AudioAficionado.org - Dennis Had Inspire Amps

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- Inspire by Dennis Had (https://www.audioaficionado.org/forumdisplay.php?f=184)

- - Dennis Had Inspire Amps (https://www.audioaficionado.org/showthread.php?t=24170)

Rosco65 " ... Running the amp this easy may allow it to run in a more linear region."

I agree totally and is a factor I was missing in my assessment. Good point. Less is not necessarily better (so much for the 'purist' approach)

Rosco65 " ... As far as a 45 SET, I think it is one of the best tube ever (along with the VT52 and 50) but requires your to accept certain compromises: your speakers with need to be extremely efficient to satisfactorily fill larger spaces, very efficient (>93dB) when used in the near field or in smaller spaces, and in both cases you may want or need active bass support depending on your expectations."

My speakers are 98 dB sensitive at 8 Ohms, used in a near-field setting. No horns for me, as these have a tendency to distort or over-emphasize certain frequency bands. I don't need them in my smallish listening room configuration. Dennis's 45 SET seems, in paper at least, to bring out what I like from his work, to another level. Until Dennis goes the 2A3 or other true-Triode design way, I believe the 45 SET is his best offering within the aforementioned restrictions. I also use a SUB (maybe two in the future) to assist the amp and get deeper bass, so that is not an issue for me either.

Rosco65 " ...Shindo Audio offers a number of configurations: PP, PSE, SE using both triode and pentode tubes, though not triode-connected pentode to my knowledge. Each of these amplifiers is magical in its own way, and none can be said to be absolutely better than the other, only different and inevitably appealing to different musical tastes."

Although it is true there are exceptions by extraordinarily successful designs, the general concepts are important to consider when attempting to sort out the amp of your choice without the benefit of listening to them at home, in your settings. I can't afford those fancy brands ... But you're right about their quality. The best example is Audio Note's (UK) Ongaku integrated amplifier using single 211 tubes, at USD 95,000.00.

Rosco65 " ...I've found that speakers with highish impedance and minimal crossovers work well. I have personal experience with Cabasse (older DIY models of 94 dB sensitivity) and various Omega speakers"

The best drivers Louis Chocho has produced to date are the Alnico-based 6" used in his super monitors and some XRL floorstanding designs. Unfortunately, at just 93 dB sensitivity these don't cut the mustard. His cabinet designs are nothing special either, in my view. Besides, I can't stand the man's ego.

You raise good points and I thank you for the insights.

What speakers are you using, to satisfy my own curiosity?

My experiences with Louis have been positive, though ego and hyperbole are almost to be expected in this hobby where boutique builders tell people that their product is subjectively better than others. His most expensive driver is the 6" Alnico, but it may not necessarily be his best depending on application and need. I have both the 6" Alnico and the latest 4" ceramic. Both are great, but the 4" really excels from the upper bass to treble. It reminds me of old very high quality cone midrange and tweeters drivers. I find it works best in smaller enclosures when supported by a subwoofer. Both of these drivers are 94-95dB (depending on how you measure).

Horns can be problematic, but they can also be fantastic. Again, it is a matter of implementation with the understanding that sometimes you get what you pay for. There are a lot of cheap horn products designed for PA applications that have been pressed into service in domestic hifi. I don't know of anyone who would look at a properly implemented Altec horn system and say that it distorts or overemphasizes anything. The key is to match the implementation to your application. Since many horn systems were design to fill large spaces, getting them to integrate in the domestic environment can be a challenge. At the very least it usually requires adapting the crossover and almost as often requires ruling out certain horns altogether (such as the Altec 511 or 811, which don't really like to play in a small room).

I think you'll like your 45 amp if you operate within its comfort zone. I'm interested to see Dennis' configuration for this amp. The most commonly used - and very highly regarded - circuit for the 45 amp is Jeff Korneff's design, which is capacitor-coupled using a 5U4, 2 6SN7's and 2 45's. I get the feeling Dennis' amp will be similar (maybe with a different power supply and shared 6SN7, which would make a preamp preferred).

