Hey. There is 650V max voltage limit recommendation for KT120 in triode mode. So how about a p-p KT120 triode strapped, supplied at 600V into Ra-a 10k load, please? Thanks.

On 11/21/21 12:34, Dau Bine wrote:
> Hey. There is 650V max voltage limit recommendation for KT120 in triode mode. So how about a p-p KT120 triode strapped, supplied at 600V into Ra-a 10k load, please? Thanks.
>

are you looking for a design to build? single-ended triode config?

I think you would be better with a push-pull triode config if you want
triode final stage. And I'd suggest sticking with the reference designs
when possible. You should be able to find some online... maybe for a
different output tube but then you make little tweeks here and there for
output impedence and bias and whatnot, and voila!

also consider that when an output transformer voltage swings positive on
the plate, you can nearly double B+ voltge at the plate.

Or were you actually looking at a resistive plate load? (not recommended).

You can get inexpensive output transformers from guitar repair parts
places online - I think 'amplifiedparts.com" is one of them.

--
(aka 'Bombastic Bob' in case you wondered)

'Feeling with my fingers, and thinking with my brain' - me

'your story is so touching, but it sounds just like a lie'
"Straighten up and fly right"

Pe marți, 23 noiembrie 2021, la 23:12:29 UTC+1, Big Bad Bombastic Bob a scris:
> On 11/21/21 12:34, Dau Bine wrote:
> > Hey. There is 650V max voltage limit recommendation for KT120 in triode mode. So how about a p-p KT120 triode strapped, supplied at 600V into Ra-a 10k load, please? Thanks.
> >
> are you looking for a design to build? single-ended triode config?
>
> I think you would be better with a push-pull triode config if you want
> triode final stage. And I'd suggest sticking with the reference designs
> when possible. You should be able to find some online... maybe for a
> different output tube but then you make little tweeks here and there for
> output impedence and bias and whatnot, and voila!
>
> also consider that when an output transformer voltage swings positive on
> the plate, you can nearly double B+ voltge at the plate.
>
> Or were you actually looking at a resistive plate load? (not recommended)..
>
> You can get inexpensive output transformers from guitar repair parts
> places online - I think 'amplifiedparts.com" is one of them.
>
>
> --
> (aka 'Bombastic Bob' in case you wondered)
>
> 'Feeling with my fingers, and thinking with my brain' - me
>
> 'your story is so touching, but it sounds just like a lie'
> "Straighten up and fly right"
Hey. Thanks for the answer. I.m pretty much aware by You recommendation but this is what I have on my shelves. A kt120 matched quad, a hefty power transformer able to provide B+ 600v/1.5A and a Hammond 1650R 5k Ra-a. And I wonder if such of load is able to provide decent results for a push pull project with 4xKt120 in triode mode please. Thanks.

On 11/23/21 14:42, Dau Bine wrote:
> Pe marți, 23 noiembrie 2021, la 23:12:29 UTC+1, Big Bad Bombastic Bob a scris:
>> On 11/21/21 12:34, Dau Bine wrote:
>>> Hey. There is 650V max voltage limit recommendation for KT120 in triode mode. So how about a p-p KT120 triode strapped, supplied at 600V into Ra-a 10k load, please? Thanks.
>>>
>> are you looking for a design to build? single-ended triode config?
>>
>> I think you would be better with a push-pull triode config if you want
>> triode final stage. And I'd suggest sticking with the reference designs
>> when possible. You should be able to find some online... maybe for a
>> different output tube but then you make little tweeks here and there for
>> output impedence and bias and whatnot, and voila!
>>
>> also consider that when an output transformer voltage swings positive on
>> the plate, you can nearly double B+ voltge at the plate.
>>
>> Or were you actually looking at a resistive plate load? (not recommended).
>>
>> You can get inexpensive output transformers from guitar repair parts
>> places online - I think 'amplifiedparts.com" is one of them.
>>
>>
>> --
>> (aka 'Bombastic Bob' in case you wondered)
>>
>> 'Feeling with my fingers, and thinking with my brain' - me
>>
>> 'your story is so touching, but it sounds just like a lie'
>> "Straighten up and fly right"
> Hey. Thanks for the answer. I.m pretty much aware by You recommendation but this is what I have on my shelves. A kt120 matched quad, a hefty power transformer able to provide B+ 600v/1.5A and a Hammond 1650R 5k Ra-a. And I wonder if such of load is able to provide decent results for a push pull project with 4xKt120 in triode mode please. Thanks.
>

