Another 124 build

[ayan]

Here's a few pics of my 124 (+/-) build. thanks to Funk for the great looking chassis.

I don't like the results of the cloth wire w/no wax (pic 4) so, I may change over to teflon.

Bob, a few thoughts for your consideration:

1. It seems you mostly use Xicon MF resistors. You may want to mix and match as those tend to sound pretty toneless if used top to bottom.

2. The slope resistor should definitely be either CF or a nice MF type.

3. I believe I have only seen one amp where the cathode resistors were NOT MF. You use CF in your amp.

4. I would consider losing the cloth covered wire now, before you go much further and kick yourself for not having done it sooner. It is so easy to use, cut and push back... but if you start making changes to the amp, it will look like shyte real quickly. BTW, vintage cloth covered wire was fine, but what is available nowadays is no good. I don't believe it's wax or lack thereof either, the material just seems to be looser.

Cheers,

Gil

[jaysg]

Gil,

I kind of recall Billy or you saying that 124 is a great sounding amp, but all the clones weren't making the grade. Any improvement or discoveries since then?

Should BobW switch the PI plate resistors to CF?

[ayan]

Gil,

I kind of recall Billy or you saying that 124 is a great sounding amp, but all the clones weren't making the grade. Any improvement or discoveries since then?

I don't believe I would have ever made a comment along those lines -- for starters, I haven't heard any clones. Also, I think 124 sounded fantastic, but I wrote that to me the amp was very brown sounding -- it needed a cap job before I heard it though, so Lord knows what it sounded like afterwards. Perfect amp for a blues guy, or Keith Richards type of thing, perhaps, but I couldn't get a clean sound out of the thing myself with Billy's LP.

I have my own copy of #124 and it really sounds nothing like the original -- -- but it just so happens to probably be the amp that has sound the best live for me, bar none. Used it at a gig a week and a half ago and was completely blown away by it, as was a very accomplished player (who lurks on this board) who came and sat in the band. A couple of guys form the audience came and talked to me about the "rig" between sets, indicating they'd never heard anything like it. It is the bomb live, extremely open sounding.

In contrast, at home it sounds poor and the lead channel with preamp boost sounds piercing bright. Also, without the Dumbleator -- as a couple of board members heard it during NAMM -- it's stiffer than any of my other amps. But, at the gig it's simply awesome and I would comfortably say that I would put it up against any other amp, including my own, knowing that it would do very well in a n A/B... situation. My best sounding amp at the moment, I'm inclined to say.

Gil

[ic-racer]

I have my own copy of #124 and it really sounds nothing like the original -- -- but it just so happens to probably be the amp that has sound the best live for me, bar none.

Gil

I'm currently in the process of trying my amp with various speaker/cab/guitar combos, I was wondering what you played through when getting that good 'live' sound.

Also, did you use 220k into 350k trimmer for the OD input in you #124?

Thanks

[ayan]

I'm currently in the process of trying my amp with various speaker/cab/guitar combos, I was wondering what you played through when getting that good 'live' sound.

Also, did you use 220k into 350k trimmer for the OD input in you #124?

Thanks

My choice is my trusty 1x12 open back EVM 12L cabinet. My OD input network is simply 220K + 100K trimmer, set at about 30+ K to ground.

Gil

[glasman]

Personally I've tried both ways, and notice absolutely NO difference.

So have I and with the same results. Except for wasting a couple of hours of time

[ic-racer]

But according to Mullard, for best noise performance in cascaded gain stages the second section should be used asa the first stage opins 6,7 and 8.

YMMV

Gary

Interesting, I was re-capping a 70s Fender Super Twin yesterday and noticed that it was also set up so 6,7,8 were used for the first stage. Until I built my clone, I had not paid much attention to this orientation on various amps.

[glasman]

But according to Mullard, for best noise performance in cascaded gain stages the second section should be used asa the first stage opins 6,7 and 8.

YMMV

Gary

Interesting, I was re-capping a 70s Fender Super Twin yesterday and noticed that it was also set up so 6,7,8 were used for the first stage. Until I built my clone, I had not paid much attention to this orientation on various amps.

Yeah, I am pretty sure that Mr. Dumble had a lot of "devine" inspiration .

[jaysg]

This all leaves me puzzled as to why KF used the 1 2 3 section for V2 on his amps. I also noticed that KF alternates heater wiring from tube to tube. I believe I've seen it in a Rivera. What did HAD do?

[BobW]

Bob, a few thoughts for your consideration:

1. It seems you mostly use Xicon MF resistors. You may want to mix and match as those tend to sound pretty toneless if used top to bottom.

2. The slope resistor should definitely be either CF or a nice MF type.

3. I believe I have only seen one amp where the cathode resistors were NOT MF.

Gil, I've got a few Carbon Comps to try as alternates. Would you recommend CCs for the slope and cathodes? Otherwise I can order more CFs. Thought I was OK with the Dales for the plates? Thanks for the insight, now is the best time to consider changes.

[Guitarman18]

ayan wrote:

3. I believe I have only seen one amp where the cathode resistors were NOT MF. You use CF in your amp.

Gil, if HAD frequently used MF's on the cathodes, have you any hypothesis' as to why he didn't stick with the RN65's (also MF's) in that position as well?

Sorry to hijack the thread BobW.

[heisthl]

My guess on the VD use is probably the same reason he didn't use them on the PI and my guess on that is it doesn't add to the tone (and may even be detrimentally bright and sterile) so why waste the money....besides it's fun to "feel" your way into some of these value choices and the VD resistors measure what they say (precision) unlike the standard MF and CF that vary around the marked values. To me it appears that HAD was a big proponent of measuring each part before he installed it with some "feel" for what he was going after, evidenced by the markings he made on his potentiometer choices and the ocassional bizarre resistor values (like a 1K3 in the D'lator).

[ayan]

Gil, I've got a few Carbon Comps to try as alternates. Would you recommend CCs for the slope and cathodes? Otherwise I can order more CFs. Thought I was OK with the Dales for the plates? Thanks for the insight, now is the best time to consider changes.

I really have no idea, Bob, I am merely relaying my humble observations. Dumble used CF for cathodes and plates, which suggest he wanted to make sure the tubes were biased precisely (1% resistors). People use MF on the plates for thermal noise considerations, but on the cathodes, I am not sure. I have used CC in the cathodes as well, for what it's worth.

Gil

[ayan]

Gil, if HAD frequently used MF's on the cathodes, have you any hypothesis' as to why he didn't stick with the RN65's (also MF's) in that position as well?

Sorry to highjack the thread BobW.

No idea. In the 90s amps, he ditched the RNs as well and used the same kind of MF throughout the amps... so who knows.

Gil

[BobW]

My opinion only, but believe this is one of the places in his circuit where HAD may have used a spectrum analyzer and his ears to dial in the cathodes. Once he found the sweet spot, using a trimmer, then went through numerous resistors to find the exact value.
Was it really the resistor types or just the exact value he needed, or both? I understand carbon composition, CC, resistors have no inductance except in their lead length, were used in RF circuits in the past, and sound great in Fenders, yet HAD never used them.
Based on Gil's and many others observations into real Dumble's, it seems HAD favored the CF at the cathodes. Now whether or not they will work for me, is another question. Maybe if I dial in the values that sound best, to me anyway, then play with MF, CF, and CC at the cathodes may help me understand why a particular resistor type does or does not. This probably was already answered in a prevous post, but I would like to understand/convince myself there may be more to it than tolerances.

Hey, I don't consider this thread highjacked, but in fact do appreciate all the comments here.