First Rocket...some questions

[davesi]

Going for the reverb version for my third build. This thing is pretty well documented here but I could use some advise to make it all that it can be. I'm using Normster's excellent layout and trying to compare the various scematics with my limited technical knowledge.

1. 1st filter supply- Using a 33 + 47 for 80 mfd. Would it be a benefit to use the 220K balancing resitors (Normster) considering the differing values for these caps? I've read that these slso function as bleeders. Are bleeders neccessary for this circuit?

2. Grounding- Pretty much per plan: PT taps at Mains earth ground; B+1 & B+2 at 5AR4 socket; B+3 - B+5 & grid leaks at star by Cut control. Now the questions. Does the board buss wire get grounded anywhwere but the controls and board? Some are shown connected at Cut control star ground, others not connected anywhere else, and I think I've seen one connected at input jack point. I stared planning on isolated input jack with buss wire and jack connected at input (see 1st pic), but I don't know if this will happen. It is likely that I will go with input jack directly grounded. Can anyone offer any experinence or advise on which grounding scheme worked best for them?

As someone said earlier, I consider this one of the last good places on earth, and am very thankful and have derived much pleasure from learning from you guys. Second pic is in progress amp, controls, board and PS wiring incomplete. If anyone sees anything amiss, your comments are greatly appreciated.

Dave

[ampmike]

Looks nice Brother,I like the blue board.Everything looks neat and tidy.Keep posting your progress,Thanx Mikey

[M Fowler]

I would just run the board ground near the input.

With a GZ34 you need to limit the total filtering so I wouldn't go with the larger caps on main filtering. I believe Normster used 40-47uf there.

[davesi]

Thanks guys. Mark, that's the plan I came up with too. Hope to make some progress this weekend.

Dave

[surfsup]

Doesn't one need to limit the filtering for any tube recto? something like no greater than 60uF?

With a GZ34 you need to limit the total filtering

Besides, doesn't a tube recto provide pretty good filtering as it is?

[solderstain]

With a GZ34 you need to limit the total filtering so I wouldn't go with the larger caps on main filtering. I believe Normster used 40-47uf there.

This has always had me scratching my head when I read this here - Go look at the AA165 and AA1069 schemos for Fender Pro Reverbs - GZ34 and 5U4 rectos, respectively, and they both have two 70uf filters in series with the usual series 220k resistors paralleling them. When I built my hybrid AB165/AA864 Bassman into my Pro Reverb chassis, I built it with the 80uf caps in the first filter position like Bassmans do... and it works killer.

If GZ34s are supposed to have limited filtering, how does Fender get away with it? I'm REALLY happy with the sound of this hybrid Bassman build with tube recto...

[martin manning]

This has always had me scratching my head when I read this here - Go look at the AA165 and AA1069 schemos for Fender Pro Reverbs - GZ34 and 5U4 rectos, respectively, and they both have two 70uf filters in series with the usual series 220k resistors paralleling them. When I built my hybrid AB165/AA864 Bassman into my Pro Reverb chassis, I built it with the 80uf caps in the first filter position like Bassmans do... and it works killer.

If GZ34s are supposed to have limited filtering, how does Fender get away with it? I'm REALLY happy with the sound of this hybrid Bassman build with tube recto...

Two 70uF in series makes 35uF. Two 80uF in series is 40uF. The spec sheets for GZ34 say 60uF is maximum (to limit peak current), but exceeding that by some amount (two 40uF are shown in parallel for 80uF in the Rocket schematic) probably only means a little reduction in life.

[davesi]

Appreciate the comments. I was concerned about that 1st filter supply when researching this amp too, but wanted to stay as close as possible to the schematic values since this amp gets such rave reviews. After consulting with a well known tube vendor, he recommended a NOS Slyvania 5R4 (on left, mis-labeled 5V4) or mullard for this amp. After I ordered tubes, I found the tube on the right in my box. GZ34 GT BRITTAIN, f32 B4H1... a 1964 Blackburn Mullard! I pulled this from a Blackface Tremolux at least fifeteen years ago, so I think I may be OK. In an effort to keep the mains filtering at 80, I planned to parallel the 33 and 47 on the left (47 on right is B+2). Is there any downside to achieving 80 uf this way? Balance resistors?

Dave

[martin manning]

No problem paralleling two different values. Since they are in parallel, they will see exactly the same the same voltage. Balance resistors are only needed for a series connection.

[davesi]

Thanks Martin.

[solderstain]

Two 70uF in series makes 35uF. Two 80uF in series is 40uF. The spec sheets for GZ34 say 60uF is maximum (to limit peak current), but exceeding that by some amount (two 40uF are shown in parallel for 80uF in the Rocket schematic) probably only means a little reduction in life.

TaDa! A little theory review is always good for the soul.

Thanks!