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In Reply to: RE: Venturing into SET active system. Does a 45 have enough power? posted by Lenin on August 22, 2016 at 13:51:27
Sorry, but E55l aren't on my radar. I'd rather look into the "usual SET suspects" for an initial venture. I'm building a speaker too, so don't want to go overly complex in the first stage. 45 and 2A3 are in the shortlist, with 45 having a bit of an edge in terms of my preference. Coincident Dynamo 34SE SEP could also be a more powerful option, but if 45 have enough power I think I'll go with the A-08S.
Follow Ups:
I have a direct coupled amp that plays the 2A3 and 45, with a rectifier substitution. I prefer the 45, but i think mostly due to the mids where i spend most of my time anyway (not the treble, as you plan).
Direct coupled amps tend to be a bit more noisy than cap coupled amps, so i wouldn't take the DC route. But as i am sure you know, there are a lot DIY schematics out there for the 45.
Frihed89, your post sent me looking into whether the A-08S is a direct coupled amp or not.
According to the Stereophile review by Art Dudley it seems the A-08S is not DC (although the first gain stage is capacitor-coupled to the 45s: "The 717A's anode is capacitor-coupled to the signal grid of a 45 triode").
But acccording the 6moons review by Srajan "By DC-coupling the 45s and 717A drivers, noise levels for the revised amp are given as 0.3mV to 0.7mV".
Do you happpen to know which one is right, and whether the A-08S is DC or not?
No, I don't. I looked at a couple of shots of the internals, and the use of turret boards confounded me. I don't have them on my Fi Audio 2A3/45 monos.
Maybe the best thing is to send an email to Jac-Music and ask. On a speaker amp, it may not matter, although your treble unit is quite sensitive. AC vs DC to the filaments is another noise issue, perhaps even more important than the coupling strategy. It is a controversial topic and there is no last word.
Sadly, there are not many commercial 45 amps on the market.
Thank you.
As usual there are multiple paths in audio. But the key takeaway from this thread is a 45 driving a tweeter and another driving the midrange should be enough. This was my critical question. So I'm happy.
Then, as usual, there are multiple other aspects to take into consideration regarding implementation. I'm taking note of noise as a potential issue, particularly with the tweeter amp. All the reviews I've seen about the A-08S highlight how dead silent it is for a SET, so that's a good start.
Many think highly of your Fi Audio too - aesthetics skews my wife's opinion towards the Yamamoto, though, since this will be in the living room.
I would be interested in discussing with A-08S owners. Please let me know if you know of any users here with experience with these amps.
Thank you!
I got in when it was 6 months. I'm very happy with it. I only use it with the Type 45 these days.
Its cap coupled, I've looked inside and seen the circuit. There are FAR better alternatives available. Don't waste your money. LOL, especially on two of them !!I use a Type 45 DC amp on my wire-modified ALTEC VOTT A7-800s. As "I" DIY build it, it has power and dynamics to BURN !!!
I have a friend in KC, MO who runs ONE A-08S on his ALTEC ( A-4?? ) system with a total of FOUR 515Bs and two 288s. The speakers are set up in a converted turn of the 19th century decommissioned fire house.
Contact me, and I will give you his contact information, so you can talk to him directly, hear what his direct experience is !! He had my prototype, a DC 45 amp for about two months on his system in 2015, and went back and forth comparing it to his A-08S 45 amp. You really need to talk to him !!
The ONLY commercial amp I know of in all of audio, that cuts the mustard, is the Serious Stereo 2A3 amp, it trashes everything else in the SET world, and DC set world, handily !! They will be at RMAF, Denver, October 2016. Call and talk to Dennis, he will help you , he KNOWS.
The quad amping, ( which you are thinking of ), adding a (1) an extra active stage and (2) using dissimilar amps with different signatures and timing - on EFFICIENT SPEAKERS - will be an UNfixable degrade compared to a well-executed passive crossover, a single GOOD amp, and a two or, at the most, three way speaker.
Remember this, it will save you much wasted time and grief :
KISS "rules"
in ultimate performance high-end audio set ups.
Jeff Medwin
Edits: 08/23/16
Right. An $11k amp sounds better than a $3k. It better do!
Can you point me to better SET alternatives within comparable prices?
I'm already actively running my system now. I've gone from "purist" to digital XO, DSP, time-alignment and I'm not going back. I know others don't share the point of view, and that's fine, while others do. I am now working on new speakers and replacing amps, but not revisiting the system concept.
Good suggestion sent, via email. An amp from China maybe.
An 11k amp is always overpriced and you probably help to pay the new Mercedes of somebody else...... Did i see a cheap EI transformer too?
Dc coupled is not a good idea, less reliable and there is always an electrolitic capaciter in the circuit path for bad sound. A normal capacitor is normally a lot better. If you want the bst is should have a 1:1 interstage to drive the powertube.
Lenin,
Respectfully, you are not well informed and not experienced in this.
But, ask yourself this : regarding coupling mechanisms :
HOW will a one-to-one interstage be better at signal transmission than three paralleled Cardas pure silver audio wires ( the direct couple mechanism )? How??
And please tell me, WHERE is there any electrolytic in such a circuit?
DC amps need not use an electrolytic, ones I make use 100% film caps everywhere !!
The amps are $15K for two monoblocks, last I saw, and READ all the user-reviews on it ( URL in my post above) obviously you have not !!
Jeff Medwin
If it is real dc coupled it should not have anywhere in the circuit a capacitor, not cathode de-coupling and not in the power supply. I doubt if you have a real dc amplifier, you have any schematic of it?Cardas silver is just a brand and just silver, nothing special to me. I have heared many fairytales about silver, silver can not do magic it is just in the mind of the person who uses it who thinks it dos magic. Btw silver is a "cheap" metal and cost less then $1/gram, even the cardas silver.
I also have heared many $10k amp/ loudspeakers and other top dollar equipment and i have never heared any of them worth the money. Some sounded really well but not worth that kind of money. It is mostly snobism.
A interstage has the best controle on the grid of the powertube.
But... If i see the work of Josh from Electronluv i will make an exception because its a peace of art if you look at it. (Not buying it for the sound)
Edits: 08/23/16
Thats incorrect.And also your comment about bias shift is also incorrect - it assumes too much, and negates certain developments (yeah I know, but I do these things).
Shane.
Edits: 08/31/16
"A interstage has the best controle on the grid of the powertube. "
Why is that?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
When using a interstage you have the possibility to have a rock solid bias because of the low dcr of the interstage. Of course you have to use a capable driver tube and use a stable fixed bias of the power tube otherwise you though away all the goods.....
Dc coupled tubes have drift ( not the best bias) and using capaciters for cathode decoupling is also not a good idea for the best performance.
An interstage can also provide for class 2, drive with grid current, if propper designed.
"...have a rock solid bias because of the low dcr of the interstage. "
I used to think that also but then someone explained that the grid current is not DC per se.
The grid current will start and stop periodically in accordance with the music signal that is causing it.
So now it is the reactance of the winding that comes into play, not the DCR.
A good grid choke (or the secondary winding of a good IT) will have a very high reactance, in many instances higher than the grid resistor that it replaced causing the bias to be less stable under class 2 conditions.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Grid current can only be there for very large signals where the grid of the powertube is driven in a postive grid signal. Then there is a much lower impedance so the driver has to be much more powerfull then normally. A normal circuit can't handle this but a powerfull driver+ interstage can.Remember this grid current is a very special situation where impedance is much different then normally so an interstage is still the best solution for a stable bias.
Edits: 08/25/16 08/25/16 08/25/16
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