United Transformer HA-100

Hi This may help somewhat, UTC catalog does not show pinouts..I gleaned this from image that was in picture in catalog.

HA-100 is a Microphone transformer 30 -20,000Hz +- 1dB You may want to use a

There is some symmetry to the terminals. 2,3 means connected together as is 4,6. Then 50ohms is from the two sets, wire one to 2,3 and wire two to 4,6

INPUT

Output is 60,000 ohms overall split winding

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I think this transformer was used for 600/250 ohm input to the grid of a tube amp. It probably isn't going to be a good fit for a 5534. Primary 1 - pin 6 = hot side pin 2 = ct pin 4 = low side Primary 2 - pin 3 = hot side pin 5 = ct pin 1 = low side Secondary 1 - pin 7 = hot pin 9 = low Secondary 2 - pin 8 = hot pin 10 = low

bg is correct in that this transformer is a low impedance microphone-to-grid matching unit. Its turns ratio is about 1:10, meaning that if your primary line level voltage is 1VAC, then the transformer's secondary level is going to be around 10VAC (assuming the impedances allow it). I don't think that's what you're after.

Of course, you could always send the secondary into a resistive voltage divider to get the level back down so the NE5534 input isn't overdriven. Better still, connect the transformer in reverse; using the secondary as the input and the primary as the output. That would reverse the turns ratio to 10:1, so the output level would be 1/10 the input level. If you need to maintain the frequency response characteristics of the transformer, then you need to experiment with source and load impedances that the transformer sees.

A better choice would be a 1:1 ratio transformer; something like a 600:600 ohm matching transformer.

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What microphone puts out 1 volt? Millivolts is more like it.

G=B2

The OP said he had line-level audio... not a mike.

-- Dave M MasonDG44 at comcast dot net (Just substitute the appropriate characters in the address)

Life is like a roll of toilet paper; the closer it gets to the end, the faster it goes.

What microphone puts out 1 volt? Millivolts is more like it.

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I was intending to use it as a line level input, however I tried it and got nothing. Removed it and patched the line level input directly to the R/C network at the input of the first opamp and I get a very low level signal but adjusting the level pot doesn't seem to do anything. Will try the 600:600.

I was intending to use it as a line level input, however I tried it and got nothing. Removed it and patched the line level input directly to the R/C network at the input of the first opamp and I get a very low level signal but adjusting the level pot doesn't seem to do anything. Will try the 600:600.

Sounds like your opamp circuit isn't working... or not wired correctly. Is it possible for you to post a schematic of your circuit? alt.binaries.schematics.electronic is a good place to post it. If you can do ASCII art, just post it here.

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Actually I found part of the problem; was using a cutoff switch from an old parts bin and it was bad. The circuit works fine. Don't really need an input transformer at all, except the bass seems kind of thin maybe the 600:600 would correct that. I'm going to be driving an old tube amp with adjustable inputs at 50, 200 or 500 ohm - would it be advisable to use a 600:600 on the output and go into the 500 ohm tap of the tube amp's input? If I understand correctly op amps are very high impedance on the input and output.

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Actually I found part of the problem; was using a cutoff switch from an old parts bin and it was bad. The circuit works fine. Don't really need an input transformer at all, except the bass seems kind of thin maybe the 600:600 would correct that. I'm going to be driving an old tube amp with adjustable inputs at 50, 200 or 500 ohm - would it be advisable to use a 600:600 on the output and go into the 500 ohm tap of the tube amp's input? If I understand correctly op amps are very high impedance on the input and output.

A 5534 can drive a 600 ohm load to about 10 volts peak, so it might do 500 ohms with a little less head room. Keep in mind that your transformer has two identicle primaries, so you can use one as a primary and one as a secondary to make a 1 to 1 transformer. You can also use your secondaries the same way. If you make use of the center taps, you can make a 2 to 1 turns ratio. For example drive one primary with the 5534 and then use half of the other primary to drive the amps 500 ohm input. This would put alot less loading on the 5534's output providing the tube amp has enough gain. You have quite a few options with that transformer but it's hard to say how best to connect it without knowing the specifics of how much signal you need into the tube amp. Then again you could also bypass the amps input transformer??? bg

Actually I found part of the problem; was using a cutoff switch from an old parts bin and it was bad. The circuit works fine. Don't really need an input transformer at all, except the bass seems kind of thin maybe the 600:600 would correct that. I'm going to be driving an old tube amp with adjustable inputs at 50, 200 or 500 ohm - would it be advisable to use a 600:600 on the output and go into the 500 ohm tap of the tube amp's input? If I understand correctly op amps are very high impedance on the input and output.

Actually, an opamp circuit's input impedance is largely dependent on the values of the components around the opamp. The op-amp is basically a differential amplifier having a large voltage gain, very high input impedance (megohms) and low output impedance (ohms).

Consider the simple inverting amp below. The input impedance of this circuit would be Ra in parallel with Rf. The output impedance is determined by the opamp's internal characteristics. Most general purpose amps have output impedance less than 100 ohms. To get the highest peak-to-peak signal swing at the output, the opamp should be looking into 2k or more (again, highly dependent on the opamp). Your NE5534 should be able to drive the 500 ohm input, but you might not get full signal swing on the output (the NE5534 is spec'ed to drive

Using a transformer interface between your opamp circuit and the tube amp's input isn't necessary unless you have a ground loop or noise problem. The transformer (600:600) should help eliminate that. That statement would apply to the opamp's input also.

One thing to remember is that the transformer doesn't create the impedances; it just transforms them. IOW, if you have a transformer with a 1:1 turns ratio (such as the 600:600 ohm unit), then if you connect it to the opamp's output, and drive the tube amp's 50 ohm input, the opamp will see 50 ohms at its output (NOT 600 ohms). The turns ratio is the determining characteristic. The impedance spec of a signal transformer is just an approximation of the circuit impedances that it will work best in. Following up on that , if you have a transformer with a 1:10 turns ratio, and connect it between the opamp's output and the tube amp's 50 ohm input, the opamp will see a reflected impedance of 5000 ohms. Read more transformer theory at

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