Build a 1987/2204 or get a 1987x??

Marcus Johns

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@neikeel thanks mate, I do agree I’d rather build the 2 in 1 straight up, I guess if I need to do any troubleshooting I can always get some voltage profiles from here or Metroamp forum?

Just confirming, with the 2 in 1, in 2204 mode (pot pulled out) the inputs are 2204 low and 2204 high, and in 1987 mode (pot in) you get 1987 bright low and 1987 high? You also mentioned the master vol works well in 1987 mode as well? So no real need for a PPIMV? I’m also looking to put in the Metroamp zero loss effects loop, it’ll be easer to drill the two holes for this prior to starting the build (along with the holes for the two switches for NFB and bright cap).

I’m starting to get a parts list together, someone already mentioned the 2 x F&T 50/50uf filter cap cans that I already have will be ok to use. Only other questions are:
- Synergy royal mustards vs Sozo Next gen coupling caps?
- Sozo silver mica 1000v vs other silver micas?
- NOS CC resistors as per the Valvestorm Diagram vs all Carbon film resistors?

cheers
 
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Marcus Johns

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@neikeel , sorry just one more question - which VS turret board is best to use for the 2 in one, the 2204 board or the 1987 board (perf?)? Thanks
 

neikeel

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I’d get the 1987 perf board.
Put the bus wire links up on top of the board and stick to Marshall colour coded with the wires fed through the inner hole then outwards back around the turret like the 69 era amps. Trouble shooting will be immeasurably easier if you need to.
 

neikeel

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Oh and I would only use cc on the NFB and, possibly preamp plates and v2a cathode (practically as the NOS ccs that I have will Soan the turrets. The rest using xicon cf will be fine, with no for the B+ droppers (10k and 8k2).
 

Marcus Johns

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@neikeel awesome thanks mate. I’m planning on putting in a NFB switch to switch between 100/4 and 47/8, however I read the 100/4 NFB doesn’t work too well with the V2a cathode 0.68u cap, do you think it would be worthwhile putting the 0.68u cap on the 2nd pole on the NFB switch so it takes it out of the circuit when on 100/4?
 

neikeel

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@neikeel awesome thanks mate. I’m planning on putting in a NFB switch to switch between 100/4 and 47/8, however I read the 100/4 NFB doesn’t work too well with the V2a cathode 0.68u cap, do you think it would be worthwhile putting the 0.68u cap on the 2nd pole on the NFB switch so it takes it out of the circuit when on 100/4?

Like most things it is a matter of taste. I like the 47k/8ohm NFB and don't particularly like 100/4 so never felt the need to swap. If anything I would go higher most of the time in the 27k/8 or 27k/16. I guess see how you go.
 

Marcus Johns

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I hope nobody minds , but I marked up the SDMs 2204 drawing for a 2204/1987 bright 2 in 1 as per the 2203/bright 1959 2 in 1 diagram (really for my own info as I like to use a highlighter to mark what I’ve wired during a build), main changes I did are the grounding, 240V mains wiring, NFB and bright cap switch, what are your thoughts:

https://www.dropbox.com/s/dnbhp7dqgz1klt0/1987 or 2204 2in1 alt lead.pdf?dl=0
 

neikeel

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Not bad.
Things I do.
I ground the heater CT not at 5 but 1
I ground 2 and 3 at point 2
I take a wire under the board from bias bus straight to pin 1/8 ground and use a ground between both octals (like Laneys) and have the output jack on one lug and bias wire on the other
I also take the presence ground in the loom to the PI/screens bias lug
I don't use the PT lug but ground mains cans and HT to the HT can mounting lug
It works very well and avoids lots of extra holes (and can be applied to a vintage amp too).
 

Marcus Johns

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Thanks @neikeel, yes I have the heater CT going to 1, I have the HT CT going to 5. I’ll check out your options above as well!
 

neikeel

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I0R1sZv.jpg

Found this pic of a 2in1 in a 50w of mine.
 

Marcus Johns

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Ok, you’ve convinced me, parts are on the way - except transformers, might need to wait till next year, I can at least wire a majority of the chassis and put the choke and transformers in later when they become available again.

@neikeel another quick one - just confirming, when in 1987 mode, the master volume needs to all the way up on 10?

I’m also looking to get the Metro ZL effects loop, the instructions mention to remove the wire between the MV pot (left lug) and Treble pot (middle lug) on a 2204 but on a 1987 the wire between the board cap that goes to the PI and treble pot (middle lug) gets removed. I’m guessing since I have a MV pot on this 2 in 1, I need to remove the wire between the MV pot and treble pot as per the 2204 instructions. - does this sound right?

