Also I prefer cathode bias as to me I seem to get more bloom - think I will stick with PP for this amp. Have cathode bias on the Tweed Deluxe.
Thanks
Mike
NFB, in all my builds it is only a switching pot. Or a switch and a pot. More important on big bottle marshall amps or similar to get the crunch.
A cranked Deluxe Blackface gets loose on the bass end as I find with 6V6 tubes running high voltages and distorting.
I would do a drawing on the switch on the cap switching for v1, but I am writing on a tablet. In the back of the amp I put a 3 position switch and connect the cathode to the center and from each switching position I put a cap and resistor combination from each switch point to ground which will bias the tube differently. Position 1 is stock, position 2 I will use a 10uf and a 820 resistor and finally the 2.2uf and even lower the resistor value some.
Fargen calls this a Decade switch. The 2.2uf to 4.7 uf will remove a lot of the looseness in the bass. You can do it with as many or as few as you prefer.
I get the transformer I want from Edcor. While I mention this a lot of guys do not heavily consider a PT, but a friend who has a shop here in town, Jeff Bakos has shown me the differences a PT can make and it is a lot. Depending on the attack you want, you can consider using a PT that will help provide it. I am not using much in the way of rectifier tubes on new builds, but having one and changing to achieve different voltages is cool.
I also harvest a lot from old Hammond Tone Cabinets. You can get them cheap and the JR 20 has a really nice one and if you watch craigslist or simply stop in by older churches and ask if they have any old organ stuff around. Most still do. I got a Stromberg Carlson PA last Saturday from a church in exchange for a $20 donation. I am careful not to collect too much junk tho. I have been there too many times. No more, if I do not use it in 6 months it goes on Ebay or to a friend.
The 8 to 10K OT's are simply from the 6V6 Data sheet and I prefer lower voltages so these OT's are a better match plus the Hammond Tone Cabinets have some really nice OT's and chokes.
Bypassing the tonestack is just like picking off the signal after the plate of V1. The cap value is simply to shave some of the Bass as I do this to get the amp distorting. You can use switching here as well. Then just insert at the PI. Having a RAW will almost do the same. All you are doing is adding more resistance to the tone stack so less of the signal is attenuated.
Speaking on caps, Blue Molded .02, first coupler vibrato channel. Not the .047 in the normal channel. I am not impressed with the Sozo Blue for this place. A vintage yellow like the Jupiter or the Blue Caps Angela instruments started selling. Big sounding like the old blue molded. Not sure, but that musicap may be good here too. Anywhere the signal is, I use a nice cap. Xicon caps work well too. Have no problem with the chicklets. They are not cheap caps and I really do not now why others dont use the a lot. I built a Super Reverb for a friend and used them all the way and the amp sounds great.
And finally cathode bias does not change the amp from being Push Pull and you can keep fixed and make the cathode bias switchable. I have done it many times. Since the lower volumes that are needed, it is just an easy way to get to the goods that the 6V6 tubes have. I also prefer NOS TungSol 6V6GT's distortion, the JJ's are not as smooth but do have a lower end focus. The new TungSol I would only use in a cathode bias amp. They distort n the brittle side in a stock deluxe granted you are not going to be having as much stress on them.
I hope that answered your questions sufficiently. The tonestack bypass or raw with lowering the coupling caps at v1 will let you get very close to 6V6 Plexi especially if you do the tonestack bypass and select the best cap, but you will not have the Plexi clean which is my favorite part of the Plexi tone.
Have fun with it.
Topic: New AB763 (Deluxe Reverb) Build (Read 15880 times)