Brett said:
I think you haven't read what I wrote
mark_titano said:Lundahl are a very good solution...just too expensive in this moment, I want to buy two 1660 interstage transformers ( 84€ each... here http://www.studiomaudio.com/ ,Torino, Italy) so my budget go down quickly.
I'm not sure that el 84 push pull will be my last amp but for sure I'll try other solutions with the 1660...so this is my priority.
Lundahl were my first choice...but I can't print money
Re: Megahertz vs Lundahl
For sure the first difference is that Megahertz don't build PP transformers
http://www.megahertzaudio.it/IT-listino.htm
Yugo said:
For sure the first difference is that Megahertz don't build PP transformers
http://www.megahertzaudio.it/IT-listino.htm
I've read the articles posts in this tread and some others that I've found on line. The designs more interesting are these:
http://www.vacuumstate.com/images/PP-1C.gif
http://www.diyparadise.com/buildel84c.html
http://www.audiodesignguide.com/my/pp3.html
I've read some articles on vacuumstate and I think that a ccs in the power stage could be a very good solution, something like the diyparadise design...but also differential design is very clever.
So I'm thinking, why not use the vacuumstate design? With the ccs on the power stage? And to split the signal from cd using this transformer
http://www.lundahl.se/pdfs/datash/1544a.pdf
and then built this line stage?
http://www.vacuumstate.com/images/RTP5_rev_1.GIF
Maybe I'm crazy but what do you think about it? Someone can help me to build something like this? It could work with an el84 power stage
http://www.vacuumstate.com/images/PP-1C.gif
http://www.diyparadise.com/buildel84c.html
http://www.audiodesignguide.com/my/pp3.html
I've read some articles on vacuumstate and I think that a ccs in the power stage could be a very good solution, something like the diyparadise design...but also differential design is very clever.
So I'm thinking, why not use the vacuumstate design? With the ccs on the power stage? And to split the signal from cd using this transformer
http://www.lundahl.se/pdfs/datash/1544a.pdf
and then built this line stage?
http://www.vacuumstate.com/images/RTP5_rev_1.GIF
Maybe I'm crazy but what do you think about it? Someone can help me to build something like this? It could work with an el84 power stage
I've built both the PP1C and the PP2CS and they're excellent, but the cascode front ends have too much gain to run straight from CDP using EL84's for the O/P tubes.mark_titano said:
I've also built a variation in the SE-IT-PP KT88 (with 6550 and 12E1 too). Again, a very good little amp, but with a different presentation to either of the Vacuumstate designs.
You don't need the Lundahl as an input signal splitter with the Vacuumstates, just ground one grid on the cascode. The Cuiffoli doesn't need it either.
You don't need the linestage at all, unless you're going to drive a really! long capacitive cable between the CDP and the amp. You definitely don't need the gain.
Suggested signal path would be; CDP - passive volume control (at amp input) - then either the VS PP1C (with EL84's) or the Cuiffoli design with EL84's and an ECC99 as the driver (perfect amount of gain)
SY said:
Well, I'm not so expert to understand which are the problems you are talking about, so please, try to explain why you don't like it so much. It seems to me ( I repeat, I've no long experience in tubes designs...) simply and with constant problems. It has no need of calibration when the circuit is well dimensioned...I'm wrong?
Brett said:
Thankyou, you have shoot my target
And with el34? When you have built pp1&pp2, have you used a preamp or run it directly from the cdp? I'm not sure to use el84... I need at least 10W so I have to use ul connection with 84s. I'm thinking that maybe using el34 in triode connections in a better idea.
Brett said:
The idea of the input transformer take place in me just to have a galvanic isolation from cdp output to amp input. With the plus of a good impedance match.
My english is very bad so maybe you don't understand what I've tried to say... my idea was to have this signal path: cd->volume control->input transformer(se input/split output) full differential vacuumstate preamp->full differential pp1
I hope now it's clearer
Brett said:
Thankyou
I used the -1C with EL34 and -2CS with 6550's. I like the idea of trioded El34 rather than EL84 in UL. PP1C built to VS specs is about 12W, iirc.mark_titano said:Thankyou, you have shoot my target
And with el34? When you have built pp1&pp2, have you used a preamp or run it directly from the cdp? I'm not sure to use el84... I need at least 10W so I have to use ul connection with 84s. I'm thinking that maybe using el34 in triode connections in a better idea.
