Dennis Had Inspire Amps

[ismelllikepoop]

kinda dumb question, but how are you supposed to figure out what tubes are good or bad? and anyone know anything about the el84 model i posted? Finally got it fired up with some devore gibbon 8's. Was worried about it but sounds fantastic.

[SteveSem]

Originally Posted by ismelllikepoop

kinda dumb question, but how are you supposed to figure out what tubes are good or bad? and anyone know anything about the el84 model i posted? Finally got it fired up with some devore gibbon 8's. Was worried about it but sounds fantastic.

Do you mean which ones sound good or bad? Whether they are good or bad from the perspective of working with a particular amp? Or whether the tubes are performing well or failing?

If it's the first, this thread contains tons and tons of annecdotal opinions about various types of tubes and how they sound in different combinations. It's definitely a subjective process. But I've found the opinions of others to be very helpful.

[ismelllikepoop]

meant which ones are failing. the seller i got the amps from is very unresponsive, even left out of the power cables and ended up getting a wireworld. No idea how many hours are on the tubes, so going to re-tube sooner rather than later.

[robert_kc]

Pstrisik and jdandy: Thanks for your warm welcome!

Originally Posted by pstrisik

I love the copper color.

I agree. When I saw it I debated with myself whether or not I needed another amp … for about 2 minutes … then I hit the “Buy It Now” button …

Originally Posted by pstrisik

I'm also curious what he will say about tube possibilities in a SET that runs pentode power tubes. Maybe the same options as the SEP's, ie, almost infinite! Or maybe the SET wiring makes for more limited options.

I’m anxious to try different tubes, once I receive Dennis’ compatibility chart. Generally with PP amps I find that the front end tubes make the biggest difference, but apparently with this amp more than one type of output tube is supported, so the sound might change noticeably with a different type of output. While I imagine that Dennis has chosen the tubes for this amp carefully, all speakers are different, and so it will be interesting to experiment to find what works best in my systems.

Originally Posted by pstrisik

If you are running it with Klipsch speakers, you have some advantage in gain as they are typically 100db+ aren't they?

Sensitivity ratings are:

• Klipsch RF-7: 101
• Klipsch Palladium P-37F: 96
• Snell Type CV: 90
• JBL L880: 91

None of my rooms are very large, and I don’t listen at very loud sound levels. Bottom line, none of these speakers are as sensitive as Klipschorn (105), but none are difficult to drive. (I also have a Klipsch WF-35 in my bedroom system, but that’s a mono system.)

Originally Posted by pstrisik

But evidently you are still needing more for classical.

Yes, with some classical recordings I need more volume. (Some recordings of string quartets are loud enough without a pre-amp. Most large scale orchestral music is not loud enough without a preamp.)

Originally Posted by pstrisik

If you are running without a pre, do you have a passive attenuator? How are you controlling volume?

My Oppo universal players (BDP-105, BDP-95, Oppo DV-980H) have variable output, controlled via their remote control. They are able to drive my other power amps (McIntosh MC240, McIntosh MC30 x 2, McIntosh MC275, Pilot SA-260, Scott LK150) satisfactorily without a preamp, except when tonal adjustment is needed (which for some amp/speaker combinations is always, for others: never, and for others it depends on the recording.)

The Inspire KT88 sounds great driven directly by my Oppo player (no preamp) when playing pop music. (I don’t know if Eva Cassidy CDs have ever sounded better than Oppo -> Inspire KT88 -> Klipsch RF-7.) On the other hand, for some classical music a pre-amp is needed for additional gain. And, candidly, large scale orchestral music often sounds better with more power (e.g., Oppo -> McIntosh MX110Z -> Scott LK150 (PP KT88s) -> Klipsch RF-7 vs. Oppo -> Inspire KT88 -> Klipsch RF-7).

I’m anxious to see if a different front-end tube in the Inspire KT-88 will provide a significant increase in gain. And if not, I’m still glad to own the Inspire KT-88.

Again, I’m interested in others’ findings regarding tube rolling. This winter I intend to work my way through my systems, tube rolling the Inspire KT-88, and comparing it with my McIntosh, Fisher, Scott, Pilot, and Altec PP tube amps (both power amps and integrated).

[nhparrot]

Originally Posted by ismelllikepoop

meant which ones are failing. the seller i got the amps from is very unresponsive, even left out of the power cables and ended up getting a wireworld. No idea how many hours are on the tubes, so going to re-tube sooner rather than later.

If you know someone with a tube tester or a tube testing service in your area you can get the tubes tested to find out their state.

