183 Build Report

[ER]

They don't red plate, they purple plate...

[Structo]

Today I replaced all the orange drops with new ones that had the outside foil marked on them.
I used #183 values with the .05uF power tube grids.
And the .015uF 715 on V2a.
Plus I installed 250K pots in the Drive and Volume spots.
I put 47pf silver mica snubbers on V2 (all I had).

The first thing I noticed was more clarity on the clean channel and less hum, even when standing close to the amp.
In overdrive it was quieter as well so I can whole heartedly recommend marking the caps.

Bass pot is still rather touchy and I don't go above 10:00 with it.

But I am really liking what I hear so even with the 6L6 power section I think this preamp is a keeper.
I have yet to change the V2b output resistor to 180K but I have some PRP resistors coming so I will experiment with placement of those.

Anyway, that is this weeks flavor.

[CHIP]

Tom, Is your bass pot 500kB?
Glad to hear you like it so far and noticed a difference in the noise level. I plan on rechecking all my caps too. I built the foil tester switch box a couple weeks ago.

[bluesfendermanblues]

Tom, the bass pot value in the original #183, according to Shad and Tony's layout is 311K.

With a 500K pot you get 311K, if you solder a 820k resistor between pin 1 and pin 3.


BTW: I did this on my 183# build and with a 4 x EL34 output section, I still have plenty of bass at hand. So I might go even lower on that particular amp.

[Structo]

Thanks for the info.

I believe I still have a 500K audio there.

Logically, wouldn't the linear pot be even more touchy?

Because the audio pot barely gets off the full value until around noon.
Seems like the linear pot would have even less of a rotation before the bass got heavy.

I have a 250KB I could try and shave.

When I have simulated the tone stack, about the only way I saw that lowers overall bass was to go to a 200K slope resistor.
Changing the bass pot to even 250K didn't result in much less bass.

[bluesfendermanblues]

Logically, wouldn't the linear pot be even more touchy?

Yep

[CHIP]

Thanks for the info.

I believe I still have a 500K audio there.

Logically, wouldn't the linear pot be even more touchy?

Because the audio pot barely gets off the full value until around noon.
Seems like the linear pot would have even less of a rotation before the bass got heavy.

I have a 250KB I could try and shave.

When I have simulated the tone stack, about the only way I saw that lowers overall bass was to go to a 200K slope resistor.
Changing the bass pot to even 250K didn't result in much less bass.

Tom, Sorry I wasn't specific, but
I installed a 300k audio pot that measured 312K. My old 500kB pot was barely higher than 9 o'clock before the bass got to overpowering.
Now it's at almost at 1 o'clock and that's where I like it.

[David Root]

Ultra, what is your PT? Does it get the specified 465V plate @idle?

The Mag Components Twin PT only gets 440V plate @ idle in my #124. That's a significant difference and I'd like to get it right when I do my #183.

[UltraHookedOnPhonix]

Ultra, what is your PT? Does it get the specified 465V plate @idle?

The Mag Components Twin PT only gets 440V plate @ idle in my #124. That's a significant difference and I'd like to get it right when I do my #183.

Hey David,

Yes, I get 462V loaded B+ from the custom wound Heyboer PT. The bias is set at 30mA per tube which amounts to about 60% of static plate dissipation (around 56% for the real 183 as I recall). That's fairly cold!

I ordered the PT from Jason who also sells really nice ODS PCBs. You'll find his Amp Garage screen name in my first post of this thread.

[Joost]

BTW, I see you have wires running across the relays, which are a source of noise. Doesn't this cause problems and tone loss?

Also, how do you approach lead dress around that area with all the tone control wires running from the preamp board to the pots around the relay area?

[img768]http://i205.photobucket.com/albums/bb17 ... n/Pic6.jpg[/img]

[bolomule]

Seriously nice build and pics. How do you keep the chassis so clean? My projects always have flux splashed all over the place.

[grtamp]

HI Joost , excelent build , compliments!!!!
Can you tell me the code of your trimpot? they are from mouser?
Thanks

[Joost]

HI Joost , excelent build , compliments!!!!
Can you tell me the code of your trimpot? they are from mouser?
Thanks

it's not my build, sorry. I asked a question about this build to the OP regarding lead dress around the relays

[UltraHookedOnPhonix]

BTW, I see you have wires running across the relays, which are a source of noise. Doesn't this cause problems and tone loss?

Also, how do you approach lead dress around that area with all the tone control wires running from the preamp board to the pots around the relay area?

[img768]http://i205.photobucket.com/albums/bb17 ... n/Pic6.jpg[/img]

Well, those wires aren't routed any differently than those found in a real ODS. The amp is very quiet and doesn't pop with either relay engaged.

I wasn't aware of relays being a source of noise and that routing wires in this fashion could cause problems, including tone loss. Please tell me what these problems are and how an electronic switch is inherently noisy.

The wires coming from the pre board snake around the preamp ground and behind the PAB relay, just like Dumble did it. In fact, using the JLDDI approach is something I try to follow rather closely.

[ToneMerc]

The wires coming from the pre board snake around the preamp ground and behind the PAB relay, just like Dumble did it. In fact, using the JLDDI approach is something I try to follow rather closely.

Phonix, you sure are a modest man my friend
I think you do one better than "JLDDI"

Mike