Hi all,
as a second project (being an absolute tubez beginner) I am planning on building the lilliput amp (E88CC and 6080 SE) that once was mentioned on this forum. It was fdegrove himself who put my nose on it.....
This should be a lovely project, and for starters I have redrawn the schematic to make it readable. I have also converted the psu to tube rectification and added a RC stage.
The only point that remains unclear to me is the choice of output transformer (...I know this question is being asked all the time...). The original schematic sez something like 1.4K (hardly readable), the Megahertz schematic says nothing at all about that! I was wondering to go a little bit higher (say 2.5K...lower power but also lower distortion?), also trannies with around 2.5K are readily available at a number of places....
So, what would be the right choice?
Any advice/recommendation is greatly appreciated!
Thnxs,
Oliver
as a second project (being an absolute tubez beginner) I am planning on building the lilliput amp (E88CC and 6080 SE) that once was mentioned on this forum. It was fdegrove himself who put my nose on it.....
This should be a lovely project, and for starters I have redrawn the schematic to make it readable. I have also converted the psu to tube rectification and added a RC stage.
The only point that remains unclear to me is the choice of output transformer (...I know this question is being asked all the time...). The original schematic sez something like 1.4K (hardly readable), the Megahertz schematic says nothing at all about that! I was wondering to go a little bit higher (say 2.5K...lower power but also lower distortion?), also trannies with around 2.5K are readily available at a number of places....
So, what would be the right choice?
Any advice/recommendation is greatly appreciated!
Thnxs,
Oliver
Attachments
Hi Oliver.
Not really critical.
I bet any load from 1K5 to 3K will work with this such lo Rp tube.
Anyway, don't expect more than 2 watts !
Oh, I feel the 800R in PSU is really too hi in value (and too lo in wattage).
80R seems more acceptable (typo ?), and why not one per channel ?
Regards, Yves.
Not really critical.
I bet any load from 1K5 to 3K will work with this such lo Rp tube.
Anyway, don't expect more than 2 watts !
Oh, I feel the 800R in PSU is really too hi in value (and too lo in wattage).
80R seems more acceptable (typo ?), and why not one per channel ?
Regards, Yves.
Hi,
The 800 ohm is correct, it drops the 300V of DC (after the EZ81) to 220V,when both channel drawing 100mA.The wattage is too low, should be 50W i think,.80 V voltage drop across it with 100mA will give 8Watts of heat from that resistor.rules of thumb, give 6-7 times extra for lower temperature.
I used 1K output trans for my own design(similar schematic) give me 2.8W at clipping.
The 800 ohm is correct, it drops the 300V of DC (after the EZ81) to 220V,when both channel drawing 100mA.The wattage is too low, should be 50W i think,.80 V voltage drop across it with 100mA will give 8Watts of heat from that resistor.rules of thumb, give 6-7 times extra for lower temperature.
I used 1K output trans for my own design(similar schematic) give me 2.8W at clipping.
I was thinking that too Yves 😀
I was pondering the loadlines of a 6080 the other day and see 1.33K is good for 200V Va in class-A 🙂
I was pondering the loadlines of a 6080 the other day and see 1.33K is good for 200V Va in class-A 🙂
re
Merci Yves, thanks Geek and bigbulb for your input.
I know this little amp won't make a lot of power, but since my open baffles are about 96dB efficient (old Telefunkens from '53) it should do.
I think I will talk to one of the local winders in Germany to have opt's made with the spec'd 1.4k. AE Europe also makes very nice opt's with c-core at a reasonable price and is basically just around the corner....
And btw...I will quickly change that psu resistor in my schematic to a higher wattage one....
Oliver
Merci Yves, thanks Geek and bigbulb for your input.
I know this little amp won't make a lot of power, but since my open baffles are about 96dB efficient (old Telefunkens from '53) it should do.
I think I will talk to one of the local winders in Germany to have opt's made with the spec'd 1.4k. AE Europe also makes very nice opt's with c-core at a reasonable price and is basically just around the corner....
And btw...I will quickly change that psu resistor in my schematic to a higher wattage one....
Oliver
Instead dropping the B++ with the 800 ohm resistor, why not just eliminate the 2uF cap and have the power supply choke-input?
By the way, these little two-stage, two-tube stereo SE amps using pass tube outputs DO sound lovely.
