El Cheapo Transformer Question

pjanda1 · 22nd November 2011, 09:14 PM

I'm planning to try one last power supply on my El Cheapo: the doubler version Eli D. originally spec'd. The Triad N-77U was the original transformer, and ever the malcontent, I'd like to try something else. The Antek AS-1T150 looks to me like it ought to work. The secondaries are spec'd for a little less current, but Antek says they are probably good for more. Many folks seem to have had problems getting the B+ high enough with the Triad, the Antek should get it considerably higher. My output tubes (Tung Sol reproduction 6V6's) should be fine with up to 400V. I'm trying to move from a two chassis amp to one, and having the same transformer for B+ and the filaments would be great. The Antek is cheap, and I've had great luck with them. The amp currently has a 4T400 feeding a choke input PS (with the filament windings in series to boost the voltage) and a 6V Antek heating the tubes. It really looks to me as if the 1T150 will work, but I wanted the check in case I'm missing something.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

Eli Duttman · 23rd November 2011, 12:39 AM

You really can't get the B+ high enough using just the N-77U. That's why the latest power "iron" recommendation is a Triad N-77U for main B+, a Triad VPS24-1800 for "12" V heater power and B+ boost, a Triad C-24X B+ filter choke, and an Allied 6K27VF for 12AT7 heater power and B-. Buy all of 'em at once from Allied and save on shipping costs.

BTW, put ferrite beads on the "12" VAC winding used to energize the 'AQ5 and 12AL5 heaters. The beads keep "hash" from sneaking into the signal path, via the heaters.

kheper · 23rd November 2011, 12:41 AM

Antek AS-1T150:

(57.5V * 2) * .330A + (57.5V * 2) * .330A + (3.15V * 2) * 3A + (3.15V * 2) * 3A = ??? VA

37.95 + 37.95 + 18.9 + 18.9 = 113.7 VA

The 115V secondaries put out ~.330A per winding, but as Antek said they may put out more. If you parallel the 115V secondaries, then use a doubler, you will get ~.330A in total. For a PP monoblock (or even stereo), that is fine.

pjanda1 · 23rd November 2011, 08:54 PM

Eli,

Do you see any reason I couldn't use that Antek? I mean, I should probably take your advice, as perhaps I wouldn't have been through the first three power transformers and 50lbs of chokes. But hey, the Antek will be much cheaper, and more importantly, it will fit better. I'm going to try and fit the whole PS in my "signal" chassis, and that 1T150 has the same footprint as the Antek I'm currently using for just the heaters. I've already got a bias transformer. I'm thinking of the C-14X for the choke, as more henries can't hurt, and the added resistance will help keep the B+ down. I also might have a choke that fits. We'll see.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

kheper · 23rd November 2011, 09:28 PM

Your schematic has no voltage figures, so I cannot tell if the Antek will provide the voltages you think you need. The Antek will supply the required current, however. You can do better than using the 1T150 as a voltage doubler. Antek has many transformers, which could be used to supply your voltage and current needs with a more conventional FW or FWB.

pjanda1 · 23rd November 2011, 09:48 PM

I know Antek has many transformers. Like I said in the first post, the amp currently has a 4T400 running into a 15lb 'swinging' input choke. But, I'd like to lose the 35lb power supply and turn this into a single chassis amp for my kitchen. I'll be happy with 350-400V B+. I'm thinking the 1T150/voltage doubler setup is going to put me at the top end of that (quick and dirty PSUD sim had it just under 400V), but I will be loading it down decently (compared to how lightly I'm taxing the current 4T400 and the separate 100VA filament transformers), and PSUD doesn't consider the load on the filament windings.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

Eli Duttman · 24th November 2011, 01:21 AM

The AnTek trafo mentioned is NOT suitable. The data sheet indicates about 300 mA. RMS is available, when the B+ secondaries are paralleled. Figure on only 25% of the RMS current being available as DC, after Greinacher doubling.

The N-77U can comfortably deliver 200+ mA. of DC, after being voltage doubled. No small part of the good performance "El Cheapo" delivers comes from the PSU's "cojones".

pjanda1 · 28th November 2011, 10:43 PM

Boy, I should have thought this through before ordering all the doubler parts from Jim McShane. The N77-U and the booster cost more than the beastly Antek 4T400! I'm half tempted to start unwinding the HV secondary on it to get down around 300V, then wire the primaries up for 230V, which I figure (based on talking to Antek tek support) would net me a little under 150V at 200VA. The problem is that I'd still have a 9lb transformer. The upside is that its free and I wouldn't have to find a home for a giant power transformer. Another option is two 1T150s, which only saves $5-15 over the Allied stuff. I know the doubler supply saves money on caps, but it looks as if a traditional cap input could use cheaper, easier iron!

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

kheper · 2nd December 2011, 08:05 AM

You could series the secondaries of the Antek, let the center tap "float", use a FW bridge, get 422Vdc then drop it. The current available will be 205ma.

If the paralleled windings will not work, you could use one winding per channel and double each. In Antek's specs, there is 330ma per winding.

