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by Cressy Snr
Sun Nov 25, 2007 6:34 pm
Forum: Everyones Projects
Topic: 6AS7 Push Pull
Replies: 261
Views: 164012

On the subject of pentode constant current sinks

Does anyone have any links to articles on applying these properly to long tail pairs
I'm not having much luck finding info on the Interweb.

Steve
by Cressy Snr
Sun Nov 25, 2007 6:05 pm
Forum: Assorted Stuff
Topic: While the cat is away ....
Replies: 12
Views: 7800

One thing I know is that since Virgin took over from TeleWest my broadband speed is extremely variable, the TV pixellates at least once per day and my Internet has gone down three times in the last month for an hour at a time with no explanation, plus I was without a phone line for three days until ...
by Cressy Snr
Sun Nov 25, 2007 5:45 pm
Forum: Beginners
Topic: Going PSE.
Replies: 17
Views: 12775

SRPP? What's the world coming to? Something needs to be done about this creeping pushing and pulling behaviour before it takes over this forum. Nothing wrong with these disgusting little push-pull perverts that a damned good thrashing wouldn't sort! Bah! http://homepage.mac.com/scress1958/.Pictures/...
by Cressy Snr
Sun Nov 25, 2007 5:38 pm
Forum: Everyones Projects
Topic: 6AS7 Push Pull
Replies: 261
Views: 164012

One thing I forgot to mention is that in addition to the improved sound quality, the amp is louder for a given volume setting than it was before. I know Andrew found that this happened with his simple EL84 PP in the CCS thread.

So far it is a win-win situation with these CCSs.

Steve.
by Cressy Snr
Sat Nov 24, 2007 9:46 pm
Forum: Assorted Stuff
Topic: A little giggle!
Replies: 9
Views: 7371

martin213 wrote:[

Now who sang that dreadful 'pop' song,"i'm living in a box,living in a cardboard box"? :shock:
Living in a Box of course.
Where were you in the '80s Martin? 8)
by Cressy Snr
Sat Nov 24, 2007 4:37 pm
Forum: Everyones Projects
Topic: 6AS7 Push Pull
Replies: 261
Views: 164012

Right, I've been doing quite a lot of modifying this week, playing with LM317s as constant current sinks for the input and driver stages. Taking advantage of the flat loadlines generated by the CCSs I took the opportunity to reduce the current passing through both stages. The 6SN7s and 6SL7s both ha...
by Cressy Snr
Sat Nov 24, 2007 12:22 pm
Forum: Everyones Projects
Topic: CCS rules supreme!
Replies: 31
Views: 20828

In a word Philip.......yes Or..... you could peruse the characteristics for the 834, look for a current draw that will give the max linearity and use that by recalculating the resistor value. Don't get hung up over voltages. (Nick cured me of that one a few months ago) Bias current is the important ...
by Cressy Snr
Sat Nov 24, 2007 12:35 am
Forum: Everyones Projects
Topic: CCS rules supreme!
Replies: 31
Views: 20828

Hi Nick, That's one way around it. :D One of the many good things I found when using the LM317s as CCSs in the input and driver long-tail pairs has been the fact that the perfect balance obtained has killed most of the power supply noise stone dead. Once the power stage is sorted I'm fairly confiden...
by Cressy Snr
Fri Nov 23, 2007 11:47 am
Forum: Everyones Projects
Topic: CCS rules supreme!
Replies: 31
Views: 20828

Steve: At 70v I would have thought you were in the range of a pentode CCS? Hi Nick Forgot about how good pentodes are at CCS duties. Should be no problem implementing a pair of pentodes as CCSs on the output valves. A couple of EL34s will handle the current very nicely and at zero additional cost, ...
by Cressy Snr
Thu Nov 22, 2007 10:23 pm
Forum: Everyones Projects
Topic: CCS rules supreme!
Replies: 31
Views: 20828

Thanks Andrew, After a bit of searching I managed to find a nice regulator that could also be used. The Texas Instruments TL783 high voltage regulator is rated at 125V and 700mA; available from Farnell. This is ideal for low voltage/high current regulator triodes being used as output devices. Great ...
by Cressy Snr
Thu Nov 22, 2007 9:32 pm
Forum: Everyones Projects
Topic: CCS rules supreme!
Replies: 31
Views: 20828

Now then lads All I need to find is a regulator that is happy to drop 70V at 100mA to balance up my 6AS7 output valves. I recently put those "lazyman" CCSs in both my voltage amp and driver stages and got a very useful improvement in bass definition and clarity. Just the output stage to do...
by Cressy Snr
Tue Nov 20, 2007 7:00 pm
Forum: Assorted Stuff
Topic: A little giggle!
Replies: 9
Views: 7371

Yes that was me. 13 years ago with the Linn pretek/powertek and LP12 plus Index IIs. It was a nice system: very enjoyable until upgraditis set in. I was never as satisfied again until I stepped off the elevator, thousands of pounds lighter and started again with valves. I can't remember now, but if ...
by Cressy Snr
Mon Nov 19, 2007 1:02 pm
Forum: Beginners
Topic: Going PSE.
Replies: 17
Views: 12775

What you need to do if you want more drive is to up the HT on the driver stage to around 500V. This will give a much greater voltage swing into the EL34s than you have at the moment. EL34s are pretty powerful tubes, and knowing a bit more now, than I did when I first put the circuit together, I woul...
by Cressy Snr
Sun Nov 18, 2007 10:06 pm
Forum: Beginners
Topic: Going PSE.
Replies: 17
Views: 12775

Hi Al All I can say is I tried going PSE with the exact same circuit as you have. trouble was that although it sounded a bit more meaty, there was an accompanying hardness that pervaded the sound. This was possibly due to the high standing current being drawn by the four valves in single ended mode ...
by Cressy Snr
Sun Nov 18, 2007 11:04 am
Forum: Assorted Stuff
Topic: Share a thought
Replies: 11
Views: 8048

So sorry to hear that Philip.
My thoughts go out to Greg

Steve