play airgap of autoformer volume .

Discussions and experiences with user adjustable gaps.
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papagenohyun
Posts: 7
Joined: Mon Aug 22, 2005 5:26 am

play airgap of autoformer volume .

Post by papagenohyun »

hello. this is kim in south korea.
i bought Dave's autoformer several weeks ago. and have fun with its sound.
my system is as below
1) poweramp : 2a3ppp ( input impedence is 100k ohm )
2) source: K&K audio rakk dac with passive board ( output impedence is 3.5k ), and steve bench riaa 5 phonostage.and self made loesch phonostage.

as you know, my source is high output impedence so my results may not be true to low impedence source

i bought basic autoformer from dave , and i know that it has 20henry inductance. so somewhat worried that it has some weak point in bass performance .
in the introduction page , dave wrote that low frequency is determined by source out impedence and autoformer inductance.
so i have high impedence source and i think 20henry is somewhat lowish.

i connected this autoformer to source and poweramp , just like passive linestage.

yes, it has too weak bass, almost no signal below 100hz.

so i emailed Dave about this problem, and he recommended me to play airgap.
and he recommended to restalk 3*3 ratio.
as you know, it requires me to resolder and solder all the wire from transformer and switch.... it is very time consumming job.

at last, i did it, and gave a listen to it.

wow, bass is almost best ever i have heard.

but high frequency and midrange sounds somewhat dry and brittle to me.
but overall balance is very good.

so i took it to my friend to try how it sounds to his system
his system
1) 20k input impedence solid state poweramp
2) pre: hovland linestage ( wow expensive one it is ! )
3) source : meridian G07 ( output impednce is 50 ohm )

first, tried autoformer instead of hovland.
- too many bass with g07. too bloated and i guess you know how it sounds. boomy...
then connected my rakk dac instead of meridian g07.
slight bass exaggerated but ok, no boomy, but bass is somewhat exaggerated to my taste.
rakk dac sounds way better than G07 alone ( i used g07 digital out for rakk dac )

so,,,,,, i concluded that if i will use low impednce source, and high impedence source at the same time in my system, i have to have two version of autoformer.
one is high henry.
the other is low henry. ( for low impednce source )
otherwise, i cannot get best match for each impednce setting.
if i choose high henry, it is ok for high impedence source, but too much bass for low impedence source,
if i choose low henry airgap, it is ok for low impedence source, but no bass for high impedence source.

that is one conclusion in several weeks ago.

oh yes, autofotmer volume sounds way better than hovland.
more dynamic and better resolution and anything you say.
hovland has only some tube tastes.

and then,,,, two days ago, i received Tribute audio autoformer volume passive preamp at last ( i waited for almost one year since ordered day )

then, i compared the two............
then i begin to think more about airgap playing......

to be continued
i[/b]
dave slagle
Posts: 2014
Joined: Sat Jan 22, 2005 3:54 am
Location: NYC
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Post by dave slagle »

hi kim,

thanks for the honest report. I agree 100% with your impressions of too small of a gap improving the bass and hurting the highs and too large of a gap hurting the bass and improving the highs. It was this experience that convinced me that the gap of a device needs to be adjusted in system.

your mention of desoldering the autoformers to adjust the gap makes me want to point out that i suggest 6" leads to allow for ease of gap adjustment.

I feel that any possible compromise added by the extra lead length is greatly offset by the ease of gap adjustment. I feel gap adjustment is a first order effect and it should be the main concern and everything else (shielding, potting, lead length, switch selection, etc.) should be dealt with after the best sounding gap is determined.

dave
galibier_numero_uno
Posts: 13
Joined: Mon Apr 04, 2005 10:47 pm
Location: Colorado Front Range

Post by galibier_numero_uno »

Hi Dave,

I really like your philosophy of making sure that 1st order improvements get the attention they deserve. We never run out of this level of change to address ... even with an infinite supply of espresso beans :shock:

It cannot be overstated that in building a component, if it becomes too "extreme" in its architecture to the point where it's difficult to adjust and tune, then you'll end up losing the sonic battle. You won't perform the fine tuning necessary to optimize the device in your own system. :idea:

Any minor gains you make by for example shortening component leads is offset by human nature - that you won't want to spend the time dialing in the component (e.g. restacking the lams) to work best in your system.

