boraomega´s STACATO HeadPhoneAmplifier - diyAudio
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 3rd June 2012, 07:19 PM   #1
44250 is offline 44250  Serbia
diyAudio Member
 
44250's Avatar
 
Join Date: Jan 2011
Location: Ugrinovci-Zemun-BELGRADE
Send a message via AIM to 44250
Arrow boraomega´s STACATO HeadPhoneAmplifier

This is one of two head-amplifiers that i have built in a same time. I have got the scheme somewhere from the internet with familiar signature of dr.Borivoje Jagodić so i have saved it in my computer.

I don´t have any experience in headphone amplifiers or in a headphone themselves,but the difference between say usuall headphone output from commercial devices is huge. I beleive that large part of it´s directivity owes to a direct conection with speakers,without any resistors between the amplifier it self and headphones.

Headphones are Sony MDR-CD480 ,they are not hi-fi or hi-end but for me they are still a step forward from what i have had before.

I will put a schematics of it if the boraomega agrees,hope he will notice this thread. The pcb is something that each of us will have to ask from him directly,that is the way i got them.

Has someone else did this headphone amplifier too,any sound impressions?

(the transformer from the amplifier will be changed from 2x11Vac EI to a 2x18Vac toroid,to get smaller magnetic dissipation inside an inclosure and the right power voltage of +/-24Vdc,now it is about +/-16Vdc)
Attached Images
File Type: jpg Slika371.jpg (323.9 KB, 560 views)
File Type: jpg Slika373.jpg (291.7 KB, 501 views)
File Type: jpg Slika375.jpg (338.6 KB, 469 views)
File Type: jpg Slika376.jpg (267.2 KB, 448 views)
File Type: jpg Slika377.jpg (261.7 KB, 409 views)
File Type: jpg Slika379.jpg (229.4 KB, 91 views)
  Reply With Quote
Old 3rd June 2012, 09:42 PM   #2
diyAudio Member
 
Join Date: Nov 2004
Location: Germany
Quote:
Originally Posted by 44250 View Post
I don´t have any experience in headphone amplifiers or in a headphone themselves,but the difference between say usuall headphone output from commercial devices is huge. I beleive that large part of it´s directivity owes to a direct conection with speakers,without any resistors between the amplifier it self and headphones.
Indeed, it is output resistance that may have a significant influence on sound. It forms a voltage divider with the generally non-constant headphone impedance.

A few examples, going from non-critical to very fussy:
Click the image to open in full size.

The vast majority of headphones is built to sound best with a low-impedance output, though the occasional exception does exist.

Output resistance in commercial integrated amplifiers and receivers commonly ranges from 330 to 470 ohms, while dedicated headphone amps tend to exhibit no more than a about 100 ohms at best (values around 10 ohms to <1 ohm are common).
  Reply With Quote
Old 3rd June 2012, 11:09 PM   #3
44250 is offline 44250  Serbia
diyAudio Member
 
44250's Avatar
 
Join Date: Jan 2011
Location: Ugrinovci-Zemun-BELGRADE
Send a message via AIM to 44250
Default STACCATO

I have received an information that the right name of this amplifier is STACCATO with two " C " ,so i would like to ask the moderators of this forum please to change the title,or to point me how to do it myself.
.
.
By the way,here is the schematic but for pcb and layout you should ask Borivoje Jagodic - boraomega himself.
.
.
.
Thanks for this interesting text sgrossklass!
Attached Images
File Type: jpg Staccato.JPG (59.3 KB, 373 views)

Last edited by 44250; 3rd June 2012 at 11:24 PM. Reason: Mistake...
  Reply With Quote
Old 4th June 2012, 10:59 PM   #4
diyAudio Member
 
Join Date: Nov 2004
Location: Germany
That's pretty much a classic "Blameless" topology with a Darlington VAS. As shown, it is best suited for driving higher-impedance or insensitive headphones due to ~21 dB gain.

There are several refinements I could think of:

1. There is no provision of RF filtering at the input (or output), potentially giving problems in areas of high radio/TV fieldstrengths.

2. Given the decent input stage current, feedback resistors (22k/2k2) could easily be chosen a factor of 2 or 3 lower for lowest residual noise.

3. The connection to feedback between the two 820 ohm resistors actually is not beneficial and should be removed for best performance with real-life loads.

