Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

#26 pre amp
#26 pre amp
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 22nd March 2011, 05:07 PM   #921
Vinylsavor is offline Vinylsavor  Germany
diyAudio Member
 
Vinylsavor's Avatar
 
Join Date: Feb 2002
Location: Lindau
Hi Andy,

nice job!

I agree with others that the 0,1uF cap is a bit on the low side unless your power amp has very high input impedance.

Why the 1k grid stopper resistor? 26s have low transconductance and low mu. You have to really try hard to get them to oscillate. No grid stopper necessary with those.

Thomas
__________________
http://vinylsavor.blogspot.com/
  Reply With Quote
Old 22nd March 2011, 07:58 PM   #922
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
Quote:
Originally Posted by Vinylsavor View Post
No grid stopper necessary with those.
Good to know!

What do you think about that operating point, Thomas?
  Reply With Quote
Old 22nd March 2011, 09:37 PM   #923
andyjevans is offline andyjevans  United Kingdom
diyAudio Member
 
Join Date: Sep 2003
Location: London
I think the input grid resistor is 560K on my power amp - that or 270K, can't remember.

Yes, the 0.1uf is probably low. I have a larger FT-3 one which would probably fit in the space - just used what came to hand.

Keep the ideas coming! The 156C plate chokes are each 8mA and 150H, 3.7K resistance.

Yes - those cathode resistors. I went through about 8 different types before I settled on those - they came from USA and were on ebay. Redundant stock Dale I believe. Best I tried.

Andy
  Reply With Quote
Old 25th March 2011, 04:03 PM   #924
dvb projekt is offline dvb projekt  Germany
diyAudio Member
 
dvb projekt's Avatar
 
Join Date: Feb 2009
Location: Willich, Germany
#26 pre amp
Now the main parts for my pre arrived today

Click the image to open in full size.

Two Arcturus 126 and one Telefunken AZ1 mash. Rods filament supply also arrived.

Lets wait to the results from AE-Europe to make a replica UTC HA-133...
__________________
Reference TDA1541A DAC project PCBs / Tube-I-zator PCB
Stock status in my Blog
  Reply With Quote
Old 25th March 2011, 04:20 PM   #925
merlin el mago is offline merlin el mago
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Looks very good.

How much will cost the AE-Europe replica?
  Reply With Quote
Old 25th March 2011, 05:18 PM   #926
dvb projekt is offline dvb projekt  Germany
diyAudio Member
 
dvb projekt's Avatar
 
Join Date: Feb 2009
Location: Willich, Germany
#26 pre amp
I gave them all needed parameters and waiting to the results.
Perhaps they could make a bit better with actual materials

I am also planning a top version with silver secondary windings.
__________________
Reference TDA1541A DAC project PCBs / Tube-I-zator PCB
Stock status in my Blog
  Reply With Quote
Old 29th March 2011, 07:43 PM   #927
coolzero is offline coolzero  Sri Lanka
diyAudio Member
 
coolzero's Avatar
 
Join Date: Sep 2009
Location: UAE
Quote:
Originally Posted by andyjevans View Post
Who's using plate chokes in their 26 preamps? I've been playing about with four 156C Hammond chokes - 150H at 8mA - using them in series as pairs. I put them bottom-to-bottom and wired them out of phase since I read that somewhere. Resistance in series is 7K.

Sound is damn good! Quite surprising. I'm using Teflon FT-3 output caps and filament bias with 10 ohm resistors. 140v on the plate, 10v on cathode. Rod Coleman filament supply - his original one which was posted early on in these pages. This is a really cheap and effective way to build a 26 preamp, except that in my case I'm using choke input supply to Rod's boards with a 280mH choke, 2.7A, and 20,000uf caps.

Now I know that this works I can look at some more exotic plate chokes!! I was thinking output transformer, but Thomas is always telling me to have more inductance and it really does sound very clean.

Andy
Andy,

Plate chokes gives far better sound than any other plate loads I tried on my 26 minus output transformers which I haven't tried yet. I use EP 200H chokes with slightly hotter parameters than yours. Indeed my 26 pre gives great sound with all these including Rods/SALAS PSU's.
  Reply With Quote
Old 5th April 2011, 03:58 PM   #928
dvb projekt is offline dvb projekt  Germany
diyAudio Member
 
dvb projekt's Avatar
 
Join Date: Feb 2009
Location: Willich, Germany
#26 pre amp
Quote:
Originally Posted by merlin el mago View Post
Looks very good.

How much will cost the AE-Europe replica?
Got the refusal from AE-Europe today. So no UTC HA-133 replica

Any concerns to use the Lundahl LL1660/5mA for the #26 with 150V B+ and -9V Bias?
__________________
Reference TDA1541A DAC project PCBs / Tube-I-zator PCB
Stock status in my Blog
  Reply With Quote
Old 5th April 2011, 04:28 PM   #929
Bas Horneman is offline Bas Horneman  Netherlands
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Quote:
Got the refusal from AE-Europe today. So no UTC HA-133 replica
That must be a bummer for you?

How about the Lundahl 1680. a Replacement built for the UTC ls-27

http://www.lundahl.se/pdfs/datash/1680.pdf
__________________
If you can see the speaker cone move...it's not hifi.
  Reply With Quote
Old 5th April 2011, 04:31 PM   #930
andyjevans is offline andyjevans  United Kingdom
diyAudio Member
 
Join Date: Sep 2003
Location: London
I have the LL1660/5mA. I used it in 1:1 to keep the gain. I think I slightly preferred a plate choke.

Andy
  Reply With Quote

Reply


#26 pre ampHide 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

Forum Jump


New To Site? Need Help?

All times are GMT. The time now is 03:33 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki