Layouts

[BobW]

Bobw, this will sound odd.. but would you happen to have the part #'s for the push/pulls you used? I look at mouser and digikey and get lost in a hurry..

I used 1M push pulls, from Magic Parts POT260. The body is smaller so you need to pre-position before you torque down on the chassis nut. Hindsight, it may have been easier to use toggles.

[Icetech]

k.. ill look for toggles.. im horrible at sourcing parts:) always end up with a pile of the wrong stuff...

[dogears]

Bob,

The pre-OD network change will really help. Either try a 220k over a 100k pot, or try a 220k over a lower load like 50k. Or maybe a 180k over the 100k pot. Experiment here.

Definately swap in a .005 OD2 cap.

I personally like something like a 1.5uf on CL2 and then use the 4.7 caps on OD1 and OD2. Maybe make the CL2 and OD2 bypass caps switchable so you are either fat in front or fat in back. I take credit for that one...

Maybe try a 150k/.001uf network to ground from the OD2 plate. Makes a nice tone. Smooths the upper mids.

You may like using something like .68 to .82uf on the presence cap. Every tranny is different. Some Elytics measure 10-20% big and that can harsh up the tone. Try a little smaller.

Report back.....

Leave me your emailo if you want off board advice.

Dogears, Here's what I've tried,

OD1 snubber 360pF
OD2 snubber 250pF
cathode caps 4.7, 4.7, 4.7+1, 1+1.
I may add a switch to one of the 1ufs on the last stage, it sounds great either way.
The best improvement was the .047 change to a .02 on CL2, made a huge difference.
Next I'll try a .005 at OD2, 10-15pF bright cap.
No real difference in the PI plate changes from 100K/110K to what was there. I redialed in the initial values w/pot.
Didn't change the odd network input yet, probably tonight.
Overall it's improved, will keep prodding when time allows.

[BobW]

Dogears, I think you are right-on about everything you mentioned. Was actually considering a change in CL2 as mentioned, since at high vol, the bass creeps in a little more than needed. Great suggestions. The switchable caps are another great option, especially with a Baker.
Too bad any more changes will have to unfortunately wait until I return from business travel.

[gar13]

Did you use the elaborate OD input section shown on your layout? Pictures on your website show a trim pot in that location. If so, what changes did you make?

[Normster]

Did you use the elaborate OD input section shown on your layout? Pictures on your website show a trim pot in that location. If so, what changes did you make?

I started with the network, but went back to a 220k and 100k trim. Now that I've got a few other things dialed in, I may throw the network back in just to see how it sounds. Maybe make it switchable? lol

[Noel Grassy]

[quote="dogears"]Bob,


Maybe try a 150k/.001uf network to ground from the OD2 plate. Makes a nice tone. Smooths the upper mids.


Leave me your emailo if you want off board advice. To clarify , may I assume paralleled[sp] 150K with the .001 cap? The network isn't in series is it? I really appreciate these tonal nirvana niblets you're so graciously serving us ! This is the best forum
I ever been a part of. Thanks again. Noel Grassy

]

[mlp-mx6]

Actually, yes, it is serial. The .001 comes off the plate, then 150K (or a 250K pot) goes from there to ground.

[skyboltone]

Thanks, just didn't initially scroll all the way down to find the jpg format.

Anyway, here's my layout of the REV A based on a SF Bassman. I removed the original fiberboard and replaced it with a turret board. Am still tweaking it after 4 months. Mostly in the grid stopper ckt of OD1. the 220pF sounds too gritty, so I recently changed to a .01uF and sounds closer. hth

Hi Bob:
You tweaked four months and then tweaked some more? Done tweakin?Have you updated your layout board .jpg? I'm getting one of Funk's chassis one of these days, and will likely start with your layout maybe probably. What do you think. Where are you at with it now? I've never built with a board. Always point to point.

Dan

[mlp-mx6]

Here's another layout option. Non-HRM, but you can stick the HRM off the plate on a separate board. (layout for that small board also on this pdf.) This is a Hoffman-style turret layout. Red lines are connections. One lead per turret, and I wrap wires around the turrets - MUCH easier to tweak this way...

This layout does not include the PI or effects loop - ONLY the preamp.

[skyboltone]

Thanks mlp-mx6. How do you pronounce that anyway? Just kidding, it's funny how you get used to following certain builders posts and refer to them in your head.

Maloop Mixsix

Anyway, I appreciate your experience and time devoted to this BBS

Dan

[mlp-mx6]

Maloop Mixsix

Hey Dan,

That's pretty funny. It's actually my initials, and the type of car I've owned since 1989. I may never retire her, she just won't wear out!! 215K on the original motor, tranny, and even original clutch! (not the original turbo, though) Most amazing to me, though, absolutely NO rust.

I'm glad to help in any way I can. I've received so much help - probably like most, a lot from Dogears - so anything I can to to reciprocate I will certainly do.

Michael

[BobW]

BobW wrote:
Thanks, just didn't initially scroll all the way down to find the jpg format.

Anyway, here's my layout of the REV A based on a SF Bassman. I removed the original fiberboard and replaced it with a turret board. Am still tweaking it after 4 months. Mostly in the grid stopper ckt of OD1. the 220pF sounds too gritty, so I recently changed to a .01uF and sounds closer. hth


Hi Bob:
You tweaked four months and then tweaked some more? Done tweakin?Have you updated your layout board .jpg? I'm getting one of Funk's chassis one of these days, and will likely start with your layout maybe probably. What do you think. Where are you at with it now? I've never built with a board. Always point to point.

Sky, I can honestly say I am finished with the layout and tweaks for this amp. The tone IS there, thanks to Dogears and forum chats with Normster and Bob-I. The changes from the layout initially posted include a change in the CL1,2 and OD1,2 cathode caps to the 5,5,5,(1+.47). Also I ditched the wierd OD entry and went with Dogears suggestions of a 180k over the 100k, and (This made a huge difference) replacing the snubber cap on OD2 with an adjustable snubber using a 250k in series with a .0012 ceramic cap to ground allows you to dial in the amount of rolloff. The iron is a stock Bassman. My only regret is that I did not include a reverb in the layout. (a future tweak, maybe) Normster has had great success with adding a tank inside the Bassman head. hth

[BobW]

Following Bob-I's suggestion and others, Here's my latest layout with the voltage readings with and w/o the 150k @ B+5. I liked the sound with the 150k installed, and did not have enough time last night to readjust the V1,V2 plate levels so for now here it is. I really should go back and try Gary Glasman's reverb ckt using Normsters layout. thanks to all.
(sorry it's zipped but my pixels exceeded the minimums)

[stevlech]

Do you intend for the snubbing network on V2b (OD2) to be connected to the grid? My assumption is that it should be connected to the plate. Just wondering...