THE MIG TUBE.
Hi,
Arg_,
Glad to help any time.🙂
If you're confortable with the amp you built may I suggest to try it out on (a friends' maybe?) more efficient set of speakers?
It would be great for us to get feedback on the overall sound of the circuit and see how to tubes behave in the long run.
I also hope Mr.Ciuffoli continues to develop his OTL,perhaps using a different driver/splitter so more tubes can be driven comfortably.
For the moment I'm looking into OTLs using the 6C45 and
6C19 tubes.
Cheers,😉
Hi,
Arg_,
Glad to help any time.🙂
If you're confortable with the amp you built may I suggest to try it out on (a friends' maybe?) more efficient set of speakers?
It would be great for us to get feedback on the overall sound of the circuit and see how to tubes behave in the long run.
I also hope Mr.Ciuffoli continues to develop his OTL,perhaps using a different driver/splitter so more tubes can be driven comfortably.
For the moment I'm looking into OTLs using the 6C45 and
6C19 tubes.
Cheers,😉
:Frank
It is a month now I am playing with the amp and have not had any signs of instability. I am not sure what happens should an output tube shorts but I trust (hope?) 🙂 the +/-B rail fuse will trip first.
However since the tubes operate at relaxed conditions (~200mA), I don't think this is very likely to happen.
I ran some measurements and the square wave at 1KHz is perfect, while the 10KHz bellow does not show any signs of oscillation (sorry for the bad pic, even the camera lens is included)
The freq. response extents well above 200KHz, using 13db of NFB.
As to the sound, I am so excited with its sonics that I am tempted to build another more efficient pair of speakers to fully enjoy it - after all we all need incentives, dont we? 😉
Re 6C45, in case you haven't spot it, Stefano Perugini has a wealth of information in his site http://digilander.libero.it/paeng/pae.htm
It's kind of irony, he has used it in every possible way except for an OTL amp
(click devices\one tube)
Cheers
Argiris
It is a month now I am playing with the amp and have not had any signs of instability. I am not sure what happens should an output tube shorts but I trust (hope?) 🙂 the +/-B rail fuse will trip first.
However since the tubes operate at relaxed conditions (~200mA), I don't think this is very likely to happen.
I ran some measurements and the square wave at 1KHz is perfect, while the 10KHz bellow does not show any signs of oscillation (sorry for the bad pic, even the camera lens is included)
An externally hosted image should be here but it was not working when we last tested it.
The freq. response extents well above 200KHz, using 13db of NFB.
As to the sound, I am so excited with its sonics that I am tempted to build another more efficient pair of speakers to fully enjoy it - after all we all need incentives, dont we? 😉
Re 6C45, in case you haven't spot it, Stefano Perugini has a wealth of information in his site http://digilander.libero.it/paeng/pae.htm
It's kind of irony, he has used it in every possible way except for an OTL amp
(click devices\one tube)Cheers
Argiris
OTL
Hi,
Having speakers with a 96 dB effeciency would be ideal for this IMO.
BTW,another interesting tube for OTL builders would be the 6C41 as used by our fellow tube lover Bas Horneman in an OPT coupled amp.
I would need more detailed data but it looks a good candidate for this application and also uses the septar socket.
I'm looking forward to see more OTLs using the ECC99 or 6C45 as drivers.
Cheers,😉
Hi,
Having speakers with a 96 dB effeciency would be ideal for this IMO.
BTW,another interesting tube for OTL builders would be the 6C41 as used by our fellow tube lover Bas Horneman in an OPT coupled amp.
I would need more detailed data but it looks a good candidate for this application and also uses the septar socket.
I'm looking forward to see more OTLs using the ECC99 or 6C45 as drivers.
Cheers,😉
Ah...
Hi Arg,
Just upload it without doing a preview,if you do a preview you'll need to attach the pic again.
Give it a try,😉
Hi Arg,
Just upload it without doing a preview,if you do a preview you'll need to attach the pic again.
Give it a try,😉
OTL
Hi,
Now try that with an OPT coupled amp...😎
Arg,
If you could try your amps on a higher effeciency speaker first to give you an idea on residual noise levels that would be great.
Did you implement the fourth bias scheme as I suggested?
If not, I suppose you connected that dreaded C connection only to one channel?
Cheers,😉
Hi,
Now try that with an OPT coupled amp...😎
Arg,
If you could try your amps on a higher effeciency speaker first to give you an idea on residual noise levels that would be great.
Did you implement the fourth bias scheme as I suggested?
If not, I suppose you connected that dreaded C connection only to one channel?
Cheers,😉
Hmmm.
I think your OTL amp has a better output than my Eico 377 signal generator.
Tim getz fixxin'....
I think your OTL amp has a better output than my Eico 377 signal generator.
Tim getz fixxin'....
Getting rid of the iron is a great thing 😉
Yes, this is the scheme I'm using now. It has made the bias adjustment somewhat easier but still the channels share the same floating ground so they can not be independent. A monoblock or dual-mono construction would be great but would drive the cost up.
I have noticed no signs of crosstalk between the channels.
btw I never tried connecting point C in one channel only so I am not sure about this scheme.
Frank could you say a few words about the OTL you're using?
OTL REVISITED.
Hi,
Sure,it's a design that is similar to the one presented by Bruce Rozenblitt in Glass Audio in 1992.
You can find it at bonavolta.ch under OTL.
The one I use dates from 1987.
The main differences are that mine are monoblocks using 10 // 6080 per channel for 120W into an 8 Ohm load.
B+ and - run from a heavily filtered rail with 2*4700 mF/250VDC caps per polarity.
Bias is set from two independent supplies and can be monitored by the push of a button through an Ampmeter on the frontpanel.
