The Acoustic Club

[D.M.N.]

Put the 360 preamp through its paces last night at rehearsal. Since I'm still working on the power amp (have new caps on order as the originals were giving me weird readings) and I'm still waiting for the replacement L187 I'll be picking up, I ran the 360 into a Peavey 800 Booster and then one of my Sunn 2000s cabs. It's certainly a different sound than my main amp, the 2000s it's sitting on top of, and the Hiwatt to the right. Still dialing in the controls, but it strikes me as pumping out more in the low mids, which is not something I ever felt the 2000s was lacking. I could really feel the air coming off the speakers. As of right now I do still think I prefer the clarity in the upper mids of the Sunn and Hiwatt, but the tightness and punch of the Acoustic is fantastic. Which means they'll probably combine great, using the Hiwatt into a 4x12 for my highs and overdrive. Or the Sunn and cab, but that's two very big rigs, the Hiwatt/4x12 is probably more portable.

Which does lead me to a question regarding the crossover network on the terminal strip at the bottom of the 361 cab. There's a schematic in the 360/361 manual dated 9/22/71 showing a crossover network before the external speaker jack with two 50uF caps. I read that this acts to roll off the low-end in order to use another cab for high end definition. Does anyone know what the ohm ratings are supposed to be for this set-up? I know the L187 is nominally 3 ohms, but how low can the power amp handle? Plugging in another 4 ohm cab? I don't see any mention of extension cab specs in the manual. I've also seen examples of cabs that have a grey cable going from the jack on the top of the power amp straight to the ext speaker output, and without the cross over network. My cab doesn't have that grey cable, but does have a jack. Any ideas on the proper setup for the power amp and speakers? Just want to make sure I don't damage anything when I have the amp back up and running.

So does anybody know the story of how ACC Acoustic went under in the 1980's?

I've never read a good explanation of what happened to ACC. From the 1970's and early 1980's they were dominant in the market, they had great distribution (almost every store carried their products), great artist endorsements, and a great reputation for sound and reliability.

IIRC they went away circa 1986 which was just at the dawn of the "hi-fi" 4x10" era, at that time most bass amps were still based on single or double 15" setups.

There was a big recession in the early 80's (something fans of the Raygun never seem to remember) but that didn't seem to sink any of the other major brands.

I looked around at some other ACC fan sites and not much really there about the demise of the company.

One site suggested they went under in 1983 but I know the products were still in the stores circa 1984 - 1985 and they had introduced a lot of new products and a new look for the small amps (brown tolex).

Seems like the later stuff, Hartke, SWR, Eden that came to dominate the market came to prominence AFTER ACC was gone.

So it's not like they were trying to sell old school products against new style competition.

Anybody have some insight on what actually happened?

It's of course a very well known fact Steve Rabe left to start SWR but I don't know if that was because the company was going under or Steve just wanted to start his own company.

Seems like in the 1970's and 1980's there were a lot of buyouts of amp companies by large corporations, seems like surely ACC would have been an attractive target for say Norlin or the like.

It's almost like they were a big thing in bass amplification and then suddenly they were gone....

Analogeezer

Can't say I know anything on the matter, but they seem to go under right around the same time Sunn petered out as well (though they were bought by Fender and had one last post-80s gasp), as well as a difficult period for Ampeg (purchased by MTI and then SLM in '80 and '86, respectively).

 

[DJ Bebop]

View attachment 4532761

Put the 360 preamp through its paces last night at rehearsal. Since I'm still working on the power amp (have new caps on order as the originals were giving me weird readings) and I'm still waiting for the replacement L187 I'll be picking up, I ran the 360 into a Peavey 800 Booster and then one of my Sunn 2000s cabs. It's certainly a different sound than my main amp, the 2000s it's sitting on top of, and the Hiwatt to the right. Still dialing in the controls, but it strikes me as pumping out more in the low mids, which is not something I ever felt the 2000s was lacking. I could really feel the air coming off the speakers. As of right now I do still think I prefer the clarity in the upper mids of the Sunn and Hiwatt, but the tightness and punch of the Acoustic is fantastic. Which means they'll probably combine great, using the Hiwatt into a 4x12 for my highs and overdrive. Or the Sunn and cab, but that's two very big rigs, the Hiwatt/4x12 is probably more portable.

