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Bogner Shiva tubes

Robzilla

Member
Messages
183
Hi guys,

I have a question regarding my old-version Bogner Shiva EL34. I bought the amp more than a year ago secondhand and it is time to change my tubes. The Bogner site states i should only use the SED powertubes. Does this mean i can just drop them in and forget about biasing? How much difference is there between the SED tubes and why should i bias if i'm using the same type of tubes?

Please explain!
 

GT100

Member
Messages
4,126
Hi guys,

I have a question regarding my old-version Bogner Shiva EL34. I bought the amp more than a year ago secondhand and it is time to change my tubes. The Bogner site states i should only use the SED powertubes. Does this mean i can just drop them in and forget about biasing? How much difference is there between the SED tubes and why should i bias if i'm using the same type of tubes?

Please explain!
Bogner is flat out wrong on this -ask around.
Every time you change power tubes (same brand or not) you should in the very least check where the tubes are idling. Odds are that you need to tweak the bias. Maybe in the old days if you were using a certain tube by a top maker you could to a certain degree get away with this -even then your tubes weren't "dialed in". Today tubes vary widely meaning even the same tube from the same manufacture could need a significantly different bias voltage than another.
If you don't check (and adjust if necessary) you risk smoking your tubes and possibly more.
The other possibility is that the amp doesn't sound it's best...
 

twangbanger

Member
Messages
1,496
Bogner is flat out wrong on this -ask around.
Every time you change power tubes (same brand or not) you should in the very least check where the tubes are idling. Odds are that you need to tweak the bias. Maybe in the old days if you were using a certain tube by a top maker you could to a certain degree get away with this -even then your tubes weren't "dialed in". Today tubes vary widely meaning even the same tube from the same manufacture could need a significantly different bias voltage than another.
If you don't check (and adjust if necessary) you risk smoking your tubes and possibly more.
The other possibility is that the amp doesn't sound it's best...
I don't think Bogner would recommend just dropping in a new set of power tubes w/out rebiasing them, that would have been the OP. I have had good luck with the SED tubes and will continue to use them in the Shiva.
 

freaksho

Member
Messages
3,998
I think Bogner recommends SED because of the unusually high voltage the tubes see in this circuit (500V+) and they determined that SED are among the sturdiest current production power tubes.

Bias should always be checked when replacing power tubes due to variations from tube to tube as a result of imperfections in manufacturing. (I don't think the OP meant to imply Bogner said biasing was unnecessary)
 

RickLee

Member
Messages
2
I think Bogner recommends SED because of the unusually high voltage the tubes see in this circuit (500V+) and they determined that SED are among the sturdiest current production power tubes.

Bias should always be checked when replacing power tubes due to variations from tube to tube as a result of imperfections in manufacturing. (I don't think the OP meant to imply Bogner said biasing was unnecessary)
I have always used a "Compu-bias " to set biasing after a tube change ... very easy to use , you don't need to be a tech and its a much safer proposition .... .. I usually just adjust biasing to about 80% of maximum "recommended" plate dissipation , ( the compu-bias has a digital read-out of wattage (dissipation) and current draw ( in MA) ..) this approach
has served me well in all the amps I have ........ was using SED's for years ,in everything including Fender 6l6's with consistent results , because of price increases I have switched to Ruby EL34BHT .. these have the ability to run at the high plate currents , have had good results with these ... so far a great inexpensive tube .. use these also in my Rivera Chubster .. very punchy ..
 

GT100

Member
Messages
4,126
Bogner is flat out wrong on this -ask around.
Every time you change power tubes (same brand or not) you should in the very least check where the tubes are idling. Odds are that you need to tweak the bias. Maybe in the old days if you were using a certain tube by a top maker you could to a certain degree get away with this -even then your tubes weren't "dialed in". Today tubes vary widely meaning even the same tube from the same manufacture could need a significantly different bias voltage than another.
If you don't check (and adjust if necessary) you risk smoking your tubes and possibly more.
The other possibility is that the amp doesn't sound it's best...
No, Bogner says you should only use SED tubes because they can handle the high plate Voltage of the Shiva.
They do not say to use SEDs to avoid having to rebias.

Big Difference

Lloyd
 

Classic09

Member
Messages
2,527
The Ruby EL34-BHT are specified due to the plate voltage, as were the SED's. The bonus with the SED's is they were also top quality valves. I have no experience with the Ruby Tubes but assume they'll work well.
 

dsmc80

Member
Messages
3,829
The Ruby EL34-BHT are specified due to the plate voltage, as were the SED's. The bonus with the SED's is they were also top quality valves. I have no experience with the Ruby Tubes but assume they'll work well.
I loved the =C= tubes and thankfully stocked up on a decent stash of EL34s, 6L6GCs and 6550 when I had the chance. The Ruby EL34-BHT are actually very fine tubes in their own right.
 

nicolasrivera

Platinum Supporting Member
Messages
6,820
I followed this recomendation, and to my ears the RUBYs sounded best, i also ordered match pairs of 12AX7AC5 HG+ preamp tubes for the SHIVA and a BAD CAT amp and those are perhaps the best 12AX7 i have ever tested, incredible tone and dead quiet, i dont know if it was the full change of power and preamp tubes but the noise was considerably lower after putting RUBYs in the Shiva and the BadCat, this was not a manth long ago so i can fully recomend those tube.
 




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