Stajo, I forgot one, the one in the middle.. 😀 Remove two of the four tabs on the rightmost version and you have the four I am familar with in ST glass.
Hi Kevin,
What filament current are you running the 26 with? You can definitely reduce microphonic noise by starving the filament current. I found 850-900mA range to be very good in terms of sound and impact on emission. With rubber suspension and the filament starvation I tried every single combination of ST and globe I had around and found this to be really quiet. Never had a problem again with microphonic noise. This is something I used with more attention in the 4P1L as it's quite tricky as everyone knows.
With regards to electrostatic hum, I simply discarded the used 26 that presented this condition 🙂, so no screening in my case
Ale
What filament current are you running the 26 with? You can definitely reduce microphonic noise by starving the filament current. I found 850-900mA range to be very good in terms of sound and impact on emission. With rubber suspension and the filament starvation I tried every single combination of ST and globe I had around and found this to be really quiet. Never had a problem again with microphonic noise. This is something I used with more attention in the 4P1L as it's quite tricky as everyone knows.
With regards to electrostatic hum, I simply discarded the used 26 that presented this condition 🙂, so no screening in my case
Ale
#26 preamp
Hi,
Am a newbie here. Wish to seek the advice from this forum re Lundahl LL1660s / 10mA.
Is this the same as the plain 1660? In the 1660s, i noticed there are 6 pins on one side and another 8 pins on the other side. I assumed the side with 8 pins is the same as those on the 1660 and is wired the same way. Am confused with the other with the 6 pins. I wish to wire it into the recommended 4.5:1 for this preamp. How do i wire the 6 pins and what are the 2 extra pins for?
Right now am using a 200H/15mA plate choke with a 1uf coupling cap at the output. I must confess i'm very much satisfied with the 26's performance. Am just curious how it will sound with the 1660s, in place of the choke/coupling cap combo! But first i want to be sure of the 1660s's suitability and the correct wiring re the side with the 6 pins.
Am using either a Jelab Simple 45/2a3 amp or a welborne 300b amp into a Big Fun horns with a lowther ex3 drivers.
Thanks in advance to your advice!
BugC
Hi,
Am a newbie here. Wish to seek the advice from this forum re Lundahl LL1660s / 10mA.
Is this the same as the plain 1660? In the 1660s, i noticed there are 6 pins on one side and another 8 pins on the other side. I assumed the side with 8 pins is the same as those on the 1660 and is wired the same way. Am confused with the other with the 6 pins. I wish to wire it into the recommended 4.5:1 for this preamp. How do i wire the 6 pins and what are the 2 extra pins for?
Right now am using a 200H/15mA plate choke with a 1uf coupling cap at the output. I must confess i'm very much satisfied with the 26's performance. Am just curious how it will sound with the 1660s, in place of the choke/coupling cap combo! But first i want to be sure of the 1660s's suitability and the correct wiring re the side with the 6 pins.
Am using either a Jelab Simple 45/2a3 amp or a welborne 300b amp into a Big Fun horns with a lowther ex3 drivers.
Thanks in advance to your advice!
BugC
Hi!
The 1660s has shields between primary and secondary which improves performance for phase splitting applications. You can use it just like the regular 1660. Wire the extra pins to ground.
Best regards
Thomas
The 1660s has shields between primary and secondary which improves performance for phase splitting applications. You can use it just like the regular 1660. Wire the extra pins to ground.
Best regards
Thomas
I'm sorry my ignorance how do you calculate heater filament current with Ohms law:
I=V/R
I=1.5V/1.5Ohms = 1A
Is OK?
I=V/R
I=1.5V/1.5Ohms = 1A
Is OK?
Hi Felipe, RCA datasheet 26.pdf shows specification heater voltage 1.5V and heater current 1.05A. So heater resistance is 1.5/1.05 = ~1.428 ohm at 1.5V. But heater resistance is not linear, it varies with voltage so can not calculate current at other voltage or calculate voltage at other current, have to measure to be correct.
In reality same tube specification (like 26, 6V6, 12ax7 etc) differ quite a lot in the amount of current needed for a specific voltage between different brands. If trying to control voltage with CCS this gets notable fairly quick.
Hi Felipe, I really don't know how to answer this question. If you have no idea how to measure current, voltage or resistance, I strongly suggest you read and understand basic electronics similar to online tube learning newbies #16 before making expensive mistakes or even put your own safety in jeopardy.
Thanks guys, I ask because I don't want to damage the tube. Can I measure the current across the 10R filament resistor?
Last edited:
hi Felipe,
Yes, please measure current across the 10Ω resistor.
Another way:
Since you have a Coleman Regulator, you can measure voltage across R1 and read Amperes directly.
So with R1 having 1.0V = 1.0A in filament.
It's best not to use Meter in current mode, as they can drop voltage, and spoil the sound while connected.
Yes, please measure current across the 10Ω resistor.
Another way:
Since you have a Coleman Regulator, you can measure voltage across R1 and read Amperes directly.
So with R1 having 1.0V = 1.0A in filament.
It's best not to use Meter in current mode, as they can drop voltage, and spoil the sound while connected.
Hi Rod,
Thanks, now I can do starved filaments.
You are very kind with me, now the #26 is sounding as good as never ear before at home or in other systems, playing originals hi-rez DSD128 files from Opus3.
Thanks to you now I can say #26 is a very very good pre.
Have a nice weekend
Felipe
Thanks, now I can do starved filaments.
You are very kind with me, now the #26 is sounding as good as never ear before at home or in other systems, playing originals hi-rez DSD128 files from Opus3.
Thanks to you now I can say #26 is a very very good pre.
Have a nice weekend
Felipe
Hi Felipe, glad to hear you get it, but please try to really understand electronics and the danger involved. I saw you work for several years with vacuum tubes at lethal voltage level without proper understanding on electronics, it is possible that you also have incorrect ideas on safety.
Remember to also check the DC anode currents do not exceed the maximum allowed value of your output transformers.
Thanks for your advice indra1 really appreciate, also my English level is very low but thanks to people like Rod, Salas & others always I end the projects safety & with success, due to my difficulty (language & electronics) for me all the projects take a lot or more time.
I ask apologizes to all people that was involved tried to help me if not always I followed his advices (Vinylsavor, andyjevans, etc).
I ask apologizes to all people that was involved tried to help me if not always I followed his advices (Vinylsavor, andyjevans, etc).
Thanks to remember me, I will check the DC anode current measuring the voltage across the output transformers.