[Masterlu]

robert_kc... Welcome to AA!

[BearCityUSA]

Originally Posted by ismelllikepoop

meant which ones are failing. the seller i got the amps from is very unresponsive, even left out of the power cables and ended up getting a wireworld. No idea how many hours are on the tubes, so going to re-tube sooner rather than later.

After inquiring around my smallish city I came up blank on finding someone with a tester. I ended up getting a Sencor tester from Brent Jessie. A little more expensive than a similar model on eBay but he checks them out and calibrates them. I thought I might use it a few times. I have it out all the time as I am buying and rolling tubes. Well worth the $.

BTW he is offering 2 year guarantee on tubes for a modest up charge now. Also well worth it IMHO.

Scott

[jscottyk]

Originally Posted by robert_kc

Greetings. I’m new to this forum. I recently acquired from Dennis Had an Inspire “Fire Bottle” SE Stereo Tube Amplifier HO, built in Oct 2015, and finished in copper color:

INSPIRE TUBE AMPLIFIER by DENNIS HAD FEATURING THE KT-88/6550 BEAM POWER VACUUM TUBE AMPLIFIER IN A SINGLE-ENDED CLASS A SET TRIODE DESIGN

• CLASS A, 8 WATT, ZERO-FEEDBACK TRIODE
• KT-88 GENALEX OUTPUT TUBES
• 6CG7 NOS INPUT DRIVER
• 5U4 Shuguang RECTIFIER TUBE
• REGULATED DC, B+ VOLTAGE ON DRIVER TUBE
• REGULATED DC POSITIVE CATHODE BIAS ON DRIVER TUBE
• CUSTOM DESIGNED AIR-GAP 15 WATT OUTPUT TRANSFORMERS TO MATCH KT-88 TUBES IN THE TRIODE MODE

Hello Robert. Looks like we have the same spec Firebottle. Mine was built in early November 2015. If I understand correctly from Dennis's comments, he is settling in to a couple different models and that this was one of them.

[jscottyk]

Originally Posted by robert_kc

I’m anxious to try different tubes, once I receive Dennis’ compatibility chart. Generally with PP amps I find that the front end tubes make the biggest difference, but apparently with this amp more than one type of output tube is supported, so the sound might change noticeably with a different type of output. While I imagine that Dennis has chosen the tubes for this amp carefully, all speakers are different, and so it will be interesting to experiment to find what works best in my systems.

Sounds like that chart will be here soon! Looking forward to trying a KT150 and a 5AR4 rectifier of some sort. I think for our units that will yield 10 watts per channel with that setup.

My speakers are currently HSU HB-1 Mk2 and while they sound great, I think they are just efficient enough for my taste. These speakers are listed as 92db efficiency. Like you I am connected directly to the amp from my DAD (a Bel Canto DAC3) and using it's volume control. The DAC3 has a dynamic range of 125 dB. I had not considered using an additional preamp but that is interesting to consider.

[FloridaBoy]

Originally Posted by pstrisik

Beautiful amp - congratulations and welcome to the club! I love the copper color.

I'm curious about his SET wiring. I have a similar amp, but it is wired as SEP.

I have 93db speakers (single driver Omega Alnico Monitors) and need a preamp for sufficient gain. The obvious option is to get a matching Inspire preamp from Dennis. The cost is reasonable. My LP-2 is top notch. I used to have the Cary SLP-05 (one of Dennis' earlier designs that won awards). When I got the amp, I got the pre so I would have the matching set. I went back and forth between the Inspire and Cary preamps trying to hear the Cary as sounding better since it cost me five times as much as the LP-2 (about 9 times the price at MSRP!). I sold the Cary.

I'm also curious what he will say about tube possibilities in a SET that runs pentode power tubes. Maybe the same options as the SEP's, ie, almost infinite! Or maybe the SET wiring makes for more limited options.
If you are running it with Klipsch speakers, you have some advantage in gain as they are typically 100db+ aren't they? But evidently you are still needing more for classical. If you are running without a pre, do you have a passive attenuator? How are you controlling volume?

If ok to run in your amp, the 5AR4 or 5Z4 rectifiers are low voltage drop and may help hold the dynamics more (if I understand correctly how that works in operation).

Peter, all of the Inspire amp are single ended pentodes SEP. They can be wired
in triode but will then be pentodes that are triode wired.

SET amps use Triode output tubes. 45, 2A3, 300B are triode output tubes.

The best way to get more gain and drive is with a preamp.