Hi. I'd like some input into a few mods to the 835 circuit that you can find here.
1. As I think I mention in one of my first posts over in the 50s Amp section of this forum, this amp has not grid-stoppers on the first stage 6SL7 sections. The whole purpose of grid stoppers is to bleed off radio interference, and this amp does have audible radio when the volume is turned up. It's not as bad as some other amps I've had. So, I am considering, but would like opinions.
2. The bias on the first stage of the 6SN7. The cathode resistor when I opened this amp was a 100k. Not sure why. My SPICE simulation of this amp have that section clipping quite early as the volume increases, and clipping in this amp is a Really Bad Thing. The way that the negative feedback is done in the power amp causes any clipping to get very non-linear. I've already done this, but i would like input as to replacing the 100k with a 4.7k, which is what I used on both the 6SL7 sections (they all have 100k plate resistors). My simulations suggest that this will increase the headroom of that section considerably, and the amp will stay clean pretty much up to full volume.
3. Tone stack. I've decided not to touch the tone stack at this time. I'm just curious as to whether anyone thinks that swapping in a B15 tone stack would be "desirable" in any meaningful way. It would totally change the character of the amp.
Beyond that, I don't have much on my mind. But if you are ware of some other possibilities, I'd love to hear about them. Remember that my objecting for this amp is just for it to sit in the music room next to my son's drum kit for for use when he friends over to jam. It's my only true bass amp, so I would like it to behave in a predictable way.
1. As I think I mention in one of my first posts over in the 50s Amp section of this forum, this amp has not grid-stoppers on the first stage 6SL7 sections. The whole purpose of grid stoppers is to bleed off radio interference, and this amp does have audible radio when the volume is turned up. It's not as bad as some other amps I've had. So, I am considering, but would like opinions.
2. The bias on the first stage of the 6SN7. The cathode resistor when I opened this amp was a 100k. Not sure why. My SPICE simulation of this amp have that section clipping quite early as the volume increases, and clipping in this amp is a Really Bad Thing. The way that the negative feedback is done in the power amp causes any clipping to get very non-linear. I've already done this, but i would like input as to replacing the 100k with a 4.7k, which is what I used on both the 6SL7 sections (they all have 100k plate resistors). My simulations suggest that this will increase the headroom of that section considerably, and the amp will stay clean pretty much up to full volume.
3. Tone stack. I've decided not to touch the tone stack at this time. I'm just curious as to whether anyone thinks that swapping in a B15 tone stack would be "desirable" in any meaningful way. It would totally change the character of the amp.
Beyond that, I don't have much on my mind. But if you are ware of some other possibilities, I'd love to hear about them. Remember that my objecting for this amp is just for it to sit in the music room next to my son's drum kit for for use when he friends over to jam. It's my only true bass amp, so I would like it to behave in a predictable way.