Tube amp re-cap info needed

[HarryO]

I'm getting ready to re-cap an old Heathkit AA-111 amp and thought I'd ask about the sound of different caps that have been used around the forum. Anyone have any experience with different .1 400V caps in the old Heathkits? I've looked at the different caps around for different prices and wondered if the sound vs. the buck is that critical in these old amps. I've not done one of these old amps except using basically stock replacements before.

Thanks,

Harry

[Erik Mandaville]

Lots of .1uf caps, which is a common coupling cap value.

Jensen

Hovland

Solen

Kimber

Orange Drop

too many other mylar to even list.

What you might want to try, if you're familiar with the process, is simply tack-solder different examples of that value and listen. I use the same value in our Moondogs, and have tried enough to make me tired of the ubiquitous capacitor upgrade. I settled on Sprague Orange Drops. Lots of builders like them, and some don't at all. I have a friend working on a PP 2A3 amp desiged by a highly experienced technician who thinks highly of Solens. Just one of those things you have to try for yourself to find what you like.

Interstage caps are often used between the plates of one stage and grids of the next, so be careful.

Erik

[HarryO]

Thanks Erik,

I've used the orange drops and personally don't care for them with high efficiency horns. They made the horns pretty harsh the only two times I've used them. They seem pretty good on the bottom end but not for me. I thought about using the Hoveland caps. Price isn't bad on them either. Less than $6.00 each. I'm sure there's plenty of $1.00 caps that sound good but I've been wanting to try some of the "high dollar" caps to see if I can justify the difference in price. I guess it's like tube sonics and everyone's going to have their own preferences.

Since I'm replacing them all I'm changing them to .22uF 600V and keeping the values of the cans where they are. Do you forsee any problems there?

Harry

[consistent]

Hi, I have been playing around with caps for a number of years in pre-amps and amps and found that these sites helped http://www.10audio.com/sonicap_oimp_multicap.htm and http://www.humblehomemadehifi.com/Cap.html where I found that the Sonicaps were the best value followed by Mundorf then Hovland.

They are all a little different when you put them into a system that allows for differentiation (your can hear it). The Hovlands had a very clean and detailed sound where the Sonicap and Mundorf had greater depth in the bottom octaves as well as the staging. Buy a few and play.

Cheers

[sparrow]

Hovlands are good, but are hard to predict. Sometimes they sound superb, and at other occasions did not sound good. Kimber is not very suitable. Auric Caps are pretty good. Love the Jensens, and my current favorite is of course Mundorf Silver/Oils. If cost is not a problem, the Mundorf Golds are probably the most natural sounding caps I have heard. Finally, there are the V-Cap teflons! I have not had the financial flexibility to use them, but have heard great things about them. You can also try the Rel Cap Teflons, somewhat cheaper than V-Caps? If it was I, would probably stick with Jensens and Mundorfs.

[Erik Mandaville]

We all hear differently, and I curiously found the Hovlands to be overly bright and slightly harsh compared to the orange drops. I would suggesting experimenting a bit to find what works best for you.

[HarryO]

This little Heathkit AA-111 looks to be basically a Dynaco board amp. All parts are easily accessable. I talked to a couple of local tech buddies of mine for their advice also. Their opinions were about the same as here on the forum. Who knows what sounds best. It's a personal preference.

I've done the recap twice now. I used the Orange Drops the first time for the price and I could get them locally. I didn't like the way it sounded at all. Shallow and it seemed like I lost some of the music and "feel" of the music. Not exactly scientific. Sorry. I gave it approximately 25 hours and re-did it with Sonicap Platinums. Maybe a bit overkill for a $300 amp but I like the sound now. Much sweeter to my liking, better detail all the way through the range and not harsh at all. I don't have a lot of time on it yet as the new preamp is taking much of my attention right now but in my Heathkit AA-111 and horns the Sonicaps are a good fit so far. A lot more expensive but it's an amp worth listening to now. Cheap works sometimes but not in this case for me. I wish I had extra time to try a half dozen different brands so I could learn more about the sound characteristics of each brand but it would probably vary with each application anyway.

As I do more amps I'll be using different brands just to hear the differences. I guess it's like anything else in audio that when you make one change everything changes.

I'm still looking for the "magic wand" to make everything easy and sound good. Pretty elusive. I'm not holding my breath.

