APP992 thread

[ppa]

Hi pier , just wondering, on pcb it seems that D6>D7 is open curcuit, do i have to connect them by soldering ?
greets
axel

yes, it is a mistake (there are not other mistakes on this PCB). This is a thing that I say always when I sell the kits, scuse me if I have forgotten to say you it.
BTW I will correct it on new stock of PCB's.

 

[sharpeleven]

Just started my build now and realized that my kits include a variety of transistors not listed on the v.2 BOM. Then again some are missing that should be there according to the BOM.

for transistors in question, BOM says:

• 4 x BC556B
• 2 x BC546B
  

included in my (four) kits:

8 x BC556B (should have 16)
4 x BC546B (should have 8 )
4 x BC547B (not listed on BOM)
10 x C557C (not listed on BOM)

I have received a number of Photos plus a BOM but no build guide. Is there still a build guide to v2? Any help much appreciated, thanks!

 

[ppa]

I have sent you the old BOM for error, in the new version I have optimized the circuit with the new BOM. The differences are only on the transistors that are on the following list 

Q1=Q2= BC557B

Q3=Q4= BC556B

Q8=BC547B

Q10=BC546B

BTW send me your email and I will send you the complete docs

Pier Paolo

 

[tsv]

Hi

I just received one of your APP992 Opamps. I will be using it to replace a Forssell JFET992 in this circuit:

http://www.forsselltech.com/media/attachments/Dual_Amp_PCB_Schematic.pdf

Will the C1 33pF cap be appropriate for the amp? Will the servo circuit be Ok?

Thanks

 

[ppa]

Hi

I just received one of your APP992 Opamps. I will be using it to replace a Forssell JFET992 in this circuit:

http://www.forsselltech.com/media/attachments/Dual_Amp_PCB_Schematic.pdf

Will the C1 33pF cap be appropriate for the amp? Will the servo circuit be Ok?

Thanks

Hi

they are both ok for it, 33pF and servo.

APP992 is very stable so you can use 5pf , 10pF, 15pf too, but also higher value.
But since APP992 has 40 Mhz of BW on unity gain (a very high value), I council you to use 33pF or 47pF to avoid that the amp will have too BW.
The FT993 has also a very high BW so, I think, for this reason Fred Forsell has used a value not so low.

The servo used is OK.

If you want, you can reduce R6 to zero too.

thanks for questions.

 

[tsv]

Hi Pier

Thanks for your response. I put the opamp in this morning and it works perfectly and sounds great as is!

I'll experiment with R6 as zero next.

Thanks

 

[bacbacou]

hello Pier,

I always wait  the parts you forget to send me to build my APP992... Anyway, I bought them myself and build one : It did not work... I build the second one, always with the help of Assembly manual, double check everything, and it did not work Too !

Quite strange, it is the first time that a kit do not work for me, and I build a lot of kits...
I tried them in place of a GAR2520 in a CAPI VP26 preamp. I have absolutely no output signal : did you ever see someone with the same problem ?  what's could be wrong ?

regards,

Richard

 

[ppa]

hello Pier,

I always wait  the parts you forget to send me to build my APP992... Anyway, I bought them myself and build one : It did not work... I build the second one, always with the help of Assembly manual, double check everything, and it did not work Too !

Quite strange, it is the first time that a kit do not work for me, and I build a lot of kits...
I tried them in place of a GAR2520 in a CAPI VP26 preamp. I have absolutely no output signal : did you ever see someone with the same problem ?  what's could be wrong ?

regards,

Richard

Richard, I have sold a lot of 992 kits and they work fine, probably you have done the same mistake on them or another one,  but don't worry,  at this point I will send you two assembled and tested 992's 

I have sent you some days ago another parcel  with priority mail with the missing components but I see it is not yet arrived to you, sorry for that.

regards
Pier Paolo

 

[bacbacou]

thank you Pier,

I received the parts, and I think I find the problem on my APP992 pair : I do not have any BC550C or BC547B in that parts that I received !
The two last transistors that I have to put in place in Q8 was  BC546B, like It was written in the BOM, or I find tree different informations on your docs :
Q8 = BC550C in the assembly manual
Q8=BC547B here
Q8=BC546B in the BOM...

so what the right part for this place...could you confirm ?

regards,

Richard

 

[ppa]

all these ones can be used for Q8

BC550C, BC550B, BC547B, BC547C,  BC546B, BC546C

so BC546B can be used for, I have put it on the parcel for this reason.

 

[Winetree]

My kits had the short pins.
There are pictures of the P.S.B. mounted upside down with long pins.
Are these correct?

 

[ppa]

yes, it's right

 

[bacbacou]

hello Pier,

thank you to send me already mouted models.
The APP992  works really well in my CAPI VP26 preamp !!!

regards,

Richard

 

[kante1603]

Hello Pier-Paolo,


hope you´re fine.
I´m about to build another pair of onlymee´s Sontec EQs.
The main audio amps have provisions of using DOAs instead of ICs (OPA134 in this case).
Your APP992 works very nice on the output.
My question is:Will the APP992 work on the input (as receiver) too?
Here is the schematic for your reference (upper left corner):
http://www.thedonclassics.com/schematics/250EQ_schematic.pdf


Thank you in advance,


best regards,


Udo.

 

[ppa]

Hello Pier-Paolo,


hope you´re fine.
I´m about to build another pair of onlymee´s Sontec EQs.
The main audio amps have provisions of using DOAs instead of ICs (OPA134 in this case).
Your APP992 works very nice on the output.
My question is:Will the APP992 work on the input (as receiver) too?
Here is the schematic for your reference (upper left corner):
http://www.thedonclassics.com/schematics/250EQ_schematic.pdf


Thank you in advance,


best regards,


Udo.

Hi, I am going to send you a PM
thanks
best regs
Pier Paolo

 

[kante1603]

Hi, I am going to send you a PM
thanks
best regs
Pier Paolo

Hello Pier Paolo,


did you send a PM to me?
I had some issues here with PMs recently,so just asking.
Have a nice weekend,


Udo.

 

[ppa]

Hi, I am going to send you a PM
thanks
best regs
Pier Paolo

Hello Pier Paolo,


did you send a PM to me?
I had some issues here with PMs recently,so just asking.
Have a nice weekend,


Udo.

PM sent

 

[anthorama]

Quote from: kante1603 on May 29, 2016, 10:18:15 AM
Hello Pier-Paolo,


hope you´re fine.
I´m about to build another pair of onlymee´s Sontec EQs.
The main audio amps have provisions of using DOAs instead of ICs (OPA134 in this case).
Your APP992 works very nice on the output.
My question is:Will the APP992 work on the input (as receiver) too?
Here is the schematic for your reference (upper left corner):
http://www.thedonclassics.com/schematics/250EQ_schematic.pdf


Thank you in advance,


best regards,


Udo.

Hello Pier Paolo,

I am building a pair of the same Sontec eqs, and would like to use your op amps as well, on input and output.  What do I need to change in order to use them best?

Thanks,
Anthony

 

[Potato Cakes]

Pier,

Hello,

I'm using a number of your 992's in a multichannel preamp that runs on 24V rails. On initial testing I had incorrectly wired the power switch, which I caused a number of the DOA's to fail. After I fixed that I put in a new batch of 992s and it works perfectly. So now I want to fix the 992s I blew up and I found that both the BD139 and 140s had failed. So I swapped them out and the "repaired" one works for a while, but it gets really hot then those same two transistors fail. The rest of the op amps are fine. I verified that the problem is with the op amps I'm trying to repair and not the particular channel itself. I swapped all the ICs on the 992, checked all the resistors and diodes and caps, and it still gets really hot to the point of smoking coming off the op amp then failure again. The last time I did have a BD140/139-16 and not a the NPX45 version that comes with the kit, so I don't know if that was the case. I'd like to repair the ones I have, but I'm a bit baffled at what the problem could be if I changed out the parts that are bad and it is still failing. I'm not sure what would cause it to get crazy hot to the point of the power transistors die.


Thanks!

Paul

 

[ppa]

Hi Paul,
before all you should chek the voltage between the BD's bases

PS: could you send me some photos of that APP992 you blew up? thanks