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In Reply to: RE: 6883B for use as a audio power tube posted by drlowmu on August 31, 2014 at 09:09:34
Who decides that 100 watt amps means one is not int tubes anyhow? What doctrine is that? May be yours, mate, but certainly not everyone's.The speakers I'm using are ATC SCM 19's (with matching subwoofer) which sound WAY better than most of the speakers of higher efficiency you are recommending. The 1625 DIY amps I have, which are 120 watts a channel, using a Thomas Meyer 6AH4 preamp, sounds a lot better than just about any solid state setup I've heard.
The circuit topology has as much or more to do with the sound as the tube itself. Other DIY folks have successfully made very nice amps using this tube. To me, what IS a waste of money is buying current production 6550's which are not as good as the NOS tubes. The 6550A NOS tubes are priced silly, IMHO. Why not instead use a well made NOS tube that is long lasting? Just need to ensure the engineering principals are adhered to, and all should be well. The 1625 tube is not considered an audio tube, yet, done right, it sounds outstanding. I had a Citation II, and these 1625 amps sound better overall.
This IS a DIY thread after all. I have not really heard a bad tube, more like bad designs.
If the tube does not work out, then it will be a simple matter to convert to the 1625 tube with very little additional changes required. I don't think that will be the case, but when one plans a project like this, never hurts to have a plan b. :-)
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
Edits: 08/31/14 08/31/14 08/31/14Follow Ups:
Misquoted. I never said " With Respect", nor did I call you names like snob.
I can see your mind is made up, and it was useless for me to challenge your thinking processes. I read all your rationalizations.
Continue on, have fun !
Jeff Medwin
PS, I used the term "respectfully question", didn't I, hardly combative !!
Then I will be the first to say I'm sorry :-). The with respect was my observation about your thought process, and challenging the notion that this project was a wasted effort.
I just get a little relied sometimes when folks say "you gotta do this or that, or your not into it" like the high powered tube comments. Tubes can sound great with both low and higher power outputs.Additionally, did not see a solid reason listed from your post not to proceed. The tube is useable from a engineering standpoint. The spec sheet does provide audio performance, others have successfully made amps with this tube, and my preferred speakers need the wattage to perform their best. Had I not has such excellent success with another RF transmitting tube (1625), would not have taken a chance with this.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
Edits: 08/31/14 08/31/14
Peruse this, and think about it. No response needed. Just put it in your conciousness. Have FUN !!!
Jeff
Lots of claims with no credible explanations. The reason no manufacturer specifies "useable power" is that it's not measurable. How do you quantify "sounds good" or "sounds best"? It's a highly subjective term. We have reached a point where many people (perhaps most) are perfectly satisfied with 2" speakers driven by MP3 players. They would claim that it "sounds good".
The best example of how far "we" have regressed is in "home theater" systems. We are up to 8.1 - 5.1 systems are now outdated. I tried to purchase a "center speaker" at Best Buy and Radio Schick. Guess what - they aren't readily available any more, because "everyone" wants a "soundbar". What exactly is the point of a 5.1 system when all the speakers are in one box? Sorry for the unrelated tirade.
Deckert's gear and his website was inspiration get me started designing and building. I jumped from Decware to Harvey Rosenburg's site (postmortem)....for a few years...
Stuben
I am having trouble buying a 1 watt amplifier being more powerful than a 50 watt amplifier.
As simple as this statement is, a power supply with good regulation & reserve energy plus a healthy driver and reasonably sized audio transformers should perform well.
I have to agree. A properly designed amp should have all these qualities.I get the points being made in the Decker paper, and the efficiency of the transfer function certainly must be taken into account. I would propose that even a higher powered push pull tube amp can provide those magical qualities at lower to moderate volumes if designed correctly.
A properly matched preamp stage can help the power amps provide that type of performance. A real game changer for improving the performance of my 1625 based amps was insertion of a DIY based Thomas Meyer 6AH4 preamp design. My goodness, what a improvement that brought! The noise floor is lower than just about any preamp I've ever heard or owned, including high end SS preamp types. This preamp transformed the power amps from very good to something special.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
Edits: 09/01/14
Here is a picture of the 6AH4 preamp insides.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
"Had I not has such excellent success with another RF transmitting tube (1625), would not have taken a chance with this."
It will be as successful as any pentode can be, and I do not mean to impune the performance of pentodes when I say that. All power pentodes require prodigious amounts of NFB. Therefore, their different sounds are likely more the result of topology and support components than the tubes themselves. I've heard plenty of pentode amplifiers that I thought were quite good, although I do personally favor the SE variety. Carry on and keep us posted!
--------------------------
Buy Chinese. Bury freedom.
Very fair points on the pentode sound. What surprised me when the 1625 amps were done is just how good a properly designed pentode output can sound. The 3D sound-stage, low level detail, and dynamics that seem to provide more contrast than I've heard from triode or ultraaliner tube amps.
The ATC speakers are among the best at any price point. At 85 db/w, they do need a good 50 watts or more to sound their best. They are not a difficult load to drive, so that works in the amps favor. They sound incredible with tube amps.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
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