Talk:Constant-voltage speaker system

Good online references

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— Preceding unsigned comment added by Scottywong (talk • contribs) 14:47, October 12, 2007‎

Transformer as a High-Pass Filter

To 129.55.27.4, who changed the transformer information: Transformers do not act as lowpass filters. They block DC voltages. 70V transformers result in a lack of low frequency information. High frequency information is not affected. Revision undone. 74.92.147.125 (talk) 19:17, 26 March 2008 (UTC)

Actually, you're both right. Real transformers have a bandpass transfer function. Both high and low frequencies can be affected by an inexpensive transformer --Kvng (talk) 17:05, 22 May 2008 (UTC)

Doesn't matter how expensive or cheap the transformer is, all of them act as bandpass filters. They certainly don't pass DC, and as the input frequency gets lower and lower, their ability to track it attenuates more and more, the actual cutoff freq depending on design. Transformers used for audio typically attenuate radio frequencies (above 100,000 Hz, for instance)--transformers work marvelously well in environments that have heavy RF interference. In that regard, they are indeed lowpass filters. Binksternet (talk) 18:10, 22 May 2008 (UTC)

In the context of the range of frequencies audible to the human ear, transformers are highpass filters. If you're talking about DC to infinity, then yes, transformers are bandpass filters. However, there is no transformer that acts as a lowpass filter in any context. Snottywong (talk) 20:29, 29 May 2008 (UTC)

I've used transformers innumerable times to reduce in-band (audible) noise from radio frequenc interference (RFI). That's the transformer working as a low-pass filter. I understand that very large high power transformers act as low-pass filters because of increasing self-capacitance as their physical size increases. I don't get your point about transformers not being low-pass filters in any context... Binksternet (talk) 20:47, 29 May 2008 (UTC)

Saying that a transformer acts as a lowpass filter would imply that the transformer passes DC voltages. There is no transformer that passes DC voltages. Therefore, there is no transformer that acts as a lowpass filter. However, there are transformers that act as bandpass filters (i.e. the combination of a highpass and lowpass filter). In the context of this article, however, the vast majority of transformers used for 70-volt speaker systems act as highpass filters in the audible frequency range. Since we're talking about audible frequency ranges (20Hz - 20kHz), I'm not sure why everyone is pointing out that a transformer will act as a bandpass filter because it's also acting as a lowpass at 3GHz. Snottywong (talk) 15:00, 18 July 2008 (UTC)

I said "bandpass" in my first post about it here. A bandpass is both a high pass and a low pass, of course. It's possible to discuss the highpass qualities of a bandpass filter and it's possible to discuss the lowpass qualities. In transformers, the physically largest ones attenuate audible high frequencies. The middle-sized and small ones attenuate RF frequencies in the 100k and MHz ranges which, in some cases, can affect the audible frequencies by creating problems in overly sensitive high-gain preamp circuitry such as on early Mackie 1604 mixers. The problem can also creep into a 70v system through the back end of some overly sensitive amplifiers because of the high impedance speaker lines used for constant voltage systems. A transformer fixes such problems because of its lowpass qualities. If a filter stops out-of-band frequencies that are creating an audible problem with in-band frequencies then that quality is worth mentioning. Binksternet (talk) 16:27, 18 July 2008 (UTC)

Independent verification of Crown's claims?

Is there some independent source that says Crown was the first to come up with those types of amps? I haven't seen it mentioned anywhere else. Tijfo098 (talk) 23:12, 13 September 2010 (UTC)

Do you have reason to believe that Crown's claims are false? Also, the article technically doesn't claim that Crown was "first". SnottyWong ^speak 00:01, 14 September 2010 (UTC)

I surely leads the reader to believe so, othewise why mention it? Free advertisment? Tijfo098 (talk) 02:59, 14 September 2010 (UTC)

I listed Crown's DC300 and Macrotech 2400 because they were the first I found to be able to connect to 70 and 100 volt lines, respectively. There may be others that I missed. I cannot say that Crown was first because there is no independent observer, a reliable, verifiable source who I can find making the statement. Binksternet (talk) 02:32, 14 September 2010 (UTC)

I'm guessing this qualifies as "original research" here. Perhaps the paragraph should be reworded to point out that these are early examples. I'm going to give it a shot. Tijfo098 (talk) 02:59, 14 September 2010 (UTC)

The bit does not violate WP:NOR since the main claim comes from a Crown publication. The problem which you identified is that no non-Crown source has been found to confirm the information. This is what Crown says: "As component design improved, 70V systems began to achieve high-fidelity status, but there were two weak links in the chain: the step-up and step-down transformers. Good broadband transformers that could resist core saturation and distortion were expensive. Half of this problem was solved in 1967 when Crown International introduced the DC-300. It was most likely the first high-powered low-distortion solid-state power amplifier capable of directly driving a 70V line without a step-up transformer. And in June 1987, the Macro-Tech 2400 was introduced with the capability of directly driving a 100V line. Thus, today only the loudspeaker needs a transformer to step down the voltage." I completely agree that a non-Crown source would be desirable, and if one is found to confirm or deny the Crown claims, it should be put into the article. Binksternet (talk) 03:54, 14 September 2010 (UTC)

The Crown links have died; pasting here if someone wants to salvage the second sentence of the HVTless section:

For example, in 1967, Crown International introduced the DC300 amplifier, which is capable of directly driving 70-volt lines, as well as traditional speaker loads, thanks to its overall power of 500W. In 1987, Crown introduced the Macrotech 2400, capable of driving 100-volt lines directly.

Best regards, Huw Powell (talk) 00:04, 27 May 2013 (UTC)

The guideline at Wikipedia:Link rot tells us that it is not appropriate to delete article text based only on whether the reference links are dead. I am restoring the text. Binksternet (talk) 01:32, 27 May 2013 (UTC)

You could have done better... the Crown reference guide moved to here: http://www.crownaudio.com/media/pdf/amps/138905-1_10-05_constant_voltage.pdf and I imagine the other Crown refs can also be tracked down. I'd do more right now but I am in the middle of a bit of research. (it looks like all they need is "media/" inserted before "pdf/"?) Huw Powell (talk) 21:57, 27 May 2013 (UTC)

Yes, I could have done better, but I was in a hurry. Now I have a bit of time so I will make sure the links are working. Binksternet (talk) 04:42, 28 May 2013 (UTC)

References

Broken link reference for "stacking" 70-volt transformers to get 210 volts.

This is just Ohm's law (and Faraday's) and thus rather obvious that putting 3 separate coils in series will add their voltages not counting losses, since this is identical to just having 3 times as many windings of a single coil(according to naive model ignoring again, losses for specific frequencies). The reference itself was broke and I found a new URL for the Tek Notes from that company. https://web.archive.org/web/20070206163808/http://www.audiotransformers.net/tek-notes.htm I'm not able to figure out which specific one mentions stacking them, but I did see notes of 70-volt-output on them. TN-03, seems most relevant. I need someone with more experience to verify if this was the intended set of documents. 47.221.236.73 (talk) 10:17, 8 June 2020 (UTC) A better question I forgot to mention is rather it was actually done. I can't find a reference to that.  :( 47.221.236.73 (talk) 10:18, 8 June 2020 (UTC)