Hello Magz. The 01A is indeed magical but I gave up on it because I didn't want to use an active load or a cathode/source follower. I can't remember your circuit but I guess it's that. I only use 2 stage amps, and the 01A is not a driver on its own.
I'll have to try the globe 26s again. I rather like the brighter sound of the STs.
I'll have to try the globe 26s again. I rather like the brighter sound of the STs.
Hi Kevin,
Well, not quite a year on from your statement, I am slow as usual, and just coming around to this...I am curious about which MM model(s) you have used, and with which EML valves for line preamp stage output. HA-133 are only good for 8mA, so good/possible for 26, but you suggest an MM rated for 30mA (which I cannot find on their list), so I'm not sure about the comparison...more info would be appreciated, please.
Best, Robert
Hi Robert,
They were custom built for me and are not in the standard catalog. I would contact them directly, mention me and ask about my 20K line stage transformer. I use a lot of their transformers in my personal gear and they very good performers.
I've been using EML 20B in my line stage, and EML 300B in my mid-range/tweeter amps.
They were custom built for me and are not in the standard catalog. I would contact them directly, mention me and ask about my 20K line stage transformer. I use a lot of their transformers in my personal gear and they very good performers.
I've been using EML 20B in my line stage, and EML 300B in my mid-range/tweeter amps.
It's very strange, I never suffered the 26 microphonics, could be I'm very fortunate and used a lot of different tubes, ST & globe with different brands....
N.B. Always used Rod Coleman filaments regs. & PSU in a separate chassis. But used with & without regulated B+ no change!!
N.B. Always used Rod Coleman filaments regs. & PSU in a separate chassis. But used with & without regulated B+ no change!!
Well try them with 20dB of gain after them (power amp) and speakers with efficiency >100dBspl. I have yet to encounter any DHT that is not microphonic to some extent. If you are using them in an amplifier driver stage the sensitivity to vibrations will be reduced compared usage in a line stage which is what I am talking about here.
I have used 01/12/26 from a variety of brands as well all exhibit this to a significant degree. DHT output tubes in my amplifiers are also microphonic. I also use Coleman regulators and have been since 2010. (Mids and tweeters are >110dBspl/w/m with no attenuators between the amps and drivers.)
I have used 01/12/26 from a variety of brands as well all exhibit this to a significant degree. DHT output tubes in my amplifiers are also microphonic. I also use Coleman regulators and have been since 2010. (Mids and tweeters are >110dBspl/w/m with no attenuators between the amps and drivers.)
No, they were very hard to obtain in the U.S at a price I could consider when I was still experimenting with DHTs.
Today the system is DSP based and mostly solid state. There are 4 channels of class D amplification for subs and woofers, while the mid and HF horns are handled by 4 channels of 300B/D3A based SE amps. Some tube analog remains for LP playback, but gets very little use.
Today the system is DSP based and mostly solid state. There are 4 channels of class D amplification for subs and woofers, while the mid and HF horns are handled by 4 channels of 300B/D3A based SE amps. Some tube analog remains for LP playback, but gets very little use.
My revised circuit for my 26 stage, which drives my EL12n outputs making a 2 stage amp - my daily amp.
I bumped up the B+ to 364V, which allowed me to use a 39K anode resistor. Audible improvement - cleaner and generally better with tighter bass than the 27K I had in before. This is now really good to my ears. I used to think the 26 was warm, but this is just super clean and transparent. The ST version.
I bumped up the B+ to 364V, which allowed me to use a 39K anode resistor. Audible improvement - cleaner and generally better with tighter bass than the 27K I had in before. This is now really good to my ears. I used to think the 26 was warm, but this is just super clean and transparent. The ST version.
I'm sorry never used with 20dB of gain after them (power amp) with >100dB loudspeakers. BTW depending the schematic used 26 doesn't have a lot of gain. Using high efficiency loudspekaers open the use of low gain power amp...always looking for the best system gain structure: not too low nor too high
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Simulation: x6.7 and 6k6.
x8 is the theoretical gain, if the tube's load is infinitive.
x8 is the theoretical gain, if the tube's load is infinitive.
Hoi @kevinkr
I am participating at Diyaudio since some twenty years, and I think you are one of the few that I know since then. From my perception you never stopped building all sort of tube amplifiers, and now you are at class D. Wow, I think it takes some courage to stop a certain path one has been travelling so long? I sometimes think that class D would probably be ok for me as well, but then I think that all the time and money I invested in tubes will be sort of wasted...
And for a practical question: what class D amplifiers are you using? 🙂 I am also thinking about testing class D on my power hungry woofers.
I'm curious about mixing tubes with SS.
How does one compensate for tone & speed to make the speaker sound as a whole.
How does one compensate for tone & speed to make the speaker sound as a whole.
I'm also interested about the DSP used, I'm currently using class D Tripath amp
I've pretty much decided on the 26 as input stage for my EL12n outputs in my 2-stage SE amp. So I've been trying to get the best out of it.
Since I use resistor loads, getting the best sound has meant putting up the value of the anode resistor. I started with 21K. Boomy bass. Then gradually up to 39K which was OK for me since my speakers are sealed box and a bit bass-light. Bass was still a bit loose, though. So up to 47K. This made a difference, tighter bass. With 376V B+ this meant 5mA through the 26 when I'd want closer to 6mA. So looks like with a resistor load this wants 400V or so. Anyway, it looks like ideally you want 47K if you use a resistor load. Maybe even more, but 47K works. Higher than I expected, but it does make a difference.
Since I use resistor loads, getting the best sound has meant putting up the value of the anode resistor. I started with 21K. Boomy bass. Then gradually up to 39K which was OK for me since my speakers are sealed box and a bit bass-light. Bass was still a bit loose, though. So up to 47K. This made a difference, tighter bass. With 376V B+ this meant 5mA through the 26 when I'd want closer to 6mA. So looks like with a resistor load this wants 400V or so. Anyway, it looks like ideally you want 47K if you use a resistor load. Maybe even more, but 47K works. Higher than I expected, but it does make a difference.
My Nuance amp, which is also an inverted SET, also uses the 26 as an input tube. I'm using a different topology in that the plate load is provided by a Hammond 156C plate choke and I use battery grid bias.
But I'm running the 26 at about the same op point - 139v across the tube at 4.93mA.