I modify my Northern Electric LR mono amplifier.
What I get now:
4 * EL34 in PP and parrallel config.
75 watts of power in 4 ohms at 450 v
I could go more power (90w) with Diode, but go back with 2 * 5U4 at 75w/450v.
To get that I use an 1650R Hammond OT
To develop this amp, I use the OT from another amplifier. So need to return it back.
It play verry good in my housewrecker box as a sub for my A7 with 2 * 15" in Isobaric config at 4 ohms.
So I need to buy an new OT.
Should I go with an 1650t. As it is 1900ohms agains t 5000ohms for my 1650r....
I'm not so sure...?
Even if will get lot more ma.
Lots more possibility to modify with an 1650T
(But power transfo is limited in current... May be not as crucial as it appear.)
Any infos I need to know from your experiment before my final choice?
Mario
What I get now:
4 * EL34 in PP and parrallel config.
75 watts of power in 4 ohms at 450 v
I could go more power (90w) with Diode, but go back with 2 * 5U4 at 75w/450v.
To get that I use an 1650R Hammond OT
To develop this amp, I use the OT from another amplifier. So need to return it back.
It play verry good in my housewrecker box as a sub for my A7 with 2 * 15" in Isobaric config at 4 ohms.
So I need to buy an new OT.
Should I go with an 1650t. As it is 1900ohms agains t 5000ohms for my 1650r....
I'm not so sure...?
Even if will get lot more ma.
Lots more possibility to modify with an 1650T
(But power transfo is limited in current... May be not as crucial as it appear.)
Any infos I need to know from your experiment before my final choice?
Mario
Thanks.
Received lot s of views, your the first to give an answer.
I am bit eager, so I bought the 1650T Friday.
As my set up is allready with the 1650R, I know the R is really ok for 4 valves
But I think, as my set up now with 4 valves EL34 is so easy going, that my power transfo could accept 2 more valves without sign of underpower
Will have more then 100 Watts with 6 EL34, around 110-120Watts. So R will be too limits, so decided to go with the 1650T who is ok trough 120.
If power transfo doesn t have anough power, for 6 El34, l will reconfigure it.
I will need to tune back to 4 KT88, if too much, will tune back to 4 or 6 KT66.
I m about sure will work easy with 6 EL34.
But will it be better with 4 KT88, that s the question.
Me for the sub base I prefer the tone of the 88. I like the sustain power of the Kt88, opposed to the fastness of the El34. But at this level of sub, I m not sure if we can find the difference
I will receive it pretty soon.
Then I will know, it is something I really want to experiment.
More possibility with the T motivate my choice.
Thanks again
Mario
Received lot s of views, your the first to give an answer.
I am bit eager, so I bought the 1650T Friday.
As my set up is allready with the 1650R, I know the R is really ok for 4 valves
But I think, as my set up now with 4 valves EL34 is so easy going, that my power transfo could accept 2 more valves without sign of underpower
Will have more then 100 Watts with 6 EL34, around 110-120Watts. So R will be too limits, so decided to go with the 1650T who is ok trough 120.
If power transfo doesn t have anough power, for 6 El34, l will reconfigure it.
I will need to tune back to 4 KT88, if too much, will tune back to 4 or 6 KT66.
I m about sure will work easy with 6 EL34.
But will it be better with 4 KT88, that s the question.
Me for the sub base I prefer the tone of the 88. I like the sustain power of the Kt88, opposed to the fastness of the El34. But at this level of sub, I m not sure if we can find the difference
I will receive it pretty soon.
Then I will know, it is something I really want to experiment.
More possibility with the T motivate my choice.
Thanks again
Mario
With 6 EL34's and 450v HT your easily get 120w with a 1650TA, your mains tfmr will need to supply that 450v at roughly 700mA, but that's with a sinewave. Whilst playing music the most your mains tfmr will need to supply about 350mA. This is fixed bias UL
EL34's will need to be biased at about 35mA or - 44v. I used SS rectification with a 1100u capacitor bank.
