Bluesmaster build

[dorrisant]

Very nice. Very timely too... I am planning a BM build. This stokes the fire!

[erwin_ve]

Sounds great!

I tweaked my Bluesmaster around my Strats - it took some time, but sounds incredible

Niki

Hi Niki, thanks! May I ask in what direction your mods ended up?
I've done some tweaking today: changed the v2a to 0.002 and Od entrance cap to 470pF. That was very nice for humbuckers and felt very similar to a skyliner OD. I reverted back to 0.001 and 47pF. to keep more mid scoop which felt more strat friendly.
OD tonestack is set to B: 70k , M: 4k7 and T; around 45%.

Some people wire the footswitch so that the PAB is activated with the OD to take the 1st tone stack out of the chain leaving just the OD tone stack. I've never done that so i teak the OD tone stack with the normal tone stack in line.

It's still a balancing act though if you play single coil guitars and humbuckerer guitars

Sounding great though. I'm sure you'll get it where you want it.

Thanks Marcus, I set the OD trimmers with PAB on. One small observation: In my last builds the Pab board resistors are 22M carbon comp resistors. They seem to give more low end on the PAB. I dont know why, it just happens.
Without the PAB the OD has the same kind of character so both are in the same ballpark.
Nevertheless balancing between bucker and single coil it is!

[norburybrook]

Sounds great!

I tweaked my Bluesmaster around my Strats - it took some time, but sounds incredible

Niki

Hi Niki, thanks! May I ask in what direction your mods ended up?
I've done some tweaking today: changed the v2a to 0.002 and Od entrance cap to 470pF. That was very nice for humbuckers and felt very similar to a skyliner OD. I reverted back to 0.001 and 47pF. to keep more mid scoop which felt more strat friendly.
OD tonestack is set to B: 70k , M: 4k7 and T; around 45%.

Some people wire the footswitch so that the PAB is activated with the OD to take the 1st tone stack out of the chain leaving just the OD tone stack. I've never done that so i teak the OD tone stack with the normal tone stack in line.

It's still a balancing act though if you play single coil guitars and humbuckerer guitars

Sounding great though. I'm sure you'll get it where you want it.

Thanks Marcus, I set the OD trimmers with PAB on. One small observation: In my last builds the Pab board resistors are 22M carbon comp resistors. They seem to give more low end on the PAB. I dont know why, it just happens.
Without the PAB the OD has the same kind of character so both are in the same ballpark.
Nevertheless balancing between bucker and single coil it is!

Interesting about the 22m resistors. I often find the PAB too thin with Single coils so that might be a way round that.

What pot did you use for the Bass on the OD trimmers? I use a 250 in there now as I found the 1M was on /off at far end of the range, so 90% wasted.


M

[erwin_ve]

Marcus I also used a 250k on the bass trimpot.
I wonder if the Bluesmaster originally has a tone stack from the cathode follower instead of the plate. That would explain the Marshall values in that spot.

[norburybrook]

Marcus I also used a 250k on the bass trimpot.
I wonder if the Bluesmaster originally has a tone stack from the cathode follower instead of the plate. That would explain the Marshall values in that spot.

that's a good point Erwin, my limited technical knowledge has meant I've never questioned or understood this, but that's a good train of thought.


Having said all that though, isn't the bluesmaster one of the amps that was fully documented/cloned from an original amp? basically nothing's being guessed at on the schematic/layout.


M

[rootz]

Marcus I also used a 250k on the bass trimpot.
I wonder if the Bluesmaster originally has a tone stack from the cathode follower instead of the plate. That would explain the Marshall values in that spot.

Erwin, maybe the 1meg bass pot seems too large in a Bluesmaster because there is more bass preserved throughout the preamp in a Dumble when compared to a 1959 model Marshall? FWIW I never have the bass knob on my jtm45 above 1 when pushing the output section (thus when it goed into overdrive). There is just too much bass in the circuit to work with overdrive, despite treble peaking caps.

Furthermore, the bass pot in a Marshall is typically audio taper, not linear like in the HRM stack. This makes a huge difference too.

By the way, amps like the Peavey JSX have a plate driven tone stack in the overdrive section also, A1meg and otherwise pretty typical Marshall values.

250k for the bass pot in HRM simply works. I used the same value and found the bass trimmer much more useful.

[talbany]

Pab board resistors are 22M carbon comp resistors. They seem to give more low end on the PAB. I dont know why, it just happens.

Perhaps we can get some of those engineer types out there?. You know the ones that have to see it in the modeling software or the curve traces and yes even spec sheets to explain this one Good luck with that.
Erwin when I first heard that the type of resistor used on the PAB board mattered I laughed,until I tried it then I cried. Same thing with the resistor types on the NFB on V1a. What you gotta be kidding me?? I cried again. We can go on. GNFB resistor type. It just gets worse and worse until you just give up..
Amp sounds great!!

Congrats!

Tony

[Synchu]

Erwin,

Here’s the list of my tweaks ( I think this should be the latest ):
Bass and Mid caps to 0.07uf (i.e. added 0.05uf in parallel)
- OD entrance resistor to 33K
- Treble cap set to 390pf ceramic. It is interesting that Silver Mica of the same value (measured within 3-4 pF difference) didn't work that well for the overdrive. Cleans were better.
- NFB changed to 4K7 & 390R
- HRM OD set as per my preferences - Treble at around 90k, Bass@70K, Mid around 7K
- OD trimmer is 20.9K to ground
Niki

[erwin_ve]

Pab board resistors are 22M carbon comp resistors. They seem to give more low end on the PAB. I dont know why, it just happens.

Perhaps we can get some of those engineer types out there?. You know the ones that have to see it in the modeling software or the curve traces and yes even spec sheets to explain this one Good luck with that.
Erwin when I first heard that the type of resistor used on the PAB board mattered I laughed,until I tried it then I cried. Same thing with the resistor types on the NFB on V1a. What you gotta be kidding me?? I cried again. We can go on. GNFB resistor type. It just gets worse and worse until you just give up..
Amp sounds great!!

Congrats!

Tony

Thanks Tony! True science is investigating why these things happen and not argueing why they shouldnt happen, dig deep . I lean more towards enjoying the benefits of certain components these days

Erwin

[erwin_ve]

Erwin,

Here’s the list of my tweaks ( I think this should be the latest ):
Bass and Mid caps to 0.07uf (i.e. added 0.05uf in parallel)
- OD entrance resistor to 33K
- Treble cap set to 390pf ceramic. It is interesting that Silver Mica of the same value (measured within 3-4 pF difference) didn't work that well for the overdrive. Cleans were better.
- NFB changed to 4K7 & 390R
- HRM OD set as per my preferences - Treble at around 90k, Bass@70K, Mid around 7K
- OD trimmer is 20.9K to ground
Niki

Thanks Niki for sharing your tweaks!
Did you try changing to slope resistor?
OD entrance resistor: do you mean the 1st one? original 470k?
On the treble cap; yes my observation as well!
NFB is more like the Non HRM version: your amp has more headroom?

Erwin

[Synchu]

Erwin,

What I do remember is that I played a lot (and I do mean a LOT) with the slope - both in LTSpice and "live", but I can't find that I changed it in my notes - so I probably left it alone
That is the OD stage entrance 120K resistor that has been changed to 33K - this was a tip from Carol-Anns very own Alan Phillips and it worked extremely well.

The story of this Bluesmaster (it is of HRM variety ) is quite a bit longer - it started as a Ceriatone BM HRM, built by another amp builder, also a forum member (thanks Mirc) with some excellent custom transformers. I purchased it from him and it ignited my passion to Dumble tone and amp building as a whole. I tweaked it to death (after I built some amps already) before it ended as described above.

Again - while it generally sounds very good, it has been tweaked around my strats and it sounds best with a strat.

Niki

[erwin_ve]

Erwin,

What I do remember is that I played a lot (and I do mean a LOT) with the slope - both in LTSpice and "live", but I can't find that I changed it in my notes - so I probably left it alone
That is the OD stage entrance 120K resistor that has been changed to 33K - this was a tip from Carol-Anns very own Alan Phillips and it worked extremely well.

The story of this Bluesmaster (it is of HRM variety ) is quite a bit longer - it started as a Ceriatone BM HRM, built by another amp builder, also a forum member (thanks Mirc) with some excellent custom transformers. I purchased it from him and it ignited my passion to Dumble tone and amp building as a whole. I tweaked it to death (after I built some amps already) before it ended as described above.

Again - while it generally sounds very good, it has been tweaked around my strats and it sounds best with a strat.

Niki

Thanks Niki!

[fred.violleau]

Sounds Great Erwin, and it looks fantastic as well!

I am hunting for NOS here as wel for my next build, got some Pihers and Roderstein, the usual suspects from Jelle as well, but I can't find the ceramic cap Tony is refering to in the treble cap position. What bypass caps did you use ? NOS too ?

I think it is a tough balance to switch from single coils to humbuckers, OK for a strat will be too bassy and missing brightness for humbuckers in my case... Add the Overdrive compromise in the mix and it's not easy to get by all the combinations. I usually tend to have an amp set for one or the other, but I am curious to hear how others deal with this issue ?

Looking forward to see this amp fully dressed

Cheers,

Fred.

[erwin_ve]

Sounds Great Erwin, and it looks fantastic as well!

...but I can't find the ceramic cap Tony is refering to in the treble cap position. What bypass caps did you use ? NOS too ?

Thanks Fred!
I cant find the old Sprague x5f ceramic either. I used the most expensive Vishay/Ceramite X5F available at mouser. On spec sheet they are the same as the cheap ones but construction and finish IRL is different between the cheap/expensive ones.

Erwin

[talbany]

Pab board resistors are 22M carbon comp resistors. They seem to give more low end on the PAB. I dont know why, it just happens.

Perhaps we can get some of those engineer types out there?. You know the ones that have to see it in the modeling software or the curve traces and yes even spec sheets to explain this one Good luck with that.
Erwin when I first heard that the type of resistor used on the PAB board mattered I laughed,until I tried it then I cried. Same thing with the resistor types on the NFB on V1a. What you gotta be kidding me?? I cried again. We can go on. GNFB resistor type. It just gets worse and worse until you just give up..
Amp sounds great!!

Congrats!

Tony

Thanks Tony! True science is investigating why these things happen and not argueing why they shouldnt happen, dig deep . I lean more towards enjoying the benefits of certain components these days

Erwin

Exactly! Couldn't have said it better myself. I don't know why either I just hear it. So Yes the older Sprague XF5's are a bitch to find in those values and very much have a sound of their own,especially in OD mode. The newer (smaller ones) do sound a bit different to me but is not a bad sounding cap. I've used these in my B.M amps with some sucess but not quite as clear and open round mids as the old ones.
BTW. A big part of my struggle to try and capture the "Dumble sound" was discovering the old XF5's and IMO is every bit as important as the 6 PS series caps used in the rest of the amp The XF5's IMO are sort of in between a typical ceramic type cap like Fender used and a Silver Mica. Clear articulate with open mids but without the harsh top end of your typical CDE (and most other)Silver Mica.

Welcome to the next level

Tony