reliable tube/mosfet hybrid amp - Page 8 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

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 16th August 2012, 11:37 AM   #71
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by vilfort View Post
Sepolansky,
Sorry for the late reply. Been busy... Yes, it can be applied to the DH500 as well. The only difference between the the DH500 and the DH200/220 is the larger voltage on the output stage and of course the fact that the 500 has 6 MOSFETs per channel.

From what I see in pictures, you have a little extra room in the DH500 for mounting a plate w/ tube sockets and the few resistors/caps needed. I was looking for a 500 on eBay, - but they seem to fetch rather high prices relative to a blown DH200 . So I have not tried yet... But looks very doable.

I have been refining the circuit a bit and changed values of some of the resistors. Broskie published a great article on the white cathode follower here: The Tube CAD Journal, August 1999 pg 1 In it (see page 4) he concludes that the plate load resistor of the top tube in the white cathode follower circuit should be Ra = rp/mu.

That seemed easy enough for the 6SN7 http://www.hifitubes.nl/weblog/wp-content/tung-sol-6sn7.pdf : 7,700/20 = 385 ohm. So a 390 ohm resistor would do nicely. To balance the circuit ala Aikido, I went for 390 ohm on the cathode of the bottom triode as well.

I have attached the updated schematic. Works like a charm and sounds very good too. Lots of detail. I now hear layers of instruments I newer heard before... With a DH500 you would have lots of power too.


Please share your findings as your project progresses.

D.
The value of Ra for white cathode follower depends on what load is the white cathode follower driving. At Tube CAD Journal you can find this formula for Ra: "Ra = (rp + 2RL)/mu"

link: "http://www.tubecad.com/2006/10/blog0083.htm"

Actually I think this circuit would sound alot better when operated in class A. I have my doubts about performance of class AB open-loop stage with just two parallel mosfets.
  Reply With Quote
Old 20th August 2012, 05:18 PM   #72
vilfort is offline vilfort  United States
diyAudio Member
 
Join Date: Feb 2010
Default Improved Tube/MOSFET circuit

This post was a little older. The evolution of this amp eventually led to using a bit of (oh no!) global feedback. As you can see from the schematic, this is now a modified white cathode follower running in class A. The power bandwitdh goes to 200Khz with a single pair of MOSFETS and to 60KHz with 3 pair.
Attached Images
File Type: png Vilfort-Hafler-Conversion-v.png (50.7 KB, 536 views)
  Reply With Quote
Old 3rd February 2016, 04:21 PM   #73
diyAudio Member
 
marc brown's Avatar
 
Join Date: Sep 2007
Location: Henderson, NV
Quote:
Originally Posted by sepolansky View Post
Thanks Denis,

I appreciate the input. I like the simplicity of the solid state portion of your circuit, the lack of global feedback and your choice of octals. While
I haven't gotten my own project to one of the front burners yet, I hope to soon.

While Broskie did "prove" the Ra = rp/mu, he seems to have ignored it in some of his subsequent circuits, something I found a bit odd. No question, the guy is a genius, and I'm sure we're all grateful for his shared insights.

I wonder about a few options, the choices you made and what sonic differences you may have heard if you played with different voltage gain circuits. Specifically, the 6SL7 in current source loaded form, did you try any other tubes here? The gain is very high and so is Cg-p, so I wondered about HF rolloff. I thought perhaps another tube, even with a cascode depletion MOSFET CCS might serve well. In the White Follower, while the 6SN7 is a very fine sounding tube, I wondered why you chose it over something like a higher gm, higher current tube such as a 6H30 or ECC99. Either of those would seem to provide more drive to overcome the input capacitance of the MOSFETs. That's something very much on my mind with 3 pair to drive.

In the output stage, I noticed no additional capacitance to equalize the n-channel and p-channel devices. SS is not my forte, so please forgive my ignorance, if such equalization is not needed in your circuit.

I plan to build two of these beasties; each of my (Tympani) bass panels is 8 ohms. I separately wired them, so I can drive them individually, in series for 16 ohms (if I do an OTL!), or in parallel for 4 ohms as the factory did. So, each channel of a DH500 will drive one 8 ohm panel.

Thanks again, Denis, this may be the circuit I needed to bring the bass impact to my system.

I promise to post progress and results as I get this under way, even if my building skills are eerily reminiscent of a third grader with a hacksaw and dull drill bits.

Stuart
Hi Stuart, did you ever get this project off the ground? I have a DH-500 that needs new driver boards. I'd love to go with tubes and like the way you and Dennis are thinking. I'm not a EE and want to get the circuit right.
thanks!
  Reply With Quote
Old 3rd February 2016, 04:25 PM   #74
diyAudio Member
 
marc brown's Avatar
 
Join Date: Sep 2007
Location: Henderson, NV
Quote:
Originally Posted by kacernator View Post
The value of Ra for white cathode follower depends on what load is the white cathode follower driving. At Tube CAD Journal you can find this formula for Ra: "Ra = (rp + 2RL)/mu"

link: "http://www.tubecad.com/2006/10/blog0083.htm"

Actually I think this circuit would sound alot better when operated in class A. I have my doubts about performance of class AB open-loop stage with just two parallel mosfets.
What changes would need to be made to get the circuit into Class A?
  Reply With Quote
Old 3rd February 2016, 05:47 PM   #75
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by marc brown View Post
What changes would need to be made to get the circuit into Class A?
I was referring to circuit in post #72. To make the output run in class A mode, you need to raise the idle bias to cca 1A - 1.5A. Obviously, this will generate lots of heat and demands better PSU for lower ripple.

