Has anyone noticed that Antek has added a few new items sometime recently? They have a 360V version with 70V taps now as well as another that seems to have a bit more 6.3VAC capacity. I can't remember what the specs were before, but I think the old one is now the AS-* and the new ones are AN-*. Hard to tell because the link to the PDF is broken on the AS models.
The AN-4TK360 should be very well-suited to a souped up Millett DCPP amp, I'd imagine. I bought the AN-4TK400 for it and it's a bit much without more extensive mods than some might want.
There a bunch of other new ones too and a few new voltages that I don't remember from before.
The AN-4TK360 should be very well-suited to a souped up Millett DCPP amp, I'd imagine. I bought the AN-4TK400 for it and it's a bit much without more extensive mods than some might want.
There a bunch of other new ones too and a few new voltages that I don't remember from before.
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and in c-cores, and in EI cores... because it is a capacitive phenomenon, not an inductive one.
Russ,
How much voltage do you get out of the AN4TK400 at, say, 200 mA load and 120 V in?
I'm considering getting one for a project but would prefer to see some solid data before deciding on a transformer to get.
Thanks,
~Tom
I have a pair of Antek AN-4T360 which gives me a nice 500V or so either full bridge (both secondarys in parallel) or 506V with the usual CT type arangement and two diodes, both loaded at 600mA. This is plain capacitor input using 2 x 1000uF 400V Evox Rifa PEH169s in series with 220K droppers accross them. Of course this is way more load than you would use but I thought I would play. I used household incandescent bulbs as a load.
With the 4TK400 I think you would get somewhere around 560V or so with solid state rectifiers and capacitor input. You could lower it with vacuum rectifiers or CRC. Choke input would give you somewhere around 360V out.
Cheers Matt.
With the 4TK400 I think you would get somewhere around 560V or so with solid state rectifiers and capacitor input. You could lower it with vacuum rectifiers or CRC. Choke input would give you somewhere around 360V out.
Cheers Matt.
I wired a 4T400 up to a Simple SE. There is no 5 volt winding and I think a Chinese 5AR4 would explode under these conditions so I used the SS diodes. I got 545 volts which made the KT88's rather hot and bothered. I also had the stock Panasonic 500 volt caps in the board so I didn't leave it on long. I decided that the 4T400 was too much for the Simple SE.
I have some 4TK400's and I had one hooked to the red board early last year. If I remember right I got about 550 volts. I am now using two of the $15 transformers for 630 volts unloaded and 600 volts with both channels cranking out 100 watts each. In this case more IS better.
I have some 4TK400's and I had one hooked to the red board early last year. If I remember right I got about 550 volts. I am now using two of the $15 transformers for 630 volts unloaded and 600 volts with both channels cranking out 100 watts each. In this case more IS better.
That doesn't quite jive with what I got on the red board with the AN4TK400, but I was using the stock, on-board FW rectifier and ripple filter. I may need to tweak the divider on the ripple filter a tad. I got 475V of B+ under load.
http://www.diyaudio.com/forums/tube...-new-p-p-power-amp-design-38.html#post2139924
http://www.diyaudio.com/forums/tube...-new-p-p-power-amp-design-38.html#post2139924
Makes sense. The ripple filter has a voltage divider in it. Granted, 47k/1M doesn't shave much off the voltage, but math says:
1M/(47k+1M) = 0.955
475 * 1/0.955 = 497 V
So you should see 500-ish volt across the reservoir cap. 1.25 * 400... That's in line with what I'd expect. 550 V sounds high. But only by 10 %.
~Tom
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I found that more capacitance across the rectifier output gets the voltage up. My line voltage is 122 volts.
I am running the output tubes on my red board directly off of the rectifier ahead of the ripple filter. This way the mosfet runs cool.
Initial experiments with Antek and red board made the mosfet and the dropping resistor unhappy, so I ran the entire board off of a 2T230 (I had one) which runs the board at about 280 volts DC after the mosfet. I used the 4T400 for the raw plate supply only and I used a big cap (2 X 470 uF in series).
