Go Back   Home > Forums > Amplifiers > Headphone Systems

Headphone Systems Everything to do with Headphones

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 26th September 2013, 09:54 AM   #1
DeeLuxx is offline DeeLuxx  New Zealand
diyAudio Member
 
Join Date: Jun 2012
Default Moskido Hybrid headphone amplifier! Help needed

Hi there,

I am working on building a copy of the headphone version of the Moskido amplifier that was posted on The Tube Cad Journal some time ago here - MOSKIDO Amplifiers

In particular, this circuit -

Click the image to open in full size.

I understand the operation of the circuit and from what I can see, it should work. I plan on making my own pcb using smd parts, which will be done soon.

Before i do though, was wondering if you guys could offer any suggestions? Attached is my altium schematic, will post the pcb shortly and can give the entire project file to you if you want. let me know!

Thanks in advance!
Attached Files
File Type: pdf Complete circuit.pdf (150.8 KB, 46 views)
  Reply With Quote
Old 12th October 2013, 04:16 AM   #2
diyAudio Member
 
Join Date: Feb 2005
Location: Melbourne, Aust
I'm a bit puzzled about what advantage(s) the more 'complicated' heater arrangement adds to the cct - I wouldn't , particularly when it ties in directly to the output buffer - any details before you do a pcb, or perhaps optional links/pads?

An other thing you could consider with this cct is to develop a good quality +/- 24 volt supply and use an input cap to V1 in order to get rid of the 'problem' output electro cap - a 'better sounding' compromise, IMHO.

... my 2 cents,
__________________
... jh
  Reply With Quote
Old 15th October 2013, 12:02 AM   #3
diyAudio Member
 
Join Date: Nov 2004
Location: Germany
Quote:
Originally Posted by jameshillj View Post
I'm a bit puzzled about what advantage(s) the more 'complicated' heater arrangement adds to the cct - I wouldn't , particularly when it ties in directly to the output buffer - any details before you do a pcb, or perhaps optional links/pads?
The BUF634 can't take 48 V, but the resistance of the heaters conveniently provides 12 V and 36 V in steady state, so they used those as a regulator reference. I hope the buffer has better PSRR than the input circuitry.
Quote:
Originally Posted by jameshillj View Post
An other thing you could consider with this cct is to develop a good quality +/- 24 volt supply and use an input cap to V1 in order to get rid of the 'problem' output electro cap - a 'better sounding' compromise, IMHO.
Generally speaking you're right, but great caution is required when adapting single-supply circuits to split supply, or else you may open up a PSRR can of worms. Here's an example that I discussed recently. I would assume this circuit to have very similar issues on a split supply.
  Reply With Quote
Old 15th October 2013, 05:21 AM   #4
diyAudio Member
 
Join Date: Feb 2005
Location: Melbourne, Aust
Ah, I see! And I do think those BUFs are good at PSSR.

Yeah, not an automatic success story with diff rail voltages - have stuffed this up myself!

All the best ...
__________________
... jh
  Reply With Quote
Old 17th October 2013, 08:34 PM   #5
diyAudio Member
 
Join Date: Sep 2012
Why not use more voltage to the valves and use an independent source for the buf? more voltage to the valves will give a more linear operation
  Reply With Quote
Old 19th October 2013, 06:52 PM   #6
diyAudio Member
 
Join Date: Jan 2007
up
  Reply With Quote
Old 19th October 2013, 09:00 PM   #7
diyAudio Member
 
Join Date: Nov 2004
Location: Germany
Quote:
Originally Posted by orlando2989 View Post
Why not use more voltage to the valves and use an independent source for the buf? more voltage to the valves will give a more linear operation
"Simplicity" probably is the answer here. It would require another transformer secondary, rectifier etc.

You're right though. This would also be an opportunity to use fancier rail filtering on the high supply (which would have to supply a fair bit less current), while the BUF could be operated from a +25.2 or +/- 12.6 V supply with rearranged heaters (12.6 V is the nominal heater voltage for a 12AU7 and easily obtained by shifting a 12 V reg up with a silicon diode).

Last edited by sgrossklass; 19th October 2013 at 09:03 PM.
  Reply With Quote
Old 20th October 2013, 11:29 PM   #8
DeeLuxx is offline DeeLuxx  New Zealand
diyAudio Member
 
Join Date: Jun 2012
Thanks for the information!

Just as an update, i did in fact build the entire circuit with the values specified in the first post.

Interesting nobody noticed that the heaters take 12.6v in series (so two tubes would drop 25.2 volts total) but the circuit has 48v going into the two tubes. Anyway i added some power resistors in series with the heaters to bring the heater voltage to 12.6 per tube.

As for performance, the amplifier clips horribly when supply voltage APPROACHES 48v.

Best functionality is at 30v it seems. not really sure what the story is but will look into it.

Any ideas?
  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


New To Site? Need Help?

All times are GMT. The time now is 10:30 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