A couple of Marshall clones

Discussion in 'DIY Amp Forum' started by ivan H, May 31, 2019.

  1. ivan H

    ivan H Strat-Talker

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    I thought I'd show a couple of my amp builds here. The first is a '68 spec 50 watter. Transformers are Marstran Heyboer items. Most of the electronic components are period correct NOS items, Iskra resistors & Philips Mullard mustard capacitors WP_20181222_13_44_54_Smart.jpg
    Filter capacitors are F&T. The 0.68uf bypass caps are Philips Bianchi & 560pf the treble & treble peaking silver mica caps are RBS. I do have period correct RS silver mica caps to replace the treble & treble peaking caps with. The volume 2 bright cap is a 4700pf Lemco ceramic disk. WP_20181225_08_21_14_Smart.jpg
    Tube compliment is as follows
    V1, 163 series Mullard.
    V2, Brimar CV4004.
    V3, 163 series Mullard.
    V4 & V5 in this pic are winged C EL34's.
    V6, Mullard f32 GZ34.
    I do have NOS/NIB xf2 Mullard single halo EL34's (factory matched branded GE) that I use for special occasions IMG_20190124_094533.jpg
    IMG_20190108_073614.jpg
    With these in & biased to 60% the amp sounds, well, phenomenal. Here's a pic of the front panel WP_20181225_08_23_03_Smart.jpg
    The CTS pots have all been opened up & had their resistance values "doctored" to my personally preferred values.
    Volumes, 1.3 Meg.
    Treble, 325k.
    Middle, 29k.
    Bass, 1.1 Meg.
    Presence is stock 5k.
    Being a '68 spec the V1a cathode combination is 820r/0.68uf. This is a good bit gainier than the common 2k7/0.68uf combination & doesn't clean up so well with the guitar volume. The power transformer is the higher voltage unit of the era that puts nearly 460V on the EL34 plates. This amp through a G12M greenback loaded 4X12 cab is my main gigging amp. Sorry I don't have a pic of it in the headcab on my phone. I'll show my '69 spec 100 watt superlead in the next post. Cheers
     
    Last edited: May 31, 2019
  2. ivan H

    ivan H Strat-Talker

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    Ok, the '69 spec 100 watt superlead is built around Merren Audio power & output transformers. The 3 henry filter choke is a Classic Tone item. WP_20130306_14_36_42_Smart.jpg The board in this (& also the previously shown 50 watter) were turreted up by me. All electronic components in this WP_20130306_14_35_12_Smart.jpg are period correct NOS items, Iskra & Piher resistors, Philips Mullards mustard & RS dogbone capacitors. WP_20130306_14_40_03_Smart.jpg
    WP_20130306_14_28_25_Smart.jpg
    Tube compliment is
    V1, 163 series Mullard.
    V2, Brimar CV4004.
    V3, 163 series Mullards.
    V4,5,6 & 7 are Svetlana EL34's but I do have a NOS quad of xf2 Mullards EL34's coming.
    Filter capacitors are all ARS 50uf/50uf/500V dual cans that I conditioned/formed by current limiting via a 100k resistor (down to a 4 volt drop across the resistor. The bright cap on volume 2 is a 5000pf RS dogbone. The pots have all been opened & had their resistance values doctored, same as the 50 Watter. The power transformer has dual secondary high voltage taps. The standby switch is a 3 pole double throw (center off) item that switches between the two voltages. The "third" pole of the switch is for the AC bias feed & has a resistor attached that is used to keep the power tubes properly biased in both HT modes. HT voltages are 506V & 466V. I usually use 466V because the higher 506V is a bit hard on the power tube screen grids. WP_20130306_14_47_12_Smart.jpg
    I've been using this through a friend's creamback loaded cab as I don't want to risk blowing the greenbacks in my cab, but I've just ordered a greenback loaded 1960B cab to go with my "A" cab. Whereas the 50 Watter has a very overdriven tone that can compress quite well, this has a big, tighter, powerful & aggressive crunch tone. It is blisteringly loud. Cheers
     

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    Last edited: May 31, 2019
  3. Stratoskater

    Stratoskater Fuzz Meister General

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    Very nice work!
     
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  4. bluejazzoid

    bluejazzoid Strats Amore Silver Member

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    Man, that's some beautiful stuff there - works of art! No doubt they sound KILLER... thanks for sharing!
     
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  5. RJ Squirrel

    RJ Squirrel Senior Stratmaster

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    Very tidy wiring.:thumb:
     
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  6. mabley123

    mabley123 Senior Stratmaster

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    Great work, and accuracy.

