least I had access to a drill press!
Have been considering a new preamp project recently and may try the CCDA (CCDA Line Stage Kits). Currently trying to get a tube regulated power supply for it up and running properly, and it's kicking my ar$e a bit. Voltage drop across the rectifier is much larger than it should be. At least it makes for a pretty picture.
I thought Broskie offered a HV regulated tube power supply, but I guess he doesn't. He has a HV tube power supply and LV regulated tube supply. Good luck with your new project. Having followed your previous build I have no doubt you will figure it out! I myself am considering this (Aikido PH-2 Phono Stage ) to go with the preamp I am hoping to finish soon.
That's a lot of tubes! If your preamp works out well, will you use the same power supply section for this as well? Thank you for the boost, I hope you're right. My last project was an upgrade to my ANK DAC in which I adequately redesigned the tube regulator PCB, but the circuit itself isn't quite powerful enough for an Aikido or CCDA. To be honest the regulator is more of a want than a need, so I may go with a tube rectifier only anyway.
Yes I will use the same PS-21 from GlassWare for this. I remember Broskie talking about not seeing the justification for a regulated tube HV power supply. I just cant seem to recall where I saw that and I don't remember what his reasons were.
I decided to use the PS-Tube power supply with a Neurochrome Maida regulator. This is similar to the PS-21, but the PS-Tube supply allows me to use a tube rectifier instead of the SS rectifier used on the PS-21. I'm not sure if it really matters with the regulator following the rectifier, but I thought I'd give it a try. Good luck with your projects.
Just did a few quick sims in PSUD2 to see what kind of difference one might see in the final voltage for an unregulated tube rectified supply with fluctuating mains input voltage. I can't guarantee my method, but let's pretend it's legitimate. Details: 240V primary 500VCT transformer 5Z4 rectifier Capacitor input power supply, followed an RC & LC filter 100mA load Results: 238VAC mains -> 247.91VAC tranny output -> 272.47VDC 240VAC mains -> 250VAC tranny output -> 275.31VDC 242VAC mains -> 252.09VAC tranny output -> 278.13VDC That's 2.82V difference in the output voltage per 2V deviation in mains voltage. I haven't ever measured how much mains voltage normally fluctuates and over what period of time. Considering my target voltage is going to be 280V, 2.82V is about a 1% change. Looking at it like that it hardly seems significant.
Very interesting. I don't have the PSUD2 software so that's good info. I wonder how 120VAC mains would change things, keeping all else the same.
Useless we have some data about average voltage changes for both 120V and 240V it's all a bit academic as they say. But the same increase/decrease in 120V mains would be worse than 240V if my maths is correct. For our 'perfect' transformer (that outputs 250V at exactly 120V mains input) an increase of 2V to 122V would see the output jump to 254.16 compared to 252.09 for 240V. Then again, are 120V fluctuations of the same magnitude experienced by 240V mains anyway? I've never tried researching this before, so am just stabbing blindly. Interesting as a thought experiment though.
I had a surge protector/power conditioner that had a mains voltage meter on the front and I never saw more than volt or 2 difference....at least at my home. I'm sure others could have more.
The combination of travel, work, and our floor refinishing project (which means my workshop is dismantled) has slowed things down considerably. I have made a bit of progress and will try to post something later today. With a tube rectifier and passive filtering and a constant current, the voltage variation on the output will pretty much follow the mains variation (as a percentage). But for most tube circuits where the bias is set by resistors, the current draw will increase as the voltage increases. Since the voltage drop across the rectifier as well as the passive components is increased as current increases, the power supply output voltage will change by a slightly smaller amount (as a percentage) compared to the mains variation in most situations. In the US, the mains voltage is not supposed to change by more than +/- 5%. In the EU, the mains can be as much as 10% high and 6% low and still be considered in-spec. Other countries will probably have different standards, but will most likely be in this ballpark. I have taken occasional measurements of my mains voltage and it has not varied by more than a couple percent. I don't think this variation will really make much difference in most tube circuits (particularly class A biased circuits like the preamps we are talking about). The variation from one tube to another of the same type can easily vary by more than this. Of course, it's not going to vary that much from one day to the next, so if your circuit is highly critical of the bias set point, then some form of regulation may be necessary. But I think the primary advantage of using some form of PS regulation is to reduce hum and noise. Even circuits with excellent power supply rejection (like the Aikido) will benefit from a cleaner power supply.
Being a bit fixated on steady voltage I never much considered the hum/noise aspect, even though I chose this regulator design because it was good in that area too. Thanks for the reminder.
