Octal Rectifiers

[titanicslim]

Hey, Gang!

I'm in a quandary. As usual. The build is an 18watt TMB EF86, and I'm using Nik's layout from the Ceriatone site.

Picked up a cheap chassis on fleaBay. Price was too good to pass up but it's got this huge hole right next to the PT, so I'm sticking an octal rectifier in it.

Well, there are a few reasons I've been wanting to try one, and the 6v tap has plenty to do in this amp, but now it's all hooked up and I am undecided about which recto tube to use. I'm getting 567v across the HT taps of the Trinity PT before hooking up the tube.

My tube box contains 5AR4s, GZ34s, 5U4s and a well-used 5Y3. I think.

And I'd be real glad to hear the opinion of an expert on the subject before I take the fateful step.

Dave

[Phil_S]

I'd vote for the GZ34/5AR4. It will give you the maximum B+, uses only 1.9A of heater current, and is much more robust than the circuit needs.

[EHansen]

+1

I'd vote for the GZ34/5AR4. It will give you the maximum B+, uses only 1.9A of heater current, and is much more robust than the circuit needs.

I used the GZ34 for my superlite TMB

[titanicslim]

Well, this is a first- It works!

Wow, first time I plug it in, nice and loud, fairly clear-both channels, too! . Hot dog! I've got to get it shielded and in a cabinet before I know what needs to be done. but it's slightly fizzy and is picking up Country Western music. Anybody know how I can bring in a Rock-N-Roll station?

I tried the GZ34 as well as a 5Y3 and honestly can't tell any difference. But, I swapped out the JJ EL84s for some of those Russian mil-spec ones- noticeable increase in loudness.

Thanks for the help, everybody!

Dave

[Phil_S]

Great news, Dave. For the RF problem, first thing is to make sure you've got a metal cover on the bottom of the chassis. Next is to change guitar cables, different brand of wire and/or different length. Third is to place a very small value cap (10-50pf) from the input jack sleeve directly to the chassis.

[titanicslim]

Great news, Dave. For the RF problem, first thing is to make sure you've got a metal cover on the bottom of the chassis. Next is to change guitar cables, different brand of wire and/or different length. Third is to place a very small value cap (10-50pf) from the input jack sleeve directly to the chassis.

Thanks, Phil. That's new to me- I also just found some Valvo EF86s I bought a while back. So I can compare with the Russian one that's in there now. Ever try those damper rings you slip over the bottle?

Dave

[zaphod_phil]

but it's slightly fizzy and is picking up Country Western music. Anybody know how I can bring in a Rock-N-Roll station?

Which channel is picking up the radio station, or is it both? Same about the fizziness - one channel only, or both?

I've tried those damper rings and they seemed to work pretty good.

[titanicslim]

Hi Phil

Thanks for chiming in!

It's all over the thing. I'm in the process of cutting out a bottom shield, and wll get back to it after that is done. Truthfully, I want to get into it now but there has been a certain amount of liquid Memorialising done today. Sheet metal working without gloves is about as far into Stupidville as I'm going.

Dave

[titanicslim]

Which channel is picking up the radio station, or is it both? Same about the fizziness - one channel only, or both?

OK, I've had a chance to work on it some more. I've used just about every combination of tubes I've got and it's not much better. The signal is nice and strong, pretty impressive, really, in both channels; the fizz and crackle are still there, though the actual RF music is gone, and that's also in both the EF86 and the TMB channels with the latter actually being a little worse.

I cut out a steel bottom panel, which does no discernable good. I've tried different instrument cables as well, no change, though I have not tried the little capacitor trick- don't have one that small.

Any suggestions?

Also, should we move this thread to the Technical Discussion Forum?

Thanks,
Dave