I currently have a portable headphone amp with the OPA2227P chip and a two-9V battery power supply. It would work great for travelling... but I am a home listener more than anything. So I want something better, but not too expensive as I am limited on funds. The tube amp below seems as though it could be quite affordable, and I have always liked tubes, and have been wanting to build a tube amp for a while now. Some of you may remember the idea to make an HF-87... it just got too expensive, unfortunately. I could have bought a rebuilt one in perfect chape for the same price. This amp will power Sennheiser HD580s in case it is necessary
I have some questions, about this amp, not a lot on how to build- I can get that part, but about safety. I am not one to enjoy strapping something to my head that could have more than 9V running through it- for my safety and that of the headphones. Are OTL headphone amps safe? I really don't wanna blow my $200 cans. Can this amp damage anything- the turning on and off, etc. Will it ever harm my phones?
The only real question I have about the amp diagram is the heater supply. It says use a shielded cable- can anyone give me an example of that type this is and what I should use? And also on the heater supply, am I reading this right when I am thinking the power is attached to pin 4 on both 6CG7's and again power attached to pins 4 and 5 on the 12AU7's and then pin 5 on the 6CG7's and pin 9 on the 12AU7's is going to ground? Or is that supposed to read that power goes to all pins (4,5,9) and then from 9 out to ground?
Also, just thought of a question... the headphone output jack/RCA input jacks have a ground. Do I connect this ground to the ground of the amp? Won't that give me some voltage across my ground that could damage my cans?
Thanks
I have some questions, about this amp, not a lot on how to build- I can get that part, but about safety. I am not one to enjoy strapping something to my head that could have more than 9V running through it- for my safety and that of the headphones. Are OTL headphone amps safe? I really don't wanna blow my $200 cans. Can this amp damage anything- the turning on and off, etc. Will it ever harm my phones?
The only real question I have about the amp diagram is the heater supply. It says use a shielded cable- can anyone give me an example of that type this is and what I should use? And also on the heater supply, am I reading this right when I am thinking the power is attached to pin 4 on both 6CG7's and again power attached to pins 4 and 5 on the 12AU7's and then pin 5 on the 6CG7's and pin 9 on the 12AU7's is going to ground? Or is that supposed to read that power goes to all pins (4,5,9) and then from 9 out to ground?
Also, just thought of a question... the headphone output jack/RCA input jacks have a ground. Do I connect this ground to the ground of the amp? Won't that give me some voltage across my ground that could damage my cans?
Thanks
Yes, please do!
It is almost impossible to desrcibe a circuit, just with words.
Makes you get many more answers and better discussion,
if you give as many and easily understood facts, as possible.
This is something many more should think about.
/halo - and all wants this forum to work as good as it can
for all to benefit
It is always recommended with some diagram.dhaen said:Please post a diagram or link.
It is almost impossible to desrcibe a circuit, just with words.
Makes you get many more answers and better discussion,
if you give as many and easily understood facts, as possible.
This is something many more should think about.
/halo - and all wants this forum to work as good as it can
for all to benefit
As I hit the submit button, I hat this odd feeling I was forgetting something... but it just never dawned on me. 
Anyway, here it is:
and the power supply:
That should help considerably.
Anyway, here it is:
An externally hosted image should be here but it was not working when we last tested it.
and the power supply:
An externally hosted image should be here but it was not working when we last tested it.
That should help considerably.
trespasser_guy,
As long as it constructed properly, there should be no safety issue with this OTL design, for you, or for your cans.
IMO the screening of the heater wiring is unnecessary, providing you keep it away from signal carrying wires and components.
I don't understand your earth/ground question.
Cheers,
Halojoy,
Sorry. But don't you think you were stating the obvious?
He had not ommited the diagram on purpose. It was obviously a mistake.
BTW Ranking stopped some time ago.
As long as it constructed properly, there should be no safety issue with this OTL design, for you, or for your cans.
IMO the screening of the heater wiring is unnecessary, providing you keep it away from signal carrying wires and components.
