My Latest Build (Progress Thread)

[Weathered]

So, since I use this site for all kinds of technical knowledge, I figured I'd show you all what I'm doing with that learning.

I've long been a fan of the AC30/Matchless vibe in an amp, but sometimes long for more grit and girth in the tone. I had thought about pairing the first stage of a Matchless Lightning to a Marshall-voiced second stage and tone stack into a cathode biased output section of 4 EL84's. Upon researching this, I found that that was the basis for the Top Hat Club Royale, so now I figure that my build is going to be similar to that, but with 4 EL84 instead of 2. The two changes I've made to the CR schematic are:

- the second gain stage won't have the fat switch - it'll simply be a 100K plate and .68u/1K5 Ck/Rk
- I'm going to install a PPIMV to make it a little more home friendly (I don't gig much right now)

I'm also going to swap the 1K2 in the PI to an 820R - I've found that the traditional Vox PI gets fizzy when it's overdriven.

I do have one question regarding the schematic - there is a voltage divider going into the PI - after the 220K coming from the treble pot, there's a 150K going to ground. This isn't present in the Rocket/AC30 - wondering if it's really necessary to have that in this amp, as the PI is pretty much straight AC30 (possibly due to the changes to the tone stack?)

I'm using the RJ Rocket chassis and Rocket xformers. Headshell was done by AmplifiedNation.

Here's the progress so far on fitting preamp parts (the power supply is on a board that I'll install after I mount the transformers, but since I don't have an amp cradle, I'm doing most of the preamp/power amp wiring before dropping the transformers in).

[img:799:478]http://img.photobucket.com/albums/v243/ ... AG0067.jpg[/img]

And here's the headshell:

[img768]http://i817.photobucket.com/albums/zz97 ... CF4564.jpg[/img]

[diagrammatiks]

solens for all the cathode bypasses?

[Weathered]

solens for all the cathode bypasses?

No, just the second stage .68. First stage is a Sprague electro 22u/25v (V1 is going to be paralleled - 220K plate/22u-1K5 Ck/Rk).

[diagrammatiks]

ahh kk. looks like the other two are tone stack then?

[Weathered]

Yep - .022 for bass and mid.

I'm also trying the PRP resistors - ordered a few of them from PartsConnexion - they made it to me in 3 days. I was surprised about that to say the least.

[diagrammatiks]

nice. lookin good.

hmm i wonder if you could have fit a 22uf film cap for the first bypass.

[Structo]

Do you have the schematic for this amp?

Does it have a LTP PI?

The 150K sounds like a grid leak resistor.

You may want to go a little bigger on the first stage bypass for more gain and kick.

Or is the first tube paralleled together?

[Weathered]

Do you have the schematic for this amp?

Does it have a LTP PI?

The 150K sounds like a grid leak resistor.

You may want to go a little bigger on the first stage bypass for more gain and kick.

Or is the first tube paralleled together?

The schematic that I'm working from is linked in this thread:

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

on page 2.

First stage is paralleled, PI is a standard Vox LTP.

[Reeltarded]

Have a Tophat CR at the studio.. umm.. you are going to want more late gain based on your description! It has distortion on the front end, but the backside of it doesn't do much to compliment any instrument I have tried with it.

Have a '63 AC30 too. Breathes fire, no fizz. The CR is like a mentos/diet pepsi fizzer.

[Weathered]

Have a Tophat CR at the studio.. umm.. you are going to want more late gain based on your description! It has distortion on the front end, but the backside of it doesn't do much to compliment any instrument I have tried with it.

Have a '63 AC30 too. Breathes fire, no fizz. The CR is like a mentos/diet pepsi fizzer.

I'm thinking that going from an unbypassed V2a with an 820R to a .68u/1K5 should help to boost the grunt - I can always start adjusting the V2a bias to get more dirt if needed.

The PA in mine will be more or less straight AC30/Rocket - 100R screens, 50R/220u cathode bias.

[Reeltarded]

heh ok! I just saw the description in the background of what it seemed like you are going for! I know what this thing sounds like.. umm. I like Emplex, but the CR is a.. umm.. it's not for me and guitar. Great for mid smoothing a standup bass, or pretty much anything with a thumby lowend though. Bass drum flattener.

Love the cab, and the strips! It's a good look all around.

[Weathered]

Well, we're making progress.

[IMG:799:478]http://img.photobucket.com/albums/v243/ ... AG0068.jpg[/img]

The preamp tube sockets are wired. I had just enough space to get the whole preamp/PI onto the strips - if I weren't putting in a LarMar MV (which means that I don't need the 220K bias feed resistors on the board), I'd have had to slide things over.

Next up - wire in controls, wire up power tube sockets, and then transformers and PSU board.

[Weathered]

Another update - making slow but steady progress.

[IMG:799:478]http://img.photobucket.com/albums/v243/ ... AG0076.jpg[/img]

[milkyBK370]

Looking good. Absolutely love that head shell.

[Weathered]

As a belated update, had first power-up last night. Worked on first power up with no weird issues - all stages are grounded independently, and the filter cap ground is tied to the same point. There is almost no noise apart from the sympathetic buzz from the fluorescent lights overhead. I actually couldn't even tell it was working when I powered it up with tubes until I had the volume over halfway up.

[IMG:799:478]http://img.photobucket.com/albums/v243/ ... 4248_n.jpg[/img]

Current issues to work through:

1. The tonestack that I have in here is not what I want - I used the Top Hat tone stack as a template, and adjusted values, and it is not doing what I want it to do. Thinking I'll swap it to traditional Marshall values and tweak from there.

2. I think the .68uf ck on the second gain stage is a bit much - once I adjust the tone stack, I'll start tweaking this stage. It sounds good when about halfway up on the volume (using the Lar-Mar MV to knock down the overall loud factor), but past that, it gets a little grainy. Hoping to smooth that out a bit.

Overall, it sounds about how I expected - like a JMP and an AC30 had a baby. Thinking that with my tweaks above, it'll be where I want it to be.