I also like schematics to work off, what are your thoughts on this:
https://www.dropbox.com/s/zorajas63ebj708/16112021104427-0001.pdf?dl=0

Does this sound right for tge 1987/2204 2 in 1?:
1987 mode:
ChI Lo: 1987 Bright Low Gain
ChI Hi: 1987 Bright High Gain
ChII Lo: not used

2204 Mode:
ChI Lo: not used
ChI Hi: 2204 High Gain
ChII Lo: 2204 Lo Gain

Cheers!
 
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neikeel

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The switching options are correct in your summary.
I see you have added NFB options.
The way you have drawn the switch for the 0.0022/0.022 first coupler is not quite right. Basically you have the switch to insert the 0.0022 cap in series with the 0.022 in plexi mode. The layout diagram on the Neil special will show you this. You are correct - for full 1987 mode you crank the MV to max. You will find that in most applications dialling it down a little is helpful.
 

Marcus Johns

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The switching options are correct in your summary.
I see you have added NFB options.
The way you have drawn the switch for the 0.0022/0.022 first coupler is not quite right. Basically you have the switch to insert the 0.0022 cap in series with the 0.022 in plexi mode. The layout diagram on the Neil special will show you this. You are correct - for full 1987 mode you crank the MV to max. You will find that in most applications dialling it down a little is helpful.

Thanks mate, also with the 2 in 1, in 2204 mode high input - the grid resistance is 34k (has the 2 x 68k hi and low input resistors in parallel) whereas the original two hole 2204 will only have the one 68k input grid resistor - thus a grid resistance of 68k. Do you recommend plugging in an empty plug into the low input jack when using the hi input to open/disconnect the low input jack grid resistor which will then give us a grid resistance of 34k? Would you notice any difference?
 

Marcus Johns

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Here is my final layout:
https://www.dropbox.com/s/lw9svl66tvucip2/1987 or 2204 2in1 Neil alt lead dress v4.pdf?dl=0

And schematic:
https://www.dropbox.com/s/4vh42e2bpdssuid/1987 or 2204 Schematic.pdf?dl=0

Main mods I’ve done:
- Grounding scheme
- Switchable bright cap via 1987 bright volume push-pull switch
- Switchable cathode switch (takes V2 0.68u Cathode cap out of circuit for 2204 mode
- Switchable NFB resistors for 1897 and 2204

This should give me a stock 1987 bright high/low channel and switchable to a stock 2204/JCM800 circuit. Can’t wait to start the build!

As for cabinets, does anyone know if the ValveStorm 50w chassis fits into the Sourmash 1987 cabinet?
 

Chris-in-LA

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Here is my final layout:
https://www.dropbox.com/s/lw9svl66tvucip2/1987 or 2204 2in1 Neil alt lead dress v4.pdf?dl=0

And schematic:
https://www.dropbox.com/s/4vh42e2bpdssuid/1987 or 2204 Schematic.pdf?dl=0

Main mods I’ve done:
- Grounding scheme
- Switchable bright cap via 1987 bright volume push-pull switch
- Switchable cathode switch (takes V2 0.68u Cathode cap out of circuit for 2204 mode
- Switchable NFB resistors for 1897 and 2204

This should give me a stock 1987 bright high/low channel and switchable to a stock 2204/JCM800 circuit. Can’t wait to start the build!

As for cabinets, does anyone know if the ValveStorm 50w chassis fits into the Sourmash 1987 cabinet?
Just tell Sourmash what you need. I think that the Valvestorm chassis is 1/4 too deep. I always tell Sourmash how deep I need the cabinet as well as the size of the opening that I want. I’ve bought 3 1987 style cabs from them.
 

Marcus Johns

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Sorry to resurrect this thread, but have been still sourcing parts. Just want to check if the MM choke (3hy APD-8058M) and Heyboer OT (Drake 794-139) from amp parts direct would be good choices for my 50w 1987/2204 build?

Still need to source a PT.

I’m using 2 x F&T dual 50uF and dual 33uF axial filter caps.
 

Gene Ballzz

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Sorry to resurrect this thread, but have been still sourcing parts. Just want to check if the MM choke (3hy APD-8058M) and Heyboer OT (Drake 794-139) from amp parts direct would be good choices for my 50w 1987/2204 build?

Still need to source a PT.

I’m using 2 x F&T dual 50uF and dual 33uF axial filter caps.

No need to apologize for this kind of resurrection! I missed it in the initial stages and besides that, you stated that it may be on hold while waiting for components. I personally think that resurrecting with still functional links and foundational discussions is far superior to starting a new thread with links back to this one! I'm eager to see this project, it's progress and completion!
Just Thankin'
Gene
 

Dblgun

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I have used both the 8025AH (784-139 Drake clone) and 8025H (Dagnall clone) and like them both. I lean towards the 8025AH and the color code is correct for those amps. I have no experience with the MM choke and avoid MM when possible because I don't think the extra cost is justified. I don't think the 8058M is available currently, at least through APD. Might be sacrilege but given the current parts supply I would consider the 8003M. It's a 3hy 200ma choke that has the same footprint.
 

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