Cheers,
Thom
|
| Galibier Design
| ... crafting technology in service of music
|
| http://galibierdesign.com/
| (303) 817-0365
|______________________________________
papagenohyun
Posts: 7
Joined: Mon Aug 22, 2005 5:26 am

Post by papagenohyun »

progress.

i have got tribute amorphous autoformer volume passive preamp now,and i can say some comparision between the two passive preamp.

my source has around 3k output impedence ( phonostage and also dac )

when i test 3*3 stacking dave autoformer with 50 ohm output impedence of meridain g07, the bass is too much and uncontrolled.
but when i put tribute, sound is very well balanced.
bass is definitely better than hovland preamp and dave's

so i have to reduce inductance of dave autoformer. so i restack it as 3*4 alternating methode.

when i test 5*5, the bass is not good enough compared with tribute.
tribute has more bass,

so i think 4*4 stacking is the same performance in bass with tribute.
but i like some fuller sound, so i chose 3*4 stacking.

with this stacking, i cannot find any high frequency distortion or irritating sound. but bass and midrange is fuller than tribute which i think is somewhat exaggerated but i like this sound balance. a litter fuller than real.

what is difference btw tribute and dave.?

dave has some color in high midragne. somewhat make me feel clearer and faster. i think it is due to permalloy core.
i donot like permalloy core's coolness. but dave's is different.
very euphonic and musical coolness.

tribute has very neutral character.
it does not add or distract form input signal.
so it is very sensitive to source and poweramp choice.
and it is more accurate in low mid and bass area.

i do like both of them. i cannot tell which one is better in objectively.
only it depends on one's preference.

with high impedence source, i would like to recommend 5*5 or 4*5 or 4*4 stacking. i think it is more reasonalbe stacking.
but like me who wants more fuller and euphonic sounds, i recommend 3*4 stacking. it is somewhat exaggerated in bass but very easy and full.

tribute is not that full but very tight and deep bass.

commercial active preamp is not comparable in any price range.
only my gary pimm 26 preamp can hold its own in these two great autoformer volume control.

phonostages are

1) steve bench riaa5
2) loesch 417a-6gk5

both are also great phonostage which cannot be found in usual commercial phonostage.
i prefer both to ear834p, fi yph phono, hagerman trumpet.
kaaos
Posts: 6
Joined: Tue Mar 08, 2005 3:46 am

well, it works!

Post by kaaos »

After reading Papagenohyun impressions I decided to restack my autoformer to see if I could get more bass. It took me about 15 minutes to restack both autoformers and it's actually a lot easier than I thought it will be.

My autoformers were custom made with butt gap and about 20H inductance. I've restack them to 4x4 which I guess gives me approximately 120H.

Sound?
The only change I could notice so far is more bass and more dynamics. I couldn't hear that sound became any worst than before. It was bit late and I didn't want to try any other way of stacking like 4x3 or 3x3 but I will try them tonight and see if sound will improve any further.

The whole thing was a great fun and it's so simple and easy to do that I wonder why I didn't done this before.

Anyhow, thank you Papagenohyun and Dave, your comments and suggestions made me go into this and as a result my great sounding Autoformer pre-amp now sounds even better.

Regards
Goran
dave slagle
Posts: 2014
Joined: Sat Jan 22, 2005 3:54 am
Location: NYC
Contact:

Post by dave slagle »

Hey Kim and Goran,

Thanks for actually playing with this and reporting back.

Goran, what was your source impedance just to keep things in order. In our initial discussions, I seem to recall a low Z source so any info on the actual source Z and the recommended load would be very interesting.

As for what is happening with the various stackings, I think it has more to do than with just the inductance number spit out by a meter. I think the various stackings kim tried (3X3, 3X4, 4X4) would all be essentially the same inductance wise, but what does change is the nature of the gap.

At some point, if both of you could simply invert the two outer lams of the stack I think the results would be very interesting.

So if you have a 3-4-3-4-3-4-3-4-3-4-3 you would invert the two end lams to get a 1-2-4-3-4-3-4-3-4-3-4-2-1

Dave
kaaos
Posts: 6
Joined: Tue Mar 08, 2005 3:46 am

Post by kaaos »

Hi Dave,
I use APL-3910 player with output impedance of 50 ohm.