oh ok I think I ge4t it. I assume it's a standard 5k CT since you ar
doing triode mode. For 600V B+ at 2.5k it's about 200ma total for full
swing (100V on plate). I think a pair of KT120s in triode mode might be
able to do that. So now you just need to bias it properly. Make sure
the output transformer has sufficient power handling though, since a lot
of current could saturate the core and cause clipping and serious plate
overheating.

The data sheet is here:
https://www.thetubestore.com/lib/thetubestore/TS-KT120.pdf

According to that the triode config can go up to 230ma for a single
tube. Using a quad means less likely to fry them.

The 5k transformer would probably get you ~100W (50WRMS). So if you
wanted to max them out (as a quad) you should get a 2.5k CT output
transformer that can handle that much power. Then current will be as
high as 400ma across 1.25k (appx 500V) which is 200W (100W RMS).

you'll need a somewhat beefy driver/splitter stage - the spec says max
51k on the G1 (fixed bias) and I'm guessing you'll bias it to at least
-100V. So that's a pretty good signal (200V peak-peak) going in, driven
into a (possible) 25k load impedence.

I'd suggest something like 2 12AU7s to drive the control grids, a common
cathode amplifier plus direct coupled cathode follower for each.

12AU7 has max cathode current of 22ma. With a swing of +/- 10ma driving
a 25k load, that's 250V (more than enough signal). So thenit's just a
matter of living within the limits of the 200V heater/cathode voltage
limit (this is always a problem with direct-coupled tubes and phase
splitters). Depending on the design, you could make this work with
direct coupling the 12AU7b cathode to G1 on the KT120s. Then your fixed
bias suppply will have to tolerate up to 40ma of current swing,
regardless.

And so on.

--
(aka 'Bombastic Bob' in case you wondered)

'Feeling with my fingers, and thinking with my brain' - me

'your story is so touching, but it sounds just like a lie'
"Straighten up and fly right"

