Input transformers

[tiroth]

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/audio/wsm/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?

 

[serengetiplains]

Tribute gets my vote as a high contender:

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

Is Audio Note still selling transformers?

 

[SY]

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.

 

[Jocko Homo]

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.

 

[SY]

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.

 

[Jocko Homo]

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

 

[tiroth]

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&ie=UTF-8&q=jensen+site:jeffrowland.com

Any number of reasonable reasons why that could have occurred of course. Thanks for the input!

 

[jam]

Jeff Rowland uses Lundahl input transformers in his newer poweramps, I believe he uses some Jensens in his preamps.

 

[Peter Daniel]

It is Jensen in JRDG Concentra amp

 

[jam]

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.

 

[Steve Eddy]

Jensen has been my Top Pick for years as well. Though I've a feeling that may change soon and CineMag may take that spot.

Embarrassingly, I'd only recently come across them, even though they've been around since 1979 and have a legacy going back to Altec Lansing in the 1940s and 50s.

They seem to offer the same level of quality as Jensen (and they're located in the same neck of the woods) but their prices are significantly lower. Hopefully I'll know for sure in a month or two when I get some samples.

se

 

[tiroth]

Excellant specs for distortion, CMRR and FR, although phase response is substantially worse than Jensen. (no other manufacturs seem to publish this!)

Steve, I'd be much obliged if you kept us in the loop. I'm been to their site but was turned off when there were no prices or distributors to be found.

 

[Steve Eddy]

Excellant specs for distortion, CMRR and FR, although phase response is substantially worse than Jensen. (no other manufacturs seem to publish this!)

You can't compare the two. Jensen doesn't plot phase, they plot Deviation from Linear Phase (DLP). Any frequency independent delay will cause phase shift, but that doesn't cause waveform distortion as all frequencies still arrive at the same time. What DLP effectively measures is frequency-dependent delay (in effect, group delay), which does cause waveform distortion.

So you can't direclty compare a phase plot with the DLP plot. A DLP plot of the CineMag transformers may look identical to the equivalent Jensen transformer.

Deane Jensen wrote an AES paper on this some years ago. If you're interested, EMail Jensen and they'll send you a copy.

Steve, I'd be much obliged if you kept us in the loop. I'm been to their site but was turned off when there were no prices or distributors to be found.

Will do.

You're in the US you'd just buy direct from them. As for prices, yeah, that's rather a bummer, but you can always ask.

The price I was quoted for a transformer otherwise identical to one of Jensen's but with a bigger core and subsequently the ability to handle a higher input level, the price was about 30% less than what Jensen is asking for their model with the smaller core.

It's rather interesting how I happened to come across CineMag.

I was about to EMail Jensen to see if they could make me one of their microphone transformers but with either a larger core or a 50% nickel core so it could handle a higher input level.

Before I EMailed Jensen, just for grins I Googled on "microphone transformer."

CineMag was one of the hits that came up.

I perused their website and saw that they offered a microphone transformer that for all the world appears to be the same as the model I was considering from Jensen.

I noticed that they had a second version of the same model but which was rated for a higher input level. They had the EXACT same thing that I was originally going to have Jensen make for me.

Weird how things like that work out sometimes.

se

 

[tiroth]

You can't compare the two. Jensen doesn't plot phase, they plot Deviation from Linear Phase (DLP).

Thank you! A very important distiction -- I was thinking this was a plot of phase response relative to "linear" (implying flat), not realizing that group delay could result in a non-flat- but linear-phase response.

 

[Bas Horneman]

What am I missing? There are a ton of "input transformers" out there, which are worth considering? Best buys? Best quality price notwithstanding?

Thanks for this thread Tiroth..I have this innate love for transformers...dunno why..I must be weird..

Amplimo make a 1:1 (10k:10k) transformer someone might have an opinion on

40,50 - Euro's (Signal transformer type TM81 )

Little specs though..


Cheers,
Bas

 

[johnnyx]

Has anyone seen a transformer with an extra feedback winding, of the type Rupert Neve uses, whilst looking through the specs, or did he have them specially made?
He achieved very good performance with these, 300kHz bandwidth for example.

 

[tiroth]

I would think any phase splitter (1:1+1 or more flexible) transformer could be used...unless there was some special winding ratio required.

 

[pooge]

Jensen has been my Top Pick for years as well. Though I've a feeling that may change soon and CineMag may take that spot.

Embarrassingly, I'd only recently come across them, even though they've been around since 1979 and have a legacy going back to Altec Lansing in the 1940s and 50s.

They seem to offer the same level of quality as Jensen (and they're located in the same neck of the woods) but their prices are significantly lower. Hopefully I'll know for sure in a month or two when I get some samples.

se

There was a former relationship between Jensen and Reichenbach Engineering family. A son of Ed Reichenbach apparently owns Cinemag. Google the two names in newsgroups, and look for postings by Bill Whitlock, the present president of Jensen, for some history.

As I understand it, Jensen's contribution to transformers was the Bessel response characteristic, which provides the excellent group delay characteristic.

 

[StevenOH]

This is the response I received from CineMag to my inquiry:

"The CMOL-3x600T2 goes for $100.34/ea in quantities of 1-10 pieces. The CMOL-2x600T2 sells for $93.65 in the same quantities.
Allow $15 for shipping/handling for U.S. delivery.
We only sell direct to our customers. "


Steven

 

[tiroth]

I tested out some of those Edcor transformers...pretty disappointing. Here is it against a Talema 1.6VA power tranny and for reference Jensen and Cinemag trannies. The pro ones are from the datasheets, and note their reference level is 6dB higher.

The CMLI-15 is, I believe, $38 for 1-10.

An externally hosted image should be here but it was not working when we last tested it.