Hi all
i've build my first 6c33 tube amp by the help of this scheme
of course it has some problem cause that i had to change to the amount of 2 resistors in order to get the following voltage that wrote in the scheme
this is the modified scheme.i just changed these 2 resistor in order to get the mentioned scheme voltage
i've build my first 6c33 tube amp by the help of this scheme
of course it has some problem cause that i had to change to the amount of 2 resistors in order to get the following voltage that wrote in the scheme
this is the modified scheme.i just changed these 2 resistor in order to get the mentioned scheme voltage
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Its because the SRPP voltages are wrong in the diagram.
Typical cathode voltage is 1.7V for 12AX7 and the diagram has 0.8V which is half.
Typical cathode voltage is 1.7V for 12AX7 and the diagram has 0.8V which is half.
asking help for replacing srpp tubes
Hi all
i've build my first 6c33 tube amp by the help of this scheme
of course it had some problem cause that i had to change to the amount of 2 resistors in order to get the following voltage that wrote in the scheme
its the modified scheme.i just changed these 2 resistors in order to get the mentioned scheme voltage
a pair of jan GE 12ax7 used in pre amp section,actually i dont like these tubes and hard to find a good quality tubes in order to replace these 12ax7
i have sweet midrang but in high frequencies not good enough (of course amercian tubes are rich in midrange and vocal and European is more sharp and good in high frequencies)
so i wanna change these 12ax7 with pcc88 European tubes
i have siemens and valvo tubes and i wanna change those with 12ax7 in order to exprience the results and achieve to better high frequncies
12ax7 has a gain of about 100 and Gm 1250-1600,and pcc88 has gain of about 33 and Gm 1250
View attachment pcc88.pdf
so which resistor i should use for pcc88 srpp (cathode and between 2triode section) and the resistor before plate capacitor (22u 350v) in order to place pcc instead 12ax7 to get the best result? ????😕
Hi all
i've build my first 6c33 tube amp by the help of this scheme
of course it had some problem cause that i had to change to the amount of 2 resistors in order to get the following voltage that wrote in the scheme
its the modified scheme.i just changed these 2 resistors in order to get the mentioned scheme voltage
a pair of jan GE 12ax7 used in pre amp section,actually i dont like these tubes and hard to find a good quality tubes in order to replace these 12ax7
i have sweet midrang but in high frequencies not good enough (of course amercian tubes are rich in midrange and vocal and European is more sharp and good in high frequencies)
so i wanna change these 12ax7 with pcc88 European tubes
i have siemens and valvo tubes and i wanna change those with 12ax7 in order to exprience the results and achieve to better high frequncies
12ax7 has a gain of about 100 and Gm 1250-1600,and pcc88 has gain of about 33 and Gm 1250
View attachment pcc88.pdf
so which resistor i should use for pcc88 srpp (cathode and between 2triode section) and the resistor before plate capacitor (22u 350v) in order to place pcc instead 12ax7 to get the best result? ????😕
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Threads merged.
Please do not start multiple threads for the same topic. It is also unfair on those who replied to your first thread to simply delete material that was incorrect and start a new thread.
Threads merged.
Please do not start multiple threads for the same topic. It is also unfair on those who replied to your first thread to simply delete material that was incorrect and start a new thread.
unfortunately the first thread interrupts,so i had to delete it but i forget how to,thank u so much.
I would try 420 ohms at Ip of 2.8mA and a grid voltage of -1.15V. Since these draw more current than the 12AX7, you need to adjust the preamp power dropping resistor to get back to 175V as you did before.
Thanks
I have no limit for srpp plate voltage,i mean that 175v is not important as be 175,i can change it to 300v or higher
The main issue is to provide the enough gain for next stage and i'm worry about
So 420 ohms for cathode and between 2triode section ?
Can this provide the same 12ax7 voltage gain for next stage?
Thanks
But by changing the plate resistor to 360k ohm,i achieve the same 175v for plate voltage,and the cathode voltage is about 0.75v and it still works well
But as i wrote my main concern is about to change pcc88 instead 12ax7
I wanna put pcc instead 12ax7
And i wanna change the cathode and between 2triode section resistors(as both are equal) in order to provide the enough voltage gain for next stage
Which resistors i should use for srpp and plate??
You have to take care the SRPP upper cathode to heater voltage doesnt go over 100 volts.
The heaters dc level should be elevated to fix this.
Sth like your speeches wrote in datasheet
The big problem of these pcc tubes is the dc voltage between cathode and filamet
So what should i do?😕
Well i think that u triee to shoe me the differences voltage Dc between heater and cathode
This rating is about 180v for 12ax7
But about 100 for pcc88
You mean that this currently 175v for plate voltage whan i placed pcc88 is enough and shouldnt exceed more than???
Cause that for both identical triodes they have equal current but half of plate voltage
Each one use about 87.5v...
I don't know about feedback but this scheme that i chose has a correct base but the voltage and amount of resistors was wrong enough
I tried alot in order to achieve the same voltage that wrote in scheme
With 180k resistor the voltage was near the same that you mentioned in scheme
But other stages put into trouble and everythinges such as voltage changed alot...
I have not good high frequnecies
So i guess this related to my 12ax7
So i decided to change them with european pcc88...😕
Its somehow complicated and confusing
If u see my modified scheme,i just changed the amount of 2resistors in order to get the same voltage
So i made a mistake?
Thats wrong?
What should i do
Changing the 30k to 55k (or is it 56k) is ok, getting 220V or 280V makes no difference for the amp.
I see nothing in that circuit to suspect loss of high frequency.
If it is still the case, perhaps the output transformer.
Mona
I see nothing in that circuit to suspect loss of high frequency.
If it is still the case, perhaps the output transformer.
Mona
Thanks
So if i wanna change 12ax7 with pcc88,what should i do?
Which amount of resistor should be exert on pcc88 srpp to provide the enough gain for next stage?
I don't get it. There are a whole bunch of issues here.
You haven't read and understood the schematic. If you had, you would have identified the incorrect voltage at the top of the SRPP.
You want to change out a tube for another that has 1/3 the gain. You want to do this in the first gain stage. You want to do this because the original tube is hard to get (it's not) and you believe the geographic location of the manufacturer dictates the frequency response of the tube (it doesn't).
You haven't grasped the reason or method of elevating the heater voltage in the SRPP. You seem unable to do (or unaware of) the math to calculate gain.
This suggests to me that there is likely plenty more wrong and possibly dangerous in your build.
Are you sure you are not out of your depth here?
You haven't read and understood the schematic. If you had, you would have identified the incorrect voltage at the top of the SRPP.
You want to change out a tube for another that has 1/3 the gain. You want to do this in the first gain stage. You want to do this because the original tube is hard to get (it's not) and you believe the geographic location of the manufacturer dictates the frequency response of the tube (it doesn't).
You haven't grasped the reason or method of elevating the heater voltage in the SRPP. You seem unable to do (or unaware of) the math to calculate gain.
This suggests to me that there is likely plenty more wrong and possibly dangerous in your build.
Are you sure you are not out of your depth here?