Pe miercuri, 24 noiembrie 2021, la 19:29:34 UTC+1, Big Bad Bombastic Bob a scris:
> On 11/23/21 14:42, Dau Bine wrote:
> > Pe marți, 23 noiembrie 2021, la 23:12:29 UTC+1, Big Bad Bombastic Bob a scris:
> >> On 11/21/21 12:34, Dau Bine wrote:
> >>> Hey. There is 650V max voltage limit recommendation for KT120 in triode mode. So how about a p-p KT120 triode strapped, supplied at 600V into Ra-a 10k load, please? Thanks.
> >>>
> >> are you looking for a design to build? single-ended triode config?
> >>
> >> I think you would be better with a push-pull triode config if you want
> >> triode final stage. And I'd suggest sticking with the reference designs
> >> when possible. You should be able to find some online... maybe for a
> >> different output tube but then you make little tweeks here and there for
> >> output impedence and bias and whatnot, and voila!
> >>
> >> also consider that when an output transformer voltage swings positive on
> >> the plate, you can nearly double B+ voltge at the plate.
> >>
> >> Or were you actually looking at a resistive plate load? (not recommended).
> >>
> >> You can get inexpensive output transformers from guitar repair parts
> >> places online - I think 'amplifiedparts.com" is one of them.
> >>
> >>
> >> --
> >> (aka 'Bombastic Bob' in case you wondered)
> >>
> >> 'Feeling with my fingers, and thinking with my brain' - me
> >>
> >> 'your story is so touching, but it sounds just like a lie'
> >> "Straighten up and fly right"
> > Hey. Thanks for the answer. I.m pretty much aware by You recommendation but this is what I have on my shelves. A kt120 matched quad, a hefty power transformer able to provide B+ 600v/1.5A and a Hammond 1650R 5k Ra-a. And I wonder if such of load is able to provide decent results for a push pull project with 4xKt120 in triode mode please. Thanks.
> >
> oh ok I think I ge4t it. I assume it's a standard 5k CT since you ar
> doing triode mode. For 600V B+ at 2.5k it's about 200ma total for full
> swing (100V on plate). I think a pair of KT120s in triode mode might be
> able to do that. So now you just need to bias it properly. Make sure
> the output transformer has sufficient power handling though, since a lot
> of current could saturate the core and cause clipping and serious plate
> overheating.
>
> The data sheet is here:
> https://www.thetubestore.com/lib/thetubestore/TS-KT120.pdf
>
> According to that the triode config can go up to 230ma for a single
> tube. Using a quad means less likely to fry them.
>
> The 5k transformer would probably get you ~100W (50WRMS). So if you
> wanted to max them out (as a quad) you should get a 2.5k CT output
> transformer that can handle that much power. Then current will be as
> high as 400ma across 1.25k (appx 500V) which is 200W (100W RMS).
>
> you'll need a somewhat beefy driver/splitter stage - the spec says max
> 51k on the G1 (fixed bias) and I'm guessing you'll bias it to at least
> -100V. So that's a pretty good signal (200V peak-peak) going in, driven
> into a (possible) 25k load impedence.
>
> I'd suggest something like 2 12AU7s to drive the control grids, a common
> cathode amplifier plus direct coupled cathode follower for each.
>
> 12AU7 has max cathode current of 22ma. With a swing of +/- 10ma driving
> a 25k load, that's 250V (more than enough signal). So thenit's just a
> matter of living within the limits of the 200V heater/cathode voltage
> limit (this is always a problem with direct-coupled tubes and phase
> splitters). Depending on the design, you could make this work with
> direct coupling the 12AU7b cathode to G1 on the KT120s. Then your fixed
> bias suppply will have to tolerate up to 40ma of current swing,
> regardless.
>
> And so on.
> --
> (aka 'Bombastic Bob' in case you wondered)
>
> 'Feeling with my fingers, and thinking with my brain' - me
>
> 'your story is so touching, but it sounds just like a lie'
> "Straighten up and fly right"
Hey. There is much interesting reading. Thank You Sir ! I remember doing a board experiment in the past with a pair of kt88 in triode mode at same 600v voltage into a standard Hammond 1.9k Ra-a. A ecc99 was chosen to driven by plate 8mA around. I got 33Vpk into 8 ohm resistive load, meant 68W rms without any sign of red plate from a pair of jj kt88. No global feedback used.. But was not happy with the sound. Hope a 5k OT, meant 10k per pair will make it more linear... Thanks.

Pe miercuri, 24 noiembrie 2021, la 19:29:34 UTC+1, Big Bad Bombastic Bob a scris:
> On 11/23/21 14:42, Dau Bine wrote:
> > Pe marți, 23 noiembrie 2021, la 23:12:29 UTC+1, Big Bad Bombastic Bob a scris:
> >> On 11/21/21 12:34, Dau Bine wrote:
> >>> Hey. There is 650V max voltage limit recommendation for KT120 in triode mode. So how about a p-p KT120 triode strapped, supplied at 600V into Ra-a 10k load, please? Thanks.
> >>>
> >> are you looking for a design to build? single-ended triode config?
> >>
> >> I think you would be better with a push-pull triode config if you want
> >> triode final stage. And I'd suggest sticking with the reference designs
> >> when possible. You should be able to find some online... maybe for a
> >> different output tube but then you make little tweeks here and there for
> >> output impedence and bias and whatnot, and voila!
> >>
> >> also consider that when an output transformer voltage swings positive on
> >> the plate, you can nearly double B+ voltge at the plate.
> >>
> >> Or were you actually looking at a resistive plate load? (not recommended).
> >>
> >> You can get inexpensive output transformers from guitar repair parts
> >> places online - I think 'amplifiedparts.com" is one of them.
> >>
> >>
> >> --
> >> (aka 'Bombastic Bob' in case you wondered)
> >>
> >> 'Feeling with my fingers, and thinking with my brain' - me
> >>
> >> 'your story is so touching, but it sounds just like a lie'
> >> "Straighten up and fly right"
> > Hey. Thanks for the answer. I.m pretty much aware by You recommendation but this is what I have on my shelves. A kt120 matched quad, a hefty power transformer able to provide B+ 600v/1.5A and a Hammond 1650R 5k Ra-a. And I wonder if such of load is able to provide decent results for a push pull project with 4xKt120 in triode mode please. Thanks.
> >
> oh ok I think I ge4t it. I assume it's a standard 5k CT since you ar
> doing triode mode. For 600V B+ at 2.5k it's about 200ma total for full
> swing (100V on plate). I think a pair of KT120s in triode mode might be
> able to do that. So now you just need to bias it properly. Make sure
> the output transformer has sufficient power handling though, since a lot
> of current could saturate the core and cause clipping and serious plate
> overheating.
>
> The data sheet is here:
> https://www.thetubestore.com/lib/thetubestore/TS-KT120.pdf
>
> According to that the triode config can go up to 230ma for a single
> tube. Using a quad means less likely to fry them.
>
> The 5k transformer would probably get you ~100W (50WRMS). So if you
> wanted to max them out (as a quad) you should get a 2.5k CT output
> transformer that can handle that much power. Then current will be as
> high as 400ma across 1.25k (appx 500V) which is 200W (100W RMS).
>
> you'll need a somewhat beefy driver/splitter stage - the spec says max
> 51k on the G1 (fixed bias) and I'm guessing you'll bias it to at least
> -100V. So that's a pretty good signal (200V peak-peak) going in, driven
> into a (possible) 25k load impedence.
>
> I'd suggest something like 2 12AU7s to drive the control grids, a common
> cathode amplifier plus direct coupled cathode follower for each.
>
> 12AU7 has max cathode current of 22ma. With a swing of +/- 10ma driving
> a 25k load, that's 250V (more than enough signal). So thenit's just a
> matter of living within the limits of the 200V heater/cathode voltage
> limit (this is always a problem with direct-coupled tubes and phase
> splitters). Depending on the design, you could make this work with
> direct coupling the 12AU7b cathode to G1 on the KT120s. Then your fixed
> bias suppply will have to tolerate up to 40ma of current swing,
> regardless.
>
> And so on.
> --
> (aka 'Bombastic Bob' in case you wondered)
>
> 'Feeling with my fingers, and thinking with my brain' - me
>
> 'your story is so touching, but it sounds just like a lie'
> "Straighten up and fly right"
Hey. There is much interesting reading. Thank You Sir ! I remember doing a board experiment in the past with a pair of kt88 in triode mode at same 600v voltage into a standard Hammond 1.9k Ra-a. but used as 3.8k load. A ecc99 was chosen to driven by plate 8mA around. I got 33Vpk into 8 ohm resistive load, meant 68W rms without any sign of red plate from a pair of jj kt88. No global feedback used. But was not happy with the sound. Hope a 5k OT, meant 10k per pair will make it more linear... Thanks.

