I am building a zenclone and many are using the Hammond 272FX mains transformer.
Are there better choices that will make a difference on the output or overall noise ?
Angela is selling an interesting option ...
I have finally selected R-core from Softone for my outputs but still did not decide on the main beast
Are there better choices that will make a difference on the output or overall noise ?
Angela is selling an interesting option ...
I have finally selected R-core from Softone for my outputs but still did not decide on the main beast
The 3xx series have dual primaries with multiple taps which generally allows you to get reasonably close.
For reasons of economy (to reduce copper usage, etc.) modern transformers are generally designed to produce their rated output voltage only at the specific load for which they were designed and at the nominal line voltage. A few additional turns are usually added to a secondary to compensate for copper losses at the rated load thus allowing the use of smaller wire. (more heat too of course) Lightly loaded of course the effect of the dcr will be lessened and the output voltage will accordingly be higher.
Some vintage/mil transformers were designed with very low winding dcr and exhibit better regulation over a range of load currents than is the case for cheaply made modern transformers. The price for this is a larger, but cooler running (and more expensive) transformer for a given current rating.
For reasons of economy (to reduce copper usage, etc.) modern transformers are generally designed to produce their rated output voltage only at the specific load for which they were designed and at the nominal line voltage. A few additional turns are usually added to a secondary to compensate for copper losses at the rated load thus allowing the use of smaller wire. (more heat too of course) Lightly loaded of course the effect of the dcr will be lessened and the output voltage will accordingly be higher.
Some vintage/mil transformers were designed with very low winding dcr and exhibit better regulation over a range of load currents than is the case for cheaply made modern transformers. The price for this is a larger, but cooler running (and more expensive) transformer for a given current rating.
Hi Kevin. While you're right, in the case of the Hammond transformers on my bench it's a rock/hard place situation. My experience is loading just the filament winding to rated current isn't nearly enough. A modern Hammond fully loaded on all windings however will run red hot due the economic considerations you outline. In comparison, the Antek toroid I bought recently, or the 40 year old AMI/Rowe jukebox iron that makes up my current daily listen, all put out very close to 6.3 VAC fil. Given how dramatically sensitive tube life is to filament overvoltage I would never use a Hammond PS tranny without careful measurement and consideration. The multiple tap primary models would also be first choice.
(Toroids have they're own set of issues but I'm fortunate to have a local utility with no DC on the lines and view it as an opportunity to play around with RF power supply filtering. Lemonade!)
(Toroids have they're own set of issues but I'm fortunate to have a local utility with no DC on the lines and view it as an opportunity to play around with RF power supply filtering. Lemonade!)
"Are Hammond power transformers good enough?"
I used a Hammond with a 550Vct / 150mA secondary operating at something like 180mA with a +/- SS power supply. Since this one also has a 5.0Vct / 3A secondary that's not being used at all, and a 6.3Vct / 6A secondary that's supplying 15mA for a panel LED (I prefer to power up the heaters separately) the primary is still well within its VA rating. It doesn't get all that hot even after hours of use. Wouldn't recommend overloading if you're gonna draw significant current from the heater windings as well as the HV sec., however. Otherwise, there aren't any problems with either heat or noise.
For this particular application, Hammonds are "good enough".
I used a Hammond with a 550Vct / 150mA secondary operating at something like 180mA with a +/- SS power supply. Since this one also has a 5.0Vct / 3A secondary that's not being used at all, and a 6.3Vct / 6A secondary that's supplying 15mA for a panel LED (I prefer to power up the heaters separately) the primary is still well within its VA rating. It doesn't get all that hot even after hours of use. Wouldn't recommend overloading if you're gonna draw significant current from the heater windings as well as the HV sec., however. Otherwise, there aren't any problems with either heat or noise.
For this particular application, Hammonds are "good enough".
One other advantage to the 300 series... they're rated for 50/60 Hz operation. This means that the flux in the core is at least 30% below the saturation level when operated on nominal 60 Hz line. So less vibration, less magnetic field escaping, less idle current in the primary. Of course this isn't FREE... it takes more wire, maybe more core for the same rating.
Of course if you need 50 Hz, it's your ONLY choice from Hammond...
Of course if you need 50 Hz, it's your ONLY choice from Hammond...
Thanks ... I wasn't expecting to get all this input.
Great info on the Hammond stuff.
I have seen reviews and comparisons for output transformers, but I was not able to find a good source for mains transformers for tube amps.
What do they use in the mid to high prices tube amps ? Are they all custom made ?
So far the options are:
http://www.one-electron.com/Trans/BFT1B_11.pdf
http://www.amplimo.nl/download/7N1474.pdf
http://www.triodestore.com/mq060.html
the angela intrument big iron
and the electraprint custom made.
And does anybody have the correct specs for the Decware SE84CS ?
Great info on the Hammond stuff.
I have seen reviews and comparisons for output transformers, but I was not able to find a good source for mains transformers for tube amps.
What do they use in the mid to high prices tube amps ? Are they all custom made ?
So far the options are:
http://www.one-electron.com/Trans/BFT1B_11.pdf
http://www.amplimo.nl/download/7N1474.pdf
http://www.triodestore.com/mq060.html
the angela intrument big iron
and the electraprint custom made.
And does anybody have the correct specs for the Decware SE84CS ?
kevinkr said:
I'm having Hammond 374BX on each of my DIY 30W PP tube amp monoblock and I've measured 120mA current, (B+ winding rated at 175mA, AVR regulated at constant 240VAC input and tapped correctly) yet it reached a hot to touch temperature after 40minutes but not further even after 2 hours of play. It satisfactorily silent. Hammond should have made this to rate the model at least 200mA for wider DIY possibilities. I feel they're very good trannys (even their OP's) but the offerings in specs can somewhat limit one's choice in DIY projects.
I once posted this question of this level of heat emmitted in this forum and someone did reply that its quite ok as he's runs his equipment similarly. From my personal view, I feel uncomfortable about it but what the heck..its entirely replaceable and not an expensive OEM part in case it goes kaput.
I am happy with my Amplimo 7N607 power transformer. It was reasonably priced, too. I'm running it close to its maximum rated output and it only gets slightly warm. It's under the chassis for aethsetic reasons (it's ugly) but it was very easy to mount.
I know toroids have a wide bandwidth, compared to E-I types, and are capable of passing lots of noise from the mains into the secondary windings, but I haven't noticed a problem. If I did, I'd have to put some sort of suppressor in there, I suppose. At least toroids don't have such a wide stray electomagnetic field.
I know toroids have a wide bandwidth, compared to E-I types, and are capable of passing lots of noise from the mains into the secondary windings, but I haven't noticed a problem. If I did, I'd have to put some sort of suppressor in there, I suppose. At least toroids don't have such a wide stray electomagnetic field.
Edcor offers EI PTs too. They also do custom.
For big stuff theres Peter W. Dahl Co.
Toroids are also more sensitive to DC offset, whether that matters at all hinges on your local power.
For big stuff theres Peter W. Dahl Co.
Toroids are also more sensitive to DC offset, whether that matters at all hinges on your local power.
coolmaster said:
Not much. Depending on the type of supply (choke or cap input), the solid state version could have higher current peaks. Since heating is current squared times resistance, the higher peak current would generate more heat (you'd also have higher output voltage). But the effect wouldn't be large. If you add series resistance to equal the tube rectifier, the output would be the same and the heat would be the same.
Sheldon
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