OK... quick background.. plenty of tube building experience... but I've never used a Hammond Transformer. I have an old homebrew amp on my bench that the 50 year old power tranny finally gave up on. I need a replacement transformer. I have been looking at the Hammond 272JX because it's specs fit the bill nicely. However, I've been reading on the tube section here and read "the 2 series are bad, you must get a 3 series they are so much better" over and over and over. One poster even said the 2 series had knockouts in the bell, which the 3 series dont. OK, here's the kicker, I have the Hammond catalog in front of me right now. And the only spec difference is the extra taps for the universal primary and bias tap. Everything else is the same, including the knockouts in the bell housing. So what gives? What's the real difference?
The 300 series is rated for 50/60 hz where as the 200 series is only rated for 60 hz. In order for a transformer to run at rated specs at 50 hz, it needs to be about 20 % larger than the same transformer that is only rated for 60 hz, for the same specs.
Basically, the higher the AC frequency the transformer will work at, the smaller it can be, because its efficiency goes up with higher frequencies.
What this means applied to the 200 and 300 series transformers at 60 hz (USA, Canada, and I think Japan line frequency) the 300 series will run much cooler at 60 hz at the given load, because the core is about 20% larger.
Hope this helps... Daniel
Basically, the higher the AC frequency the transformer will work at, the smaller it can be, because its efficiency goes up with higher frequencies.
What this means applied to the 200 and 300 series transformers at 60 hz (USA, Canada, and I think Japan line frequency) the 300 series will run much cooler at 60 hz at the given load, because the core is about 20% larger.
Hope this helps... Daniel
The "300" series can be used on 50 Hz as well as 60 - that means more primary turns, and 20% lower flux density on 60 Hz. Less likely to buzz, less inrush current, and of course larger physical size and higher cost for the same rating.
Do you need 50 Hz or 240V? Use 300 series. 200 series may win on size though... will 300 series fit?
Do you need 50 Hz or 240V? Use 300 series. 200 series may win on size though... will 300 series fit?
There are several differences. If you look at the size chart, you'll see that the 3** series is a core size or two larger. The 3** series has very versatile dual 100-110-120v primaries, which can really help you get the secondary voltages you need. The 3** series also has a bias tap on the HV secondary, in case your amp has 'fixed' (negative supply) bias.
About 50% of the 2** trans I used developed mechanical hum (an overall problem with Hammond) when used at anything above about 50% derating, and all got too hot to touch for more than an instant.
Your amp, your call; but I don't even look at the 2** transformers any more. The pro series aren't that much more expensive.
Aloha,
Poinz
About 50% of the 2** trans I used developed mechanical hum (an overall problem with Hammond) when used at anything above about 50% derating, and all got too hot to touch for more than an instant.
Your amp, your call; but I don't even look at the 2** transformers any more. The pro series aren't that much more expensive.
Aloha,
Poinz
Thanks everyone.. the larger size/running cooler makes sense... I guess what I'm struggling with here is that it appears to me these are made with the same cores (across the series - not necessarily the 272JX vs 373JX), same bell housing construction, etc... so I don't see why the 200s are buzzing and the 300s aren't. I don't need universal, I don't need negative bias... and the transformer would be running at about 50% of it's rated capacity. I have decided to go with the 300 just because there must be something to all the comments on the forum here, but in the back of my head it just seems like the other would fit the bill nicely too at 2/3 the price.
Listen, Daddyo,
Make how you like. The 3** trans is made with one size up core, has no knockouts (euw!) in the bells, and the adjustable primary may end up (how do I know this, hm?) being more useful than you dream right now.
Look at the difference in price. You want the best for your dozens (hundreds) of hours of sweat equity, or you don't think this is value?
Up to you,
Poinz
Make how you like. The 3** trans is made with one size up core, has no knockouts (euw!) in the bells, and the adjustable primary may end up (how do I know this, hm?) being more useful than you dream right now.
Look at the difference in price. You want the best for your dozens (hundreds) of hours of sweat equity, or you don't think this is value?
Up to you,
Poinz
even if its the same core size, designed for 50 hz, and the no of turns can be different, all that still affects buzzing ( magnetic B) ability
its to do with volts ( same? ) , frequency (50 hz capable better ), core size, no turns, even if core size is the same, more turns will mean lower b, meaning lower heat and buzzing, and of course, more turns, means more copper, longer to wind, more money.
its to do with volts ( same? ) , frequency (50 hz capable better ), core size, no turns, even if core size is the same, more turns will mean lower b, meaning lower heat and buzzing, and of course, more turns, means more copper, longer to wind, more money.
