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Old 23rd March 2003, 09:23 AM   #1
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Default Suggestions from the tube world

What tube anps would you recommend for this

http://www.diyaudio.com/forums/showt...&postid=149374

To drive the Manger
http://www.manger-msw.com/en/inhalt.html

is perhaps the most challenging one, not in ohms or db, but bandwidth detail and speed
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Old 23rd March 2003, 11:49 AM   #2
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Hi,

To get most detail and speed the obvious choice is an OTL amp, there are nothing to compare really. The sensitivity of the Manger is reasonable and impedance is quite forgiving also so I dont see any problems with using an OTL. However the cost limit you put in an earlier mail is somewhat of a problem...

Regards Hans
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Old 24th March 2003, 02:15 AM   #3
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Default only need one channel

tubetvr
What advantages do OTL amps have (over other tube designs, or SS)?

What is the starting point for cost of an OTL amp? Remember I only need one (center) channel.

While I guess one channel designs are non-existent, presumably I can just build half a normal stereo design.

What designs/ sites should I investigate?

TIA
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Old 24th March 2003, 05:04 AM   #4
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I made a design where I have to buy $80 of iron, caps and other parts.

Come to think of it, that's one of my more expensive projects!

Tim
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Old 24th March 2003, 05:20 AM   #5
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Default only need one channel

Hi,

Quote:
What is the starting point for cost of an OTL amp? Remember I only need one (center) channel.
While I'm a big fan of OTL amps, using that on a center channel for a hometheater setup seems a bit over the top to me...even using a formidable speaker such as a Manger for a center channel is overkill already to me.

Not that I'm an expert on hometheater though.

As for cost, think in the 1,000 USD range for a single monoblock OTL if you have to buy everything.

Cheers,
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Old 24th March 2003, 05:41 AM   #6
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Default Ouch!?

I agrre it's bit over the top, but I want to do it once, and do it well.

Is the ballpark $1000 to buy new, 2nd hand, or build?

And how do OTLs sound vs say a 2A3?
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Old 24th March 2003, 05:45 AM   #7
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Default Re: only need one channel

Quote:
Originally posted by rick57
While I guess one channel designs are non-existent, presumably I can just build half a normal stereo design.

What designs/ sites should I investigate?

TIA
Yep, you can build one channel and use it for the centre. However, after setting up, and in some cases completely respecifying and rebuilding a few HTs, the most important part of the whole setup is the consistency in voicing the front 3 channels. All 3 channels <i>must</i> have similar frequency response, dispersion and voicing, so the choice is simple; either use whatever you have for L&R amps for the centre too, or build 3 matching amps. That said, unless you have a large (wide) room amd narrow dispersion speakers, I've often found that a centre is not needed at all, and can mess with the coherency of a good front based system.

I think an OTL for the centre is a woftam.
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Old 24th March 2003, 07:31 AM   #8
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Default OTL advantages

Hi

general advantages with tube OTL amps:

Transient response and bandwidth, OTL amps have much better transient response then any transformer coupled tube amp, for instance in my DIY OTL frequency response is flat from 10Hz to 200kHz and rise time is < 1 us, a 100Hz or 10kHz square wave is amplified without any obvious distorsion and without any ringing.

Higher open loop bandwidth and lower distorsion in open loop compared to most SS designs, (most SS designs have a dominant pole at low frequency in order to be stable with heavy feedback)

Low distorsion with limited feedback and few circuit elements, in my case 0.25% at 20W and 0.05% at 2W with only 13 dB feedback and totally 3 stages of amplification, voltage amp + phase splitter + output stage.

Mostly low order distorsion products as with normal tube amps, mainly 2nd and 3rd order products.

Disadvantages:

Heat dissipation, for instance in my case I need > 400W for a amp giving 2 x 25W out.

A bit tricky to do as DIY, transformer coupled amps is probably easier for a beginner, also quite more difficult to build high power OTL amps using many parallel connected tubes.


Most commercial OTL amps seems to be quite expensive, for instance Graaf OTL GM-20 has been advertised for ~4600 Euro, it gives 2 x 20W and there is a mono block version of this amp giving 65W for the same price.

Other manufactures are for instance Tenor, Silvaweld. For the DIYer one alternative is the amplifiers from Transcendent Sound, their type T-16 monoblocks giving 40W Model T16 cost $1999 per pair as a kit, maybe it is possible to buy one single unit. http://www.transcendentsound.com/T16OTL.htm

For DIY it can actually be cheaper to build an OTL amp compared to an ordinary transformer coupled amp as an output transformer is not needed and they usually is quite a substantial part of the cost for a tube amp.

For real DIY, (to build from scratch) I can recommend the design by Ciuffoli, see http://www.audiodesignguide.com/my/O...ion_82_ocl.gif

My amp is similar but I have re-designed the driver circuit, see here: http://www2.gol.com/users/tube/otl.html

Regards Hans
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Old 24th March 2003, 08:32 AM   #9
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Default Re: Re: only need one channel

Quote:
Originally posted by Brett
I've often found that a centre is not needed at all, and can mess with the coherency of a good front based system.
This has been my experience, and i avoid them in my system. I haven't seen very many physical set-ups where a center channel doesn't get in the way as compared to a set of speakers that image well.

dave
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Old 24th March 2003, 03:44 PM   #10
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Default protection

hi all
just out of interest, how do you protect you're speakers from a failure in the amp when using otl/
i feel that otl is a way to go as there is less in the signal path ie no tx,put this point has concerned me

rob
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