So I should abandon the Japanese tradition such as this circuit : Japanese kt120 in triode
Focus on having a healthy class A and healthy AB and ultralinear
Focus on having a healthy class A and healthy AB and ultralinear
So...
I will keep what I have already have like circuit except maybe redo a little the input tube...
Basic building blocks :
5K Output transformer 50% UL (80W -3db 35hz), feedback around 10-15 db
Full bridge exotic diodes going to around 50-100 uf , voltage peak unknown
Power Transformer : Hammond 278X , 230ma 800vct, 5v 3A, 6.3V 6A,
Main power supply Choke Hammond 193J 200ma 10H
Bias Transformer: some small thing around 90vac can't remember
CCS negative supply transformer with dedicated heating filaments? : Hammond 262D6 120V 54ma
Thinking of regulating the power supply of input and LTP...
Input tube 6sn7gt, 4ma
ecc99 LTP with e182cc as ccs. 30ma (I know this is a lot of waste)
Voltage and parameter of output tubes: 70ma 520V
Filaments to DC or not DC that is also the question
Matching loudspeakers, 3 ways closed , 91db 1m 1v
I will keep what I have already have like circuit except maybe redo a little the input tube...
Basic building blocks :
5K Output transformer 50% UL (80W -3db 35hz), feedback around 10-15 db
Full bridge exotic diodes going to around 50-100 uf , voltage peak unknown
Power Transformer : Hammond 278X , 230ma 800vct, 5v 3A, 6.3V 6A,
Main power supply Choke Hammond 193J 200ma 10H
Bias Transformer: some small thing around 90vac can't remember
CCS negative supply transformer with dedicated heating filaments? : Hammond 262D6 120V 54ma
Thinking of regulating the power supply of input and LTP...
Input tube 6sn7gt, 4ma
ecc99 LTP with e182cc as ccs. 30ma (I know this is a lot of waste)
Voltage and parameter of output tubes: 70ma 520V
Filaments to DC or not DC that is also the question
Matching loudspeakers, 3 ways closed , 91db 1m 1v
Methinks the Hammond 193J reactor you plan to use could cause some sag on peaks, and even struggle at idle, unless you plan to use one per channel. Sorry if I missed that. I don’t know you planned PS schematic, but personally I would choose an inductor with higher current and lower inductance. Such high inductance does not buy you much with a PP amplifier, especially if you regulate the input and LTP supplies.
That circuit is pretty wild. An LM317 driving a third KT120 to bias the output tubes.
😉 looking to their webpage didn't give me much info why added the KT120... they say about some //pp el34 that the LM317 is failing due to overheat.. The reason for the LM317 is to only allow class A output.
This original circuit only had the LM317, they added the KT120 later, no explanation.
This original circuit only had the LM317, they added the KT120 later, no explanation.
Hello to everyone following this, I don't think I will build a triode or non-feedback amplifier.
I am very tempted to build it pentode with cathode feedback which my transformer allows.
I copied a schematic from a defunct website called novotone.be (it is in french), amplifier project #33 which is currently driving my EL34 amplifier without any complaint.
I plan to use this circuit instead of the LTP. I will also post my construction a little bit and share what I learn during and after this experience of building an amplifier which has a lot of what I learned from diy audio.
I am very tempted to build it pentode with cathode feedback which my transformer allows.
I copied a schematic from a defunct website called novotone.be (it is in french), amplifier project #33 which is currently driving my EL34 amplifier without any complaint.
I plan to use this circuit instead of the LTP. I will also post my construction a little bit and share what I learn during and after this experience of building an amplifier which has a lot of what I learned from diy audio.
I will only post the schematic after it works as intended, but meanwhile I can show that I took all my ideas and schematics on the available web.
with the schematic of novotone, gain is 63x , with kt120 and Cathode follower the gain of output stage is 9x, I guess the total gain is multiplying both values , which is equal 63*9= 567 . (55db)
I don't know how much feedback is available, a power amp needs around 27 db of gain ? I am not sure how to calculate anything up to this point.
with the schematic of novotone, gain is 63x , with kt120 and Cathode follower the gain of output stage is 9x, I guess the total gain is multiplying both values , which is equal 63*9= 567 . (55db)
I don't know how much feedback is available, a power amp needs around 27 db of gain ? I am not sure how to calculate anything up to this point.
