I agree with both of these observations.

If this CN is still needed at moderate to loud volume levels, then that implies the speaker in its standard configuration has a real problem. My goodness, a 9.5dB attenuation through the midrange and well up into the lower treble to get it to sound balanced?

Contour Network
 

Hello all,

Please understand that the Contour Network that Dennis put together for me was a fun experiment built out of parts he had lying around. I am pretty sure he was shooting from the hip a bit as far as the values of the components. I do not recall him having used a calculator and comments like "this should work" being used. As we listened before and after we enjoyed some of the effects it had on my speakers powered by my amplifier. To all others, YMMV or not at all if you choose not do drive in the same car. I shared this with you all because I thought you might find the story entertaining. Dennis was excited by process and we had fun testing the outcome. Though he told me it was ok to share here I received an email a little while ago where he is having second thoughts. Some here may know why.

The tubes will last longer than I will. :scratch2:

I can understand where it could be seen as critical of Omegas. I haven't been taking it that way at all. I have seen the need to supplement lower and higher frequencies but absolutely love my SAMs. I have listened to them alone and they sound wonderful. The bass they provide is pleasing bass, however I like having lower and stronger bottom end. I would say the same about running my SAM/8" woofer combo. When the plate amp is set to extend down to 30Hz, the combo is great. But having a pair of F12s, even for just up to 30Hz improves things even more.

I guess if I were in your shoes, I would probably refrain from this conversation on AC. Even if the CN is benign as electronics in the speaker signal path can be, it is counter to the Omega philosophy and approach.

I like to tinker and this was a good opportunity, not so much from sound quality need, but from need to tinker, explore, and learn. Simple enough (it seemed) to tackle something and learn something. Still true, but the links provided remind me that I will only learn as a rank amateur. Beyond the first level of this stuff I get overwhelmed and shut down. I'll confess that way back in high school when I took Physics this was also true. I was a top student in the the class overall and found most of the areas fascinating and accessible. It was the electrical/electronic area that challenged me the most and I mostly muddled through it.

So, I think I will break out REW when I get the chance (hard as our kitchen remodel starts Wednesday!). I would be interesting to see how my frequency response is on paper - ie, how flat or how "contoured"!

Thanks for posting the CN details. I think most of us just like analyzing the tweaks we can do to our systems. I fail to see anything that would cause drama: Dennis listened to a pair of well-regarded single driver speakers, applied an on-the-fly tweak that you both liked, and you told us about it. Those of us with Omega speakers tend to try out tweaks on our own (adding supertweeters, subwoofers, helper drivers, etc.).

TWIW, Seas also publishes a contour network in the application notes for their Alnico FR driver. It is supposed to shelve the upper frequencies in rooms that are too live. Seas also recommends trial-and-error experimentation with parts values.

What were the upgrades that made your LP-27a a Special Edition? Mine has a DACT attenuator but is otherwise "stock". I can see maybe a bit more PS filtration and a difference component choice.

Attachment 51085
Attachment 51086

Take a look. I do not remember the particulars. My wife told him to give me "the works". It was a gift.

Sorry that photo is pretty worthless. I'll try and get a better shot.

Thanks for the replies regarding the heat of my fiery Fire Bottle. I assumed it was normal but I rarely touch the transformers of tube amps (my previous home audio one was an utterly different push-pull type A/B anyway), and with guitar amps I simply haven't noticed…I will check out the transformer in my single ended guitar amp if I ever remember to plunge my hand in there...

My Inspire KT88 amp typically has lukewarm transformers. However if I drive it hard, they do heat up. This is driving speakers which I believe to be approximately 91dB efficiency. Mine has the larger 20w output transformers. I suspect yours has 15w.

My amp is a December '16 build…so I think it has 17.2 watt transformers…or maybe 14…16.5? Not sure how I'd be able to tell.

The temperature of the transformers depends on the output tube and rectifier used. KT88's etc. and a 5AR4 run hot. My triode strapped Inspire runs hot with that combo and it has 20 watt transformers.

