Pioneer Spec 4 clipping?

[PAUL Camden]

Understandable.

I did it with recommendation from CV so was confident, and I blew a number of those 3.0's with no issues. Of course these were a different model as well, the D9's.

Ended up using 5.0 amp fast blows in the end as they were more readily available. Blew a lot of those as well, speakers in great shape till lost in the Big D.

Too fun to crank, those CV's.

Did you try to engage the low freq filter on your preamp?

They are fun to crank, thats why I bought them. I have 4 B&W dm220 speakers that I use for 90 % of my listening
and have the cerwins on a different amp (biamped) when I need things to shake.

I love the Vegas, the guy I bought them from tells me im too hard on them but I bought the to abuse.

I did not try the low freq filter, your the second guy that asked me that today. I am pretty much a rookie here but
I will definitely try tonight when I get home

 

[PAUL Camden]

well i called the shop that did the work and he admitted he didnt check everything out. he doesn't even own a distortion meter.
live and learn, he got the amp up and running but didnt get it right., that was a 200 dollar lesson. got a good recommendation from a couple of folks for another shop locally for vintage gear service so thats where Im going next. I really do like the amp, really great sound but damn, Ill probably have 8 or 9 into before Im through.

 

[savatage1973]

well i called the shop that did the work and he admitted he didnt check everything out. he doesn't even own a distortion meter.
live and learn, he got the amp up and running but didnt get it right., that was a 200 dollar lesson.

Not surprising--I was going to say something the first time you mentioned $200. Basically, you got off easy, even just getting it "fixed"--up and running at all for $200. I don't know about your geographic area, but $200 doesn't buy you a whole lot of bench time with a good tech. Parts are generally pretty cheap, but time is $$$. Even a simple "tune-up" that doesn't necessarily require any parts, can easily run more than $200 in most areas.

 

[PAUL Camden]

Not surprising--I was going to say something the first time you mentioned $200. Basically, you got off easy, even just getting it "fixed"--up and running at all for $200. I don't know about your geographic area, but $200 doesn't buy you a whole lot of bench time with a good tech. Parts are generally pretty cheap, but time is $$$. Even a simple "tune-up" that doesn't necessarily require any parts, can easily run more than $200 in most areas.

True, Im not really pissed off at the guy. he did fix some stuff. a couple of small caps and some solder joints.
but he did tell me everything was good. just wont take anything high end over there.

 

[rcs16]

thx for the update, one way or the other you have to figure out if the limiters are being activated, thus causing your issue
have someone properly adjust the limiter

 

[PAUL Camden]

thx for the update, one way or the other you have to figure out if the limiters are being activated, thus causing your issue
I can suggest to turn them down to see how they perform.
You could note & mark the trim pot wiper position, on the VR3 & 4 pots where they are currently set at,
then turn the pots counter clock wise a bit, then test to see if the amp triggers the limiter under the same conditions.
be careful, these limiters have been known to kill speakers, usually one tests/adjusts with a resistor load, not good speakers

Thanks, I tried that and it did not rigger limiter when I turned them counter clock wise. there seems to be a peak,I just think its low.
I did back off on the bass a bit so the woofers are not bouncing out bad like before. I also tried just 1 set of 8 ohm speakers ( b & w dm220 )
and I can run it up to 150 watts, did this for about 2 seconds and the backed off. all 4 b & w's and it cuts out around 75 watts.
is it possible thats all this amp has? I run all 4 on my sherwood amp which is rated 120 watts at 100 watts and the lights blink a bit but no distortion.
I can run the 4 ohm cerwins vegas on the sherwood and it handles them better also.

 

[LesE]

Keep in mind that the level meters are calibrated to be accurate only for a resistive 8 ohm load. They are set up so that the meter shows 0dB when the output voltage is 34.64V @ 1KHz. This corresponds to 150W of power into an 8 ohm load. 180W into a 4 ohm load will be produced with an output voltage of 26.83V. So, the output meters will indicate considerably lower output power for 4 ohms @ 180W than it will for 8 ohms @ 150W.

The best way to evaluate the amplifier's maximum output power into 4 ohms is with a test signal, a dummy load and a scope.

 

[PAUL Camden]

Keep in mind that the level meters are calibrated to be accurate only for a resistive 8 ohm load. They are set up so that the meter shows 0dB when the output voltage is 34.64V @ 1KHz. This corresponds to 150W of power into an 8 ohm load. 180W into a 4 ohm load will be produced with an output voltage of 26.83V. So, the output meters will indicate considerably lower output power for 4 ohms @ 180W than it will for 8 ohms @ 150W.

The best way to evaluate the amplifier's maximum output power into 4 ohms is with a test signal, a dummy load and a scope.