John
P.S. Is the AE transformer a standard item or is it wound to order?
psu
Modelling this in Duncan's psud results in B++ of 195V, plus you're loosing one cap for smoothing....
The AE transformer hasn't been wound yet and is not a standard item, but as far as I know the owner happily accepts custom orders.
Oliver
Modelling this in Duncan's psud results in B++ of 195V, plus you're loosing one cap for smoothing....
The AE transformer hasn't been wound yet and is not a standard item, but as far as I know the owner happily accepts custom orders.
Oliver
Hi,
1K4 it is.But...into a 6 Ohm load.
To answer your question once and for all, the Megahertz iron is extraordinary both in measurement and sonics: it's about the only OPT I ever heard that sounds like no OPT at all.
Coming from someone who's been religiously devoted to OTL amps for well over two decades that's very high praise indeed.
The 6 Ohm secondary is no problem as it will drive both 4 Ohm and 6 Ohm speakers without any problem.
I heard this amp on 8 Ohm Lowthers and was impressed: it was one of the few times I actually heard the music and not the Lowthers' notorious nasality for a change.
Of course you can use other iron with a slightly higher Zprim on 8 Ohm nominal speakers but why would you?
The Megahertz OPT will do better, the amp doesn't show any sign of distortion under normal listening conditions and the OPTs are pretty cheap on all counts...
You can't look at it that way: doing away with the input cap changes the PS filtering topology from cap input to choke input.
Choke input being the prefered one.
If you need to have a higher B+ use a hybrid FWB rectified B+ choke input filter type iso a FW tube rectified one.
That's what I'd recommend anyway: no need for fancy diodes as most people would have you believe, the two diodes can be as daft as a pair of 1N4007s, it won't make any difference except in your wallet.
Cheers, 😉
1K4 it is.But...into a 6 Ohm load.
To answer your question once and for all, the Megahertz iron is extraordinary both in measurement and sonics: it's about the only OPT I ever heard that sounds like no OPT at all.
Coming from someone who's been religiously devoted to OTL amps for well over two decades that's very high praise indeed.
The 6 Ohm secondary is no problem as it will drive both 4 Ohm and 6 Ohm speakers without any problem.
I heard this amp on 8 Ohm Lowthers and was impressed: it was one of the few times I actually heard the music and not the Lowthers' notorious nasality for a change.
Of course you can use other iron with a slightly higher Zprim on 8 Ohm nominal speakers but why would you?
The Megahertz OPT will do better, the amp doesn't show any sign of distortion under normal listening conditions and the OPTs are pretty cheap on all counts...
You can't look at it that way: doing away with the input cap changes the PS filtering topology from cap input to choke input.
Choke input being the prefered one.
If you need to have a higher B+ use a hybrid FWB rectified B+ choke input filter type iso a FW tube rectified one.
That's what I'd recommend anyway: no need for fancy diodes as most people would have you believe, the two diodes can be as daft as a pair of 1N4007s, it won't make any difference except in your wallet.
Cheers, 😉
Hi,
...which implies that the kit from audiokit.it still comes with those megahertz OPT's.....
My Telefunkens are 5 Ohm-ish, so that'll do.
regards,
Oliver
...which implies that the kit from audiokit.it still comes with those megahertz OPT's.....
My Telefunkens are 5 Ohm-ish, so that'll do.
regards,
Oliver
I am still waiting to order that amp (went broke) so if you finally go for it Stixx , send your impressions.
Cheers,
Cheers,
Hi everybody,
Found that thread by searching on 6AS7.
It appears that I can buy some 6AS7 Russian near equivalents (6N13S or 6H13C) for very little money locally and thought, that the Lilliput could be a fun project to build to drive some high efficient speakers.
But while it seems very simple and relatively cheap to build, I am wondering that if it needs an additional preamp to be builded, the above virtues kind of disappear?
Can anybody make a wild guess what is the Lillput's input sensitivity or better: does it need a preamp if feed from CD player?
cheers,
argo
Found that thread by searching on 6AS7.
It appears that I can buy some 6AS7 Russian near equivalents (6N13S or 6H13C) for very little money locally and thought, that the Lilliput could be a fun project to build to drive some high efficient speakers.
But while it seems very simple and relatively cheap to build, I am wondering that if it needs an additional preamp to be builded, the above virtues kind of disappear?