I am going to try some different stacking tonight. My autoformers have 37 laminates so I think I could try 1-2-3-4-3-4-3-4-3-4-3-2-1 and see how that works.
Unfortunately I am not able to measure anything and give you some useful data but I could at least tell you how good it sounds.

regards
Goran
dave slagle
Posts: 2014
Joined: Sat Jan 22, 2005 3:54 am
Location: NYC
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Post by dave slagle »

kaaos wrote:Hi Dave,
I use APL-3910 player with output impedance of 50 ohm.
interesting, i wonder if it could really deliver 40ma into a 50 ohm load? (assuming a 2V output)

I suspect that Z-out and the ability to deliver the required current into the load are not related, which leads to odd behaviors like a 50 ohm source requiring a 100hy load. (a 250:1 Z ratio) So maybe we need to make new rules for low drive and high drive sources.
I am going to try some different stacking tonight. My autoformers have 37 laminates so I think I could try 1-2-3-4-3-4-3-4-3-4-3-2-1 and see how that works.
great!
Unfortunately I am not able to measure anything and give you some useful data but I could at least tell you how good it sounds.
luckily, i can replicate your experiences if something interesting shows up so listen away and i'll be responsible for the rest.

dave
kaaos
Posts: 6
Joined: Tue Mar 08, 2005 3:46 am

Post by kaaos »

dave slagle wrote:
kaaos wrote:Hi Dave,
I use APL-3910 player with output impedance of 50 ohm.
interesting, i wonder if it could really deliver 40ma into a 50 ohm load? (assuming a 2V output)

dave
According to Alex (APL) the output voltage of APL-3910 is 1.5V

regards
Goran
kaaos
Posts: 6
Joined: Tue Mar 08, 2005 3:46 am

Post by kaaos »

Hi Dave,
I restacked my autoformers again yesterday to 1-2-3-4-3-4-3-4-3-4-3-2-1 and result is simply amazing. There is even more bass. I had a couple of hours to listen some favorite music and what I noticed is following (compared to original butt stacking):

-There is a sense of authority across the whole frequency range
-Sound is now very focused
-More dynamic
-Bass improvement is amazing, it's so controlled, strong, tight and punchy that is hard to believe.

I didn't really expect this much of an improvement from simple restacking. It just shows how great your autoformers are and I really like the fact that by simple restacking I could change the sound to my taste.
It also confirmed my decision to keep autoformers in my system forever.

Thank you
Regards
Goran Nikolic
AudioGeek
Posts: 36
Joined: Mon Dec 26, 2005 7:19 pm

question...

Post by AudioGeek »

wondering about restacking laminations...

have a arcam cd player... SS and a 87K input impedance on amp,

running about -9 to -15db listening volume.

currently have standard but stacking.. but should I try something else??

how will my HF response be affected?
dave slagle
Posts: 2014
Joined: Sat Jan 22, 2005 3:54 am
Location: NYC
Contact:

Re: question...

Post by dave slagle »

AudioGeek wrote: have a arcam cd player... SS and a 87K input impedance on amp
what is the Zout of the arcam?
running about -9 to -15db listening volume.
ahhh.. nice to hear that!!! that suggests your gain structure is just about perfect!.
currently have standard but stacking.. but should I try something else??
depends on what the Zout of your source is. Chances are you will have plenty of inductance, and moving to an alternate stacking will give you more inductance at the cost of linearity.
how will my HF response be affected?
You could remove the core and not change the HF behavior from a first order approximation. The square wave and overall top end frequency response will not change with gap adjustment, yet the sound of the top end does change.

most have found the "proper gap" gives the best compromise between high end clarity and control of the bass. If the gap is too large, the top end get cleaner, but the bass suffers, and if the gap is too small, the bass gets slamming, but the top end suffers. I attribute this to IM distortion. Simply put, the smaller the gap, the less linear the inductance will be. So as you shrink the gap, the large number of HY's that gives you great bass comes with variability (non-linearity) and it is my belief that this non-linearity creates artifacts higher up into the frequency range that we perceive as a fuzzyness of the top end.

dave
PeterJ
Posts: 1
Joined: Fri May 06, 2005 12:15 pm

Post by PeterJ »

Hi. My name is Peter and I live in Melbourne, Australia.

