Driver and enclosure for 4 watt amp, 12x12 room, moderate volume chamber music? - Page 3 - diyAudio
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Old 11th December 2010, 02:42 AM   #21
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But sreten, it is optimized for 2 ohms. Steve winds his own OPTs. There are special loudspeakers just for this amp.

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Old 11th December 2010, 03:18 AM   #22
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Quote:
Originally Posted by zenga123 View Post
I'll look for something in the 94 db and 8 ohm range.
The Zen is much happier with lower impedances. It struggles a bit at higher impedance, althou one of the favorites with the Zen is the EdHorn.

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Old 11th December 2010, 03:31 AM   #23
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sreten - have you actually heard one (or more) of the Decware amps, or researched the design?

I have - more recently than the model and vintage of the review in your link - of course the price has increased in the 10yrs since (now at $775 for the factory built unit - but still available in PCB kit form for $300 USD)

It was an audition to one of these approx 8yrs ago that opened my eyes to the appeal of flea powered SET amp, and I've built/owned more than a few kits and scratch build DIY amps since - including Bottlehead Paramour 2A3s, George Wright Mono7 300B, and a variety of SET and P/P EL34 and EL34s. Several of the scratch builds were as close as possible to the freely published Zen schematics a possible without the custom OPTs.

This is quite a nifty little piece, and as Dave mentioned the combination of Steve's in-house built OPTs, and the resultant operating conditions are a bit out of the ordinary. It really is quite more comfortable with lower impedance loads than one would normally suspect. No, it's not a Krell arc-welder, or an ARC Reference 610T, and doesn't pretend to be the last word in triode-ness, but it's a very sweet, fast and musical little gadget that I'd wager could fill the bill for the application that zenga describes.

If he has space to accommodate a speaker system with more efficient driver(s) than the Mark Audio /CSS EL70 that has been discussed for the past few posts, so much the better. ( i.e. Fostex FE126E in "Horns" or DIY designs is widely enjoyed by a lot of owners of the Zen amp)

sorry if that sounded a bit petulant
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Old 11th December 2010, 04:17 AM   #24
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I appreciate the interesting comments. From what has been said, the Fe126En in an MK3 seems like it would be a good match for the Zen amp.
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Old 11th December 2010, 04:35 AM   #25
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Would it be better to put two 4" FE126En in a cabinet to get them to 4 ohm? If so, has there been a cabinet designed for that?
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Old 11th December 2010, 04:58 AM   #26
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Perhaps a vertical half of this?

Large Dual FLH with multiple ENabled FE126en drivers

I think you'll be fine with 1.

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Old 11th December 2010, 05:11 AM   #27
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I don't know if it helps, but I'm listening to a low power SET with full range speakers. I'm using the Fostex 127E, the now discontinued sibling of the FE126. My amplifier puts out somewhere between 1W and 2W. To get an amplifier twice as loud would require 10W, so although the Decware Zen amp is more powerful, it's still likely that my amplifier gives some useful insight.

With this roughly 90dB of full range speaker I'm using, in a room that is 12' x 15' it is loud enough on full volume to listen to music providing the kids aren't disturbing me. It's on the edge of being loud enough and it's an amplifier I routinely operate at full volume. With some 88dB Fountex speakers I made the amplifier is only used at full volume (this speaker is destined for a SS amp).

A SET amplifier couples the output tube to the load with a transformer designed to ensure the tube is operating under the right conditions - with good power and low distortion. It's possible to match the tube to different speaker loads by having different taps on the transformer; if there's a dedicated 2 Ohm tap then you should be OK. If it doesn't have a dedicated 2 Ohm tap then you had better experiment. As far as I can see, if you have an opportunity to match your speaker to the amplifier you already own and therefore, should choose a speaker with an impedance that matches one of the taps on the output transformer. If it doesn't have any taps and is described as being suitable for 8 Ohm, then use 8 Ohm nominal speaker impedance. Multiple drivers per speaker are potentially an added layer of complication.

Hope this is useful, but bear in mind that my experience is limited - I know Dave's a big user of Mark Audio drivers, he has listened to them extensively as well as Fostex drivers and knows their performances well. His advice has always be useful for my projects.
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Old 11th December 2010, 05:39 AM   #28
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Quote:
Originally Posted by Bigun View Post
I don't know if it helps, but I'm listening to a low power SET with full range speakers. I'm using the Fostex 127E, the now discontinued sibling of the FE126. My amplifier puts out somewhere between 1W and 2W. To get an amplifier twice as loud would require 10W, so although the Decware Zen amp is more powerful, it's still likely that my amplifier gives some useful insight.

With this roughly 90dB of full range speaker I'm using, in a room that is 12' x 15' it is loud enough on full volume to listen to music providing the kids aren't disturbing me. It's on the edge of being loud enough and it's an amplifier I routinely operate at full volume. With some 88dB Fountex speakers I made the amplifier is only used at full volume (this speaker is destined for a SS amp).

A SET amplifier couples the output tube to the load with a transformer designed to ensure the tube is operating under the right conditions - with good power and low distortion. It's possible to match the tube to different speaker loads by having different taps on the transformer; if there's a dedicated 2 Ohm tap then you should be OK. If it doesn't have a dedicated 2 Ohm tap then you had better experiment. As far as I can see, if you have an opportunity to match your speaker to the amplifier you already own and therefore, should choose a speaker with an impedance that matches one of the taps on the output transformer. If it doesn't have any taps and is described as being suitable for 8 Ohm, then use 8 Ohm nominal speaker impedance. Multiple drivers per speaker are potentially an added layer of complication.

Hope this is useful, but bear in mind that my experience is limited - I know Dave's a big user of Mark Audio drivers, he has listened to them extensively as well as Fostex drivers and knows their performances well. His advice has always be useful for my projects.
Very helpful, thanks Bigun. Both you and Dave suggest using one driver, which sounds like the simpler solution.
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Old 11th December 2010, 07:28 AM   #29
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Current version of the amplifier.

Click the image to open in full size.

Quote:
Original Zen Triode Amplifier

model SE84C+

2 watts x 2 or 6 watts x 1
Single Ended Triode Class A1
SV83 or EL84 Output tubes
For speakers between 1 & 8 ohms.

Features 2 inputs and Volume Control,
no preamp is needed, but you can still
use one.
note the 1>8 ohm bit...

Further, from here Audio Tube Amps by DECWARE(tm) Zen Triodes (noteL Steve is a master at turning a phrase)

Quote:
An 8 ohm load yielded around 1.5 to 1.9 watts RMS. A 4 ohm load gave us around 2.38 watts RMS and a 2 ohm load gave us around 3.21 watts RMS. In the same tests, the amplifier was bridged using our series bridging technique made possible by floating the outputs. In this configuration the now mono amplifier exactly doubled all the figures above.
more: http://www.decware.com/newsite/articles.html

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Old 11th December 2010, 05:53 PM   #30
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You get more power by steepening the load-line for the output tube, it swings over a wider range of current. if you adjust the tube loading through different transformer winding ratios (taps) you can keep the same load-line but the power will not then increase into lower impedance loads. If I understand this correctly. So if you are operating the amp with higher output power you must therefore be exposing the tube to a larger current swing at the anode. This also increases distortion - there's no free lunch. Performance will be better when the amp is operating at lower power and this means the most sensitive speakers.

I'm not the designer of the amp - not an expert by any means. But as you say, people with commercial interests always have an incentive to promote what is good for their business whether it be through mastering a turn of phrase or otherwise.
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