Hiwatt-based preamp

[syndromet]

If anyone is interessted, here is a Hiwatt custom 50 simulator using Jfets. I haven't tried this yet, but I guess this will make a good preamp. Just run it at 18V, and use some 500k or 1M Trimpots.

I have named it Hiawatha Click the images for bigger versions.

Schem:


vero-layout:

[RDV]

Looking forward to sound samples. 

RDV

[syndromet]

Well, I guess there will take some time before I can build this. I'm in the middle of redoing my appartment and moving. On the top if this I'm having a daughter in a couple of weeks. But I'll let you all know when I have build my first proto-type.

I've understood that you are a big fan of the Who, RDV. I also understand that you have had a Hiwatt? Let me know if it sounds  anything like your original when I get around to build this.

[RDV]

Wow, I yak about me a lot on line don't I!

I had a Hiwatt that never worked right till I had it retubed and biased and then found out that no one wanted to hear me that loudly so I sold it to a heavy metal bass player.

I may try out the circuit myself this weekend. I'll let you know.

RDV

[syndromet]

I've got it up and running, but I havent tried it with a higher voltage than 9V. I had a few troubles getting it to work, but they should be corected now. This thing sounds good, and has a very classic rock sound.

Things I like about it:
The Briliance-switch does a lot to the sound, and gives it a little more bite.
Good classic rock distortion
Very silent.
Useable range on the tone-controll.

Things I'll change:
The presence controll needs some work, as it is barely notiseable like it is now
Needs a mpf102 in the first stage, otherwise youll have some oscilation and a harsh overdrive.


Theese clips were recorded Guitar->Hiawatha->soundcard, and I've used guitar rig to simulate a twin reverb through a 1*12 speakercab.

j201 in first stage
Humbucker
Single coil

Mpf102 in fist stage
Single coil
Humbucker

So, RDV, is there anything Hiwatt--like in the sound?

[teemuk]

The last two clips sounded very good. By swapping that fet you lowered the gain of the first stage, right? It really made a difference, IMO the first two clips sounded pretty bad while the last two had a "smooth" overdrive sound that I really like. Did you rebias or make any other changes (with MPF102 the circuit sounds less bright)?

[syndromet]

The last two clips sounded very good. By swapping that fet you lowered the gain of the first stage, right? It really made a difference, IMO the first two clips sounded pretty bad while the last two had a "smooth" overdrive sound that I really like. Did you rebias or make any other changes (with MPF102 the circuit sounds less bright)?

I found the circuit to be a little brighter and "rounder"-sounding with the mpf102 in the first stage. The mpf lowers the gain of the first stage, wich affect all the other fet's aswell. IIRC, I had to rebias when installing the mpf. I had to do this at realy low volume, so it's not correctly biased. Thats why it sounds gated and fuzzy. When the bias is set correct you will have a very nice classic rock sound, without the "Fizz" you hear on the mpf102-clipps. (and j201, for that matter). I'll try tweaking it this weakend, and post some new clips, this time with a tuned guitar....

The circuit also have a huge volume-boost, so I think this could be a nice preamp for a chipamp. I'll test it as soon as I find a transformer for my lm1875 kit.

[joecool85]

Sounds good to me!  I especially like the MPF102 clips, mostly the humbucker.  What type of guitar is that?

[syndromet]

That is my trusted Epiphone Les Paul. It's a great giutar, but you have to try them out if you're buying one. Some of them are realy bad too. I used to have a set of di-marzios in it, but found out I like it a lot better with the stock PU's. This guitar gets better for every year that goes, and I'we never had a problem with it for the nine years I've owned it. Top quality for a great price.

[joecool85]

Les Paul Standard?  I've been looking at getting a Epi LP JR.  I need to find a place around here that carries them so I can play one.

[syndromet]

Yes, it's a Standard. I've played a few specials, and some of them are prety good. I don't think you'll save anything on buying a special, since they need a a major upgrade in the hardware section to be useable.

I'ce never tried a JR yet, but I thinkI would miss the neck pickup if I did. I'm sure it's a great guitar, though.

[joecool85]

I dunno, I never use the neck pickup on the guitar I have now.  I really like bridge pickup sound.

[syndromet]

I dunno, I never use the neck pickup on the guitar I have now.  I really like bridge pickup sound.

I know what you mean. I used to be a metal-to-the bone kind of guy, always using my bridgepickup. I actually thought about ripping ot the neck pickup, and make the cavity a place to put pyrotechnics. Glad I didn't do that.....

As the year envolved, I found that I started using the middle-possition more, and more, with the volume of the bridge a little higher than the vol of the neck. This fattens up the sound when riffing, and when it's time for a solo, you just flick the switch to the bridge possition. Also, if you're using octave effects, they sound a 1000 times better with the neck pickup and tone rolled down. Now I can't see myself playing a guitar without a neck pickup.

[Stompin_Tom]

hmmm... I really like the idea of this preamp for a chipamp because the hiwatt power amp was pretty clean/hifi back in the day. That is, unlike marshalls and the like, there was less sag in the power amp. Should be able to make this into a good sounding solid state. My friend actually has two hiwatts (100 watt head and 4X12 cab and a very strange 100watt 2x12 combo - not too many of those were made) and this sounds way grainier and muddy to my ears. For me the defining tonal characteristic of his amps are how clean they sound. I'm not talking jazz amp clean, but clear and chimey... I think of it as just about as HiFi as you can get a big honking tube amp. If you think of pete and the who, his tones were never really that overdriven. I think the idea was to see how loud you could get a clean tone (with a little bite added). And, fyi, the presence knob on a hiwatt really adds a world of bite.

Anywho, I wish I knew more about electronics so I could help tweek this circuit, cause I'd really like to build one when it sounds good!

[syndromet]

Hi.
This preamp add a great distortion when the knobs are turned all the way up, and there is a lot of different sounds playing with the gain and volume controlls. It can go from a clean, sparkley sound to a classic rock-type distortion/overdrive. I guess it sounds a lot like a hiwatt, and when cranked it sound like a tube-amp pushed hard. I really like the sound of this, but I really wish I could get the presence-controll to do something. I don't have a lot of time to work on stompboxes these days, but when I'll get the time I'll try to get the presence to do something.

Running this on 18 volt would give you a lot more headroom, giving you less distortion at higher volumes. Running this on 18v I guess this will be a really good tube-like preamp, giving a great breakup ehen pushed. I'm planning on trying this when my Lm1875 amp is finnished.

I changed the Gain and Volume-controlls on the schem and layout, but they should be 500k as they were on the first schem. The reason I changed them was that I had misswired the pots, so they didn't work propperly.  When wiring things up the right way, 500k turned out to be theperfect value.
 
Even if the precence controll doesen't work at the moment, I encourage you to build this. As soon as I get the presence controll to work, it will (hopefully) only be a few components that should be changed. I would really like the feedback from someone who knows what a Hiwatt sounds like.

I finnished the box for this earlier today, so I'll post pics and soundclipps when it's finnished.