[quote=Rosco65;801712]What speakers are you using, to satisfy my own curiosity?

Tekton Lore 2.0 with Clarity Caps and Decware DM945 with Mundorf Supreme Caps

My experiences with Louis have been positive, though ego and hyperbole are almost to be expected in this hobby where boutique builders tell people that their product is subjectively better than others. His most expensive driver is the 6" Alnico, but it may not necessarily be his best depending on application and need. I have both the 6" Alnico and the latest 4" ceramic. Both are great, but the 4" really excels from the upper bass to treble. It reminds me of old very high quality cone midrange and tweeters drivers. I find it works best in smaller enclosures when supported by a subwoofer. Both of these drivers are 94-95dB (depending on how you measure).

Do you mean the RS5 4.5" drivers he uses in the 3 series models? Those are faster and detailed but may lack some body/weight due to the smallish cone size?.

Horns can be problematic, but they can also be fantastic. Again, it is a matter of implementation with the understanding that sometimes you get what you pay for. There are a lot of cheap horn products designed for PA applications that have been pressed into service in domestic hifi. I don't know of anyone who would look at a properly implemented Altec horn system and say that it distorts or overemphasizes anything. The key is to match the implementation to your application. Since many horn systems were design to fill large spaces, getting them to integrate in the domestic environment can be a challenge. At the very least it usually requires adapting the crossover and almost as often requires ruling out certain horns altogether (such as the Altec 511 or 811, which don't really like to play in a small room).

I'm sure Altecs are fine, I just don't see the need to go over that route in my setup

I think you'll like your 45 amp if you operate within its comfort zone. I'm interested to see Dennis' configuration for this amp. The most commonly used - and very highly regarded - circuit for the 45 amp is Jeff Korneff's design, which is capacitor-coupled using a 5U4, 2 6SN7's and 2 45's. I get the feeling Denni's amp will be similar (maybe with a different power supply and shared 6SN7, which would make a preamp preferred).

He offered me his first unit from his recent comeback to 45 SET's, by the end of last year, at USD 1,700.00 plus shipping. Tempting price! He said at the time this would take me all the way into sound quality (I had recently bought the KT 88, oversized transformers version, SE in Triode configuration amp and his LP 27a Preamp). I was not ready to take him up on his offer but have ever since considered it a future acquisition to complement my other Inspire gear. This of course was before he came out with the PSE designs.
/quote]

Quote:

Originally Posted by Rosco65 (Post 801639)

I'm not sure I 100% agree with your position. The special output transformers Dennis implies are necessary for PSE may also be in part responsible for the improved performance of the PSE specifically because they are special, just as the 20w transformers in the higher output KT88 amp may be responsible for its reported improved performance over the standard version. The quality of output transformers has a lot to do with sound quality (in PP and SE), and in a typical SE amp comprise the major cost (look up the price of Lundahl, Magnequest, Tango, Tamura, Electraprint, or Hashimoto outputs).

Dennis has his transformers wound to his specs locally. I got that straight from him.

The PSE also allows for a lower impedance, theoretically allowing for greater control of bass drivers. Dennis also implies that the amp sounds best operating at less than maximum power, preferring either the 5U4/KT88 at 15 watts or - preferably - 5U4/6V6 at 10 watts. Running the amp this easy may allow it to run in a more linear region. To put this in perspective, getting more than 10 watts from a single tube in SE requires cranking a KT88 pretty hard. This may sound great in a different way but perhaps not the best it can. To get 17 watts from a single KT88 requires running it at maximum output. For most of us with speakers with sensitivity less than 95dB, a linear 10 watt 6V6 PSE may be much better than a 5 watt 6V6 SE (equal to a 3dB difference) depending on room and musical tastes.

+1 on the above, especially if the speakers are below 90db with less than flat impedance.

