Pioneer Spec 4 clipping?

[PAUL Camden]

Purchased a non working Spec 4 recently, just got it back from the shop and trying out for the first time.
I am using a pair of Cerwin Vega at15's . So when I try to pour some power into them I get woofer bounce
and the thing cuts out like protect mode when Im at about 70-80 watts average on the meters.

The amp is rated at 150 for 8 ohm and 180 at 4 ohm. Am I wrong to think I should be able to push a little more before this happens? same speakers on my mcintosh mc2500 and can go 350 easy.

Am I just running out of amp with the spec 4? I am just surprised this happens at lower wattage.

 

[rcs16]

ask the person at the shop you had it serviced at, if they think that what you describe as normal?Ask the shop if they tested the Spec 4 into a resistive load ( 4 & 8 ohms) at full volume?
The spec4 has a over current protection(power limiter) adjustment, maybe that is not set correctly per the service manual. see p14
Also DC offset and bias should be checked again.

 

[Gibsonian]

What do you mean by woofer bounce?

You cannot go much by meters, that is for sure. I was able to get a higher power amp than your Spec 4 to clip into D-9's, it wasn't that hard. That being said I have no idea if your amp is healthy or not.

Suggestion to request if they tested output into 8, 4 ohms is a good one. I'll bet they didn't.

Overcurrent limiter is a suspect, as was mentioned. I think I would disable that if it were me.

That amp is long in the tooth and if they did just the minimum to get it running, a full restore is likely something it might need. Good luck!

 

[PAUL Camden]

ask the person at the shop you had it serviced at, if they think that what you describe as normal?Ask the shop if they tested the Spec 4 into a resistive load ( 4 & 8 ohms) at full volume?
The spec4 has a over current protection(power limiter) adjustment, maybe that is not set correctly per the service manual. see p14
Also DC offset and bias should be checked again.

I will call him, just wanted to do a little research before I call. Ive never had a working spec 4 so I dont know what to expect.
like I said, I can dump 100 watts into those vegas no problem on the sherwood hp 2000 which is rated at 120 watts per channel,
the leds blink a little but no distortion and no problem.

 

[PAUL Camden]

What do you mean by woofer bounce?

You cannot go much by meters, that is for sure. I was able to get a higher power amp than your Spec 4 to clip into D-9's, it wasn't that hard. That being said I have no idea if your amp is healthy or not.

Suggestion to request if they tested output into 8, 4 ohms is a good one. I'll bet they didn't.

Overcurrent limiter is a suspect, as was mentioned. I think I would disable that if it were me.

That amp is long in the tooth and if they did just the minimum to get it running, a full restore is likely something it might need. Good luck!

hard to believe this amp cant push those vegas better. My sherwood hp 2000 handles them just fine. The tech told me the amp was healthy.
the 4 big caps were replaced by the previous owner but not the smaller ones.

Ive had the cerwin vegas out to 400 watts on my mcintosh!

 

[PAUL Camden]

What do you mean by woofer bounce?

You cannot go much by meters, that is for sure. I was able to get a higher power amp than your Spec 4 to clip into D-9's, it wasn't that hard. That being said I have no idea if your amp is healthy or not.

Suggestion to request if they tested output into 8, 4 ohms is a good one. I'll bet they didn't.

Overcurrent limiter is a suspect, as was mentioned. I think I would disable that if it were me.

That amp is long in the tooth and if they did just the minimum to get it running, a full restore is likely something it might need. Good luck!

by woofer bounce its like the woofer wants to jump out of the box, not normal rebound.

 

[Gibsonian]

So the woofer moves more than normal but is not as loud as your 120 watt receiver when doing so?

Or it is moving this extreme amount when no music is playing?

Not sure what is going on with your amp/speaks here.

FYI, if the Spec 1 is capable of lower freq response reproduction than your receiver, this will cause the woofer to move more.

 

[embrown057]

Sound like the power limiter was not set correctly, some tech's are concerned at running the amp to such high levels. He may not have had large 4 ohm load to run it into. Still, an amp should never leave a shop with being brutally tested to it full potential.

 

[PAUL Camden]

Sound like the power limiter was not set correctly, some tech's are concerned at running the amp to such high levels. He may not have had large 4 ohm load to run it into. Still, an amp should never leave a shop with being brutally tested to it full potential.