Drive to the output tubes comes from a pair of 12BH7A mounted as CFs, one per phase.
Those are fed from an ECF802 phase splitter with unequal phase to compensate for the difference in gain of the upper and lower banks of output tubes.
This ECF802 gets its' signal from a trioded EF86.
The powerxformer is an impressive custommade 1.5KV and accounts for 80% of the 38 Kgs these monoblocks clock on the scale.
NFB is taken straight from the output to the split cathode R of the EF86 and is 12dB.
My speakers are British SD Acoustics SD3 with 92dB efficiency.
Output impedance after NFB is 0.14 Ohm.
THD < 0.1% typical.
Input sensitivity for rated output is 1.3V.
Input impedance is 100K.
Cheers,😉
Hi,
Sure,it's a design that is similar to the one presented by Bruce Rozenblitt in Glass Audio in 1992.
You can find it at bonavolta.ch under OTL.
The one I use dates from 1987.
The main differences are that mine are monoblocks using 10 // 6080 per channel for 120W into an 8 Ohm load.
B+ and - run from a heavily filtered rail with 2*4700 mF/250VDC caps per polarity.
Bias is set from two independent supplies and can be monitored by the push of a button through an Ampmeter on the frontpanel.
Drive to the output tubes comes from a pair of 12BH7A mounted as CFs, one per phase.
Those are fed from an ECF802 phase splitter with unequal phase to compensate for the difference in gain of the upper and lower banks of output tubes.
This ECF802 gets its' signal from a trioded EF86.
The powerxformer is an impressive custommade 1.5KV and accounts for 80% of the 38 Kgs these monoblocks clock on the scale.
NFB is taken straight from the output to the split cathode R of the EF86 and is 12dB.
My speakers are British SD Acoustics SD3 with 92dB efficiency.
Output impedance after NFB is 0.14 Ohm.
THD < 0.1% typical.
Input sensitivity for rated output is 1.3V.
Input impedance is 100K.
Cheers,😉
Hello,
About the circuit diagram that is posted earlier, is the E182CC
used in parallel ?
On the diagram the grid is unconnected.
Also, 0,1 R - is this correct value ?
In previous versions Mr.Ciuffoli used 1 R.
Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip
About the circuit diagram that is posted earlier, is the E182CC
used in parallel ?
On the diagram the grid is unconnected.
Also, 0,1 R - is this correct value ?
In previous versions Mr.Ciuffoli used 1 R.
Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip
Attachments
:Kristijan
The E182CC is indeed connected in parallel, grid included. There is a tiny little line if you look closer 😉
Yes, it doesn't make any difference to the circuit, it's just there to facilitate current measurement
:Frank
Wow, some beasts you have there !!! It will take some time for me to digest the specs...
I can sure understand why you
OTLs
Cheers
Argiris
The E182CC is indeed connected in parallel, grid included. There is a tiny little line if you look closer 😉
Yes, it doesn't make any difference to the circuit, it's just there to facilitate current measurement
:Frank
Wow, some beasts you have there !!! It will take some time for me to digest the specs...
I can sure understand why you
OTLsCheers
Argiris
.1R
Hi,
For those of you concerned abourt the 0.1 R resistors in the circuit,they are there for measuring current only.
As has been pointed out Mr.Ciuffoli used higher values in previous designs and changed this to lower the ouyput Z of the amps.
This has only a marginal effect though but if you're concerned about this, a neat trick is to bypass them using a switching arrangement.
This amounts to 1 resistor that is switched around one tube at the time in a make before break manner and is out of the circuit when not measuring standing current.
With some tubes such as the USA made 6AS7 the plate resistors serve another purpose as well.
For info:
6AS7G
Cheers,😉
Hi,
For those of you concerned abourt the 0.1 R resistors in the circuit,they are there for measuring current only.
As has been pointed out Mr.Ciuffoli used higher values in previous designs and changed this to lower the ouyput Z of the amps.
This has only a marginal effect though but if you're concerned about this, a neat trick is to bypass them using a switching arrangement.
This amounts to 1 resistor that is switched around one tube at the time in a make before break manner and is out of the circuit when not measuring standing current.
With some tubes such as the USA made 6AS7 the plate resistors serve another purpose as well.
For info:
6AS7G
Cheers,😉
Of course, we all know that already, and also know that resistors are best placed in the cathode for current-spreading.......
Tim
Tim
KNOWLEDGE
Hi,
We,OTOH,have no idea what you know and don't know.
Pluralis Majestatis...jeeez,talk about an ego.
Cheers,😉
Hi,
We,OTOH,have no idea what you know and don't know.
Pluralis Majestatis...jeeez,talk about an ego.
Cheers,😉
Huh? I assumed you did!
The effect is (mu+1) times greater having resistors in cathode rather than plate.
Tim (ego? I'm 16, kinda DUH 😛 I try to help it, but inevitably it'll show)
The effect is (mu+1) times greater having resistors in cathode rather than plate.
Tim (ego? I'm 16, kinda DUH 😛 I try to help it, but inevitably it'll show)
16?
Hi,
Tim,if I didn't know what I point out how could I have pointed it out in the first place?
Keep in mind also we're talking regulator tubes with their particular oddities.
I posted it to help people too,but I fail to see how your reply has added anything positive to the topic at hand?
So,let's lower the testosterone level and forgive and forget.😎
Cheers,😉
Hi,
Tim,if I didn't know what I point out how could I have pointed it out in the first place?
Keep in mind also we're talking regulator tubes with their particular oddities.
I posted it to help people too,but I fail to see how your reply has added anything positive to the topic at hand?
So,let's lower the testosterone level and forgive and forget.😎
Cheers,😉
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