Metro 100 Watt MV Build

[gldtp99]

I've started building up one of the two Metro 100 watt MV kits I bought just before Metro stopped selling amp kits---- I've had these two kits in storage for quite a while---- I've been too busy with other scratch builds, conversions, amp service, etc to start one of these--- this will be the very first amp kit I've ever built.
This one will use a Marstran T-2562 PT because I had to pull the Metro dual voltage PT from the kit to do an emergency PT replacement on a friend's JMP 2203------ the one I pulled from the kit was the only 100 watt Marshall PT I had on hand.
I used reinforcement brackets from ClassicTone to mount the PT and OT and used longer bolts and larger washers inside the chassis to make a better, more secure mounting for the heavy PT and OT transformers---10/24 x 3/4" machine screws and Nylok nuts----- trimmed the ends of the machine screws that are under the turret board to eliminate any possibility of arcing.
Using the CE 50/50uF@500V cap cans supplied with the kit----- I have F&T's on hand but I've used the less expensive CE's on some builds and they seem fine.
The circuit won't be stock on this one------ it will be modeled after a 25 watt, 6V6 x 2, 2204 type head I built with ideas stolen from several posts from very smart people on this forum. Not the AFD/Slash type mods----- it will also have the Metro FX loop that I ordered with the two kits-- I debated using 4 preamp tubes (chassis is punched for 4 preamp tubes) and building a 3 and 4 gain stage preamp similar to a 50 watter that I built up last yr----- the Lo input feeds 3 gain stages and the Hi input feeds 4 gain stages, inputs wired to allow real time A/B switching between input jacks----- this 50 watter has been rented out for recording and performace uses several times and I just got it back from a band live use rental because another band wants to rent it for recording in the studio across the hall from my workshop.
But I decided to only use 3 preamp tubes so that I could use the Metro turret board supplied with the kit------ the planned circuit mods fit the standard layout without any changes.
Depth mod and PPIMV are being thought about------ i'll build it without them and see how it sounds first.
I'm finally building an amp kit !!!!!---- ............................gldtp99

[gldtp99]

Ok---- the Forum is Back !!!!
After long delays keeping me away from my workshop, I finally powered up this build for the first time last night.
Went to bias the supplied JJ E34L's and found that the B+, because of the Marstran PT----supposed to be @490V, was 525V----- I stopped and thought about it for a while and went ahead and converted the bias circuit to 6550/KT88 specs, including 150k bias splitter resistors-----I installed and biased a new quad of Valve Art KT88's----- amp was stable but plate volts are now 529V and screens are 525V--- preamp voltages measure in the normal range.
The clean tones on this amp are incredible !!! Huge, deep, and rich----I tried some different preamp tubes and settled on three RCA 12ax7a's for now. While building this one I decided not to start out with the mods described in my first post but instead to build the preamp near stock---- at least to start out.
By this time the rappers were done recording in the studio across the hall so I was able to crank this amp up without disturbing the recording time they'd paid for---- the studio engineer came over and witnessed the trial run of this amp.
I'm not totally in love with the cranked distorted tone at this point----- It does thicken up with the MV cranked enough to get the amp "working"------tried a few different OD and distortion pedals to boost it but nothing was really grabbing me about the overall distortion tone----but the recording engineer and another player who stopped by were quite impressed---- I think it was mostly because it is a very loud, powerful amp--- I know that a 2203 with unusually high B+, running KT88's should be an extremely powerful unit, and it is !!!! But I'm not satisfied with the distortion tone yet. Preamp is near stock except there's no Bright cap and the 470k/470pF first treble peaker is replaced by a 68k resistor----- this is my standard near stock starting point in 2204 based builds.
I've been debating what direction to go towards in terms of tweaking this one out------ Using the KT88's seems to point to Slash-type mods but I want to keep the potential for clean tones------ and the background noise that the #34 Mod brings bugs me. Although a gate in the loop will help with that.
I'll install the Metro FX loop tonight and sub in more and different preamp tubes and think about what direction to go in with preamp changes----- the chassis is punched for another preamp tube-- .......................................gldtp99

PS-- It did feel good to test it out at volume and feel it in my bones in a way that less powerful amps just can't match---- this is turning out to be a fun project--

[neikeel]

Sounds really interesting.
If you use both triodes of the extra tube (if you use it ) then presumably you can retain the clean channel and be able to switch in the other channel as before?
Sounds like it will need a front end kick (although the lack of response to good pedals is a concern.........)

