6GW8 Parallel SE

[TIMBO]

Hi guys, Looking at doing something simple.



Questions...
What OT primary am I needing and what power rating.
 

[tubenit]

I like that idea!  You sure come up with some cool stuff!   

With respect, Tubenit

[sluckey]

Do you have a stash of 6GW8s? They are kinda pricey over here. About $60 each.

[shooter]

What OT primary am I needing and what power rating.

need a 2nd opinion, but looks like ~RA 24k, so 1/2 ~10k-ish, so a 5K using a 4ohm skr on 8ohm tap 

power-wise, a low range would be 15W, go up from there

when I get some time i'll try and hunt down a data sheet

[shooter]

while rooting around the web I found this paper by your neighbor, might help?  It's PP, but PSE specs should be "close enough"

https://dalmura.com.au/static/Australian%206GW8%20PP%20amp.pdf

[tubeswell]

What OT primary am I needing and what power rating.

need a 2nd opinion, but looks like ~RA 24k, so 1/2 ~10k-ish, so a 5K using a 4ohm skr on 8ohm tap 

Yes - the pentodes are rated at 9W. For centre-bias class A, running at (say) 300V:

300/(9/300) = 10,000R.

2 in parallel would be 5k.


As to power rating - figure about 40% of (2 x 9) = 7.2W. 2 or 3 more watts above this would be a good margin of safety ;-)

[TIMBO]

Thanks guys.

Sluckey, I have a few 6GW8s left, but my supplier has a stack of 14GW8s

He's looking to get some transformers wound to accommodate the 14.5v heaters.

[TIMBO]

The reverb will be a work in progress, as the Belton brick is something I want to try.
After rummaging through my discarded builds I was able to find a few bits I could use.


The chassis has been sitting on the shelf for so long I can't remember why I had it bent like that.
WASTE NOT WANT NOT


 

[TIMBO]

Hi guys, Some progress.....





Just waiting on the OT

[kagliostro]

 

Franco

[TIMBO]

Thanks Franco.
Guys I had another think about the heater supply.
I using a 1A transformer that ahs 6.3v and 12.6 taps and I will be adding a 12AX7 to the 6GW8.

Would this be a better circuit.

[TIMBO]

Hi guys, Tweaked the circuit some and fired up well, sorta.

The back to back transformers under load did not have the expected 300ish output  :crying:
A bit of head scratching and connecting the 18v tap on the first transformer to the 12v tap on the second transformer helped greatly.

Still not quite 300v but good enough.

[tubenit]

Timbo,

As always, thanks for sharing your info and schematic!   

How does it sound?

with respect, Tubenit

[TIMBO]

Thanks T, This little amp sounds like a BIG amp.
Had a muso give it a whirl and I was very impressed.

Plenty sparkle and great bottom end.

Would work well with 6BM8s

[TIMBO]

Hi guys, After much tinkering I think I've got this one done.
Adding the Belton reverb brick was a bigger job than I thought.

If you like plenty of reverb these bricks are great and sound pretty good.

I need to do some tiding up and I'll get some pics.


If there is anything I should not have done please tell me, as it was very much trial and error addon.

[TIMBO]

Hi guys, put the finishing touches on the circuit.







Overall I think this one has turned out pretty good.
Does clean to mean very well with great reverb.
Cab is under construction as we speak.

[uki]

Sound sample pls ?! 

[TIMBO]

Will do ASAP.

[TIMBO]

Hi guys, The "CHICKABOO 10" is complete.





Will work on some clips soon.

[shooter]

true craftsmanship! 

nicely done

[bmccowan]

Super nice! I'll be interested to hear some sound clips. Parallel SE amps have their own charm.