1 volt AC. There is no clipping. That was NOT maximum output. Maximum output is some 35 volts at clipping.
I told you the gain. You can do the math.
Attachments
Then this input circuit should drive it to full output. The resistors may need some fine adjustment in your LT Spice simulator. I did not do that. I threw that together in like 5 minutes or so.
Well that really sounds like something I can work with. I'll probably be feeding it 2v, and if it can put out 30V, we should be good.
I really do appreciate your help. I'll order up some resistors soon but in the meantime perhaps I can hack this together with other stuff to see how it sounds.
Thanks again 🙂
I've implemented this schematic but I'm still unable to drive the 6CU6 to clipping when I drive this gain stage with an average computer at 100% volume.
I've also been working on a nice little 35EH5 spud amp, but hopefully we can get this figured out too 🙂
I do not know the output capability of your computer. Did you try a CD player?
You may need another gain stage.
Replacing the upper tube with a trio of 4.5mA Current Limiting Diodes and increasing the cathode resistor to 220 ohms gives about 30dB of gain. Clipping is at about 21Vrms output (30Vp-p) which is about 1% THD, according to simulation.
You could also cascade the two triode sections for even more gain.
You could also cascade the two triode sections for even more gain.
I've been looking at tubes on eBay and I found that 5755 Tubes are cheap and have a good amount of gain. Do you think this tube would serve me better?
The 5755 is an interesting tube, some basic info derived from drawing all over printout of plate curves: at bias of -1V, plate 180V, it has a Gm of just over 1mA/V and plate resistance of ~60k, mu a little over 60. Beware it has a unique pinout, and is suceptible to hum- I tried it in a phono preamp and it had to be used with DC heating and a sheild. IMHO would not be using it as an input tube for a power amp, I have found that common little pentodes like 6AU6, 6AG5, 6BC5 etc have a nice amount gain and linearity as triodes loaded with a CCS, and bias up happily at 3.5-4 volts/8mA (easily obtained with LED bias), allowing plenty of input headroom.
Hi,
Then why not pick a valve that was designed for low anode voltages?
Just about any valve ( I assume you want to stay with triodes) that was made for car radio use should. Just keep in mind these often consume an awful lot of heater power.
Actually the 6DJ8 works rather well here as does the ECC86 (which also happens to be a frame grid type much like the 6DJ8)
The 5755 is really a special valve designed as a DC amplifier in high precision regulated supplies. You don't need a mu of 70 for a line stage and with such low B+ you'll not reach that figure unless you'd use a CCS and then some.
No, all in all the ECC86/6GM8 seems to be the best candidate for the job if I understand your project correctly.
Ciao, 😉
Then why not pick a valve that was designed for low anode voltages?
Just about any valve ( I assume you want to stay with triodes) that was made for car radio use should. Just keep in mind these often consume an awful lot of heater power.
Actually the 6DJ8 works rather well here as does the ECC86 (which also happens to be a frame grid type much like the 6DJ8)
The 5755 is really a special valve designed as a DC amplifier in high precision regulated supplies. You don't need a mu of 70 for a line stage and with such low B+ you'll not reach that figure unless you'd use a CCS and then some.
No, all in all the ECC86/6GM8 seems to be the best candidate for the job if I understand your project correctly.
Ciao, 😉
Hello, theres a bit of a misunderstanding here. My line stage preamp is staying as-is, I only mentioned it because of a ground loop issue with it and the amp that this thread is actually about (the 6CU6 monoblock).
I am trying to look for a tube that will drive my 6CU6 better than the single 12AU7 gain stage that is currently in the monoblock.
Hi,
Ah...I see now. The 12AU7 stage already exists and that's the one running from the low B+.
Oh well, at the very least you now have some alternatives for the 12AU7As...
😀
Sorry for the confusion, 😉
Ah...I see now. The 12AU7 stage already exists and that's the one running from the low B+.
Oh well, at the very least you now have some alternatives for the 12AU7As...
😀
Sorry for the confusion, 😉
A question to all those smarter than I,
Why in the world is this contraption humming????? I get a very loud and angry hum out of the speakers whenever the power is turned on. As soon as I shut the amp off, even as I can still hear music, the hum is gone. I've done star grounding, I've tried DC on the heaters, shorted the input, removing the driver tube, but NOTHING does it.
My filter caps should be excellent, even overrated. I only get .5VAC across the main filter cap, and something like .2VAC across my negative grid bias cap.
Hopefully someone can shed some light on this.
Why in the world is this contraption humming????? I get a very loud and angry hum out of the speakers whenever the power is turned on. As soon as I shut the amp off, even as I can still hear music, the hum is gone. I've done star grounding, I've tried DC on the heaters, shorted the input, removing the driver tube, but NOTHING does it.
My filter caps should be excellent, even overrated. I only get .5VAC across the main filter cap, and something like .2VAC across my negative grid bias cap.
Hopefully someone can shed some light on this.
Yes, the photo showing the component placement.
And power supply schematic is needed too.
You told the hum exist even when ECC88 is removed.
How is the hum when you take 6CU6 away ?
(sometimes the hum is coupled directly between power- and output transformer)
In general, GNFB would give essential improvement to this problem too.
And power supply schematic is needed too.
You told the hum exist even when ECC88 is removed.
How is the hum when you take 6CU6 away ?
(sometimes the hum is coupled directly between power- and output transformer)
In general, GNFB would give essential improvement to this problem too.
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