The ECC83 draws 0.3 amps so that's correct if you tested only one amp PCB? The El34's draw 1.5 amps each so your total heater current is around 6.6 amps for both PCB's.
Its a fair amount of current so you would expect them to be warm.
Have you got a temperature probe to check it? Ill do the same with mine and report back
Its a fair amount of current so you would expect them to be warm.
Have you got a temperature probe to check it? Ill do the same with mine and report back
https://www.mouser.it/datasheet/2/169/kbu1004-2451253.pdf
it can run up to 100°C without any derating.
it can run up to 100°C without any derating.
Would it be an idea to replace this rectifier with something like this:
https://no.farnell.com/multicomp/kbpc3506/diode-bridge-rect-1-ph-600v-module/dp/2675391
Mounted off board on the aluminium chassis for better heat dissipation?
https://no.farnell.com/multicomp/kbpc3506/diode-bridge-rect-1-ph-600v-module/dp/2675391
Mounted off board on the aluminium chassis for better heat dissipation?
I've got everything connected, with tubes and all. I think it will look quite stylish in black with the beautiful stainless steel output transformers.
No problems with adjusting bias and balance.
But I measured VC1-GND/VC2-GND on both channels to about 215 v. Which is a bit more that 150 - 200 v. Is this a problem?
No problems with adjusting bias and balance.
But I measured VC1-GND/VC2-GND on both channels to about 215 v. Which is a bit more that 150 - 200 v. Is this a problem?
Attachments
It depends on the voltage the output tubes are running at. Guessing 400V, it's 0,7 mA per side of the PI that is IMO a good working point.
You should have around 380V on output tubes, so you set the PI to around 0,9 mA per side. You could probably lower to around 0,7 per side.
This should give enough current for the a-g1 feedback, but stay away from the 12AX7's grid current zone (the higher the CCS current, the lower the voltage of the working point of the 12AX7, the lower its grid swing capability before entering grid current zone).
Thanks! Looking forward to listening to some music. I built an M2X amplifier last year, and it'll be fun to compare the two.
The supreme version is worth the cost I think. I'm planning on using it for many years to come, so I think it's important that it look decent.
What 12AX7 or 6N2P are you guys using with this amp?
I can't install 6N2P on my board being the very first one without jumpers, so I can only test 12AX7 on this boards (whilst on the EL84 one I have 6N2P).
Modern Tungsol seem a bit hard on top and lacks a bit in the middle.
Old Brimar have less gain so probably not the best choice for big bottles, but are way smoother than Tungsol.
I can't install 6N2P on my board being the very first one without jumpers, so I can only test 12AX7 on this boards (whilst on the EL84 one I have 6N2P).
Modern Tungsol seem a bit hard on top and lacks a bit in the middle.
Old Brimar have less gain so probably not the best choice for big bottles, but are way smoother than Tungsol.
Hi Zintolo
I'm running Telefunken's at the moment, tried Brimar but prefer the Tele's. Im also running the older PCB's on the current amps so not able to try the 6N2P's. I will order a couple from Toroidy when I order my transformers for the second build.
Cheers
I'm running Telefunken's at the moment, tried Brimar but prefer the Tele's. Im also running the older PCB's on the current amps so not able to try the 6N2P's. I will order a couple from Toroidy when I order my transformers for the second build.
Ill have a look at this today.
Cheers
Ok, I have to admit I just set the bias to the range mentioned way back and was running the EL34's at 55mA.
Have now re-checked the plate to cathode voltage and yes its a touch under 380v DC, on my tube calculator app it recommends 46.1 mA so I've dialed it back a bit and rechecked VC1-GND/VC2-GND and am sitting at 155v DC. Still low but within range and at the lower input voltage.
Would you recommend i swap the input to the 0 - 330vac and run at the higher B+ for EL34's? Any advise appreciated.
Have now re-checked the plate to cathode voltage and yes its a touch under 380v DC, on my tube calculator app it recommends 46.1 mA so I've dialed it back a bit and rechecked VC1-GND/VC2-GND and am sitting at 155v DC. Still low but within range and at the lower input voltage.
Would you recommend i swap the input to the 0 - 330vac and run at the higher B+ for EL34's? Any advise appreciated.
Personally I like the sound of EL34 at around 380V, so I'd keep it there.
Try it at higher voltages, a little bit more power could be what you like most.
Which app do you use? At 380V I'd stay at 55 mA like you did (measured at the cathode), because from datasheets the Ia/Ig2 ratio in this configuration is 5, so you are running 46 mA from the anode and 9 from the screen, approximately.
Try it at higher voltages, a little bit more power could be what you like most.
Which app do you use? At 380V I'd stay at 55 mA like you did (measured at the cathode), because from datasheets the Ia/Ig2 ratio in this configuration is 5, so you are running 46 mA from the anode and 9 from the screen, approximately.
Its just called "Tube Bias Calculator"
When my chassis bottom plates arrive back from the powder coater and I install the battery box for the bias LCD ill have a play with the higher B+. I had read a few members say they preferred the EL34 at the lower setting so its a good start.
Power is not what in after as I have fairly efficient speakers and dont lkesten at crazy levels these days.
At 46.1 Ma its listed as 70% of max
When my chassis bottom plates arrive back from the powder coater and I install the battery box for the bias LCD ill have a play with the higher B+. I had read a few members say they preferred the EL34 at the lower setting so its a good start.
Power is not what in after as I have fairly efficient speakers and dont lkesten at crazy levels these days.
At 46.1 Ma its listed as 70% of max
I'm wondering about this myself. I'm especially interested in experiences with 6N2P. How do they compare to ECC83 (of various types)? I have some Telefunken tubes, a few NOS ECC83 of unknown make and 6N2P to test with. I'll report back when I have the amplifier reassembled.