3A5 thoughts - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 12th October 2009, 09:11 PM   #1
Ryssen is offline Ryssen  Sweden
diyAudio Member
 
Ryssen's Avatar
 
Join Date: Dec 2003
Location: Sweden--> Here
Default 3A5 thoughts

Have anyone built anything with these,how is the sound?
Thought of maybee use them as an outputstage after a DAC (CS4398)
But I wonder if they are worthy..
__________________
Regards Åke
  Reply With Quote
Old 13th October 2009, 11:28 AM   #2
diyAudio Member
 
Join Date: May 2007
Hey Ryssen,
Don't think it's worth adding a tube at all. Differential output is 2,4Vrms. Just add a balanced to SE 2:1 transformer, Lundahl off course, and you're done. Still you have over 1V signal level and acceptably low Zout.

andyjevans have tried the 3A5 as a preamp and reported it sounding good. Probably the halves should be parallelled(like in a 2A3) and fed to a 4:1 transformer.
  Reply With Quote
Old 13th October 2009, 03:59 PM   #3
Ryssen is offline Ryssen  Sweden
diyAudio Member
 
Ryssen's Avatar
 
Join Date: Dec 2003
Location: Sweden--> Here
Quote:
Don't think it's worth adding a tube at all.
Thats what I thought..

Quote:
Just add a balanced to SE 2:1 transformer, Lundahl off course, and you´re done.
How much current should the trafo withstand?
__________________
Regards Åke

Last edited by Ryssen; 13th October 2009 at 04:29 PM.
  Reply With Quote
Old 13th October 2009, 05:00 PM   #4
diyAudio Member
 
Join Date: May 2007
As the input is balanced there is no DC-current flowing. A LL1676 would probably be a good choice.
  Reply With Quote
Old 13th October 2009, 05:21 PM   #5
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
Quote:
Originally Posted by revintage View Post
Hey Ryssen,
Don´t think it´s worth adding a tube at all. Differential output is 2,4Vrms. Just add a balanced to SE 2:1 transformer, Lundahl off course, and you´re done. Still you have over 1V signal level and acceptably low Zout.

andyjevans have tried the 3A5 as a preamp and reported it sounding good. Probably the halves should be parallelled(like in a 2A3) and fed to a 4:1 transformer.
I recall a little while ago some people pointed out the paralleling as not a good idea in a thread over at audioasylum/tubediy. Might be better off just using each half for a channel. In the end, you trying both setups will be the best answer.
  Reply With Quote
Old 13th October 2009, 05:32 PM   #6
diyAudio Member
 
Join Date: May 2007
ikoflexer,
Know how a 2A3, 6B4G or 300B is built? Also with 3A5´s common-cathode, one for each channel probably isn´t the best idea.

Last edited by revintage; 13th October 2009 at 05:36 PM.
  Reply With Quote
Old 13th October 2009, 05:40 PM   #7
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
Proof by similarity sometimes works, sometimes doesn't. That I know.
  Reply With Quote
Old 14th October 2009, 09:20 AM   #8
diyAudio Member
 
Join Date: Sep 2003
Location: London
Hi,

I personally like DHT small triodes as DAC outputs. Cheap version if you have a balanced DAC is something like 3a5 or 1J6 into a Hammond 124b. 3-1 stepdown. Doesn't give you much more than unity gain with a stepdown, though. If you need gain I'd go with the 2C22 - one of the few indirectly heated tubes I'd think of using.

But let's go for some quality here! Use the 26. Cheap and plentiful and close to the best you'll get. Arguably the 10y is better and the 01A is as good in lighter more airy way, but the 26 is just one of the absolute great all-time tubes. WAY better than any 6SN7, for instance. The 26 is a Hall of Fame tube. So learn to use it and you won't regret it. For filament just use a big cap (15,000 or similar) and a LM1084 configured as current source, with a 1.25 ohm 5 watt (or more, like 12W is good) resistor between gate and output, and positive taken from the gate. And a decent heatsink like 2 to 3 ins square at least. And a 6v secondary transformer. Nothing more fancy than that and you're good to go.

To make the 26 sing, use an active plate load, like two IXYS 10M45 in cascode. Search the forum for designs, but basically you want 1k gate resistors right on the LM1084 chip. Start the sense resistor around 1K and go down until you're right. I've been trying red LEDs in the cathode of small tubes - 1.7v so you may need a few! The above is assuming single ended. For balance I guess use a CCS in the cathodes. Then you can use a transformer, parafeed a transformer or use cap out. Dave Davenport has a nice parafeed balanced line stage design on the K&K website. Tells you all you need to know really.

good luck

andy

Last edited by andyjevans; 14th October 2009 at 09:22 AM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
My thoughts. And nothing else. Gyuri The Lounge 229 5th September 2014 01:48 PM
813 Thoughts Steven-H Tubes / Valves 40 26th January 2008 02:24 AM
HT thoughts bjackson Multi-Way 5 8th February 2006 05:18 PM
Some DAC thoughts Bernhard Digital Source 9 31st January 2005 02:54 PM


New To Site? Need Help?

All times are GMT. The time now is 10:25 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2