Dennis Had Inspire Amps

[FloridaBoy]

Originally Posted by decooney

I saw an ad from a guy who sold his QMB-25s and kept his Cary SLI-80 and 807s. Kinda been there already and prefer my SLP-98 pre and V12R amp combo over my former SLI-80, going full circle probably need to leave well enough alone for the big system, and just keep my DH KT150 for the small den room system and pair it up with a smaller and more efficient pair of speakers. I'm no longer into soft/metal dome tweeter speakers or horn speakers. Not my taste. Have owned and built many of them, and prefer AMT/electrostatics type speakers, however as most know who build them it's not easy to get them to sound right above 92db@1w/1m or without good power. Works great in a large system, not so great in a small den room system.

The little DH KT150 HotRod is a cool little amp, and it deserves the right speakers to go with it; have not found or built them yet. Not looking to go overboard for this den room system, and closest I can find so far is the Decware DM945 ribbon type speaker. Still open to ideas anything under $1500/pair if something of real "value" comes to mind, or its back to the drawing board on building a set with di-pole AMTs. Thanks.

Common sense prevails. The Omegas seem a good choice and they can be returned if you R not happy.

[decooney]

Cool...Thanks. You guys have all mentioned both the Omegas and Tektons before, and both seem to have a great following by many on this AA forum.

[decooney]

Originally Posted by straitwire

Hey decooney, if yours is one of the new Triode-strapped KT-150 Hot Rods then asking Dennis for output numbers would be best.
straitwire

straightwire,
spoke to Dennis by messaging. I'm not to able to message you on this forum, blocked. Gotta question. He mentioned the 22w monos you are punching out. Not a lot of details since it's a bit of a test, but I do have a question for the future...

Would two of the current version stereo Inspire KT150 Hot Rod amps (at 10-12 watts per channel) with one amp bi-amped to my speaker woofers on both speakers and the second amp bi-amped to my tweeters on both speakers effectively work and sound the same as a pair of the strapped 22w triode mono block amps? (in either case I'd still be running four KT150s in total. However, I guess the real difference is a pair of my current amps would be stereo amps with four interconnects total, and a pair of the mono blocks would be mono with two interconnects). I just don't know if true mono amps present something more beneficial when comparing to a pair of stereo amps.

[Analog Addict]

Originally Posted by decooney

straightwire,
spoke to Dennis by messaging. I'm not to able to message you on this forum, blocked. Gotta question. He mentioned the 22w monos you are punching out. Not a lot of details since it's a bit of a test, but I do have a question for the future...

Would two of the current version stereo Inspire KT150 Hot Rod amps (at 10-12 watts per channel) with one amp bi-amped to my speaker woofers on both speakers and the second amp bi-amped to my tweeters on both speakers effectively work and sound the same as a pair of the strapped 22w triode mono block amps? (in either case I'd still be running four KT150s in total. However, I guess the real difference is a pair of my current amps would be stereo amps with four interconnects total, and a pair of the mono blocks would be mono with two interconnects). I just don't know if true mono amps present something more beneficial when comparing to a pair of stereo amps.

You may be able to better control the woofers, but IIRC, the majority of your output power is going to the woofers to produce the lowest frequencies. Your best bet is to ask Dennis to give you a quote on a QMB running 6L6s or 6550s. However, I do believe we talked about this very idea at some point, and I think the output transformers he uses are limited to about 25 watts.

Here is the latest offering at the Toy Shop. Dennis is experimenting with a two stage power supply, but I don't know if he thinks it's better than the IIPS. Just another experiment to evaluate.


Untitled by Analog Addict, on Flickr


Here is my newest build, a PSE 71-A triode amp pushing a mighty 2.5 WPC. However, when we looked at it on the bench, Dennis said the square wave is clean up to 5 wpc, giving me 3 db dynamic headroom. Dennis was very complimentary about the sound, and wanted to know if I could leave it at the shop for further testing when I go on my summer vacation.....



Untitled by Analog Addict, on Flickr

Untitled by Analog Addict, on Flickr

[Bombadil]

Originally Posted by decooney

Would two of the current version stereo Inspire KT150 Hot Rod amps (at 10-12 watts per channel) with one amp bi-amped to my speaker woofers on both speakers and the second amp bi-amped to my tweeters on both speakers effectively work and sound the same as a pair of the strapped 22w triode mono block amps? (in either case I'd still be running four KT150s in total. However, I guess the real difference is a pair of my current amps would be stereo amps with four interconnects total, and a pair of the mono blocks would be mono with two interconnects). I just don't know if true mono amps present something more beneficial when comparing to a pair of stereo amps.

I have run my Hot Rod high output Inspire amp with KT120s producing about 17-18 wpc in SEP mode paired with a SS amp in a bi-amp configuration. The SS amp handled up to 200Hz, with those low frequencies being filtered from the signal to the Inspire, so that it never saw them. Had to tinker with volume leveling, as the SS amp was more sensitive. When I got them well balanced, the resultant sound was very good.

I picked 200Hz because that is the crossover to my woofers. Thus the SS amp drove my woofers with the Inspire driving my midrange & tweeter.

In this config, the Inspire had plenty of power to drive my 91dB speakers (well, the mids & tweeters). Relieved of the lower bass power demands, the Inspired sounded more like a 30-40 wpc amp in that I was able to push this amp combo to sound levels where the Inspire alone would have clipped.

IMO, the lower bass was improved in this setup, having more definition and power. To my ears the magic from Dennis' amps happens above 150/200Hz.

One can do almost the same thing by employing a powered subwoofer, setting the crossover to around 80Hz. Again, this works best when you can filter the low bass from the signal going to the Inspire. Some newer preamps can handle this type of thing.

