NOS John Mayer Sig / Wonderland 100W

[dbharris]

Big thanks to Taylor for the chassis and posting the layout for this project. I also have a head cab and 2x12 cab coming from Taylor in a month or so. In the meantime, I am starting to put this amp together slowly. I am a really big John Mayer fan and wanted to try to get this amp as close as possible to the Two-Rock amps that were built for him.

I wanted to contribute something back to the community, so I am uploading my BOM here. I tried to add links to the parts the I ordered.

Wonderland BOM (version 1).xlsx

When I heard Classic Tone was going out of business I ordered a full set of Twin Reverb iron since that was the brand Two-Rock used back then. Depending how the voltages end up, I may drop some voltage with a zener as I understand the iron in the Two-Rock amps were Twin Reverb but with 10% lower voltage secondary.

Jelle was kind enough to sell me a set of NOS draloric resistors. I also scored some NOS Philips BC caps from Ebay for the cathode bypass (in the appropriate spots) and presence cap. I collected a set of NOS Sprague orange drops as well, a mix of 6PS polyster and difilm. May end up switching out the difilm for new production 6PS depending on how it sounds.

Using new production for the rest of the amp. I think I have all of the parts now other than the power tubes. I had ordered a matched quad from AES but they only sent a matched pair...sorting that out now.

This is my first build from scratch and first fixed bias amp. So far I have added all of the hardware and cut some vinyl for the graphics. The only issue I have run into is that the fuse holder is too snug for the hole in the chassis. I guess I am going to open it up a little with a stepped bit tomorrow. Then I'll start wiring next.

If anyone sees anything wrong or that could be done better throughout the build, please feel free to point it out. All constructive criticism is much appreciated!

-Dan

[jwhousley]

AWESOME!

[Colossal]

Very nice! I just got my chassis for this project as well. I will enjoy following your build. Nice work on the BOM.

[ChopSauce]

Great! That's something of a project...

On a side note: I like using "counter nuts" so my switches (jacks, etc) don't protrude (much) from the faceplate.

[norburybrook]

I should play mine more often

Great build .


M

[Colossal]

I wanted to contribute something back to the community, so I am uploading my BOM here. I tried to add links to the parts the I ordered. Wonderland BOM (version 1).xlsx

-Dan

Dan,

I noticed you specified a number of pF value ceramic caps in your BOM. There are three used for the amp: 220p (bright cap), 330p (mid boost cap), and 470p (R||C on V1b). Did you just want a variety for tuning the amp to your taste?

[dbharris]

Thanks for the feedback so far!

I wanted to contribute something back to the community, so I am uploading my BOM here. I tried to add links to the parts the I ordered. Wonderland BOM (version 1).xlsx

-Dan

Dan,

I noticed you specified a number of pF value ceramic caps in your BOM. There are three used for the amp: 220p (bright cap), 330p (mid boost cap), and 470p (R||C on V1b). Did you just want a variety for tuning the amp to your taste?

I should have mentioned my BOM is not exactly in line with the layout, but should be 99% there. On the pf caps, I did order extra values to try. Back in November I think, Ryan (Tone Geek) posted his updated layout in the thread with Taylor selling chassis. It had the values for the precision resistors the Two-Rock used, but I noticed he had also changed some cap values too. There were some resistors that were the same value, but a metal film instead of carbon film, etc. I am not sure where that info came from.

As far as I am aware the 25 limited run of amps all have a blue signature by JM. This is the type of amp that Taylor met and based his layout on. There are other "JM Sig" amps that have a white signature and red signature too that I know of. These were built at different times as far as I know. The good picture of the "prototype" amp that has been posted on this site is dated 2009 in the chassis, which would be a couple years after the 25 limited run amps were released. John has said (a few years ago) he originally signed extra chassis in case they were damaged in shipping and Two Rock built new amps in them b/c demand was so high and sold them to the public as "prototypes." I imagine they may have used different parts in some places for what they had on hand, etc. I believe John may have also had his personal amps tweaked or updated from time to time and it is very likely the run of 25 amps is close, but not exactly what is in John's amps (circuit and parts selection). That is just his style and track record.

[norburybrook]

I still think the 1m/68k voltage divider is wrong it cuts way to much gain IMHO.

I've replaced it with a pot on the back to dial the gain in to taste.


M

[dbharris]

Marcus, curious if when you have that voltage divider set for more gain if the amp will start to break up? My only thought on this is that the original amps reportedly will not break up even with the gain and volume maxed.

-Dan

[dbharris]

Got the fuse holder hole opened up a bit and installed it. Also spent some time this weekend organizing parts to make the workflow for the build easier. Sorted all the resistors and caps, while watching some Anderton's demo videos on the tv.

IMAG2116.jpg

I have a couple questions. First, I realized that when I ordered the 1 Ohm resistors I selected al 1/4 watt, when 1 should have been 2-3 watt for the bias board. Can I used a 47 Ohm resistor there? That is the lowest value I have on hand in the right wattage range.

Second, I had ordered 2x 220uf F&T caps rated for 300V and 2x200uf Nichicon caps rated for 350V. The F&T are axial and Nichicon radial. Is there any issue with using the F&T? It seems like the radial would be a bit awkward to use on the power supply board.

IMAG2121.jpg

In the next post, I'll attach pictures of the resistors and caps I'll be using. I have some duplicates here or alternate values (as noted the BOM has some duplicate alternate values/types, etc.). My plan is to go with all of the Dralorics first and then when I am tweaking I may experiment with some metal films in a few places.

-Dan

[dbharris]

Pics:

[norburybrook]

Marcus, curious if when you have that voltage divider set for more gain if the amp will start to break up? My only thought on this is that the original amps reportedly will not break up even with the gain and volume maxed.

-Dan

The amp always seemed to be too quiet for a 100w amp with the 68k/1M unless the master was @100% which seemed pointless to me, why have a master volume if it needs to be set so high. Obviously the amp is designed to be clean and it certainly is but IMHO it can take some more gain from that voltage divider and still be clean. I don't think amps like this are designed to be run at full volume on the master and gain. If you look at John Mayer's settings at gig volume they're not extreme at all and he plays at a fair volume live.

I tend to run single coils and turning up the voltage divider and turning off the NFB with the dirt switches adds a nice bit of hair to a note if you want it.

I'll try record a demo if I get chance.

My amp is running 500+ VDC on the plates and I've got higher pre amp voltage too as I'm using different dropping resistors so it's not exactly the same as the layout/schematic from that point of view but more like the SSS it was modelled on.


M

[dbharris]

Marcus, thanks for the info. Would love to hear any of your recordings with the amp too.

Colossal, in my BOM I realized today that I was short 1 220K carbon film if you are going to use all cf (6 total), otherwise you need 4 cf and 2 RN60D.

I decided to use an extra RN60D for the 220K grid leak after the reverb tank. I may have a generic 1/2 watt 220K cf in my parts drawer that I could sub in if anyone thinks that would sound better.

Made a little progress today and hoping to be able to spend some more time tomorrow.

-Dan

[dbharris]

A little more slow progress...trying to triple check everything as I go. Next I'll be on to the power tube sockets, etc. before populating boards and adding the OT and PT.

-Dan

[amplifiednation]

Looking good!