Max filtering for a GZ34?

James Knox

Tele-Afflicted
Joined
Aug 13, 2003
Posts
1,334
Location
Phoenix
For a 5Y3 it seems the conventional wisdom for the max “first filter” would be 30uf.

What would it be for a GZ34?

I’m not exactly sure what all the fine points of Tube Data Sheets are but am I reading this JJ GZ34 data sheet correct that max Cap limiting value is 50uf?

D43F506F-1853-4939-9F59-A7302CC3D412.jpeg
 

Nicko_Lps

Tele-Meister
Joined
Oct 10, 2021
Posts
171
Age
37
Location
Greece/Rhodes Island
For a 5Y3 it seems the conventional wisdom for the max “first filter” would be 30uf.

What would it be for a GZ34?

I’m not exactly sure what all the fine points of Tube Data Sheets are but am I reading this JJ GZ34 data sheet correct that max Cap limiting value is 50uf?

View attachment 999771
Your arrow points at F(frequency)
You can use up to 60μF according to this datasheet
 

King Fan

Poster Extraordinaire
Ad Free Member
Joined
Jan 1, 2013
Posts
8,419
Location
Salt Lake City
Poorly typeset, the units are far from the numbers. But @Nicko_Lps nailed it.

Just a note on the common misconception that the 5Y3 max is 30 or 32 uF. In virtually all 5Y3 datasheets, that number (and often lower ones, earlier) is listed as a *Typical* value. Fender for years built BF / SF Champs, VCs, and Broncos with the first 20-20 caps in the can jumpered, and lots of modern builders run 40uF. A true max is hard to source, but experts seem to feel that 47 may be a bridge too far.
 

James Knox

Tele-Afflicted
Joined
Aug 13, 2003
Posts
1,334
Location
Phoenix
Poorly typeset, the units are far from the numbers. But @Nicko_Lps nailed it.

Just a note on the common misconception that the 5Y3 max is 30 or 32 uF. In virtually all 5Y3 datasheets, that number (and often lower ones, earlier) is listed as a *Typical* value. Fender for years built BF / SF Champs, VCs, and Broncos with the first 20-20 caps in the can jumpered, and lots of modern builders run 40uF. A true max is hard to source, but experts seem to feel that 47 may be a bridge too far.
I’ve been using 40 for 5F1, GA5 and 5F2 for awhile with no probs *yet (fingers crossed).
 

King Fan

Poster Extraordinaire
Ad Free Member
Joined
Jan 1, 2013
Posts
8,419
Location
Salt Lake City
I dont know why you mention me, its what the datasheet is showing and the datasheet OP is referring to. You can read it yourself.

Sorry to give you credit... :) ...just thought you deserved it.

To be clear about my 47uF note, I was talking about the 5Y3. Good to know about the GZ34.
 
Last edited:

2L man

Tele-Afflicted
Joined
Nov 23, 2020
Posts
1,533
Age
62
Location
Finland
For that GZ34S max is 60uF but secondary resistance also has minimum value. For 2x400V each secondary half Rt should be at least 125 ohms. It they are not just install resistors to both anodes so that they come at least 125 ohms. Bit more won't hurt.

If chassis has room I recommend at least one more filter capacitor and resistor between them. Two 30uF and two 68...125 ohm between them, other to feed and other to return. It sounds like this make SE amps hum less.
 

James Knox

Tele-Afflicted
Joined
Aug 13, 2003
Posts
1,334
Location
Phoenix
For that GZ34S max is 60uF but secondary resistance also has minimum value. For 2x400V each secondary half Rt should be at least 125 ohms. It they are not just install resistors to both anodes so that they come at least 125 ohms. Bit more won't hurt.

If chassis has room I recommend at least one more filter capacitor and resistor between them. Two 30uF and two 68...125 ohm between them, other to feed and other to return. It sounds like this make SE amps hum less.
This sounds amazing, but I’m having a hard time visualizing it – what it would actually look like.
 

2L man

Tele-Afflicted
Joined
Nov 23, 2020
Posts
1,533
Age
62
Location
Finland
This sounds amazing, but I’m having a hard time visualizing it – what it would actually look like.
It is here in recent grounding thread! Third picture on OP.


Perhaps just multiple RC filters is what lessen mains hum but it is as easy to install resistors to return between electrolyts that I have done multiple RCR filters practically all my builds already last two years. Usually three to five RCR filters between rectifier and B+1 feed.

I have quit installing Chokes because they come more expensive and heavier. I have few left and when chassis has room I will use two Chokes which other comes to return current like those resistors.
 
Last edited:

James Knox

Tele-Afflicted
Joined
Aug 13, 2003
Posts
1,334
Location
Phoenix
It is here in recent grounding thread! Third picture on OP.


Perhaps just multiple RC filters is what lessen mains hum but it is as easy to install resistors to return between electrolyts that I have done multiple RCR filters practically all my builds already last two years. Usually three to five RCR filters between rectifier and B+1 feed.

I have quit installing Chokes because they come more expensive and heavier. I have few left and when chassis has room I will use two Chokes which other comes to return current like those resistors.
Thank you… I went back and read through that thread and I remember now that diagram in a previous grounding study.

So, if I am using 2 X 30uf (or a 40 and a 20) capacitors to create 60uf how do I figure out what resistors to use?
 

BenTobith

Tele-Meister
Joined
Jan 3, 2020
Posts
232
Location
Austin, Texas
It depends on how fond you are of the GZ34 tube you’re using.

Is it an old Mullard? I probably wouldn’t go over 32uF. Maybe 40–48uF if you’re feeling ambitious.

The other factor to consider: Does your amp have Standby, and especially the old, horrifying, tube-destroying Standby design made popular by Fender, Marshall, etc.? If so, and you also want to push the filtering to the edge, that’s double trouble.
 

mountainhick

Tele-Meister
Joined
May 2, 2021
Posts
418
Age
64
Location
Rocky Mountains
Thank you… I went back and read through that thread and I remember now that diagram in a previous grounding study.

So, if I am using 2 X 30uf (or a 40 and a 20) capacitors to create 60uf how do I figure out what resistors to use?

Two variables in terms of desired outcome, what supply voltage are you shooting for, and what are the RC filter cutoff figures. I've found this calculator helpful: https://www.ampbooks.com/mobile/amplifier-calculators/RC-ripple-filter/calculator/

Larger cap values lower the RC cutoff and increase amount of LF attenuation. Larger resistors crate more voltage drop and also increase LF attenuation (ripple/hum)
 

Dennis Perusse

Tele-Meister
Joined
May 12, 2011
Posts
253
Location
Amesbury Mass
For Gz34 it is around 60 uf max depending on age, brand, datasheet specs, and how the circuit is set up. Where you were also mentioning a 5y3 it can range from 10 uf to 20 uf depending on datasheet. Now I've seen a stereo hi fi setup that has a 5y3gt setup at 40 uf but I think that it was split amongst the two channels.
 

2L man

Tele-Afflicted
Joined
Nov 23, 2020
Posts
1,533
Age
62
Location
Finland
Yep, that’s what I decided to do. I’ll be using a JJ GZ34 and “make it take it”.
Just measure PT secondary resistances that it is high enough. Modern electrolyts internal resistance can be very low and both together the rectifier peak current might come too high?
 




Top