Thanks again,

Harry

[Audible Nectar]

Those Sonicaps improve even further after 300-500 hours of listening time. They become more transparent through the break in. If you like them now, you'll like them even more with use.

[Groomlakearea51]

Anybody help me on this related question?

On the Sonicaps; there are three "flavors", Gen-I, Gen-II and Platinum.

Two Questions:

(1) Notwithstanding that the Platinum are premium grade, what about the Gen-I vs Gen-II?

(2) According to www.soniccraft.com, there is a difference between the two,; here's what they say: "The Gen I is basically a fairly balanced capacitor. However, some find our "balanced" slightly thin and bright compared to the more lush "colored" capacitors which would include the Gen II. While the Gen II has a nice Midrange bloom, Gen I has a slight advantage on the freq extremes (top and bottom). In many applications, larger values of Gen I bypassed with smaller values of Gen II yield a very favorable result." What do they mean by this?

Other Info: I'm looking at the Platinums, but maybe, maybe not. The application is for a 2 channel, tube amplifier that calls for four x .33uf x 400v caps. Tubes will all be US made NOS 6L6GC's x 4; 5 x 12AX7's; 2x 12BH7's; and 1 x 6AQ8 (that one may be a Telefunken, depends on price factor at the moment).

[Erik Mandaville]

What do they mean by this?

In general, that not all people will perceive the sound attributed to a specific component or passive part in the same way (as in the "balanced" G I example). Bypassing larger values with smaller values are said to sometimes improve high frequency transient response/speed (aka: HF frequency response), and also perhaps provide the added advantage of better ESR values than the single larger capacitor by itself. What it seems they found at sonicraft was that the Gen. II capacitor, which was described as more lush rather than bright and lively, was 'helped' in the frequency response dept. by bypassing it with a smaller value. I did the same thing with some obviously sort of muddy sounding (but expensive) oil coupling caps I had, and bypassing it with a .1uf poly tubular capacitor seemed to help. Another common practice is to bypass electrolyitc capacitors with small value solid dielectric types. I tried both in my preamp and noticed no difference whatsoever.

.33uf for your stereo amp project is a common value, and there are many types you can try. The one that sounds the best may not be the most expensive you can find, and then again it just may. It boils down to the sound you prefer despite the cost factor.

Erik

edit: Sorry, I meant that the bright Gen I bypassed with the more lush Gen II seemed to tame the less-easy-to-listen-to characteristic of the Gen I, and thereby making what for some was initially 'thin' and 'bright' more balanced. Lots of builders I've communicated with look at the coupling cap element as a way to voice a component to a personal preference. You might be surprised at how many builders with decades of experience still like Orange Drops or Solen. I liked the sound of much more expensive Jensen PIOs in the parafeed amps I made a few years ago, which were not as edgy in that already 'fast' sounding amplifier as Hovlands, Kimbers, and some others I tried. Inexpensive Orange Drops are what I have in my modified Moondogs SET amps, but I have 2uf Hovlands in my preamp. What you prefer is the ticket, and I find cost simply coincidental.

[Marvel]

I was thinking that the definition of 'bypass' might be in order as well. This would mean that the regular value of capacitor in the circuit has the smaller bypass cap in parallel with it, to modify the performance characteristics. In your case, you might find an improvement by placing a .1µf cap in parallel with the .33µf that is called for in the design.

Bruce

[Erik Mandaville]

Here you can see the yellow Hovlands paralleling the two light blue electrolytics. I forgot how many different capacitors I tried in this preamp, and the Solens seen in the lower bottom are the 2uf caps on the output. The orange drops are coupling the two 6SN7s in each channel. The orange drops remain, the Solens were replaced by same value Hovlands another forum member gave me as a gift. They sound nice; I left them in.

Erik

...built when I still insisted on using silver-plated copper with Teflon. Thankfully I've gotten beyond that. And: I tried the same circuit with a vacuum tube rectified power supply, and the dual solid state rectifiers with the four large-value electrolytics were not slightly, but MUCH better. Regulated DC filament supply like the Moth 2A3 amp I put together = very, very quiet performance. Granted this is far less complex than a Klipsch type 'A' crossover, but what can I say....