I don't understand your earth/ground question.
Cheers,
Halojoy,
Sorry. But don't you think you were stating the obvious?
He had not ommited the diagram on purpose. It was obviously a mistake.
BTW Ranking stopped some time ago.
Some more thoughts
trespasser_guy,
Looking again at the heater circuit, I would predict less hum (and noise) if you just used AC through twisted wires "daisy chained" from the heater winding on the transformer. If there is no centre tap, you can use 2 resistors to ground.
Indirectly heated valves were designed with AC in mind. IMO there is no reason for DC except in mic and phono inputs.
There'd be a bit less heat too.
Cheers,
Craig,
Thanks, but it's got a long way to go.
trespasser_guy,
Looking again at the heater circuit, I would predict less hum (and noise) if you just used AC through twisted wires "daisy chained" from the heater winding on the transformer. If there is no centre tap, you can use 2 resistors to ground.
Indirectly heated valves were designed with AC in mind. IMO there is no reason for DC except in mic and phono inputs.
There'd be a bit less heat too.
Cheers,
Craig,
Thanks, but it's got a long way to go.
Thanks so far.
Ryder, I found the schematic on HeadWize- the first one under the tubes section by Kurt Strain. Here
So, the power supply could use work? What should be done? Change the heater supply to AC? I am guessing that would be done by removing the diode bridge, but what else would be done? And I am still uncertain how to wire the heaters... For the 6CG7's it shows pin 4 on top and 5 on the bottom next to the ground. Does this mean that pin 4 gets the power and then pin 5 is just grounded? Then the same with the 12AU7's, except pins 4+5 are powered and 9 is grounded?
Also, when I run the ground from my input/output jacks, if they connect to the amp ground, won't they have some voltage running across them?
fdegrove, this mute switch I am guessing is a simple switch like a DPDT that is just an on off at the output section, correct? Where in the diagram is it located exactly?
Ryder, I found the schematic on HeadWize- the first one under the tubes section by Kurt Strain. Here
So, the power supply could use work? What should be done? Change the heater supply to AC? I am guessing that would be done by removing the diode bridge, but what else would be done? And I am still uncertain how to wire the heaters... For the 6CG7's it shows pin 4 on top and 5 on the bottom next to the ground. Does this mean that pin 4 gets the power and then pin 5 is just grounded? Then the same with the 12AU7's, except pins 4+5 are powered and 9 is grounded?
Also, when I run the ground from my input/output jacks, if they connect to the amp ground, won't they have some voltage running across them?
fdegrove, this mute switch I am guessing is a simple switch like a DPDT that is just an on off at the output section, correct? Where in the diagram is it located exactly?
MUTE.
Hi,
Very well, it is to be positioned behind to output cap.
Re:heaters...I need to check pinouts for the tubes.
Just a guess, if pins 4+5 are connected on the the 12AU7 you run them at 6.3 V with twice the current.
I'll check and get back on this.
The SRPP circuits are rather finicky about the PSU,go either regulated or brute force.
Cheers,
Hi,
Very well, it is to be positioned behind to output cap.
Re:heaters...I need to check pinouts for the tubes.
Just a guess, if pins 4+5 are connected on the the 12AU7 you run them at 6.3 V with twice the current.
I'll check and get back on this.
The SRPP circuits are rather finicky about the PSU,go either regulated or brute force.
Cheers,
So is the switch behind the output cap and the resistor going to ground? Or between?
Will this amp have a hard time driving a 300-ohm load? I just read on the page about it that it didn't have as detailed of bass... this worries me.
There is also this amp that most say will drive the 300-ohm 580s better. Is it a better design? I was thinking about the optimized one with the feedback added, and then the second power supply by Rudy van Stratum if I went this route.
What do you think?
Will this amp have a hard time driving a 300-ohm load? I just read on the page about it that it didn't have as detailed of bass... this worries me.
There is also this amp that most say will drive the 300-ohm 580s better. Is it a better design? I was thinking about the optimized one with the feedback added, and then the second power supply by Rudy van Stratum if I went this route.
