#124 CAP QUESTION

[rogb]

Sven, you've got me thinking the same thing

I've decided to get a pair of 100uf and stick them in to replace the (expensive) 220's I have there now. At this stage it's an easy swap.

My reasons are; I have a 50w #102 with 220's so I'm curious to try this #124 with less filtering.

Also, looking at the 50w 3rd gen amp it's a low plate amp with 100k slope just like the #124 so not a million miles away.


anyway, we've got two #124 threads going consecutively here will be interesting to compare notes as we go along

Marcus

Definitely a good idea to try low filtering, remembering Tony's #102 "Feedback City", a Classic with 50uF, bloom and noteflip may become more apparent, who knows? Good luck anyway

[ToneMerc]

As for the CAPACITOR question, I am still undecided: If a 100 W Dumble amp has a total of 150 uF capacitance in the first section of Power supply, what should be capacitance of a 50 Watt version of that amplifier, half of that (75 uF) or one third of that (50 uF) or somewhat more than half of that (100 uF)? As a fellow up in this thread stated, THERE IS NO PRECEDENCE FOR A 50 WATT AMP. What really changes with smaller or larger capacitance? I used to know that some years ago, but I forgot it (if I ever actually knew it, I wander, ha, ha, ha...).

Again not all 100W ODS amps had at least 100 or 150uF of mains filtering and there was at least one Dumble quad 6V6 ODS, I'm willing to bet it had the lower filtering as well. There is precedence for the 50 watt amp topology, look at the "early gen" amps with the "classic" tone stack and a pair of 6L6's.

Don't make this harder than what it needs to be....LOL. It's your amp experiment. For a 50 watt ODS, I have gone as low as 40, 20, 20, 10 and 10 across the board.


TM

[Sven]

Well, quite frankly, I do not really know what would be difference in performance and sound of such an 50 Watt amp if it had 100 uF as opposed to 50 uF of filtering in the first stage. We only know that the original had 150 uF in the first stage for 100 Watts, while the rest is up for grabs... If I knew what is the difference between 50 and 100 uF, it would be easy to make up my mind. I doubt that I could HEAR the difference if both options are tested side-by-side in two same amps... Well, that is why this thread is called ¨#124 CAP QUESTION¨... All things considered, it seems that it does not matter than much anyway (?) ... perhaps (?) Thanks for your input, everyone ...

[erwin_ve]

Sven: 100uF has tighter bass, 50uF has a loose feel. It feels very different. For my 50W ODS I have 60uF, enough punch and not too stiff.

[talbany]

Well, quite frankly, I do not really know what would be difference in performance and sound of such an 50 Watt amp if it had 100 uF as opposed to 50 uF of filtering in the first stage. We only know that the original had 150 uF in the first stage for 100 Watts, while the rest is up for grabs... If I knew what is the difference between 50 and 100 uF, it would be easy to make up my mind. I doubt that I could HEAR the difference if both options are tested side-by-side in two same amps... Well, that is why this thread is called ¨#124 CAP QUESTION¨... All things considered, it seems that it does not matter than much anyway (?) ... perhaps (?) Thanks for your input, everyone ...

Here is my .002 cents worth

I don't think I have ever seen a 50w Dumble amp with more than 50uf..I have seen several 100w with only 50uF..
The best sounding 100w ODS I've built only had 50uf..
Remember 100w AB763's (Showman/Twins)only had around 50uf on them..

IMO it really depends on how you run it!!
If your the type player who can get away with really cranking the amp (to the point of taxing the PS) and your finding the low end going real loose on you and ghost note-ing then upping the filtering on the plates makes sense!!
If not then I wouldn't go there because the price you pay with over filtering is you begin to choke off the amp as it gets stiff as well as lose the amps ability to sustain at lower volumes..So you not only get a tight amp but possibility of a slightly more life-less sounding amp..(the same can be said with PI over filtering)..
IMO there are better ways to tighten up an amp like lower bypass caps or turn down presence control, raise the voltage on V1 or add in some LNFB V1 or go to a high plate design,lower the value of the pots in the OD circuit..Some of the fine tuning points Dumble has been known to use to tighten up an amp..(Also cap orientation has been known to help tighten an amp a bit)

A kind of analogy to me would be the suspension on a car..If your driving at 120mph your going to need a tight suspension..If your only going 55 the benefit is not as obvious and you get a rougher ride..So filter it how you run it!!.If this makes any sense!!..I hope!!

