Hi guys,
I belive this is my first post at tube section, 'cose I've been busy with sand, sorry
. Recently I manage to buy 16 Ei PL509 along with Magnoval sockets wery cheaply. I also have a Sennheizer HD600 (300 Ohm) and Philips SBC-HP890 (32 Ohm) headphones but not a tube headamp capable to drive them both. So I am in the mood for something really special, like DC coupled balance OTL headamp based on PL509. I found only one schematic that satisfied my needs, that is schematic by dr. Kevin Gilmore (of head-fi.org fame) OTL based on 6C33C-B. Original sch have some mosfets which I can't get, so I changed that part of circuit for IRF9231 and IRF610 along with output tubes, some resistors and pots, added snoobers network and inductive decoupling at output. I think that servo opamps is a must in amplifier like this, but I have not try to solve that part yet. Guess that each output (+ & -) will need it's own servo opamp to control relative DC offset (+ output agaist ground and - output against ground) & one more to control absolute DC offset (+ output against - output). Let me tell you that I am NOT an EE nor have long experiece with SS and tubes, so ANY help and advise is wellcome.
And yes, I am willing to split ground in my headphones if this Godzilla works🙂
Best, a
I belive this is my first post at tube section, 'cose I've been busy with sand, sorry
. Recently I manage to buy 16 Ei PL509 along with Magnoval sockets wery cheaply. I also have a Sennheizer HD600 (300 Ohm) and Philips SBC-HP890 (32 Ohm) headphones but not a tube headamp capable to drive them both. So I am in the mood for something really special, like DC coupled balance OTL headamp based on PL509. I found only one schematic that satisfied my needs, that is schematic by dr. Kevin Gilmore (of head-fi.org fame) OTL based on 6C33C-B. Original sch have some mosfets which I can't get, so I changed that part of circuit for IRF9231 and IRF610 along with output tubes, some resistors and pots, added snoobers network and inductive decoupling at output. I think that servo opamps is a must in amplifier like this, but I have not try to solve that part yet. Guess that each output (+ & -) will need it's own servo opamp to control relative DC offset (+ output agaist ground and - output against ground) & one more to control absolute DC offset (+ output against - output). Let me tell you that I am NOT an EE nor have long experiece with SS and tubes, so ANY help and advise is wellcome.And yes, I am willing to split ground in my headphones if this Godzilla works🙂
Best, a
Wow. I wanna see pictures. Now replace the current
sources with tubes and you have a MIG2.
I'll analyze all the currents and voltages and see if i can't
come up with a few minor changes. It should be stable enough
not to need a servo...
sources with tubes and you have a MIG2.
I'll analyze all the currents and voltages and see if i can't
come up with a few minor changes. It should be stable enough
not to need a servo...
Hi Kevin,
Thank you for replay, I really need all the help I can get from gurues around here.
Now, as suggested, I managed somehow to swop BJT current source for tube one, but I have to learn that part first from Bruce Rozenblit book😀. How does it looks? At this point I should point out that, if this Headzilla ever come to life, I intend to bild poweramp base on same (more or less) sch. Therefore, I have to spare some of the PL509 for that duty, and for that reason I would rather use SS (M-fet or BJT) current source no matter how tube CCS looks good on spice or actual sound/measurement of a real thing.
That appart, I think I have trouble with Vbe mutliplier (Q3/Q4)and M-fet differential amp (M2/M3). Should I swop BJT Vbe multipier for M-fet Vgs mutipier (something like ZVN3306) and keep the 2 x IRF610 diff. amp with some resistors/pots values changes?
Any way, here is KGB v1.1 with tube current source...suggestions, comments?
Regards, a
Thank you for replay, I really need all the help I can get from gurues around here.
Now, as suggested, I managed somehow to swop BJT current source for tube one, but I have to learn that part first from Bruce Rozenblit book😀. How does it looks? At this point I should point out that, if this Headzilla ever come to life, I intend to bild poweramp base on same (more or less) sch. Therefore, I have to spare some of the PL509 for that duty, and for that reason I would rather use SS (M-fet or BJT) current source no matter how tube CCS looks good on spice or actual sound/measurement of a real thing.
