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Old 2nd January 2011, 04:05 PM   #11
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Originally Posted by platplaas View Post
If I use a 10H (vs 20H) choke - would I need to adjust the value of the 220uf Capacitor?
I wouldn't bother. 10H is a pretty good amount, and so is 220uF. You should have plenty of filtering. I've had good results using a 6H choke with 120uF filter cap after it, even into efficient (>100dB) speakers.
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Old 2nd January 2011, 04:10 PM   #12
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Thank you everyone!
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Old 3rd January 2011, 12:16 AM   #13
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Would someone be able to explain the significance of the "frequency response" data on different transformers? What does this mean in real life performance / audio? Does it affect the frequency response?

e.g. From Edcor for 5k to 8ohm output trannies:
- Bottom of the line: XSE 10-8-5K, 70hz to 18khz, $17.22
- Middle of the line: GXSE 10-8-5K, 40hz to 18khz, $26.10
- Top of the line: CXSE 25-8-5K, 20hz to 20khz, $83.50
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Old 3rd January 2011, 12:25 AM   #14
6L6 is offline 6L6  United States
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This measurement is hugely important for audio.

It has to do with the frequencies that the transformers can pass.

Hi-Fi Audio frequency range is considered 20hz to 20Khz, and only the CXSE series can reproduce the entire range.

In real life the XSE will have no bass, the GXSE will have poor bass, and the CXSE will sound good, with bass as good as the circuit can pass.

In general, it's a mass thing with output transformers. Big ones are the only ones with bass.
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Old 3rd January 2011, 01:29 AM   #15
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Originally Posted by 6L6 View Post
This measurement is hugely important for audio.

It has to do with the frequencies that the transformers can pass.

Hi-Fi Audio frequency range is considered 20hz to 20Khz, and only the CXSE series can reproduce the entire range.
Transformer 'Frequency Range' is not a sharp bandpass filter situation- the response 'drops off' at the low and high end. Without a spec like '-3dB' or similar, it is impossible to tell how quickly the frequency response is dropping, and how poorly the transformer will perform. You really need a graph to tell you what's happening. And, you need to know the power level that was used during the test. Response with 1mW will look a lot better than at 10W. (One reason you can use a small OT in a headphone amp and still get decent bass...) Your low-power RH84 will be less demanding in a somewhat similar way.

What's your budget?
For info on the CSXE, and Hammond equivalent see Output Transformers
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File Type: jpg BigEdcor_FR_UL_no_FB_5Wb.jpg (79.4 KB, 510 views)
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Old 3rd January 2011, 01:31 AM   #16
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In real life the XSE will have no bass, the GXSE will have poor bass, and the CXSE will sound good, with bass as good as the circuit can pass.
I'm not buying that story. I've used the GXSE with low plate resistance DHTs, and achieved very satisfying bass. I believe that Edcor's ratings refer to the lowest frequency that will be reproduced (within 1 dB?) at full rated power. At less than full power, my experience has been that you will get good quality low frequency reproduction - even at frequencies well below the Edcor's specifications. Even if that weren't the case, 99% of the people out there simply do not have speakers capable of extending down to the 20 Hz octave anyway.

I'm not trying to discourage anyone from buying the best transformers they can afford. I'm just saying it's ridiculous to say the XSE has "no" bass, or the GXSE has "poor" bass. I'm certain my experience is not unique, and there are many other satisfied customers out there who have had good results with the X and GX line.
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Old 3rd January 2011, 01:33 AM   #17
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+1
Tubelab likes the XSE (see his webpages)
Also, I built a RH84 with good bass using guitar amp-type OTs.

John
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Old 3rd January 2011, 01:43 AM   #18
6L6 is offline 6L6  United States
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I am not implying that it is a sharp bandpass. Sorry if it came out that way.

As for the other transformers having good bass, that is a distinct possibility. My question is at what power does the, for example, XSE's 70hz roll-off occur? What happens if it is only a few milliwatts? (Which I doubt) The stated bandwdith, at full power, of the CXSE will help make sure that the bass is reproduced fully, at whatever output your amp can produce.

In my experience, I have never regretted buying "too much" output transformer. I have, however, really regretted buying small ones.
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Old 3rd January 2011, 02:12 AM   #19
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Quote:
Originally Posted by platplaas View Post
Would someone be able to explain the significance of the "frequency response" data on different transformers? What does this mean in real life performance / audio? Does it affect the frequency response?

e.g. From Edcor for 5k to 8ohm output trannies:
- Bottom of the line: XSE 10-8-5K, 70hz to 18khz, $17.22
- Middle of the line: GXSE 10-8-5K, 40hz to 18khz, $26.10
- Top of the line: CXSE 25-8-5K, 20hz to 20khz, $83.50
For any of them they are operating at such a low % of maximum design capacity (what will the RH84 produce - 3W?) that the bandwidth rating is pretty irrelevant.

Having said that, the cost difference between the G- and the bare XSE is so small, it would be a no-brainer for me - go with the GXSE...
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Old 3rd January 2011, 02:33 AM   #20
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Thank you everyone. This is now more clear.

I'm going for the GXSE model as the RH84 puts out about 3.5w.

Would the GXSE 15w model offer any advantages over the 10w model? I'm thinking not, but if the frequency performance is based on 40hz at 15w then there is more cushion for performance at 3.5w?
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