[gldtp99]

I haven't done any more work to this one----- But I have received some text messages from players that have heard about this amp from the studio engineer and the folk player who were there in the room when I tried it out----- and from some other players who heard this thing cranked up from other parts of the building---- they are all quite positive and I have players wanting to try it out as it is now.
I think what is going on is that I recently bought a 20 watt Jet City 1x12 combo and I've been playing it at home, low vol. This cheapo ($299.99 brand new, free shipping, on sale) has a lead channel that is similar to the Soldano SLO, channel switching, and a series FX loop----- I don't know if all of these amps sound as good as this particular one but this amp probably has the easiest to play, best sounding lead channel I've ever played in any amp---- at least at very low volume levels----- I think i'm expecting a near stock 2203, pedal boosted, to match the endless, smooth distortion tone/feel of this cheapo Jet City.
So my expectations are the problem here, not so much a problem with the new Metro kit build----- It sounds just like a 2203--- Everything on the build operates properly, no noise/hum issues----relatively low noise floor.
Everybody else is very positive about it-----So I believe what I should do is install the Metro FX loop (chassis is already drilled), finalize preamp tube selection, and let these other players test it out and see what they think.
This makes more sense at this time than going ahead and modding the crap out of this build, drilling holes for more pots/jacks, and probably making a mess out of a build that sounds just the way it's supposed to---- and the amp looks good the way it is: no added holes (except FX loop), pots, etc----- the Metro chassis/faceplates and head cab are very photogenic just the way it is now.
I have other transformer sets, chassis, head cabs, that would better support the highly modded platform----- including turret boards with enough room to build a circuit with additional gain stages, switching, diode clippers, or whatever else I'll need to add to get the tone that's in my head.
Sometimes it's good to know when to stop----- ..............................gldtp99

[demonufo]

Keep us posted, as I'm intrigued. Other than servicing a 2203KK I don't have any experience with KT88's, and I'm curious as to whether or not you can get the whole thing to your liking, as it's not a tube I currently have in my arsenal.

[gldtp99]

I bypassed the V2a cathode resistor (820 ohm) with a .47uF cap----- this added enough fullness and sustain, and some distortion when pushed, that I see no need to mod this amp any further----- The amp now feels great when playing and I'm very, very happy with it------ most of the clean tone is still available.
The amp now sounds very good pushed by my Keeley Tubescreamer, MXR ZW OD, and Rat------ but actually the cranked tone of the amp itself, even though less gainy, really sounds better than the pedals------ the pedals would work for some compressed, gainy lead passages for a different accent------ but now the amp sounds terrific by itself---- I didn't use any delay tonight but the amp has big, thick tone with very pleasing harmonic content.
I will try delay after I wire in the Metro FX loop tomorrow.
I ended up with a Blackburn Mullard in V1, an RCA 12ax7a in V2, and a JJ ECC83S in the PI------ I'll do further preamp tube selection after the FX loop is installed.
I had the .47uF cap that I installed and a .68uF both in hand and just went with the .47uF cap, i'm not sure why------ either one might have done the trick but I'm not changing it now.
To sum it up: I couldn't be happier with the tone and feel of this amp------ not too much saturated distortion but it has easy, forgiving sustain----- it sounds like a good Marshall----------- ..............................gldtp99

PS---- After the amp is complete I'll get a demo vid up for viewing

[demonufo]

I know people have been pushing the front endd of 2203/2204's for many generations now, but I've always felt this circuit in mostly stock form suffers with anything in front from a tonal view. I always preferred to make the amp work for me, rather than be lazy and crank up more gain.

[gldtp99]

I see your point------ this build has me re-thinking my approach for future builds----- the sustain available without being boosted by pedals or highly modding the preamp makes this one very satisfying to play-----and it still sounds like a Marshall.
I have an '81 JMP 2204 and a '78 JMP 2203 but these two amps don't have the natural sustain and note bloom that this Metro kit build does--- I always boosted them with pedals to get the sustain I look for. But I don't think I'll mod these amps
with the same V2a bypass cap just yet---I have my Marshall 4010, 1x12 combo that I recently rebuilt near stock with a turret board-----removing the orig PCB that I'd modded with the #34 Mod---- I kept the Lar/Mar PPIMV and the Metro FX loop---- maybe a .47 or .68uF cap will improve this one------we'll see.
I also have been planning a 35 watt lo budget 2204 build using 6L6GC output tubes------- maybe I'll start on this one next to see if I can re-create the feel/tone of the Metro 100 watt build at lower power levels................gldtp99

[gldtp99]