Can anybody make a wild guess what is the Lillput's input sensitivity or better: does it need a preamp if feed from CD player?
cheers,
argo
Found it, I must have been blind. 
http://www.audiokit.it/ITAENG/KitElettr/MEGA/Lilliput/Lilliput.htm
Output Power (A1Class) 2,5 W
Input Sensitivity 1V
argo
http://www.audiokit.it/ITAENG/KitElettr/MEGA/Lilliput/Lilliput.htm
Output Power (A1Class) 2,5 W
Input Sensitivity 1V
argo
...uhm,
which is the better schematic for lilliput?
In this schematic(by audiokit) R6(270R) is in series with R3(15k - 3W) for ecc88 V+.
In this schematic(by megahertz) 270R is for 6080 V+.
which is the better schematic for lilliput?
In this schematic(by audiokit) R6(270R) is in series with R3(15k - 3W) for ecc88 V+.
An externally hosted image should be here but it was not working when we last tested it.
In this schematic(by megahertz) 270R is for 6080 V+.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
BTW: The 6AS7 can be swapped with 6BX7 and 6BL7 tubes. The tubes are pin compatible. They have lower power capabilities, but sound very good. Since the tubes have higher µ than the 6AS7 the idle current will be much lower when plugging them in, so no worries about that. If the carhode resistor is made variable, then the amp can be fine tuned for each tube. I even tried 6SN7 tubes for fun, and it sounds pretty good at low levels!
ye ye,
there is an error in megahertz schematic. B+ is A+...
Simply for precision!
Btw,
R470 in cathode of ECC88(475R for audiokit) maybe simply 1/4Watt? Or bigger is better?
They only indicate 10w for 1k resistance(cathode of 6080), and 3w for 15k resistance (anode of ECC88). Other resistances seem to be 1/4W...
Thanks.
there is an error in megahertz schematic. B+ is A+...
Simply for precision!
Btw,
R470 in cathode of ECC88(475R for audiokit) maybe simply 1/4Watt? Or bigger is better?
They only indicate 10w for 1k resistance(cathode of 6080), and 3w for 15k resistance (anode of ECC88). Other resistances seem to be 1/4W...
Thanks.
ok,
since a friend of mine gave me the 83 gas-filled rectifier, I decided to use this for lilliput.
Unfortunatlely informations are hard to find and also all the thread in this forum concern only general discussions about mercury tubes.
I know I have to make pre-heat of filaments and also I want to use an LC system(choke input filter).
The best datasheet I found is from GE.
It says(for choke input filter):
Inductance of choke: 3H(design center) - 3.3H(Absolute)
Maximum DC output Current: 225mA(design center) - 248(absolute)
Voltage drop: 15V(design center) - 17V(absolute)
So I think to do in this way:
2 resistances of 50R each one(suggested by datasheet) for plate protection.
A choke of 3H/300mA
A cap of 470uF
the rest of supply in normal way(like schematic)
Now the questions are:
Does the 83 tube work electrically well in this condition or I made mistakes?
I saw in the datasheet( http://www.mif.pg.gda.pl/homepages/frank/sheets/093/8/83.pdf ) only curves for 400V and 500V DC plate input...there is the possibility to have the 215V needed by lilliput?
And if it is possible, How I can obtaint the perfect voltage for the sec. of transformer?
Thanks
since a friend of mine gave me the 83 gas-filled rectifier, I decided to use this for lilliput.
Unfortunatlely informations are hard to find and also all the thread in this forum concern only general discussions about mercury tubes.
I know I have to make pre-heat of filaments and also I want to use an LC system(choke input filter).
The best datasheet I found is from GE.
It says(for choke input filter):
Inductance of choke: 3H(design center) - 3.3H(Absolute)
Maximum DC output Current: 225mA(design center) - 248(absolute)
Voltage drop: 15V(design center) - 17V(absolute)
So I think to do in this way:
2 resistances of 50R each one(suggested by datasheet) for plate protection.
A choke of 3H/300mA
A cap of 470uF
the rest of supply in normal way(like schematic)
Now the questions are:
Does the 83 tube work electrically well in this condition or I made mistakes?
I saw in the datasheet( http://www.mif.pg.gda.pl/homepages/frank/sheets/093/8/83.pdf ) only curves for 400V and 500V DC plate input...there is the possibility to have the 215V needed by lilliput?
And if it is possible, How I can obtaint the perfect voltage for the sec. of transformer?
Thanks
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