50 Watt Bass (1986 circuit) Rocks!

[Harold]

I added the 250pF to my order to be able to try them all. Let's start with the stock 1986 Bass spec and work our way up to the 33K/500pF spec.

That is a rock solid plan

I'm using the stock 1986 tone stack right now, and have everyting dialed up to 9-9.5 to get real punch out of the amp. According to the Duncan Tone Stack Calculator, the treble cap also adds quite some mids and the shelf resistor shifts the low-peak from 50-60Hz to about 80?

First I'll try the amp at high volume in our rehearsal space before I change anything in the tonestack ...

[Harold]

I added the 250pF to my order to be able to try them all. Let's start with the stock 1986 Bass spec and work our way up to the 33K/500pF spec.

That is a rock solid plan

I'm using the stock 1986 tone stack right now, and have everyting dialed up to 9-9.5 to get real punch out of the amp. According to the Duncan Tone Stack Calculator, the treble cap also adds quite some mids and the shelf resistor shifts the low-peak from 50-60Hz to about 80?

First I'll try the amp at high volume in our rehearsal space before I change anything in the tonestack ...

... I'm having a hard time getting used to the 56K/250pF tonestack. Bass and mids are set at 10 and treble around 7 to get enough punch out of the amp.

I guess converting it to 33K/500pF will add some mids and (audible) lows for me? I read somewhere that the low-peak of the 56K/250pF stack is around 40Hz when dimed?

[Danhalen]

Whoa bass on 10! On my amp that setting would be very boomy and if the amp was cranked into distortion sludgy too.

To my ears the lead tonestack sounds a bit more nasally and harsh. I am not crazy about it without going the full way to lead (.68 bypass caps). For some reason either full bass or full lead sounds best to me, with lead working well for focused high gain sounds. I couldn't say I noticed a difference in bass response between either tone stack. What you will get with lead spec if you go the whole way is cleaner tighter bass (ie less bass) when the amp is really cranked so it will be punchy and focused under high gain.

Edit: Oh wait I see you don't have the huge bypass cap on v1 which might be way you are able to get your bass control up to 10! If you want more bass maybe you like the sound of a larger bypass cap at v1? Although that won't give you what I would describe as punch at high gain.

[Coot Boy]

For some reason either full bass or full lead sounds best to me

I've been saying for years the same thing, especially the JTM45, to me they all sound best stock. That's why I have 8 amps. I spent years doing all the mods but realized one day that it was getting me further away from what I was looking for, of course, that's just me.

[Harold]

I received a NOS 400pF ceramic cap that I'll try as treble cap and I'm going to lower the slope resister to 47K or even 33K. I like the feeling of the amp, but it's far to mid-scooped for my taste, which -until recently- was all about JMP 2203 and 2204's

[Harold]

I received a NOS 400pF ceramic cap that I'll try as treble cap and I'm going to lower the slope resister to 47K or even 33K. I like the feeling of the amp, but it's far to mid-scooped for my taste, which -until recently- was all about JMP 2203 and 2204's

First impression of the 400pF/47K is impressive! Far more highs, mids and "open" than the 100% 1986 tone stack.

... and the mandatory gut shot:


Larger image: http://img.sait.nl/1987x/1987_mvs.jpg" onclick="window.open(this.href);return false;

[ramhi4x]

Does this circuit brown like a 1987?