22nd November 2011, 09:14 PM	#1
pjanda1 diyAudio Member Join Date: Jan 2005 Location: The Nebraska Panhandle	El Cheapo Transformer Question I'm planning to try one last power supply on my El Cheapo: the doubler version Eli D. originally spec'd. The Triad N-77U was the original transformer, and ever the malcontent, I'd like to try something else. The Antek AS-1T150 looks to me like it ought to work. The secondaries are spec'd for a little less current, but Antek says they are probably good for more. Many folks seem to have had problems getting the B+ high enough with the Triad, the Antek should get it considerably higher. My output tubes (Tung Sol reproduction 6V6's) should be fine with up to 400V. I'm trying to move from a two chassis amp to one, and having the same transformer for B+ and the filaments would be great. The Antek is cheap, and I've had great luck with them. The amp currently has a 4T400 feeding a choke input PS (with the filament windings in series to boost the voltage) and a 6V Antek heating the tubes. It really looks to me as if the 1T150 will work, but I wanted the check in case I'm missing something. Paul Wild Burro Audio Labs - DIY Full Range Speakers

24th November 2011, 01:21 AM	#7
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	The AnTek trafo mentioned is NOT suitable. The data sheet indicates about 300 mA. RMS is available, when the B+ secondaries are paralleled. Figure on only 25% of the RMS current being available as DC, after Greinacher doubling. The N-77U can comfortably deliver 200+ mA. of DC, after being voltage doubled. No small part of the good performance "El Cheapo" delivers comes from the PSU's "cojones". __________________ Eli D.

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23rd November 2011, 12:41 AM	#3
kheper diyAudio Member Join Date: Jun 2007	Antek AS-1T150: (57.5V * 2) * .330A + (57.5V * 2) * .330A + (3.15V * 2) * 3A + (3.15V * 2) * 3A = ??? VA 37.95 + 37.95 + 18.9 + 18.9 = 113.7 VA The 115V secondaries put out ~.330A per winding, but as Antek said they may put out more. If you parallel the 115V secondaries, then use a doubler, you will get ~.330A in total. For a PP monoblock (or even stereo), that is fine.

23rd November 2011, 08:54 PM	#4
pjanda1 diyAudio Member Join Date: Jan 2005 Location: The Nebraska Panhandle	Eli, Do you see any reason I couldn't use that Antek? I mean, I should probably take your advice, as perhaps I wouldn't have been through the first three power transformers and 50lbs of chokes. But hey, the Antek will be much cheaper, and more importantly, it will fit better. I'm going to try and fit the whole PS in my "signal" chassis, and that 1T150 has the same footprint as the Antek I'm currently using for just the heaters. I've already got a bias transformer. I'm thinking of the C-14X for the choke, as more henries can't hurt, and the added resistance will help keep the B+ down. I also might have a choke that fits. We'll see. Paul Wild Burro Audio Labs - DIY Full Range Speakers

23rd November 2011, 09:28 PM	#5
kheper diyAudio Member Join Date: Jun 2007	Your schematic has no voltage figures, so I cannot tell if the Antek will provide the voltages you think you need. The Antek will supply the required current, however. You can do better than using the 1T150 as a voltage doubler. Antek has many transformers, which could be used to supply your voltage and current needs with a more conventional FW or FWB.

23rd November 2011, 09:48 PM	#6
pjanda1 diyAudio Member Join Date: Jan 2005 Location: The Nebraska Panhandle	I know Antek has many transformers. Like I said in the first post, the amp currently has a 4T400 running into a 15lb 'swinging' input choke. But, I'd like to lose the 35lb power supply and turn this into a single chassis amp for my kitchen. I'll be happy with 350-400V B+. I'm thinking the 1T150/voltage doubler setup is going to put me at the top end of that (quick and dirty PSUD sim had it just under 400V), but I will be loading it down decently (compared to how lightly I'm taxing the current 4T400 and the separate 100VA filament transformers), and PSUD doesn't consider the load on the filament windings. Paul Wild Burro Audio Labs - DIY Full Range Speakers

28th November 2011, 10:43 PM	#8
pjanda1 diyAudio Member Join Date: Jan 2005 Location: The Nebraska Panhandle	Boy, I should have thought this through before ordering all the doubler parts from Jim McShane. The N77-U and the booster cost more than the beastly Antek 4T400! I'm half tempted to start unwinding the HV secondary on it to get down around 300V, then wire the primaries up for 230V, which I figure (based on talking to Antek tek support) would net me a little under 150V at 200VA. The problem is that I'd still have a 9lb transformer. The upside is that its free and I wouldn't have to find a home for a giant power transformer. Another option is two 1T150s, which only saves $5-15 over the Allied stuff. I know the doubler supply saves money on caps, but it looks as if a traditional cap input could use cheaper, easier iron! Paul Wild Burro Audio Labs - DIY Full Range Speakers

2nd December 2011, 08:05 AM	#9
kheper diyAudio Member Join Date: Jun 2007	You could series the secondaries of the Antek, let the center tap "float", use a FW bridge, get 422Vdc then drop it. The current available will be 205ma. If the paralleled windings will not work, you could use one winding per channel and double each. In Antek's specs, there is 330ma per winding.

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