Galvanic isolation is a great idea, but I would use CDP - 1544 - VC* - amp otherwise you're going to be driving the input of the transformer with a varying, and at times quite high impedance, not good. Unless you run the 1544 in 2:1 or 4:1 there won't be any benefit in matching and I'd run it 1:1
You need a quad stacked 100k or greater linear pot, with each wiper shunted to ground by a 15k, run balanced. For the Cuiffoli amp, you only need a std dual pot.
http://sound.westhost.com/project01.htm
Well, in the output stage, your current source will need to have an order of magnitude more compliance and power dissipation than it would on the input stage. Moreover, the output stage is most likely to be the limiting element for clipping- now you have to consider not only the power supply and driver behavior, but also what the current source and its reference do under overload conditions and how they all interact for recovery (recovery from overload is one of the most important and neglected aspects of tube amp design).
Tis I suppose indeed quite hard to design a current source for the output stage...I would not do it...just yet...especially if it is going to be your first amp Mark.
However..Allen Wright has done it and won the Product of the year from the Enjoy the music folks...whatever that is worth..
http://www.enjoythemusic.com/magazine/viewpoint/0104/aachapter52.htm
This is one reason I want to try a grid choke...I've lent mine to dhtrob.com and his initial impression was...that his amps sounded faster and had a quiter background...I am hoping that his final report will also be positive...
They where the Magnequest BCP-16NI GC...sorry to have hi-jacked your thread Mark...
Regards,
Bas
Thankyou all for the reply.
SY can you tell me something more about recovery from overload ? Which parameters influences this neglected aspect?
How do you design a good push pull output stage?
There is some good manual on line or some recommended book that I have to read to understand these aspects?
Yesterday I found this discussion...
http://db.audioasylum.com/cgi/m.mpl?forum=tubediy&n=42896&highlight=pufff&r=&session=
Interesting
SY can you tell me something more about recovery from overload ? Which parameters influences this neglected aspect?
How do you design a good push pull output stage?
There is some good manual on line or some recommended book that I have to read to understand these aspects?
Yesterday I found this discussion...
http://db.audioasylum.com/cgi/m.mpl?forum=tubediy&n=42896&highlight=pufff&r=&session=
Interesting
The best explanations I've seen regarding overload recovery (with nice pictures) are some articles by Norman Crowhurst that appeared in Audio on the late '50s. I think they're around somewhere on the 'net- if not, they've been reprinted in the Audio Anthology series from Old Colony. He also deals with this in the book "Understanding Hifi Circuits." Morgan Jones also discusses these issues in "Valve Amplifiers." You ought to own both these books if you want to start playing with tube circuits.
The principal bad-actor is blocking from the RC coupling to the output stage. I'd want to think pretty hard about how to set voltage ratings and compliance of the CCS to minimize that problem.
The principal bad-actor is blocking from the RC coupling to the output stage. I'd want to think pretty hard about how to set voltage ratings and compliance of the CCS to minimize that problem.
Experimenting with EL84 PP
Hello,
I have been experimenting with EL84 PP; a way to learn and understand circuits.
First I have built Morgan Jones Bevois Valley; I didn't like it at all, the sound is somewhat sterile compared to a borrowed Leak amp.
I am wondering if someone can suggest a good circuit ( no NFB), yet simple! I don't need much power; 5 watts are more than enough.
I have got a few EL84 and Ecc99 laying around, plus 2 pairs of pushpull output tx with ultralinear taps.
By the way, I've bought (very very cheap) a pair of brand new output transformers ( 9K, ultralinear, taps at 20%) and need to know what can they be used for?
Thanks for your input
Hello,
I have been experimenting with EL84 PP; a way to learn and understand circuits.
First I have built Morgan Jones Bevois Valley; I didn't like it at all, the sound is somewhat sterile compared to a borrowed Leak amp.
I am wondering if someone can suggest a good circuit ( no NFB), yet simple! I don't need much power; 5 watts are more than enough.
I have got a few EL84 and Ecc99 laying around, plus 2 pairs of pushpull output tx with ultralinear taps.
By the way, I've bought (very very cheap) a pair of brand new output transformers ( 9K, ultralinear, taps at 20%) and need to know what can they be used for?
Thanks for your input
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