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Old 20th May 2003, 01:16 AM   #21
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How so? Give me scientific reasons explaining why.

Tim
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Old 20th May 2003, 01:46 AM   #22
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Quote:
Originally posted by JAZZ2250


Are you going to use the power supply as drwan in the schematics? What transformer will you use? Hammond? I'll order one from Angela pretty soon.


i allready have the transformer not sure what the name is it kinda old but it works for now. if it turns out sounding good ill change it
i have most of the parts just no tubes yet likely in a week.


Are you going to use the power supply as drwan in theschematics? yes





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Old 20th May 2003, 02:16 AM   #23
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Quote:
Originally posted by Sch3mat1c


I always find it funny when people say this. They have the exact same curves, +/- a few mA.

Tim
As I've just got in and seen the thread, all I can do is say that I've done the measurements on a number of tubes (on an HP spec-an) as well as listened to them in circuit. For a long time I thought the 12AU7 was a good tube, until I heard and saw the difference.

Curves only give you an idea of what it's like, useful, but not definitive. It's also my inderstanding that for most of the tube era 'curves' were not even as readily available as they are now, rather most people using tabular, or linear (as in VM style) simple data. How many people in the 40/50/60's would have actually had access to a curve tracer, so there is a lot of potential for manufacturers to smudge data in their commercial interests as there was little potential to check.
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Old 20th May 2003, 03:40 AM   #24
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Quote:
Originally posted by Brett
How many people in the 40/50/60's would have actually had access to a curve tracer, so there is a lot of potential for manufacturers to smudge data in their commercial interests as there was little potential to check.
Oh boy, here we go...

Tim
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Old 20th May 2003, 04:33 AM   #25
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Quote:
Originally posted by Sch3mat1c
Oh boy, here we go...
Right, here we go. Another snide comment from Tim with no substance.

My comments based on what I was told by the engineers I first worked under, re availability of data. I was not around then to have first hand experience, but they were.

Now, as it's not hard to find any number of companies large and small today, that smudge their data for any number of commercial reasons, would you please tell me why in a huge, and often cut-throat commercial environment (even then) that they wouldn't have presented the best data possible? This data may not be the most representative, and to simply posture that because a manufacturer's published data is, well, naive. I personally don't give a bugger what the curves say, if over a number of tubes the spec-an is telling me comething different.

Also, what did a wave-analyser cost in the 40/50's? How many were around? Or a curve tracer? So who was going to do the independent analysis? Hmmmm?
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Old 20th May 2003, 07:10 AM   #26
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Just keep in mind that much of the fun and the learning is in the journey... i think i'll have to build up a 12AU7 pre just to see how it sounds ... maybe the Rosenblitz grounded grid ...

... but then i just found some 12B4s in my stash...

dave
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Old 20th May 2003, 09:48 AM   #27
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Default Re: Re: The curves don't tell the whole story

Quote:
Originally posted by Sch3mat1c


I'd try 6SN7 in my preamp but the reason I have 12AU7 in it in the first place is because it only has 600mA of heater available (the other half being used by the AU/AT/AX amp tube).

Tim
6SN7 is rated at 6.3v/600mA

7N7
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Old 20th May 2003, 11:31 AM   #28
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I had the original Foreplay circuit with 12AU7's and it sounded fine(different PSU). Swapped in 6SN7's expecting to hear subtle differences...

...not subtle.
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Old 20th May 2003, 01:12 PM   #29
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so...huge differences in a good or bad way?

I looked up 6SN7 on the bottlehead forum. Lots of word on this over there! Alot of the guys claimed it wasnt as good as the stock sounding w/12AU7's....some claimed it lost detail.

If anyone ( besides me ) wants to try it thought, you need a specific hammond transformer that can handle the increased current demands of the 6SN7. OR ( as stated above ) you can just switch to 8 pin sockets and use the 12SN7.


-Maz
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Old 20th May 2003, 01:16 PM   #30
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quoted from Paul Joppa ( designer of the foreplay ) off the Bottlehead forum :

"Hammond does make a similar transformer with a suitable filament winding, model 262E6. For new chassis, the 369AX has 2 amps of filament current available, universal primaries, and an electrostatic shield. (It has a 250vCT winding, so the power supply design is a little different.) Check their website for a local dealer, or try Antique Electronics - you may have to special order."
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