I finally installed and tested the FX loop---- everything works properly----- it's hard to get much bench time lately---- the last three times I went to my shop I've been unable to get any amp work done because other players have wanted to demo amps that I've already built or rebuilt----- this has led to sales so it's not all bad, but progress on this Metro kit and others amps I'd like to get to keeps getting pushed back.
Testing out the FX loop I used an analog (Maxon) delay in the loop and an MXR ZW OD pedal front ended----- with the MV above 2 it sounds fantastic----- at lower MV levels it was sounding a little on the brittle side----- I played the longest with the Vol on 6 and the MV on 2.5------this sounded very, very good and allowed a very wide range of tones---- Clean with guitar vol rolled off, crunch with guitar vol on 10, and AFD Mod type blistering drive with the OD pedal.
I liked the delay for single note passages and for some cleans----- for crunch type tones the amp sounds better with the pedals turned off-----very satisfying basic rock amp tone.
I'll do further testing with different pedals, preamp tubes, speaker cabs, and having different players try it out.
I've been testing it out through my bench test 4x12 cab---- a Marshall JCM 900 1960A loaded with WGS ET65's.
One of these days I'll be able to get enough time to mount the amp in the head cab, take pics, and make a demo vid-- ...........................gldtp99

[gldtp99]

I forgot to mention how much fun it is to play this high B+, KT88 equipped, 100 watt amp-----the headroom and note definition available at all levels of amp/pedal distortion makes playing it so easy-----Just by changing the pressure of the pick attack so many flavors of tone are available without flipping switches, dialing knobs, or tap dancing on pedals.
If I could figure out how to build 15 to 50 watt amps that had this level of clarity, tone, and playability I could quit my real job and just build guitar amps, and still earn a comfortable living.
But one thing------ this amp is LOUD------ even with the preamp Vol on 6 and the MV on 2.5------ I have a '78 JMP 2203 in factory purple---- I let a friend try it out with his full band because he was interested in buying it----his drummer threatened to quit the band during practice as he was trying it out, and the MV was turned up to "1"----- he was using a distortion pedal and had the preamp cranked.
I still have the '78 2203 and I put a Lar/Mar PPIMV into it several yrs ago----It does lessen the vol and make the amp more playable in some situations------ but it's not a perfect solution by any means-----it takes away headroom/note depth---- In other words it does a good job of making a 100 watt 2203 sound/feel like a 50 watt 2204 or smaller amp------ this isn't necessarily a bad thing but why have a 2203 if what you really need is a 15-50 watt amp.
So I won't be installing a Lar/Mar or other PPIMV in this Metro kit build. This Metro build sounds better than my '78 2203 anyway----- the '78 sounds good, stock iron, EL34's, and some of the earlier tone smoothing preamp mods---it sounds good but this Metro build with the V2a cathode bypass cap (.47uF) has more sustain and clarity---- the way the note "carries" is a wonderful thing without any preamp buzziness that many modded preamps have.
This has me thinking about how I set up the gain structure in other types of amp builds I do---- I have one particular '65 Fender Bandmaster that has been the "sad sister", tonally, of all the other BF Bandmasters I have----- I can't directly do the exact same changes as in the Metro 2203 build but I can add some more drive, to get the sustain/warmth of other BF Bandmaster I have, later in the preamp or PI ----- I've already spent many hrs trying to blueprint this Bandmaster (voltages, component values, tubes, etc) vs another '65 Bandmaster I have (this one "has it")----- the sad sister has been somewhat improved through all this but it still isn't the amp that the #1 '65 is--- We'll see what I can come up with.......................................when I get some free time...............gldtp99

[gldtp99]

I turned down the FX loop a tiny bit---- then I tried out many different preamp tubes----Mullards, RFTs, Tungsrams, RCAs, GEs, etc----- I ended up with true NOS Allied branded Japanese 12ax7's in V1 and V2---- I don't know if these are Matsushita, Toshiba, or Hitachi but they sound fantastic in this amp---- I tried many tubes in the PI and one JJ ECC83 that came with the kit sounded as good as anything else so it's staying in there---- ----you never know.
I mounted the chassis in the head cab and put on the back panel----- this project is completed and I'm very, very happy with the outcome----
This is one of the most satisfying amps I've ever played-------I tried both analog and digital delays in the loop, both sound great------ I found that I like my Keeley modded TS9 best of all for a front end boost but other pedals sound good, too.
For rock/crunch rhythms the amp still sounds best with the pedals turned off-----the delays work well for clean tones and single note leads.
An amp customer was there while I was doing all this tweaking and he was amazed by the natural sustain of the amp by itself---- this is too much amp for him and he bought another, much less expensive, amp I built a few days ago.
I'll work on getting pics and a vid of this project for any who are interested.............................gldtp99

[neikeel]

Yes - we want pics

[gldtp99]

The Metro Forum is Back !!!!

Here are pics of this build I did several months ago:

http://s46.photobucket.com/user/gldtp99 ... t=3&page=1

[Maschinenmann]

Beautiful build Mark!

[maxwedge572]

That's nice!
Got a question. Where do you get that skinny wire that you use and is it 600v rated?
I need some wire like that for some Hiwatt repairs.