Andy.
EL34's will need to be biased at about 35mA or - 44v. I used SS rectification with a 1100u capacitor bank.
Andy.
Robert,
When I mean perfect,
I mean perfectly listenable at the sub frequency, as from 20(-2db) to 63hz, where there crossed to my A7.
But if you look at the distortion level. You could easily see that it is no so perfect.
But you can't ear that distortion with music, it's too low.
May be the wall but not your ear.
For this purpose, I just want to ear good music, and a kind of following the note, not just the same boom everytime we got one.
The test is pretty easy, you just put the sub, no A7, if you can find the beat of the song, it is perfect, if you can t, it is garbage.
The rest is purely measure, but for me, it s to play music. So do my test with music, then confirm with measure, and correct my work if not satisfy with what I heard. If like it, leave it like this,...? till my next crisis. ... Lol
Mario
When I mean perfect,
I mean perfectly listenable at the sub frequency, as from 20(-2db) to 63hz, where there crossed to my A7.
But if you look at the distortion level. You could easily see that it is no so perfect.
But you can't ear that distortion with music, it's too low.
May be the wall but not your ear.
For this purpose, I just want to ear good music, and a kind of following the note, not just the same boom everytime we got one.
The test is pretty easy, you just put the sub, no A7, if you can find the beat of the song, it is perfect, if you can t, it is garbage.
The rest is purely measure, but for me, it s to play music. So do my test with music, then confirm with measure, and correct my work if not satisfy with what I heard. If like it, leave it like this,...? till my next crisis. ... Lol
Mario
Andy, thank you for you reply.
Will use this kind of rectification to start my work. As I developped a self adjust bias, it will be easily adjustable with the sinewave. I know my limit is with the current. But have no specs for power transfo, except it can easily push 13 tubes and the fact that it is about 18-20 pounds or more. The amplifier originally pushed 11 speakers at 2 ohms.
So work with what I got, and see the limit I would reach when will receive my new transfo.
The bank of tube is easy with 4 *EL34 (socket pretty close one to the other) But as soon as I want to use Kt88 or more El34, I need to use the second bank of tube socket, it 's a work that I didn t done yet. So will be done when will receive my 1650T, and will be able to do my test when the transfo will be permanently fixe. Then the real work will start to establish the nicest 110-120 watts I can reach with EL34 or Kt88 or Kt66. As I have lots more voltage that I could get back with diode, I think EL34 (lower needed Ma) will be the one... But if ok, will use the KT88, as I think I could get more sustainable power for lower Hz.... But need lot 's more current for Kt88..???? (Harder to find then voltage for el34).
Anyway, will see, as I m on my way to work on it.
Thank for your answer.
Mario
Thanks for your reaction. My question was adressed to claudiomas since he wrote that 5K for 4 x EL34 is perfect. I just wanted to know why he wrote that. 5K for 4 x EL34 in pentode or ul mode looks unusual high to me. I'm just eager to learn more.
My follow up:
Defenitively need to change power transfo.
Good voltage
Not anough Ma.
So this original power transfo, is really limit to do something more then is own original design. The filament current can t support the current nead to bigger valve and the Ma, defenitively not anough to support.
So at my standing point, my next step, optimise this amp for 2 Kt 88.
If don t like what I ear, will go for 4 x 6L6 for 100~135watts the limit of my new 1650T.
So wait my new power transfo.
Defenitively need to change power transfo.
Good voltage
Not anough Ma.
So this original power transfo, is really limit to do something more then is own original design. The filament current can t support the current nead to bigger valve and the Ma, defenitively not anough to support.
So at my standing point, my next step, optimise this amp for 2 Kt 88.
If don t like what I ear, will go for 4 x 6L6 for 100~135watts the limit of my new 1650T.
So wait my new power transfo.