Suggestions for a low wattage Hiwatt style amp

[liddokun]

I may be acquiring a broken Hiwatt solid state combo soon, thought I'd build something new into the chassis. 

Do y'all have any good leads to projects for a Hiwatt style low wattage amp?  I realize a low-watt Hiwatt sounds silly, but I'm hoping there's something out there.

I know AX84 has a Lowwatt project, but even then that's got a dual el34 output section, perhaps there's something that's lower wattage, maybe something single ended. 

[pompeiisneaks]

Just so you're aware, you'll likely need to replace the power transformer, and add an output transformer, as this is a solid state amp you're mentioning, which uses a single power transformer with voltages often no more than 50VDC, and no output transformer.  That being said, you can usually couple the power section of most amps with a decent preamp with a few exceptions, (sometimes the PI needs to be altered, from what I recall, for certain power tubes) but the best answer is 'it depends on what you want for the output section'.    OR you could do a tube preamp, and keep some form of solid state output section, which could then be controlled on output volume pretty easily and linearly.  I don't know for sure, though, if a Hiwatt gets it's tone from preamp distortion, power amp distortion or both,  If it's the last two, then it would be tricky to do in lower wattages sometimes. 

Hopefully that makes some sense.

~Phil

[liddokun]

Just so I'm clear, I'm only planning on using the chassis and cabinet, so it'll be completely new electronics. 

Some reading has taught me that for the most part, some people out there think that Fane speakers and an interesting tone stack and PI configuration at least contribute somewhat to a "Hiwatt" sound.

So I suppose I should be looking into how the original Hiwatt tone stack and PI was set up, first.  Trying not to recreate the wheel if I don't need to.

[pompeiisneaks]

Here's a great place to look for that data:

https://hiwatt.org/tech2.html

tons of schematics of different period ones.  Pick the one you're trying to do, and go from there, he also has layouts.  Then at the PI output you could change the power section to something much smaller.  Not sure if you want PP 6V6 or what etc.

~Phil

[OrganicEffects]

The Trinity Triwatt is out there - don’t know if they made the scheme available or not.

[liddokun]

@pompeiisneaks

Thanks for the link.  I'll do some reading and see what I can come up with.  I was *thinking* about building something single ended, but I'll look through that hiwatt resource and maybe I'll change my mind. 

@organiceffects

I'll have a look into the Triwatt as well.  I think Trinity is based in Toronto which is useful since I live here too. 

[Ritchie200]

Liddokun

What are you looking to achieve?  Will you be doing windmills, air splits, and soccer goal knee slide celebrations, expecting to sound like Pete?  Are you looking for something you can drop a mic in front of on stage and still hear yourself above the drummer (and still sound like Pete)?  Or are you looking to just shoebox something in that space and play in your bedroom?  I think your expectations/available real estate will be driving this decision.  Which broke SS Hiwatt combo will you be getting? Do you have room to hang some tubes on the bottom of the chassis without banging the speaker(s)?  How much room you have may also determine which tube or tubes you are considering.  The Lowwatt might be a ready to go project for you if you are leery about cutting and pasting - although there are folks here to help you with that.

The reason I bring all this up is I see posts all the time about people disappointed that their low wattage copy amps do not sound like their preamp topographied big brother with the big bottles and big wattage.  If you want to sound like Pete, you need a DR or a Kemper.  If you want to sound like Pete, want to keep your hearing, and want to build something - build a DR and power scale it. Heck you will almost have it built if you copy the preamp and you are buying all new iron anyway.  That way you have all sorts of options, from stage to recording at any volume - and you WILL sound like Pete.  Use the combo shell for a AC4!

JMHO, but I have a thing about old big amps....
Jim

[liddokun]

Hi Ritchie200,

I agree with you and I see plenty of people wanting to build low wattage versions (and then becoming disappointed) of these big bottle big wattage amps.  Not really my intention here and I know the limitations to trying this.