My experiences with autoformers follow on the decision of several of my friends (including Goran above) to buy autoformers from Dave.

I remember being at Goran's place, auditioning his new autoformers on his APL-3910 player / SE-45 Amp / Exemplar speaker setup, looking at his 15-inch woofers, and wondering why the bass and dynamics were anemic. Goran agreed that something was up and after playing with various crossover changes decided to try restacking the laminations for higher inductance. The improvement was as dramatic as he has reported.

Around this time another friend who had brought autoformers, Justin, had bought a Nagra tube preamp which he found was more dynamic than the autoformers, even though he thought that the autoformers had superior transparency. There is a view that you need an active preamp to get dynamics and Justin's Nagra appeared to prove the point. Anyway, the up-shot of this was that Justin loaned me his autoformers and didn't seem in a hurry to get them back.

My system was apart at the time so I took the autoformers to my friend John's place. His system includes a Sony CD player with LC-Audio Zap filter and Clock (same as me), Audio Research amp (110W/Channel) and Quad 989 ESL speakers. He had just purchased an active preamp to get those dynamics. We listened to the autoformer and agreed that the presentation was extremely vivid but was down in dynamics and punch.

I asked and Justin agreed to me restacking his autoformers, which I did according to the scheme Dave suggested: 1-2-4-3-4-3-4-3-4-3-4-2-1.

Then I took the restacked autoformers back to John's place. This time the sound was transparent AND dynamic. John did not let me take the autoformers when I left that evening. (He has since ordered and received his own pair.)

A few weeks later Justin asked for his autoformers back as someone else wanted to borrow them. Justin has a separate DAC, parallel SE-2A3 amp and current production Tannoy dual concentric speakers. This time the autoformers outshone the Nagra, not only in clarity but now in dynamics as well. I was as surprised as Justin as there had never been any doubt that the Nagra was an excellent unit.

I have now received my own autoformers but may not get to hear them for a while because I am rebuilding my 300B amp to accommodate them.

As an aside, another friend who bought Dave's autoformers has not found a need to restack them - he uses them with a Meridian CD player which apparently has very low output impedance.

John has restacked his autoformers as: 1-1-1-1... I am looking forward to comparing them with Justin's unit to see whether he has gained anything or whether he has started to lose something. I have not been aware of any penalty associated with restacking so far, but time and more comparisons will tell.

Thanks for the bandwidth.

Regards ... Peter.
Nickolas
Posts: 1
Joined: Thu Sep 04, 2014 9:23 am

Post by Nickolas »

hy my name is Nickolas and I purchase your product Dave's autoformer I really enjoy this sound its owsum
Daniel
Posts: 35
Joined: Fri Jan 10, 2014 4:50 pm

Post by Daniel »

I received my AVCs with a 1x1 stacking (0 to ground this measured 76H @1kHz??). Source is a triode strapped E55L through a 1:1 output transformer, so Zout about 600R.
With the 1x1 stacking bass seemed surprisingly weak given this yields maximum inductance. Listening to Madvillain's Madvillainy 12" I figured bass is all there, it's just a mess. Restacking to 2x3x3x3xrest of themx3x3x3x2 (40H) cleans that up to a degree where the lf is defined enough for me to recognise it at as a bit boomy and I have a direction to go.
dave slagle
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Post by dave slagle »

Daniel wrote:I received my AVCs with a 1x1 stacking (0 to ground this measured 76H @1kHz??).
FWIW... you have to measure the inductance of all audio magnetics at a frequency well below 1000Hz in order to get meaningful results. The self resonance of the device will always be in the 500Hz to 2kHz range and trying to measure inductance near that will lead to incorrect results. @ 60hz the inductance of the autoformers as sent will be between 130 and 200hy depending on the excitation level.

One other thing to consider when you increase the gap size for a given source Z is your low frequency corner moves up and often times (particularly with vinyl) keeping the low frequency (sub 20hz) info from creating havoc downstream often cleans things up.

dave
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