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OPT code explanation

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I am trying to spec out the parts for a Tubelab SSE and they ask specify one of these OPT transformers.
1) Hammond 1628SEA

2) Edcor CXSE25-8-5K.


For the Edcor what do the numbers mean ?
25 = Max Watts
8 = ??
5K = ??


I like the look and price of the Edcor but I cannot find that exact model so I was shopping around for a replacement.



thanks
 
What is your output tube, amp topology, etc.? What kind of wattage are you shooting for? Would you be willing to use an output transformer that has both a 4 and an 8 Ohm tap? Would a 6 Ohm tap be close enough for both?

Keep in mind that most speakers have a minimum impedance that is 3/4 to 1/2 of the rated impedance. Those factors may either increase your choices of a good output transformer, or it may decrease your choices of a good output transformer.

If I had only one impedance choice, I would choose a 4 Ohm tap. The voltage drive from a 4 Ohm tap to the efficient Klipsch will be 70% of what it would be if you used an 8 Ohm tap on them. That would make the effective power to the Klipsch be 1/2, or -3dB versus using an 8 Ohm tap.

Also, using a 4 Ohm tap would double the damping factor to the Klipsch, versus using an 8 Ohm tap.

Hopefully that will help you to choose.
 
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Edcor CXSE25-8-5K.

The CXSE part is the Edcor series number. The 25 is the suggested maximum power rating.

From the Edcor web page, The CXSE series is for "25W single ended tube amplifier output transformers with a full frequency range of 20 to 20K Hz."

The 8 is the optimum speaker impedance and the 5K is the load impedance an 8 ohm speaker will present to the output tube.

Unfortunately there is no standard rating system for tube output transformers and many companies inflate, or just lie about their power capabilities. The power capability of an output transformer is directly related to the frequency range it operates. The low frequency (bass) capability of a transformer is determined by the amount of iron and copper is uses and weight or physical size is usually the best judge of a transformers capability. The high frequency (extreme treble) capability of the transformer is determined by the iron quality, the insulation materials, and the winding techniques used. These properties conflict with each other such that s good high powered transformer over the entire 20 Hz to 20 KHz range is hard to design and build.

I have used both the Hammond and Edcor transformers. The Edcor may give up a bit of bass to get the last octave of treble (10KHz to 20KHz) right, there the larger and heavier Hammond gives up some treble response for extended bass response.

Given those only two choices, unless you have music with 20 Hz bass and speakers capable of playing it, I would choose the Edcor unit.

There are plenty of other choices, and the usual decision factors are the sound quality, budget, and the size / weight constraints.
 
VT52com,

I put my post #5 above into a simpler and more detailed form:

Connecting the 4 Ohm Highly Inefficient KEF C-80 speakers on an 8 Ohm tap will cause three things:
1. More distortion
2. Poor damping
3. Reduced power

Connecting the 8 Ohm Efficient Klipsch bookshelf speakers on a 4 Ohm tap will cause three things:
1. Less distortion all the way up to 1/2 power
2. Better damping
3. Reduced power . . . But . . . the speaker needs less power because it is efficient.

And, putting the In-efficient KEFs on a 4 Ohm tap is the correct thing to do:
Less distortion
Better damping
More Power
(than putting the KEFs on an 8 Ohm tap)

I would choose a transformer with a 4 Ohm tap instead of an 8 Ohm tap, if I wanted to be able to drive those two types of speakers (yes, one type at a time).
 
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I believe the Hammond has 4, 8, 16 tap capabilities, but you may have to wire them one impedance at a time (no multi taps)
I am not a fan of the multi tap switches of some Hammonds, just wire them the one way you want them.

I also believe that many of the Edcore transformers can be ordered with a single specific output impedance.

I never did find out any details of the output tube, circuit, etc.
I guess I should try and find a schematic of the tubelab SSE.
 
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