    If I could build amps, Id build a 1966 replica JTM45/100:). If I get the money I will 1 day have Valvestorm build one/Metro spec, for me.

    Ive got a 2013 LTD ED Metropoulos GMP45 head, which is a 65 replica Drake spec transformers from Heyboer, with NOS Mustards, KT66s but has PEC pots. Its a killer amp. Possibly the best amp Ive ever heard, or as good as any anyway.

    Running it through 4 x 1972 Pulsonic G12H/25w/75Hz speakers with a Mather Replica 1966 JTM45/100 TVB cab, with EC Collins Pinstripe cloth. Its the closest Ill ever get to the real thing.
    NOS 1956 Marconi Osram KT66s, V1 NOS Mullard 10M Gold Pin, V2 NOS Mullard 10M GP, V3 NOS 57 mC1 Mullard LP, NOS Mullard 61 Fatbase GZ34.
    [​IMG][​IMG][​IMG][​IMG][​IMG][​IMG][​IMG][​IMG]
     
  7. ivan H

    ivan H Strat-Talker

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    Thanks for the kind words guys. The 50 watter was built quite a few years ago, as can be seen by the transformer bell ends etc. It was rebuilt with the NOS components, retubed & recapped about 6 months ago. The board was stripped & re-turreted at the time. It has carbon comp HT voltage droppers/decouplers as I feel they contribute something to the feel of the amp. The NOS 163 series Mullard 12AX7's in both amps are rebranded RTC. They were chosen for their tested mA & gm readings. Both PI (V3) tubes are quite hot, especially the one in the 50 Watter, mA1.2/1.3, gm2000/2000, which would somewhat explain its heavily overdriven tone. Phase inverter plate differential voltage in the 50 watter is a little above the ideal 7.2V & in the 100 Watter it's a little below it, but both are ballpark, within 0.5V. I may (one day) add a 5k trimmer to both so I can dial it in. I like the 163 series Mullard 12AX7's as they have a great hard rock sound. The NOS box plate Brimar CV4004's are 1% matched triodes with mA1.3/1.3. gm is around 1800/1800. Great sounding cathode follower tubes. The GZ34 was NOS/NIB rebranded Valvo & has a Blackburn '71 date code. It's a 7 notch plates type. All the Mullard tubes have Blackburn codes, including the EL34's which are also '71.

    Mabley123, that is a beautiful amp/cab right there, I can imagine it sounds glorious. Some really nice British valves you are using too. Were the KT66's hard to source? A buddy has a NOS/NIB factory matched GEC duet that he isn't using & just will not sell to me (damn it, damn it, damn it). George Metropolis is a renowned builder/tuner & also a decent guy. I have a few of his products (no amps though). Pity about the loss of info on his forum, it was a great resource.
    I also use Valvestorm, mostly for hardware, chassis, headcabs etc, but also some components. Robert is great to deal with.
    I have a full set of NOS silver Mica caps (slated for an upcoming NOS black flag/reverse logo amp build) that would be great in your amp. IMG_20190601_081500.jpg If I come across another I'll give you a yell. A JTM45/100 would be a great amp. Very hard on the KT66 screen grids though.
    I have enough NOS components in my stash to do a full NOS component Back Flag/Reverse Logo build & also to rebuild my footswitchable 2204/Tim Caswell #39 mod amp with NOS components. That will probably be all I will do, it's getting too hard to source the NOS components, not to mention there are fakes getting around. You need to know what to look for, I imagine people are unknowingly getting stung.
    Well, I'm off to rehearsal & to let the superlead loose.
    Cheers
     
    Last edited: May 31, 2019
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  8. mabley123

    mabley123 Senior Stratmaster

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  9. mabley123

    mabley123 Senior Stratmaster

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    I run my amps at 110v-112v too. I use a Furman P1800 AR, and a BrownBox to reduce the volts. Makes it run 20-30 degrees cooler. Alot more anyway. Much easier on tubes also. I cooked NOS KT66s over time as my wall voltage is often 129v.
     
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  10. Mr. Lumbergh

    Mr. Lumbergh needs you to go ahead and come in on Sunday, too.

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    Very nice. I'm impressed by the workmanship and attention to detail in those photos.
    Are you going to post some audio samples?
     
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  11. mabley123

    mabley123 Senior Stratmaster

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    Ive got no way to record
     
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  12. Sarnodude

    Sarnodude Most Honored Senior Member

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    Absolutely beautiful component layout and lead dress. Wow....
     
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