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 11th February 2005, 04:22 PM   #1
Tea is offline Tea  Hong Kong
diyAudio Member
 
Join Date: Aug 2002
Location: Hong Kong
Question Output current of this CAT SL-1 schematic ?

Hi all, I want to DIY a tube preamp to drive my vintage MC240 tube amp AND my AKG 271s headphone, since my headphone is only 56 ohm so I need a high current and low impedance output preamp.

My question is :

1: What is the output current and impedance of the following CAT SL-1 schematic ?

2: How do I know the output current and impedance for difference schematic or which part should I check ?

3: If this schematic do not have high enough current or low enough impedance, can I modifly it ? If yes which part should I modifly ?

Thank you very much for the help.
Attached Images
File Type: jpg ls26.jpg (86.4 KB, 372 views)
  Reply With Quote
Old 14th February 2005, 12:23 PM   #2
diyAudio Member
 
Join Date: Oct 2004
Output impedance of the LS-26 should be around 80 Ohms, and maximum output current is around 5mA. So this one is not for you (also it does sound very good; it is actually the one I am using).

Output impedance in this case is affected by the 50 Ohms series resistor + depends on tube and feedback (basically, the 100 Ohms output impedance of the tube is "virtually" reduced by the amplifier feedback) .

Current capability depends on the tube used: the 6922 will give you roughly 10mA, ie 5 mA bias + 5mA current.

Additionally, driving a 56 Ohm load requires a very large capacitor in the output (cutoff frequency is f= 1/ (2*PI*R*C) where R = 56 Ohms).

Finally, this preamp has a huge (26dB,i.e. x20) gain.

So it is not for your headphone!

If you really want to use this type of schematic, then you would have to change the 6922 for a large double triode (ex 6AS7 ) or for two pentodes (SV83/ EL84) + use electrolytics for the output cap.

You'd be much better off using a triode SE amp with a right chosen output stage transformer.

Eric
  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
COD - Current Output DAC BrianDonegan Twisted Pear 150 27th March 2013 04:15 PM
Current best Schematic/PCB Software in the $2,000 USD and under range alvaius Everything Else 28 22nd February 2009 08:35 PM
current sensing relay schematic? ojcool Car Audio 4 20th June 2008 03:42 PM
current sourced cascoded BLS schematic SteveG Pass Labs 48 24th July 2002 07:16 PM


New To Site? Need Help?

All times are GMT. The time now is 12:57 AM.


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