#124 CAP QUESTION

[echo44]

Hi another newbie question
at the v1 cathode where there is a 10uF cap in parallel
with a 1.5k resistor does it matter the brand of cap?
I was going to use a Vishay aluminum electrolytic
10uF 50V?(its all I have) or should i order something different?

oh yeah one other
on the 100k metal film is it ok they are .5w
at the plate

[Structo]

You should try when possible to use the same components as HAD did.
I know in some cases that is impractical nowadays but try to use the same specifications as what he used.
It will help it sound like the real deal.

So you can still get the Vishay RN65D metal film resistors for the plates, they are listed as .6 watt but they are Mil Spec and are good up to 1 watt. Hit up Mouser for those.

As for the cathode bypass caps, generally you want the lowest voltage value that will work and since there is only about 1.5-2v on those caps a 16v or 25v cap is fine though sometimes hard to source these days.
Your 50v caps are probably fine.

Try to use metal film where HAD did and carbon film where he put them.

A good metal film and what I used is the Vishay/Dale 71-CCF60 series. See Mouser, just enter 71-CCF60 in the search bar and it will take you to them.

The coupling caps are pretty important to keep as SBE 6PS 600v.
You can get those at AES:
http://www.tubesandmore.com/scripts/fox ... EE04=0600V

Good luck and have fun!

Tom

[echo44]

what do you recommend for the 4.7uF in parallel with the 1.5 k
as always thanks

[echo44]

i can only find these at mouser for the 4.7u
they are actually 5u

[Structo]

Vishay/ Sprague has a good rep and the TVA series is low leakage.
But they cost more.
Here is the 5uF
http://www.mouser.com/ProductDetail/Vis ... VPJSpF0%3d

Here is the 10uF.
http://www.mouser.com/ProductDetail/Vis ... 4zbteH4%3d

Nichicon is getting good reviews now for E caps.

It's difficult to source axial caps more and more because everything is PCB so the market is for radial caps which you can use, they just don't look as good on a eyelet board.

Here is a Nichicon but the lowest it goes is 50v, which is fine.

http://www.mouser.com/Passive-Component ... 20Rating|0

When I played around with bypass cap values, I found the 10uF too bassy.
But, my amps are high plate so it may not be the same for #124.
If it were me I would buy enough 4.7-5uF to do both channels in case there is too much bass.

[Sven]

Schematics show that 0124 amp uses 2x 300uF caps in series for a total of 150uF in the first stage for a 100 Watt amp based on 4x 6L6 output valves. What would be capacitance of these first two caps for the same amp but built for a 50 Watt version based on 2x EL34 output valves (active one valve FX loop included in the amp)?

[ToneMerc]

Schematics show that 0124 amp uses 2x 300uF caps in series for a total of 150uF in the first stage for a 100 Watt amp based on 4x 6L6 output valves. What would be capacitance of these first two caps for the same amp but built for a 50 Watt version based on 2x EL34 output valves (active one valve FX loop included in the amp)?

If one follows the earlier Dumble lower wattage amps then it would be 50uF or so. I have built a couple of 50 watt D'lites with 110uF on the front and maybe five to six 40-50 watt various Dumble circuit clones using only 40-50uF on the front end. My personal opinion is that 110 makes the smaller wattage amps a little stiff for my tastes, however your mileage may vary.

The Dumble MusicMan supply amps with a quad of EL34's also had lower filtering.

TM

[Sven]

Thank you! So, my conclusion is that in order NOT to have this amp stiff, I should use 2x 100uF electrolytic caps wired in series, which totals 50uF for the first stage, right? If that is right, than it is looking good since I already have 100uF F&T caps. Thanks again. Sven

[norburybrook]

I'm building the #124 low plate classic. If you look it has a half power switch so the filtering would be the same on the 100 or 50w.

I've used the same filtering for a 100w and a 50w and don't notice any difference in stiffness.

again YMMV

Might be interesting to experiment.

you're right about axial caps getting harder to source. I've not built for a year and things have changed in that year!





Marcus

[Sven]

I am also preparing to build (my friend is going to be actual builder) a 124 clone, but on a new thread dealing with that build author ignored my question as to WHICH SCHEMATICS are correct? There are two schematics in DUMBLE FILES thread but I do not see which one is used nowadays since those are old files...

As for the filtering, I have 100uF 350 W F&T axial capacitors, so I wander is it OK to use two of these for a total of 50 uF of capacitance for the first stage for a 50 Watt amp with 2xEL34 output valves? According to the above advice, that is OK. Right?

[norburybrook]

there are two versions of #124. the original low plate classic and the updated skyliner.Just check the schematic against the layout for the differences.

Its up to you which to build


I'm going for the original low plate classic as I already have a skyliner amp.



M

[Sven]

Thanks. I also want an original 124, not the skyliner. Would that be this schematics named #124 schematics (as opposed to the one below named #124 schematics 1984) or is it the one below named #124 schematics 1984? Which one of the two?!

http://ampgarage.com/forum/viewtopic.php?t=5719

[norburybrook]

Sven,


It's written on the schematics which is which.

the classic original is the 1984

the other one is the Skyliner version,


it's written in the little box at the bottom right on both schematic.


M

[bluesfendermanblues]

Thanks. I also want an original 124, not the skyliner. Would that be this schematics named #124 schematics (as opposed to the one below named #124 schematics 1984) or is it the one below named #124 schematics 1984? Which one of the two?!

http://ampgarage.com/forum/viewtopic.php?t=5719

The first one (1988) is the "skyliner" and the second is the classic.

The main difference between the two is the slope resistor/ mid cap combination. 150k/10n ind the skyliner vs the 100k/47n in the classic.

My personal preference is skyline for humbucker and telecaster guitars and classic for strat. Therefore, I have installed a switch under the chassis in order to be able to switch between the two.

[norburybrook]

interesting. what about the different mid pot value, surely that has a big effect on the tone? also no master bright cap, I've found the master bright cap to have a significant effect on the overall tone, obviously dependent on value

so you can switch between the two different caps and slope resistors combinations but use the same mid pot.....which mid pot do you use, 250 or 100k?


Marcus