This is really up my street. I've been experimenting with different DHT small tubes for 3 years in 300b SETs. In terms of input tubes I found I liked in approximately this order:
26 - my preferred option for tone and overall magic
10Y - capable of great clarity and dynamics, but I missed the 26
01A - very good, but not as magical as 26 or clear as 10Y
30sp (VT67) - surprisingly good, less microphonic than 30
46 - usually a driver tube, but very neutral with good tone
1G6G/GT - surprisingly good but very microphonic, so needs special mounting
I went with the 10Y for ages in different contexts but came back to the 26.
The implementation matters here. On the basis of listening tests I gave up resistor loads and solid state loads and went for a transformer/plate choke. 26 needs a high inductance load like 200H or more, and this is most easily found in a plate choke. I currently use a cheap solution - two Hammond 156C chokes of 150H, in series making 300H. It does the job fine, though clearly there will be more expensive and sophisticated options. I don't use a cathode bypass because I use filament bias, and the cathode resistor is just 10 ohms. I preferred filament bias to battery bias on the grid which would be my second best option. But I do use choke input plus a Rod Coleman boards for the filament - only works when it's super clean.
Like you I planned on using 10y as a driver, but when I started matching the 10Y up with interstages I surprisingly found that I preferred the tone quality of the 46. Usefully this sounded very good with the cheap but excellent Hammond 126C without cathode bypass, and also with the much more expensive Lundahl LL1692A. So I went with that. I was surprised not to be using the 10y because in AB listening tests in various other contexts it seemed to sound better than the 46. So it's really a case of getting the alchemy right.
Andy
26 - my preferred option for tone and overall magic
10Y - capable of great clarity and dynamics, but I missed the 26
01A - very good, but not as magical as 26 or clear as 10Y
30sp (VT67) - surprisingly good, less microphonic than 30
46 - usually a driver tube, but very neutral with good tone
1G6G/GT - surprisingly good but very microphonic, so needs special mounting
I went with the 10Y for ages in different contexts but came back to the 26.
The implementation matters here. On the basis of listening tests I gave up resistor loads and solid state loads and went for a transformer/plate choke. 26 needs a high inductance load like 200H or more, and this is most easily found in a plate choke. I currently use a cheap solution - two Hammond 156C chokes of 150H, in series making 300H. It does the job fine, though clearly there will be more expensive and sophisticated options. I don't use a cathode bypass because I use filament bias, and the cathode resistor is just 10 ohms. I preferred filament bias to battery bias on the grid which would be my second best option. But I do use choke input plus a Rod Coleman boards for the filament - only works when it's super clean.
Like you I planned on using 10y as a driver, but when I started matching the 10Y up with interstages I surprisingly found that I preferred the tone quality of the 46. Usefully this sounded very good with the cheap but excellent Hammond 126C without cathode bypass, and also with the much more expensive Lundahl LL1692A. So I went with that. I was surprised not to be using the 10y because in AB listening tests in various other contexts it seemed to sound better than the 46. So it's really a case of getting the alchemy right.
Andy
Holy Cow! Never seen that one. What a cool tube. What's your operating point - is it happy with around 250v on the plate?
I couldn't see any curves. Doesn't look too expensive.
Andy
Hi,
you can find the curves on electron Tube Data sheets - Search but you have look under 8012a, same tube but different base.
The tube runs fine at 250-300V@18ma using LL1660.
best regards
Karsten
you can find the curves on electron Tube Data sheets - Search but you have look under 8012a, same tube but different base.
The tube runs fine at 250-300V@18ma using LL1660.
best regards
Karsten
Not a first choice for me. Middle of the pack. 26, 01A, 10y all better, and no doubt also the 30sp (VT67)
andy
If you're in London, you could drop in and see my vast collection of DHTs and some amps and preamps I've made with them!! I'm sure I can match any prices on tubes if you want some. I'm in West Kensington if that's any help. We might not be too far away, and we could talk about choices. I'm on 020 7602 2707
andy
andy
Hi Andy, that would be fantastic. I live in Balham, so we are not far away. I'm more than happy to pop in and look/listen to your amps. I have followed you posts with a lot of interest since I'm planning to build an DHT pre-amp once I finish the belated 45 SET amplifier which I'm currently working on.
I'm currently in Argentina staying with my family as we are going through a difficult time and returning to London next week, so i will get in touch as soon I get back on track with the daily grind...
I mentioned the CX-112a as I know someone here in Buenos Aires who has a big stock of them and is willing to sell me some at a good price.
I do have many 27, and some used 26, which are a bit worn out.
I was also thinking of using 4P1L which are very linear.
Anyway, open to suggestions....
Cheers,
Ale
Hello Andy,
thanks for your great contribution (and the others DIYers...) on the 26 pre thread : very interesting !
I love so the 26 and I built a pre, with my reduced knowledge and the aid of an english friend designer who learned me the great benefit of these triodes... and I am very happy with it (inspiration of the VT 52/Jim de Kort schema simple RC load with tube damper rectification and a current regulated filament, classical cathode bias).
I will try plate choke and filament bias, but I enjoy listen to the 26 too mutch
I have tried the 46 pré so and it was quiet good, but not as mutch as the 26...
It drive my classical 300B amp with 6SN7 and Tango XE-60/5K trans. on VOTT system.
Can you post me the schema of your 46 + 300B amp ? It look very interesting with the 26 pre...
Thanks
B r u n o
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