I figured that was the case on the meters (says right below meter 8 ohm) and I know the amp is rated for 180 at 4 ohm load. so im comparing it to performance of the Sherwood and was
shocked that it wont at least perform at the same level as the sherwood. I do remember the tech that worked on this did replace a cap on the protect circuit. he told me it was bad and he
replaced it with whatever was on the schematic in the service manual, but he said it took a long time for the amp to come out of protect when starting up, like 20 or 30 seconds.
he said the old cap was different than the schematic so he put one in that matched the old one and the amp came up at about 10 seconds.
Im wondering if the difference in the caps would affect the overload calibration???

 

[rcs16]

sounds like it was the relay delay ecap, so it should not affect the limiter.
have some properly adjust the limiter per the manual

 

[PAUL Camden]

sounds like it was the relay delay ecap, so it should not affect the limiter.
If it was my spec 4, I'd replace the o/p devices that are rated for 150W and use new 250W MJ211193(4),MJ21195(6), parts which can handle much more power, turn the limiter down to its minimum, or remove its op, good luck blowing those devices.
what sherwood model are you using? a spec 4 should outperform a receiver amp rated at 120W

Blowing what devices? sherwood model hp 2000

 

[kevzep]

Blowing what devices? sherwood model hp 2000

He means if you replaced the output transistors with the modern MJ21193/4 they are a much higher powered device, so it would be very unlikely you'd blow them in this amplifier.

You do realise the meter is set to watts @ 8Ω right, so when you are driving lower impedance loads, it producing a lot more power than what the meter says.
This, plus the fact that depending on the meter ballistics, many many peaks will not be registered by the meter as they are too fast, this is why a lot of meters are often accompanied by a Peak LED.

 

[PAUL Camden]

He means if you replaced the output transistors with the modern MJ21193/4 they are a much higher powered device, so it would be very unlikely you'd blow them in this amplifier.

You do realise the meter is set to watts @ 8Ω right, so when you are driving lower impedance loads, it producing a lot more power than what the meter says.
This, plus the fact that depending on the meter ballistics, many many peaks will not be registered by the meter as they are two fast, this is why a lot of meters are often accompanied by a Peak LED.

yes, I am aware the meters are set to 8 ohm. as far as his suggestion on those MJ21193/4 is concerned, I will discuss it with the tech at the "New Place"
I plan on taking it too.

 

[PAUL Camden]

lots of good info here. you guys are great.

 

[rcs16]

edit shot gun

 

[PAUL Camden]

what output devices are in it?, the service manual says that they used 2 different types. the 150W devices 2sb554/2sd424 or the 200W Toshiba devices 2sb600/2sd555
I worked with a guy a while back who re-built his spec-4, i'd have to look at what his id was.
fyi there are lots of threads on this unit, check them out so you can understand what people have done.

I will have to open it and take a peek

 

[Gazdatronik]

I figured that was the case on the meters (says right below meter 8 ohm) and I know the amp is rated for 180 at 4 ohm load. so im comparing it to performance of the Sherwood and was
shocked that it wont at least perform at the same level as the sherwood. I do remember the tech that worked on this did replace a cap on the protect circuit. he told me it was bad and he
replaced it with whatever was on the schematic in the service manual, but he said it took a long time for the amp to come out of protect when starting up, like 20 or 30 seconds.
he said the old cap was different than the schematic so he put one in that matched the old one and the amp came up at about 10 seconds.
Im wondering if the difference in the caps would affect the overload calibration???

Les has good advice, but also, 4 ohm nominal means that the impedance can possibly dip well below that. So either the Spec is sick, or possibly the Sherwood is using an infrasonic filter of some sort that allows it to push the Vegas with crapping out.

I have had high end gear that freaks out at high volume due to this lack of filter, to the point where lesser stuff works better.

 

[PAUL Camden]

Les has good advice, but also, 4 ohm nominal means that the impedance can possibly dip well below that. So either the Spec is sick, or possibly the Sherwood is using an infrasonic filter of some sort that allows it to push the Vegas with crapping out.

I have had high end gear that freaks out at high volume due to this lack of filter, to the point where lesser stuff works better.

Thats pretty interesting. the Sherwood was considered high end gear back then. I just assumed the spec gear was a cut above it

 

[PAUL Camden]

Thats pretty interesting. the Sherwood was considered high end gear back then. I just assumed the spec gear was a cut above it

By the way, the clipping lights come on on that Sherwood at 150 watts (8 ohm load) the lights were considered accurate.
I dont know what kind of watts that would translate to for 4 ohm load for the vegas.

 

[rcs16]

edit shot gun

 

[Dingman]

Did I see you adjusting the trimmers with the system running, and playing? Not a good idea, just follow the procedure in the manual (sorry if you said you did this, if I missed it).

Ya, the amp appears to be motorboating, low freq response notwithstanding. That is so hard on your speakers.
That amp needs to be gone thru due to its age and how hard you are pushing it.
If not for the fuse, you'd have damaged VC's in the speakers.