If you are interested in hybrid circuit I recommend you this one.

80W Hybrid Audio Amplifier!

http://bas.elitesecurity.org/IOTA-CD.html
Attached Images
File Type: png IOTA-CD sema.png (31.4 KB, 228 views)
  Reply With Quote
Old 4th February 2016, 12:31 PM   #76
diyAudio Member
 
sepolansky's Avatar
 
Join Date: Nov 2007
Location: Maryland
Quote:
Originally Posted by marc brown View Post
Hi Stuart, did you ever get this project off the ground? I have a DH-500 that needs new driver boards. I'd love to go with tubes and like the way you and Dennis are thinking. I'm not a EE and want to get the circuit right.
thanks!
Wow, it's been a long time. Life changes forced me to pay attention to other things, but yes, I did get this off of the ground.

The design ended up being a multi-chassis solution. Two DH500's equipped with DIN connectors for inputs, Two Aikido chassis and one Aikido power supply chassis.

The Aikido chassis are made, one almost complete. Haven't yet started the power supply chassis stuffing, although the chassis is built (wood frames with plastic tops.

One DH500 is complete. It is an output stage and power supply only now.

Pictures and schematic attached. I hope it works!

I'll post more of this come spring, when I hope to get back to it.

Stuart
Attached Images
File Type: jpg 20131106_220446.jpg (754.8 KB, 186 views)
File Type: jpg 20131106_220457.jpg (661.6 KB, 162 views)
File Type: jpg 20131021_051833.jpg (647.0 KB, 144 views)
File Type: jpg 20131011_175914.jpg (485.8 KB, 45 views)
File Type: jpg 20131014_044516.jpg (801.4 KB, 53 views)
File Type: jpg 20131021_051905.jpg (740.6 KB, 61 views)
File Type: jpg 20131108_113626.jpg (650.0 KB, 59 views)
Attached Files
File Type: pdf Corrected-Hafler500--source_R.pdf (13.3 KB, 25 views)
  Reply With Quote
Old 4th February 2016, 05:28 PM   #77
diyAudio Member
 
marc brown's Avatar
 
Join Date: Sep 2007
Location: Henderson, NV
Quote:
Originally Posted by sepolansky View Post

One DH500 is complete. It is an output stage and power supply only now.

Pictures and schematic attached. I hope it works!

I'll post more of this come spring, when I hope to get back to it.

Stuart
That's very cool Stuart. Definitely update us as things progress.
  Reply With Quote
Old 4th February 2016, 09:24 PM   #78
diyAudio Member
 
sepolansky's Avatar
 
Join Date: Nov 2007
Location: Maryland
Quote:
Originally Posted by marc brown View Post
That's very cool Stuart. Definitely update us as things progress.
Thank you Mark, will do!
  Reply With Quote
Old 5th February 2016, 04:44 AM   #79
diyAudio Member
 
still4given's Avatar
 
Join Date: Oct 2004
Location: Victorville, CA
One of my very favorites.
TubSuMo
  Reply With Quote
Old 5th February 2016, 01:09 PM   #80
diyAudio Member
 
vzaichenko's Avatar
 
Join Date: Jan 2010
Location: Moscow, Russia
Send a message via Skype™ to vzaichenko
If somebody is interested, see this post for the final schematics / measurements:
TubSuMo as built

Gerbers, PCBs are available. There is even one set fully assembled / tested IPS + OPS boards for sale (2 channels set)

Great sounding amp! Let me know if you will have questions.
Attached Images
File Type: jpg 00-xDSC03437.JPG (251.4 KB, 47 views)
File Type: jpg 00-xDSC03439.JPG (331.8 KB, 49 views)
__________________
If you can't explain it simply, you don't understand it well enough (c) Albert Einstein
See my projects at VIRTUAL ZERO distortion AUDIO
  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
MOSKIDO - Hybrid Tube/MOSFET Amplifier Kashmire Pass Labs 7 22nd September 2011 08:30 PM
24V Tube IRF610 MOSFET Hybrid HPA lineup Solid State 10 23rd October 2008 02:36 AM
Hybrid Tube / Mosfet Amplifier poynton Tubes / Valves 8 10th August 2007 05:32 PM
bass guitar amp hybrid Tube/mosfet ?? partyjups Instruments and Amps 1 19th April 2004 01:08 PM


New To Site? Need Help?

All times are GMT. The time now is 04:55 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki