Pearl Two

dcbingaman · 2013-02-19 4:58 am

Distortion Meter

Me too !! One of those nice Audio Precision rigs would be a nice birthday present, but my wife thinks its a dumb idea !!

dcbingaman · 2013-02-19 5:01 am

She feels the same way about the new 'Vette (make mine a Z51 in silver....)

6L6 · 2013-02-19 5:37 am

You can get used first gen AP rigs for about a grand. (Although you need an old windows machine to run it...)

This looks fantastically interesting -- QA400 Audio Analyzer And it's only $200!!!!

Vette? A '70 or '71would be great, but honestly any chrome-bumpered Mako would be fine.

poli · 2013-02-19 2:22 pm

Hi guys,
thanks a lot for all your answers! I will check out the MOS-FET and the other ZTX450 transistors. Yes, I have a jumper in place for R15.

One more question:
Did you have problems in adjusting voltage between R16 and R17 with P1 to 0V DC? I find it very difficult, I am having drift to +- 0.3 V - is that normal?

Thanks
Poli

richluvsound · 2013-02-19 3:05 pm

Hi Poli ,

that drift is within spec ....

I checked my VDC and all good ,but I do have a short fall where I need 10mA
I'm getting .03 mA

Rich

bnorrish · 2013-02-19 3:34 pm

poli said:
Hi guys,

One more question:
Did you have problems in adjusting voltage between R16 and R17 with P1 to 0V DC? I find it very difficult, I am having drift to +- 0.3 V - is that normal?

Thanks
Poli

300 mv seems high. I would think you could get under +/- 15 mv.

Wellerman · 2013-02-19 5:20 pm

richluvsound said:
Hi Wellerman ,

was this post to me or Poli ?

To poli, but maybe it is of some use to you too

Wellerman · 2013-02-19 5:24 pm

bnorrish said:
What clued you that ZVP3310 was bad? Did you measure ~ 10 mA current going into per Wayne's voltages diagram?

I used 10R instead of 10K on R7, R8 and R10. I think I get carried away stuffing all the 10Rs. After replacing them, found out that Q1 and Q3 were bad. Waiting for an order of ZTX450s. I only ordered 10.

Well,actually a post by someone having a bad ZVP. Voltages around mine were ok, but I thought I'd try to replace it anyway and fortunately that worked.

Wellerman · 2013-02-19 6:18 pm

poli said:
Hi guys,
thanks a lot for all your answers! I will check out the MOS-FET and the other ZTX450 transistors. Yes, I have a jumper in place for R15.

One more question:
Did you have problems in adjusting voltage between R16 and R17 with P1 to 0V DC? I find it very difficult, I am having drift to +- 0.3 V - is that normal?

Thanks
Poli

My voltages drift too. I replaced my dmm as it drifted in the mV range with the leads not connected. But even with the new one (Metrel 9040) the voltage drifts. I also noticed that it takes some time before the readings stabilise a bit. When connected I might get a few 100 mV or even over 1V, which then continually decreases to more normal voltages. I can get it to drift between ±30mV with occasional peaks around ±60mV. Also P1 is quite sensitive around the 0V point. Just a tiny bit of adjusting might get the voltage from say 80mV to -50mV.

What I do now is to let the Pearl II warm up for at least an hour, then conect the dmm and watch the voltage for quite some time, ocasionally adjusting P1 until I've got the feeling that I get satisfactory readings.

Salas · 2013-02-19 6:33 pm

Looks like a Brymen OEM meter possibly, which is a good thing.

rsavas · 2013-02-19 6:35 pm

Not sure why you think that the output DC voltage dirfting around a bit, is a problem. The O/P is AC coupled so it would not affect a following stage. I do not believe that the ckt is designed to be rock solid, thus not be able to drift around a bit = a non-issue.

dcbingaman · 2013-02-20 2:46 am

New 'Vette

6L6: A primo condition L88 in that vintage would be very nice - but the NEW one (2014) looks like a real honey too, (and probably less expensive). I'm still trying to figure out how to get one in the garage before she notices it. I need stealth paint.

6L6 · 2013-02-20 3:07 am

The new 'Vette looks like what you would get if Chris Bangle was hired to design a Dustbuster.

bnorrish · 2013-02-20 3:29 am

Good thing I have plenty of ZVP3310 on hand in case. Seems to be fairly common issue.

Not sure about the new Corvette. The one in blue looks OK - red looks very tacky. Do not see many Vettes here on the East Coast. 'The head of Chevy marketing, Chris Perry, acknowledges that too many people see it as the car of "the successful plumber."'

6L6 · 2013-02-20 3:32 am

Yep. That's a very accurate diagnosis, and unfortunately it's terminal. Chevy will never be able to make it cool again.

richluvsound · 2013-02-20 10:38 am

'6' .... did you use kapton tape to insulate the signal wires ?

Old vettes ... stunning ! The new ones are just 1/4 mile bullies .

Aston Martin for Boston me thinks

6L6 · 2013-02-20 1:03 pm

The signal wire is surplus, it's a twisted teflon covered pair (about 22awg) in an outer teflon jacket. The outer jacket is, as you notice, about the color of kapton.

I believe it's plenum or in-the-wall rated. Nice audio wire, is you don't mind the color.

poli · 2013-02-20 5:22 pm

Thanks everybody for the hints about the voltage drift.
I think, I just leave it that way and see that I find out about the faint signal that I am getting on both channels. I have not measured the current through the MOS-FET, but will do that now.
Cheers
Poli

bnorrish · 2013-02-20 5:44 pm

Boston is more of a BMW town.

6L6 · 2013-02-20 6:55 pm

I've got a Benz wagon, wife has a BMW

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