Now, as to true SET's, I didn't say that a 45 is the best compromise among SET's. In fact, the 45 is probably the lowest power common SET and has a reputation of "highlighting" the music, especially in the upper registers. It can be dynamic, but needs to be appropriately matched with the right speakers, usually horns of >100dB. In contrast, the 300B has a more typical rounded triode sound (in typical applications), but outputs an 8wpc that is usable by many speakers of 90dB sensitivity or more. The most common compromise between these two is the 2A3, with a 3.5 watt output. Another compromise, albeit less common (with tubes out of production) is a 421a/5998 amp (though this tube is indirectly heated, which can make it quieter) which gives about 4.5 wpc and leans more to the 45 side than 300B side. This doesn't count European tubes such as the AD1 which are beyond my knowledge and experience. In any case, to get more than 8-10 watts requires us to either parallel the triodes or go to transmitting tubes (845, 211) that run at much higher voltage and have much more complicated power supplies and circuits.

I don't think that a triode-connected pentode is better than a true DHT, but it can sound great in the right circumstances (the Decware SE84 triode connected EL84 punches way above its weight class). I also don't think that getting into the pentode/triode-connected pentode/DHT dogmatic argument is all that productive. There are legendary amps - both PP and SE - that use all tube configurations to deliver world-class sound. Each may have a different character but the end result is great musical reproduction. Shindo Audio offers a number of configurations: PP, PSE, SE using both triode and pentode tubes, though not triode-connected pentode to my knowledge. Each of these amplifiers is magical in its own way, and none can be said to be absolutely better than the other, only different and inevitably appealing to different musical tastes.

I had a Shindo Monbrison pre and Cortese 10wpc (F2a tube) SEP amp driving 12" PHY-HP drivers. That combo was better than any SET I ever had. I bought them used, kept 'em 18 months and after re-selling them it cost me $500.

TL;dr - the quality of output transformers is very important, and may be partly responsible for the superiority of the PSE over the Firebottle SE. Additionally, the extra power of the PSE is difficult to achieve using a single tube unless you whip it hard, possibly into higher levels of distortion. PSE lets you get a good 15-20 wpc (nominally 12 dB) which means you can use almost any reasonably sensitive speaker, and there are a lot of great sounding ones out there.

As far as a 45 SET, I think it is one of the best tube ever (along with the VT52 and 50) but requires your to accept certain compromises: your speakers with need to be extremely efficient to satisfactorily fill larger spaces, very efficient (>93dB) when used in the near field or in smaller spaces, and in both cases you may want or need active bass support depending on your expectations.

If you do want to go the 45 route (or anything < 3wpc) then your speaker game needs to be appropriate. I've found that speakers with highish impedance and minimal crossovers work well. I have personal experience with Cabasse (older DIY models of 94 dB sensitivity) and various Omega speakers. The latter really work well and begin at $600 with the most expensive models topping out at $4k. Where it would really shine is with ultra high efficiency horns. I'm partial to Altec, but I am biased.

+1 on horns or very efficient single drivers with a 45 amp. Dennis did build Inspire 2A3's too. I saw one he had on the auction site last year. Tempting but...I resisted.

Capacitors...again

I have been running Jupiter Red Astron .02uf, tin foil & Mylar, caps paralleled with a .01uf 600v Vitamin Q in my amp for about a week and they are going to stay.
Wood got more woody and the bass is excellent. YMMV.

The Astron's are $11.50 each and the VQ's are about $5 and can both be had on the auction site.

Musica Amantem, I would maybe think twice about running your tekton Lore with a 45 amp. The Lore uses an Eminence Pro Sound driver that likes a little power. While I don't want to discourage anyone from buying from Dennis, but you may be a little happier with Guitar Dave's PSE on the auction site. Of course you can buy straight from Dennis, and he has given me frequent flyer discounts now that I've bought three pieces from him. I haven't completed my comparisons yet, since my PSE is not fully broken in, but if you need the extra power (and you probably do), the PSE may be a better choice than the 45, especially if you are not committed to really high efficiency speakers.

