(Mark3+Poseidon)*(2) Question

for Dynaco Mark II/III/IV and DIY PP monoblocks

(Mark3+Poseidon)*(2) Question

Postby ChrisK » Fri Sep 18, 2009 1:09 pm

First, thanks to everyone for their patient and extremely useful replies to all my questions. I'm attempting to build a project that combines all the great ideas that I've come across in this forum and from others. If this works out, I'll be happy to share the details.

I thought it's time to post a progress report and ask for some more advice at the same time.

The concept is to combine two monoblocks into one (really heavy!) unit. Here's what it looks like so far:

Image

I was going to use SDS cap boards with GZ34's until I discovered PSD 2 and realized that voltages would be out of whack with the Antek AN-TK400. Sheldon's design uses eight 68uF caps, Triode sent me the kits with eight 100uF caps, and PSD said: "This just ain't right, we can do better"! I was advised to try the 5U4 and, after running a bunch of simulations, I came up with this cap board:

Image

The first C stage (34uF) is not shown but will be located on a turret board underneath the tubes together with some ground tap diodes and snubbers. From the top down, LCLCRC should work out to 480/430/330VDC and a 300V preamp tap (give or take). In series, caps will be rated at 800V. Good so far, but then I discovered that the 5U4 specs said 3A for heaters instead of the 2A I had. Yep, yet another mid-course correction resulted because I didn't RTFM.

I bought two shielded 5V 3A transformers, but the only space available was between the OPT's:

Image

Now I'm starting to wonder if they're too close to the OPT's and/or oriented properly. If it's advisable, I could relocate the soft start relay and realign the filament transformers on a mid-line between the OPT's to provide a little more clearance. Or maybe I'm just obsessing (again) over nothing.

Your thoughts/critique/ comments would be appreciated. I'd like to start wiring things up this weekend, but maybe I need to refabricate some stuff instead?

Thanks,

Chris
User avatar
ChrisK
 
Posts: 115
Joined: Sun Mar 23, 2008 5:57 pm
Location: Laguna Beach, CA

Postby mesherm » Fri Sep 18, 2009 3:38 pm

Your OPTs are Z mount and the 5v filament trannies are shielded which are both pluses so I think your ok as is. If that black plate behind the 5v trannies is steel and is too close you might get some buzzing from the filament trannies though.
Mike's N-1 Rule: When looking for N number of components to finish a job, you have a 95% chance of only finding N-1 of them.
User avatar
mesherm
KT88
 
Posts: 1232
Joined: Fri Aug 27, 2004 10:33 pm
Location: Alvin Texas

Postby ChrisK » Fri Sep 18, 2009 3:48 pm

mesherm wrote:Your OPTs are Z mount and the 5v filament trannies are shielded which are both pluses so I think your ok as is. If that black plate behind the 5v trannies is steel and is too close you might get some buzzing from the filament trannies though.


Thanks, I'm glad to hear that.

Yes, the black plate is steel. It's sole purpose is to stiffen the wooden case and to provide a place to mount chokes. There's only about 1/4" clearance between the transformers and the steel. It would be fairly simple to get maybe 1/2" or even 3/4" at this stage of the build, but I have no feel for whether that would make a difference.

I can leave as is for now, give them a little more space or deal with it later. If buzzing develops it would be fairly simple to remove and refabricate in aluminum.

Regards,

Chris
User avatar
ChrisK
 
Posts: 115
Joined: Sun Mar 23, 2008 5:57 pm
Location: Laguna Beach, CA

Postby ChrisK » Fri Sep 18, 2009 4:11 pm

mesherm wrote:If that black plate behind the 5v trannies is steel and is too close you might get some buzzing from the filament trannies though.


Would it make any sense to wire them up and load them with the 5U4 heaters as a quick test? Would that alone cause the buzzing you mentioned?

Chris
User avatar
ChrisK
 
Posts: 115
Joined: Sun Mar 23, 2008 5:57 pm
Location: Laguna Beach, CA

Postby ChrisK » Fri Sep 18, 2009 5:15 pm

ChrisK wrote:
mesherm wrote:If that black plate behind the 5v trannies is steel and is too close you might get some buzzing from the filament trannies though.


Would it make any sense to wire them up and load them with the 5U4 heaters as a quick test? Would that alone cause the buzzing you mentioned?

Chris


I just resolved any potential buzzing issue (I think). I pulled out the steel plate and replaced it with aluminum.

Seemed like the easiest thing for me to do.

Chris
User avatar
ChrisK
 
Posts: 115
Joined: Sun Mar 23, 2008 5:57 pm
Location: Laguna Beach, CA


Return to poseidon

Who is online

Users browsing this forum: No registered users and 19 guests

cron