4. One could get a little more fancy with part choices, e.g. use transistors with higher Early voltage and lower Cob for VAS and current sources, and ones with more constant beta for drivers.

5. For applications with considerably reduced gain, best replace 2k7 in the VAS with an appropriately sized current source for much reduced common-mode distortion.

6. A tail-driven cascode in the LTP could be used to reduce nonlinear input capacitance.
  Reply With Quote
Old 4th June 2012, 11:17 PM   #5
44250 is offline 44250  Serbia
diyAudio Member
 
44250's Avatar
 
Join Date: Jan 2011
Location: Ugrinovci-Zemun-BELGRADE
Send a message via AIM to 44250
Your first sentence was almost the same as boraomega's in a feturn mail when i asked him if i could post the schematic here. He actually said that someone will imediately tell me that it is pretty basic topology,but i haven't hoped for such detailed upgrade suggestions! When i read some more (and more) books i will better understand these sentences! Thank you wery much for posting here!

What would be actions of preventing from radio frequencies in input and output?
  Reply With Quote
Old 6th June 2012, 05:37 PM   #6
diyAudio Member
 
Join Date: Nov 2004
Location: Germany
Quote:
Originally Posted by 44250 View Post
What would be actions of preventing from radio frequencies in input and output?
You can try the following:

* connect input/output ground to chassis vs. ~10 nF ceramic (so the chassis has a better chance of acting as a Faraday cage)
* 100 pF ceramic to ground directly at each input...
* ... followed by a about 1 kOhm in series and ~220 pF to ground, and maybe another 220R to input transistor base. (If there's a volume pot, that goes before the 220R. If connected by a long cable, that one may need special attention in the form of a common-mode choke.)
* The output tends to be relatively uncritical, as there typically is a Zobel network that keeps RF impedance fairly low anyway (try 47R - 10n or so), and possibly even a series L (with parallel R) when going to the output jack.

These are about the standard precautions for keeping MW and higher out. If you have issues with longwave signals, more drastic measures may be needed.

You can look at the input circuitry of a Kenwood L-1000M power amp to get a glimpse of how a fancier solution might look like.

Another trick that allows larger-value input capacitors is using input bootstrapping at audio frequencies. That's a little advanced though and not recommended for the novice.

Unfortunately just about the only test of effectiveness is using the component in a known harsh RF environment or conducting tests in an EMC measurement chamber ($$$). Of course one can test whether the component is audibly bothered by a mobile phone transmitting or DECT/WLAN, but that's far from comprehensive.

You can also do something against generating unwanted RF emissions within the component itself:

If you have used an ordinary silicon rectifier (or ordinary discrete rectifier diodes), place a 10..100 nF film capacitor in parallel to each diode. Alternatively, use fast recovery types.

A standard, non-bypassed rectifier can be quite a buzzy affair on the AM bands at higher current (esp. because of capacitor charging).

Last edited by sgrossklass; 6th June 2012 at 05:47 PM.
  Reply With Quote
Old 6th June 2012, 10:29 PM   #7
44250 is offline 44250  Serbia
diyAudio Member
 
44250's Avatar
 
Join Date: Jan 2011
Location: Ugrinovci-Zemun-BELGRADE
Send a message via AIM to 44250
Quote:
Originally Posted by sgrossklass View Post
You can try the following:

* connect input/output ground to chassis vs. ~10 nF ceramic (so the chassis has a better chance of acting as a Faraday cage)
* 100 pF ceramic to ground directly at each input...
* ... followed by a about 1 kOhm in series and ~220 pF to ground, and maybe another 220R to input transistor base. (If there's a volume pot, that goes before the 220R. If connected by a long cable, that one may need special attention in the form of a common-mode choke.)
* The output tends to be relatively uncritical, as there typically is a Zobel network that keeps RF impedance fairly low anyway (try 47R - 10n or so), and possibly even a series L (with parallel R) when going to the output jack.

These are about the standard precautions for keeping MW and higher out. If you have issues with longwave signals, more drastic measures may be needed.

You can look at the input circuitry of a Kenwood L-1000M power amp to get a glimpse of how a fancier solution might look like.

Another trick that allows larger-value input capacitors is using input bootstrapping at audio frequencies. That's a little advanced though and not recommended for the novice.