FloridaBoy - is your amp the original KT88HO (15 watt xfmr version)? I may want to compare notes with you. My current ultimate application with be an ALtec 414/802/32A in a 4 cu ft cabinet tuned to 40hz. The 414 will run with no crossover and the 802 may be brought in with a 1st order crossover or some other option (Joe Roberts and Joe Esmilla both have ideas on this. They are not too expensive to try). Given the need to pad down the 802 to match the 414, I am toying with the idea of running the PSE ( 5U4/6V6) on the 414 (10 watts into 97 dB) and the KT88HO with 6V6's (5 watts into 100 dB above 5,000 hz). It may need no attenuation at all and the PSE would run the entire vocal range with no crossover in the circuit. The coupling caps on the PSE can be optimized for bass and midrange and the caps on the KT88HO can be optimized for HF performance.

Quote:

Originally Posted by Rosco65 (Post 801758)

I see what you mean. I would not want to replace my current KT88 oversize T Inspire for the PSE basically because it is an upgrade on the same line. The 45 SET, OTOH, represents another approach with its own special features. But, I recognize I may have to re-assess plans for the loudspeakers if I go with the 45, in which case a horn-based 102+ dB's may come in handy. Any suggestions other than the DIY Altec? I need a pair of loudspeakers already built.

Quote:

Originally Posted by Musica Amantem (Post 801768)

Depending on your space and budget, Klipsch LaScala's or perhaps Altec 19's come to mind. You can also look at Bob Crites Cornscala's.

Quote:

Originally Posted by Rosco65 (Post 801770)

Depending on your space and budget, Klipsch LaScala's or perhaps Altec 19's come to mind. You can also look at Bob Crites Cornscala's.

I had LaScala's for 23 years. Then got the PHY in Auris enclosures from Han Kortenbach. I was his first US customer.

Musica, you have a bad case of Audio Nervosa. Only the Zeka virus get more attention. :D Your present amp, pre and speakers are fine. Especially for a small space.

Roscoe,

FloridaBoy - is your amp the original KT88HO (15 watt xfmr version)? I may want to compare notes with you. My current ultimate application with be an ALtec 414/802/32A in a 4 cu ft cabinet tuned to 40hz. The 414 will run with no crossover and the 802 may be brought in with a 1st order crossover or some other option (Joe Roberts and Joe Esmilla both have ideas on this. They are not too expensive to try). Given the need to pad down the 802 to match the 414, I am toying with the idea of running the PSE ( 5U4/6V6) on the 414 (10 watts into 97 dB) and the KT88HO with 6V6's (5 watts into 100 dB above 5,000 hz). It may need no attenuation at all and the PSE would run the entire vocal range with no crossover in the circuit. The coupling caps on the PSE can be optimized for bass and midrange and the caps on the KT88HO can be optimized for HF performance.

I have this amp: http://i67.tinypic.com/k4gp77.jpg

It has the 20 watt transformers and, per Dennis, built on the 45 chassis. It is single ended and triode strapped. 5 watts with 6V6's. 7 or 8 with 6L6's. I took a step backwards and am driving Heresy III's, no subwoofer. This amp and the LP27a really strutted it's stuff with my buddies Volti Audio modified La Scalas. My friend was quite surprised. However the H III's are a great match for my smallish room. The original Heresy was my first 'good' speaker. I traded them up for LaScalas in 1978. A big circle but I thoroughly enjoy what I have now,

The Shindo gear was the best sound I ever had but I just could not justify keeping it. To be perfectly candid, my present rig is 80% of the Shindo at 20%
of the price. For me, the chase has ended :thumbsup:

The only thing I may do is change some resistors to carbon film.

Tube amps are fine things, reasonably priced one's that can deliver even more so, and if he continues to dominate the forum for the foreseeable future it must be for a righteous cause, and Mr Had will certainly get a drink from me if I meet him in a bar, and no more sardonic humor either.