M-125 Output Impedance Tricks?

gktamps wrote:

ttocs wrote:

I'll try some tubes first since this is the least invasive approach.

Least expensive would be tubes. The Zeros are somewhat pricey, even raw, which is how I bought them, and then installed into nice stout chassis boxes of my choosing.

Sorry if I missed it, but what preamp are you using? Do you have tone controls? There is no shame in using them if you have them, and I say that as an owner of 10-11 preamps ranging from very good to excellent but not esoteric - with and without tone controls. No intention of starting a tone control discussion with the forum here, but there are good preamps with tone controls that don't kill the sound quality.

I use an Emotiva XMC-2, and yes, it does have tone controls which I haven't tried. i know, i know, . . . . So I'll try that also.

I think the treble and bass controls are configurable for the frequency. I'll check that when I get back home. Meanwhile, already ordered tubes that I've wanted to try since they are talked about so much. The resistor swap may or may not happen.

ttocs wrote:Hi all! I don't think I've posted anything here before since building my M-125 amps more than two years ago, but could be wrong. I've enjoyed all the helpful info gleaned from this forum!

This is something I've thought about from time to time since of owning these great amps but haven't really found any info which would directly answer my question.

Is there any nifty way to lower the Output Impedance such that the amp would be just a little bit happier with low impedance speakers such as the Martin Logan Expression as still sound great? I've compared the frequency response to a Krell multi-channel amp and yes, the Krell has no issue with extending the flat response out to around 16KHz before slumping, but the M-125 slumps around 10KHz (if I remember correctly). I'd like to be able to extend the flat response out farther if that's possible.

Measuring at various output levels the M-125 dutifully doesn't complain by showing any sag in the frequency response when pushed into higher volume, so for me, it's just to see if the frequency response could be extended a bit with these speakers. When connected to "normal" speakers the treble response goes past 20KHz, so the amps are working as they should, but the ML's are just a bit imposing on the amps. I think it says a lot that the Krell also has trouble well before 20KHz.

Started with KT88 tubes, now am using KT120.
I prefer and use the Weber WS1-T rectifier.
I thoroughly enjoy the sound of these amps, I'd just like to see if I can enjoy even more thoroughly-er!

Thanks in advance for any assistance!

Don't know if these would help. I don't have this issue-  

https://www.zuaudio.com/diy/loading25r

I've never been a fan of using resistive loads on speaker connections to alter impedance. A speaker is a more complex reactive load; using resistors can change the frequency response and take power from the output signal. The autotransformers don't function like resistors.

ttocs; try your tone knob for goodness sake. On my preamps with tone controls, only subtle adjustments are needed unless I'm listening to a really poor recording. You may find the same.

gktamps wrote:I've never been a fan of using resistive loads on speaker connections to alter impedance. A speaker is a more complex reactive load; using resistors can change the frequency response and take power from the output signal. The autotransformers don't function like resistors.

ttocs; try your tone knob for goodness sake. On my preamps with tone controls, only subtle adjustments are needed unless I'm listening to a really poor recording. You may find the same.

Well, it's not a knob unfortunately. The "tone" settings are buried in the Menu.
... and ...
The reason I haven't tried anything for a while now is due to the M-125's not being connected except for a couple tests here and there. There was work going on in the house, rewiring the a/v system to make things neater, so other than some testing some things - other than tube amps - the system really hasn't been fully functional, and the M-125's have been stored on the dining table during this time. Plus, I loaned out my absorbers to a friend because I'm making new ones, yadda, yadda, yadda.

So your friendly scolding is appropriate and well received! I'll be putting the M-125 amps back in action this weekend. And yes, I "do" know to use the Variac to bring up the voltage slowly like I did when I first built the amps.

