gary sanders wrote:Would 40uf 450V caps be ok since Im using a bit less voltage?
Also, the next question is how you will you implement the bias circuit?
TM
In your reply about using at least 100uf,I will just try the original 100uf/300V cans to get it going and install new ones when the mail gets here.May give the JJ cans a try.
(This is just another one of my salvage builds where i try to make chicken salad out of chicken sh*t )
I'm not sure how the original cans were configured, but off the top of my head i'm thinking that you better make sure that the outside of the can is isolated from the chassis.
Man I sure read that ( 244V ) wrong.From chassis ground to HT its 484V! Glad I didnt stick my tongue to it! I was reading it from the negative end of the first cap in the divider so I guess thats the halfway point.Im good with 484.Thats what the 7868s need.
Heres what I ended up using
Now to get the 12V heater supply to 6.3........
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Just curious, but you know this design will need about 350Ma, right?
Granted it will put out about 90W, but current demands will be north of 300Ma.
That's 700Ma BEFORE the doubler!
I would have gone with cat bias(more current), for a more "friendly" sound.
cobalt wrote:
I would have gone with cat bias(more current), for a more "friendly" sound.
Looks good though! LOUD too.
Good luck!
weirddave
I kept the PI to the OT as it was.Its Cathode biased.Twice actually.This one is stereo!!!!! Was going to use the 25 or 29 volt tap for bias but decided against it.The power end was there so I wanted to see how it sounded with the paraphrase PIs.Heard theres some Page-ish magic there
I only used the doubler on the bogen schematic,the closest thing I could find to a 7868 based amp like this will be
Structo wrote:Well Dave did say that the power supply powered 30+ tubes, so it should be OK with a leaser amount of tubes.
On that Bogen schematic, it shows plate voltage of 460v and screen as 450, right?
Yes,465 plate and 450 screen.I have seen a few schematics from searches where they had up to 500 on them.I believe the 7868 datasheet says 550 max.
Never seen one.Will look it up.This one come out of a Conn organ.Going to maybe split up the fx loop in some cool way when I get all the basics figured out.It has been quite a challenge but I had to use it just to see if I could figure it out.Still havent ruled out tossing the two OT's and running the 7868s as a quad.90 watts sounds nice
)
