Metropoulos Forum

I've been toying with the idea of building a 10000 series, for quite some time, lots of things happened in between (a 6G16 Vibroverb build, for one), and in the last couple of months I started accumulating the parts.
Basically a late '67 SB with the JTM preamp (single dropping resistor, 470K mixer resistors), low screen filtering, 27K/16Ohm NFB and Drake style iron.

Finally last week, thanks to COVID isolation (and to Heyboer delivering the PT) I had the chance to finish the build.
So, here she is in all her glory:

https://flic.kr/s/aHBqjzzLhv

I used the following:
Metro amp 67-68 steel chassis
Heyboer 1202-132 Metro spec OT
Heyboer 1203-80ML Metro spec PT
ClassicTone 3Hy choke
22/16/50/32 filtering (F&Ts and RIFAs)
SOZO coupling caps
Valvestorm blank perf preamp and power boards with Silver coated Turrets from AliExpress (had to cheap out on something)
Valvestorm front JMP logo panel
Modulus amps Superbass rear panel
Alpha pots - I ditched the Linears for Log (Audio) pots
garden variety 1 Watt Carbon Film resistors, some 1/2 and 1 watt Carbon Comps of different makes (ABs, Xicons...)
Castelco bat switches
Clynder (UK) wire

I deviated from the original spec (if there ever was one) by implementing the Larry grounding scheme, a Lar/Mar PPIMV and a 270pf cap in the tone stack.
In addition, I chose to replace the Linear pots with Logarithmic pots based on George's account of checking old Marshall pots, I have no idea whether the ratios match.
I haven't yet settled on a final V1 cathode cap - I tried 5uf, 220uf and currently using a 10uf BC cap, contemplating trying a 25uf.
Also considering increasing the PI filter cap.

I love the sound - it's organic and very much a cross between the fluidity and bluesy raunch of the JTM45 with the authority and punch of a '68 Superlead - a happy medium I was opting for, having built both the JTM45 and the '68 SL and always wishing for something to bridge the gap between both tonal characteristics.

Would love to hear any input (no pun intended), especially regarding the Linear vs. Log thing and cathode cap value.

You shouldn't hear any difference between Lin & Log pots (note: Presence pot is always linear). You'll just have different dial setting between the two pot versions to acquire the same tone.

As for V1 cathode bypass cap; any large value, say over 10uF, will basically produce the same results.

Tazin wrote: ↑

Wed Jan 26, 2022 11:37 am

You shouldn't hear any difference between Lin & Log pots (note: Presence pot is always linear). You'll just have different dial setting between the two pot versions to acquire the same tone.

As for V1 cathode bypass cap; any large value, say over 10uF, will basically produce the same results.

You're right - I used a Linear 5K pot for the Presence control, the Treble and Mid controls are Audio.

I'm currently using 10uf, gonna try 2.2uf and 1uf, just looking to strike the perfect balance as 220uf sounds nice and tweedy but too much flab at low volume and on the other end, .68uf is a bit too lean on lows for my taste (though sounds great for certain things).

I set up my previous Superlead for maximum versatility with a 1.5k/4.7uf Normal channel, 820/.68uf Bright channel, .0022 v1B coupling cap, switchable Lead/Bass tone stack with a 330uf fat cap on the Lead side and .022 PI couplers.
I wanted this amp to be less of a tinkerer's dream and more of a straight out epitome of the classic Plexi tone but it seems some experimenting is needed to relieve the tone chasing urge.

Dude it looks fabulous. Any slips or videos on YouTube?

Looks very nice and tidy

Good job, I like your work!

axeman wrote: ↑

Thu Mar 03, 2022 10:55 pm

Dude it looks fabulous. Any slips or videos on YouTube?

Thanks, challenge accepted.
Excuse my sloppy playing, here are three recordings of the amp through a mid-nineties 1960AX cab which I moded with S&P grill cloth, full 60s bracing, a plywood back and metal handles.
Amp settings are Presence 5, Bass 0, Mid 8, Treble 6, Vol. 2 on zero and PPIMV at about 9 o'clock.

1. Early 60s style DIY Strat, E906 mic on grill straight to my Firestudio Mobile and into Garage Band with no fx or eq except for 75% panning of each track to the left and right channels and a fade out.
The left channel is guitar straight to upper left input, vol. 1 on 8.
The lead sound on the right channel is the same settings but pushed with a Catalinbread Epoch booster.
https://soundcloud.com/user-129489329/e ... al_sharing

2. Historic R8 LP straight into amp, vol. 1 on 10.
The verses are the neck pickup with volume on 3 and the choruses are the bridge pup on 10.
https://soundcloud.com/user-129489329/e ... al_sharing

3. iPhone recording of my 335 through a Catalinbread Belle Epoch Deluxe into the lower left input with vol. 1 on 6.
https://soundcloud.com/user-129489329/n ... al_sharing

I'll try to record some VH style clips with a Superstrat and pedals (the amp can't get there alone) later this week.

One more sample extracted from noodling recordings (this was my first time using the E906 - its a 57 killer but I think I still need a room mic as well).

Its the same Strat from the Hendrixesque track but I don't remember the amp settings, way too much drive though - I believe this was with the volume on 10. I'll record clean-clean tones when I get to it.

https://soundcloud.com/user-129489329/e ... al_sharing

Sounds good to me!

danman wrote: ↑

Mon Jun 27, 2022 5:59 pm

Sounds good to me!

Thanks mate!

Trying to do my best within the time and playing abilities constraints
I'm pretty happy that the low end heft, the compression and the punch/bark of the amp in the room comes in the recordings through most speakers/headphones I tried. Those are the main attributes setting the early EL34 amps' tonal character apart from that of the later ('68-'70) 100 watt amps with Dagnall iron, in my ears at least, and is what I opted to achieve when I set out to build this amp.

I hear it's a marshally Amp. Good sound!

I didn't have the time to come up with something nice so I just noodled and slammed some stuff together to demonstrate a Van Halen 1-ish tone out of the amp.
Amp set up as previous tracks with vol. 1, treble and mid on 10.
The guitar is a DIY Superstrat with a northern ash body, AllParts maple neck, 6-screw gotoh bridge and a single ceramic Dimarzio Dual Sound humbucker. Strings are Daddario Pure Nickel .009-.041 tuned to D#.
Signal chain is the guitar into the Catalinbread Epoch Boost and Belle Epoch Deluxe for some delay.
I'm really impressed with the E906 so far.

https://soundcloud.com/user-129489329/e ... al_sharing