I've been using the Krell lately, and it's been working better than ever! Krell told me years ago that if channels weren't "active" that they would not negatively affect the working channels, more power to the active channels. That is not correct. I recently pulled the wires internally for two of the channels and kept the first three channels connected. This in and of itself changes the power rating from 150WPC as a 5 channel amp, to 175WPC as a 3 channel amp. The sound is better, smoother, but the big change is a better soundstage which totally gobsmacked me because I never would've thought it would be as good coming from a single amp that's not a dual-mono design. It's not as deep as the tube monos, but it's just as wide, but the imaging is lower which is interesting. A new experience for me.

Since last week I've also been trying out a pair of mono amps from Emotiva which actually work quite well. They are the HC-1 amps that I wanted to try just before I got the M-125's a couple years ago, but they weren't released until late that year and I was totally enamored with the M-125 being an instant success. So now I'm trying them with the Fronts, just to find out, and maybe keep one to power just the Center speaker.

I just read the overview of your processor; apparently the entire signal is going through DSP and a parametric EQ, so it's not like an analog signal chain that has active or passive tone controls - it's already shaped by the design criteria of the digital processing. This is much like active DSP crossovers, so there is really no reason with your processor.

You've found the joy of having multiple different pieces of gear and the ever-evolving tonal and dynamic changes you can experiment with. I can relate!

gktamps wrote:I just read the overview of your processor; apparently the entire signal is going through DSP and a parametric EQ, so it's not like an analog signal chain that has active or passive tone controls - it's already shaped by the design criteria of the digital processing. This is much like active DSP crossovers, so there is really no reason with your processor.

You've found the joy of having multiple different pieces of gear and the ever-evolving tonal and dynamic changes you can experiment with. I can relate!

I like that statement "the ever-evolving tonal and dynamic changes you can experiment with". This explains what I'm doing better than I've explained it.

When just watching tv and in a digital audio mode of some type I can see the Tone settings. But when listening to music I've never been able to find it and here's why. From the XMC-2 manual:
"In Reference Stereo Mode:
• The output is always TWO CHANNEL STEREO.
• There is NO bass management, and NOTHING is sent to the subwoofer.
• You CANNOT use the Loudness Control, or the Tone Presets, or the Tone Trims.
• You CANNOT use Dirac Live or the manual Parametric EQ Presets.
• Level Trims, which operate in the analog domain, are still available.
• Speaker Distance adjustments are active for digital inputs but not for analog inputs.
• Stereo analog input signals are passed straight to the Volume Control and the outputs.
• Stereo digital input signals are converted to analog then sent to the Volume Control.
• Surround sound digital signals are decoded, mixed down to stereo (the Center Channel and
LFE signals, if present, are mixed into the stereo output), and converted to analog."

For music I use Reference Stereo. So this is why the Tone settings were hard to find because they don't exist with Reference Stereo, nor does PEQ.

I have yet to be satisfied with Dirac for the Fronts for two channel music, but I do use Dirac for HT, but only up to the XO in the Front L&R speakers. So Dirac just corrects below 300Hz for the woofers.

So using my ears for the main system setup of which settings I prefer to use has been about the best I can do so far with respect to using Ref. Stereo. The L&R are setup as Large, and I use two pair of subwoofers stacked just outside of each Front speaker and a'la Rel type setup. The subs are used as extra woofers and connected via the speaker level connections on the subs. The bass is very well worked out with exception of a dip from 60-70Hz that I use a fifth subwoofer in the back of the room to help smooth out via a miniDSP. The processor isn't involved with any of the bass for these two speaker setups.

So I guess that brings us back to the treble, which again, is not a really big deal. Just looking for a tweak, one or two of which will be tried next week.

Hmm. Well that's unfortunate.
Try the tubes, then consider the autoformers and any other tweaks, but ultimately it would not surprise me if you later feel compelled to have a more pure analog preamp.

"Well the squirrels are back again". (sorry, tv commercial)

Well, the 12BH7AEH tubes arrived early. So I've been going through some measurements to get a new baseline for the Krell solid state, and the M-125 with original supplied 5963 tubes.

I'm not using any Processor EQ or Room Correction, just straight up whatever it happens to output.

