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PostPosted: 24 Dec 2018, 17:52 
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Hi Mark, That is a lot of mains voltage fluctuation. I have good power here and see less than about 1.5%. For tube heaters I usually consider +/-10% ok, however I prefer to err on the low side for longer tube life. I find that 6.0 VDC or RMS AC to be fine and use for a target voltage. If I find a circuit that goes over about 6.6 I will cut it down. I use tubes in series all the time. With modern tubes this is generally no issue as long as they are the same batch / brand / mfg date lot. Some NOS ones ...particularly very vintage ones are not as precise in construction and may not be suitable for such use. I did have some new KT120s from Tungsol that were not well matched and I had to fiddle around with several pairs to get ones that were the same voltage when in series.

Good listening
Bruce

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PostPosted: 24 Dec 2018, 18:21 
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gofar99 wrote:
Hi Mark, That is a lot of mains voltage fluctuation. I have good power here and see less than about 1.5%. For tube heaters I usually consider +/-10% ok, however I prefer to err on the low side for longer tube life. I find that 6.0 VDC or RMS AC to be fine and use for a target voltage. If I find a circuit that goes over about 6.6 I will cut it down. I use tubes in series all the time. With modern tubes this is generally no issue as long as they are the same batch / brand / mfg date lot. Some NOS ones ...particularly very vintage ones are not as precise in construction and may not be suitable for such use. I did have some new KT120s from Tungsol that were not well matched and I had to fiddle around with several pairs to get ones that were the same voltage when in series.

Good listening
Bruce

Thanks. I felt +/-10% would be OK.

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PostPosted: 10 Jan 2019, 14:52 
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I typically like spot on 6.25-6.28V DC regulated with a cheap buck converter or 6.1-6.2V AC.
Allot of listening tests shows that some tubes don't like low heater voltage eg 6v and they can never age fully to become best sounding.
Even with fully aged one must run high enough heater say at least 6.15 to get best sound but over 6.3v is very bad.

I used to used 6n4 from china at 6.3v ac but overtime it degraded though it accumulated at least 5000hours of service life at this voltage. Not as good as fresh one burnt in at 6.3v dc as the mains go past 6.3v from fluxuation and degrades.

I've been using 6v for a long time and was supprised to find tubes that had at least 1000hours will burn in even further and sound better after running at 6.3v


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PostPosted: 11 Jan 2019, 16:35 
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El Cheapo LM7806 work pretty good in most applications. Certainly no harm in tight tolerance on the circuit. For odd values of heater voltage use one of the LT108X adjustables or a LM317.

Good listening
Bruce

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PostPosted: 12 Jan 2019, 01:47 
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I used to use lm317 but I find it hard to work with, high drop out votlage and high power disipation along with bulky. This essentally becomes impracticall with higher currents and large valves.
Cheap buck boost converters lm2596 from china can handle 1.2A safely without any fans or cooling and have low drop out voltage.
Regulating from 6.3v AC supply is also possible using a buck boost one.


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PostPosted: 19 Feb 2019, 20:36 
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Hi Everyone, I gave in and reconfigured my listening area. A bit more sonic stuff, moved the electrostatics further away from the wall behind them which necessitated moving the sofa back to the far wall. Otherwise it they would be really near field things. Notice the special yellow sonic treatment devices on the fire place.

Good listening
Bruce
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Room 2019 with Yellow Sonic Improvement.jpg
Attachment:
Flip Flops.jpg


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PostPosted: 19 Feb 2019, 21:26 
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gofar99 wrote:
Hi Everyone, I gave in and reconfigured my listening area. A bit more sonic stuff, moved the electrostatics further away from the wall behind them which necessitated moving the sofa back to the far wall. Otherwise it they would be really near field things. Notice the special yellow sonic treatment devices on the fire place.

Good listening
Bruce
Attachment:
Room 2019 with Yellow Sonic Improvement.jpg
Attachment:
Flip Flops.jpg


Maybe I should have included a note with the yellow flip-flops that they are to go on your feet.

Whatever works!

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PostPosted: 20 Feb 2019, 09:42 
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Hi Mark, Oh horrors, my bad, :eek: I thought they were some of the ultra unobtanium high tech sonic wave guide dispersers. :D

Good listening
Bruce

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PostPosted: 20 Feb 2019, 16:20 
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I don’t have any sound dampening. It is our lounge room so I need to show some respect and keep the WAF high. Not sure yellow flip-flops purched on the glass top table would go over that well.

Fortunately we have heavy furniture, a thick carpet and it’s a good size room. It’s touch on the lively side but not too bad.

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PostPosted: 20 Feb 2019, 22:01 
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Hi Mark, With ESLs sound treatments are a must to control the back waves.

Good listening
Bruce

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