I agree, I took it to this shop because the record store that I bought another amp from had sent me there to get the amp I bought from them fixed, it was under warranty.
the only place I have any experience with was 30 years ago. he's still in business but has an 8 week backlog.

Now I have to decide if I want to deal with this guy or take it somewhere else. This last visit was 200 bucks.

 

[zebulon1]

The adjustment is set with two trimmers for the top and bottom sign wave (Positive half cycle and negative half cycle). The amp is connected to a 4 ohm load. Amp brought up to 200 watts and adjusted.
If you don't mind a bet? I bet he accidentally adjusted one of the limiters while setting the Offset and Balance.
It should be included in the first service.

 

[PAUL Camden]

So the woofer moves more than normal but is not as loud as your 120 watt receiver when doing so?

Or it is moving this extreme amount when no music is playing?

Not sure what is going on with your amp/speaks here.

FYI, if the Spec 1 is capable of lower freq response reproduction than your receiver, this will cause the woofer to move more.

Ok, so the spec 4 is rated 5Hz to 100kHz, the sherwood is 20Hz to 20kHz. so the spec 4 is capable of a bit lower response

it moves an extreme amount with music playing. guess I didn't notice if in general they move more on the spec 4 but that may be happening

It doesn't seem I can get the same volume from the spec 4 before it happens. I was pretty surprised. I actually blew a speaker fuse
when I first put some power to them. tried to push to 100 watts on the meter and saw the woofer on that speaker really hyper extend
and you could hear the distortion and then fuse blew. happened pretty fast. after that I walked it up slow and it would go into protect
around 80 watts. Not peak watts, more like average sustained around 60-80 average. it sounds fine if I don't push it past that around 75ish point.
was expecting the spec 4 to have a little more to give. the cerwin vega at15's are pretty efficient.

 

[PAUL Camden]

The adjustment is set with two trimmers for the top and bottom sign wave (Positive half cycle and negative half cycle). The amp is connected to a 4 ohm load. Amp brought up to 200 watts and adjusted.
If you don't mind a bet? I bet he accidentally adjusted one of the limiters while setting the Offset and Balance.
It should be included in the first service.

it also seems like the left side is a little weaker, I watched the meters for quite a while at around 50 watts and the left was lagging consistantly

 

[PAUL Camden]

I wonder about the meters, the increments are for 8 ohm. so I'm running 4 ohm load . so does that mean its actually
a higher load than the meters show with 4 ohm speakers?

 

[Gibsonian]

What preamp are you driving the Spec 4 with?

If it has a low or subsonic filter, you might engaging try this. Would lower the woofer movement and the wattage used with most music material, esp music with low freq content.

 

[Gibsonian]

And what fuse do you have in your CV's? Per CV, at least on the D9's, they recommended going up to 3.0 amp slow blow, the OEM fuse was 2.5.

 

[embrown057]

My back log is 6 weeks, any shop is going to have a waiting list. The problem is most all of these repair shops are just going to do what that have to get it up and running. Making it perform as it should takes much more than that. The unit just comes back over and over till the user gets sick of being nickeled and dimed and send it to someone that specialized in vintage repair. As far as the meters I would bet they never calibrated the meter amp circuit either.

 

[PAUL Camden]

My back log is 6 weeks, any shop is going to have a waiting list. The problem is most all of these repair shops are just going to do what that have to get it up and running. Making it perform as it should takes much more than that. The unit just comes back over and over till the user gets sick of being nickeled and dimed and send it to someone that specialized in vintage repair. As far as the meters I would bet they never calibrated the meter amp circuit either.

He said he did calibrate meter amp circuit but how could that be true? the left side is off by at least 20%. Ill give the guy a call tomorrow and see what he says. its a crap shoot if you dont have a good referral. also got a referral from someone today so ill have to decide if I want to deal with the other guy anymore.

 

[PAUL Camden]

I do like the spec 4 amp though. put 4 B & W dm 220's on it and man what a nice sounding set up!

 

[PAUL Camden]

And what fuse do you have in your CV's? Per CV, at least on the D9's, they recommended going up to 3.0 amp slow blow, the OEM fuse was 2.5.

Mine have 2.5 slow blow. Im tempted to try the 3.0, I will have to research that. I do push them hard quite a bit, maybe better to be on the conservative side.

 

[Gibsonian]

Mine have 2.5 slow blow. Im tempted to try the 3.0, I will have to research that. I do push them hard quite a bit, maybe better to be on the conservative side.

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?