In running through some sweeps I decided to tweak the settings on the speaker to tilt the bass/mid-bass down a touch which on my speakers is -1dB Bass Control, and -2dB Mid Bass Switch. This helped to level the playing field because without these adjustments the bass is much more prominent, and by more than the settings would imply. A -1dB adjustment actually accounts for a -3dB difference for in-room measurement.

So all I'm working with right now is just the new 12BH7 tube, the resistors have not arrived. I inserted the 12BH7 into the rear tube socket, am I correct in using it in this position? I can't find my assembly manual since I cleaned up the basement, it's in a new bin somewhere. The bias is slightly higher with the 12BH7 by 0.035V, so I adjusted down to 1V.

Using the 12BH7 the amp has a bit more output by just under 1dB above 500Hz, and the falloff above 5500Hz has a different slope and hangs on better to 10kHz, but both tubes are exactly the same at 10-11kHz. While I don't consider this to be great, it's not remarkable, it's also not bad, it helps a little.

So my work-in-progress judgement at the moment is that there is more output where I'm looking for it.

Listening will tell the tale.

edit: Initial measurements while using a brand new tube notwithstanding, there's some good stuff, and some not so good. So I'll give the new 12BH7's some time. Too early to judge SQ.

edit2: It only took a few hours to substantially reduce the sibilance, selective glare, and unevenness. The sound is quite good now after about 8 hours on the 12BH7's, but everything in the midrange is a bit too forward. I didn't need more mids. But there is a touch more "sparkle" in the highs, which is what I want.

The resistors arrive early in the week, so R28 can be swapped out. I don't know how this will affect the sound, but I'll find out.

Well it's been interesting.
The tiny bit of sparkle I heard last night, along with the more forward mid range, have receded. Today after another 6 hours of listening, which near the end included what I listened to last night, made me think I was getting used to the BH7 tubes. The sound was more like I'm used to hearing, especially when listening to Tubular Bells where some of the sparkling tinkling sounds were like the 5963 tubes.

So I revved up REW to check. I was very surprised to see that the 5963 and BH7 tubes are exactly the same shaped traces, except that the BH7 has about 0.5dB to 0.7dB more output. See attached.
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It's not a bad outcome, there's a bit more output, and now I know a little about this tube. Tomorrow the resistors arrive that will allow more current, so it'll be interesting to find out what difference, if any, might there be.

My amp kits were shipped with 5963 tubes for the front and rear positions on the driver board.

Changing the rear position from a 5963 to a 12BH7 ends up sounding the same after the new tube has been run for more than 10 hours, but there's just a bit more output, 0.9dB to be exact at 10kHz. Putting 12BH7 tubes in both positions makes for +1.4dB more output. I can't yet hear how this sounds because I only bought a pair of tubes to begin with, but ordered another pair. I don't expect much if any change in sound, but maybe I'll be surprised with better dynamics which would be nice.

Once the second pair of 12BH7 tubes come in I'll listen for a while before changing R28 as Roy suggested. Also, unless there's some convincing evidence of what will be different if changing the output caps with Mundorf silver-oil, I'll be keeping the caps the amps already have.

ttocs,

Please keep the updates coming. It is nice to see the results from you experimenting - especially when I do not have to buy all the parts to experiment on my system... FYI, regarding the 12BH7 in the M-125s from Bob in 2016. The search on this forum works quite well:

"You can use a 12BH7 or a 12AU7 in either position or both positions on your M-125's. The power transformer is "overbuilt" and can handle the extra current draw of a 12BH7. You can also MIX 12AU7 and 12BH7 tubes in the M-125's. If you do, I recommend the 12BH7 in the REAR position and the 12AU7 in the FRONT position. In fact, that is the way I have my own two M-125's set up > A Mullard 12AU7 in the front position on both amps and a GE 12BH7 in the rear position."

Note also, that there is a majority of opinions that tube amplification softens the highs and lows of the music signal - thus is more pleasing to some people. Many others feel that this is not the most accurate reproduction of the signal and prefer the sound of solid state. I do not care as I am only interested in the sound that I like best - and I like the look of those beautiful glowing tubes. I even resist the SS rectifier just to keep the GZ33 showing its glory - and that it is more compatible with the auto-bias board that I also never wish to part with.