Which does lead me to a question regarding the crossover network on the terminal strip at the bottom of the 361 cab. There's a schematic in the 360/361 manual dated 9/22/71 showing a crossover network before the external speaker jack with two 50uF caps. I read that this acts to roll off the low-end in order to use another cab for high end definition. Does anyone know what the ohm ratings are supposed to be for this set-up? I know the L187 is nominally 3 ohms, but how low can the power amp handle? Plugging in another 4 ohm cab? I don't see any mention of extension cab specs in the manual. I've also seen examples of cabs that have a grey cable going from the jack on the top of the power amp straight to the ext speaker output, and without the cross over network. My cab doesn't have that grey cable, but does have a jack. Any ideas on the proper setup for the power amp and speakers? Just want to make sure I don't damage anything when I have the amp back up and running.




Can't say I know anything on the matter, but they seem to go under right around the same time Sunn petered out as well (though they were bought by Fender and had one last post-80s gasp), as well as a difficult period for Ampeg (purchased by MTI and then SLM in '80 and '86, respectively).

For some reason, I still lust after a 200s bottom

 

[JacklegBass]

View attachment 4532761Which does lead me to a question regarding the crossover network on the terminal strip at the bottom of the 361 cab. There's a schematic in the 360/361 manual dated 9/22/71 showing a crossover network before the external speaker jack with two 50uF caps. I read that this acts to roll off the low-end in order to use another cab for high end definition. Does anyone know what the ohm ratings are supposed to be for this set-up? I know the L187 is nominally 3 ohms, but how low can the power amp handle? Plugging in another 4 ohm cab? I don't see any mention of extension cab specs in the manual. I've also seen examples of cabs that have a grey cable going from the jack on the top of the power amp straight to the ext speaker output, and without the cross over network. My cab doesn't have that grey cable, but does have a jack. Any ideas on the proper setup for the power amp and speakers? Just want to make sure I don't damage anything when I have the amp back up and running.

Are you sure they aren't 100uF caps? That's what my schematic calls for and I've got a picture of a 361PP with two 100uF caps on the side-mounted multi-lug terminal strip. They're wired together in series with the two negative leads joined to yield a 50uF non-polarized effective capacitance. The high-pass crossover frequency of the output is spec'd at 300Hz into a 4-ohms load.

Acoustic used to publish the impedance of Cerwin-Vega 18-inch speakers at 3.2 ohms. The 370 was spec'd to handle down to 1.6-ohms, the equivalent of two 301 bottoms. The 360 had four(!) preamp output jacks so it could handle up to four 361PP cabinets directly with no need to parallel them from one power amp. The 361PP has a 5-ohm/100W resistor in series with those two crossover caps that was to limit the loading effect on the power amplifier.

 

[D.M.N.]

Here's the schematic as it appears in my manual, but decided to double check, and in the amp, you are correct, it's two 100uF caps. So either it's an incorrect schematic or they changed specs at some point. Mine does not have the 5 ohm resistor though, just the two 100uF caps

However, I then took a look just at the schematic for the power amp itself, dated 7/30/68, and it does show the 100uF caps at 150v with a 5 ohm resistor. So I'm going to guess changing specs during production run? It looks like those caps need to be replaced, I can see some leakage on one, and when I do that, I'll likely go ahead and add that 5 ohm resistor in per the original spec. Thank you for the help in sorting that, and the impedance load information!

 

[JacklegBass]

Well I had to do some digging on this one. I didn't have that 361 wiring drawing you posted, but I knew I had seen it somewhere. Finally found it in 260/261 documentation. The 261 guitar cabinet (the one with 2x15-inch Altecs and the blue Atlas HF horn) has virtually the same HF network drawing with two 50uf cap values and no series 5-ohm resistor. According to the 260/261 documentation, the network frequency with the two 50uf caps was 800Hz. The Atlas horn was 8-ohms.

