Hello Everyone,
I hope someone can tell me what gridvoltage is, used for the EL34 tubes in my Simply two Unison research
I have a guy that I can buy tubes from and he asked me what's the gridvoltage
Can't find this info or a schematic anywhere on the internet so thought asking the experts
Thanks very much in advance🙂
Maikel
Holland
I hope someone can tell me what gridvoltage is, used for the EL34 tubes in my Simply two Unison research
I have a guy that I can buy tubes from and he asked me what's the gridvoltage
Can't find this info or a schematic anywhere on the internet so thought asking the experts
Thanks very much in advance🙂
Maikel
Holland
My first question is, Which Grid?
If you mean the Control Grid anything from -23 to -38Volts depending on the Anode voltage and the class you are using it in.
If you mean the Control Grid anything from -23 to -38Volts depending on the Anode voltage and the class you are using it in.
Could he be asking about the screen grid voltage, in order to determine whether some cheap Chinese EL34 will survive in the amp?
Does it?
If you amp is an AB amp and it uses those EL34 in pentode. you can ask the customer the G2 and G1 voltage and select a pair of EL34 for identical quiescent current.
As most pentode curves are ruler flat beyond 100 volts. the anode voltage is of little importance.
However it doesn't matter if the amp is adjustable bias.
You could contact UR and find out.
v4lve
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Thank you
Hi
Thank you all for replying and thank you very much for the schematic including all values YvesM
My suplier is asking because he can measure and match tubes and indeed was worrying a bit about some tubes from China and Russia
According to Unison research the amplifier is working in class A mode ultralinear mode and they say the tubes are woriking "almost in triode";
"consisting of one EL34 in a single-ended ultralinear configuration. This mode of operation for the output transformers allows the pentode EL34s to operate almost as if they were triodes. "
The amp autobiases itself, I don't have to do that myself
Hope I answered all questions
Interesting to see that there are quite some C's in the signal path; C1, C4, C6
Do you think that I can make the amp even better by using some better C's there or doesn't it change a bit?
Thanks again
Maikel
Hi
Thank you all for replying and thank you very much for the schematic including all values YvesM
My suplier is asking because he can measure and match tubes and indeed was worrying a bit about some tubes from China and Russia
According to Unison research the amplifier is working in class A mode ultralinear mode and they say the tubes are woriking "almost in triode";
"consisting of one EL34 in a single-ended ultralinear configuration. This mode of operation for the output transformers allows the pentode EL34s to operate almost as if they were triodes. "
The amp autobiases itself, I don't have to do that myself
Hope I answered all questions
Interesting to see that there are quite some C's in the signal path; C1, C4, C6
Do you think that I can make the amp even better by using some better C's there or doesn't it change a bit?
Thanks again
Maikel
From the schematic posted the operating conditions for the EL34 in this circuit are:
Ua = Ug2 = 327V
Ug1= - 23V
Ia = 70 mA
You can forward these informations to your tube supplier to help them select/match the tubes.
Please note that the plate dissipation at these operating conditions is 22.9W which is very close to the max. plate ratings for a EL34 (25W)
Most currently produced EL34's will not withstand this for very long and will fail sooner or later. (or will have a considerably reduced life) I would recommend using only good quality N.O.S EL34's in this amp for long lasting and reliable service.
Ua = Ug2 = 327V
Ug1= - 23V
Ia = 70 mA
You can forward these informations to your tube supplier to help them select/match the tubes.
Please note that the plate dissipation at these operating conditions is 22.9W which is very close to the max. plate ratings for a EL34 (25W)
Most currently produced EL34's will not withstand this for very long and will fail sooner or later. (or will have a considerably reduced life) I would recommend using only good quality N.O.S EL34's in this amp for long lasting and reliable service.
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Thanks a lot Tubologic!
I just emailed my suplier the schematic and mentioned the maximum plate-dissipation
Hope to get an appointment somewhere this week, I miss my music 🙂
Btw, I'm actually replacing the tubes with NOS ones, probably/hopefully Philips (Mullard). Also going to replace the ECC82 with nice NOSones
I post when I got them, maybe even with a picture
Greetings and thanks again everyone
Maikel
I just emailed my suplier the schematic and mentioned the maximum plate-dissipation
Hope to get an appointment somewhere this week, I miss my music 🙂
Btw, I'm actually replacing the tubes with NOS ones, probably/hopefully Philips (Mullard). Also going to replace the ECC82 with nice NOSones
I post when I got them, maybe even with a picture
Greetings and thanks again everyone
Maikel
HI all, resuming this old post.
I'm close to put in my simply two amp a pair of 5814a tubes, whose are said to be a direct swap for 12au7. but i see they tolerate a half of Vhk Max (max heater to cathode voltage, volts) !
100v vs 200v of the 12au7.
Is there anyone so kind to tell me, given the schema posted in the thread, if a 5814a will survive there? I'm not able to fully understand it.
Thank you so much.
I'm close to put in my simply two amp a pair of 5814a tubes, whose are said to be a direct swap for 12au7. but i see they tolerate a half of Vhk Max (max heater to cathode voltage, volts) !
100v vs 200v of the 12au7.
Is there anyone so kind to tell me, given the schema posted in the thread, if a 5814a will survive there? I'm not able to fully understand it.
Thank you so much.
No problem with 5814a, 100 volt vhk is plenty for this circuit. You may try 12bh7 instead for much better sound though. If your speaker is with 90+ db sensitivity you may mod the output for triode operation for better linearity and forget the feedback circuit.
Better still 2 stage complete.
Regards
Better still 2 stage complete.
Regards
Oh great info there! I've just ordered a pair of italian made RCA 12bh7 and can't wait to try those. Is there any info and reviews about that stage 2 mod / triode mod?
Not sure i'd go trough that, but it will be very interesting to read at.
Thank you so much for your answer, you canceled my doubt and gave great suggestions!