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The point of an 845, 211, 805 amp?
The point of an 845, 211, 805 amp?
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Old 26th June 2019, 02:47 PM   #21
dhaen is offline dhaen  Europe
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Quote:
Originally Posted by Bas Horneman View Post
Thoriated Tungsten Filaments.
So can read my newspaper
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Old 26th June 2019, 03:05 PM   #22
FullRangeMan is offline FullRangeMan  Brazil
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Quote:
Originally Posted by Bas Horneman View Post
Thoriated Tungsten Filaments.
Talking in Thorium, let me ask to the experts here how much per cent of thorium the Vintage NOS tubes had in the time of WW2 as 211,811,805,845 etc ??
Gracias
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Old 26th June 2019, 05:25 PM   #23
Tubelab_com is offline Tubelab_com  United States
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You guys and your thirsty V8s, my car is a 73 Super Beetle
And my ride for the last 10 years has been a 2008 Honda Element with a 2.4L 4 cylinder. I have been thinking about getting something newer to replace it, but can't find anything that fits my current needs better than the "toaster."
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Old 26th June 2019, 06:15 PM   #24
Bas Horneman is offline Bas Horneman  Netherlands
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So can read my newspaper
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Old 26th June 2019, 06:36 PM   #25
Tubelab_com is offline Tubelab_com  United States
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Quote:
So can read my newspaper
No need for a thoriated DHT.....just run a plain old TV sweep tube a wee bit over spec, or abuse a Chinese 6L6GC.

Although an 845 does have a much higher color temperature, better for reading......

But something's not quite right with this one....
Attached Images
File Type: jpg 6BQ6GA_cranked.jpg (279.8 KB, 377 views)
File Type: jpg 6L6_maxed.jpg (137.7 KB, 377 views)
File Type: jpg 845glow.jpg (220.1 KB, 369 views)
File Type: jpg Blue_211.jpg (172.8 KB, 373 views)
File Type: jpg DSCN7065a.jpg (64.4 KB, 371 views)
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Old 26th June 2019, 07:26 PM   #26
dhaen is offline dhaen  Europe
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I built my 845 amp about 8 years ago. At the time (and even now) I could only afford cheap Chinese valves, so I ordered 4 so had 2 spare.
It's been in almost daily use since then and I'm still on the first pair with minimal re-biasing, even though it runs in A2.
True, I have run it in low power mode for much of the time PA 80W vs 100W but it's hard to hear the difference between the settings.

What can I say about it in defence of the OP? It sounds nice. It suffers from no blocking since it has no NFB. It has no detectable hum.
My wife, who is a music lover but not an audiophile, can hear a clear difference between it and a well built chip-amp.
It warms the house in winter. I had hoped to have a class D amp finished by now to run in summer - yes I'm sensitive our energy consumption's effect to climate change.
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Old 26th June 2019, 08:59 PM   #27
DAK808 is offline DAK808  United States
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The point of an 845, 211, 805 amp?
Quote:
Originally Posted by samsdad View Post
Hello,

I’m trying to understand the point of an 845, 211, 805, etc. amplifier.

Are these amplifiers really more linear than say, a El34 ultra linear amp running in class A designed with, again, a quality circuit, parts, etc.? Is there something super special that I’m missing in an 845 SET amp (line magnetic, for example) that can’t be achieved in a 6p15 SET (Decware zen Torii, for example) plus a quality subwoofer?
Audio is not only a "numbers" game. If numbers, or specifications, or "lowest distortion" was the driving force in audio we would only be using SS amps. Obviously, there are other elements in audio reproduction that can override a strictly technical analysis. You already embrace vacuum tubes which technically are inferior to SS devices so why do you doubt the legitimacy of high power vintage triodes? In the final analysis we all seek something that we subjectively relate to in a way that is deeper than a technical analysis. This means that as others have related sometimes what we pursue has less to do with objectivity than personal enjoyment. One of my teachers liked to remind us that " Not all knowledge resides in one house". Obviously, not my grammar teacher.

Last edited by DAK808; 26th June 2019 at 09:03 PM. Reason: correction
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Old 26th June 2019, 09:20 PM   #28
Zoran is offline Zoran  Serbia
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To note the first post
It is not the same tubes. From the cpecs we can see that main factor for audio purposes is Ri - internal resistance of the tube. That will have huge impact for later designing the output transformer. And for a proper bandwidth offcourse
...
As the Ri is higher - as much Henrys in Primary windings it demands. For the solid low end. But next thing is that higher Lp [Hy] needs higher number of turns in primary. That will lead to increasing the capacitance, and will make issue for the opposite side of BW at highs. BUT main thing is the space to pack all turns, layers AND good isolation.
For these high Ri tubes like 211 type standard Transofmer laminations windows are just not enough. Increasing tha size of core to goal bigger space for copper layers will also increase lenght of turns, Rdc of copper wire, disturb the ratio of Magnetic lines [Lm]/gap, Lm will be longer so the gap shoud be longer too, BUT increasing tha gap we will losse Lp, induction of primary. Also Mass of Copper and mass of Iron will tend to Iron side, that will disturb the losses in Iron against tha losses in Copper... Also special techniques should be aplied for decreasing Ls, and Capacitances...
...
That is for the high Ri tubes, not so simple infact it is complicated and it is just opposite from that we can see, just one famous statements about OT "10K:8ohm"
...
The solution for OT for High Ri tubes could be to find nonstandard say EI lamination's, with larger window, same as the length of core middle "E". That is double space from standard. AND second vital thing is Permeability. Lamination's should have medium to higher relative permeability about 800. Not 250 to 400 like standard laminations. AND 0.35mm or smaller d. Without higher permability it is not posibile to acomplish huge inductance about 100Hy for the 211 for the example. In the other hand, Permeability simle should not be too high, because the core will go into DC current coming from Io of the output tube, into saturation more quickly... Again increasing the GAP we can decrease DC core saturation BUT we will loose the Primary inductance...
...
Sorry for the longer post.
From the specs, I think that 845 have the smaller Ri from other tubes in the list, and it is easier to mount OT for wider BW and smaller Phase shift at the edges of the BW.
...
Somebody can make comparative datas between Ri in typical working points for listed tubes?
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Old 26th June 2019, 09:41 PM   #29
scobham is offline scobham  United Kingdom
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Well samsdad I can give you the main point. They sound fantastic. Over the years I have built 4 or 5 different topologies from 6550, 300B, EL34 some in Ultralinear
PP some in single ended. I can confidently say my 845
SE wipes the floor with all of the proceeding designs based on other tubes in terms of sheer musical enjoyment. Just cap coupled all the way until the output iron. Is is more linear than the rest? The hell if I know as I have never bothered to measure - I just used my ears. (I also have all the bits to make a GM70 SE amp but have never managed to summon up the energy to get round to building another boat anchor. ��).

Whilst measurements are necessary to validate good basic operation of an amp at the end of the day it's more important that it sounds good to you - after all that's the whole point isn't it?
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Old 26th June 2019, 10:39 PM   #30
Wavebourn is offline Wavebourn  United States
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The point of an 845, 211, 805 amp?
The point olf using triodes is, it is easy to copy a schematic of 1930'Th and get well sounding amplifier without the knowledge and experience of using feedbacks. The point of using transmitting triodes is possibility to drive wider range of speakers with sensitivity 90 dB / W / M or less.
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