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

Can someone give some info on this tube circuit please?
Can someone give some info on this tube circuit please?
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 17th September 2018, 11:45 AM   #11
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Quote:
Originally Posted by georgehifi
It's from a highly regarded Japanese preamp the gain is switchable from a 1 or 2 db to 20db.
It is a simple circuit with average performance into a high impedance load, but poorer performance into a lower impedance load. Voltage gain will be switchable from 11dB to 2.2dB. Performance is limited by the choice of valve and the low supply rail voltage.
  Reply With Quote
Old 17th September 2018, 07:46 PM   #12
6A3sUMMER is online now 6A3sUMMER  United States
diyAudio Member
 
Join Date: Jun 2016
martyh,

I am surprised by you suggestion that for the two circuits, post #1 and post #4 decreasing the load resistance will null the distortion.

Would you give us a discussion on how that works on one or both of those circuits, please. Either with, or without negative feedback. Also list what distortion(s) will be nulled; 2nd, 3rd Harmonic; 2nd, 3rd Intermod, etc.

I am guessing what you are taking about is that when you reduce the load resistance on the cathode follower that its 2nd harmonic distortion goes up; and that when the cathode follower's 2nd harmonic distortion is the same percent as the input stage 2nd harmonic distortion, they will null (since they are in opposite directions, one on positive alternation, and one on the negative alternation). Of course, now with both positive and negative alternations being fore-shortened, we have 3rd Harmonic distortion at a larger percent than we had before reducing the load resistance, right?

Last edited by 6A3sUMMER; 17th September 2018 at 07:56 PM.
  Reply With Quote
Old 17th September 2018, 09:01 PM   #13
georgehifi is offline georgehifi  Australia
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
OK time to let the cat out of the bag, this is a new Japanese kit I've yet to put together, I did a swap for a Lightspeed Attenuator as I like having many different pres active and passive on hand to A/B's with at demos with the Lightspeed, for customers.

But I don't want to disadvantage it by it seeing a load that's too low for it, I've had a look and can raise my total load to 68kohm?

Doctorjohn Cheaptubeaudio: Audio Reviews and More: Review: Elekit TU-8500 Full-Function Preamp, Part I

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 17th September 2018, 11:52 PM   #14
georgehifi is offline georgehifi  Australia
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Found this on Tubecad looks to be a CCDA??

Cheers George
Attached Images
File Type: png ccda schematic.png (27.5 KB, 227 views)
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 17th September 2018, 11:54 PM   #15
rayma is online now rayma  United States
diyAudio Member
 
Join Date: Apr 2011
Quote:
Originally Posted by georgehifi View Post
Found this on Tubecad looks to be a CCDA??
Not a diff amp, but it draws approx. constant supply current. "Constant Current Draw Amplifier" So does a typical tube differential amplifier.

Click the image to open in full size.

Last edited by rayma; 18th September 2018 at 12:00 AM.
  Reply With Quote
Old 18th September 2018, 12:05 AM   #16
rayma is online now rayma  United States
diyAudio Member
 
Join Date: Apr 2011
Quote:
Originally Posted by georgehifi View Post
I don't want to disadvantage it by it seeing a load that's too low for it, I've had
a look and can raise my total load to 68kohm?
That will work, but it's best for the load to be several times larger than the 33k cathode resistor.

Last edited by rayma; 18th September 2018 at 12:09 AM.
  Reply With Quote
Old 18th September 2018, 12:27 AM   #17
georgehifi is offline georgehifi  Australia
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
So even though it's a couple hundred ohms output impedance, the 33kohm cathode resistor is the controlling factor of what it can and can't drive without any impediments.
(1:10 impedance ratio min for me, amp load should be at least 330kohm?)

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 18th September 2018, 12:34 AM   #18
rayma is online now rayma  United States
diyAudio Member
 
Join Date: Apr 2011
The output impedance is small signal, but not suitable for driving a difficult load. If too small, the load will increase the distortion. As a rule of thumb, the load should be at least 3-5 times the cathode resistor, so 100k - 170k is preferable, but the higher the better, naturally.

Last edited by rayma; 18th September 2018 at 12:39 AM.
  Reply With Quote
Old 18th September 2018, 12:40 AM   #19
georgehifi is offline georgehifi  Australia
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Quote:
Originally Posted by rayma View Post
The load (if too small) will increase distortion. As a rule of thumb, the load
should be 3-5 times the cathode resistor, so 100k - 170k is preferable.
Can the R48 R49 cathode resistor be reduced to something like 10kohms without cause other trouble and major re-jigging?

Like on Tube Cad John Broskie's CCDA: constant-current-draw amplifier

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com

Last edited by georgehifi; 18th September 2018 at 12:43 AM.
  Reply With Quote
Old 18th September 2018, 12:48 AM   #20
rayma is online now rayma  United States
diyAudio Member
 
Join Date: Apr 2011
His circuit uses higher B+ (200V vs 140V). Try 20k first, that should work. The plate current will increase by the reciprocal factor, as the grid voltage is constant. Is the power supply just passive dropping resistors? One or more of those may have to be decreased.

The input section has low plate current, another limitation of this circuit.

Last edited by rayma; 18th September 2018 at 01:07 AM.
  Reply With Quote

Reply


Can someone give some info on this tube circuit please?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Can someone give me more info about this amplifier? H3x0S Solid State 3 25th October 2013 02:29 PM
Can anyone give me the specs/Info on these; Haybrook HB1 JammyBStard Solid State 8 17th March 2010 03:43 PM
Can anyone give me the specs/Info on these; Haybrook HB1 JammyBStard Multi-Way 1 3rd January 2010 01:09 PM
Can someone give me a link to crystal info? leadbelly Parts 0 22nd March 2004 03:49 PM
Can anyone give more info on this amp? mg16 Tubes / Valves 6 8th May 2003 01:43 AM


New To Site? Need Help?

All times are GMT. The time now is 01:40 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki