Hi All,
I am new to this forum,just registered today. I have jolida JD1501BRC hybrid amp and planing to roll off 12ax7 tubes,please guide me , I have tried tungsol 12ax7 RI,mullard 12ax7,jj 12ax7,siemens ecc83 NOS,GE 5751 NOS and telefunken ecc83 smooth place, among this I like GE 5751 NOS,but still I am looking for dynamics..... please guide me
Thanks
I am new to this forum,just registered today. I have jolida JD1501BRC hybrid amp and planing to roll off 12ax7 tubes,please guide me , I have tried tungsol 12ax7 RI,mullard 12ax7,jj 12ax7,siemens ecc83 NOS,GE 5751 NOS and telefunken ecc83 smooth place, among this I like GE 5751 NOS,but still I am looking for dynamics..... please guide me
Thanks
Hi,
I have a JD1701RC....I don't think the drivers tube going to change our amp...I've made same try as you
I have a JD1701RC....I don't think the drivers tube going to change our amp...I've made same try as you
The 5751 has a lower mu than the ECC83. I wouldn't expect huge dynamics from both. Or noteworthy changes in sound unless your amplifier is constructed on the edge and different current draws of different tubes change the behaviour of the circuit.
Did you measure bias of the different tubes you used?
Be aware that emission will rise in the first few hours you are heating a tube.
Did you measure bias of the different tubes you used?
Be aware that emission will rise in the first few hours you are heating a tube.
yes , GE 5751 don't have dynamics, I am expecting tube which can give dynamics. I don't have any idea abt bias.. My amp is hybrid amp ( 2 pair of 12ax7 + sold stage power amp ) .
I don't have idea, I just spoke with one person he said it will be more cost effective. Give me clear idea
I would like to retract the above post, did not realize it was a PCB hybrid amplifier, sorry about that...
Given the output stage is capable of delivering dynamics the input stage would have to be replaced. There are always many possibilities. If you want to stick with tubes go for a high transconductance low Rp type. These will need considerably higher anode current than a 12AX7, so a new powersupply will be needed as well. A Salas simplistic HV regulator could be used here. Use a CCS as plate load and LEDs on the cathodes to get rid of the cathode resistor and most importantly of the bypass cap. Hopefully you found a tube with enough mu to work with the output stage. DC couple to the output stage, don't use coupling caps.
Do your math.
Do your math.
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today I have tried siemens 12ax7 nos tubes, it is nice than ge but low is not like ge. It is very clear representation... it is nice but disappointed with lows
Leave them switched on for a couple of hours. Emission needs to stabilise when an old tube is used for the first time. Current draw usually goes up. Different current draws (operating points) will (if at all) change the sound more than the printing on the glass.
you mean to say we need to burn them for couple of days.. if I get the little bit more bass after burn this will be good for me. but GE have good sound stage than siemens..
Not a couple of days. Around 4h does it. If you hook up a meter and watch the bias you can see how it changes the first few hours.
I dont have any meter type and even dont know the bias 🙂 . I will burn them for some days....
have one small query , some people who know more abt this amps, they informed this jolida have some limitation,so by changing tube you will not get benefit
have one small query , some people who know more abt this amps, they informed this jolida have some limitation,so by changing tube you will not get benefit
I was one of these people. Tube rolling does soooo little for what you are looking for I personally consider it a waste of time. But maybe these little changes are all you need. It just seems very tedious.
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