Slow Progress

[justinsweber]

I decided to use the templates laid out by more exp builders, pairing the Getset with 300b output tubes.

Im waiting for the PCB and parts, but the transformers have made it in and are mounted.

Transformer compliament includes:
2 CXSE25-8-5K output transformers (10 lbs each)
Wattage 25W
Max. Current 200mA
Primary (input) Impedance 5K Ohms
Primary (input) DCR 85 Ohms
Primary (input) Inductance 50H
Screen/Grid Tap 40%
Secondary (output) Impedance 8 Ohms
Secondary (output) DCR <1 Ohm
Frequency Response 20~20K Hz., <1dBu


1 XPWR005-120 Power Transformer
Power transformer for 660V (330-0-330) at 180mA center tapped and two 6.3V at 2.5A.


2 C354 cokes. 55 ohms, 1.5 henries, 10% tolerance, 2500 volt DC hipot tested, 200 ma DC.

I can’t afford tubes yet, but should be something to behold when done.
Shannon was kind and found the 5watt 1.5ohm resistors I needed. I bought 4 for $2 and paid $8 for shipping. Ouch!
The sockets are antique electronic supply $25 each... no idea why so much, but will allow for under mount and a clean look up top.

[justinsweber]

Is it possible to include a stand by circuit?
Maybe one of the automated units from ebay.

[Ty_Bower]

I decided to use... the Getset with 300b output tubes.

Transformer complement includes:

1 XPWR005-120 Power Transformer
Power transformer for 660V (330-0-330) at 180mA center tapped and two 6.3V at 2.5A.

The XPWR005 has two 6.3 volt heater windings, which is perfect for 6B4G or 6A3 tubes. However, the 300B needs a 5 volt heater. Is that what you are going to do with the high wattage 1.5 ohm resistors? Simply use them to drop the excess voltage? Ah yes, now I see. I should have read the 300B sticky first.

The sockets are antique electronic supply $25 each... no idea why so much, but will allow for under mount and a clean look up top.

Chinese UX4 sockets sell on eBay for $11 a pair, shipped.

[TerrySmith]

If your using SS diodes instead of the 6AX5, just add CL90 in the primary circuit. A good spot is between the power switch and transformer pri lead.

[TerrySmith]

WOW! $25.00 for a plastic UX4 socket? I would seriously call AES if you already have these sockets, Angela sells them for $1.99.

[lth1]

Justin,

To include a standby circuit, I have gone to using separate filament and B+ transformers, and using John Broskies AC switch.

"The three positions are: all transformers off, transformer 1 on and transformer 2 off, and both transformers on. With this setup, you can turn on the heater transformer first, so the tubes are given a chance to heat up, which will create an electron cloud over the cathodes, protecting them from the B+ voltage.

$7.00"

This is an extremely positive and inexpensive way to build a standby circuit or switch. By using a separate filament xfmr it also makes it easier to play around with 6 or 12 volt tubes.

Lee Hankins

[justinsweber]

I already drilled the hole for the power stitch I will use :-(.

Far better to ask in advance. Least I got the 2 chockes mounted :-0.
The CXSE transformer was used becuase of bandwidth. I use big cornscala's that get into the low 40s. The GXSEs seemed flat compaired to my McIntosh gear. Im hoping for SE bliss, with the buy in of the big Edcor transformers. Seems over kill 25watts for a 5watt 300b, but I wanted full bandwidth. Maybe I shoudl have had them build some 15watt 20hz-20khz ones. Again, more questions in planing might help me:-).

About the SS rectifer idea. I think Ill stick with tube rectifer. Ease the load on the 300bs.

Does the 6AX5 allow for slower warm up like the GZ34?
I was always told that the 5AR4 was a better choice for my ST70 as it allows the voltage to come up slowly instead of the 5U4GB

[Shannon Parks]

Does the 6AX5 allow for slower warm up like the GZ34?

Yes, it has the slow warm up of a 5Y3.

Shannon

[justinsweber]

With the heavy transformers, we spent some time and had reinforcements for the chassis built... no bowing now. I need a few resistors and we can start wiring. Once built it will be a mo or so before it can be tested... Need to save for tubes :-(.

[Shannon Parks]

Nice compartmentalized setup. Which 300Bs will you be using?

Shannon

[justinsweber]

I had assumed EH300Bs, but would love some sugestions.

I just used tubesandmore.com to get the 1626s and 12SL7s for my other project.

[justinsweber]

My budy Tom Meza helped clean all the wires up nicely... can eat it off it now.

[justinsweber]

Like a dumb ass I put R15a-R15c and R16a-R16c on the side with the C1... I bought some very very cool Wima caps that need all the space you can give them... as a result... I will build another PCB and put the resistors on the right side and my cool ass caps on the oposite... Maybe Ill hear no diff. I can fire this bad boy up for a mo or so... bought the transformers for the Clem... and thus no extra cash for 300bs.

[justinsweber]

WIth the Wima Caps on the new PCB, Ive ordered my EH300Bs... should have this bad boy up and running in a week.

[Shannon Parks]

All the Wima caps I've ever tested have worked very well. Looking good!

Shannon