New Build and 102 thoughts:

[Raoul Duke]

So I’ve been playing my 102 everyday for almost a week now and I’m still discovering new things about it. When Marcus said it is a truly versatile amp - he hit the nail on the head! Here’s a few random opinions:

1. The amp sounds better the louder I play it; and there are a number of ways to play it loud. I realize it will be settling in for awhile, but it is really fun to tweak and explore.

2. The cleans are pretty amazing. The middle position on my Les Pauls has never sounded so distinct. With literally every other amp I’ve played - middle is either too much bridge or too much neck. Clean setting in 102 balances them better than I can ever remember hearing and has its own full sound. Really amazing to play.

3. The presence control is super subtle. I may be partly to blame because I used a 33pf in place of the 68pf, so I may opt to try the 68 in the future.

Took a break earlier and dug into my 2nd Gen parts box which got me thinking about a few ideas I’d be curious to get some opinions on:

1. Forgot I have a bag of about 50 unused brown drop caps I bought at a flea market a few months back. Sorted through them and I have every value needed for this project. Some are El Menco, some are El Menco with the CDE stamp. I searched here for these and see they might be a good choice. Any thoughts on that?

2. I’m a big fan of Martin’s boards and am leaning toward incorporating at least his power supply board into this build for simplicity and proven design. Any reason why I shouldn’t?

3. I want to stay as true to the design as possible, but I’m curious about the following circuit variations:

a. Push/pull bass pot for switching the .02uf cap in/out. Read about it in one of the 2nd gen hybrid builds and it seemed like a way to get some 3rd gen flavor as an option. Dumb idea?

b. Is there any advantage to including some of the later “HAD upgrades” such as a presence pot, master volume, or OD trimmer on the board? My understanding is these might be nice to include - but it’s important that the amp retain the 2nd/3rd gen character and I’m not sure if these differences will affect the end result negatively.

Just in the “thinking about and getting organized” phase, so any random thoughts or anecdotes are very much appreciated!

Thanks,
Marc

[martin manning]

3. The presence control is super subtle. I may be partly to blame because I used a 33pf in place of the 68pf, so I may opt to try the 68 in the future.

Huh? 102 has 68p for the master bright. 2u2 on the presence cap.

1. Forgot I have a bag of about 50 unused brown drop caps I bought at a flea market a few months back. Sorted through them and I have every value needed for this project. Some are El Menco, some are El Menco with the CDE stamp. I searched here for these and see they might be a good choice. Any thoughts on that?

Probably ok, but you'll wonder "what if" you had used 6PS Orange drops...

2. I’m a big fan of Martin’s boards and am leaning toward incorporating at least his power supply board into this build for simplicity and proven design. Any reason why I shouldn’t?

All ODS are more alike than different; the same boards will work for virtually any of them. There is extra space on the board for the so-called "funky OD entrance" of the early ODS amps.

3a. Push/pull bass pot for switching the .02uf cap in/out. Read about it in one of the 2nd gen hybrid builds and it seemed like a way to get some 3rd gen flavor as an option. Dumb idea?

As long as the mods include the original circuit, I wouldn't be afraid of including them, but recall the adage bells and whistles will probably wind up unused.

3b. Is there any advantage to including some of the later “HAD upgrades” such as a presence pot, master volume, or OD trimmer on the board? My understanding is these might be nice to include - but it’s important that the amp retain the 2nd/3rd gen character and I’m not sure if these differences will affect the end result negatively.

See above, but PI trimmer is always a good idea, IMO. Accent switch is just fixed presence, which you can adjust to your liking.

[rootz]

I wonder if that presence control is also that subtle on 9 or 10? These come on rather slow in my experience. 2u2 and 68pF master bright should be plenty bright and also a lot thicker when louder.

Not sure if a 3rd gen/102 hybrid would work, as the 3rd gen and skyline differ in quite some places. Could you tell what the aim is? More scoop? Shifting the mid dip?

[dbharris]

I'm starting a 2nd Gen build now and using mostly brown drops. I am really going for that Lindley tone and since his amps were so early on, I am assuming a sort of transition assortment of parts from the 1st to 2nd Gen may have been used.

I thought it might give this amp a more unique voice since I am going to end up with a 102, 2nd Gen, Low Plate Classic, and Blues Master.

Also some old builds by Tonemerc are really fantastic using the brown drops.

If I hate it, it's not that hard to change the caps.

P.s. if you inspect the 2nd Gen pics we have closely, you can tell the orange drops are not all the typical 6PS caps...many are the orange drop di-film which would be a similar construction to the brown drops.

-Dan

[Raoul Duke]

Oops!

Yes Martin, I misspoke. I meant the master bright - which now that I say that - it isn’t affected by the presence pot, is it? Still learning, lol.

I’m still trying to figure out the “funky OD entrance”. I don’t quite understand it - so I don’t understand the controversial points of this 2nd gen characteristic. Also meant to ask about the PI balance. It would seem like a good idea I think (even though there’s no power amp in)?

I was thinking if I used your power board, I could eliminate what I think is the B+4&5 stand alone filter on the back wall. Is that the funky OD entrance and am I barking up the wrong tree with my idea here?

Rootz - the presence is most noticeable between 7 and 10 to my ears. It’s there, just not what I’m accustomed to. Also, I’m trying to build a 2nd gen with the 3rd gen bass value switchable, not a 2nd gen/102 hybrid. To your point - that doesn’t sound easy to figure out. I’m just trying to get a textbook 2nd gen sound with a few practical options built in.

Dan - I’ve read Tonemerc’s builds and saw that. It jogged my memory because there are a few original bags in my stash that state “di-film” on the packaging - so it connected the dots in my cranium so to speak. Because of that, I figured I’d ask.

Thanks guys, I appreciate all the input! I’ll continue to ponder these things, lol…

[rootz]

That sounds a lot like the presence in my amps; comes on slowly but gives a big treble boost though. It's been a while since I touched my other non Dumble based amps, so can't compare.

I missed your point about the 22n cap completely, but understand it now. Yes, it will work. The pot values differ a bit too, so some adjustment of them might be in order after switching. I agree with Martin though: might be a switch you could miss. Pretty easy to solder in and out the cap too and just stick with whatever config you like most.

Not too experienced with 2nd/3rd gen amps, but the entrance looks like a combination of a low pass (output impedance of v1b and 470pF cap), high pass (10n off V1b with 220k to ground, followed by a 1meg2 to 33k voltage divider. So tone shaping and attenuation.

And I'd love to know how El Menco's sound in a 2nd/3rd gen. Any Dumble actually.

[ijedouglas]

Those El Menco brown drops sound pretty good. I have only tried them in the Mid cap position on a #0102 build and it sounded much better than the 6PS. No reason they shouldn't make a great sounding amp.... easy enough to swap out. I believe the actual #0102 used a cap similar (or the same) to the EM/CDE Brown Drop

[martin manning]

I meant the master bright - which now that I say that - it isn’t affected by the presence pot, is it?

Nope ;^)

Also meant to ask about the PI balance. It would seem like a good idea I think (even though there’s no power amp in)?

The balance trimmer is used to balance the power stage (remove 2nd order harmonic distortion), and that's what you want regardless of whether it's being driven by the preamp or from an external source.

I was thinking if I used your power board, I could eliminate what I think is the B+4&5 stand alone filter on the back wall. Is that the funky OD entrance and am I barking up the wrong tree with my idea here?

Correct, and no, the funky OD entrance on the 2nd Gen is the network feeding the OD first stage grid, 500p//220k to ground, 1.2 meg, and 33k grid leak in Tony's layout. The preamp board for the later amps can be used to make a 2nd Gen, but since you are fabricating your own boards you can easily make one to match the 2nd Gen layout. Be aware that the long span for the cathode RC's may be too long for your parts; check before you drill.

[Raoul Duke]

Ahh, see; a valuable nugget (among many valuable nuggets) that would not have occurred to me until after I’d made boards and was sitting there saying “these leads aren’t long enough, WTF?”

Thanks Martin!

How does the 2/3 gen design account for PI balance? Just through the circuit design and choosing a well-balanced tube?

Ian,
I wondered in Tony’s 102 layout what that mid-cap was. That’s definitely good to know. I have the old Aerovox in there now, but I’m still making up my mind. Thanks for the info

[martin manning]

How does the 2/3 gen design account for PI balance? Just through the circuit design and choosing a well-balanced tube?

Balanced tube, and choosing the right values for the plate loads.

[Raoul Duke]

Might have a power transformer for this build. Fender Tweed Bassman reissue (new/uninstalled) with the following (unloaded) specs:

120 primary
5.2 rectifier
374-0-374 ht @250 ma
57.8 bias supply
6.96 heaters

Look right? Never seen heater supply at 6.96 so I thought I’d get some opinions. Is this common?

Also - regarding using Martin’s PS board - should I keep the values in the (100w) board plans or switch to dual 100uf plus 20-20-20 (no B+5) and keep the resistor values indicated in Tony’s layout (2x220, 2k2, 27k) in order to stay close to the original circuit and its desired performance characteristics?

Yeah, I’m hooked…

Thanks in advance!

[martin manning]

The RI Basssman PT will put out more voltage than you want, close to 500VDC. I'd look for something with a 325-0-325 secondary.

The Second Gen has a stacked reservoir (2x 100uF, B+1), and then four 20 uF filters (B+2 thru B+5), with the last mounted on the back of the chassis near the preamp end. It's up to you to decide whether you want to make something that looks like the layout, or use the same power supply board you used for the 102 and keep all of the filters together. Either way I'd keep the values shown in the 2nd Gen layout (modern caps will be 22 uF, though). For the dropping resistors, it shows 2k2 and 27k on the main PS board, and a 2k2 on the B+5 filter. Recall the first 2k2 might need some adjustment to get the preamp voltages correct.

[bepone]

Might have a power transformer for this build. Fender Tweed Bassman reissue (new/uninstalled) with the following (unloaded) specs:

120 primary
5.2 rectifier
374-0-374 ht @250 ma
57.8 bias supply
6.96 heaters

374V is too high..

[Raoul Duke]

Thanks guys! I’ll keep looking around; obviously no hurry. The 325-0-325 spec is somewhere around Deluxe/Vibrolux territory if I’m not mistaken?

Martin, thanks and understood regarding the values. I’d prefer to keep everything on the one PS board just for simplicity sake. I wouldn’t think the location of the B+5 filter would affect the sound/behavior of the amp as long as the values are consistent with the layout (and correct for the individual amp).

Going through 2nd gen build threads and trying to see the different approaches. I like Erwin’s implementation of a PI trimmer. Probably “borrow” that

[ijedouglas]

Going through 2nd gen build threads and trying to see the different approaches. I like Erwin’s implementation of a PI trimmer. Probably “borrow” that

I seriously considered doing that on my 3rd Gen. I even built the board but after chatting with another builder, whose opinion I deeply respect, he told me it wasn't really necessary. I went without the trimmer on his recommendation and I can't say I miss it.