That appart, I think I have trouble with Vbe mutliplier (Q3/Q4)and M-fet differential amp (M2/M3). Should I swop BJT Vbe multipier for M-fet Vgs mutipier (something like ZVN3306) and keep the 2 x IRF610 diff. amp with some resistors/pots values changes?
Any way, here is KGB v1.1 with tube current source...suggestions, comments?
Regards, a
Hi aparatusonitus,
I wonder what the aim of this exercise might be - just to show that such a Rube Goldberg monstrosity could be done somehow?
BTW, the EL509/PL509 is a horrible tube to start with, even in trioded mode. See this link for the plate curves., moreover, it is really hard to keep from drifting.
A decent OTL headphone amp probably could be done with about 5% of the parts count you are at already in your schematic, even if you decide to go hybrid, which usually tends to up the parts count considerably, compared to pure tube tech.
Just my 2 Euro-cents.
Tom
I wonder what the aim of this exercise might be - just to show that such a Rube Goldberg monstrosity could be done somehow?
BTW, the EL509/PL509 is a horrible tube to start with, even in trioded mode. See this link for the plate curves., moreover, it is really hard to keep from drifting.
A decent OTL headphone amp probably could be done with about 5% of the parts count you are at already in your schematic, even if you decide to go hybrid, which usually tends to up the parts count considerably, compared to pure tube tech.
Just my 2 Euro-cents.
Tom
Hi,
First I must warn you that I am not a friend of hybrid designs so I can't add so much help with your chosen circuit but I am intrigued why you want to build such a complicated design so I would be intrested to hear your answers to some questions I have.
Why do you use such big tubes as EL 509 to drive headphones?
What is your basic goal? is it to build a headphone amp as such or is to build a hybrid amp? How much output power do you aim for?
I built a much simpler amp that can be seen here http://www.tubetvr.com/headphoneamp.html it gives about 600mV out when loaded with 30 ohm load which is about 12mW and more than enough for most headphones.
Regards hans
First I must warn you that I am not a friend of hybrid designs so I can't add so much help with your chosen circuit but I am intrigued why you want to build such a complicated design so I would be intrested to hear your answers to some questions I have.
Why do you use such big tubes as EL 509 to drive headphones?
What is your basic goal? is it to build a headphone amp as such or is to build a hybrid amp? How much output power do you aim for?
I built a much simpler amp that can be seen here http://www.tubetvr.com/headphoneamp.html it gives about 600mV out when loaded with 30 ohm load which is about 12mW and more than enough for most headphones.
Regards hans
Hi Tubes4e4 & Hans,
Thanks for replay, I really need some feedback from more experience builders around.
I will use PL509 (or PL504, if I can get them) 'couse I allready have 16 pcs of them, and the very same topology will be eventually used for power amp. I will try to build a headamp first to evaluate topology soundwise, it's chiper that way.
Why hybrid? Becouse it's DC coupled balance amp, from input to output, and that is what I like (although one might see a servo opamps as capacitor), and except topology from Kaneda (also hybrid, totem-pole SE output, I think) is the only one I have found out so far.
Headamp should be capable to drive 32 and 300 Ohms headphones simultaneously, so something like 2W in class A
Thanks for replay, I really need some feedback from more experience builders around.
I will use PL509 (or PL504, if I can get them) 'couse I allready have 16 pcs of them, and the very same topology will be eventually used for power amp. I will try to build a headamp first to evaluate topology soundwise, it's chiper that way.
Why hybrid? Becouse it's DC coupled balance amp, from input to output, and that is what I like (although one might see a servo opamps as capacitor), and except topology from Kaneda (also hybrid, totem-pole SE output, I think) is the only one I have found out so far.
