PRR-176 REV 4 Build Thread ***Manual up!***1/16/14 - (chk 1st post)

[Sylvain D.]

Merci AntoineQ!

I'll be mounting mine in a 1U case, but the VU scales will certainly be handy.

 

[johnnyscotch]

I'm interested in sourcing a power trafo as well.

Will Gustav's work?
https://pcbgrinder.com/index.php?route=product/product&path=94_97&product_id=103

 

[berkleystudios]

maybe its just me but the build butler seems to be down

 

[ding]

maybe its just me but the build butler seems to be down

confirmed

 

[Sylvain D.]

maybe its just me but the build butler seems to be down

Adam,

I also got an odd behavior a week or so ago and it turned out to be my browser was too old. it worked on a newer machine. (both Win and Macs)

But Abe told me his brother has been working on it so maybe that's what's up...

 

[johnnyscotch]

Hey Guys,

I'm going to place a Mouser order soon. Here is the cart I put together (building off the one posted earlier in this thread):
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=d4c538fac1

Feel free to look over it and let me know if there's anything fishy. Hopefully it's all good and this will help some folks out.

And here is a link to a power trafo (per Abe):
http://www.antekinc.com/as-0515-50va-15v-transformer/

Anyone see a BOM for Abe's DOAs?? Sorry if I missed it.

Cheers!
Eric

 

[Sylvain D.]

This one from kakumei47 a few pages back.

http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=b36f41ddbf

 

[tazwolf]

Hi
I am thinking of building mine using an attenuator for the front end, has anybody else done it this way and can tell me if its a good alternative?

/taz

 

[manulaf]

Hi everybody

I finished my prr176. I'have build it with antoine Q With same frontpanel and trafo.
It works fine but when I push it in extreme settings (fast attack and release, input CW) it start to self oscillate (weird HF hiss noise) and I have to turn it off to stop oscillation !
I used 6 Abe's DOA, don audio transformer, RCA tube , Cinemag interstage and Carnhill output trafo.
Thanks for your help
Manu

 

[johnnyscotch]

How critical is it to match the 550 transistors on the DOAs??

 

[manulaf]

Hi
I'havn't solved my squeal problem but I working on it.
Another thing is that right channel have less compression than left channel.
Here is a picture of my unit.

 

[prh]

Hi
I'havn't solved my squeal problem but I working on it.
Another thing is that right channel have less compression than left channel.
Here is a picture of my unit.

Out of curiosity, do you have insulation under the tubes?

 

[manulaf]

Out of curiosity, do you have insulation under the tubes?

No I haven't ! What kind of insulation ?
Thanks.

 

[manulaf]

And the front panel 

 

[prh]

Out of curiosity, do you have insulation under the tubes?

No I haven't ! What kind of insulation ?
Thanks.

Well, the tubes were intended to lie horizontal, but an error in the PCB routing means that the tubes either have to be installed vertically (as you have) or horizontally using special adapters from the board designer.

There are resistors installed on the tube footprint, and it occurred to me that there might be the possibility of shorts if the valve socket board was able to touch the resistors underneath.

I'm still sitting on my boards until a few more builders have reported successful builds  8)

 

[manulaf]

Put some insulation between tube socket and pcb socket but that didn't change anything. Squeal still here at High level !

Also it's very hard to calibrate thump trim. With fast attack an fast release I can here a put put put....(in mid input position) when sound pass through my unit especialy on channel 2. I can fixed it in either trim position.
Thanks

 

[manulaf]

Hi
Tested my unit this afternoon, try to explain my issues (sorry for my english)

- Compression work fine and sound great on normal setting and link mode (modern link)
- But in dual mode right channel is less compressing than the left channel maybe 3 or 5 db less. Try to swap tubes without Changes.

- My unit still squealing in fast attack an CW input (I have to turn the unit off to stop HF squeal)
- There is something I don't understand with thump trim I can really calibrate it on both channels. I have to turn thump trim CCW to have the best sound but still have thump in fast attack. Especially one of the two tube and this one is "motorboating" in fast attack too. This tube can be bad ? Or just a bad trim adjust ?
- I saw that there was a plate balance trim in the latest revision of prr176. Why removed it ? Can it help me to fix my issue ?
- did I miss something ?

Thanks very much for your help. I'm a beginner and I'm pretty lost  :'(

 

[johnnyscotch]

I can't find schematic for Abe's DOAs, can anyone tell me which 550s are supposed to be the matched pair??

thanks

 

[manulaf]

Hi

I believe that the bc550 matched are in position 1 & 3 (input) transistor.

 

[johnnyscotch]

Cool, thanks!

Hi

I believe that the bc550 matched are in position 1 & 3 (input) transistor.