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Inspire by Dennis Had Enjoying Vacuum Tube Audio

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  #2141  
Old 08-28-2016, 08:48 AM
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BearCityUSA BearCityUSA is offline
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Originally Posted by Rosco65 View Post
Is the LP-3 an octal version of the LP-27a, or is the circuit different? I understand that the LP-3 has three 6SN7/6SL7 tubes. However the 6**7 types are double triodes, where the 27/56 tubes in the LP-27a are single triodes. Is Dennis simply running 1/2 of two of the tubes?
I don't think it is. I was inquiring with Dennis about the difference recently and he put it this way. He designed the lip-3a as a response to some buyers with stashes of 6**7s who wanted one of his preamps. He still feels the lip-27a is for the real tube enthusiast and a real gem of a unit but not really for the tube newbee. A little finicky dealing with antique tubes but worth it if you have the patience.

I get the feeling that the lip-3a in the upgraded version of the lip-2. The lip-27a is a whole different animal.
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  #2142  
Old 08-28-2016, 09:28 AM
Rosco65 Rosco65 is offline
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That makes sense. The 3 6FM7's in the LP-2 are the equivalent of 3 6SN7's and 3 6SL7's. I don't have the circuit, but my instincts tell me that two of the three tubes are shared by both channels. This could be easily changed by subbing in a pair of 6SN7's and one 6SL7 (or vice versa). The sockets would have to be rewired, but would appear to have the benefit of being closer to a dual mono layout. It still gives one additional stage compared to the LP-27a, but maybe that is beneficial and maybe not.

I don't find the LP-27a to be finicky, but from a long-term perspective it is probably best to limit the market for something relying on antique tubes. I get the impression that Dennis started his retirement business as a hobby, but that demand and his natural business instincts have turned it into a cottage business. As such, we can see an evolution of his designs. Casework has gotten better, and he appears to be moving toward using tubes that are in current production rather than cheap, overlooked vintage tubes (e.g., 6FM7 and 6GC7). He's also sensing the desire for higher performance passive components (capacitors) and has been slowly moving the Inspire line upmarket. All of these are the marks of a businessman creating a sustainable model.

That being said, I've laid in my own stash of 80 rectifiers, 27 and 56 tubes. They are cheap enough and if I ever sell the LP-27a they will add value to the sale.
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  #2143  
Old 08-28-2016, 09:41 AM
FloridaBoy FloridaBoy is offline
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Originally Posted by Rosco65 View Post
My KT-88HO shipped with a 6DJ8 type. I purchased it January 20, 2016. I think maybe a couple of months later he switch to an octal driver tube. I asked him about this, and his reply was: "The circuit is very similar except for the bias values on the 6SN7 driver on the front end of the KT88 HO. The 6SN7 has a bit more dynamic drive. You may give the 6CG7 a whirl in your amplifier. Similar to a 6SN7 except for the different bias on the 6SN7 driver."

This is interesting, since your amp came supplied with a 6CG7, which is a 6SN7 in a 9-pin bottle. His implication that they would be biased differently puzzles me.

I do know his KT88 amp is now $45 more expensive, and that may reflect a higher parts cost. It also appears that as his amps (and preamps) are becoming more popular he is going a little more upmarket. IIRC, Inspire started as a kitchen table retirement hobby business, originally revamping Magnavox console amps and later producing his own adaptation of the circuit. His metalwork has improved and he now uses higher end passive components. Both Cary Audio and AES exclusively used octal tubes, at least I don't recall seeing 9-pin tubes except as the output buffer in the PH-1 phono stage. It could be that he's switching based on the higher perceived quality of the octal tubes.

That being said, there appear to be a lot more options for affordable tube-rolling with 6SN7's. 6CG7's weren't made by many manufacturers and the best 6DJ8 types have gotten expensive (and frankly was not even designed as an audio tube to begin with). It seems like it is harder to find a good sounding 6DJ8 than a good sounding 6SN7. 6CG7's are electrically identical to 6SN7's but with the elements closer together in the smaller bottle there are potential compromises.

When I saw Dennis had moved to a 6SN7 right after I bought my amp I was disappointed. My options are to use what I have (and am currently happy with), preferably with a 6CG7, send it back to him to get converted to an octal socket, sell it (I have a number of amps), or buy a socket adapter to use a 6SN7. I may do the last anyway just to see how things sound.

I rather think it depends on what he feels like or is making today. I'd been watching these amps for a while and e-mailed him last year and attached a link to a KT88 amp. He responded with 'you have to get the amp I am just finishing'. SE triode wired 20 watt tranny's...so I did. He did use a UX4 rectifier
socket for 5Z3/type 80 tubes. Not sure why he chose those rectifiers. No regrets.

I believe that once you find the tube compliment that works best your rig you will have excellent sound with these amps. There is always some other amp etc. to wonder about...I am trying to resist.

Last edited by FloridaBoy; 08-28-2016 at 01:25 PM.
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  #2144  
Old 08-28-2016, 10:10 AM
Rosco65 Rosco65 is offline
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Originally Posted by FloridaBoy View Post

