Vintage Acoustic amps 370 vs 320

johnk_10 · #1 10-22-2011, 04:01 PM

i've had my two vintage Acoustic Control Corp amps (a '75 370 and an '80 320 with two 4x15 408 cabs) for a little while now. i used to own both of these models back in the 70's as well as a 360 rig, and loved all of them so i recently bought these two very clean examples based on my fond memories of them.

they both needed a little work to bring them back up to factory spec (i replaced quite a few electrolytic caps, a few resistors, cleaned all the pots, jacks and replaced a couple of the inductors in the 320's graphic eq section. after installing an adjustable bias on the 370 (they have a preset fixed bias, and adjusting the bias on the 320, they are now running absolutely perfect.

at first, i preferred the 370 (and always did in the past), but now i love them both, even though they are voiced quite a bit differently from each other.

my take on them is this:
the 370 is rounder, fuller, a bit smoother/transparent and actually sounds alot like a tube amp. its low end goes thru the floor and while playing it, it can actually can shake your legs (or any other extremity

) and sounds absolutely HUGE. the 320 on the other hand, has a little bit less extreme low end, but has a faster, thicker mid bass and a more present mid and high end, but also sounds HUGE as well. i kept A/B'ing them back and forth today, and i still can't make up my mind which one i like better. i guess that the only real way to tell would be to use them both on the gig, and i think the 320 might be a bit better suited since it's focused more in the mid bass.

just thought that i'd post this to see if anyone else is hearing the same things that i am between these two cool vintage heads.

and btw, here's a couple of pics of them:

Sav'nBass · #2 10-22-2011, 04:11 PM

Wow I had one of those.. back in the 80s.. I don't remember which one though.. I think it was the one on the bottom in the second pic.. and I believe it was a 301 bottom I used to run it through.. I know it had the EQ on the side.. and I remember only one set of controls.. with 2 inputs.. I couldnt appreciate it then like I would now though.. (ear wise at least.. there is no way I'd even try to schlepp one of those anywhere now...

)

craig.p · #3 10-22-2011, 05:06 PM

One of the things I recall about the 370 head is that its bass control operated at a really low frequency and went sub-audible, too, enough to cause damage to drivers in reflex cabs. Probably not as much of an issue in the FH cabs for which it was designed. But anyway, good to see people keeping these in service and giving them the TLC they deserve. Ah, the good old days when you could actually troubleshoot and repair without having to use en electron microscope to see what the heck you were doing. Someone should start building these again.

What?

Oh.

Never mind.

DerekG · #4 10-22-2011, 05:10 PM

I have my old 150b from 1975 up in my attic. Some day, I'll have to pull it out and plug it into my Aggie GS112s. I wonder how it would compare to my Markbass LMII??

rodl2005 · #5 10-22-2011, 05:25 PM

Do an A/B comparison Derek. Please!
An acquaintance of mine has an old Acoustic cab.
I don't know him well enough to go play it, or know anything much about it, apart from that he told me it was made out of chipboard/particle board 0_o
I will ask about it next time J run into him for sure.

bottomend! · #6 10-23-2011, 01:47 AM

Two different beast' IMHO. One of the advantages of the 320 is the second channel and the ability to blend it with the first channel. If you haven't yet done so - go to your amp and start BLENDING.
The amp truly becomes an astoundingly capable piece of gear so if you have the space ... and ear plugs, set one channel so it distorts and keep the second clean. The manner in which they blend is really functional and they maintain their separation even into full tilt overdrive. For a more indepth description, do a search on me and 320/330 at teh Acoustic forum. I'm sure I blabbed on for a while a few years ago when I first discovered these amps. Running multiples of these (320's and 330's) through multiple cabs may alter the way you interact with your bass permanently. It did for me...

The 370 is simply a wonderfully simple and hard working amp and I personally found my own sonic freedom after I looking at the online manual and tried out the suggested tone settings. At first glance I gaged and winced because they were SOOOOOO extreme - one slider gets maxxed while it's neighbor is fully cut.... that sort of thing. But son of a gun - the old anchor really came to life adjusting it in this manner!

I agree with you about the mids perhaps being more focused on the 320 vs the 370 but the 370's bright switch more than makes up for the deficit in the way that it opens up the top without getting brittle like it can on the 320 when the switch is used. Maybe the the 320's stronger mids could benefit from a higher voiced bright switch?

To me the 370 is more an amp of extremes (a byproduct of the eye-opening look at the manual?) whereas the 320 is a bit more refined in it's purpose.

JMarkD · #7 10-23-2011, 05:36 AM

John, I used both at one time and I totally agree with what you are hearing. The 370 has a huge low end that sounds wonderful in the living room but I often felt would be lost on stage. I gigged the 320 (and 330) for years. I ran it into an Acoustic 2x15 or an EV 215M for many gigs. A very nice amp. Very clean and clear. Never ran it at 2 ohms into a 408. That must be quite impressive.

Sadly, I sold my 320 and 330 and my 370 was stolen. I wish I had at least one of them now.

HOOLIGAN · #8 10-23-2011, 10:05 AM

I own a 370-
Along time ago I remember reading on the Acoustic forum
that you put a dummy jack into the 2nd input & it makes it
louder-I can't remember why, but it works!

someparts · #9 10-23-2011, 10:45 AM

The 370 is more tube-like for sure. I never really dug the 320 - lots more knobs and just seemed power came at differrent voicing - that and the head box was too wide for the 301s and narrow 406 that I ran.

jj4001 · #10 10-23-2011, 11:28 AM

Keep posting about these amps, johnk!

