DIY amp build: Done with the headshell ..now comes the tough part :p

[GoldenVulture]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Board with a rotary pot (C 50k), IC, input, ground, output & +12V DC connections

What's the IC and what's it do ?
I'm presuming that's where your gain is coming from. Most OP amps output level can be set by a couple of resistors. Depending on the values , sets the gain factor , from unity gain to what ever the chip is capable of.

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

The IC is pretty small and I can't tell if anything's written on it..it's square-ish with 4 pins coming out of either side that's all I can say about it

EDIT: OK, apparently my son's eyesight is a hell of a lot better than mine :laugh2:

Here's what he said he saw on the chip: 022BA04GJRC

 

[GoldenVulture]

Re: DIY amp build: Done with the headshell ..now comes the tough part

The IC is pretty small and I can't tell if anything's written on it..it's square-ish with 4 pins coming out of either side that's all I can say about it

EDIT: OK, apparently my son's eyesight is a hell of a lot better than mine :laugh2:

Here's what he said he saw on the chip: 022BA04GJRC

OK, that probably translates to JRC022 [equivalent NJM022] which is a dual op amp.- https://www.google.com/url?sa=t&rct... M022B_E.pdf&usg=AOvVaw268M_LRZBr2XPiY_DRm5_A -

I don't know if you can get your head around this.
- https://www.radio-electronics.com/info/circuits/opamp_basics/operational-amplifier-gain.php -
But if you can grasp the basic formula here , then use it to deduce what your boost circuit is doing you may be able to change the gain factor.
- https://www.youtube.com/watch?v=4M4H-aLvIoA -

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Well, Thanks Vulture.. I gave that a fair try but I have to admit most of it just went way over my head.. even though I looked up a whole lot of other stuff about op amps as well. I don't think I can even identify the type of circuit leave alone calculate the gain and use those formula's to pick appropriate resistor values. It's way beyond my capabilities :laugh2:

In purely practical/layman terms, how about if I use a trim pot (another 10k pot?) in series with the mid-boost board..just before the volume pot? That way I could match the gain level/volume after the signal passes through the board with the gain/volume of the signal before it hits the board (which is what I need to do). Would That affect the nice taper I have for the power amp's volume pot right now? Or should I use a couple of 5k pots (ie 1 trim pot & 1 rotary in series) instead of the 10k volume pot I have there right now. Would that work do you think?

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

I do have a plan B in hand as well. Another mid-boost board without an op amp. It does'nt boost the signal as much and the effect is a lot less dramatic/drastic.

While this one actually affects & changes mid frequencies (ie "Q" ..ideally what I'd like to have in there) the other board I have (without the chip) just boosts mid-mids and high mids that are already there as you sweep the wiper..sort of like a tubescreamer..

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

A little fun with the mid circuit

I recorded this with my digital handheld recorder and the same setup as the last clip.

There's definitely some clipping of the input signal going into the amp (it's way too high.. even with the preamp output & amp input levels turned way down). But if I can get things down to acceptable levels there's a fair bit of tonal variety available with every turn.. :bigthumb:





EDIT: And a short clip jamming Powerslave (wrong lol) using a mid-sweep setting - this one's a mic'd recording, but I had to turn the preamp's & overall volume super low..or it clips.

 

[GoldenVulture]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Well, Thanks Vulture.. I gave that a fair try but I have to admit most of it just went way over my head.. even though I looked up a whole lot of other stuff about op amps as well. I don't think I can even identify the type of circuit leave alone calculate the gain and use those formula's to pick appropriate resistor values. It's way beyond my capabilities :laugh2:

In purely practical/layman terms, how about if I use a trim pot (another 10k pot?) in series with the mid-boost board..just before the volume pot? That way I could match the gain level/volume after the signal passes through the board with the gain/volume of the signal before it hits the board (which is what I need to do). Would That affect the nice taper I have for the power amp's volume pot right now? Or should I use a couple of 5k pots (ie 1 trim pot & 1 rotary in series) instead of the 10k volume pot I have there right now. Would that work do you think?

