My 5F6A build vs. others

[Jester]

Hi Guys, MWJB

I've been playing around with my 5F6-A, and just tweaked the tone cct as you mention here and I ended up today with the original design with two .02uF caps in the cct, rather than the later design of 0.1 and 0.02 uF. In my case I think it has helped clean up the lower end (I think I was getting some early break-up of the bass notes at a low volume.)

The reason for me jumping in on this thread is to ask about your comment:

To give you an idea though, 5F6A's may have been fitted with 0.1uf or 0.022uf bass caps, they may have had 100K or 56K treble slope resistors, etc. A lot of builders would skip the 8uf preamp filter and go straight in with 20uf (reissue uses 40uf). There's a bit of room to move whilst staying true to the 5F6A mold.

I realise that upping the preamp filter will improve the transient response of the supply at this early stage. I just wanted to ask what effect this has on tone? I have previously experimented with the main power supply filters, and found increasing these on an early champ amp, had a fantastic improvement to the bass response. Is it similar here too, or is it something else?

I'd also like to hear from people who have changed the power supply filters on the 5F6-a. Mine now has two 220uF /300 V F&T caps. in series, with the 220k Ohm resistor in parallel across them both. I guess this has improved the bottom end a bit, and I'm wondering if I should change these back to the two physically much larger (and costly) Sparague 20uF / 600V caps. The reason I'm thinking of this is that my amp still has the bass breaking up first when I strum hard on medium volumes (4-5). I was hoping to keep a clean sound down at this volume, accepting the break-up only at higher levels. I also want to keep a firm bass (so don't really want to back of the bass tone) for the quite playing. I've also read that some people claim the F&T caps are not that good, and that physically larger caps (like Sparague) sound better in valve amps. So here my question is who prefers what when it comes to main filter caps on the 5F6-a and why? Do smaller value Sparague caps manage to sound better than the larger value F&T caps (which are physically only about 1/2 the size for 11 times the capacitance value, albeit at 1/2 the voltage). Look forward to hearing from you guys.

Jester

[MWJB]

Where will you put the Sprague 600v caps? They're typically much too long to go in a stock Fender style chassis. You'd need 5 of them to get the 100uf you have at the moment. I really wouldn't bother.

You could try a larger value than 20uf at the screen supply, say 40-50uf? How about a solid state rectifier?

Setting the amp at "4-5" means very little, pot tapers vary greatly, having fixed perceptions of how loud the amp should be (in db) at a specific number on the dial will not be helpful. Original bassmans tend to ramp up pretty quick on the volume pot.

F&T caps are plenty good.

[Jester]

Where will you put the Sprague 600v caps?

Well there's a question I don't have a stock chassis, but a large aluminium Hammond Box, and I could get a couple in there to go to the original 2*20uF filtering, or maybe even 3*20uF - but as you say no were near enough room to put in 5 more monster sized caps. I already have two in there for the other filters. Maybe I should look elsewhere to reduce the early break-up of the bass as you say - maybe rather than hi-jacking this thread, I should start another. Thanks for your answer.

Jester

[Paul P]

The only place you might need 600v caps are the first filter stage. The
caps further down the line can be lower voltage like 450 or 500v.

I understand that the big 600v Spragues are actually two seperate caps
placed end to end inside the plastic tube. With no equalizing resistors
(how do they get away with that ?). So you could be better off using
two 350v caps anyway.

Paul P

[Jester]

The only place you might need 600v caps are the first filter stage. The
caps further down the line can be lower voltage like 450 or 500v.

I understand that the big 600v Spragues are actually two seperate caps
placed end to end inside the plastic tube. With no equalizing resistors
(how do they get away with that ?). So you could be better off using
two 350v caps anyway.

Paul P

Paul
Please correct me if I'm wrong but the original cct diagram showed 20uF / 600 v caps in the first three filter positions. When I first powered on the amp, with only the rectifier in place. I measured voltages of 540-546 volts across each of these three filters. Yes I agree when i put the tubes in, and bias the amp these values come down to 350 - 480 volts, but I think that when caps fail they can be catastrophic, and so I would not want to design them at lower values, which mean that standard fault finding techniques (like pulling a tube, or two) can run them over voltage. Unless I'm missing something that would be dangerous wouldn't it? Or am I missing something?

I had not hear that these caps had two inside, but I guess they are big enough. I was just wondering if the tone of them was any different - some of the books I've read rave about this type of electrolytic cap, and slag off Illinios caps (and have even read bad things about F&T), so am pleased to hear some people think they are okay.

I know it should be down to my ears to tell if they are any good, but I don't want to waste the time and money if others have tried these things and don't think they work.

Cheers
Jester

[Paul P]

Paul
Please correct me if I'm wrong but the original cct diagram showed 20uF / 600 v caps in the first three filter positions.

I also misunderstood the labeling of the caps and bought a bunch of 600v
caps (which cost a fortune). Those caps are not "600v" caps but "600P"
caps, the P standing for 'peak'. So really they are rated at 424v.

Paul P

[Jester]

I also misunderstood the labeling of the caps and bought a bunch of 600v
caps (which cost a fortune). Those caps are not "600v" caps but "600P"
caps, the P standing for 'peak'. So really they are rated at 424v.

Paul P

Thanks for pointing that out Paul. I had miss read the cct diagram and purchased the expensive 600 v caps.

At least I've learnt - thanks.

Jester .

[MWJB]

Foe less presence you could switch the 5K pot & 0.1uf cap out of the NFB circuit altogether?

[tweed5259]

So it's been a while playing the amp now, and I still feel as though I'm lacking that certain balance in tone of the clones I've heard. I've found that a lot of these Clark, Victoria, and Kendricks have an acoustic type sound to them when played with a telecaster. Meaning they sound very even and have a singing quality when you strum a chord, this is certainly something mine lacks, mine is more stiff, and harsh. mine sounds in between a fender reissue LTD and a Clark.

I really do not believe there's some secret ingredient in these boutique amps I'm just not sure what I'm doing differently in my build, ah, frustration.

Bias is good, voltage problem fixed, speakers and tubes broken in, good quality caps and resistors, MM OT and Choke, the only thing left is the PT which is a fender reissue. C'mon, what's the secret?

[MWJB]

"I really do not believe there's some secret ingredient in these boutique amps" Why not? If you had built 100 bassman amps don't you think that you'd get better at it?

Clarks, Victorias & Kendricks don't use MM OTs. What else is different between your amp and the high end repro's? Even typical examples of the 3 manufacturers you mention weill sound different to each other.

[yankeerob]

I've made a 5F6A clone (of sorts ) from the chassis, iron and cab from a '98 HR Deville... as their were a good handful of compromises to be made in marrying the Deville PT and power stage to the 5F6A front end it really doesn't qualify as a 5F6A in that regard - a few things I did find - however - were that spending money on Sprague or F&T filter caps was a folly - I've used the same caps that Weber use in their kits with v. satisfactory results - it's my belief that filter caps play very little - if any - part in the overall sound of an amp. I've used these far less expensive caps in other amps with success - and have found that there is as much chance of finding a leaky F&T (I'd already bought some that were badged 'TAD') as there is in these cheapies... what I have found to be of greater significance is selecting coupling caps and resistors - I've gone to using Vishay Roederstein polyester film (the same caps you'll find in the limited edition handwired HiWatts) which are quite similar to Mallory 150's in appearance - and pretty standard carbon film resistors but sub 1W's for 1.2W's and 2W's for 1W's etc. This in combination with a couple of NOS Brimar's in the V1&2 results in an amazingly clean (bags of headroom) and quiet amp (signal to noise) that is as happy in a studio with a mic in front of it as it is on stage (one engineer asked if I was using a gate!) the PI is just a JJ ECC83S and I use Winged C 6L6GC's - this is not a good solution if you are looking for early breakup and distortion - I get 36W@4Ω, 24.5W@8Ω - both measured at 1Khz - it's not as loud as a Matamp GT100 - but it pees on just about everything around here for tone and clarity - all I do is set everything at 12 oclock, link the ch's, crank the normal ch full up and start with the bright ch at around halfway - it usually winds up around 2-3 oclock - and use a BlackStar HT-Dual DS-2 for a bit of dirt when necessary - job done

[tweed5259]

"If you had built 100 bassman amps don't you think that you'd get better at it?"

I do believe I'd get better at it, I don't believe that there's some off schematic part that they've all got the tip on and that's making the difference.


So what OT's do they use? I know they do all use Paper Bobbin OT's and my mercury is plastic bobbin, and according to a certain person I spoke with named who's initials are Gerald Weber that's the end all tone solving difference...

Which I'm not sure I believe. AHHHHH!

I should just buy a clark and enjoy it.

[MWJB]

I guarantee you, that 100th amp would sound different to the first.

Firstly, as they all use different brand parts, yes you're right, there isn't one part that they all have the 'tip off' on. But what comes with building, modding and listening to lots and lots of amps of broadly the same type, is the opportunity to tweak various parts and most importantly, the layout, to ensure consistency (to a greater degree than any mass produced amp) and that the finished product matches the builder's expectation of what THAT amp should sound like.

It's then the purchaser's perogative to buy the one that they think sounds best.

Have a look at the positioning of the tubes on the Clark bassman, look at the routing of the wires on the Kendrick...these things are all the product of honing the basic design whilst remaining true to the original intent. This is something that is often overlooked by novice amp builder (you can only see how & where the basic components join together on a Fender schem/layout - there is not enough information between the 2 of them to guarantee a working, trouble free great sounding build)...sure you can go and copy an original Fender amp but you might listen to 10 amps that all sound a little different, use slightly different values AND in some cases these might have had quirks ironed out in the test shop before they hit the market. You can be sure that Victoria have done some ironing out of the build, within the perameters of what's regarded as an 'original' bassman amp design.

If you showed your finished amp to any one of ther builders you mention, there may well be things that all of them might point out as being wrong in their eyes. "Yeah, we used to do that, but..."

Clark uses "custom wound" transformers, Kendrick obviuosly use Kendrick ones. They all appear to use different brands of coupling/tone caps.

I'm not going to say that you definitely need this brand or that brand of OT, all the guys you mention will have their own reasons for using what they do (5F6A OTs were wound on paper, but Kendrick specifically have made no secret of the fact that they have sought to change materials from the original amp to get it how THEY want), but I would have a long look at the details of your build...it's a common mistake to be dissatisfied with a build and blame this or that specific component/brand, whilst missing the bigger picture/an important detail elsewhere in the circuit.

Malt scotch is a good analagy here, when a still reaches the end of it's servicable life the new version is often copied right down to every dent & defect in order to retain consistency...this is what boutique builders do, find their way of doing things over the years, refining & honing to ensure constency. If you work from a Fender schematic/layout the best you can do is build a "still" that was as the designer originally intended, maybe not what has proven successsful over the years. Sure, there's bound to be some emotionally driven decisions (you might say snake oil, I couldn't possibly comment), as well as financialy driven, but the proof of the pudding, as you're discovering, is in the eating.

Do you have any detailed photos of your build?

[tweed5259]

I'm gonna start a new topic just for this layout, I think it'll help a lot of people if I document this experience.

[yankeerob]

I guarantee you, that 100th amp would sound different to the first............Sure, there's bound to be some emotionally driven decisions (you might say snake oil, I couldn't possibly comment), as well as financialy driven, but the proof of the pudding, as you're discovering, is in the eating.

I 100% agree with MWJB's post - the notion that this or that particular component is going to radically change things for the better is pure conjecture - I posted a few of my preferences and observations - MWJB has put it quite eloquently - unfortunately - for us mere mortals it's a case of suck it and see - the only way to learn anything in the business of choosing your materials is usually the hard way... the point of it all - hopefully - is to have fun doing it and expect a few bumps along the way - they're not all bumps though - sometimes it's that warm feeling when you've nailed something for yourself - then that's what you go with next time... don't give up and enjoy it as much as you can