More Q's for the BOM:
1. The 2 caps for avoiding noise on the heaters (OuO1/600V) - do these really need to be 600V and what uF would you recommend?
2. Any wattage for the 100K pot on the screen supply?
3. Is 300mA ok for a B+ current rating on the PTx for the output stage?
OK,
I nearly have the thing done, might get to email it to you later on...
thanks,
Fran
1. The 2 caps for avoiding noise on the heaters (OuO1/600V) - do these really need to be 600V and what uF would you recommend?
2. Any wattage for the 100K pot on the screen supply?
3. Is 300mA ok for a B+ current rating on the PTx for the output stage?
OK,
I nearly have the thing done, might get to email it to you later on...
thanks,
Fran
1. HV ceramic discs are common, cheap, and known-good for RF bypassing. They're generally rated 600V or higher. Who am I to argue?😉 0u01 is a good, common value.
2. 1/4W or higher. It's handling about a milliamp, so that's 100mW.
3. Yes, that's fine.
2. 1/4W or higher. It's handling about a milliamp, so that's 100mW.
3. Yes, that's fine.
Thanks SY,
I was in work earlier and emailed the excel file home and the damn thing isn't here, so if theres been a prob with the outgoing server in work it'll be Monday before I email it to you....
Fran
I was in work earlier and emailed the excel file home and the damn thing isn't here, so if theres been a prob with the outgoing server in work it'll be Monday before I email it to you....
Fran
Hi SY,
-Chris
What do you expect your maximum voltage drop to be, peak? A higher wattage may be needed if you check the voltage rating on the resistor datasheet.
-Chris
anatech said:
Something like 100-150V. The trimmers I bought were surplus and don't have a datasheet. I suspect if they did have one, I'm totally abusing it. I've used this bag of 100ks in a variety of projects and haven't lost one yet. (This is all rationalization)
Well,
although I have the preamp to do yet, I started to think about layout for my RLD amp. I want the pre and RLD to match in the same size case so I need sizes for one before I build the other.
Anyway:
This is what I'm thinking of. OTX at the back either side, power Tx in the centre at 90deg to OTX and then the valves arranged basically 3 per side in an arc. Heater connections next the edge so the AC can be tucked into the chassis edges
Any comments?
See above post, I bought 4 power Tx (telefunken) on ebay a few weeks ago. 2 of them have input voltage selectors etc on them, I have the voltages figured out fine on these. The other ones (see here) I cannot figure out, not even sure of the primary! If anyone has come across the likes of these before, let me know if you got it sorted. I've shot the seller off an email too, but although it says they were tested, I don't expect much help!
Fran
although I have the preamp to do yet, I started to think about layout for my RLD amp. I want the pre and RLD to match in the same size case so I need sizes for one before I build the other.
Anyway:
An externally hosted image should be here but it was not working when we last tested it.
This is what I'm thinking of. OTX at the back either side, power Tx in the centre at 90deg to OTX and then the valves arranged basically 3 per side in an arc. Heater connections next the edge so the AC can be tucked into the chassis edges
Any comments?
See above post, I bought 4 power Tx (telefunken) on ebay a few weeks ago. 2 of them have input voltage selectors etc on them, I have the voltages figured out fine on these. The other ones (see here) I cannot figure out, not even sure of the primary! If anyone has come across the likes of these before, let me know if you got it sorted. I've shot the seller off an email too, but although it says they were tested, I don't expect much help!
Fran
That's pretty similar to my layout (it makes the grounding flow pretty naturally), so I can't complain.😉
I reckon that means I'm on the right track! 😉
To be honest though, unless you want to do something unusual with the layout, this would suggest itself straight off anyway. The avant-garde I will look at down the line, but for this project I want a traditional look.
I got a response from the ebay seller that just might sort out the Tx but I need to test it out. More later....
Fran
To be honest though, unless you want to do something unusual with the layout, this would suggest itself straight off anyway. The avant-garde I will look at down the line, but for this project I want a traditional look.
I got a response from the ebay seller that just might sort out the Tx but I need to test it out. More later....
Fran
Have you considered reversing the arc? This would put the power tubes closer to the output transformers and the input tubes further from the power transformer…John
Could do that but i think it would actually put them marginally closer to the PTx - the input tubes are at the front of the arc on each side - its impossible to see on that pic I put up.
Will have to place them out again and have a look - looks are important here too for WAF!
Fran
Will have to place them out again and have a look - looks are important here too for WAF!
Fran
Sorry for not reading through the whole thread to see if this was answered already, but given a B+2 of around 320, would you recommend using your ECC81 as a driver in a different EL84 amp, i.e. one with cathode biasing in UL? I was thinking the prototypical 6922 in LTP capacitatively coupled, but I like the idea of direct coupling...
It could work, though a bit higher B+ is better. The combo of voltage amp direct coupled to a split load gives quite a bit more gain than the LTP and is very suitable for EL84 drivers.
good for a bump to get this thread back up! Hey SY how are things going , nudge, nudge!
I have my passive pre almost done, replacement PTx on the way and nearly ready to order up and start the RLD! Hows that BOM going?
Fran
I have my passive pre almost done, replacement PTx on the way and nearly ready to order up and start the RLD! Hows that BOM going?
Fran
psu
Hi,
What do you think of using a single power transformer with 300V secondary and parallel the rectification and filter circuits for the ecc81 B+ supply and the output stage dito? In that case you can use a vacuum diode to get the 300V for el84s and silicon diodes can get you the higher 350-400V for the ecc81. What are the down sides of such arrangement?
Hi,
What do you think of using a single power transformer with 300V secondary and parallel the rectification and filter circuits for the ecc81 B+ supply and the output stage dito? In that case you can use a vacuum diode to get the 300V for el84s and silicon diodes can get you the higher 350-400V for the ecc81. What are the down sides of such arrangement?
Heat, reliability, and regulation are the weaknesses of tube rectifiers. It could still be done that way, though. However, if you use the same supply for output and driver, any bouncing of the rails because of the output stage going into AB (or worse yet, overloading) gets passed right to the driver.
A second power transformer is much cheaper, I think, than trying to do something fancy with tube rectifiers, and it will perform better, too.
A second power transformer is much cheaper, I think, than trying to do something fancy with tube rectifiers, and it will perform better, too.
forgive my ignorance,
but what about a multi tapped transformer, 0-250-275V? Does that solve the problem or is two separate transformer really superior?
but what about a multi tapped transformer, 0-250-275V? Does that solve the problem or is two separate transformer really superior?
It solves the problem and is 90% as good as a separate driver stage power transformer. But the current requirements are minimal, and suitable separate transformers can be gotten easily at surplus for a dollar or two, so why bother? Brand new units run about $12 from Allied. We're not talking about a major expenditure to do things optimally.