This should do for now.
Have you got any of these ?

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

No, not that type exactly..I've got these (5k, 10k, 20k)

Are they the same thing?

Or I could get that exact type you posted in a couple of days, I've seen them around.

 

[GoldenVulture]

Re: DIY amp build: Done with the headshell ..now comes the tough part

No, not that type exactly..I've got these (5k, 10k, 20k)

Are they the same thing?

Or I could get that exact type you posted in a couple of days, I've seen them around.

Essentially , yes VR = VR. They should be fine, they save a lot of space.

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Sweet, so which one should I go with do you think (5/10/20k? ..you mentioned Vr ..does that mean I need a reverse pot or something?) And how/where would I have to hook it up (not sure which of the three pins on these things corresponds to the pins on a regular pot )

 

[GoldenVulture]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Sweet, so which one should I go with do you think (5/10/20k? ..you mentioned Vr ..does that mean I need a reverse pot or something?) And how/where would I have to hook it up (not sure which of the three pins on these things corresponds to the pins on a regular pot )

Start with the 10K, see how it works. If need be change to either of the others depending on how the 10K responds.
VR = Variable Resistance [ pot ].
Your trim pot has the connections marked on it at the bottom of the front face.. The centre wire is the same as most pots, it's the variable wiper.
...........v..............
[ 1_/\/\/\/\/\/\_ 3 ]

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Oh yeah, it's written there ..missed that

Thanks, I'll try that..I'd basically be connecting them in series right? I guess the sweep of the volume pot would depend on where I end up setting the trimpot?

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

I tried the 5k & 10k trimpots in the circuit after the mid-boost/before the master volume (amp input) and they both did the job.. the 10 k was a bit angrier/gainier with a bit more white noise too. The 5k seemed a bit tamer/true to the original signal gain-wise. Both went down to zero. I could use either. Just need to hook up a little bypass circuit with a dpdt/push button now to bypass the mid sweep board when it's pressed. That should take care of that hopefully.

Then it's time to figure out what bypasses what to be able to uses the preamps individually/independent of each other/switch them on and off & also hook up the channel selector/standby switch.

After That I need to figure out the effects loop (want that to be bypassable too) ...and the circuit's done

I played around a whole lot with it yesterday.. for a few hours maybe. There are a whole bunch of absolutely KILLER tones coming out of this thing! And that's without even messing with the EQ (just the mid-sweep). Can't believe how tube-like it sounds (and feels/responds) and how thick/saturated the tone can get if you want it to. I actually can't tell it apart at all from any of my tube amps as far as its response and feel goes. While my Randall T2 & AMT Stonehead are both very tube-like SS amps, in the end ..there's a difference, if only pretty slight. With this one there's actually none I could tell at all. It's easily the most tube like SS amp (or pedal) I've ever played. From the moment I bought that tube preamp kit a few years ago, I could tell it would do wonders in a guitar amp, just like it did for my hi-fi set-up. It's a real "tuberizer". Makes everything you run through it sound like hot tubes

The more I play it the more I realize that by happy as **** coincidence it may actually be my ideal/dream amp tone-wise :lmao:

Fat/juicy/organic/meaty/warm/old-school/smooth-yet-aggressive with some absolutely awesome sweet as **** lead tones as well (overtones & harmonics absolutely through the roof!)

It was my first nice long jam with it & holy **** ...it was a pretty awesome experience if I do say so myself :laugh2:

 

[DankStar]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Can't believe how tube-like it sounds (and feels/responds) and how thick/saturated the tone can get if you want it to. I actually can't tell it apart at all from any of my tube amps as far as its response and feel goes.

That's great. There's something about when you are picking out the components and values of things, you can really make the best amp (or sometimes pedal) for you. In this case, it's not only you because I really dug the clip and thought it sounded like my kind of tone - sort of fuzzy but not messy; beefy but not too boomy/bassy. I keep wondering what the distortion circuit is - you said it was some kind of stand-alone board you got off ebay?