Mine has Gold Lion KT88s and a 5Y3S rectifier as supplied with the amp, and again, I have no idea what wattage my transformers might be…but now that my curiosity has been peaked about this, is there an easy way to tell which transformers were put in this amp? After all, it's a HO.

Post a pic. I imagine it has 20 watters. 5Y3? Try the KT88's with a recitifier with less voltage drop like a 5AR4 or 5V4G.

What do you guys think about the 2a3 fire-bottle Dennis has up on eBay right now? Really intriguing to me.

Thats a beauty. Analog posted a pict earlier here but the 12 on eBay really do it justice. I really like the asymmetry of the layout of these. Also interesting that he has it up for sale as a high bid sale. Cool stuff for sure.

Pretty amp. Not enough power for my needs.

The 15 or 20 watt question could be answered but I can't seem to post a pic, but a clear pic of the innards of MY amp is among the photos of the most recent Fire Bottle HO posted by Had on Ebay from a couple of weeks ago…so it's there if anyone wishes to look at it…thanks in advance!

Also, is there any risk to these amps in changing to other rectifier types?…such as the suggested swap from a 5Y3S to a 5AR4? I assume not, as various recommendations seem to indicate no cap changes are needed or bias issues exist, but I'm careful with that which I do not understand.

No risk at all. You can use any rectifier with any power tube in your amp except 6V6G's & 6L6G/GA's. These are lower power tubes. With them stick with a 5Y3 to be safe. The 6L6GB and GC are higher rated tubes and any rectifier is fine. Do you have any other rectifiers in your tube stash?

I would recommend 274B for any tube smaller than KT-88 or 6550 (i.e., 6V6, 6L6, KT-66, 350B), except of course as FloridaBoy pointed out, the shouldered G ST 6V6 and 6L6, which need a 5Y3 (80). With the larger tubes my best results have come from 5Z4 and 5AR4 (low V-drops), as these behave better with the sagging larger tubes. KT-77 can go either way. Experimenting is the only way to dial-in your preferences, as each system/setup responds differently.

I do need to add some rectifiers to my tube stash if only to provide a modicum of credibility. The only other tube rectified amp I own is an EL84 based single ended guitar amp with an EZ81. And, I appreciate the advice. Thanks.

The Shuguang 274B and GL 5AR4 are worth looking into.

Yesterday I ordered both the Shuguang 274B and a Gold Lion U77/GZ34, so things should be getting rectified around my house.

They, especially the GL GZ34, will wake up the KT88's. Just trust your ears. :thumbsup:

I might fool myself into liking the Shuguang more than I should only because it looks so cool, but my ears are ready (just cleaned 'em). My ears just got me into trouble as a new (3 months…trying cables and whatever to get these things to come alive) pair of higher efficiency speakers are failing me…not enough clear tweeting from the tweeters, and the manufacturer/owner of that company is sending me new resistors to give the ribbon tweets less restriction. I put my previous speakers (yet unsold luckily) back in the system and although the lack of relative efficiency (new speakers are 93db, older ones now back in the system around 89 to 90) could explain the "HO" (what I call my Fire Bottle…and why not?) running hotter, but with the astonishing resolution my rig now has I don't mind at all. Go HO!

You may need to give the tubes a few hours to settle in. These rectifiers will give you more power and the amp will run hotter.

I would venture to suggest anything under "true" 95 dB (not demanding impedance curves) won't do justice to that amp, probably even in a near-field configuration. You may have enough SPL, but the amp´s performance is not the same. Also, try the 100 Hz filters with a SUB in the future, big difference! Of course, my experience is based on a Triode-strapped version of the HO.

My current speakers are in use until I can re-wire the tweeters (for more output…they need it) in my more efficient speakers, and the HO's performance is astounding enough in this configuration that the tweeter issue will have to have a profound effect to kick the current preferred speakers aside. (2 REL subs are also in the mix)…I have been looking at much more efficient speakers for eventual use anyway so that gives me a reason to live, and if the new rectifiers do cause the amp to run hotter that's gonna be interesting…I haven't let the new rectifiers settle in as they're not here yet, and I'll have to consider the effects of jet lag or mail carrier lag on their performance. If the triode strapped HO (!) is the lower powered version I imagine far more efficient speakers would make a tremendous difference, but no filtering seems necessary in my current rig so my HO remains unmolested, so to speak.

