I just picked up 2 weeks ago a PrimaLuna Dialogue Premium HP Integrated Amp. I took out the Stock EL34's and replaced with KT150's. Now I only have 15hrs of run time..Upscale Audio recommended to go right into the KT150. The sound is soo good...I cannot wait to hear this at 100hrs.
Yes, it was a suggestion more than a question. If you do, there may be current concerns in the overall design. I don't know enough to know. But, if you're going to use a turntable, you'll need a preamp somewhere. Easy to design into the circuit now that you have space for the tube. That is what I would do with it.
Well now.. it's been some time.
I've been using this amplifier consistently over the past few years, hooked to my record player, television, and PC (HTPC). Sounds great.. a few issues, but overall a great experience.
I think the time has come to put this back on the bench and make some performance enhancements. I'm also not sure that it's running properly, it's eaten 2x 6SN7 tubes and I'd actually like to measure it's power output.. I think it might be low.
My goal is better sound, and more power (isn't everyone's?). I'm not afraid of tearing it all down and rewiring it.. my first attempt was a bit sloppy and I think I can do a better job. Perfect time to make some enhancements.
Will update.
--CTD
I've been using this amplifier consistently over the past few years, hooked to my record player, television, and PC (HTPC). Sounds great.. a few issues, but overall a great experience.
I think the time has come to put this back on the bench and make some performance enhancements. I'm also not sure that it's running properly, it's eaten 2x 6SN7 tubes and I'd actually like to measure it's power output.. I think it might be low.
My goal is better sound, and more power (isn't everyone's?). I'm not afraid of tearing it all down and rewiring it.. my first attempt was a bit sloppy and I think I can do a better job. Perfect time to make some enhancements.
Will update.
--CTD
I'been building a parallel single ended guitar amplifier around Toroidy TTG-KT88PSE which is 1,5k 60W and has UL at 43%. First I use two KT120 tubes using Cathode bias but my coal to use Grid bias and when I get it tuned I might buy KT150's to it?
I have used this excellent calculatoe by Giuseppe Amato wjich should open using following link to play with different currents and voltages. For parallel SE just load resistance needs to be doubled and naturally target power as well. When you adjust headroom so high that 2nd and 3rd harmonics are about the same and then change quiscent current you can see how other end of the voltage gets clipped and distortion increases. That is what you need to do using an oscilloscope if you want to tune your amp to higher power without incteasing distortion.
Esa
Universal loadline calculator for vacuum tubes - Vacuum Tube Amplifiers - DIY
I have used this excellent calculatoe by Giuseppe Amato wjich should open using following link to play with different currents and voltages. For parallel SE just load resistance needs to be doubled and naturally target power as well. When you adjust headroom so high that 2nd and 3rd harmonics are about the same and then change quiscent current you can see how other end of the voltage gets clipped and distortion increases. That is what you need to do using an oscilloscope if you want to tune your amp to higher power without incteasing distortion.
Esa
Universal loadline calculator for vacuum tubes - Vacuum Tube Amplifiers - DIY
Thanks! I have tried to find why fixed bias is not common on single ended amplifiers and it seems like the listeners just like how cathode biasing sounds nicer? Is it because operation does not drift to B?
I understand that cathode biasing can protect the tube from severe "runaway" but isn't the tube getting bad already if its operating point begins to drift by itself?
Does cathode biasing keep both tubes better balanced than grid biasing which have individual trimmers to adjust bias? Perhaps fixed bias with smallish cathode resistors? I have seen one or two such SE schematics? Is for protection of to improve sound?
I see that fixed bias is simpler and cheaper if there is no need to install expensive and big bypass capacitors
On push pull tube amps fixed biasing is used more although most guitar amps do not seem to have individual tube bias adjusts, at least old schematics I have researched.
If I'm going to use cathode biasing I will install bias adjust trimmers with serial resistor parallel to cathode resistors to make bias set easier.
Esa
Cathode bias keeps the cathode current relatively constant until the tube is really very worn out. That's very convenient.
If you have individual cathode resistors for a paralleled single ended amplifier, then the two will balance nicely and you don't have to do any adjustments.
Fixed bias is absolutely not simpler, nor is it less expensive. What does a potentiometer cost vs. a (for your amp at least) 470uF/50V capacitor and a 5W resistor?
For push-pull amplifiers, fixed bias allows better performance when you leave class A.
If you're going to use cathode biasing, use the correct value of cathode resistor and call it a day. You do not need to add trimmers.
If you have individual cathode resistors for a paralleled single ended amplifier, then the two will balance nicely and you don't have to do any adjustments.
Fixed bias is absolutely not simpler, nor is it less expensive. What does a potentiometer cost vs. a (for your amp at least) 470uF/50V capacitor and a 5W resistor?
For push-pull amplifiers, fixed bias allows better performance when you leave class A.
If you're going to use cathode biasing, use the correct value of cathode resistor and call it a day. You do not need to add trimmers.
Thank You!
So far I have been experimenting with ~10W SE amp using 6L6GC, EL34 and KT88 and I have changed cathode resistor(s) so many times that I have began thinking other option. So I bought a 10VA 48VAC toroid for bias voltage and test fixed bias as well on this single low power amp as I don't want to toast two new KT120. Its PT has 100VAC bias output option.
Esa
So far I have been experimenting with ~10W SE amp using 6L6GC, EL34 and KT88 and I have changed cathode resistor(s) so many times that I have began thinking other option. So I bought a 10VA 48VAC toroid for bias voltage and test fixed bias as well on this single low power amp as I don't want to toast two new KT120. Its PT has 100VAC bias output option.
Esa
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