Mike

I'm just awaiting tubes and resistors before being able to give more opinions and post some results. But thanks for the cheerleading from the sidelines!!

In the meantime I've adjusted a PEQ filter for boosting the freqs centered on 10kHz a couple dB, which ranges from about 6kHz to 16kHz with a Q of 1. Using steeper Q's had some not so graceful curves, so this looks to be just a tilt up starting at 6kHz.

I sent an email to Paul Speltz late yesterday expressing interest in placing an order for a pair of Zeros. Haven't heard back yet, so I'll call tomorrow.

The second pair of 12BH7 tubes arrived today, as did the resistors. I popped in the new tubes so both amps are sporting the same config, the new 12BH7 Gold in front, and the older 12BH7AEH in the rear position. Both pair are Electro-Harmonix but different series. With the new tubes in front I'm not hearing anything bad, it's all good. Don't notice any difference from what I'm used to so I'll put some hours on the tubes then switch back to all 5963's. My guess right now is that it's probably mostly a bump in output power more than anything else. If that's the case, and nothing is degraded, then it's a win just for that.

I'll play with resistors on Saturday.

A little update.
No measurements, well, time measurements of how long it takes the power transformers to heat up - temp/vs/time, and listening with various tube compliments.

The tubes in play are GE 5963 as supplied with the kits, EH 12BH7AEH (the first pair I bought), and EH 12BH7 Gold Pin.

With 12BH7AEH in the Rear, and 12BH7 Gold Pin in Front, there is some "ragged edge" stuff going on with some vocals and certain distorted guitar, but mostly with vocals. It's not pleasant and makes me question everything.

Went back to twin 5963 for a sanity check and all was as I expected it to be.

Now I've got the 12BH7 Gold Pin in the Rear and 5963 in Front and the sound is very good. It's as clear as twin 5963's, great stage as I'm accustomed to, maybe just a tinge more life in the upper treble range, and something else, . . . . I'd describe it as a bit more lively. Maybe it's a tiny bit more dynamics in the mid/upper ranges? Don't know yet, but something is better.

One way I determine how much I like something is that I just keep listening and don't want to stop to change to another config. But the next config would be to put the 12BH7AEH in the Front position to see if twin BH7 tubes are what cause that "ragged edge", or if it was only with the BH7AEH in the Rear position. Tomorrow I expect to swap R28 for the 8.2Ω to see what that ends up doing. It would be nice if I could find out prior what that expects to change sound wise, but I'm not afraid to try, but that's one reason why I like to have baseline info for things like the power trans temp over time so I know what normal is.

So while changing the driver tubes doesn't answer the question about output impedance, it's a fun experience.

Paul from Anti-Cables responded to my email that he will call me tomorrow about ordering ZERO Autoformers.

FYI... I found running 2 GE 5693/12au7 tubes up front for voltage gain and 2 12BH7 tubes in back as phase splitters give me consistent quality in sound and image.

You have me very curious for the results of the Zero Autoformers. I would think that because the MLs have built-in crossovers all of the signal from the M-125s would go to the stat panels - thus the M-125s would handle the mids and upper range just fine. We are depending on the ML crossovers to basically bi-amplify our speakers with the class D amps driving the woofer and our subs. What happens in theory vs in practice can be very different. It sounds like your ears and measuring tools can distinguish small difference, so if you get positive results from your experiments I might follow your lead and experiment a little. My only hesitation is that I am running a tube preamp and might get different results.

I found it too difficult to run my home theater through all my tube amps so I just have my HT running through a separate Marantz SS amp with its own speakers. I'm nowhere near as picky with the sound of my HT as I am with my music.

Mike

I've been testing all the voltages inside one amp today. First with 5963 in both positions to get baseline measurements, then with the BH7's. I also used some different bias settings with the BH7's.

