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Old 3rd June 2004, 05:29 PM   #1
tiroth is offline tiroth  United States
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Default Input transformers

There as been a lot of talk about input transformers in threads, but given that prices have changed and information was often incomplete, I'd like to stimulate some debate on the issue. Here are the rankings based purely on the numbers that I could find; I'd welcome feedback on alternative suppliers, subjective quality, etc. I'm mainly thinking of trannies that are 10K:10K with cores that are reasonably oversized (can make it up to +10dB or better without gross distortion)

Top Pick - Jensen
$70 direct
Has most comprehensive set of measurements of any manufacturer I've seen, and the measurements are excellant. Jeff Rowland has a couple pages praising them.
http://www.jensen-transformers.com/ln_in.html

Tier 1
Lundahl
$58 (LL1544a from K&K)
Good measurements but not great detail. Widely acclaimed by DIYers, but is the $12 price difference compared to Jensen worth it?
Manufacturer http://www.lundahl.se/catframe.html
U.S. Dist. http://www.kandkaudio.com

Stevens & Billington
? I think these are quite expensive
Not great detail. Level handling not spectacular, but high FR flatness.
http://www.stevens-billington.co.uk/

Tier 2
Sowter
$30-40 for better models, direct
Decent performance but does appear to be worse than Tier 2 in terms of FR flatness. Better level handling than S&B for the most part.
http://www.sowter.co.uk/

Tamura
?
They make everything from modem-type to higher quality trannies. Availability unclear.
http://a1.solidweb.com/ps/wi-tamura/customer.nsf

Tier 3
Generic
Generally $5-15
These are generic, relatively poorly performing, transformers. Much better than modem type coupling transformers but not hi-fi. Sometimes 70V output trannies are used as line inputs.

Edcor
$8.24 direct
I think they spec distortion as <0.5% at 20Hz, not sure of level.
http://www.edcorusa.com/transformers...wsm10k-10k.htm

Tier 4
These are modem coupling, PA, etc. transformers-the kind you find at Radio Shack. FR is often specified in a very narrow range, 300-5000Hz or worse.

DIY
$9? from Digikey
I've used Talema potted toroids successfully--they have high FR flatness, but very poor distortion performance *at low frequency* due to insufficient inductance. CMRR is probably poor. I measured THD to be -100dB at 1kHz and rising and goes downhill rapidly by the time you dip below 100Hz.

Moving on
What am I missing? There are a ton of "input transformers" out there, which are worth considering? Best buys? Best quality price notwithstanding?
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Old 3rd June 2004, 05:36 PM   #2
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Tribute gets my vote as a high contender:

http://www.tribute-audio.nl/

Is Audio Note still selling transformers?
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Old 3rd June 2004, 05:51 PM   #3
SY is offline SY  United States
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After trying some vintage 1:1 transformers over the years, I was pretty down on the whole concept. The Jensens turned me around. My subjective experience with them has been excellent- my system is quieter than it ever has been, and the sound didn't homogenize and soften like it did with, say, vintage Ampex transformers.
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Old 3rd June 2004, 09:26 PM   #4
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I prefer the Lundahls. The Jensens have more roll-off and insertion loss.

With either one, you have to play games with the loading. The terminations that Lundahl suggests I find are off a bit.

But you can easliy compensate for any frequency roll-off. No sustitute for keeping out RF. I have used one of them in all my designs the last few years.

As for which one that JRDG uses............maybe you should look more closely.


Jocko.
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Old 3rd June 2004, 09:29 PM   #5
SY is offline SY  United States
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Haven't tried the Lundahls, but the Jensens meet their 100kHz spec and with a 10K load, no ringing. The insertion loss is quite real.
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Old 3rd June 2004, 09:31 PM   #6
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Default Yes........

It does meet spec, but if you misterminate it just the right way, you can correct for some of the roll-off.

(Also depends on the rest of the system............an end-to-end solution.)

Jocko
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Old 3rd June 2004, 11:25 PM   #7
tiroth is offline tiroth  United States
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Yeah, I am pretty sure Rowland is using Lundahl in some bridgeclone pics I saw a bit ago, but he also has pages up eulagizing Jensen as the best transformers out there.

http://www.jeffrowland.com/transfor.htm
http://www.jeffrowland.com/tectalk2.htm
http://www.google.com/search?hl=en&i...effrowland.com

Any number of reasonable reasons why that could have occurred of course. Thanks for the input!
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Old 4th June 2004, 02:21 AM   #8
jam is offline jam  United States
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Jeff Rowland uses Lundahl input transformers in his newer poweramps, I believe he uses some Jensens in his preamps.
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Old 4th June 2004, 02:35 AM   #9
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It is Jensen in JRDG Concentra amp
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Old 4th June 2004, 03:45 AM   #10
jam is offline jam  United States
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Peter,

Check again. That transformer is to the pre-amp input or output of their integrated. You need to check the 211, 301 and 501 power amps.......... nice try though.

Regards,
Jam

P.S. Also the Concentra is a discontinued product.
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