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Old 4th September 2009, 07:01 AM   #61
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some of the Russian tubes being sold on Ebay as 7189A compatible
I plugged some of those into a sansui s500a and they lit up the room... I was curious. Anyway, the simple PP looks like the perfect thing to make use of the sansui OPTs. Can't wait. Thanks, dude.
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Old 4th September 2009, 01:00 PM   #62
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What kind of camera you use and your pics are so vivid and true? No flash?
The camera is a Sony DSC-F828. It is a "prosumer" model from about 5 years ago and is no longer made. I think that it is the only Sony that uses compact flash memory and it will take DVD quality video if you put a microdrive in the card slot. I do not use flash. I use a tripod and I set the camera on F8 for a good depth of field and let the camera set the exposure speed. Shots like these are taken with strong room lighting that is mostly flourescent. I often turn off most of the lights to accentuate heater / filament glow and then fix the lack of contrast in post processing. I use Nikon View software which used to be a free download for processing. It does cropping, and basic color and contrast adjustments. It also does resolution and size scaling for web page or forum size limitations.

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I still see the commercial versions (e.g. SS-5U4) of this arrangement pretty often at hamfests.
AES still has them in their catalog for $9.95. I will solder two diodes in the board in place of the tube socket (much cheaper).

Last nights picture was taken with an Antek 1T200 ($29) power transformer, and two FRED diodes B+ is about 240 volts. The outputs are two dumpster toroids that I got from some thermal label printers. I thought they were both the same since they have the same part number on them but one has 4 secondary wires, and the other has 5. One has far better bass, but the other makes more power. Both will show visible saturation effects at 20Hz on the scope, but neither distorts on seriously bass heavy music, but my lab speakers make no audible sound below 50 Hz even though the cone is moving.
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Old 4th September 2009, 09:56 PM   #63
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What do you think of the Antek AN-2T230 (230V/200VA) in the application of the 6CW5. It that overkill and too much for the tubes?

Also regarding 6CW5 tubes: any thoughts on Siemens or Motorola tubes as far as quality of construction and durability. I know those companies have decent reputations, but I know nothing about their tubes.

Thanks!
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Old 5th September 2009, 01:28 AM   #64
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I used the Antek 1T200 because I had one on the shelf. I have some 400 VA 230 volt toroidal transformers. I will get around to trying them sooner or later. The VA rating doesn't make much difference as long as it is big enough. The 230 volt secondary might raise the B+ voltage too much for the 6CW5's.

All of the 6CW5's that I have are pulls from old HP audio oscillators. I have about 8 of them here and they are all GE's. There are more in the warehouse, but they may also be GE's too.

I don't have much experience with Siemens tubes, but they do have a good reputation. Motorola never made any tubes, they had their name screened on other manufacturers tubes. I have seen RCA, GE and Sylvania tubes with the Motorola brand as well as some I couldn't identify.
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Old 6th September 2009, 02:17 AM   #65
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There are more in the warehouse, but they may also be GE's too.
I did some digging deep in my warehouse today and forun a total of 47 more 6CW5's that came from HP oscillators. All are used, most are indeed GE's. Some are "HP" branded some of them are marked "by Amperex" and "made in Gt. Britain. There are a few that are not original, replacements of various brands.

The two obvoius standouts are a pair of RCA's that are "made in Canada". These have internal structures that are much smaller that all of the others. I bet that these will glow. I also found a pair of Philips ECG tubes that look like they were made by Sylvania. The date code is 8715, near the end of vacuum tube manufacturing. I don't know what Sylvania stuffed inside the glass, but it isn't a 6CW5.

I also found 7 more of the large dumpster toroids. They all have the same part number, but there are 4 different constructions.

I brought back a pair of isolation transformers (toroids) that can be wired to put out 230 volts. Its time for some experiments.
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Old 6th September 2009, 02:54 AM   #66
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Just for fun I ordered a sleeve of 10 Siemens 6CW5's and 5 Motorolas (I'll try to see who actually made them when they arrive).

I know I am jumping the gun a bit, but am pretty excited about the prospect of building a Simple P-P, and this seemed a pretty inexpensive way to start.

I know enough to hold off on the rest since the values and specs are sure to change.

Any guess on what may work well as OT's?
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Old 6th September 2009, 01:00 PM   #67
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Any guess on what may work well as OT's?
There are dozens of possibilities and the choice comes down to budget.

6CW5's want 3000 to 3500 ohms. I am getting excellent results with some surplus guitar amp transformers that are 6600 ohms. I put an 8 ohm load on the 16 ohm tap to present a 3300 ohm load to the tubes. I have also used some power toroids with two 120 volt windings for the primary and a single 12 volt winding for the secondary. Not all power toroids will work for OPT's, so you must experiment. The power transformer is a bit harder to figure out with these tubes. The ones that I have tried like 240 to 250 volts of B+ and need at least 350 mA.

EL84's, 6BQ5's and 7189's want 6600 to 8000 ohms. Again the 6600 ohm surplus transformers work great, some rather large 6600 ohm OPT's from Handwound Electronics work good too but cost about a watt of power due to their size. I have also used a pair of the cheapest Edcors, XPP10-8-8K. They sound nice until you turn it up loud with some bass heavy music. They are only rated for 10 watts and I am extracting about 14 watts, so they distort. For $17 each you can't beat them, in fact these are probably the only new $17 OPT that you can buy. The $20 ones would likely be a better choice.
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Old 6th September 2009, 03:43 PM   #68
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I was surprised at how well a pair of XPP15-8-8K sound with 6BQ5's. I would expect the GXPP and CXPP to do even better.
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Old 6th September 2009, 05:26 PM   #69
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for the 6CW5 what would you think of the Edcor CXPP series? They have a 25W/3.4k ohm, bt it only has 4 ohm output, and they have a 30W/3.8k Ohm with 4/8/16 taps
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Old 6th September 2009, 11:45 PM   #70
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I would also note that the Edcor CXPP's are not cheap at $48-$60 each, and cheaper would be better.
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