Thanks, I do find it odd that varying the resistance isnt having any effect on cathode voltage though, which does make me think something is wrong. I can vary resistance from 0 - 317 ohms with the pot (as its paralelled with 470 ohms as in schemtic).
Anode voltages are approx 160, cathodes are 2.3 ish. this is with a B+ of 340.
Anode voltages are approx 160, cathodes are 2.3 ish. this is with a B+ of 340.
well its all cased up, I can balance the anodes of one tube, but not the other so i suspect its just a bad tube. Its about 16 volts off - not great.
Listening to it now, first thing that hits is the bass, its there is spades!
An externally hosted image should be here but it was not working when we last tested it.
Listening to it now, first thing that hits is the bass, its there is spades!
An externally hosted image should be here but it was not working when we last tested it.
Thanks,
I still dont think the sweat is over, i dont think the 12ax7 css's are functioning right, I'll rebuild them and check, there just is such minimal change in anode voltage with the pot.... which nobody else seems to have experience, and the cathode voltage is at 2.4v, which looking at the datasheets - with the anode at 165 and current supposedly at 0.5ma, i am not at a good point!!!
I still dont think the sweat is over, i dont think the 12ax7 css's are functioning right, I'll rebuild them and check, there just is such minimal change in anode voltage with the pot.... which nobody else seems to have experience, and the cathode voltage is at 2.4v, which looking at the datasheets - with the anode at 165 and current supposedly at 0.5ma, i am not at a good point!!!
Hi all,
Ian, Yves, firstly thanks for the innovative design. Over the week Ive been secretly wiring up ecl82 following more or less closely to the original schematic #1 and #9.
However, I have problem with the CCS for driver. In the last attempt, the LED lights up during power on, then it slowly fades, in 1 minute or so the light goes totally off. Then I turn off for few minutes, then power up, everything repeats itself again. Now I'm temporarily using simple jfet CCS, but would like to try the original (and much better) design.
Appreciate if anyone can help to diagnose. Thanks,
Colin
Ian, Yves, firstly thanks for the innovative design. Over the week Ive been secretly wiring up ecl82 following more or less closely to the original schematic #1 and #9.
However, I have problem with the CCS for driver. In the last attempt, the LED lights up during power on, then it slowly fades, in 1 minute or so the light goes totally off. Then I turn off for few minutes, then power up, everything repeats itself again. Now I'm temporarily using simple jfet CCS, but would like to try the original (and much better) design.
Appreciate if anyone can help to diagnose. Thanks,
Colin
Hi skyraider,
Just a preliminary question:
Are your sure you want to use the ECL82 ?
YvesM's schematic is based on the ECL86 (1/2 ECC83 + derated EL84 in a bulb).
The ECL82 is quite a different beast. The triode section is completely
different. The pentode section could do. I doubt that the ECL82 works in this design here as it really needs the exact specs of an ECL86 due
to the local feedback loops.
For your problem: I guess that as the tubes heat up and draw current,
your ccs starts to act weird as it is not adapted the the ECL82.
Bye
Yves
Just a preliminary question:
Are your sure you want to use the ECL82 ?
YvesM's schematic is based on the ECL86 (1/2 ECC83 + derated EL84 in a bulb).
The ECL82 is quite a different beast. The triode section is completely
different. The pentode section could do. I doubt that the ECL82 works in this design here as it really needs the exact specs of an ECL86 due
to the local feedback loops.
For your problem: I guess that as the tubes heat up and draw current,
your ccs starts to act weird as it is not adapted the the ECL82.
Bye
Yves
Update on this ....
Its had about 30hrs to settle in, but people do say blackgates need 100hrs+.
1sts few hours its sounded brilliant, deep bass, extended fluid treble and mids to die for.
10-25hrs..... not so good. muddied bass e.g. Ray lamontagne, till the sun turns black has a double bass throughout, some how the amp lost its definition and the pluck was gone, it was just too muddy).
30hrs+ now were talking! the bass is detailed and drops lower than my solid state. the treble is airy, creates a lovely sense of space. I still think the LF will tighten up some more.