Pe miercuri, 24 noiembrie 2021, la 19:29:34 UTC+1, Big Bad Bombastic Bob a scris:
> On 11/23/21 14:42, Dau Bine wrote:
> > Pe marți, 23 noiembrie 2021, la 23:12:29 UTC+1, Big Bad Bombastic Bob a scris:
> >> On 11/21/21 12:34, Dau Bine wrote:
> >>> Hey. There is 650V max voltage limit recommendation for KT120 in triode mode. So how about a p-p KT120 triode strapped, supplied at 600V into Ra-a 10k load, please? Thanks.
> >>>
> >> are you looking for a design to build? single-ended triode config?
> >>
> >> I think you would be better with a push-pull triode config if you want
> >> triode final stage. And I'd suggest sticking with the reference designs
> >> when possible. You should be able to find some online... maybe for a
> >> different output tube but then you make little tweeks here and there for
> >> output impedence and bias and whatnot, and voila!
> >>
> >> also consider that when an output transformer voltage swings positive on
> >> the plate, you can nearly double B+ voltge at the plate.
> >>
> >> Or were you actually looking at a resistive plate load? (not recommended).
> >>
> >> You can get inexpensive output transformers from guitar repair parts
> >> places online - I think 'amplifiedparts.com" is one of them.
> >>
> >>
> >> --
> >> (aka 'Bombastic Bob' in case you wondered)
> >>
> >> 'Feeling with my fingers, and thinking with my brain' - me
> >>
> >> 'your story is so touching, but it sounds just like a lie'
> >> "Straighten up and fly right"
> > Hey. Thanks for the answer. I.m pretty much aware by You recommendation but this is what I have on my shelves. A kt120 matched quad, a hefty power transformer able to provide B+ 600v/1.5A and a Hammond 1650R 5k Ra-a. And I wonder if such of load is able to provide decent results for a push pull project with 4xKt120 in triode mode please. Thanks.
> >
> oh ok I think I ge4t it. I assume it's a standard 5k CT since you ar
> doing triode mode. For 600V B+ at 2.5k it's about 200ma total for full
> swing (100V on plate). I think a pair of KT120s in triode mode might be
> able to do that. So now you just need to bias it properly. Make sure
> the output transformer has sufficient power handling though, since a lot
> of current could saturate the core and cause clipping and serious plate
> overheating.
>
> The data sheet is here:
> https://www.thetubestore.com/lib/thetubestore/TS-KT120.pdf
>
> According to that the triode config can go up to 230ma for a single
> tube. Using a quad means less likely to fry them.
>
> The 5k transformer would probably get you ~100W (50WRMS). So if you
> wanted to max them out (as a quad) you should get a 2.5k CT output
> transformer that can handle that much power. Then current will be as
> high as 400ma across 1.25k (appx 500V) which is 200W (100W RMS).
>
> you'll need a somewhat beefy driver/splitter stage - the spec says max
> 51k on the G1 (fixed bias) and I'm guessing you'll bias it to at least
> -100V. So that's a pretty good signal (200V peak-peak) going in, driven
> into a (possible) 25k load impedence.
>
> I'd suggest something like 2 12AU7s to drive the control grids, a common
> cathode amplifier plus direct coupled cathode follower for each.
>
> 12AU7 has max cathode current of 22ma. With a swing of +/- 10ma driving
> a 25k load, that's 250V (more than enough signal). So thenit's just a
> matter of living within the limits of the 200V heater/cathode voltage
> limit (this is always a problem with direct-coupled tubes and phase
> splitters). Depending on the design, you could make this work with
> direct coupling the 12AU7b cathode to G1 on the KT120s. Then your fixed
> bias suppply will have to tolerate up to 40ma of current swing,
> regardless.
>
> And so on.
> --
> (aka 'Bombastic Bob' in case you wondered)
>
> 'Feeling with my fingers, and thinking with my brain' - me
>
> 'your story is so touching, but it sounds just like a lie'
> "Straighten up and fly right"
Thanks You for the answer. The 1650R 5k Ra-a is rated at 316 mA per side. Also I take in consideration to buy a kt88 quad to use it with this OT and to drive it from ecc99 plate for gain consideration. Do you think it work please? Thanks.

On 11/28/21 16:15, Dau Bine wrote:
> Pe miercuri, 24 noiembrie 2021, la 19:29:34 UTC+1, Big Bad Bombastic Bob a scris:
>> On 11/23/21 14:42, Dau Bine wrote:
>>> Pe marți, 23 noiembrie 2021, la 23:12:29 UTC+1, Big Bad Bombastic Bob a scris:
>>>> On 11/21/21 12:34, Dau Bine wrote:
>>>>> Hey. There is 650V max voltage limit recommendation for KT120 in triode mode. So how about a p-p KT120 triode strapped, supplied at 600V into Ra-a 10k load, please? Thanks.
>>>>>
>>>> are you looking for a design to build? single-ended triode config?
>>>>
>>>> I think you would be better with a push-pull triode config if you want
>>>> triode final stage. And I'd suggest sticking with the reference designs
>>>> when possible. You should be able to find some online... maybe for a
>>>> different output tube but then you make little tweeks here and there for
>>>> output impedence and bias and whatnot, and voila!
>>>>
>>>> also consider that when an output transformer voltage swings positive on
>>>> the plate, you can nearly double B+ voltge at the plate.
>>>>
>>>> Or were you actually looking at a resistive plate load? (not recommended).
>>>>
>>>> You can get inexpensive output transformers from guitar repair parts
>>>> places online - I think 'amplifiedparts.com" is one of them.
>>>>
>>>>
>>>> --
>>>> (aka 'Bombastic Bob' in case you wondered)
>>>>
>>>> 'Feeling with my fingers, and thinking with my brain' - me
>>>>
>>>> 'your story is so touching, but it sounds just like a lie'
>>>> "Straighten up and fly right"
>>> Hey. Thanks for the answer. I.m pretty much aware by You recommendation but this is what I have on my shelves. A kt120 matched quad, a hefty power transformer able to provide B+ 600v/1.5A and a Hammond 1650R 5k Ra-a. And I wonder if such of load is able to provide decent results for a push pull project with 4xKt120 in triode mode please. Thanks.
>>>
>> oh ok I think I ge4t it. I assume it's a standard 5k CT since you ar
>> doing triode mode. For 600V B+ at 2.5k it's about 200ma total for full
>> swing (100V on plate). I think a pair of KT120s in triode mode might be
>> able to do that. So now you just need to bias it properly. Make sure
>> the output transformer has sufficient power handling though, since a lot
>> of current could saturate the core and cause clipping and serious plate
>> overheating.
>>
>> The data sheet is here:
>> https://www.thetubestore.com/lib/thetubestore/TS-KT120.pdf
>>
>> According to that the triode config can go up to 230ma for a single
>> tube. Using a quad means less likely to fry them.
>>
>> The 5k transformer would probably get you ~100W (50WRMS). So if you
>> wanted to max them out (as a quad) you should get a 2.5k CT output
>> transformer that can handle that much power. Then current will be as
>> high as 400ma across 1.25k (appx 500V) which is 200W (100W RMS).
>>
>> you'll need a somewhat beefy driver/splitter stage - the spec says max
>> 51k on the G1 (fixed bias) and I'm guessing you'll bias it to at least
>> -100V. So that's a pretty good signal (200V peak-peak) going in, driven
>> into a (possible) 25k load impedence.
>>
>> I'd suggest something like 2 12AU7s to drive the control grids, a common
>> cathode amplifier plus direct coupled cathode follower for each.
>>
>> 12AU7 has max cathode current of 22ma. With a swing of +/- 10ma driving
>> a 25k load, that's 250V (more than enough signal). So thenit's just a
>> matter of living within the limits of the 200V heater/cathode voltage
>> limit (this is always a problem with direct-coupled tubes and phase
>> splitters). Depending on the design, you could make this work with
>> direct coupling the 12AU7b cathode to G1 on the KT120s. Then your fixed
>> bias suppply will have to tolerate up to 40ma of current swing,
>> regardless.
>>
>> And so on.
>> --
>> (aka 'Bombastic Bob' in case you wondered)
>>
>> 'Feeling with my fingers, and thinking with my brain' - me
>>
>> 'your story is so touching, but it sounds just like a lie'
>> "Straighten up and fly right"
> Thanks You for the answer. The 1650R 5k Ra-a is rated at 316 mA per side. Also I take in consideration to buy a kt88 quad to use it with this OT and to drive it from ecc99 plate for gain consideration. Do you think it work please? Thanks.
>

