Dennis Had Inspire Amps

[Bombadil]

Originally Posted by Musica Amantem

Bombadil: "I find that a well-integrated subwoofer can add a nice deep bass balance."

I used to do that, but a SUB that merely reinforces the full range does not have the same effect. Replacing those lower frequencies with the SUB alone, and allowing the amp to work everything else out without that burden, makes a tangible difference. I strongly suggest you try that filtering approach.

That's what I do with my Inspire SE EL84 amp. It's deeper bass output is simply terrible and it clips at low volume on sub-80Hz notes. I have a preamp with a bass filter and a subwoofer output. I filter all sub-120Hz going to the amp.

With the filter in place, the amp is much happier. It sounds better and can play at significantly higher volumes. A night and day difference.

[FloridaBoy]

Originally Posted by Wgarcia

I run 2 REL subs from the same era…a Q150e 10", and a Q108e MKII 8"…and since they utilize the amp's output it would seem there's plenty of bass generated by the Fire Bottle. Without the subs my mains are fairly flat to around 40hz (Sonist Recital 3s) and the amp gets to that area just fine, but with the subs it's sublime (sorry).

Another Enabler!

[Wgarcia]

I can't imagine why an EL34 based Inspire would distort low frequencies to the extent noted, but then I don't get out much. I'm currently rolling various tubes from my "tube museum" I've wound up with (not THAT many…at least compared to the tube extremists around here), and the most recent are a pair of Sovtek KT88s from a quad I've barely used…and they sound GREAT…must be accidental as they're inexpensive (and discontinued) and a couple of them are sort of rusty around the top of the base which adds to their charm. (!) My Inspire sort of lives up to Had's hype ("Like a 50 watter"…man…) and seems to be clear as a bell at all frequencies demanded of it, even though my mains are a not so extreme at 93db efficient…the subs (I bought the second one to stick in a nearby window sometimes for deck listening, but otherwise it adds to my original Q150 in normal duty) add that "room charging" atmosphere that makes things right somehow, and only require dusting and level tweaking here and there.

[Musica Amantem]

Originally Posted by Bombadil

That's what I do with my Inspire SE EL84 amp. It's deeper bass output is simply terrible and it clips at low volume on sub-80Hz notes. I have a preamp with a bass filter and a subwoofer output. I filter all sub-120Hz going to the amp.

With the filter in place, the amp is much happier. It sounds better and can play at significantly higher volumes. A night and day difference.

I see. That's the way to go .

I'll be trying the larger tubes (6550 / KT-88) with the filters this weekend. I don't expect as much benefit with those, but who knows. Hopefully their over-boldness from the PRE's boost in the signal path will be reduced by not having to deal with those first 100 Hz.

[Musica Amantem]

Originally Posted by Wgarcia

I can't imagine why an EL34 based Inspire would distort low frequencies to the extent noted, but then I don't get out much. I'm currently rolling various tubes from my "tube museum" I've wound up with (not THAT many…at least compared to the tube extremists around here), and the most recent are a pair of Sovtek KT88s from a quad I've barely used…and they sound GREAT…must be accidental as they're inexpensive (and discontinued) and a couple of them are sort of rusty around the top of the base which adds to their charm. (!) My Inspire sort of lives up to Had's hype ("Like a 50 watter"…man…) and seems to be clear as a bell at all frequencies demanded of it, even though my mains are a not so extreme at 93db efficient…the subs (I bought the second one to stick in a nearby window sometimes for deck listening, but otherwise it adds to my original Q150 in normal duty) add that "room charging" atmosphere that makes things right somehow, and only require dusting and level tweaking here and there.

I believe Bombadil's observation refers to an EL84, not an EL34, which is a larger, more robust tube (70 mA at 250 V in Triode).

[Bombadil]

Yes, I was referring to Dennis' old line of EL84-based amps, which were based off of old single-ended Magnavox console amps. Unfortunately he used very small output transformers, much like the old Magnavox amps. They have a -3 dB point of 82Hz. The EL84 tube can go much lower than that, in the right amp.

But these low-powered amps can sound very good with the low bass filtered off to a sub and with decent efficiency speakers. They were surprisingly loud with 90dB bookshelf speakers. A single-ended EL84 has a very nice tone.

[Bombadil]

Here is a Magnavox 196 single-ended EL84 amp
https://c2.staticflickr.com/2/1684/2...595b73dd_b.jpg

Here is an Inspire single-ended EL84 amp
http://img.canuckaudiomart.com/uploa...b50b212358.png

[Rosco65]

Originally Posted by Bombadil

Yes, I was referring to Dennis' old line of EL84-based amps, which were based off of old single-ended Magnavox console amps. Unfortunately he used very small output transformers, much like the old Magnavox amps. They have a -3 dB point of 82Hz. The EL84 tube can go much lower than that, in the right amp.

But these low-powered amps can sound very good with the low bass filtered off to a sub and with decent efficiency speakers. They were surprisingly loud with 90dB bookshelf speakers. A single-ended EL84 has a very nice tone.

I've made this observation before. The early Inspire amps were essentially scratch-built versions of Magnavox console amps. In contrast, the Decware SE84 amps use a much bigger output transformer that can deliver bass. I have a pair of EL84 adapters to use in my KT88HO amp. Using the larger (15 watt) transformers the EL84 produces adequate bass when used into efficient speakers.

[FloridaBoy]

I bought one of these and will set it up tomorrow. Fingers crossed. I'm in. There is a thread here. Long but not as long as the Inspire.

https://www.audioaficionado.org/showthread.php?t=25096

[Musica Amantem]

Originally Posted by FloridaBoy

I bought one of these and will set it up tomorrow. Fingers crossed. I'm in. There is a thread here. Long but not as long as the Inspire.

https://www.audioaficionado.org/showthread.php?t=25096

Congrats! Let us know how it performs. Happy listening!