It would be possible to run a red board with all Antek transformers, but I would use something like a 1T230 or 1T250 to supply the B+ for the board. An AN-0525 (series FWB) or AN-0540 (FWCT) could be used for the bias supply. The big Antek of your choice could be used for the output tube plate supply and heaters. Depending on my choice of output tubes it could be anything from a 4T360 to a 4T500.
I wanted more power and I found the cheap power transformers on Ebay so I modified my set up. One $15 transformer runs the entire red board using the on board rectifiers (with 2 more diodes added for a FWB) mosfets filter and bias supply. An off board 470 uF 450 V cap is used across the bridge output. The second $15 transformer with its own bridge and cap generates a second 300 volt supply that is wired in series with the main supply for 600 volts of B+.
Makes sense. Bigger cap --> less ripple voltage --> higher DC voltage.
What's the current draw of the red board at the 500+ volt? I.e. how much current runs in the transformer secondary?
~Tom
That is a great big It Depends!
It depends on how much power output you want, how much B+ voltage you run, and what impedance the OPT's are.
When I had it set up with 35LR6's at 250 WPC I measured the total DC power out of the power supply at 650 volts DC and 1.3 AMPS! That is 845 watts of DC to make 500 watts of audio for 59% efficiency.
Right now I am running 600 volts of B+ through 6HJ5's. With 6.6K ohm OPT's I get about 75 WPC at clip and the maximum DC current is about 350 mA. With the same setup running at 3.3K ohms I get about 125 WPC at clip and the DC current is about 700 mA.
My rule of thumb for guestimations is about 60% plate efficiency for a well designed class AB P-P amp. So for a 250 watt amp you will need about 420 VA of power transformer for the plate supply plus heater power. I measured 700 mA on 600 volts which is 420 watts. A normal HiFi amp will not be run at full power all of the time and a 250 watt amp will see 10 to 40 watts of average power output even if it is cranked to the edge of clipping on peaks. The efficiency drops at low powers and goes to zero at idle. The red board draws 140 mA at idle so minimum power is 84 watts plus heater current. In reality you don't need a 400 VA transformer for a 250 watt amp since you aren't going to leave it at full power all the time, but some reserve is always good. The common Antek size just happens to be 400VA. I have not tested the red board with an Antek for extended periods of time yet.
I have a 100VA Antek running a Simple P-P and it does see a lot of use at near max power. The transformer gets warm but not hot.
Indeed. At idle the FETs were fine but at max power with a sine wave they got toasty. I attributed most of it to the screen supply, but I can't say for sure since they were on the same heat sink. The dropping resistor got a little smelly after being leaned on for a minute or two.
The 550 V you quoted earlier was that measured with power out or at idle? What I'm trying to get a handle on is how much voltage I should expect to get out when the transformer is under load.
I currently have a modified 2T350 supplying my 300B amp. My modification consists of adding a 12 V winding to it. I pull about 100 W out of the transformer -- 70~75 W for the B+ supply and roughly 25 W for the heaters. The 200 VA transformer gets quite toasty. About 60 C with ambient being 18~20 C. Now, 60 C is a bit toasty but certainly not in danger territory.
I'd be fine with a 400 V, 200 VA tranny, but Antek doesn't make one.
~Tom
Yeah, there are a lot of transformers I need but Antek doesn't make.
Probably at power, but I can't remember what the power level was since my red board has been operated at levels from 15 WPC to 250 WPC. THere is a live red board on my bench and two big Anteks sitting here too, so I will try to connect them together and see what happens, maybe this weekend.
The SSE experiments were with about a 200 mA load since each driver consumes 10 mA and the KT88's like 80 to 100 mA.
I haven't made any temp measurements on the Simple P-P but the transformer is a lot colder than the Hammond sourced Allied transformer in my SSE. That one is too hot to touch after a couple of hours. Of course I am sucking 200 mA from a 150 mA transformer so......
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