Effect of Coupling Capacitor Sizing on a 2230

[ConradH]

Actually I don't think the designers spent a lot of time fine tuning the sound of receivers way back. They did their best with the parts and price point they had to work with. If some minor tweaks can be applied today as the result of better knowledge, I'll happily do it. That said, I'm not in favor of anything that can't be easily reversed to bring things back to completely original.

 

[Hyperion]

With my level of knowledge I would be reluctant to increase the value of any coupling capacitor. However, speaker coupling capacitors are slightly different as I see it, and I would almost certainly try it if I had the opportunity with a suitable candidate.

Local filtering capacitors are a different game, and I feel can have values increased somewhat if desired. Especially if this means the leads of the replacements are no longer having their leads strained, which is often the case with the lead pitch for same value/voltage modern replacements.

 

[Hipocrates]

some minor tweaks

Like go with higher capacitance on speakers coupling and filtering caps... riiight?
Calling that re-engineering... I don't know gentlemen, kind of light use of the term isn't?

That kitten looks like a modded AU-999

 

[ConradH]

Remember that every time you sub a transistor with a modern part, you're wearing the design hat. And heaven help you if you have to sub a FET. As for cap values, I've simulated some Sansui designs where seemingly logical and sensible cap increases didn't have the expected results and Sansui really did know best. I have to believe other manufacturers, Marantz for example, are no different, but that doesn't mean that all changes are undesirable, you just have to do some research and prove what you're doing.

 

[Hipocrates]

Agreed... Actually I have tested some caps values on HK330B(speakers coupling caps)... and finally I went for the original values despite the fact that a lot of people use to go up, because ''sounds better".
My point, those are tweaks as you well said, reversible and fun to try.

 

[hirscwi]

This is exactly the discussion I was hoping for. Very informative and thanks to all.

Ben, thanks especially for the computation. Is it a different formula for F3 if there's an inductor involved?

 

[Leestereo]

20 Hz is for musical information, but don't forget how much a woofer can pump at subsonic frequencies if you don't have a subsonic filter. That could be a significant load on the amp with larger coupling caps. IMO, coupling caps are the wrong place for response shaping because the load isn't well defined, but I'm not the designer, so what I think doesn't really matter.

Agreed, but my point is that a DC coupled amplifier would equally be affected by a subsonic signal and that the capacitor coupled amplifier is not more vulnerable.

 

[Leestereo]

...I also don't like re-engineering any model. The original engineers had something specific in mind when they designed the 2230 and out of respect to their efforts and their design, it should be left as original as possible, so when you listen to it, you're actually listening to a 2230...

...anyone should feel free to experiment on their gear and if you like it... go for it!! It's part of the hobby and fun. Enjoyment is what we're after here!!

There are many different approaches to restoring/repairing vintage stereo components, and if the end result is a component that functions as intended (or better), the approach used is, IMO, respectful of the original design and is equally valid as any other.

I do not consider the use of different, higher specification components (e.g., replacing original low leakage capacitors with a film capacitor) as re-engineering the component or altering the original design objectives. IMO, the "sound" of the vintage Marantz or any other brand is a result of the topology rather than the components used. I think that the original designers would have wanted to use the better parts had they been available or had not been limited by the company's bean-counters (for profit margins). Further, even if one uses the same type of replacement component, the modern equivalent may be quite different from its vintage counterpart, i.e., their ESR, ESL, leakage and capacitance tolerance specifications. Hence, their use does not necessarily result in a component that sounds the way it did when it was originally manufactured.

I agree with @ConradH, and generally avoid any changes that can not be reversed back to the original state, e.g., no trace cutting, chassis modification. Here is an example of a repair that was NOT respectful of the original design and which could only be salvaged by re-engineering: Saving Unican Eric's Philips AG9016 From the Dumpster

 

[ConradH]

OTOH, sometimes I just can't help myself. I did a lot of re-engineering to a friends Sansui 881 because the original design has a hum issue. They just plain didn't use a good ground strategy and it took a few trace cuts to fix it. A certain voicing I can understand and see keeping intact, but listening to hum and calling it the designer's intent doesn't work for me. One could still jumper my cuts and return the thing to the original design I suppose, but under what crazy circumstances would somebody do that? Well, most likely, somebody that didn't understand the original problem would look at the work, call me a butcher, or worse, and put it all back. Then they'd blame the hum on something the previous tech had screwed up, that they couldn't find!

 

[catrafter]

The capacitance of many electrolytic capacitors from 'back in the day' were rated -20/+100%, now, they are usually rated -/+20%.

Tom

 

[KutzlerTrans]

Good thread

On the lighter side
Chris M has never been rude to anyone that i know of, but Brians comment was respectful of the op considering he didn't know Chris's personality. All is cool.

 

[ChrisMarantz]

That said, anyone should feel free to experiment on their gear and if you like it... go for it!! It's part of the hobby and fun. Enjoyment is what we're after here!!

I agree with Randy completely, people are certainly entitled to do whatever they want to do with their own equipment. Audiophiles have a long standing tradition of modding their equipment. It is part of the audio hobby, it's just not the part that I participate in.

IMO, the "sound" of the vintage Marantz or any other brand is a result of the topology rather than the components used.

I think that the original designers would have wanted to use the better parts had they been available or had not been limited by the company's bean-counters (for profit margins).

Further, even if one uses the same type of replacement component, the modern equivalent may be quite different from its vintage counterpart, i.e., their ESR, ESL, leakage and capacitance tolerance specifications. Hence, their use does not necessarily result in a component that sounds the way it did when it was originally manufactured.

While topology is the backbone of every design, the original engineers choices in how to create the design and which components to populate it with go hand-in-hand

If we were discussion a JC Pennys stereo that cost $98.00 then the bottom line would be that largest factor in how the unit was designed and built. I never really buy into the "bean-counter" theory when it involves a high end piece of equipment like a Marantz Receiver.

Modern components certainly have high and more consistent build quality thanks to modern manufacturing. Needing to use modern components is unavoidable in most cases. There's a big difference between choosing modern components that inherently have higher tolerances or naturally better specifications than choosing a component that is many times the original value.

The general wisdom is that. . .

In my opinion, this is the real heart of the issue. I see many many people who make modifications without have any real understanding as to why they're doing them. They just follow along with what everyone else does because it popular that that time. I applaud the OP for actually asking the question before he made his choice. I don't expect every person working on their own equipment to become an audio design engineer, but a little googling and a little reading goes a long way to begin to have some understanding about the choice they are making - Chris

 

[restorer-john]

...I see many many people who make modifications without have any real understanding as to why they're doing them. They just follow along with what everyone else does because it popular that that time....

Yes. I call it "socially acquired herd knowledge". In other words- complete BS.

When did one of the so-called "restoration and upgrade" threads post any actual test results? What about a FR plot before the cap value changes and after? How about some power output and THD tests before and after restoration?

I've seen a number of times where coupling caps have been significantly reduced in value and yet no testing of FR or low frequency THD was done to justify those 'mods'.

 

[ChrisMarantz]

Yes. I call it "socially acquired herd knowledge". In other words- complete BS.

I agree with this, I actually laughed when I read this.

When did one of the so-called "restoration and upgrade" threads post any actual test results? What about a FR plot before the cap value changes and after? How about some power output and THD tests before and after restoration?

I've seen a number of times where coupling caps have been significantly reduced in value and yet no testing of FR or low frequency THD was done to justify those 'mods'.

John, there's clearly no need for testing, every modification I have every read about here has yielded positive results. . . . . - Chris

 

[Blue Shadow]

This discussion includes the necessary talk about the changes expected to the frequency response of the amp, but many AKers see big caps and have decided to blindly increase the size of them because they think they are power supply caps not coupling caps. There are those that make changes and explain them and those that just wield a soldering iron waving it around and doing whatever the recap disease here on AK thinks might work.

Good to see Conrad discussing the lower actual capacitance of new larger caps that meet specs on the low end, too. A definite need to make adjustments for these new caps in older designs, ±20% new caps running about -10% from spec and older caps, mentioned here as -20%/+100% (put I usually see +80%) still a wide range, more probably on the high side of the designated value compared to a replacement new cap.