well, "work" most likely. You have to select the output transformer's
impedance based on the expected voltage/current swing of the output
tube. So you use the max/min current of the linear range on the
performance chart, figure out what G1 volts needs to be biased at, etc.
based on all of that. So in short at max current plate volts will be a
bit under 100V at the max current, and quiescent (AB mode) will be high
enough to not have crossover distortion of any kind [so is still in the
linear range of the G1:plate curve]. That's typically how the designers
would pick the transformer for a reference design, anyway.

I did not see any plate volt/current curves (with G1 voltage references)
in the docs I found, but if you look for them you should be able to find
them.

If you want to limit distortion you could try biasing the output tubes
as class A. You get higher total current through the transformer
though, so you will need to use one that is beefy enough. Class A push
pull should get you very low distortion open-ended, at the expense of
gain and power requirements.

[this is why I use NFB insead]

--
(aka 'Bombastic Bob' in case you wondered)

'Feeling with my fingers, and thinking with my brain' - me

'your story is so touching, but it sounds just like a lie'
"Straighten up and fly right"

I did not see any plate volt/current curves (with G1 voltage references)
in the docs I found, but if you look for them you should be able to find
them.

Here's a KT120 datasheet with Ia/Ua and Ia/Ug1 curves in pentode mode with
Ug2 reference . Also a Ia/Ua curve set in triode mode.
The published curves seem to originate from (an) individual tube(s) rather
than being nominal curves.
https://frank.pocnet.net/sheets/084/k/KT120.pdf

Gio

Pe vineri, 3 decembrie 2021, la 10:44:51 UTC+2, G.Re a scris:
> I did not see any plate volt/current curves (with G1 voltage references)
> in the docs I found, but if you look for them you should be able to find
> them.
> Here's a KT120 datasheet with Ia/Ua and Ia/Ug1 curves in pentode mode with
> Ug2 reference . Also a Ia/Ua curve set in triode mode.
> The published curves seem to originate from (an) individual tube(s) rather
> than being nominal curves.
> https://frank.pocnet.net/sheets/084/k/KT120.pdf
>
> Gio
Thank You Gents!
Well, have not to much options over there : a hammond 1650R Ra-a 5k with 300 mA current ability, and a hefty 1650W Ra-a 1.9k , over 800 mA. I think I may use the W with its 4 ohm output for 8 ohm load to get Ra-a 3.8K for a KT quad at 600V

On 12/5/21 08:22, Dau Bine wrote:
> Pe vineri, 3 decembrie 2021, la 10:44:51 UTC+2, G.Re a scris:
>> I did not see any plate volt/current curves (with G1 voltage references)
>> in the docs I found, but if you look for them you should be able to find
>> them.
>> Here's a KT120 datasheet with Ia/Ua and Ia/Ug1 curves in pentode mode with
>> Ug2 reference . Also a Ia/Ua curve set in triode mode.
>> The published curves seem to originate from (an) individual tube(s) rather
>> than being nominal curves.
>> https://frank.pocnet.net/sheets/084/k/KT120.pdf
>>
>> Gio
> Thank You Gents!
> Well, have not to much options over there : a hammond 1650R Ra-a 5k with 300 mA current ability, and a hefty 1650W Ra-a 1.9k , over 800 mA. I think I may use the W with its 4 ohm output for 8 ohm load to get Ra-a 3.8K for a KT quad at 600V
>

there's NO kill like OVERkill like NO kill I know... (that monstrous
transformer used that way)

--
(aka 'Bombastic Bob' in case you wondered)

'Feeling with my fingers, and thinking with my brain' - me

'your story is so touching, but it sounds just like a lie'
"Straighten up and fly right"

....I know, almost ridiculous for 88 W rms I got it...

