The Amp Garage

bal704 wrote:Wall wart into the LM1085 circuit, and the output to the heaters.

Why do you need to regulate the output of the wall wart?

I could see sticking a cap on it if there's some HF switching noise. But a regulator seems like overkill.

http://www.valvewizard.co.uk/heater.html I'm looking at the Valve Wizard link and see this diagram, aren't the AC and DC side here both grounded? Looks to me like only the DC side is grounded. The filter cap neg is tied to the bridge neg. So far this has been the most informative post on DC heaters...

OK, I see your point, but I thought we were talking about the CT of the winding, not either end (so notionally at a constant voltage, but accepting that nothing is perfect...). Better to leave the AC side floating, then, and elevate one of the DC legs? Yeah, elevation probably won't matter at that ...

Setting the ground/positive reference at the CT and letting the rectified side "float" will still leave a signal relationship occurring between your cathode and heater. ^ I don't follow this part, though. Well, if you measure the DC output of the rectifier/filter, it will have very little AC on it ...

My PT cathode is about 25V DC, so I'll hook the CT up to it. How about the DC side of the rectifier? Would I hook up the - output of the rectifier to the PT cathode as well to elevate it? If you tie the AC side to ground, or any voltage, via the center tap, then you must not tie the DC side to grou...

My warning was just to be sure that you don't try to set a reference on both sides of the rectifier. If you are sure that there is no ground reference on the AC side, then I would suggest setting the ground reference on the DC side, either at ground, or at some elevated level. For noise reduction, t...

Would certainly be fine for debugging. For longer term use, I would worry about how securely it could be mounted. Note that you still need to reference the heater supply to ground somehow. (This is one big pain in the butt if you try to have a mix of 6.3VAC and rectified 6VDC off the same transforme...

The "12" in the name indicates that it was designed to run on a 12 volt heater supply. But it is also center tapped, for use with typical 6 volt heater supplies. To use it with 12v, you connect to pins 4 and 5, leaving pin 9 disconnected. When run at 12v, each tube only requires 150mA. So, you could...

Find some space in your chassis to bolt one of these in. Power your 12ax7's at 12v, and never need to think about it again.

http://www.alliedelec.com/search/produc ... U=70069560

xtian wrote:So, is there DC leaking thru the valve?

Might be grid current. Maybe you're biased a bit hot? Or B+ is a bit low. Or try some other tubes.

This measurement seems odd to me. The plate supply will have a ton of ripple on it. There will be much less on the screen supply (and it will be slightly phase shifted). Any numbers that your meter shows you when comparing these two will totally depend on how your brand of meter integrates the rippl...

kin345 wrote:Many moving and packing companies are available which work on packing the products and move them to the one place to the other. You can get help from any company to move any type of products from one place to the other.

Moderator please. We have a spam-bot.

One note about a tubelab style prototyping system - there will be more noise in your prototype than in a final chassis-enclosed system, due to the bath of 60hz and RF we live in. To minimize this, you can put some sort of metal ground plane under everything. (Maybe make a cage top for it too.) If yo...

Structo wrote:http://www.tubelab.com/

The cool prototyping on the Tubelab site can be found here:
http://www.tubelab.com/The_Tubelab.htm

[img:651:492]http://www.tubelab.com/images/TL3/6AV5_amp.jpg[/img]

roberto wrote:This is what I mean.

Not sure, but shouldn't your capacitors be connected one position closer to the plate? The way you have it, I think that the upper one is just listening to B+.