Then I swapped R28 from 10Ω to 8.2Ω and measured again.

When I bought the kits I bought both types of rectifiers, 5AR4 and Weber WS1-t. I decided I liked the WS1-T better and have used that ever since. The main issue to be aware of when using the WS1-t is higher voltages, especially for the quad cap. After changing R28 to 8.2Ω the voltages increased. I kept each run consistent and used what had been a safe maximum operating voltage of 118V, but this proved to be too high with the new resistor, pushing the voltage just over the max according to the instructions for the amps, at least with some bias settings, but when the bias is increased the voltages in question are reduced back to within range. So with the SS rectifier and a 1V bias, the voltage in the quad cap is too high by a few volts, but with higher bias voltage everything becomes within range. The issue then becomes stability when the bias voltage is set at 1.15V and the input signal is pushed to almost at clipping. So in the morning I'll check with lower line voltage settings, which should help quite a bit. I'll also check with the tube rectifier.

Regarding the ZERO Autoformers, I first emailed an inquiry Wednesday evening. Friday just before lunch I called and left a message and a couple hours later I received an email response from Paul saying he would call me on Saturday. Still waiting.

As I said last week, Paul from Anti-Cables emailed my on Friday - after two inquiries about purchasing ZERO Autoformers from me by email and telephone over two days - that he would call me on Saturday, but has not yet called. Is this normal operating procedure for this company?

edit: Finally heard from Paul. Placed order tonight.

The ZERO's arrived today! So I've been doing some initial testing to discover the combo that I'm looking for between which speaker tap to use vs which X-Multiplier on the ZERO to use.

It looks like the best combo for now is 3X and 4Ω Tap.

But it comes with a cost. Electricity being what it is, requires that if one aspect is increased, another aspect is decreased. This was not unexpected.

The cost at the moment is a loss of output by -4.9dB when the ZERO is used as stated above. There might be another one, but it's too early to say for sure, but it seems that the power transformer may be getting hotter sooner, but the only way to be sure is to use a playlist I have and keep track of the temp vs time (which I've done before so I know exactly what to expect).

The first plot is how it all shakes out. The second plot has the Non-ZERO trace lowered so it matches up with the ZERO trace at the XO of my speaker so I can see how things compare for the stat panel. As a recap, my speakers have self-powered woofers so I'm only interested in how the amps do with the electrostatic panels.




Next, I'll need to listen, which won't be till tomorrow night, unfortunately.

M-125 with Dual 12BH7 Driver Tubes.
Anticables ZERO-Autoformers using the 2X multiplier connected directly between amp and speaker, no speaker cables used.

I had been using fairly long speaker cables because the amps performed better with my speakers. But with the ZERO’s inline with these cables I found that the 3X multiplier needed to be used for best result. But, after moving the amps next to each speaker and connecting each ZERO between amp and speaker the 2X works better.

I don’t want to say much yet after only listening for just over an hour, but, I’m now hearing the sparkle that’s been missing when using the M-125 amps. Cymbals aren’t recessed like they were, now they’re more appropriately mixed. Lots of the little percussive sounds, the tinklers, chimes, shakers, etc, all sound more prominent. Plus I still get the soundstage I love with the M-125’s!

Santana Caravanserai is what I used first, then Art Of Noise: In Visible Silence. Both have lots of those “little” sounds throughout the albums. Then, Sade’s song: Never As Good As The First Time has some sounds that can easily get lost if something isn’t right with setup. In all, there’s a better sense of detail without any harshness. All of this is very good tonight.

My initial impression so far is very good!

Anticables ZERO Autoformer
To those who believe these to be "bandaids", I say this is absolutely incorrect. They are tuning devices, the same as using different types and lengths of speaker cable to suit a particular amp/speaker combination.

Case in point. I found that using longer speaker cable between the M-125 amp and ML 13A speaker resulted in better performance, meaning, better sound and happier and cooler running M-125. But with the ZERO in the chain I needed to delete the speaker cable altogether to find the best performance, again, better sound and happier amp.

