PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*

[ethervalve]

aside: hey Abe, are you planning on making another run of these boards? I'm hoping to build a second one in a 2RU chassis with switchable thresholds and few other bells and whistles.
Also: you wouldn't happen to know if a slight step-up, 1 + 1 : 2.28 transformer would be suitable for the inter-stage? The Lundahl LL1521B seems to come up for sale for decent prices used quite frequently. According to a doc on the Lundahl site: "The LL1521B is a high impedance line input transformer, very similar to the LL1540 but with a slight stepup."
Thanks!

 

[Dr_J]

Hi baadc0de,

don't know if it may help, but I had this problems
http://www.groupdiy.com/index.php?topic=44586.740

Good luck!

ROCK-ON.

 

[abechap024]

aside: hey Abe, are you planning on making another run of these boards? I'm hoping to build a second one in a 2RU chassis with switchable thresholds and few other bells and whistles.
Also: you wouldn't happen to know if a slight step-up, 1 + 1 : 2.28 transformer would be suitable for the inter-stage? The Lundahl LL1521B seems to come up for sale for decent prices used quite frequently. According to a doc on the Lundahl site: "The LL1521B is a high impedance line input transformer, very similar to the LL1540 but with a slight stepup."
Thanks!

Yes, Im going to get another run together  soon! Also yes that should be fine. ANY transformer will work (within reason) the only things changing will be gain and frequency response, also interestingly enough i found attack and release times changed with different transformers?? (answer me that one somebody!)
Best,
Abe

 

[labak]

Hi all!

I'm currently looking for a group buy of some power Xformers for this project!

Before a big thanks to DR-J and Kingston who did and helped it before!

Price is 33€ (Netto) + Shipping for one piece. Shipping 2-3 weeks after Order.

Specs : 230V // 20VAC 0.5A (opamps), 20VAC 1A (opamps + heater), 120VDC 50mA (B+)!!!

Same as DR-J already did.

Let me know who is in?

Best.

 

[ArnauTS]

I'm in for one for power trafo.
Was hoping for a new group buy run 

 

[labak]

Only 2 we are?

I'll send the order on Monday!

Best.

 

[WNStudios]

I'm in!

 

[labak]

Hi ArnauTS and WNStudios!

Look at you PM Boxes, dudes.

Best.

 

[baadc0de]

After putting the project on the backburner, coming back to it was easy;

faulty (intermittent) bypass switch, depending on horizontal-vertical operation. And a tiny weeny solder bridge with a via near R166 on the up (component) side of the PCB (missed that one since I was looking for bridges on the other side).

Thanks for the help, both problems were hinted at in this thread!

Cheers!

Hi baadc0de,

don't know if it may help, but I had this problems
http://www.groupdiy.com/index.php?topic=44586.740

Good luck!

ROCK-ON.

 

[prh]

Is there a circuit description somewhere for this project?  I guess a "canonical" thread is what I am looking for.

Thanks.  Paul

 

[astroschnautzer]

http://www.acsoundstudio.com/diyhosting/PRR_176.jpg

 

[supiarmando]

here we go! since this morning the unit running (after struggling with the LM350 because of temerature issue)!

 

[prh]

I am having trouble locating suitable tube sockets for the 6bc8 tubes.  I bought some 9 pin sockets from ebay, which are too large.  (I am a tube noob).

Can someone please post a link for the correct tube sockets? 

@Austroschnautzer:  thanks for the circuit.  I found an early article by PRR which provides the circuit description of the original circuit.

 

[abechap024]

I am having trouble locating suitable tube sockets for the 6bc8 tubes.  I bought some 9 pin sockets from ebay, which are too large.  (I am a tube noob).

Can someone please post a link for the correct tube sockets? 

@Austroschnautzer:  thanks for the circuit.  I found an early article by PRR which provides the circuit description of the original circuit.

Here:

http://www.ebay.com/itm/160580213397?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

and some nice holders so your tube don't fall out if your ship it or something:

http://www.ebay.com/itm/251037957427?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

 

[prh]

I am having trouble locating suitable tube sockets for the 6bc8 tubes.  I bought some 9 pin sockets from ebay, which are too large.  (I am a tube noob).

Can someone please post a link for the correct tube sockets? 

@Austroschnautzer:  thanks for the circuit.  I found an early article by PRR which provides the circuit description of the original circuit.

Here:

http://www.ebay.com/itm/160580213397?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

and some nice holders so your tube don't fall out if your ship it or something:

http://www.ebay.com/itm/251037957427?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Many thanks!

 

[astroschnautzer]

Question about fuse:  I  have 40VA transformer with three outputs, how to calculate fuse for this (I'm in eu, 230v mains).... I'm getting 0.17 amps with 40/230 mut that seems a bit small, can this be correct?


TS 40VA PRI: 230V SEC:
20V (1A)
20V (500mA)
120V (50mA)

 

[astroschnautzer]

Just got this working after some troubleshooting ( still though the other output transformer seems to be broken) , and it sounds awesome, best on vocals and acoustic instruments and plucky transients just as I was hoping to, its sounds like the 60's.

 

[baadc0de]

http://www.youtube.com/watch?v=HjP2e-bq4Ao
Sorry for the plug

The PRR176 is sounding great, sitting on the guitar (two gefell m582 through silentarts jensamp). Lots of other awesome DIY gear can be seen in the video.

This PRR in question has LL1540, moamps's melcor DOAs and RCA 6BC8s.

 

[abechap024]

Sounds great! Great work. Also these do have that 60's mojo,  the best kind! Glad you got them going.

 

[WNStudios]

My build is put on hold for a while, but i did manage to finish the front.