Old school amps - SQ comparisons

[6ix]

Now I know this is entirely subjective, so there is no definitive answer. Plus I know we are biased PG fans here. However I also hope we are open minded and honest enough to appreciate different brands as well. So this is not necessarily about finding "the best", as it is all personal. But opinions are all we have, so they are interesting to share. Also please keep this focused on old school amps, rather than getting into the USA v newer Far Eastern amps. So, with that said...



I've owned various old school amps over the years: PG ZX, M, MS, Rockford ix, Soundstream Reference, Genesis, plus more. There are also lots more amps I have never listened to in real life, but always wanted to. Such as: Zapco Studio, McIntosh, US Amps. So I wonder how these compare as well?

I have never carried out an honest back to back A/B amp test, to really check to see which amps I prefer the sound of. All were perfectly fine at the time. But it is impossible to honestly judge them as each was in a different instal, with different components, all spread out over many years. So fair comparison is impossible in my particular case. My recent blip of loving Rockford amps again is all based on nostalgia, looks, plus their rugged reputation (I ran one back in the 1990s, amongst other amp brands). Some people are still running old ix amps, which have been pounding every day since the early 1990s! That is just staggering reliability! Yet I wonder if these RF ix amps can match the SQ of the other old school amps out there?

I know some people say most amps sound the same, up to a point, so just pick whichever is your favourite shape, most reliable, or cheapest. But on the other hand many people say nothing is built like the old school top tier amps. Certain brands do have an amazing reputation, such as Soundstream Reference. Ok their reputation for longevity does not match their SQ rep

So...


1. Lets hear your personal favourite amps and why.

2. Has anyone carried out a back to back amp test and discovered they love one brands sound more than another? Are there clear sonic differences in your opinion?

3. Does anyone have any thoughts on RF ix landmine amps compared to the other brands? The reason I ask is I can always use my RF on sub duty and another brand of amp for the comps - if the other amp brands are clearly superior sounding? Despite my rose tinted nostalgia of RF I am open minded enough to accept alternatives, so be honest. Zapco Studio, Soundstream Reference, or PG ZX are alternative favourites to use / try.

4. Post up anything related which stimulates relevant discussion

[alehed]

Hi. I have tested a few smaller amplifiers from a few different brands and still think PG amp sounds clearer than the others I tested.
It is of course subjective , but it has nothing to do with the brand. The others sound great but not as clear in my opinion.

Amplifiers in question is.

PG MS275
PG MQ430
PG M50
Rockford Punch 40 dsm
Rockford Prime R250x4 (2015)
Hifonics Odin
MTX Thunder 280
Genesis stereo 60

I tested all of them in my livingroom with smaller bookshelf speakers.

[Eric D]

I wrote this many years ago...

http://www.soundbuggy.com/Eric/Car%20Au ... index.html

It may be an interesting read for some.

Of all the RF amps I have owned, the ix (and DSM) series sounded the best. Nearly as good as PG and other great sounding brands.

If you study the circuits of older RF amps, you will find that they are different. The ix series use the same transistor type for both the positive and negative half waves of their outputs (either PNP, or NPN, I believe NPN). All newer RF amps (x2 series on to today) use complementary NPN / PNP outputs. My guess was that when the switch was made, something else was changed in the design, and the trade off was SQ began to suffer.

[6ix]

Alehed, thanks for your reply. Would you say the difference was tiny and hard to notice, or more obvious? Sometimes in home Hi-Fi you get people talking about differences which are almost impossible to hear.

Eric, excellent info thanks.

It is interesting to note you say "Of all the RF amps I have owned, the ix (and DSM) series sounded the best. Nearly as good as PG and other great sounding brands." That is exactly what someone else told me regarding the ix being the better sounding ones. Although they did not have any technical explanations.

With regard to your review that sounds like a perfect example of ABX to me. So it would be daft to fault your conclusions. However I note you were listening to a newer style ".2" RF amp. It seems clear this newer style is below par compared to the other brand offerings. Yet you rate the older RF "ix" models much more highly. Is this ".2" range from RF the exact time when things started to go downhill? Where does the (newer than "ix" but before the .2) Transana style fit into this picture?

[Eric D]

In my documented A-B comparison, I used a PG ZX500, and an RF 250.2. The results caused me to do further A-B testing in the months to follow, but I never documented it like I did that first example. I A-B tested that same 250.2 with a Punch 60ix. That is when I concluded the ix series were superior.

For example, the following amps use the same basic circuit...

Punch 200x2
Punch 200.2
Punch 225.2
Punch 500a2
Punch 500s
Punch 501s

The x2, and .2 amplifiers are internally identical. Just their heatsink is different. The next generation a2 series are also "almost the same". They use the same amplification circuit, but have a variable crossover instead of the X-cards from earlier models. These amps sound the same. Rockford has been using the same circuit for some time, just changing the features, and the chassis they put it in. I cannot comment on the newest of their amps, as I quit using them after the "T" series.

[6ix]

So if we take PG as the top benchmark for SQ in this case, then we have the less ideal newer RF ".2" amps (as you tested) at the other lower end of the SQ spectrum...

Roughly where in between these two does the SQ of the "ix" fall? Is it say very close to PG, or more halfway between the two benchmarks?

Finally, once the RF ix is installed in a slightly noisier car, will the differences be that noticeable anyway? Thanks for all the details.

[Eric D]

Honestly, I had a hard time determining the difference between the RF ix amp, and the PG. The ix amps really do sound good.

Now, there is one important difference though. Headroom...

Even though RF amps (the old ones at least) were underrated, PG amps of this vintage are VERY underrated.

I once had a pair of Rockford Power 250.2c amps in my car. One for my components, and one for my subs. I then bought my very first PG amp, a used (and abused) ZX450. I installed it in my car just to try it out. The single ZX450 was just as loud AND better sounding than the PAIR of RF amps were.

The Power 250.2 is rated at 125W x 2 into 4 ohms. It has the unclipped output voltage to do maybe 150W x 2 into 4 ohms.

The ZX450 is rated at 75W x 4 into 4 ohms, but it has the voltage to do 144W x 4 into 4 ohms. This is less power than the RF, but not a noticeable amount.

So, if you go with a PG, you get way more power than rated. I have measured other older RF amps, and they are a similar level of being underrated. I have tested the Punch 60 DSM, the 60ix, the 60x2, the 100x2, the 4080, 400x4, and several others.

[6ix]

Excellent info once again. Thanks so much for all the detail.

Back in the day I loved both PG and RF products and I had trouble making a decision between them. So i didn't. I used a PG ZX for my highs and an RF ix on sub duty. I wish I tried swapping them around back then, just for an A/B test. Alas I never did. I was too busy grinning and driving around.

Although my installer at the time made an interesting observation. He said something like; "I've never heard so much control in a subwoofer before when that RF amp is playing. Your ZX amp sounds great on the highs, but that RF amp has ridiculous control!"




Anyway thanks again. Please feel free to pitch in your own observations over the years on which amps you like, or not. It's always interesting to hear peoples views, stories and info

[Eric D]

The Soundstream Class A Picasso is the best sounding car audio amplifier I have ever heard. Not much for power though.

[ttocs]

soundstream amps were some of the smoothest I had heard. One of the brands I was upset I never worked at a shop that carried.

[alehed]

I say the difference was pretty clear on most of them. just as Eric said the PG and the Rockford are some what close, the other ones sounds more dull in comparison.
Then again I'm going to put the RF Prime in my car so non of them sounds bad, just not as good as the PG ones.

I am a bit of a hifi nerd but this test was done on cheap small speakers that sounds well so no exotic ones. And this is my opinion.