And just like using one speaker cable type - design/length - might be great with one speaker/amp combo, it can be totally degrading for another combo. In my case I found that using multi-thousand $$$$ speaker cable to not be as good as good quality generic 14/4 speaker wire with two-pair connections making for a 11Ga equivalent and needing to be at least 9' long. When I tried very short speaker cable it really, really, was a bad idea!! Terrible sound.

I admit I'm still skeptical and must remain so for now, even though last night the sound was awesome. I like to audition for days with something like this just to toss enough musical diversity at it to try and break it. But it seems that the soundstage has filled in with some details which were previously missing or subdued. (Not to be confused with The Subdudes.) And quite frankly, this is exactly the amount of 10kHz level I'm looking for, because much more would be annoying when Triangles and Chimes are played. Right now these are right where I want them to be just using the 2X tap on the ZERO's.

When going up from 2X to 3X what I see when measuring with REW is an upward tilt in both low and high frequencies with the range right around 600-900Hz remaining where it is, at least for my speakers. Don't want to kill the mids.

The comparison between no ZERO and with the ZERO using 2X tap is that the tilt in the lows is subtle and is not near as much as it is from 8kHz and up which is very dramatic at about +3-4dB. So again, this is just what I've been wanting. So to answer the thread title, this trick seems to be a very good one for me!

Also, I question how these ZERO's might differ in design from the autoformers in McIntosh amps? Anybody know?

With no air flow around the amps, after 1-1/2 hours of my test music playing at the test volume the power transformers on the amps definitely run cooler. It takes longer to start rising, and they don't seem to "want" to get hot hot hot. At the 90 minute mark they both got up to 120° as measured on the left side, which is 8° less than without the ZERO Autoformer. Both amps are sporting dual 12BH7 driver tubes, but only one has the 8.2Ω resistor swapped in, even so, both amps are interchangeable in terms of heat from the transformers and quad cap, but, it seems that C16 is now cooler by about 40° in the amp with the 8.2Ω resistor - 150ish° vs 190ish°. But while C14 always runs a lot cooler than C16, in the amp with the 8.2Ω resistor C14 runs warmer by about 20° at around 130° (not exact, but close, forgot to write it down before shutting down the amps).

What is very different now is that I prefer UL instead of Triode mode. I've run these amps in Triode mode for 2-1/2 years, trying UL every now and then just to reconfirm. Now, when switched to Triode, it's just not as pleasant. Singers seem more "IN YOUR FACE" with a tad bit of sibilance instead of just a bit more prominent.

Tomorrow night I'll try the 5963/12BH7 combo instead of 12BH7/12BH7. And I'll change the other amp's 10Ω resistor for the 8.2Ω since I'm pretty sure I like the combination of factors it brings with it.

I love it when a plan comes together!

I swapped from running dual 12BH7's on the driver board to a 5963 in front and a 12BH7 in the rear. I thought I'd just listen for a bit, but I'm on album #5 and really enjoying what I'm hearing.

With dual 12BH7 tubes there is a very slight "edge" to vocals, and also chimes, triangles, etc, where they should just be very clear sounding. That "edge" sound helped give a sense of extra dynamics, but it had me questioning what I was hearing. Tonight I'm not questioning anything except a slight sibilance on some tracks - which I've known to have sibilance but less pronounced - which I should be able to dial out. It might be that I've taken all of the absorption out of the room (loaned to a friend), and haven't yet built the new absorbers, the material for which is in the garage.

So having the 5963 in the front position makes me and the amps happy.

From the suggestions provided here in this thread (thanks to all) I'm using the following, in order of most effective:
AntiCables ZERO Autoformers on the 2X tap.
12BH7 phase splitter.
8.2Ω resistor for R28.

I'd still love to find out what changing the output caps to Mundorf silver-oil would do. I might be willing to do this, but not without knowing what the expectation would be. I've searched to see what difference might be expected, but it was a shot in the dark, nothing substantial came of it.

