Anyone have experience using Edcors with the Quickie?

[SPaulMac]

I currently have the Speco transformers in my Quickie for headphone use. I've purchased a set Edcor EM0735 transformers for hopefully slightly better performance, but have no idea how to wire them into the circuit. Can anybody help me with the following inquiry?

I finally got around to ordering the Edcor EM0735 transformers. Now that I have them before me, I have to admit that I probably have no business with a soldering iron in my hands. I have no clue as to how to hook the new transformers into my Quickie's circuit in place of the Specos. I'd imagined something like the signal ground going to both the C.T. and Common taps on the primary and secondary; the signal going to the 8K ohm tap on the primary and the output going from the 250 ohm tap of the secondary to the headphone jack, but I don't really look forward to smoking my little Quickie. I'd be very thankful for any help I can get on the proper wiring procedure for this transformer. The pin assignments for the EM0735 are as follows:

Primary

Pin 1    8K Ohm
Pin 2    Center Tap
Pin 4    8K Ohm

Secondary

Pin 5    250 Ohm
Pin 6    32 Ohm
Pin 8    Common

Thanks,
Stephen

[Paul Joppa]

What confuses me is the primary as listed:

Pin 1    8K Ohm
Pin 2    Center Tap
Pin 4    8K Ohm

This looks like a push-pull transformer, though it might just be an odd way of listing the transformer. It's not clear to me whether this is a 16KCT primary, or an 8KCT primary, or an 8KSE primary with a tap, possibly for ultralinear(?) Normally, if single-ended, there would be some indication of which end (pin 1 or pin 4) should go to AC ground, and which is "hot" for signal. I have not been able to find any listing of this transformer on the Edcor web site - am I looking in the wrong place?

Anyhow, that's why I haven't posted on this question.

[vanofmonks]

I commissioned this model originally, and it was confusing when I first saw it, but it was designed as an 8k winding that they put a CT in.  So for parafeed pin 1-4 is 8K  It is similar to all their other line output transformers in that it is push pull, but can be used as parafeed out.  They stated it should have about 15h inductance for what it is worth.  I have 10, but still have been to lazy to wire them in by quickie.  Hope this helps.

[Dr. Toobz]

Not to resurrect an old thread, but any updates on these? I have all the parts laying around to build a spare Quickie for headphone use in a bedroom, and would be interested in how these Edcors held up in comparison to the Specos.

[vanofmonks]

Ok, I have a prelim report on the EM0735.  I created an external box with the transformers and connect to the quickie via rca to 1/8th inch cable.  I have a jack for both the 32ohm and 250ohm taps.  Unfortunately, I am waiting on some new D cells, but did a quick test with some 1.2v rechargeables that need a charge.  I used both a grado sr80i from about 1997 via 32ohm and a beyerdynamic dt880 via 250ohm.  Both worked fine and played plenty loud with rock, though could not really go too loud with the dt880.  The grado's were fairly sibilant.  Dt880 well balanced.  Both had nice defined bass.  This was only a few songs and not broken in by any means.  I will be able to do better listening this weekend when I have the D cells.

Short answer is they seem to work as they should and nice listenable sound.  I may be able to compare with the speco if I can find my spares and the crack if I fix the left channel.

Chris

Edit: This is on a bone stock quickie.  I have not installed my pjccs yet.

[Dr. Toobz]

I called Edcor last Friday to ask about the EM0735, and it turns out that they still had a pair on the shelf! The set is slated to arrive via UPS on Monday, so I'll post observations at that time. Right now, I'm down to a single pair of headphones, HD650's, so I will be interested to see how well these work on the 250 ohm tap.

[Dr. Toobz]

Received these Edcors the other day and have now hooked them up to the Quickie. First impressions with HD650 headphones are very positive, especially for an $11 transformer! Mids and treble sound much smoother and flatter than the Speco line-transofmers I once used long ago. Bass is good, but definitely lighter than the Crack amp. I do have to say, there is something about this one-stage, DHT, battery-powered amp that is letting through details and sound-staging that even my Crack and SEX amps don't have. Perhaps the magic is in the simplicity?

I have these wired as standard transformers, with the secondaries going back to the common ground. I do wonder if wiring these little guys as autoformers would buy some extra inductance (and therefore, better LF response), and am I also assuming that the 2.2uF coupling caps in there right now are big enough? I also wonder if the secondaries could be floated from ground, or even made into a sort of balanced arrangement by taking the common and 250 ohm taps to the headphones and grounding the unused 32-ohm taps. What's best?

EDIT: I should mention that I'm using the PJCCS to load the tubes, which are 1940's Raytheons. Capacitors are Solens, and the source is an HRT Music Streamer II.

[Doc B.]

Perhaps the magic is in the simplicity?

I think so, specifically the single gain stage. That was my reasoning behind doing the single gain stage Smack amp. These single gain stage amps are less sensitive and thus need a little more signal level coming in, but they reward you with a little more resolution.

[Dr. Toobz]

I'm not home to try this, but I just was thinking about the notion of wiring these puppies as autoformers vs. standard transformers. I've read somewhere that in the SEX 2.0, such a wiring arrangement really "helped out" the Specos, which I presume is because they don't have all that much inductance at certain frequencies. In fact, my own experiments showed better bass response when wired this way, but I have never understood why. These little Edcors might not be much better in the LF realm, so I'm wondering if there is any theoretical advantage to wiring them as a single, tapped coil vs. the usual method. Does an autoformer arrangement really buy any more inductance, considering that the secondary winding must have far fewer windings than the primary?

[Paul Joppa]

Inductance goes as turns squared, so 10% more turns makes 21% more inductance.

[Dr. Toobz]

The step-down for the Edcors isn't as severe as the Specos used in the SEX to drive speakers; I have them wired for 8k:250 ohm. On my cheap meter, which is not terribly accurate (a Fluke will surely be needed before my Stereomour arrives), the primary DCR is 263 ohm (or 122 ohm and 141 ohm from the "center" tap to each end, suggesting that maybe it's not the center after all), while the secondary measured out at 24 ohm for the 250 ohm tap (8 ohm at the 32 ohm tap). How does that work out for turns ratio, etc?

[Paul Joppa]

Turns ratio is the square root of the impedance ratio - don't rely on DC resistance measurements. 8K:250 is 32:1, turns must be 5.6, inductance (6.6/5.6) squared or 1.385 times as much. Very close to another half octave of bass...

[Dr. Toobz]

Half an octave "aint bad" - I may rewire them after all. My feeling is that the Edcors start to roll off around 50Hz, and though they will pass a 20Hz tone to my HD650's, I have to turn up the volume to about 2 or 3x louder than average. So, the -3dB point is probably similar to that of the Specos. Treble is far cleaner, though, and they don't have that sort of shouty quality in the mids that the Specos can possess at times. Not bad for $11! Won't unseat my Crack, though, which is still the best headphone amp I've heard by far.