Tony

[Sven]

ROMA LOCUTA CAUSA FINITA EST! Rome has spoken, the case is finished!

Rome has spoken... ha, ha, ha... thanks Mr. Tony, you and the previous responder, ¨erwin_ve¨, have nailed it. So, 50 uF it shall be. Good news, too, since I already have a couple of 100 uF 450 V F&T caps...

[dorrisant]

Thanks for that Tony... I'm gonna order new reservoir caps for my 50w hack at a #124.

Glad to see you posting!!

[norburybrook]

I've got an extra set for my #102 coming as well. IT will be interesting to do a before and after

I'm surprised it's taken this long for this topic to be talked about. I built my 50w #102 two years ago and there was no mention of filtering on the build thread. I'd done a LOT of research as well before I started and didn't see anything mentioned by previous 50w builders.

So thank you Sven and Tony for bringing this up.


M

[Sven]

While still on the topic of 124, I would like to see if there is a more clear layout regarding connections to DEEP and JAZZ/ROCK switches. The layout that is now present for quite some time on a DUMBLE FILES thread about 124, is very confusing as to how these switches are wired. I wander if there is a better picture of those connections somewhere on this forum?

Ceriatone layouts are excellent as far as their visual quality, CLARITY is concerned and DEEP switch that they present is here, but it is DIFFERENT than what seems to be (?) a DEEP switch wiring of 124 layout found on DUMBLE FILES section.

QUESTION: Since I do not care to have ¨Jazz¨ option, what would be the hard wired scheme for just ¨Rock¨ sound circuit? Is there such a scheme on this group? (I have searched and have not found it...)

[ToneMerc]

I've got an extra set for my #102 coming as well. IT will be interesting to do a before and after

I'm surprised it's taken this long for this topic to be talked about. I built my 50w #102 two years ago and there was no mention of filtering on the build thread. I'd done a LOT of research as well before I started and didn't see anything mentioned by previous 50w builders.

So thank you Sven and Tony for bringing this up.




M

The topic has come up before here, using the keywords "filtering" or "50uf" will yield lots of results, you just have to wade through it all.

http://ampgarage.com/forum/viewtopic.ph ... light=50uf

http://ampgarage.com/forum/viewtopic.ph ... =filtering

http://ampgarage.com/forum/viewtopic.ph ... =filtering


FWIW, here's a couple of my quad 6V6 or EL34 pair 50 watt builds with the lower filtering

http://ampgarage.com/forum/download/file.php?id=24025

http://ampgarage.com/forum/download/file.php?id=18485

http://ampgarage.com/forum/download/file.php?id=20258


TM

[norburybrook]

Sven checkout my 102 build there's a layout Martin did for All rock and no jazz.

M

[Sven]

Sven checkout my 102 build there's a layout Martin did for All rock and no jazz.

M

Where is that sch.?

[larsvictor]

Ceriatone offers both versions of a (kind of) midboost switch in some of their amps. Both are dumble-style. The switch on the right in your ceriatone layout - labeled "deep" - is the midboost/deep switch in older Dumble amps like the ODS #40 or the SSS. The "modern" version of the midboost switch is that one in the middle of the ceriatone layout. Unfortunately this one is labeled "deep" in some amps - quite a bit confusing. They do sound a little different.

Lars

[vibratoking]

Sven checkout my 102 build there's a layout Martin did for All rock and no jazz.

M

Where is that sch.?

I mean no offense to anyone, but I find it interesting that guys can get a full amp built and working without the basic knowledge to modify the circuit for rock only. I don't understand that thought process and I wonder how serious injuries are avoided. I hope everyone is working safely because there is a potentially lethal high voltage in there.

[Sven]

Yes, it is offense but not to me, it is a picture of the one who makes such comments! Because there are MANY WAYS to do certain changes, while it is a GOAL to get the closest to what Dumble style change and modification would be like IF it is desirable at all (?) and so on and so forth... it is a matter of very fine, very delicate fine-tuning, which some people, obviously, do not understand.