Thanks to all who helped! I'm not done yet, probably, maybe, but tonight is proving to be right there with what I've been wanting.

ttocs wrote:I swapped from running dual 12BH7's on the driver board to a 5963 in front and a 12BH7 in the rear. I thought I'd just listen for a bit, but I'm on album #5 and really enjoying what I'm hearing.

With dual 12BH7 tubes there is a very slight "edge" to vocals, and also chimes, triangles, etc, where they should just be very clear sounding. That "edge" sound helped give a sense of extra dynamics, but it had me questioning what I was hearing. Tonight I'm not questioning anything except a slight sibilance on some tracks - which I've known to have sibilance but less pronounced - which I should be able to dial out. It might be that I've taken all of the absorption out of the room (loaned to a friend), and haven't yet built the new absorbers, the material for which is in the garage.

So having the 5963 in the front position makes me and the amps happy.

From the suggestions provided here in this thread (thanks to all) I'm using the following, in order of most effective:
AntiCables ZERO Autoformers on the 2X tap.
12BH7 phase splitter.
8.2Ω resistor for R28.

I'd still love to find out what changing the output caps to Mundorf silver-oil would do. I might be willing to do this, but not without knowing what the expectation would be. I've searched to see what difference might be expected, but it was a shot in the dark, nothing substantial came of it.

Thanks to all who helped! I'm not done yet, probably, maybe, but tonight is proving to be right there with what I've been wanting.

I could lend you my Silver oil caps. They probably have around 100 hundred hours on them. I have tried the Silver oils, Jantzen Superior , Evo supreme silver/gold, the Russian caps and the Audiocaps PPT Thetas. I've settled for the Aidiocaps as they seem to be more "punchy" which I like.

Great news ttocs. I am happy for you, but almost want to curse you because now you have me interested in tinkering with my system to try to get just a little better sound. What a hobby we have, but I just can't help myself... Maybe I'll be able to get those snare drums to snap more like they do when listening in person.

It looks like McIntosh builds those autoformers directly into their amps to get the same results that you are describing for some of the more difficult speakers to drive like our stats. I'm not sure if all bipolars have the same issues, but I sure like the sound that comes from these type of speakers.

There is no way to know the sound difference from introducing Mundorf caps as the output caps until you install and listen. They would probably alter the sound more than any single item that you could replace on these amps. Good or bad might depend on the listener. I do know that most of the absurdly expensive amps in the world today swear by these Mundorf silver-oil caps. I think that I'll hold off on them until my amps are due for a major tune-up. Hopefully in 10 years.

Thanks for sharing your experience. I think that I will plan a drive over to the Martin Logan offices and get some face time with one of their engineers to ask them their opinions with the autoformers with their speakers. If they cannot say anything negative, I'll follow your lead and share my experience after installing them. I'm not sure if my ears can pick up the subtle sounds that you appear to be able to detect. Your attention to detail has me curious to how you source your music. Are you listening to vinyl, streaming, combination?

Mike...

pedrocols wrote:

ttocs wrote:
I'd still love to find out what changing the output caps to Mundorf silver-oil would do. I might be willing to do this, but not without knowing what the expectation would be. I've searched to see what difference might be expected, but it was a shot in the dark, nothing substantial came of it.

Thanks to all who helped! I'm not done yet, probably, maybe, but tonight is proving to be right there with what I've been wanting.

I could lend you my Silver oil caps. They probably have around 100 hundred hours on them. I have tried the Silver oils, Jantzen Superior , Evo supreme silver/gold, the Russian caps and the Audiocaps PPT Thetas. I've settled for the Aidiocaps as they seem to be more "punchy" which I like.

Thank you for the very kind and generous offer! For now, I'll keep that in abeyance pending further education on the subject. But first, need more time with the recent changes.

So if one were to try to define how capacitors can change the sound, would it be to describe it as changing dynamics? When you mention "punchy", this is what I thought of.

The caps that came with my kits are the Russian PIO. My goal in thinking about changing the caps is to decipher if a change will be more to my liking or less. Predictions can be tricky with our hobby.