Re: How can that work well?

Posted by mqracing (M) on January 26, 2004 at 09:56:32

In Reply to: Re: How can that work well? posted by Triode Kingdon on January 26, 2004 at 08:57:57:

TK wrote:

::::What you hear when you use a transformer without a resistive load is anyone's guess, but it's likely to include numerous anomalies that don't accurately represent the original signal.::::

Hi TK:

That statement... had me scrachting my head... and turning to some tehnical data for an input trans out of the Peerless archives....

I don't know if I agree with you or not :=)... but I hope your statement above is at least partially not true....

and the qualifier I was thinking is... do we need to look at this across some limited bandwidth.... we could argue about what that bandwidth should be....

well... let me just cite some stats and figures of a LIMITED range of tests done on one particular input trans... where they tested the unit with the secondary loaded and then unloaded.... and at two operating levels...

allow me to quote some text;

"Frequency response curves for four operating conditions, divided into two parts. The first shows response at maximum rated power level with the transformer terminated resistively and unterminated. Teh same conditions of operation are shwn in the second part except for the -60dbm level which is representative of micrphone output. Extreme performance stability is illustrated by these frequency responses taken at wildly different power leels and under two extremes of operations; that is, with open circuited secondary and with fully loaded secondary."

when you read the FR graphs... what it whous is that at max power (+8dbm) the reponse is approx down 1db at 10 hertz and aprox 2 or 2.5 db down at 100khz with the secondary loaded. Unloaded at this same power level the FR is approx -3db at 10 hz and about 5.5 or 6 db down at 100khz.

at -60dbm power level... the same response curves hold for each condition (loaded vs unloaded sec) except for visually the FR at 100khz with an unloaded secondary does seem to be down about 1db further than at full power...

but, what has me curious, is that across the audio band (say 20 hz to 20 khz) the response is essentially flat... perhaps a few tenths of a db down at close to 20 khz...

there is also a distortion graph done at +8dbm... with the secondary loaded vs the secondary unloaded... here there is a difference.... the distortion is about five times greater at 20 hz with the secondary unloaded.

Now... none of the data supplied looks at or evaluates square wave response (though the bandwidth and it's flatness of response might suggest it would probably do reasonably well) .

but... across most of the audio bandwidth (say arbitrarily 20hz to 20 khz) the unit looks reasonable from these two perspectives (FR and Distortion) whether the secondary is loaded or unloaded....

a quick note... the greater distortion of the unloaded secondary test condition at around seventy hertz subsides to approx the same level of distortion as the unit with the loaded secondary.

My hunch is that it is best to load the secondary... and I have done some listening tests (informal) btwn line outputs driven by a 6J5 wherein we loaded and then unloaded the secondary... my subjective impressions at that time was that I liked different aspects of the sound each way.... and did not find either to be conclusively "better" sounding as much as I did hear some differences in how they sounded...

but, I guess my question to you TK (in your opinion) is response characteristics and sound quality "unpredictable" if we limit the bandwidth and pick a "high quality" (however we might define this) transformer whenever the secondary is unloaded....

it's not a "set-up" question... I don't know the answer to this myself...

MSL

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Follow Ups Full Thread

Topic - input transformer loading - marnold 07:38:44 01/25/04 (43)

After all the theorising, some practical input..... - Mark Kelly 14:46:49 01/26/04 (1)

We meet again - marnold 16:48:34 01/26/04 (0)

That actually doesn't look too bad. - VoltSecond 22:26:54 01/25/04 (1)

Thanks VoltSecond - marnold 16:54:52 01/26/04 (0)

Re: input transformer loading - j.l.guillebeau@att.net 09:07:30 01/25/04 (38)

How can that work well? - Triode Kingdon 11:14:43 01/25/04 (16)

Re: How can that work well? - dave slagle 17:56:47 01/25/04 (14)

Re: How can that work well? - Triode Kingdon 20:57:20 01/25/04 (13)

Re: How can that work well? - vry 01:08:23 01/26/04 (11)

Re: How can that work well? - Triode Kingdon 07:37:07 01/26/04 (10)

Re: How can that work well? - vry 08:50:12 01/26/04 (0)

Re: How can that work well? - dave slagle 08:43:52 01/26/04 (7)

Re: How can that work well? - Triode Kingdon 08:57:57 01/26/04 (6)

Re: How can that work well? - mqracing 09:56:32 01/26/04 (1)

Re: How can that work well? - Triode Kingdon 19:26:37 01/26/04 (0)

Re: How can that work well? - vry 09:26:18 01/26/04 (3)

Re: How can that work well? - Triode Kingdon 10:59:12 01/26/04 (1)

so we load the secondary... - Sector-7G 13:31:55 01/26/04 (0)

Re: How can that work well? - mqracing 10:04:39 01/26/04 (0)

Re: How can that work well? - MQracing 08:42:18 01/26/04 (0)

very good point TK <nt> - MQracing 21:09:18 01/25/04 (0)

it worked well for me - j.l.guillebeau@att.net 12:21:47 01/25/04 (0)

Will do - marnold 10:40:17 01/25/04 (18)

Here are the pics - marnold 14:10:40 01/25/04 (17)

Well you've eliminated that.... - j.l.guillebeau@att.net 14:40:14 01/25/04 (16)

? - marnold 15:50:45 01/25/04 (15)

Choice of damping resistor.... - j.l.guillebeau@att.net 17:00:11 01/25/04 (1)

Re: Choice of damping resistor.... - marnold 20:32:30 01/25/04 (0)

you know... - Sector-7G 16:19:11 01/25/04 (12)

Will try a few - marnold 19:50:49 01/25/04 (0)

Re: you know... - Pete Fowler 18:26:33 01/25/04 (9)

Re: you know... - mqracing 09:12:48 01/26/04 (2)

Okay... - Pete Fowler 12:26:45 01/26/04 (1)

Thanks Pete.... - mqracing 13:43:15 01/26/04 (0)

A few comments. - VoltSecond 21:50:54 01/25/04 (4)

I'm familiar with those articles... - Pete Fowler 07:43:09 01/26/04 (1)

Cents off... - Pete Fowler 08:36:34 01/26/04 (0)

voltsec: these two links don't work.... - MQracing 21:55:50 01/25/04 (1)

2nd Try. - VoltSecond 22:20:46 01/25/04 (0)

Re: you know... - dave slagle 18:59:15 01/25/04 (0)

Yes, some ringing is usually normal - Triode Kingdon 17:26:01 01/25/04 (0)

Re: input transformer loading - Sector-7G 09:12:19 01/25/04 (1)

Re: input transformer loading - marnold 10:35:43 01/25/04 (0)

Follow Ups

Re: How can that work well? - mqracing 09:56:32 01/26/04 (1)

Re: How can that work well? - Triode Kingdon 19:26:37 01/26/04 (0)

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