ampsandsound Improvement on an already Awesome tube amp

[Deang]

At one point you were talking about a hot rodded Kenzie? No?

I need an amp that can power speakers and has a headphone jack. Something a little more elaborate than the standard headphone input topology would be nice. I'm severely disadvantaged here - I know very little about amps.

We should probably talk. 937-823-9902. Please don't text. I don't carry my phone in my hand 24 x 7 like most these days (it's finally happened - I'm old).

"Constant impedance".

I hired John Warren to run some tests for me. Yes, that means I paid him for services.

Measurably, when you add the swamping resistor to the autotransformer, you remove the primary inherent advantage of the autotransformer and it actually behaves more like an L-pad -- which is why it becomes "constant impedance" (L-pads are "constant impedance"). So, what is the "advantage" of the autotransformer? It's an impedance multiplier, and as you attenuate, impedance seen by the amplifier goes up, reducing the load on the amp. The swamping resistor impedes that, literally. I mean, you can't have a relatively "constant" impedance and "impedance multiplication" at the same time.

However, using an autotransformer with a swamping resistor to keep the impedance stable while attenuating on the fly is a powerful tool for those who plan on trying different horns and drivers. It might surprise many to know that this technique was first employed by JBL in 1976.

This idea that amplifiers "like to see" an 8 ohm load is erroneous. Amplifiers may be tested with dummy loads, but they are specifically designed to handle loads of all types - they have to be - because that what loudspeakers do to them as frequencies change.

Since I'm still waiting on parts to come in, I did a marathon last night and built myself a pair of networks with some Auricap XO capacitors -- no time for a Jupiter build. Now, I could have built a constant impedance filter, but instead chose to build a modified Type AA. I already know the mids will be too hot for my ears, so I just took them another 3dB down. This also allows for a horn change (but not a driver change).

The old simple filters are cool. PK basically just tied the drivers together and let the horns do the crossover work.

A long rambling post to simply say that you don't need "constant impedance" and higher part counts to knock 3dB off the midrange to get a subjectively better sound. In fact, if staying close to stock, while sitting relatively close in an averaged sized room -- reduce the part count and put the money into better sounding parts. These speakers deserve better than $4 caps.

Incidentally, the AK-2 takes the midrange down 6dB, so it's not like shaving a little off is like some cardinal sin.

Edited June 14, 2014 by DeanG

[BEC]

Incidentally, the AK-2 takes the midrange down 6dB, so it's not like shaving a little off is like some cardinal sin.

But remember also that the AK-3 replaced the AK-2 very quickly taking attenuation to just 4db.

[Deang]

Yes, true. The higher output level curves better for sure. All I'm really trying to say is that some back and forth movement due to room acoustics, the fact that people hear differently, and have different ideas of what "sounds good" -- is okay -- and we don't need "constant impedance" to accomplish that.

I really enjoyed the talk last night.

[joessportster]

Dean / Justin

? I saw Dean wants an amp to play both Headphones and Speakers, I thought the Kenzie headphone had Iron that was made and used for the different loads of headphones (specifically 32 ohm and 600 ohm) As I understand it this would no do well on speakers correct ??

I am guessing a Kenzie with a headphone option would end up being sort of like the SE84 in design except with the Kenzie topology / tubes / power output ??

As an aside This is exactly what I plan to do with the SE84, use it on the top end of speaker while using SS on the bass............Unless I am forced to buy a kenzie headphone amp upon listening

[Deang]

If you're right, then I can't have my cake and eat it too. Oh well.

Slow going on the LaScalas. Alexia Hope had her dance recital today -- I can't really call that "time lost", but it didn't leave me any time to do much. I finished the networks though, and I was able to avoid guilt because none of the parts showed up for the builds I'm supposed to do.

I did my first eBay transaction in about 10 years. I feel pretty good about this one.

http://m.ebay.com/itm?itemId=221463257949

In the end, I decided to "DJK" the networks.

Edited June 15, 2014 by DeanG

[Schu]

not to bad for something you just tossed together in your spare time.

[justinsweber]

Dean, there is a hotroded Kenzie with bigger iron... Kenzie SE.

The basic quetion is.. Did you want an amp for phones and speaker... then its the SE84 or SE-84 special ed.

If you wanted to try one for just phones... 32ohms and 600ohms. The Kenzie phones which has just completed bench testing.

I think the 1626/Darling/Kenzie is well paried with the LSs.

A kenzie (1626 power tubes, .75watt SET goodness) or even big ben (8-12watt KT88), can be had with a headphone option I guess but confuses things.

The SE84 is moderate power with a great headphone section. Trying to take a straight up power amp design and use transformers wound for headphone impedances proved to have some pitfalls that were really hard to work through... thus Ill call it good with 2 amps that offer head phones.

