In my opinion if you've got 87 dB efficient speakers you should be looking at a push/pull project, preferably a big one. I'd be thinking about building a pair of Dynaco Mk III clones. I'd rather go for one with a modified driver board, but some people prefer the stock circuit with the 6AN8. There's plenty of other good choices for Mk III driver boards too - DIYTube's Poseidon, the Curico board, and the VTA board just to name a few.
Depends on your listening habits, etc. If this is for acoustic music in your office then perhaps it would be sufficient. If it's for your main system and you listen to Ozzie Osbourn at 100 db, I'd consider PP. Maybe a EL34 or KT88 UL. If you want to experiment, you can usually also try triode with a few mods to the circuit. The Dyna-clone designs would be worth checking out, as mentioned above by Ty Bower. The MkIII's are KT88 based, and the ST-70 is EL34 based.
No, it won't rock the house. I use 87db Yamaha NS-10 studio monitors in my lab which is only 10 by 11 feet. 8 WPC will get plenty loud in that small room, and I use a 2 WPC amp for much of my listening on those speakers.
UL with KT88's can deliver up to 14 watts. 14 WPC doesn't make the little Yamahas much louder so I usually run the Simple SE in triode mode.
I am not familiar with your speakers but I have discovered that the Yamahas and many other small driver speakers reach their maximum SPL in the 10 watt range. The cones are nearly at their full excursion on bass notes with 10 watts, and more power just makes more distortion. I have used tube amps with up to 50 WPC on the Yamahas and they just dont get much louder than with a 10 WPC amp.
On the other hand I have a pair of Open Baffle 15 inch Silver Iris speakers mounted in old console radios in my living room. They are rated at 96db and I have not found the power level at which the power / SPL curve begins to compress. They will literally rock the neighbors house with a 14 WPC KT88 powered Simple SE in UL mode. 50 WPC will bring the cops!
So 8 WPC may be sufficient on your speakers if used in a small room for "near field" applications. It is possible that additional power may not help. The best thing to do is borrow an amp in the 8 WPC range (and a bigger one if available) and find out before spending a lot of money.
It should be noted that a watt is a watt regardless of the source, but the saying that "tube watts are louder than SS watts" carries some merit. A solid state amp will begin to exhibit audible nastyness as soon as it touches clipping. A zero feedback tube amp can be pushed well into clipping on loud bass before being noticed. A tube amp with feedback lies somewhere in between. This allows a tube amp to be turned up more than an identically powered SS amp.
George-
Thanks for the info. The ZTR's are a 2 way ported floorstander. I think it's a 38 liter cabinet. Here's the link to the design http://www.zaphaudio.com/ZRT.html
I currently run a 50W SimAudio integrated amp and I rarely have the volume knob past 9'oclock
Thanks for the info. The ZTR's are a 2 way ported floorstander. I think it's a 38 liter cabinet. Here's the link to the design http://www.zaphaudio.com/ZRT.html
I currently run a 50W SimAudio integrated amp and I rarely have the volume knob past 9'oclock
So you have 87dB speakers....
Speaker sensitivity really matters. Getting just 3db more from the speakers does the same as doubling the amp's power. And as the amp gets larger it is hard to continue with the same clean single ended sound. You would have to go push-pull.
If you like the music turned up and you have something other then a small space then with your speakers you'd likely want a push pull amp with a pair of larger octal tubes per channel. 35 to 50 WPC would be ideal but half that if you don't turn it up to past where you can talk over the music
Build a smaller amp first. Maybe a really small one for "computer speakers" or even headphones. You learn as much building a 1 to 4 WPC amp as a larger one and it costs a lot less, transformers for a small amp can be had for under $20 each if you hunt a round
I've settled on UL with feedback using Edcor GXSE OPT's and KT88's recently. I've got it driving a pair of home-made 88+ db bookshelf speakers that sit about five feet off the floor. The room has a concrete floor with maple flooring. The back of the room is open to the rest of the main floor that is also oak floored.
I had a party a couple weeks ago and the Simple SE had no problems providing music though the whole house. Mostly Jazz, that came through clear and detailed. Even Jack Johnson's Curious George soundtrack played loud with no stress. I can turn it up louder than what I regard to be comfortable and not be displeased.
I had a Marantz 8b wired up to the same config while I was operating on the Simple SE. The Simple SE whoops it. That's my opinion and I'm sticking to it.
My point is, the Simple SE with even economy iron sounds great in UL. Your room can play a big factor in offsetting less efficent speakers. With a bit of patience you can wire up a switch so you can choose between UL and triode, feedback or no feedback. It's a worthwhile effort.
I had a party a couple weeks ago and the Simple SE had no problems providing music though the whole house. Mostly Jazz, that came through clear and detailed. Even Jack Johnson's Curious George soundtrack played loud with no stress. I can turn it up louder than what I regard to be comfortable and not be displeased.
I had a Marantz 8b wired up to the same config while I was operating on the Simple SE. The Simple SE whoops it. That's my opinion and I'm sticking to it.
My point is, the Simple SE with even economy iron sounds great in UL. Your room can play a big factor in offsetting less efficent speakers. With a bit of patience you can wire up a switch so you can choose between UL and triode, feedback or no feedback. It's a worthwhile effort.
I offer 1 more possibility, definitely a step toward high end and a trip further into the DIY spiral.... Bi-amping. Build your first amp, be it a Simple SE (no need for the big bux version, but it wouldn't hurt) or another high quality 2 to 5 WPC amp. Build or buy an active crossover preferably one with a subwoofer output. Use the active crossover to split the highs and lows between the source and the amps. Then you use the newly constructed tube amp to drive the tweeter and your current SS amp to drive the woofer (bypassing the crossover in the speaker). You keep your current volume level, and get tube sound where it benefits most.
Then when the DIY fever strikes again, you get do decide...do I want to build an amp or a subwoofer? Do I want to add more low bass, or bring the tube sound to the rest of the system? You decide.
When it is time for the second tube amp. A decent sized P-P amp along the lines of a Dyna 70 or similar would do nicely. The subwoofer, something with a SS plate amp in the 100+W range. That way it shouldn't clip unless you really hit it hard.
What about the first tube amp? The tweeter is far more efficient than the woofer (thats why there is a resistor in your passive crossover), so you don't need a lot of power. You don't want it to clip either, but 5 WPC is plenty. Now you choose the tube that is going to give you the best sound in the 2KHz and up region. Save the KT88's for your woofer amp. My first choice would be a DHT, but this is your first amp, so we will stich to IDHT's. My first choice here would be a trioded 6V6 but it only gives 2 WPC (maybe enough), followed by a good EL34 (trioded) or maybe a 6L6GC (again trioded). Next you need an OPT that works great in this range, you don't care about the bass. Because of this the 7 pound rule goes out the window, and so does the power rating. You want a frequency response that goes to at least 30 KHz and is ruler flat from 500Hz to 25 KHz. Remember those $30 Edcors, they are excellent for this application, but ugly. They don't get hot, so put them in a box, or use the smaller James transformers.
The trioded 6V6 is a great sounding amp, but it requires a different power transformer that the usual 750 VCT unit. You want something in the 540 to 550 VCT range.
Then when the DIY fever strikes again, you get do decide...do I want to build an amp or a subwoofer? Do I want to add more low bass, or bring the tube sound to the rest of the system? You decide.
When it is time for the second tube amp. A decent sized P-P amp along the lines of a Dyna 70 or similar would do nicely. The subwoofer, something with a SS plate amp in the 100+W range. That way it shouldn't clip unless you really hit it hard.
What about the first tube amp? The tweeter is far more efficient than the woofer (thats why there is a resistor in your passive crossover), so you don't need a lot of power. You don't want it to clip either, but 5 WPC is plenty. Now you choose the tube that is going to give you the best sound in the 2KHz and up region. Save the KT88's for your woofer amp. My first choice would be a DHT, but this is your first amp, so we will stich to IDHT's. My first choice here would be a trioded 6V6 but it only gives 2 WPC (maybe enough), followed by a good EL34 (trioded) or maybe a 6L6GC (again trioded). Next you need an OPT that works great in this range, you don't care about the bass. Because of this the 7 pound rule goes out the window, and so does the power rating. You want a frequency response that goes to at least 30 KHz and is ruler flat from 500Hz to 25 KHz. Remember those $30 Edcors, they are excellent for this application, but ugly. They don't get hot, so put them in a box, or use the smaller James transformers.
The trioded 6V6 is a great sounding amp, but it requires a different power transformer that the usual 750 VCT unit. You want something in the 540 to 550 VCT range.
Regarding the efficiency of the ZRT's the tweeter is 92.5 and the woofer is 87. I'm not sure what that gets me but it's surely below 90.
My concern with the Simple SE is that I'll make it and it won't work well with the ZRT's.
Is there another easily made SET amp that would give me more power? Can the Simple SE be set up for monoblocks? What about a 300B PSE?
The Audio Note stuff looks incredible but so is the price. I'd like to keep it around a 1000 or so.
My concern with the Simple SE is that I'll make it and it won't work well with the ZRT's.
Is there another easily made SET amp that would give me more power? Can the Simple SE be set up for monoblocks? What about a 300B PSE?
The Audio Note stuff looks incredible but so is the price. I'd like to keep it around a 1000 or so.
The first step is to clearly specify the amplifier you want. The key here, and it is hard to do ifyou are not used to thinking this way is the _specify_ and NOT design.
For example: You might say "The amp shall be a single ended design that can drive my 87db speakers to XX db listing level."
Plug in any value of "XX" you like. This will imply a level of power (watts) at the speaker terminals.
The next step is to find an output transformer that can meet you power requirement, then figure out what power tube(s) you need. For high power levels you may need to go with paralleled output tubes. if a single KT88 or EL34 is not enough.
If you don't like the result (because maybe four parallel KT88 tubes borders on the insane) then you are forced to chage the your written requirement. Maybe you eliminate the words "single ended" or lower the value of "XX". or change the speaker type.
If you're looking for more power from an easy kit, I think you'll need to go Push-Pull or 300B for more power.
If you are curious about how loud 7 or 8 watts is with your speakers (or 1 or 2 watts for that matter), and have access to a scope or averaging voltmeter, check out this thread:
http://www.diyaudio.com/forums/tubes-valves/153154-power-measurements-normal-listening-levels.html
If you can wire a scope across your speaker terminals and listen to music at various volumes on your existing setup, you can get a crude idea of what volumes to expect from low power SE.
http://www.diyaudio.com/forums/tubes-valves/153154-power-measurements-normal-listening-levels.html
If you can wire a scope across your speaker terminals and listen to music at various volumes on your existing setup, you can get a crude idea of what volumes to expect from low power SE.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.