[Erik Mandaville]

And this little guy as another example of where more expensive "audio grade" capacitors did not perform as well for me than the rectangularly-shaped blue coupling capacitors seen on either side toward the top of the picture. This small amplifier, with an opening on the bottom that's about the size of my multi-meter, was completely gutted and rebuilt as shown. I initially used, what was the value, .27uf, I think, coupling capacitors from Sidereal (which even indicate on the cap itself that they are 'premium audio capacitors') and the sound was not right. After a little while and a couple of other experiments, including 600v .22 uf Kimber caps, which I also didn't care for, I replaced them yet again with the blue ones mentioned above. .22uf mylar, which is a material audiophiles are supposed to treat like bubonic plague. However, in this circuit, a single-ended 4 watt 6BQ5 amp, they, to me are very balanced top-to-bottom. The amp is wonderful with Klipschorns, and one I've also modified, by removing the volume control and installing fixed grid leak resistors and a headphone jack, to be used as an excellent headphone amplifier.

The best capacitor may not be the one that cost the most, but in some cases it may. Not in this case.

[Erik Mandaville]

And this little guy as another example of where more expensive "audio grade" capacitors did not perform as well for me than the rectangularly-shaped blue coupling capacitors seen on either side toward the top of the picture. This small amplifier, with an opening on the bottom that's about the size of my multi-meter, was completely gutted and rebuilt as shown. I initially used, what was the value, .27uf, I think, coupling capacitors from Sidereal (which even indicate on the cap itself that they are 'premium audio capacitors') and the sound was not right. After a little while and a couple of other experiments, including 600v .22 uf Kimber caps, which I also didn't care for, I replaced them yet again with the blue ones mentioned above. .22uf mylar, which is a material audiophiles are supposed to treat like bubonic plague. However, in this circuit, a single-ended 4 watt 6BQ5 amp, they, to me are very balanced top-to-bottom. The amp is wonderful with Klipschorns, and one I've also modified, by removing the volume control and installing fixed grid leak resistors and a headphone jack, to be used as an excellent headphone amplifier.

The best capacitor may not be the one that cost the most, but in some cases it may. Not in this case.

[HarryO]

That's nice work Erik. Clean and neat job.

Experimentation and playing wih the different brands seems to be paying off.

Now a quick question or two. On the different brands of caps, Do you know them well enough to expect certain results out of them in certain applications or is it always a "crap shoot" when playing with the caps?

Harry

[Mike Lindsey]

Hi Harry,

You should email Ki Choi as he has restored over 50 of the Heathkit amps, and has them all sitting in a closet in his audio room. []

He's been restoring these things since he was a kid...

Mike

[Groomlakearea51]

I think Harry has a good question. From a general point of view, regardless of cost, etc. reviews of "types" by brand, and their "tendencies" to "bright", "fast", or "lush", would be quite interesting. A better understanding of what are the general characteristics of some of the wide array of possible caps would really help many of us new to the tube amps.

Here's a few more questions that have cropped up as I wade through the different manufacturers' cap listings:

(1) What voltage values should you not exceed, or for that matter, go under? As an example, the amp's schematics shows four .33uf /400v. Say you identify a particular brand that you want to try, but they only have .33uf at 450 or (much more common) 600. In other words, from a mechanical/ electrical point of view only, what happens if you use a .33 at 600v in this case? Is that possible, or not recommended.

(2) As an example, given two caps under consideration, one is brand X is 400 and the other brand Y is 450, can you use either? and what's the potential effect on the sound, if any?

(3) Given that the four .33's will be replaced (they are the $1.99 specials that the previous owner put in...), and given that all the tubes will be "new", I can or should assume that the other caps should also be replaced?

(4) I understand "lush" and "bright", but what do they mean by "fast"?

To be sure, I am intrigued with the parallel caps arrangement. But insofar as this is the first tube amp I have ever owned, I do want to start with a good quality "baseline", or a reasonably predictable configuration until my ears, my brain, (and my wallet....) have a better understanding as to how the caps (and tubes...) and their characteristics affect the sound.