Dean, you have new speakers… how about amplification?

Edited June 15, 2014 by justinsweber

[justinsweber]

Not to confuse things... could someone start a new threat and explain diff between an AA, AK and AL networks.

I have a AL-3 which I understand is a good LS network... that said, Im not loving the sound.

[Deang]

There is so much in the archives - an insane amount of discussion and data.

Tomorrow, I will look for a couple of good threads to bump.

I don't care for the AL-3 either. My opinion is that the more parts you add, the less cohesive it sounds - and too many parts more, and the transients go soft. I also notice a weird lagging effect that I can't quite put into words.

I spent today listening to three networks: Type AA, Type AA modified (3dB additional midrange attenuation and .40mH coil in series with K-55-M), and my SuperX built with ClarityCaps and Mundorfs.

The question of course is this: which network is best for low powered amplifiers and the kind of listening that goes with that.

But, I don't have a low powered amp, I have a Luxman R-117 receiver with 160 wpc. Still, I've owned a lot gear and consider these units, along with the M-117, among the best sounding units I've ever heard, and they match very nicely with Klipsch anything.

My rooms are mostly on the small side, except the finished basement -- but I only use a section of it. All listening was done in quasi-nearfield, about 8 feet from the speakers.

I started with the modified AA, and sure enough, it sounded a little dry and closed in at my normal listening levels. However, as I surmised -- the bass came up some, and jacking on the volume really lit the room up. I was surprised by the non-fatiguing nature of the sound -- I was really expecting it to go to crap, but it didn't. Peaks were between 110-115, and it sounded awesome. Low volume listening was a disappointment though. So ...

I reverted the filter to stock, and was so happy when I heard what I heard. clear, open, with the sound jumping out to my listening chair. Awesome, and perfect for the way I listen. Live level listening was loud enough without showing signs of distress. However, nothing like the modified version, which was kind of insane.

The SuperX didn't disappoint. It sounded good at low volumes, but not as good as the AA with Auricaps. It also sounded good loud, but not quite as good as the AA with the midrange dropped 3dB down. Still, it delivered most of what the other two did, and you get the attenuation convenience feature. However, It is my opinion that this not the network for low power amps.

The Type AA with Auricaps (always use something better than entry level capacitors for best performance), was clearly the better performer at low to moderate volume levels.

I'm not learning anything new, but I am getting a good refresher course.

The K-400 is tolerable, but overloads easily and isn't as open as the Trachorn I had in my Klipschorns. So, like Justin, I feel like a new horn is in order. I was hoping to keep these stock, but I guess that's not going to happen.

I got lucky on eBay and scored some beautiful dual phase plug K-55-Vs out of some Heresys, and I'm looking forward to loading those in.

By the end of this next weekend, I'm sure to be back to Type As. It really is the best sounding network for these type of amplifiers, and the low part count combined with the small values means you don't have to settle for entry level parts -- you can invest in the good stuff. When it comes to parts, you get what you pay for. Sorry, but a $2 2.2uF Audyn does not sound the same, or nearly as good as a $75 2.2uF Jupiter Flat Stack Film.

Edited June 18, 2014 by DeanG

[joessportster]

Have to bring this back to life, as the amp has really started to strut it's stuff now, Never been a big believer in all the break in business however headphones have opened my horizons a bit

I have a level of SUB BASS heretofore not heard on the HifiMan HE500's ...............tones proved the amp to dig deeper, I may have to see if I can hear more now via tones...............

It is a pleasant surprise to be sure. Color me happy

Thanks again Justin

[Deang]

On the fence about break-in/burn-in? And you call yourself an "audiophile"? Wow, lol. :-)

[joessportster]

Actually I dont call myself an audiophile, I just love music

[sunnysal]

I like the amps and sounds stereo 15 SE a LOT! T

[joessportster]

are you saying you have one ??, if so please post listening impressions..........................once i get settled I plan on using another of justins amps in a Bi-amp setup

[jbsl]

Just noticed this and agree with the review of the Stereo 15!  

 

I bought one of Justin's first Stereo 15's and have loved it.  

 

I was using it with Fortes with great results and just got Chorus IIs and the bass is even better with the Chorus IIs and Stereo 15.  

I may eventually get the Stereo 15 SE.

[jimjimbo]

Just noticed this and agree with the review of the Stereo 15!  








 








I bought one of Justin's first Stereo 15's and have loved it.  








 








I was using it with Fortes with great results and just got Chorus IIs and the bass is even better with the Chorus IIs and Stereo 15.  








I may eventually get the Stereo 15 SE.[emoji4]

I have a stereo 15 SE if you are interested.