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going to build a 12au7 pre what do you think?

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#22
JAZZ2250 said:


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.
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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





😉
 
#23
Sch3mat1c said:


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

Tim
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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.
 
#24
Brett said:
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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Oh boy, here we go...

Tim
 

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#25
Sch3mat1c said:
Oh boy, here we go...
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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?
 
#29
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
 
#30
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."
 
#31
Differences were mostly good...and an increase in detail - not a decrease. It was a top to bottom change, with the only drawback being a plumper bass. Putting in the Bottlehead C4S's took care of that*.

You don't need to buy a new transformer, per se, just add a cheap 6v 2A tranny for the filaments.

*side note - changing the current that the CF sinks totally changes the bass response of the circuit. You could almost call it a tone control. 😉
 
#32
Filaments

Why not add a standard 9-0-9 transformer and provide regulated DC to the filaments ? Easy . I don't understand this at all

'Alot of the guys claimed it wasnt as good as the stock sounding w/12AU7's....some claimed it lost detail'

...what detail did they lose with the 6SN7 I wonder ? Considering the lower distortion (esp high order) artifacts of the 6SN7 I would think the 'detail' that was missing was perhaps the extra third , fourth , fith , sixth etc harmonic distortion that a 12AU7 generates . Sorry , just speculating but it is a possibility . Time to put the crack pipe down again

316a
 
#35
mrfeedback said:
In amongst this discussion of tube type sonics, is there anything wrong with using a higher power output tube as a preamp tube ?.

Eric.
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It would depend on the tube in question and how you operated it. IIRC, there was even a suggestion for using an SV572 as a preamp tube, and according to the report sounded quite good. The Japanese have been using things like 300Bs in preamps for years too as well as things like the 6080. So you could use a power tube as a pre.
 
#36
My favorite is an 845 based RIAA pre-amp... Japanese of course.

They run the 845 at 400 Va ... to acheive an all 845 amplifier chain. The designer believes that the 845 is sonically transparent and that when he tried other valves in front of the 845 he could hear the other valve colouring the sound - so he ended up with all 845 and lots and lots of ITs...

I like this philosophy :nod:

ciao

James
 
#37
James D. said:
My favorite is an 845 based RIAA pre-amp... Japanese of course.

They run the 845 at 400 Va ... to acheive an all 845 amplifier chain. The designer believes that the 845 is sonically transparent and that when he tried other valves in front of the 845 he could hear the other valve colouring the sound - so he ended up with all 845 and lots and lots of ITs...

I like this philosophy :nod:

ciao

James
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Build one. I'd like to see that. LCR RIAA of course.
iron = good.
 
#38
Brett said:


It would depend on the tube in question and how you operated it. IIRC, there was even a suggestion for using an SV572 as a preamp tube, and according to the report sounded quite good. The Japanese have been using things like 300Bs in preamps for years too as well as things like the 6080. So you could use a power tube as a pre.
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Hi all

I've been using a choke loaded 300b
as output on my breadboard linestage for over a year.
Sounds ok

cheers
 
#39
i have built a stock foreplay and used many 12AU7 variants. we all agreed that the Telefunken ECC302S is the best sounding in that particular circuit among all tubes we have tried.

one 6SN7-based foreplay owner who owns the Telefunken told us if he knew it will sound that good, he wouldn't have sold it.

just sharing a recent experience.
 
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