the Poor Man 660 support thread

[Nele]

[quote author="emrr"]You want to regulate a lightbulb? :razz: Keep it simple.....[/quote]
hehe, touché!
just thinking costwise it might be cheaper to regulate than to buy various 50W resistors but maybe not...

 

[cannikin]

[quote author="Nele"]
just thinking costwise it might be cheaper to regulate than to buy various 50W resistors but maybe not...[/quote]

Hell with buying a bunch of 50W Resistors.... buy yourself one of these 50W suckers and then do the test/measurements to buy the right value. You can use it with for all your future projects.....

 

[emrr]

[quote author="cannikin"][quote author="Nele"]
just thinking costwise it might be cheaper to regulate than to buy various 50W resistors but maybe not...[/quote]

Hell with buying a bunch of 50W Resistors.... buy yourself one of these 50W suckers and then do the test/measurements to buy the right value. You can use it with for all your future projects.....

[/quote]

I was thinking about those power rheostats; expensive, but good to have around for these sorts of experiments. Exactly what was used for voltage control in lots of vintage PSU's. You get back to battery powered gear in the late 1920's, and this was a front panel filament control, complete with metering.

 

[Nele]

[quote author="cannikin"]Hell with buying a bunch of 50W Resistors.... buy yourself one of these 50W suckers [/quote]

hmmm.. that's not such a bad idea.. :green:

 

[tommypiper]

[quote author="emrr"][quote author="Nele"][quote author="tommypiper"]With all those issues... Wouldn't it be easier to use a regulator?[/quote]

my thoughts as well. Why not use a 317 with a TIP2955 for instance...[/quote]

You want to regulate a lightbulb? :razz: Keep it simple.....[/quote]

Yeah, I understand it doesn't need regulating really, and the high current is a consideration.... but it might actually be simpler and easier... and avoids cooking a 50w resistor and creating all that heat and further current loss...

 

[[silent:arts]]

you could use the heater regulation scheme used in the D-AOC, but you would need one for each channel.
much more heat ...

 

[emrr]

The heat produced with a voltage drop has to go somewhere, one way or the other.

 

[Moby]

I received my PCB's today. Thanks Valker. One question now when I see schemo... How close tubes have to be matched. I read somewhere Analag's comment about but can't find it now :?

 

[[silent:arts]]

http://www.groupdiy.com/index.php?topic=341135&highlight=#341135

 

[Moby]

Thanks Volker. Do you have info about current tolerance?

 

[[silent:arts]]

[quote author="Moby"]Do you have info about current tolerance?[/quote]
let's wait for analag to answer this question

 

[analag]

[quote author="Moby"]Thanks Volker. Do you have info about current tolerance?[/quote]

Current tolerance is wide, enough to accept the average ratio of mismatch between tubes. Naturally you will buy at least twice the number of 6BC8 you will need (for replacements as well) so just average the tubes, no need to super match. You can do this by simply measuring the voltage drop across the cathode resistors.

analag

 

[flintan]

[quote author="analag"]
You can do this by simply measuring the voltage drop across the cathode resistors.
[/quote]

Approx how close is ok? Since i'm a tube noob i don't really know what to look for..

 

[Moby]

Ok, say that I will use tube emission tester. Ideal current for 6BC8 will be 10+10ma. What will be worst scenario you can accept for PM topology?

 

[emrr]

only the ears can answer this question.

 

[Moby]

[quote author="emrr"]only the ears can answer this question.[/quote]
I don't agree. I'm asking simple question because if you go more than transformer can handle there will be huge low freq loss. Of course constant current helps, but there is also limitation. I don't think that Edcors are so oversized... :roll:

 

[emrr]

I was referring to mismatch, which is already expected to be a minimal issue according to all said before here.

The units that have been built all work fine. There are response graphs posted here; did you see them? I doubt anyone sourced special 'extra current flow' tubes to test the hypothesis of high draw. Transformer overload point is an interesting question though.

The side chain amp uses the same transformer, and appears to pass a far greater signal level than the audio amp. That should be clue enough.

 

[Moby]

I'm talking about DC signal passing through transformer. If the current is different difference will saturate TX. So, I ask does Analag knows how much difference space is available with EDCOR TX. That can be easy determined by knowing the TX inductance and current flowing through. Unfortunately I still don't have transformers and want to select the tubes :? Anyway it will be good to know that details :green:

 

[mitsos]

Hi Volker,

A couple questions on the parts lists..

the Mouser 1N4007 diodes are coming up as obsolete.. Any other 1n4007 will do right?

Also, on the PM660 list, the first Wima is 220nF, but the Mouser one is listed as .022uF or 22nF right? I found 3 different MKS2 .22uF
505-MKS20.22/63/10
505-MKS2.22/63/5T
505-MKS20.22/63/5
lead spacing is 5mm for all of them.

Also, for the US peeps, Mouser is out of the big 10uF Wima, so I called TAW. They're giving me a much better price, so I'm getting all these and whatever other Wimas I need from them. Check them out.

Thanks again Volker and Analag

 

[kazper]

1N4007 is mouser #512-1N4007 and 462,464 Can Ship Immediately
Hopefully after your order there is some left over for me.