Headamp should be capable to drive 32 and 300 Ohms headphones simultaneously, so something like 2W in class A
You don't need to build a hybrid amp to make it DC coupled and balanced if that is what you want, It is more of a challenge to do this using only tubes, it has been done many times before but you need to look up how they built DC coupled instrumentation amps with tubes.
2W will make your ears fall off!, 10mW is more than enough to seriously risk damage to your hearing with most headphones, 2W would make a good power amplifier for driving high efficiency speakers even in large rooms. My headphone amp can give the same current output regardless of if the load is 30 ohm or 300 ohm so the output power at 300ohm is 10 times higher or ~120mW, please measure at what level you are playing when you think it is too high, you will be surprised how low it is.
Regards Hans
Hi Hans,
I am aware of the power needed to drive heaphones to ear spliting level, I can only confirm yours findings, but I forget to note that Headzilla will be eventualy used as a speaker/tweeter amp also in biamp system just to evaluate concept soundwise before I go for OTLzilla 😀 (speakers are Castle Harlech, benign load, stays over 8 Ohms most of time, no nasty reactance, fairly efficient, quarter-wave + bas reflex technology).
DC coupled instrumentation amps with tubes, newer heard for such, any link before I hit the Google?
Best, a
P.S How about all valve (PCC88) DC coupled (from input to output) balance headamp with Circlotron topology, is it posible?
I am aware of the power needed to drive heaphones to ear spliting level, I can only confirm yours findings, but I forget to note that Headzilla will be eventualy used as a speaker/tweeter amp also in biamp system just to evaluate concept soundwise before I go for OTLzilla 😀 (speakers are Castle Harlech, benign load, stays over 8 Ohms most of time, no nasty reactance, fairly efficient, quarter-wave + bas reflex technology).
DC coupled instrumentation amps with tubes, newer heard for such, any link before I hit the Google?
Best, a
P.S How about all valve (PCC88) DC coupled (from input to output) balance headamp with Circlotron topology, is it posible?
I don't know about internet sources but there are of course old tube text books, as an example look up "vacuum tube amplifiers" by Valley & Wallman chapter 11 where the principles of DC coupled tube amplifiers are described, there are also examples of complete circuits.
Should be quite possible, I remember that there where a participant on the forum earlier that had built a DC coupled OTL and I think that was a circlotron variant. My first real OTL was a DC coupled Futterman variant but I never developed it further than a lab prototype.
Although a DC coupled balanced OTL is possible to design maybe you should take a step back and think about what your requirements are? What are the advantages that you think you will get with an all DC coupled design? will it give any noticable difference compared with a simpler design where you use a few coupling capacitors?
The same for why you want to use an all balanced design, what are you trying to achieve and will it give any noticeable difference?
Regards Hans
Hi Hans,
I know I could get a very good sound from an AC coupled amp, but whenever I do that, sound is dependent of copling caps quality and ability to get one here that sounds really good, is variable that I would rather avoid by DC coupling.
Well, I have very good sounding balance cd player(I meen really balance, like 8 x DACs in dual differential mode), working on a balanced nonos TDA1541 DAC, and just to have a Balance Line Stage (aka Bride of Son of Zen) from Nelson Pass witch could drive HD600 at preety good volume and excelent sound with balaced output. Hope to get even more of that from KGB. Moreover, I want to buid entyre sistem balanced, 'couse I like the sound coming from it more then SE, that is.
Best, a
tubetvr said:
I know I could get a very good sound from an AC coupled amp, but whenever I do that, sound is dependent of copling caps quality and ability to get one here that sounds really good, is variable that I would rather avoid by DC coupling.
tubetvr said:
Well, I have very good sounding balance cd player(I meen really balance, like 8 x DACs in dual differential mode), working on a balanced nonos TDA1541 DAC, and just to have a Balance Line Stage (aka Bride of Son of Zen) from Nelson Pass witch could drive HD600 at preety good volume and excelent sound with balaced output. Hope to get even more of that from KGB. Moreover, I want to buid entyre sistem balanced, 'couse I like the sound coming from it more then SE, that is.
Best, a
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