[decooney]

on a similar note, as a test I tried running a Cary SA-200.2 solid state amp (and my Cary V12R tube amp in a 2nd test) for bass up to 1200hz, and the Inspire Triode Hot Rod for my midrange and tweeter range above 1200hz.

While It sped up response a bit to the point where I noticed it lost some of the tube "bloom" with either of the higher power amps just running the woofers. I had no way of backing down and matching outputs to the inspire but it was a fun test.

This started me back down the path of trying a 2nd identical Inspire amp. I can see why you say to use the higher power amp below 200hz or a sub woofer. I can try that next with my sub but using the sub/crossover will likely kill the sound of the Inspire. May try it as a fun test though. Thanks.

[straitwire]

Originally Posted by decooney

straightwire,
spoke to Dennis by messaging. I'm not to able to message you on this forum, blocked. Gotta question. He mentioned the 22w monos you are punching out. Not a lot of details since it's a bit of a test, but I do have a question for the future...

Would two of the current version stereo Inspire KT150 Hot Rod amps (at 10-12 watts per channel) with one amp bi-amped to my speaker woofers on both speakers and the second amp bi-amped to my tweeters on both speakers effectively work and sound the same as a pair of the strapped 22w triode mono block amps? (in either case I'd still be running four KT150s in total. However, I guess the real difference is a pair of my current amps would be stereo amps with four interconnects total, and a pair of the mono blocks would be mono with two interconnects). I just don't know if true mono amps present something more beneficial when comparing to a pair of stereo amps.

Hey decooney, I am not an expert but, stacking two stereo amps (bi-amped) would increase SPL, but if it doesn't sound quite right, getting it right using attenuation, filters, or crossovers can sometimes be a hassle, but if done right, it sounds great IMHO. With a PSE (two output tubes per channel) you have doubled the power and halved the output transformers impedance (fewer winding's) so you get better speaker driver control which improves overall dynamics as well as low frequency control, meaning stronger, tighter bass, then if you take the PSE circuit and build it in mono block configuration you have completely separated the two channels power supplies and input stages, this generally makes the sound stage even larger and improves detail and positioning of instruments in the sound stage. The PSE mono blocks I am cutting chassis's for are built on the same size chassis as the FireBottle you have now. And the stereo PSE's are wired in Pentode, I do not know if Dennis is wiring these mono block PSE's in Triode or Pentode though. hope this helps you...straitwire

[Bombadil]

Originally Posted by decooney

I can see why you say to use the higher power amp below 200hz or a sub woofer. I can try that next with my sub but using the sub/crossover will likely kill the sound of the Inspire. May try it as a fun test though. Thanks.

Running just the lower bass through a SS amp didn't "kill" the sound of my Inspire amp at all. IMO the lower bass is a weakness in tube SE amps. Tough to get enough power or definition. If anything, I felt my Inspire sounded better after filtering the lower frequencies from it.

This was particularly true for my baby Inspire, an EL84 amp which produces only about 4 wpc. Lower bass was flabby and woefully weak. But when paired with a subwoofer cutting in at 100Hz and filtering sub-100Hz from the Inspire, that amp came alive. Much better dynamics, more "air" around instruments, even vocals sounded more lifelike.

[decooney]

Originally Posted by Bombadil

Running just the lower bass through a SS amp didn't "kill" the sound of my Inspire amp at all. IMO the lower bass is a weakness in tube SE amps. Tough to get enough power or definition. If anything, I felt my Inspire sounded better after filtering the lower frequencies from it.

This was particularly true for my baby Inspire, an EL84 amp which produces only about 4 wpc. Lower bass was flabby and woefully weak. But when paired with a subwoofer cutting in at 100Hz and filtering sub-100Hz from the Inspire, that amp came alive. Much better dynamics, more "air" around instruments, even vocals sounded more lifelike.

Sure, makes sense. I'm assuming you have a much better crossover option and idea than I do of course. I'm guessing you are talking about using an active crossover vs. a passive one for dividing signal for the main speakers, correct?

In my case, I don't have a very good electronic crossover and/or using the internal active crossover in my active subwoofer amp to divide duties would likely kill the sound quality of the Inspire bit (in my system). I know some are using DSP, not my thing. Hehe, the idea of going from a nice source and nice interconnects to a lower quality crossover inside my subwoofer amps and back through nice interconnects over to the inspire makes me feel ill, but maybe that's just me. I'll tr it and see though. Agree, the light weight amps don't produce the same bass, and i do mix in my subwoofer some times for times when added oomph is needed

[Bombadil]

In the case of integrating a powered subwoofer into a system, no active crossover is needed. I do have a preamp which has built-in filters which I can set to filter out low frequencies from being sent to a power amp.

In my other setup, where my woofer crossover is set at 200Hz, I do not use an active crossover. I know that is preferred by many however the person who designed my speakers strongly advises against it. The passive crossovers are very complex and employ elements which smooth the impedance curve and affect output too. Removing them would totally change the sound of the speaker and an active crossover would not be capable of compensating.

For example the crossovers result in the woofer module having a nearly flat 4 ohm impedance, while the mid/tweeters are a nearly flat 8 ohms. I think the Inspire is happier driving that smooth 8 ohm load.

So I leave the passive crossovers in place. Having the one crossover set at 200Hz is almost perfect to integrate the SS amp, leaving the all important 200-2000 range (and up to 20Khz) for the Inspire. If my lower crossover were higher, I'd be restricted to using a powered subwoofer or trying to use an active crossover in front of the passive crossovers.

My speakers are an older set of Von Schweikerts which were upgraded to the VR-7 model. The most current offering in this line ultimately sold for $22K/pr, although mine aren't the equals of that last version.