The GL GZ34 seems to work well, and the HO doesn't seem any hotter than with the 5Y3S (except maybe for how it sounds). This last thing was carefully tested with my calibrated human palm while running a CD Julian Lage gave me (name drop…it's a name drop).

Since installing the GL GZ34 and it having some break-in time, it seems that the bass output from my HO has increased significantly…surprising.

If you really want neat, seamless bass, try the 100 Hz filters :)

Is that based on a "triode strapped" lower powered amp? If so I can see why you'd want to do that. I was simply wondering if the increased bass was due to the GZ34 or my imagination, and since I'm using 2 REL subs running from the speaker outs to the REL High Level inputs I'm utilizing the bass tone of the HO (I like that). It sounds astonishingly good even with my modest efficiency speakers with coherency and clean bass for days. If I were to use a 100 hz filter, I would have to run long unbalanced signals to my subs (no no no) and force the subs into higher frequencies (High lows? Low mids?) which I prefer they stay away from (they sound better at around 50hz or lower). With the new rectifier I turned my subs down a little from where they were previously (I adjust the level of them from time to time as recorded bass levels vary), and, surprisingly, they're not pushed as hard with the HO anyway even with bass slam heavy recordings.

The approach works for any of the Inspire configurations. The key is not to over-impose bass frequencies but let those be handled exclusively by the better capable SUB. The amp will work effortlessly without that drag. Balanced and unbalanced source signals makes no difference at low frequencies. The issue is not the SPL of bass lines but their integration and complement to the frequency distribution. In the case of not so sensitive speakers the effect is even more tangible. IME, more bass from the change of a rectifier may bring a tradeoff in SQ at higher frequencies, usually masking transparency in the mid-range. I experimented that until I applied the filters. With the filters, these larger tubes coupled with low V-drop rectifiers do not mask any detail or transparency anymore.

I utterly get the filter thing, but I don't think my amp's output is imposed upon by low frequencies at least based on listening to it. My speakers have gained far more coherant mojo with the HO than with previous amps, including the mids and the upper frequency tone, and with the GZ34 it all seems simply clearer including the mids which were relatively clear already. I won't use unbalanced cable over a few feet as it doesn't work well at longer lengths (I've been a successful live concert sound engineer and professional live and studio musician for many decades, so balanced vs. unbalanced cable is one of the few things I know something about…few…very few), and the REL "high level" 100,000 ohm design seems like a great idea that's worked well for me for years. The HO is sending a fairly hot signal to the RELs from the speakers outputs and that's all HO generated, and it sounds great and effortless. But I get it...

Now that you have some new rectifiers consider a pair of the GK KT77's. :D

It is not an expensive fix. Just try it. You may be surprised. I know I was. Again, I don't think the XLR noise reduction is really significant on the subwoofer channel compared to your mains. My RCA SUB cables also run several feet, without any apparent interference.

Long runs of single ended cables seriously affect the signal and tend to load up their source…I use a micro amp to restore the sparkle to my electric guitars that's lost from cable loading. So "try it" I shall not. It's not a fix that I feel I need as I prefer to let the amp operate as designed, and it works extremely well without denying it its well earned low frequencies, which I'm afraid would risk hurting its feelings (no sad amps for me!). Not interested in buying long single ended cables, not interested in switching from the High Level REL inputs which many feel sound better (mine work very well), and at the level I listen I'm getting excellent, undistorted bass even when I test the sound without the subs, so I know the HO is doing fine. It seems happy.

My question was sidetracked so it remains unanswered: I seem to be experiencing more low end from the HO since switching to the GZ34, and I simply wondered if others had experienced that phenomena.

The GZ34 has a low voltage drop which would account for the change.