chassis and caps

[mike7]

Hey all
I searched and couldn't find this info.
Ordering parts and am wondering what size chassis to buy for the 5f6 bassman? Also after looking at caps has anyone tried the MOD, auricaps or musicap from AES? I know they are expensive but if they are worth it why not right? Maybe? Maybe not? OK back to loading turrets.
Thank you for any insight you can offer
Mike

[martin manning]

If you are building a 4x10 Bassman then get a 5F6-A replica chassis. Weber, Angela, Triode, and Mojo sell them. If it were me I'd use Mallory 150's (now CDE) for the coupling caps.

[gldtp99]

Get many sizes of blank chassis here: http://www.turretboards.com/

I use a lot of Mallory M150 caps in tube guitar amp builds----- there are no magic corksniffer parts dusted with special mojo dust that will instantly transform a build using standard grade parts into tonal nirvana.
But you can use any parts you want to----- it's ok with me-----some parts just cost more and are intended for use in Hi-Fi tube amps (music reproduction) and offer no real world advantage in a tube guitar amp----- tight and sterile are not qualities that most guitar players look for.
M150's are popular because they sound good in vintage tube guitar amp builds---- In a tube guitar amp (music production, not reproduction) a given part, with less impressive specs that the hi-$$ part, can sound much better because of its inaccuracies----- often we hear this as Warmth, greater Harmonic Content, etc.
This actually is a form of distortion but it sounds more pleasant to most human ears.
But, in the end, what matters most is what you think of the sound of your finished build---- and if using expensive parts makes you feel better then the finished build will sound better to you, even if it makes no difference (or sounds worse) to others.
Experiment, listen, change parts, etc until you come up with the combination that you believe is the right sound for you.......................gldtp99

PS--- having said all that, the signal/coupling caps I'm using in the current build on my bench are Sozo Standards----- I also use Mojo Dijons, Xicon MPP's, OD 715's, and some Military Surplus, and others------ but I use M150's more than any other brand. They sound good.

[martin manning]

BTW, if you do use a repro chassis, using turrets instead of eyelets will be an added strain on an already tight fit, and possibly result in interference problems with the input and speaker jacks.

[mike7]

Martin
That makes sense. I didn't realize the difference of those types of caps. Would 2 inches be deep enough for the chassis? I don't want my head cab to be a square by the time you add tube height.
Well all I can do is try it and see what happens.
Thanks again.
Mike

[martin manning]

So you are doing a 5F6-A in a head cab (kind of like a JTM45, eh?). Are you starting from a blank chassis? Following a published layout?

[mike7]

I am going to follow the fender layout. Not sure about the selenium rect. And I am going to omit the ground switch due to the use of a grounded plug of course. I wanted to split the 220k resistors at the bias point(?) And install a bias pot for each tube. Is it as simple as that though? I was thinking about a head and a 4-10 cab but it would probably be better in a combo as far as traveling goes. I really love the 59RI bassman so maybe I should stick to a combo. With that in mind I better use the correct size chassis too huh? Any idea what size it is? If I have to do an eyelet board it's no big deal I have to order caps and iron still.
Thanks
Mike

[mike7]

Oh and yes I am starting from scratch.
Mike

[M Fowler]

Either prepunched Marshall JTM 45 or blank chassis 17.5 x 6 x 2.5 from Turretboards.com. Mojotone also has a blank JTM 45 chassis.

Mark

[martin manning]

I think I pointed you at this once before? The layout has an adjustable bias mod, and definitely use a 1N4007 for the bias supply rectifier... Separate bias adjust for each tube will basically require a duplicate of everything after the diode... probably not worth the trouble. The 4x10 arrangement is a big part of the sound, IMO. https://tubeamparchive.com/viewtopic.ph ... 321#226321

[mike7]

Yes martin you did. I went to download them and found I already had them. Sorry about that.
OK so after much research I am once again baffled. Should I buy the "original" fender iron or merc magnetics, mag components, etc.etc...... being the most expensive part( s) I don't want to get myself into trouble in this area. I'm not really concerned with price I want THE best tone I can get. Everyone seems to have the " best" sounding iron

I' m still stuck on wanting to be able to bias each tube seperately for some reason i don't understand! Haha maybe I should just get it built and worry about that later huh?
I would like the ability to swap tubes if I want is all.
I'll put that on the back burner for now.
I am going to build a head version after looking at those small chassis for the 5f6a. I am not confident I will be able to squeeze everything into that small a space and not run into a
few problems on a first build.

Thanks for putting up with my PITA questions.
Mike

[martin manning]

Note I updated the "Modernized 5F6-A" build guide today... I read through it again and found some garbled text in the power-up and test section, which I fixed and further improved.

Separate bias on the power tubes will let you match the idle current on unmatched tubes, so has some usefulness. Since you are building a non-traditional layout, you can make room for the extra components. A single bias adjust and test points which are accessible from outside the chassis will let you swap tubes and re-bias very quickly.

IMO, Mercury transformers are overpriced. Magnetic Components or Heyboer would be fine, and certainly compare favorably to the transformers used in the reissue Bassman.

[mike7]

OK, had to go to Fla to work for a month but now I'm back.
This 5F6a build being from scratch leaves me with this question: no ground switch. So I planned on running the neutral from the power cord straight to the neutral of the PT,soldering and shrink tubing the connection. Then the line straight to the 3 amp fuse. Would that be OK to do?
Also, this would be on down the line but I normally only use the normal channel of an amp so could I make this a channel switching amp and mod the bright channel to my liking and switch between the two? Or omit the bright channel but still use both halves of the 12ay7 to thicken up the tone or install a switch for such a mod? I know, I know, I'm a beginner and have these stupid ideas but I just love music and tube amps and I get so excited about it. Please forgive me for all these pain in the @$$ questions.
Martin thank you for the very nice layout you provided. It has helped me so much!!
Mike7

[mike7]

Would 20uF caps be OK instead of 22uF for the filter caps for a 5f6a build? I am looking at Sprague's and can only find the 20's. I can find Illinois caps at 22 but they are so cheap that I question their stability. Am I wrong? Or can anyone suggest another brand?
Thank you all very much
Mike

[martin manning]

20 vs. 22 uF is not a big deal. Illinois are ok according to reports here on TAG. If you want to spend more, I'd go with F&T rather than Sprague.