OK, several points to address here - the Hammond catalog shows and specifies knockouts on BOTH models. That's 200 and 300. Why does everyone keep saying they don't have knockouts? I can't find an image of one that doesnt when searching images.google.com? That was one of my original questions. As for dozens of hours - not hardly, more like 30 minutes - less time than spent in this forum. All im doing is replacing a failed transformer. The circuit has an autobias feature I did - so I don't even have to bias the tubes. As for the universal primary - it won't be useful - I don't need it. Not to single you out per see, but it is posts like POINZ's here that made me ask in the first place, because they seem to be saying things without anything that backs it up. It sure shows knockouts on hammonds site too:Poindexter said:
Look at the 300 page
Re: Knockouts
OK this is beyond bizarre. Again, the specs are same hi-pot test value, same temp and insulation value and it even says finished to match our series 200 and audio output transformers. Which implies that they MATCH - not look different as you say. It clearly shows the knockouts in the photo and the diagrams. Oh well... like I said, I am going to order the 300, but it's clear that something strange is going on - and frankly if there is so much difference between them, Hammond should be expressing that. It seems very odd that they list the differences as very minor, when everyone here says they are so vast. The finish means nothing as I will be repainting it to match the amp. Again, one more reason why I feel like the 200 series should fit the bill nicely. I don't care about the knockouts either - plenty of old stock trannies Ive used have had them. It wouldn't keep me from buying a tranny. Im also glad you agree with him, but he didn't say anything that wasn't in my original questions. I agree it's not worth worrying over for $30 and 1 transformer. But I may end up ordering more later and I'd like to understand the differences - especially when I don't need ANY of the extra features. I suppose ordering 1 of each would do the trick, then I could compare them side by side.. hmm... that might actually be the way to go.
MikeR said:
OK this is beyond bizarre. Again, the specs are same hi-pot test value, same temp and insulation value and it even says finished to match our series 200 and audio output transformers. Which implies that they MATCH - not look different as you say. It clearly shows the knockouts in the photo and the diagrams. Oh well... like I said, I am going to order the 300, but it's clear that something strange is going on - and frankly if there is so much difference between them, Hammond should be expressing that. It seems very odd that they list the differences as very minor, when everyone here says they are so vast. The finish means nothing as I will be repainting it to match the amp. Again, one more reason why I feel like the 200 series should fit the bill nicely. I don't care about the knockouts either - plenty of old stock trannies Ive used have had them. It wouldn't keep me from buying a tranny. Im also glad you agree with him, but he didn't say anything that wasn't in my original questions. I agree it's not worth worrying over for $30 and 1 transformer. But I may end up ordering more later and I'd like to understand the differences - especially when I don't need ANY of the extra features. I suppose ordering 1 of each would do the trick, then I could compare them side by side.. hmm... that might actually be the way to go.
I have just completed a Tubelab SimpleSE and since I live in Australia with 240 volt mains I used a 300 series transformer. If you look at my thread http://www.diyaudio.com/forums/showthread.php?s=&threadid=104475 you will see a picture of the 300 transformer, I cant quite remember, (I am away from home at the moment) but from the photo it looks like there are no knockouts on the power transformer (there are on the choke). If you decide later that you might like to re-use the transformer for a different project, the 300 series transformers multiple input taps will allow you quite a bit of flexibility to change the output voltage. This flexibility may or may not be useful to you in the future and that is probably what you will have to consider when spending your hard earned folding!!
Anyway, good luck with your project I hope it works well for you whichever way you decide.
Chris
Anyway, good luck with your project I hope it works well for you whichever way you decide.
Chris
Agreed, the 300 series has features you don't need. BUT... is your line voltage higher than 115V? (mine is generally 122-124V). 120V tap on the 300 will be closer than the 115V primary on the 200. The inrush current will be less, easier on the power switch. The magnetic field escaping from the 300 will be much less, since the 200 will be running close to core saturation.
Bottom line: I'd use a 200 series to fix somebody else's amp at the lowest cost. I'd use a 300 series to build my own.
Bottom line: I'd use a 200 series to fix somebody else's amp at the lowest cost. I'd use a 300 series to build my own.
If you are looking at low cost, do any of the Edcore transformers fit the bill? No 5v tap though.
http://www.edcorusa.com/products/transformers/xpwr/xpwr107.html
http://www.edcorusa.com/products/transformers/xpwr/xpwr107.html
Chrish - thank you so much! That's a very helpful link. I love the fact those are made in the USA. Great price too. Any input on the quality? Have you used them... ? As for 5V - I do not believe in tube rectification. I've built several amps over the years where you could switch between tube or solid state rectification and every single one sounded worse and had less power with the tube rectifier. So, never again. Anyway, Thanks! -Sean
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