Pe joi, 9 decembrie 2021, la 19:40:51 UTC+2, Big Bad Bombastic Bob a scris:
> On 12/5/21 08:22, Dau Bine wrote:
> > Pe vineri, 3 decembrie 2021, la 10:44:51 UTC+2, G.Re a scris:
> >> I did not see any plate volt/current curves (with G1 voltage references)
> >> in the docs I found, but if you look for them you should be able to find
> >> them.
> >> Here's a KT120 datasheet with Ia/Ua and Ia/Ug1 curves in pentode mode with
> >> Ug2 reference . Also a Ia/Ua curve set in triode mode.
> >> The published curves seem to originate from (an) individual tube(s) rather
> >> than being nominal curves.
> >> https://frank.pocnet.net/sheets/084/k/KT120.pdf
> >>
> >> Gio
> > Thank You Gents!
> > Well, have not to much options over there : a hammond 1650R Ra-a 5k with 300 mA current ability, and a hefty 1650W Ra-a 1.9k , over 800 mA. I think I may use the W with its 4 ohm output for 8 ohm load to get Ra-a 3.8K for a KT quad at 600V
> >
> there's NO kill like OVERkill like NO kill I know... (that monstrous
> transformer used that way)
> --
> (aka 'Bombastic Bob' in case you wondered)
>
> 'Feeling with my fingers, and thinking with my brain' - me
>
> 'your story is so touching, but it sounds just like a lie'
> "Straighten up and fly right"
Fortunately, smallest 1650R works as well making also a ridiculous situation using a kt quad for only 60w around, but it sound better than mismatched 1650w btw.

Pe sâmbătă, 11 decembrie 2021, la 06:19:41 UTC+2, Dau Bine a scris:
> Pe joi, 9 decembrie 2021, la 19:40:51 UTC+2, Big Bad Bombastic Bob a scris:
> > On 12/5/21 08:22, Dau Bine wrote:
> > > Pe vineri, 3 decembrie 2021, la 10:44:51 UTC+2, G.Re a scris:
> > >> I did not see any plate volt/current curves (with G1 voltage references)
> > >> in the docs I found, but if you look for them you should be able to find
> > >> them.
> > >> Here's a KT120 datasheet with Ia/Ua and Ia/Ug1 curves in pentode mode with
> > >> Ug2 reference . Also a Ia/Ua curve set in triode mode.
> > >> The published curves seem to originate from (an) individual tube(s) rather
> > >> than being nominal curves.
> > >> https://frank.pocnet.net/sheets/084/k/KT120.pdf
> > >>
> > >> Gio
> > > Thank You Gents!
> > > Well, have not to much options over there : a hammond 1650R Ra-a 5k with 300 mA current ability, and a hefty 1650W Ra-a 1.9k , over 800 mA. I think I may use the W with its 4 ohm output for 8 ohm load to get Ra-a 3.8K for a KT quad at 600V
> > >
> > there's NO kill like OVERkill like NO kill I know... (that monstrous
> > transformer used that way)
> > --
> > (aka 'Bombastic Bob' in case you wondered)
> >
> > 'Feeling with my fingers, and thinking with my brain' - me
> >
> > 'your story is so touching, but it sounds just like a lie'
> > "Straighten up and fly right"
> Fortunately, smallest 1650R works as well making also a ridiculous situation using a kt quad for only 60w around, but it sound better than mismatched 1650w btw.
And I have a winner for my project. 4xkt88 svetlana into hammond 1650R for Ra-a 2.5k ( 16 ohm tap was used with 8 ohm load) at 600v. Got exactly 100W rms with the tubes biased 60 percent. Tested down to 40cps at nominal power and no sign of partial saturation. Screen grids under 6w dissipation. Very happy with result. Thanks for helping!