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Thanks Dankstar ..it's a really sweet fat juicy tone that's very old-school and I love it..old Mercyful Fate, Maiden, just about any ballsy 80's metal band. Pretty much the very tone characteristics I dial in with my other amps (or try to)..it's what's in my head.

Not sure if it's pure chance/luck or component choice on my part but either way it turned out great :laugh2:

I got the board off a Russian guy who made cheap clones of well-known pedals. Actually came across him when I was looking for an Amptweaker Tightmetal a few years ago & he had his version of it up there for about 40 bucks. Anyway, I was'nt interested in the clones, but the guy had a bunch of modules and finished pedals & I bought a few of his boards that sounded awesome in a demo/vid he had uploaded because they were even cheaper (half the price) than his finished stuff..so that's what I decided I use here. Always had an amp build in mind for it & the same goes for my tube preamp...it was pretty much destined to be part of a guitar amp build from the day I first heard it :lmao:

Unfortunately the guy has since disappeared off ebay. I thought I'd pick up another of these boards as back-up just in case I screwed this one up, but there's no trace of him there now

The thing is the circuit sounds pretty amazing with just about any dstortion in front. I tried it with a bunch of my pedals too & it sounded awesome with every one of them..

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Yeah, even his vids are gone now. I just looked to see if I could post that one. His pedals were all in wood DIY/cigar-box sort of enclosures..

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Oh yeah, speaking of component choice I "summed" the output of my stereo tube preamp to mono using a pair of resistors just like I saw in a bunch of circuit diagrams. Except I used 470k instead of the specified 470 ohm resistors ..and I've been wondering why the volumes dropped so much compared to the way it sounded before.Thought it might be the trimpot at the amplifier input..apparently not. Oh well time to undo more rubbish :laugh2:

Come to think of it, since the signal into the preamp is summed to mono from a mono source & not stereo like it used to be, do I ctually need to do any ''summing to mono" at the output at all or could I just join both hots/ground outputs and skip the resistors altogether (Golden Vulture?)

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Ok ..so I changed the stereo to mono "summing" resistors from the 470K (oops ) ones that were there to 10K (recommendations for values are all over the place from 470 ohms to aout 20K ohms....I just decided on 10K) and the sound decibels shot back up again .

Sounds the same as before but a whole lot louder, though maybe not as loud as with no summing resistors at all...(still loud enough )

..also discovered that for some reason I don't need the trimpot to match levels between the mid-sweep & the bypass signal from the tube preamp anymore. They're exactly the same volume when I flip between them now...that was lucky.

EDIT: Put the trimpot back in where it was 'cause it sounds a lot better with it there (fuller & less noisy). I think it shunts the noise to ground or something..

Signal levels still match perfectly....everything's on track & sounding sweet. I'm going to give things a break for a day or two now..

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

A liittle comparison between the direct tone & mid-sweep tone..levels are almost the same. I guess the mid sweep could be a tad louder to my ears but I've maxed out the trimpot..still it's close enough to get by I guess.. :bigthumb:

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Well, that slight mismatch between the two volumes was bothering me :laugh2: so I changed the summing resistors from 10K to 15K and it all sounds 100% perfect to my ears now. Absolute match between both volumes. There was the added benefit of more bottom end to the mid-sweep tone as well so it's smoother & rounder/wetter like it was before (with the 470K resistors :lmao but still pretty much as loud as with the 10K resistors. I'm not changing a thing now. It's in it's "sweet spot" so to speak :bigthumb:


Unrelated.. but here's a mock up of the top of the amp (nothing's actually been screwed in yet)



I'm waiting for a pair of black fans and black grilles to arrive (Damn shipping from China :laugh2 They will replace the blue fans/chrome grilles. Then I'll screw it all in with allen bolts :bigthumb: