the Blitz posted design is a balanced one, phase splitting is done at the inputs, the smaller tube there is a voltage amplifier designed to swing enough volts to drive output tube grids...
to be able to use this circuit, you will nee a preamp with balanced outputs, SY Impasse is a good one...
Tony Tecson
How did you deal with the very low input resistance with so many KT88's.
Recently I modified a Jadis with 8 X 6550's amp wired as triodes had 1 Meg on the grids tubes were going into melt down constantly the chassis was full of soot from the 10-OHM biasing resisters burning up. Was using 12AX7’s to drive the 6550’s with very low voltage
I used 47K for each 6550 and individual bias pots with a much higher voltage and used Russian 6n6’s to get sufficient drive.
I see from GEC’s circuit for KT88’s they use just two 47K resisters and two pots to adjust the bias and depend on good matching for the KT88’s
Thanks Phil
How did you deal with the very low input resistance with so many KT88's.
Recently I modified a Jadis with 8 X 6550's amp wired as triodes had 1 Meg on the grids tubes were going into melt down constantly the chassis was full of soot from the 10-OHM biasing resisters burning up. Was using 12AX7’s to drive the 6550’s with very low voltage
I used 47K for each 6550 and individual bias pots with a much higher voltage and used Russian 6n6’s to get sufficient drive.
I see from GEC’s circuit for KT88’s they use just two 47K resisters and two pots to adjust the bias and depend on good matching for the KT88’s
Thanks Phil
i adopted the carver silver 7 front-end, two sections of 12bh7 paralleled....
if i were to do that today, i will probably use the 6bq5 pentode wired as a triode in the ltp...
Jadis designs are what i call "weird" designs, i do not waste my time on them, there are far better circuits out there based on solid engineering...
since there are only two bias pots one each per channel, it is imperative that the tubes are matched octets....
kt88 and other power tubes need low grid leak resistors if we expect them to live longer...47k is also what i used, i will never use 1meg even for a 6bq5
if i were to do that today, i will probably use the 6bq5 pentode wired as a triode in the ltp...
Jadis designs are what i call "weird" designs, i do not waste my time on them, there are far better circuits out there based on solid engineering...
since there are only two bias pots one each per channel, it is imperative that the tubes are matched octets....
kt88 and other power tubes need low grid leak resistors if we expect them to live longer...47k is also what i used, i will never use 1meg even for a 6bq5
The idiocy of the Jadis design, in particular, the use of exceedingly high grid resistors on the output tubes, was well documented in Patrick Turner's pages.
yes it surely does....i frown on the triode to pentode mode switch thingy,
if you want triode, then use triode, if pentode, then use it pentode...
the switch from el34 to kt88, each tube has its own set of requirements to run them optimally....and that is the psu.
if your psu can handle the change from el34 to kt88, then why not...
Guys, are there any high-power tube PP amps here in the forum somewhere ? I mean a REAL strong thing around 1000W RMS into 8 Ohms, for driving a bass section as a monoblock alone.
I know such are mostly Class D, some AB, but all solid state.. - how about tube monsters ? (Even class AB OTL). Or any Class D tube amps here with linear PSU ?
Assuming - let's say - a handful of KT88s, or even KT150s. Or some 6C33C (6S33S), GU russian tubes, whatever.
I know such are mostly Class D, some AB, but all solid state.. - how about tube monsters ? (Even class AB OTL). Or any Class D tube amps here with linear PSU ?
Assuming - let's say - a handful of KT88s, or even KT150s. Or some 6C33C (6S33S), GU russian tubes, whatever.
You can do a search on the forum, but here is one that's referred to often:
Champ 1000 Watt Tube Amp
Champ 1000 Watt Tube Amp
Sorry to say, but this is not correct.
The second grid is grounded, so the differential pair work as a phase splitter, voltage amplifier and driver all with one tube.
The charming thing is: IF you ever want to convert is to a balanced inout, you can do this very easy by just detaching the second grid from ground and feed it with inverted inputund you are done.
I agree with the comments about the charme of using the EL34 in triode (with g3 at the anode, much better than at the cathode !!! Very different resolution and dynamics). I have prettybig speakers which need maybe 15W and two EL34 in PP is all I needed to rock the house. Important with EL34 is, that you can check their bias and adjust (I use fixed bias)...I do this always before start serious listing as I want as well that the pairs have the same current in each leg. THe more tubes, the more complex....but you have a better sounding OPT...
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