I'm Flipping The Switch.........

Flames1950 · Post by **Flames1950** » Sun Aug 21, 2005 9:33 pm

Well, I did say no tubes installed....but you will have to make an exception for the rectifier or you've got no B+ voltage......me bad.

Ricky Lee · Post by **Ricky Lee** » Sun Aug 21, 2005 9:37 pm

You did that on purpose! You know I kinda thought the Rect tube played a part in this, since the PT appears to supply voltage to the rectifier first.

Ricky Lee · Post by **Ricky Lee** » Sun Aug 21, 2005 10:37 pm

B+ 450 at all relative pins with Z34 installed, which will probably drop to around 405 B+ With tubes installed. I'll probably end up with around 42-43ma peak. That's typical of the 45's. I usually run them at about 42. Now to decide on what value bias resistor.

Ricky Lee · Post by **Ricky Lee** » Sun Aug 21, 2005 11:28 pm

Got real Lucky! These voltages are with the Valve Arts KT-66 valves and Rectifier tube, as well as Mullard RI 12AX7M preamp tubes installed. B+ voltage is 403. Here is the formula I used for bias calculations 17.5 / 403 volts = 43ma peak. With an 82k resistor installed my readings are 41ma & 42ma, respectfully for each valve. A 68k resistors came in at about 60ma and 100k @ 22ma. Now if they stay that way I'll be a happy camper.

Did some light to heavy picking and strumming, especially on the bass strings, below and above the 12th fret for any apparant ghosting, with none present. Experimented between the 16uf & 32uf filtering, as well. With 16uf the amp appears to have little more sag than with 32uf. Also, the 32uf has an excellent sound with almost a slight fuzz tone creaping in, which I liked very well. The amp is quiet as a mouse with no hiss or hums. So far I am very pleased with this amp and building was a walk in the park compared to the SLP's. This amp is an excellent starter kit for the newbee's. George, has done an excellent job with the instructions, this is the paint by numbers amp!

Flames1950 · Post by **Flames1950** » Mon Aug 22, 2005 11:40 pm

Those voltages are almost dead-on to what I had. I was a little scared that the 450VDC wouldn't drop as far as it did with a load in, but I'm pretty sure it was 403VDC that it settled into just like yours.
Since it's not in a head case yet I'm going to try going with 16uF on the PI instead of the 32uF next chance I get.

Ricky Lee · Post by **Ricky Lee** » Tue Aug 23, 2005 12:03 am

I' ve tried both values on the filtering and I like the 32uf a little better, just seems more responsive and string definition is a little better as well. Although no ghosting on the lower filtering, I really didn't care for the sag, which may be just the type of tunes I'm playing with. I haft to get the SLP tone out of my head to see what I really like in the filtering. I'm thinking about experimenting with a .68 cap on V2 as well, just to compare the gain. I wonder what the 47k would sound like for NFB, that might prove interesting.