Anybody recognize the drawing software this was made with ?

[Alf]

A couple of years ago I experimented with the ecc85 preamp tube and drew up this schematic.
Today I wanted to add some changes but can't remember what programme I made it with.
Does any made recognize the font and drawings ?



It was quite a simple programme I recollect.

[tubeswell]

You did that on a mac maybe? Looks like JSchem

[Alf]

No I didn't , it's a Windows computer , when I made it I was using windows XP.

Now I 'm using windows 7 , a new computer , and can't for the life of me remember what the programme was.

[Alf]

Don't bother anymore I found it. It was done in Jschem.

But unfortunately I will have to start again because the schematic got lost with the .jsch extension.

[Alf]

This is as far as I've got now. Doesn't sound bad but I want it cleaner. Any suggestions ?

[tubeswell]

As well as the part values, you can also label the tube types in Jschem. ;-) (Edit: okay so it says 'ECC85 Preamp' (Dur me)).

Try increasing the RK values a bit, or putting more attenuation between V1a and V1b (something like a 470k resistor between the V1a coupling cap and the vol pot's input lug ought to knock it down a bit. You may then need to think about bypassing the 470k with a smallish value cap to get the highs back into it - or you may not)

[loudthud]

For ECC85 my tube manual says 6AQ8 is equivalent. A(v) = 57. Pinout same as 12AX7 except no CT for the heater on pin 9, needs 6V from 4 to 5.

You have to get those 190V points lower, down to about half the B+ (229V). Either raise the 11K or decrease the 750 ohm.

Also, move the 47nF cap on the first stage to the plate (172V) instead of inside between the two plate load resistors.

[JoeM]

Alf,

Can you make all the part values show in a darker font? I have a hard time seeing some of the values (at least on my work monitor)

[Alf]

Thanks guys , I'm gonna try all your suggestions. First I'll make the schematic more legible !

Alf

[Alf]

This must be a lot better ?




http://i291.photobucket.com/albums/l...fal/bigger.jpg

[Alf]

reduced cathode resistor on V2

Loudthud:

You have to get those 190V points lower, down to about half the B+ (229V). Either raise the 11K or decrease the 750 ohm.

I started bringing down the cathode resistor on V2a and immediately noticed the effect
on the gain , it is now 470 ohm. The values I had in there were the result of trying to calculate them by drawing a loadline and then calculate the correct values.
(I have this book by Merlin Blencowe) but it remains hard for me.

Also, move the 47nF cap on the first stage to the plate (172V) instead of inside between the two plate load resistors.

I will go on in making your suggested changes but in small steps to hear the differences.

The cap in between the 2 resistors was done to bring down the voltage to the next stage while keeping the right total load (plate).

or putting more attenuation between V1a and V1b (something like a 470k resistor between the V1a coupling cap and the vol pot's input lug ought to knock it down a bit.

Tubeswell , there are 470 K resistors , maybe it's clearer now in the new drawing.

I'll try your suggestion of a adding a small cap ( like a Marshall preamp ?).

What I wanted to try out is if these tubes would be suitable for a preamp as they are mainly used in FM radios as oscillators. And I like NOS tubes much better than current production and these are still available at reasonable prices.
( I bough a few dozen of them some years ago)

[tubeswell]

I suggested a 470k between the V1a coupling cap and the input lug of the vol pot as well.

You could also try reducing the V1a coupling cap from 47nF to something way smaller like 1nF or 5nF. THis will knock a lot of bass flab out

[Alf]

Made some changes again; cleans up now with my les paul at vol 2 and gradually gets grainier. I like it quite a lot so far .

http://i291.photobucket.com/albums/l...pF-2012big.jpg