Just so happens I have the 261's Atlas HF horn in a standalone enclosure with the same 800Hz high-pass network. It's a model 700, a rare product Acoustic only made for a short while in 1971. Hmm, that coincides with the date on your drawing, which leads me to think that during the last year of the 361PP's production they may have raised the high-pass output frequency to 800Hz in 1971 in order to match up with that 700 horn similar to what they had been doing in the 261.

I wouldn't worry about the 5-ohm resistor. I went back and looked at the picture I had of a 361PP terminal strip with 100uf capacitors and didn't see a resistor there either. I'm guessing they discontinued it after the 360/361 manual was written.

 

[D.M.N.]

Well I had to do some digging on this one. I didn't have that 361 wiring drawing you posted, but I knew I had seen it somewhere. Finally found it in 260/261 documentation. The 261 guitar cabinet (the one with 2x15-inch Altecs and the blue Atlas HF horn) has virtually the same HF network drawing with two 50uf cap values and no series 5-ohm resistor. According to the 260/261 documentation, the network frequency with the two 50uf caps was 800Hz. The Atlas horn was 8-ohms.

Just so happens I have the 261's Atlas HF horn in a standalone enclosure with the same 800Hz high-pass network. It's a model 700, a rare product Acoustic only made for a short while in 1971. Hmm, that coincides with the date on your drawing, which leads me to think that during the last year of the 361PP's production they may have raised the high-pass output frequency to 800Hz in 1971 in order to match up with that 700 horn similar to what they had been doing in the 261.

I wouldn't worry about the 5-ohm resistor. I went back and looked at the picture I had of a 361PP terminal strip with 100uf capacitors and didn't see a resistor there either. I'm guessing they discontinued it after the 360/361 manual was written.

Now that is some sleuthing! Interesting, and it makes sense given the date that they likely changed it to work with the new product. I actually purchased the manual from Musicparts, since all the free schematics I could find posted on the web were missing page 24, which showed the crossover and terminal strip wiring. So when I replace the caps, I'll go with the original value of 100uF. The 300Hz would seem much more useful for going into a 4x12 or other extension cab.


I also think I've sorted the rest of the wiring out in the cab. Mine is missing the jack for the out on the back of the cab, but it appears someone has moved the output jack and cable to the input, as input jack has brown cable attached that goes straight to the crossover terminal strip. If what I'm seeing on photos is correct, the input jack should be attached to a Grey cable that goes straight to the 1/4" jack in the top middle of the power amp. from the power amp, there are two clip connectors, one of which goes to the power cable on the back of the cab, and the other of which goes to the terminal strip to split the output signal to the speaker and through the crossover and then to the back panel. Glad I've had time waiting on parts to sit and go over all the wiring and make sure it's all correct!

I guess my only other question is, for the 360/361 combo, is the power amp essentially set to wide open all the time, allowing the preamp's volume knob to function as the sole volume? As in, there is no control over the power amp's volume, you're just controlling the preamp's output.

 

[JacklegBass]

It sounds like you've got it right. Originally there were two brown lamp cord-type cables, one for bringing incoming AC power down to the chassis and the other for bringing the high-passed speaker signal from the terminal strip up to the back panel Output jack just under the pilot light. Then there was a shielded instrument-type cable lead from the Input jack running down to under the chassis and feeding up through a chassis hole and soldered directly to the back (foil side) of the power amp board.

You are correct that there's no master volume, it's basically wide open.

 

[D.M.N.]

It sounds like you've got it right. Originally there were two brown lamp cord-type cables, one for bringing incoming AC power down to the chassis and the other for bringing the high-passed speaker signal from the terminal strip up to the back panel Output jack just under the pilot light. Then there was a shielded instrument-type cable lead from the Input jack running down to under the chassis and feeding up through a chassis hole and soldered directly to the back (foil side) of the power amp board.