What do you think?
HEADPHONE AMP
Hi,
As long as it is behind the coupling cap it doesn't matter where you put it.
The second circuit based on the Morgan Jones seems to be the better one.
I've used White cathode folowers for years and IME these are about the best buffers I can think of.
They will drive very low impedances,can swing a considerable amount of volts as well and don't veil the sound.
Cheers,
Hi,
As long as it is behind the coupling cap it doesn't matter where you put it.
The second circuit based on the Morgan Jones seems to be the better one.
I've used White cathode folowers for years and IME these are about the best buffers I can think of.
They will drive very low impedances,can swing a considerable amount of volts as well and don't veil the sound.
Cheers,
Amps through headphones...
The second one is elegant, in that the power supply seems to use "available" components. And yes, I'd agree that it's output Z will probably be lower.
Why is the output coupling capacitor so large; 470uF. Surely no headphones are that low impedance? IMO there is also a chance that high voltage will appear on the headphone jack during warmup while that enormous cap charges up through 22k.
Cheers,
The second one is elegant, in that the power supply seems to use "available" components. And yes, I'd agree that it's output Z will probably be lower.
Why is the output coupling capacitor so large; 470uF. Surely no headphones are that low impedance? IMO there is also a chance that high voltage will appear on the headphone jack during warmup while that enormous cap charges up through 22k.
Cheers,
DC.
Hi,
That's why I suggest to add a mute switch.
While warming up (at least for a minute) the switch should be engaged to prevent any DC from developping at the output.
My guess for the value of that cap is that it is a standard value and as such readily available?
It sure is large enough!
Cheers,
Hi,
That's why I suggest to add a mute switch.
While warming up (at least for a minute) the switch should be engaged to prevent any DC from developping at the output.
My guess for the value of that cap is that it is a standard value and as such readily available?
It sure is large enough!
Cheers,
I don't understand the use of electrolytics in the second circuit... I thought film types were superior... if I can find some of the values used in film types would they be good upgrades? Or do I need to stay electrolyitic since there are polarity markers?
And the ehadphones I am going to drive are 300-ohms, and they havea peak to almost 600-ohms at the 100-ish Hz region.
Would the second one drive the 300-ohm load better?
Which power supply would you use?
And the ehadphones I am going to drive are 300-ohms, and they havea peak to almost 600-ohms at the 100-ish Hz region.
Would the second one drive the 300-ohm load better?
Which power supply would you use?
I just found another power supply here that is tube rectified and puts out 225V, which is closer to the required 220V than the 230V put out by the power supply I liked best. Would it work? Which power supply would you go with?
EDIT: the power supply is from VT52.com
EDIT again... of course there is nothing for the filament supplies... so hmm...
EDIT: the power supply is from VT52.com
EDIT again... of course there is nothing for the filament supplies... so hmm...
You should of course use FILMS if you find Values.
Even polyester are better than ANY electrolyte.
Whatever exoticly colored names they call them.
I know you know, tresspasser_guy.
So trust yourself, your own judgement.
No labels can changes the facts.
/halo - a man that tries to find out the facts
Even polyester are better than ANY electrolyte.
Whatever exoticly colored names they call them.
I know you know, tresspasser_guy.
So trust yourself, your own judgement.
No labels can changes the facts.
/halo - a man that tries to find out the facts
trespasser_guy,
Film caps are often better than electrolytics, but large values are difficult to source, expensive, and physically large.
IMO the second one would drive better.
The power supply choice is interesting. The first power supply was conventional. The second seemed to be made from bits the guy had in his component box.
Your best choice depends on your budget, and the availability of a suitable mains transformer.
Cheers,
Film caps are often better than electrolytics, but large values are difficult to source, expensive, and physically large.
IMO the second one would drive better.
The power supply choice is interesting. The first power supply was conventional. The second seemed to be made from bits the guy had in his component box.
Your best choice depends on your budget, and the availability of a suitable mains transformer.
Cheers,
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