Unfortunately just about the only test of effectiveness is using the component in a known harsh RF environment or conducting tests in an EMC measurement chamber ($$$). Of course one can test whether the component is audibly bothered by a mobile phone transmitting or DECT/WLAN, but that's far from comprehensive.

You can also do something against generating unwanted RF emissions within the component itself:

If you have used an ordinary silicon rectifier (or ordinary discrete rectifier diodes), place a 10..100 nF film capacitor in parallel to each diode. Alternatively, use fast recovery types.

A standard, non-bypassed rectifier can be quite a buzzy affair on the AM bands at higher current (esp. because of capacitor charging).
Thank you so much,i will write this down to a paper and than do it in practise,part by part!
  Reply With Quote
Old 7th June 2012, 04:21 AM   #8
Jay is offline Jay  Indonesia
diyAudio Member
 
Join Date: Feb 2003
Location: Jakarta
Quote:
Originally Posted by sgrossklass View Post
You can try the following:
* connect input/output ground to chassis vs. ~10 nF ceramic (so the chassis has a better chance of acting as a Faraday cage)
* 100 pF ceramic to ground directly at each input...
* ... followed by a about 1 kOhm in series and ~220 pF to ground, and maybe another 220R to input transistor base. (If there's a volume pot, that goes before the 220R. If connected by a long cable, that one may need special attention in the form of a common-mode choke.)
* The output tends to be relatively uncritical, as there typically is a Zobel network that keeps RF impedance fairly low anyway (try 47R - 10n or so), and possibly even a series L (with parallel R) when going to the output jack.
Precautions and compensations is an art. You can make the amp bullet proof and sound like a public address amplifiers.

Musical Fidelity A1 is very popular for it's reputation to go frequently into repair shops. I didn't even want to connect it to my main speakers...

But Boraomega modification to the MFA1 removes many compensation schemes! I think that is cool...
  Reply With Quote
Old 7th June 2012, 12:20 PM   #9
44250 is offline 44250  Serbia
diyAudio Member
 
44250's Avatar
 
Join Date: Jan 2011
Location: Ugrinovci-Zemun-BELGRADE
Send a message via AIM to 44250
Today it will get a proper 30VA toroid transformer with 2x18Vac secondary voltage, than i'll see how it will behave. Since it has +/- 24V supply,i guess that it wouldn't be so bad idea to put some dc-protection inside. I'm thinking about Elliot Soundwesthost Project 33. Would this be a good idea or not so needed device?
  Reply With Quote
Old 7th June 2012, 07:01 PM   #10
44250 is offline 44250  Serbia
diyAudio Member
 
44250's Avatar
 
Join Date: Jan 2011
Location: Ugrinovci-Zemun-BELGRADE
Send a message via AIM to 44250
Default finnished for now...

It is finnished at least for now. Today it got his 30VA 2x18Vac toroid transformer and +/-24Vdc supply,quescent current of 70mA and much of the noise that existed before dissapiared. I´d say it is now fully operational amplifier,and it will stay like this i´d say for a long long time.

on a first picture is how it looks like now,
on a second is a temperature of a heatsink,
third would be quiscient currents per channel (mV on 1R resistors),
fourth is a dc-offset on one channel and
fifth is dc-offset on the other channel. That could be better if i used multiturn trim-pots instead regular. Untill something else comes to my mind (maybe input pot and dc-protection...) this will be it.
Attached Images
File Type: jpg Slika385.jpg (131.6 KB, 331 views)
File Type: jpg Slika386.jpg (103.4 KB, 164 views)
File Type: jpg Slika387.jpg (132.8 KB, 146 views)
File Type: jpg Slika388.jpg (98.5 KB, 145 views)
File Type: jpg Slika389.jpg (104.8 KB, 144 views)
  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
legend master amplifier by boraomega black Solid State 16 17th May 2013 11:45 PM
GB for PCB-s of Dr Jagodic (boraomega) designs boraomega Group Buys 2 30th July 2009 10:39 PM
OTL Headphoneamplifier with 12AU7 or 12AX7 Mr. Triatic Tubes / Valves 7 25th March 2003 05:26 PM


New To Site? Need Help?

All times are GMT. The time now is 09:18 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