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 Post subject: GZ33 and GZ37 vs GZ34/5AR4 rectifiers
PostPosted: May Sun 10, 2015 12:33 am 
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Joined: Apr Wed 09, 2014 4:21 am
Posts: 422
I would like your thoughts. I love the big bottle GZ33 and, with a choke PS, it is (I think) rated at 300 mA and 40 uF. The GZ37 has a (silly) rated 4uF but is still considered a robust rectifier for 6550/KT88 type amps. I do not really trust the data sheets of the 33 or 37 and wonder if the vintage audio community here can add to my knowledge. Biggest question is "do either of the big bottle tubes offer any advantage over the Mullard GZ34 or Sylvania 5AR4?"

This is a NOS vintage tube question only. Scuds and silkworms - like Larry said.


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 Post subject: Re: GZ33 and GZ37 vs GZ34/5AR4 rectifiers
PostPosted: May Sun 10, 2015 4:04 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5685
Location: Rochester NY USA
Why wouldn't you trust the data sheets? They're all rated about the same, 750 mA peak repetitive current, 250 mA with cap input. Maximum cap would depend on the current limiting resistance (power transformer and other resistance before the first cap. The higher the supply voltage, the higher that resistance must be (or the cap size must be reduced) to meet the maximum current limit. The 5AR4 has the advantage of lower heater current - don't sub the others unless you know the heater winding can take 3 amps.

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 Post subject: Re: GZ33 and GZ37 vs GZ34/5AR4 rectifiers
PostPosted: May Mon 11, 2015 2:30 am 
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Joined: Apr Wed 09, 2014 4:21 am
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Why wouldn't I trust the data sheets? Have you seen a GZ37? Does not 4 uF maximum capacitor seem absurd? Did you even look?


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 Post subject: Re: GZ33 and GZ37 vs GZ34/5AR4 rectifiers
PostPosted: May Mon 11, 2015 3:02 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Rochester NY USA
The REAL limit is 750 mA peak repetitive current. With a 140 Ohm transformer, 500V and 250 mA, ALL of them should be limited to 4 uF. With lower voltage and current, higher transformer resistance, higher cap values will be fine. There is no straightforward formula to calculate peak current, but SPICE or other CAD programs make it easy these days.

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 Post subject: Re: GZ33 and GZ37 vs GZ34/5AR4 rectifiers
PostPosted: May Mon 11, 2015 3:58 am 
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Joined: Apr Wed 09, 2014 4:21 am
Posts: 422
Thanks Tom, I will look into that.


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