You are correct that there's no master volume, it's basically wide open.

Perfect, I'll use one of my old spare cables and fashion a proper connection to the power amp then, and leave the two lamp cord cables as is for the time being. Once the new caps arrive I'll get them wired up and prepare to get the new speaker in. I was initially looking at a JBL E155, in part as I have JBLs in 90% of my other cabs, and I appreciate the high end in them, but as luck would have it I should be getting a proper L187 courtesy of @bottomend! with one of the last US made CV recone kits installed. And that should really put a bow on it! Can't thank y'all enough for the help, it's greatly appreciated.

On a side note, when I was using it at rehearsal last night I could hear an oscillation most of the time, and especially when I kicked on my gain and wah. Thought I'd have to spend more time on the bench chasing that down. Luckily, however, it appears the source was actually my Univibe on my board, some issue with the pedal power supply, so that's a relief, and much easier to fix!

 

[Syncopation]

Help Needed.
At band rehearsal yesterday I was playing through my 126. All was well then I heard some static hissing and the bottom end dropped out of my tone. Everything works on the amp but the bass control. When I turn it, it does nothing.
Any ideas?
Thanks in advance!

 

[JacklegBass]

Help Needed.
At band rehearsal yesterday I was playing through my 126. All was well then I heard some static hissing and the bottom end dropped out of my tone. Everything works on the amp but the bass control. When I turn it, it does nothing.
Any ideas?
Thanks in advance!

That's unfortunate. The bass control consists or just three parts, the 100K-ohm rotary potentiometer, the L401 1.5Hy inductor, and a 1K-ohm 1/4W resistor. One of them has probably failed or come loose from the board.

 

[Syncopation]

That's unfortunate. The bass control consists or just three parts, the 100K-ohm rotary potentiometer, the L401 1.5Hy inductor, and a 1K-ohm 1/4W resistor. One of them has probably failed or come loose from the board.

Thanks. I'll pull the chassis and see what I can see. Are these parts that can be obtained?

 

[JacklegBass]

Are these parts that can be obtained?

The resistor can be gotten anywhere, but of course that's the least likely of the three to be bad. A new 24mm 100K linear potentiometer could probably be adapted, but you'll never find one with the same double-flatted shaft to mate with the original knob. The most likely part to fail is the inductor, and of course that's been unobtanium for many years. Hopefully it just come loose from the board and just needs re-soldering. If it's failed internally you'll need to scavenge a part from a donor chassis.

 

[Doombuggy68]

I started a post in another forum and was directed here.
I opened my 301 and was a bit shocked to find it had a weird 8 ohm Fender replacement speaker replacement with 2604 printed on it and its made in Japan? It looks to be aluminum frame, its a solid speaker replacement, no idea what it came out of and Id leave it but I need a 4 ohm to go with my 370 head and other Acoustic heads 220 and 320.
I haven't looked into it yet but thought Id ask some of you. I'm not up on the cab measurements and math. I guess I could track down a Cerwin Vega? ideas?

 

[StereoPlayer]

I started a post in another forum and was directed here.
I opened my 301 and was a bit shocked to find it had a weird 8 ohm Fender replacement speaker replacement with 2604 printed on it and its made in Japan? It looks to be aluminum frame, its a solid speaker replacement, no idea what it came out of and Id leave it but I need a 4 ohm to go with my 370 head and other Acoustic heads 220 and 320.
I haven't looked into it yet but thought Id ask some of you. I'm not up on the cab measurements and math. I guess I could track down a Cerwin Vega? ideas?View attachment 4561776 View attachment 4561778

The Cerwin Vega would be tough to find. But I'm sure there are accepted replacements. @JacklegBass could probably help. He'll be along soon to help as well as others. I'm very lucky to have my original CV speaker in mine.
Welcome to the club!

Your Acoustic head will work at 8 Ohms too. But I would want a better speaker in that cab too.