Thanks Eric, Bruce, Harry for your posts, and special thanks to those who have emailed me about this. Again, I really appreciate everyone taking the time to discuss these issues. Everyone is very, very helpful and very informative. Please bear with me. I've only used ss for 35 years, and have waited forever to obtain that particular tube amp that I always wanted to use with a pair of Klipschorns. The "stereo room/ man cave/ home office" is getting near to completion, and I'm almost finished with the Klipschorns in the workshop that will go in there with the amp [])

[Erik Mandaville]

Honestly, it really doesn't matter how long someone has been doing something, What matters is what you hear and your own response to that. A capacitor can have a certain sonic signature in one component, and sound different still in another; and we all, regardless of years of experience, are still bound by the fact that we don't hear and perceive sound the same way.

Erik

[Erik Mandaville]

(1) What voltage values should you not exceed, or for that matter, go under? As an example, the amp's schematics shows four .33uf /400v. Say you identify a particular brand that you want to try, but they only have .33uf at 450 or (much more common) 600. In other words, from a mechanical/ electrical point of view only, what happens if you use a .33 at 600v in this case? Is that possible, or not recommended.

(2) As an example, given two caps under consideration, one is brand X is 400 and the other brand Y is 450, can you use either? and what's the potential effect on the sound, if any?

(3) Given that the four .33's will be replaced (they are the $1.99 specials that the previous owner put in...), and given that all the tubes will be "new", I can or should assume that the other caps should also be replaced?

(4) I understand "lush" and "bright", but what do they mean by "fast"?

To be sure, I am intrigued with the parallel caps arrangement. But insofar as this is the first tube amp I have ever owned, I do want to start with a good quality "baseline", or a reasonably predictable configuration until my ears, my brain, (and my wallet....) have a better understanding as to how the caps (and tubes...) and their characteristics affect the sound.

Sure.

1) The voltage spec. takes the working voltages of the component into consideration, leaving some room at the high end for safety. If the schematic says .33uf at 400VDC, using a 450V cap is absolutely fine. Same for 600V. Many solid dielectric capacitors can withstand higher voltages than what they're rated for, but it's best IMO to stay close to what you need for a reasonable safety margin.

2) The voltage rating wouldn't really influence the sound.

3) I wouldn't assume the other caps need replacing just because the owner used inexpensive ones for interstage coupling. Those are signal capacitors, where some of the others in the amp have other functions related to power supply. But even there, some builders like using, for example, oil capacitors as the input to filter capacitor after the rectifier (in a vacuum tube rectified amp), with the belief that they can sometimes impart that sort of rich, liquid quality preferred by some. Others think that sound is euphonic.

4) Good point. The term 'fast' is sometimes used simply to describe good frequency response, particularly on the high end. In my case, I have to chase my amps around the room before they let me catch them to play music.

Erik

[Erik Mandaville]

And quickly:

Other areas the might need some attention are the power supply filter capacitors (electrolytic). Where those can effect the audio is when, if not in good shape, will cause a number of problems. However, I have an Audio Express article about one person's rebuild of another Heath amp, the W-5M, where he describes the reconditioning of 20 year-old filter caps. It's just a matter of slowly bringing up the current to the amp using a Variac. There were times in the past where less experienced builders would scoff in doubt about the effectiveness of that, but I know too many people with vastly more experience than myself who do that on a regular basis. It works. In my case, a teacher friend once gave me an old Sears radio console that was built during the second world war. He said he hadn't touched the thing in decades. I brought it home, plugged it in (I should have used a variac -- I didn't), and was amazed by not the sound of the radio, but by the fact that it was completely hum free, and that all working voltages were just where they should be within a certain tolerance. Old electrolytic caps are not automatically bad.

In any event, the Audio Express builder, with more than 30 years of electronics building and experience under his belt, rebuilt the Heath amps for about $65.00. And for this one, we should probably fasten our seat belts: He suggests Solen capacitors for coupling between stages. One can of course choose to use whatever one wants, as well as spend whatever one wants. Whether the investment results in an improvement will be subjective.

You might also consider replacing, if you have hum or other problems, the power supply filter capacitors, as well as possibly the cathode resistor bypass caps, which are also usually electrolytic types. Even those have followers of Elna Cerafine and Blackgate, both of which I have used myself on many different occasions, but now use less expensive alternatives because I can't hear the difference.

If you would like that Audio Express article just for general reading interest (they are educational and helpful), I'd be happy to send you the issue with the Heath amp rebuild. Copying is too much of a hassle; you can have the magazine.

Erik