Seems like the blackgate rumours are true, i'll be honest i didnt believe them until this experience.
Its had about 30hrs to settle in, but people do say blackgates need 100hrs+.
1sts few hours its sounded brilliant, deep bass, extended fluid treble and mids to die for.
10-25hrs..... not so good. muddied bass e.g. Ray lamontagne, till the sun turns black has a double bass throughout, some how the amp lost its definition and the pluck was gone, it was just too muddy).
30hrs+ now were talking! the bass is detailed and drops lower than my solid state. the treble is airy, creates a lovely sense of space. I still think the LF will tighten up some more.
Seems like the blackgate rumours are true, i'll be honest i didnt believe them until this experience.
I know.... perhaps i could have rained the budget in on the caps. But i am very happy with the results. I only paid £10 for 4 X 470uf blackgates, and £4 for 4 x 1000uf silmics. I am going to have a play with removing the silmics, but i fear i may loose too much bass.
last question, should i increase the resistors between the UL taps and the screens. Currently they are as per the schematic, but i am running 340v b+.
Cheers
Adam.
last question, should i increase the resistors between the UL taps and the screens. Currently they are as per the schematic, but i am running 340v b+.
Cheers
Adam.
Hi Guys,
Back "on deck" after 3 weeks away on holidays.
On my latest Baby Huey monoblocks I have 350V rails and am using 150 Ohm resistors from the Ultralinear Taps to the EL84 screens.
I have resurrected the original Baby Huey with the CCS biased Output Tubes so that I can do A/B comparisons. On that amplifier I found that the 470uF Blackgate CCS Bypass Capacitors by themselves did impact bass a little and am now using 1000uF Blackgates.
Adamus - I would leave the Silmics in. Your experience with the Blackgate Capacitors is very typical - they sound quite good when first fitted, then they go "Squirrely" for a bit before eventually settling in. This typically takes about 40 hours.
Yvesm - would you care to elaborate on why you don't like Ultralinear. I've seen a number of respected designers (like yourself) say similar things yet I have never been unhappy with it myself - particularly with EL84.
Cheers,
Ian
Back "on deck" after 3 weeks away on holidays.
On my latest Baby Huey monoblocks I have 350V rails and am using 150 Ohm resistors from the Ultralinear Taps to the EL84 screens.
I have resurrected the original Baby Huey with the CCS biased Output Tubes so that I can do A/B comparisons. On that amplifier I found that the 470uF Blackgate CCS Bypass Capacitors by themselves did impact bass a little and am now using 1000uF Blackgates.
Adamus - I would leave the Silmics in. Your experience with the Blackgate Capacitors is very typical - they sound quite good when first fitted, then they go "Squirrely" for a bit before eventually settling in. This typically takes about 40 hours.
Yvesm - would you care to elaborate on why you don't like Ultralinear. I've seen a number of respected designers (like yourself) say similar things yet I have never been unhappy with it myself - particularly with EL84.
Cheers,
Ian
gingertube said:
Mmmmh !
What I beleive in:
-UL reintroduces some Miller effect.
-UL asks for a better OPT.
-UL asks for better PSU regulation/smoothing, in other words, pentodes/tetrodes are less sensitive to plate voltage sag than to screen voltage one and it 'is easier to fix screen voltage than plate + screen one.
Probably, the importance of these points increases with the size of the tubes ? ?
Yves.
I have a pair of OPT used in a guitar KT88 amp. They are heavy (approx. 3kg each) and I guess used in 70-100W amp.
I wonder if they would be useable for hifi, when only needed to deliver 10-15W?
The are norminel 3500:8 Ohm with 40% UL tappings. But by using 4 Ohm secondary I can get 7000:8...will that be useable for Baby Huey or other EL84 amps?
I wonder if they would be useable for hifi, when only needed to deliver 10-15W?
The are norminel 3500:8 Ohm with 40% UL tappings. But by using 4 Ohm secondary I can get 7000:8...will that be useable for Baby Huey or other EL84 amps?