I believe that once you find the tube compliment that works best your rig you will have excellent sound in these amps. There is always some other amp etc. to wonder about...I am trying to resist.
I'm in the same boat. I have an LP-27a, KT-88HO (15 watt, 9-pin), and am about to receive a PSE amp. I also have a custom-built 4 watt 421a SE amp, two pair of Omega single-driver loudspeakers and a custom Altec 414/802/32A speaker. I have three very good dacs and a middle of the road TT. This is aside from vintage solid state rig and a pretty good HT rig. I officially have more equipment than I can accommodate but have to resist the urge to find something "better".
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  #2145  
Old 08-28-2016, 12:56 PM
CoGT3 CoGT3 is offline
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Quote:
Originally Posted by Rosco65 View Post
I don't find the LP-27a to be finicky, but from a long-term perspective it is probably best to limit the market for something relying on antique tubes. I get the impression that Dennis started his retirement business as a hobby, but that demand and his natural business instincts have turned it into a cottage business. As such, we can see an evolution of his designs. Casework has gotten better, and he appears to be moving toward using tubes that are in current production rather than cheap, overlooked vintage tubes (e.g., 6FM7 and 6GC7).
Think you nailed regarding the shift in tubes used. He shipped my 45 SET with the "tung sol" 6sl7gt. When I asked about rolling he implied the new production tube was awfully good but there where gains to be had at a $$$ and depending on preference. That may be the shift toward 6xx7s. When he wasn't making that many amps it probably wasn't too hard to track down NOS drivers,but the volume he is now making that has to be harder. He has already made it very clear how good he thinks the Russian GL KT88s are, especially compared to the price of admission for NOS output tubes. At least for the amps, you only need 1 6xx7 for rolling tubes isn't that expensive. Glad the PSE is using the 6xx7 driver also, will be picking one up to compliment the 45 SET when the timing is right.
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  #2146  
Old 08-28-2016, 01:29 PM
Bombadil Bombadil is offline
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Quote:
Originally Posted by FloridaBoy View Post
I rather think it depends on what he feels like or is making today. I'd been watching these amps for a while and e-mailed him last year and attached a link to a KT88 amp. He responded with 'you have to get the amp I am just finishing'. SE triode wired 20 watt tranny's...so I did. He did use a UX4 rectifier
socket for 5Z3/type 80 tubes. Not sure why he chose those rectifiers. No regrets.
He does just whip them together. Frequent changes. He built my amp in May, but when I communicated with him, he needed pictures of the underside of it in order to know what he did with it.

Mine has the 20 watt output transformers, but is pentode wired to produce 17 wpc with KT88. Standard tube set of KT88, 6SN7, and 5AR4/GZ34 rectifier. I mix/match several output tube types and rectifiers, but always stay with 6SN7 driver tubes. Was told that if I use 5U4G rectifiers that I will get 15 wpc with KT88.
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  #2147  
Old 08-28-2016, 01:45 PM
FloridaBoy FloridaBoy is offline
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Rosco,

I had a respected dealer tell me that the chase ends when you say so.

Forums can induce audio nervosa. Imagine that ?

Personally, I'm done with gear and to get the most out of what I have I need to work on the room.

I have had 'better' gear but the price to performance ratio of the Inspire combo
is IMHO unbeatable. I'm just enjoying music again.
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  #2148  
Old 08-28-2016, 01:47 PM
FloridaBoy FloridaBoy is offline
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Originally Posted by Bombadil View Post
He does just whip them together. Frequent changes. He built my amp in May, but when I communicated with him, he needed pictures of the underside of it in order to know what he did with it.

Mine has the 20 watt output transformers, but is pentode wired to produce 17 wpc with KT88. Standard tube set of KT88, 6SN7, and 5AR4/GZ34 rectifier. I mix/match several output tube types and rectifiers, but always stay with 6SN7 driver tubes. Was told that if I use 5U4G rectifiers that I will get 15 wpc with KT88.
Yeah, the chef whips something new up all the time..different..but all good
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  #2149  
Old 08-28-2016, 02:13 PM
FloridaBoy FloridaBoy is offline
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Default FWIW: Pure Audio i20 dock

I bought one of these 5 years ago. It's still $99 and the best bang for the buck
audio toy I've ever had. It only works with Apple. Presently, I'm using my old iPhone 4s as a dedicated source. It sounds extremely good and uses standard RCA IC's. I use Spotify and Tune In Radio.

Excerpt from a review comparing to a Wadia unit from 2011:

Having said that I decided to take out the Wadia and connect the Pure i20. Since the i20 has a far more superior DAC (the Wadia uses a standard Sigma Tel 16-bit DAC) and is actually a pure digital interface, I would expect virtually no floor noise. Using interconnects provided by Moon Audio (Silver Dragon), as I figured, no floor noise on the analog stage while connecting into the digital portion to the Little Dot DAC am using a SEAS coaxial digital interconnect with WBT RCA locking connectors. Using a 4th generation iPod touch with IOS-4 and the application FLAC Player and the source material purchased from HD-Tracks, I was able to test both the analog output stage and digital transport feature of the Pure i20. Treating the Pure i20 as a player I have noticed that when playing the FLAC files (24-bit at 96-KHz) the sound stage was very three-dimensional. Very musical with virtually no jitter artifacts. This is quite an impressive feat for a digital dock costing half the price of the Wadia. Appearances though, the Wadia defeats the Pure, but I only care about music reproduction and without any modification, the Pure i20 does a much better job. It will not rival the Krell KID, but for those who are seeking a great listening experience, then by all means go for the Pure i20 over the Wadia.
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  #2150  
Old 08-28-2016, 02:26 PM
Musica Amantem Musica Amantem is offline
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So many Inspire design alternatives makes me wonder if, in the end, it is worth it. This can be interpreted as if all the multiple configurations end up sounding basically the same, turning emphasis to complementing sound quality areas in our systems.

Once you get an Inspire design, preamp and amp, focus on the other most essential areas for significant improvement:

Room conditions,
Quality of the source and
Quality and characteristics of the loudspeakers/Subwoofers.

Dialing-up our particular unit versions with the right tube combinations should do it in the amplification department. I know I had tremendous benefits by upgrading DAC and implementing diffusors. Otherwise, it becomes as the 'detergent of the month' (super!, new!, improved!, etc.)

YMMV

Last edited by Musica Amantem; 08-28-2016 at 03:11 PM.
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