The amp in question is the Hiwatt Bulldog 30R.  The reason I'm looking for a low watt project is that there will be physical limitations (as you have also pointed out).  I can hang some tubes and iron, but low watts will potentially mean less tubes and thus it won't be as challenging.  The reason I was looking for a Hiwatt project in particular is because I'd feel remiss building a different circuit into a Hiwatt chassis/cab.  I personally think it's a handsome looking amp and I don't want to mess with the aesthetics. 

The lowatt might be the ready to go project for me, but it's still got 6 tubes in it.  I was looking around to see if I could even scale back even more. 

[shooter]

physical limitations

you have to decide if most of what I like about __________amp comes from the front or back of the amp, if it's the front, mate it with anything class A, done.  Me, I'd stretch the chassis and meld it with a KT88, runnin near melt-down 

[tubenit]

What about using a 300-0-300 PT with tube rectification & cathode biased with this HiWatt schematic with EL34's ?

https://el34world.com/charts/Schematics/files/Hiwatt/Hiwatt_50w_dr504.pdf

With a 5V4, you'd get about 360v on the plates for maybe 36w or so?   

OR use a GZ34 for 390v     OR use a solid state plug-in rectifier for 420v

I can not remember the source, but IIRC ………… there are some guys using cathode biased EL34's on Trainwrecks (I think?) for around 30w amps?

You can look at the Matchless Clubman for an idea for cathode biasing EL34's.    Matchless claims their Clubman is around 35w.

https://el34world.com/charts/Schematics/files/Matchless/Matchless_clubman.pdf

With respect, Tubenit

[VMS]

How about Hiwatt custom 7
Maybe you or someone can draw the schematic from this inside picture.
Looks like only 3 of the 4 gain stages are in use.

[liddokun]

@tubenit
Yes, there are lots of possibilities if I want to roll my own kinda deal. 

I think I'm going to go solid state rectifier regardless of which circuit I choose. 

Looking into one of the AX84 projects where they're using a single ended el34 as the output section, and perhaps feeding that with a Hiwatt style preamp/tonestack/PI.

@VMS

That's a good reference to have.  Looks like 2 12AX7s feeding a single EL34. 

[silverfox]

I think one of the significant circuit features of the DR 504 OL, at least that's the name of the schematic I've got, one of the significant features is the voltage regulator on what looks like the bias circuit for the phase inverter. That would lend to HiFi ish tones. Very balanced.

[shooter]

NICE use of 1/2 a tube, I might steal it 

[sluckey]

That's just a buffered voltage divider. Nothing regulated about it.

[OrganicEffects]

How about Hiwatt custom 7
Maybe you or someone can draw the schematic from this inside picture.
Looks like only 3 of the 4 gain stages are in use.

Wait... you’re allowed to do heater wiring like that???

[sluckey]

Kinda blows all those "twisty" myths away doesn't it? 

Lot's of ways to properly wire filaments. I usually twist but I did a couple amps like this just to mess with Ed's head!   

     http://sluckeyamps.com/6v6plexi/P-6V6_05_big.jpg

     http://sluckeyamps.com/dual_lite/big_guts.jpg

[silverfox]

Why, what, would be the difference or reason for using a buffered voltage divider as opposed to a voltage regulator? Trying to isolate something??
Was this feature then, not really necessary? If it did add value, what does it add to the performance of the circuit?

silverfox.

[shooter]

If it did add value,

I jumped on the goolge train and didn't find what I was looking for but I did stumble on this

https://www.tubecad.com/2006/06/blog0068.htm

I like this quote;

two stages are not as pure as one stage. For others, cathode followers are creepy in general.

[silverfox]

If it did add value,

I jumped on the goolge train and didn't find what I was looking for but I did stumble on this

https://www.tubecad.com/2006/06/blog0068.htm

I like this quote;

two stages are not as pure as one stage. For others, cathode followers are creepy in general.

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