... a sort of "pizza connection"?!
Hi baggerbole,
I'm sorry that you feel unsatisfied from this circuit.
Besides Stefano's advices, keep in mind that this kind of circuit is quite sensitive to component quality.
Furthermore you could consider to bypass the battery pack with low-ESR electrolytic capacitors and try small value (plastic) ones.
The sound sign you described is quite the opposite I experienced with this amplifier.
Please let me know
All the best
Marcello
I can second that....mine is the one in my avatar as it happens.
At the moment I'm rebuilding my main amp (pp KT88) and so I'm using my mini-zen headphone amp to run my speakers (B&W 309). Pretty much stock circuit, and does a very good job of it considering!
By the way, I thought I was immune to wiring mistakes too:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=41231
Good luck,
Steve
hi guys,
at first: The sound is still terrible
And after several checks i mention to say that the amp seems to work correct. I´ve done some additional measurements with 150mA bias current and a 75Ohm load at 24V supply.
Please have a look at them and give me your comments.
I know that squarewaves are a hard food for an amp, but the sinwave (one chanel inverted) is also not really symmetrical from input to output. May be I have to widen the bandwidth (or to give up this project)?
greetings from despaired Bernd
at first: The sound is still terrible
And after several checks i mention to say that the amp seems to work correct. I´ve done some additional measurements with 150mA bias current and a 75Ohm load at 24V supply.
Please have a look at them and give me your comments.
I know that squarewaves are a hard food for an amp, but the sinwave (one chanel inverted) is also not really symmetrical from input to output. May be I have to widen the bandwidth (or to give up this project)?
greetings from despaired Bernd
Bernd,
I've seen your screenshots, and they look right to me.
The 10KHz square wave behaviour is due to the limited bandpass of this circuit, in my unit the square wave, even if asymmetrical, is a bit "faster".
Anyway, I dan't think that this could lead to a "terrible" sound.
Check your components' quality (surplus caps?!). Or more simple, this could not be "your" sound, but believe me, this circuit topology hardly leads to such an "hard" sound...
Marcello
Post Scriptum: the output load is made by a 33R non-inductive resistor
I've seen your screenshots, and they look right to me.
The 10KHz square wave behaviour is due to the limited bandpass of this circuit, in my unit the square wave, even if asymmetrical, is a bit "faster".
Anyway, I dan't think that this could lead to a "terrible" sound.
Check your components' quality (surplus caps?!). Or more simple, this could not be "your" sound, but believe me, this circuit topology hardly leads to such an "hard" sound...
Marcello
Post Scriptum: the output load is made by a 33R non-inductive resistor
Attachments
Hi Marcello,
thanks for your response.
May be you´re right. The input copling cap is only a "cheap" standard type. Is it required to spend 15 or more Euros for one 5µF cap? What type is surplus and were to get them? On the output side i´ve used Panasonic FC types.
I´ve no high qualitiy caps available, so I will order some. What would you recommend?
Best regards
Bernd
thanks for your response.
May be you´re right. The input copling cap is only a "cheap" standard type. Is it required to spend 15 or more Euros for one 5µF cap? What type is surplus and were to get them? On the output side i´ve used Panasonic FC types.
I´ve no high qualitiy caps available, so I will order some. What would you recommend?
Best regards
Bernd
Hi tortello, hi all,
First of all thanks to you and to M. Pass.
I'm very interested in making this amplifier to feed my Senheiser HD-600. It appears that some members (CapacitorBill, stefanobilliani,...) are using this headphone too. If possible, I would like to know how I should modify the original amplifier in order to use this high impedance headphone (change in the part list, etc...)?
I would like to order all the part in the same shop... but the one I'm thinking of do not sell IRF610 So here is my second question: what else can I use, is there something better than the IRF610 for this purpose?
Thank you in advance for your help!
First of all thanks to you and to M. Pass.
I'm very interested in making this amplifier to feed my Senheiser HD-600. It appears that some members (CapacitorBill, stefanobilliani,...) are using this headphone too. If possible, I would like to know how I should modify the original amplifier in order to use this high impedance headphone (change in the part list, etc...)?
I would like to order all the part in the same shop... but the one I'm thinking of do not sell IRF610
So here is my second question: what else can I use, is there something better than the IRF610 for this purpose?Thank you in advance for your help!
Unless you want to listen at extra-super-ungodly high listening levels, you shouldn't need to make any changes at all. By my quick calc, it should drive your HD-600's to well over 100dB (i.e. loud enough to damage your hearing).
As to your question on the fet's, maybe some of the other members can make some suggestions. As a start I'd suggest dowloadig the IRF610 datasheet and look for fets that have similar characteristics, in particular the transconductance, and capacitance values.
Cheers, Terry
Thanks for your reply metalman.
In point of fact I was not really thinking of the power/volume thing. I'm mostly wondering if some changes have to be done to adapt the amplifier to a different charge. If not I can follow tortello's original part list. But if things can be adapted I and probably other people would be glad to know how
Have a nice day
In point of fact I was not really thinking of the power/volume thing. I'm mostly wondering if some changes have to be done to adapt the amplifier to a different charge. If not I can follow tortello's original part list. But if things can be adapted I and probably other people would be glad to know how
Have a nice day
Hello r_jik45,
Terry is right!
Only if you wish to use this amp with high-Z, (very) low sensitivity headphones, then it would be advisable to increase the PS voltage, changing the nfb resistors values to center the bias point. You can decrease the bias current too, since with higher loads the modulated current will be less than Grados. So you can obtain a low dissipation figure anyway.
The hexfet substitution is a bit tricky, since the (total) input capacitance can limit seriously the high frquency response of the amplifier.
Good work!
Marcello
Terry is right!
Only if you wish to use this amp with high-Z, (very) low sensitivity headphones, then it would be advisable to increase the PS voltage, changing the nfb resistors values to center the bias point. You can decrease the bias current too, since with higher loads the modulated current will be less than Grados. So you can obtain a low dissipation figure anyway.
The hexfet substitution is a bit tricky, since the (total) input capacitance can limit seriously the high frquency response of the amplifier.
Good work!
Marcello
Hello
Full details of the project can be found here
http://headwize.com/projects/showfile.php?file=pellerano_prj.htm
Mark
Full details of the project can be found here
http://headwize.com/projects/showfile.php?file=pellerano_prj.htm
Mark