 

[JacklegBass]

I don't have a lot to add. When I got my current 301 cabinet it was loaded with an Eminence Professional Sigma Pro 18A-2. I eventually found a blown original Cerwin-Vega AC188L which I bought and sent off to the now-defunct Orange County Speaker for reconing. Might be my imagination, but it seemed to me that the restored CV sounded better than the Sigma, fuller, but that's not to say the Sigma didn't sound OK because it did. The Sigmas are still available, but they're 8 ohm too, so it would be a lateral move from the Fender in that regard. If the OP wants to pour the bucks into something new then Eminence has the Omega 18" which is 4 ohm, but I haven't heard of any reports/reviews of one in a 301, so who knows. Might be worth a call or email to Eminence to get their opinion.

 

[StereoPlayer]

I don't have a lot to add. When I got my current 301 cabinet it was loaded with an Eminence Professional Sigma Pro 18A-2. I eventually found a blown original Cerwin-Vega AC188L which I bought and sent off to the now-defunct Orange County Speaker for reconing. Might be my imagination, but it seemed to me that the restored CV sounded better than the Sigma, fuller, but that's not to say the Sigma didn't sound OK because it did. The Sigmas are still available, but they're 8 ohm too, so it would be a lateral move from the Fender in that regard. If the OP wants to pour the bucks into something new then Eminence has the Omega 18" which is 4 ohm, but I haven't heard of any reports/reviews of one in a 301, so who knows. Might be worth a call or email to Eminence to get their opinion.

Thank you. And I like the info for my brain too!

 

[Doombuggy68]

I don't have a lot to add. When I got my current 301 cabinet it was loaded with an Eminence Professional Sigma Pro 18A-2. I eventually found a blown original Cerwin-Vega AC188L which I bought and sent off to the now-defunct Orange County Speaker for reconing. Might be my imagination, but it seemed to me that the restored CV sounded better than the Sigma, fuller, but that's not to say the Sigma didn't sound OK because it did. The Sigmas are still available, but they're 8 ohm too, so it would be a lateral move from the Fender in that regard. If the OP wants to pour the bucks into something new then Eminence has the Omega 18" which is 4 ohm, but I haven't heard of any reports/reviews of one in a 301, so who knows. Might be worth a call or email to Eminence to get their opinion.

The Fender speaker is well made and doesnt sound bad. there was some rattle in the cab before I removed the speaker but I think it was the back, some of the screw holes are a little stripped and wont tighten. Id like to find a 4 ohm speaker so I have a better match for the Acoustic heads, otherwise Id just put the Fender back in. Im not sure what the Fender speaker came out of. Weird that its made in Japan, I wasnt aware Fender had speakers, cabs or amp made in Japan. Makes me think its farmed out to Yamaha or some other company.

 

[user362432]

The Fender speaker is well made and doesnt sound bad. there was some rattle in the cab before I removed the speaker but I think it was the back, some of the screw holes are a little stripped and wont tighten. Id like to find a 4 ohm speaker so I have a better match for the Acoustic heads, otherwise Id just put the Fender back in. Im not sure what the Fender speaker came out of. Weird that its made in Japan, I wasnt aware Fender had speakers, cabs or amp made in Japan. Makes me think its farmed out to Yamaha or some other company.

I had one situation when the whole cab was rattling. I found that front board was partially unglued from the top of the cab. It was, probably, the reason for the previous owner to dump it. I got it for $100 from GC. Easy fix.

 

[iriegnome]

Anyone up for a even trade for a 125 for my 136?

 

[Bulltrout]

Hi everyone. I recently bought a pristine looking Acoustic 126 combo. Probably the best looking vintage acoustic piece I've come across. Unfortunately the amp has really low output, and the boost and bright switches aren't working - the good news is that the EQ does. Anyone else have experience with this or this model - I took some gut shots, but nothing immediately jumped out to me. Regrettably, none of my local techs seem inclined to take on a vintage solid state amp.