I am thinking of using autobias boards however how good are they to get rid of grid current? It doesn't mention it anywhere on websites of vendors
Anyways, I am going to use that design instead of the more used traditional LTP etc, I know it sounds wonderful, however here I know already what sound I can get from the output transformer, and if in the worst case scenario the sound is not to my liking I can then change the circuit back, and even purchase another smaller transformer and experiment with transformer coupling and direct no capacitor in the signal path schematic.
With Cathode followers as drivers I don't see the point to have special bias or tracking bias, I read in many comments over the internet that automatic bias boards improved the sound etc.
It would only improve by stabilizing the core of the sensitive transformer to DC (which reduces low frequency by saturation and cause all kinds of distortion), As the transformer is built to tolerate 1ma it will be something to explore....
for the starting of the amplifier the soft start will be simply a second power switch, it is done manually and reduce the number of parts...
It is going to be built ptp on some piece of aluminum with as much dampers as possible, a steel cage will protect the top and a wood base around it, for simplicity, easy access and easy modifications.
Most of the parts are already purchased...
With Cathode followers as drivers I don't see the point to have special bias or tracking bias, I read in many comments over the internet that automatic bias boards improved the sound etc.
It would only improve by stabilizing the core of the sensitive transformer to DC (which reduces low frequency by saturation and cause all kinds of distortion), As the transformer is built to tolerate 1ma it will be something to explore....
for the starting of the amplifier the soft start will be simply a second power switch, it is done manually and reduce the number of parts...
It is going to be built ptp on some piece of aluminum with as much dampers as possible, a steel cage will protect the top and a wood base around it, for simplicity, easy access and easy modifications.
Most of the parts are already purchased...
https://novotone.be/projets/amplificateur-hybride-pp-ul-de-el34-kt77
This link above is the schematic, Basically.
The only modifications are that I use IRFPG50 N-Channel instead of BUZ80...
Some caps are not exactly the same value as well as voltages, I use a bigger choke, full wave rectifier not bridge.
Tube is KT120, obviously the grid-ground resistances are lowered 1k on the grid, 22k at entry of 50k bias pot, with 20k to ground from the bias pot. Values are approximative.
There is no complex soft start of any kind, I simply wire two switches, first one goes through a 30R , the second one bypass it and gives full power. I use this on two of my amplifiers and it worked well since 15 years.
The schematic you linked in hour post above uses small signal Mosfets. No driver tubes. I see no BUZ80 in that schematic.
In post #1 you mentioned your plans to use
The schematic you linked uses a SS front end with no tubes used. I’m confused. Please unconfuse me.
Hay, maybe it has to do with the language, the site is in French, if you click the 200W power amp the schematic project you will see what I use for driver stage.
I am not going to use the ecc99/el822 ltp, I trust more to drive with CF the output tubes.
I am not going to use the ecc99/el822 ltp, I trust more to drive with CF the output tubes.
The LM317 will not live long with 165 volts across it. Even if it could handle the voltage it will be dissipating 36.3 watts making for a large heat sink. The added tube absorbs most of the heat as the LM317 sets its cathode current, and the voltage across the chip will be whatever bias voltage it takes to get 220 mA of current through the tube in triode mode. The design is on my web site here:
http://tubelab.com/articles/circuits/ccs-circuits/
Thanks tubelab, wouldn't be great to series the lm's?
When I swapped kt77 in my UL amplifier I experienced a drop in performance at all levels, all things being equal, best bias, etc...
I read that kt77 are designed for UL however at around 450V the EL34 performs better, maybe kt77 work better at higher voltages and lower bias in pentode mode.
When I swapped kt77 in my UL amplifier I experienced a drop in performance at all levels, all things being equal, best bias, etc...
I read that kt77 are designed for UL however at around 450V the EL34 performs better, maybe kt77 work better at higher voltages and lower bias in pentode mode.