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Post subject: Dummy Plug to quiet the HRD
Posted: Sun Nov 04, 2012 8:41 am
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So as not to risk HJ the "I castrated my Twin today" thread, I thought it would be best to start a new one.

in the original thread, shimmilou wrote:
... you can create an impedance mismatch by inserting a dummy plug into the external speaker jack while leaving the internal speaker plugged into its jack. This will lower the output power because you will have an 8 ohm speaker connected to the 4 ohm tap of the OT. Also, plug the guitar into input 2 as it is attenuated and you will have less volume than when using input 1. You might affect the tone of the amp by doing this, but no harm in trying it.
I recently swapped pre-amp tubes which somewhat tamed the beast in my HRD but it can still use some more taming. :wink:

A couple of questions
  • Does the Dummy Plug effectively cut the "juice" going to the HRD speaker by half and thus diminishing the "output volume"?
  • Will any 1/4" plug suffice - for example 1/8" to 1/4" headphone adapter - or is there something particular about the Dummy Plug.

Thanks and Cheers!
BM

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Post subject: Re: Dummy Plug to quiet the HRD
Posted: Sun Nov 04, 2012 10:31 am
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:lol:

Using a dummy plug into the external speaker jack of the HRDlx causes a switch to the 4 ohm tap of the OT, which creates an impedance mismatch because the 8 ohm speaker is still connected. The power reduction might not be half, but definitely less as the mismatch does not allow as much of the power developed by the tubes to be transferred to the speaker as would happen with a matched impedance.

Yes, a 1/4" to 1/8" adapter would work as a dummy plug into the external speaker jack, just don't connect anything to the adapter.

Have you tried using input 2? It is attenuated and using it will give lower volume.

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Post subject: Re: Dummy Plug to quiet the HRD
Posted: Sun Nov 04, 2012 3:45 pm
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Thanks for the feedback, Shimmilou.

After inserting the dummny plug (I used this one) and doing a double-blind test 5 times, I can say that there is a definite decrease in output volume with the dummy plug. However, the difference is very slight. I don't know what this means in terms of db, but there is a much greater difference between Input 1 and Input 2 (i.e. 6 db) than there is between Input 2 without the dummy plug and Input 2 with the dummy plug.

shimmilou wrote:
Have you tried using input 2? It is attenuated and using it will give lower volume.
Yes, this is the default input on my HRD.

Cheers!
BM

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Post subject: Re: Dummy Plug to quiet the HRD
Posted: Sun Nov 04, 2012 5:53 pm
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Yeah, even halving the power of an amp only results in a 3 db reduction, not huge but as you've discovered you get some reduction. Between the tube swap, dummy plug and using input 2, your amp should be almost silent by now. :lol:

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Post subject: Re: Dummy Plug to quiet the HRD
Posted: Sun Nov 04, 2012 7:30 pm
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shimmilou wrote:
Yeah, even halving the power of an amp only results in a 3 db reduction, not huge but as you've discovered you get some reduction. Between the tube swap, dummy plug and using input 2, your amp should be almost silent by now. :lol:
The tube swap, input 2, and the dummy plug have all helped to make the amp more quitet, but I think the tube swap has had the greatest effect. It certainly has as far as the sound of the amp goes. Really smooth, sweet, and the Drive channel is unbelievable.

As a results of things I learned recently regarding the Standby, I've been leaving my amp on instead of turning it off and have discovered that the sound gets even better after the tubes have had a good long warm-up. I don't know if there is any basis in reality here or if it's just in my head, but I swear the amp sounds better when it's been on for over an hour as opposed to a few minutes.

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Post subject: Re: Dummy Plug to quiet the HRD
Posted: Sun Nov 04, 2012 7:42 pm
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Not just in your head, it's real. All of the amp parts will warm up, including the OT. The OT will warm up even more as you play, and some amps take a while before they really warm up. Using the standby switch keeps things warm, but not as warm as when playing. Maybe that's why many times performers start off with a slower song, to let the amp really warm up before rockin' out. :idea:

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Post subject: Re: Dummy Plug to quiet the HRD
Posted: Mon Nov 05, 2012 4:43 am
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shimmilou wrote:
Not just in your head, it's real. All of the amp parts will warm up, including the OT. The OT will warm up even more as you play, and some amps take a while before they really warm up. ...
Thanks for the confirmation of sanity, shimmilou. :)

When I wrote "...the amp sounds better when it's been on for over an hour..." I should have specified that I meant playing through the amp for over an hour, not just leaving it on.

BM

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