Words cannot describe how much I love what my 320 can do and I hope to keep up and running forever. Perfect amp for a stereo bass. It's nice to be able keep the volume knobs full up on my bass while using each channel's volume knob to blend the pickups to taste. It lets me dial in more bridge pickup without the hum I get from turning the neck pup down on the bass. It's really helpful for dialing in an appropriate tone while gigging in three very different sounding bands with minimal EQ fiddling.

johnk_10 · #11 10-24-2011, 11:59 AM

to give you an idea of the frequency response of the two heads, here's a couple of 10hz-20Khz signal sweep tests that i ran on them using TrueRTA.

first, the 370, with all of the tone controls set at 12 o'clock and the graphic eq set with no boost or cut. you can see that it's pretty flat but starts to gently roll off at around 5-6kHz:

now the 320 with all of the tone controls at noon, with the graphic eq bypassed. you can clearly see that it has a smooth but large amount of boost centered around 6.5Khz:

here's the 320 adjusted as flat as i could get it using just the tone controls with no graphic eq. the setting were:
Treble-just under 3 o'clock
Middle-just over 9 o'clock
Bass- 3 o'clock

and probably the biggest surprise was when i clicked in the graphic eq, but didn't use any boost or cut. you can see that just by clicking it in that there's a pretty sharp rolloff centered around 20Hz, but is also 4db down at 50Hz. the green line is without the graphic clicked in and the yellow line is with it clicked in (but no boost or cut).

**Lazarus.Bird** · #12 10-24-2011, 12:03 PM

Cool stuff john. Always enjoy your threads.

millsbass5 · #13 10-24-2011, 12:24 PM

Man,I sure wish I still had my 370. That amp went to hell and back gigging with me. It suffered a fire at a club,rain & mud while being hauled in the back of pickup trucks. Hell,just think of ANY form of abuse that gigging can dole out,that amp took it in spades. The old adage is true. You don't know want you want till it's gone. Damn,why do musicians always seem to get rid of the great stuff when they're young?

johnk_10 · #14 10-24-2011, 01:09 PM

yeah, they're reliable workhorses alright, and IMO, their rated power is very conservative by today's standards. they aren't difficult to service or repair either should they ever need it. just about the only part that is 'unobtanium' in them are the inductors for the eq, but i found a few substitutes that work perfectly in them should you encounter a bad one.

bottomend! · #15 10-24-2011, 02:50 PM

Your graph for the 320 may explain why I hear "clackyness" when I engage the bright switch. The head already has a rise at 6.5khz and without a horn to balance things out I would imagine the lower octave of this freq gets a boost as well, this combined with a 15" speakers tendency to beam above 1.5 khz (I use a 408 too) just exacerbates the issue.

It's been a while since I've used my head though a cab with anything other than 15's so I'm wondering how much of this is speaker related vs. the amps response.

I wonder if the lows rolling off when the EQ is engaged was engineered in to compensate for something the cab (408) is doing. Do you have a way to measure the cabinet response?

bottomend! · #16 10-24-2011, 02:58 PM

Quote:

Originally Posted by jj4001

Keep posting about these amps, johnk!

Words cannot describe how much I love what my 320 can do and I hope to keep up and running forever. Perfect amp for a stereo bass. It's nice to be able keep the volume knobs full up on my bass while using each channel's volume knob to blend the pickups to taste. It lets me dial in more bridge pickup without the hum I get from turning the neck pup down on the bass. It's really helpful for dialing in an appropriate tone while gigging in three very different sounding bands with minimal EQ fiddling.

The cool thing I've found about blending channels is that there is almost zero "cross pollination" of the two. They remain separate and clear no matter when the control are set. It's very unique to be able to "layer" the two sounds on top of one another without them completely bleeding into each other. Glad to see another 320/330 fan on TB!

jj4001 · #17 10-25-2011, 08:31 AM

So true. It does sound like two basses playing in perfect unison. It works very nicely in a three piece band.

Also, seeing the 320's response reading comes as no surprise. I've had to be careful with the midrange knobs on the preamp side. If I turn them up too much, it makes the speakers in my 402 chirp when I play the 5 and 7th frets on the D string. I was really worried about my speakers until I noticed it having the same effect on an Ampeg 8x10.

**garmenteros** · #18 10-25-2011, 11:28 AM

Quote:

Originally Posted by DerekG

I have my old 150b from 1975 up in my attic. Some day, I'll have to pull it out and plug it into my Aggie GS112s. I wonder how it would compare to my Markbass LMII??

Excellent head... I owned one for a while and hooked it up to my mesa1000 and it was really loud for its rated 100 something watts. It will sound way more bass heavy in comparison to your little mark thats for sure.

**garmenteros** · #19 10-25-2011, 11:32 AM

Quote:

Originally Posted by HOOLIGAN

I own a 370-
Along time ago I remember reading on the Acoustic forum
that you put a dummy jack into the 2nd input & it makes it
louder-I can't remember why, but it works!

I don't know why anyone would need that amp to get louder... it is insanely loud.

jj4001 · #20 10-25-2011, 12:47 PM

Quote:

Originally Posted by garmenteros

I don't know why anyone would need that amp to get louder... it is insanely loud.

Must be like the "power boost" switch on the 320. This switch is always good for laughs. I mean, this amp keeps up with two 100 watt Marshall half stacks with the volume set to 2.5. I can't imagine someone actually needing to use it.