NAD ( modded JCM800 content )

griff10672

griff10672

Well-known member
Built myself a Friedman JEL 50 ( JCM800 channel only ) in a small box format

just like the USA 800's back in the day ..... this one is running 6550's ( Sovtek )

all Sozo Mustards .... Vishay Beyschlag Metal films ....

also added DC Heaters for the first two pre amp tubes ( used one of Jeremy's / Ground Zero boards )

and one of my own Zero Loss Metro style FX Loops .....

grabbed a smallbox from Sourmash .... stripped and retolexed it in Plum Gator

Faceplates and Emblem were done using my new Laser I bought for the shop
 

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7704A said:
Is that considered hot? 6550's are 35W tubes, 42W for some like the Sovtek 6550WE's, and 39 mA is only 18.64W at that plate voltage. So somewhere between 44% and 53% dissipation.
Click to expand...

Ah, I was thinking it used EL34s. I set my EL34 at 38mA.
 
7704A said:
Is that considered hot? 6550's are 35W tubes, 42W for some like the Sovtek 6550WE's, and 39 mA is only 18.64W at that plate voltage. So somewhere between 44% and 53% dissipation.
Click to expand...
according to everything I've read ...... the 6550's when in a " 50 watt " amp like in a 2204 ..... should be treated as 25 watts each when biasing ... because that's what the transformer is designed for ....
 
lespaul6 said:
do you have a depth circuit? what nfb configuration?
Click to expand...
yes ..... it's built to exact specs according to Headfirst's modified 800 schematic which Jason says is the 800 channel of the JEL

it has a 4n7 cap and a 220K coming off the 4 Ohm tap going back to the amp

7704A said:
Awesome, love 6550's in these things.
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I also have a Ceriatone 2204 running EL34's ...... they both sound great ..... but the 6550's just add some friggin push and girth the EL34's don't ....
 
Well @griff10672 you're a lot braver than I ever would be with this stuff. I would always be afraid I would lay my hand down in the wrong place without being aware of it. Very cool that you know how to create your own boards.
 
my experience with doing pedals has definitely made it easier for me to build an amp .... from soldering skills ... schematics ... grounding schemes .. etc

I've been considering doing some PCB's for amps .... but I really love the turret boards ... some amp companies mix the two which I think looks sick ....
 
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