Best input DHT tube?

neskor · 10th June 2011, 06:51 AM

Any suggestion for DHT input tube for 10Y IT 300B amplifier?
Beside 26

andyjevans · 10th June 2011, 08:12 AM

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

neskor · 10th June 2011, 08:20 AM

Thanx Andy!
I was waiting for your answer

211hojbjerg · 10th June 2011, 07:59 PM

I'm using 8025a in my preamp, it is a great sounding DHT that tube can be used as driver as well for 300b. the tube has white filament like 10Y.

best
karsten

neskor · 10th June 2011, 08:20 PM

it looks cool

Vinylsavor · 10th June 2011, 09:06 PM

Hi!

I always use step up input transformers with all DHT amps and stick to 2 stages. Of course this requires a preamp with low enough output impedance to drive the input transformer

Thomas

neskor · 10th June 2011, 09:09 PM

What kind of input transformer?

Vinylsavor · 10th June 2011, 09:15 PM

Hi!

Lundahl LL7903 works nicely for me

Thomas

andyjevans · 10th June 2011, 09:16 PM

Quote:

Originally Posted by 211hojbjerg

I'm using 8025a in my preamp, it is a great sounding DHT that tube can be used as driver as well for 300b. the tube has white filament like 10Y.

best
karsten

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

neskor · 10th June 2011, 09:17 PM

I have LL1636, can I use that?

10th June 2011, 06:51 AM	#1
neskor diyAudio Member Join Date: May 2008	Best input DHT tube? Any suggestion for DHT input tube for 10Y IT 300B amplifier? Beside 26

10th June 2011, 09:06 PM	#6
Vinylsavor diyAudio Member Join Date: Feb 2002 Location: Lindau	Hi! I always use step up input transformers with all DHT amps and stick to 2 stages. Of course this requires a preamp with low enough output impedance to drive the input transformer Thomas __________________ http://vinylsavor.blogspot.com/

10th June 2011, 09:15 PM	#8
Vinylsavor diyAudio Member Join Date: Feb 2002 Location: Lindau	Hi! Lundahl LL7903 works nicely for me Thomas __________________ http://vinylsavor.blogspot.com/

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
HQ-DHT (All tube DHT amli) 26-45-2A3	quanghao	Tubes / Valves	33	9th November 2011 07:27 PM
For sale - several audiophile DHT tube amp/preamp projects (UK)	andyjevans	Swap Meet	9	16th December 2009 03:49 PM
F* amp VS Single Ended DHT tube amp	xecluded	Pass Labs	15	11th August 2009 07:59 PM
Input stage tube	Steen Bentzen	Tubes / Valves	2	6th October 2005 03:39 PM
input/driver tube	brsanko	Tubes / Valves	0	13th January 2004 07:18 AM

10th June 2011, 08:12 AM	#2
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	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

10th June 2011, 08:20 AM	#3
neskor diyAudio Member Join Date: May 2008	Thanx Andy! I was waiting for your answer

10th June 2011, 07:59 PM	#4
211hojbjerg diyAudio Member Join Date: May 2010	I'm using 8025a in my preamp, it is a great sounding DHT that tube can be used as driver as well for 300b. the tube has white filament like 10Y. best karsten

10th June 2011, 08:20 PM	#5
neskor diyAudio Member Join Date: May 2008	it looks cool

10th June 2011, 09:09 PM	#7
neskor diyAudio Member Join Date: May 2008	What kind of input transformer?

10th June 2011, 09:17 PM	#10
neskor diyAudio Member Join Date: May 2008	I have LL1636, can I use that?

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read