My newly built Hiwatt DR504 clone

[DCCable]

I have been interested in Hiwatt for quite some time and thanks to the excellent resource of Mark Huss's Hiwatt web site I decided to take the leap and built a clone of one of the earlier Hiwatt amps. First of all coming up with the appropriate parts to do a reasonably accurate clone is not the easiest thing in the world to pull off here in the states. I ended up getting the chassis and the front/back plates from Modulus in the UK. While there are many Marshall style chassis available the Marshall chassis is smaller, with different dimensions than the classic Hiwatt chassis. I also got the transformer brackets from a couple of European vendors since I was unable to find them stateside. And the same story with the cab; nothing pre-made stateside. So I ended up fabricating that myself. For transformers, I was able to secure a couple of Classic Tone units that I was able to find online (Classic Tone went out of business around the first of the year.) So I ended up with a power transformer for a Marshall 100 watt amp and an output transformer for a Marshall 900 50 watt amp. It should be noted that the Hiwatt chassis for their 100 watt and their 50 watt amp is the same animal. I used 1 watt metal film resistors everywhere instead of 1/4 or 1/2 watt resistors.

I'll not try to describe that Hiwatt sound here; there are a number of YouTube videos that do a pretty good job of that. I will say that even after watching a number of them with a really good set of headphones they're not like playing through one. Now for some photos:

 

[Buzzgrowl]

I've always wondered how is a Hiwatt different from a Marshall. Never had a chance to A/B a pair. Nice work!

 

[DCCable]

I've always wondered how is a Hiwatt different from a Marshall. Never had a chance to A/B a pair. Nice work!

They're totally different animals with very different sounds. There is the persistent story out there about how loud Hiwatts are; they're true. They also take the concept of touch sensitivity to a whole new level. More than any other amp that I've experienced who's playing it really matters in the sound. Also, the tone stack seems to do a lot more than a Marshall tone stack.

 

[eslover]

Great job @DCCable

I did almost the exactly same thing for building my DR504. My avatar has the completed amp, and I can post some gut shots but don’t want to poo-poo on your thread.

I’d be interested in seeing the voltages you are getting and what your “clean” output rms is. By the way I’m getting 58 watts rms output and this is the loudest amp I’ve ever built for sure. Sounds glorious though.

 

[DCCable]

Great job @DCCable

I did almost the exactly same thing for building my DR504. My avatar has the completed amp, and I can post some gut shots but don’t want to poo-poo on your thread.

I’d be interested in seeing the voltages you are getting and what your “clean” output rms is. By the way I’m getting 58 watts rms output and this is the loudest amp I’ve ever built for sure. Sounds glorious though.

No problem. I'm getting 60 watts rms (single sine wave at clipping) My PS output with no load on it is 505 volts, V1 has 211 and 205 at the plates, V2 has 200 and 462 at the plates (I'm using a cathode follower to drive the tone stack.) V3 has 236 and 337 volts at the plates V4 (PI, 12AT7) has 290 and 302 volts at the plates. the outputs (JJ EL34s) have 480 on the plates, 468 on the screen grids and the bias is at -46 volts. And I'd like to see some of your gut shots.

 

[eslover]

This was my summer pandemic project last year...

I put an adjustable bias pot in...

 

[DCCable]

This was my summer pandemic project last year...

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I put an adjustable bias pot in...


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Very nice. Looks like you exactly followed the Hiwatt wire routing scheme. I can never seem to get wires to lay exactly straight and make exactly 90 degree bends like that. I changed some things on my wire routing starting with an extra turret row at the control end of the chassis which has ground and HV wiring underneath attached to appropriate points. The other big thing I did was not to follow Dave R's ground scheme, I only have one signal ground to chassis connection at the input jacks. All other grounds are tied to a buss (Well, except the power safety ground.) Oh and using a 100 W PT I ended up building the 100 watt power supply version with the bridge rectifier. That third board also has my bias adjustment and DC heater voltage elevation circuits on it.

 

[Deeve]

I'm impressed w/ how clean this looks.
fwiw, I kinda liked the raw wood casing, too

Peace - Deeve

 

[eslover]

Thanks, 20awg solid core is your friend when used in the right places.

your rewiring approach is smart especially for those turrets that would otherwise have 4 or more tie points.

but I must say the modulus amp stuff is very high quality and for anyone interested I highly recommend it. Even with shipping from Scotland it is not that much more expensive than high quality U.S. stuff.

 

[DCCable]

I used this stuff from TubeDepot. I did really like the way it soldered even though it didn't want to stay straight.

https://tubedepot.com/products/18-ga-tin-plated-aerospace-grade-tefzel-wire

 

[DCCable]

Thanks Deeve, the case didn't stay that way as I was going for as close to an original look as possible, within reason. It's Home Depot 3/4" (approximately) plywood, clamped and glued together with joiner biscuits. It's what got covered with the tolex seen in the last photos.

 

[eslover]

@DCCcble I recommend Steve at ApexJr ( apexjr.com ) he sells PTFE solid core in many gauges at very reasonable prices - its great for wiring the preamp and in some other spots in an amp. The Teflon sleeves on this wire is thin and gives a tidy look. I use the 20 gauge wire and it bends nicely I realize that I probably could’ve gotten away with the 22 gauge which I’m sure gets less cramped on those British turrets. Maybe next time !

 

[DCCable]

@DCCcble I recommend Steve at ApexJr ( apexjr.com ) he sells PTFE solid core in many gauges at very reasonable prices - its great for wiring the preamp and in some other spots in an amp. The Teflon sleeves on this wire is thin and gives a tidy look. I use the 20 gauge wire and it bends nicely I realize that I probably could’ve gotten away with the 22 gauge which I’m sure gets less cramped on those British turrets. Maybe next time !

Thanks, I'll check him out.

 

[zeppelinofled69]

Dang, real nice builds all around. I did a DR103 last year and have been absolutely floored with the results since building it.

I like to run it alongside my JTM45 to really round things out and move the stuff on my shelves.

 

[DCCable]

Yes, that's nice! You guys have me in the mood to upgrade. I just ordered a Heyboer 100W output transformer.

 

[eslover]

That’s a really clean looking build @zeppelinofled69

is that the mojotone kit?
I’ve heard good things about it, but have they stopped selling it?

 

[zeppelinofled69]

That’s a really clean looking build @zeppelinofled69

is that the mojotone kit?
I’ve heard good things about it, but have they stopped selling it?

Thank you for the compliment!

Yeah, that's the Mojo Kit. I struggled with trying to find parts on my own as that is typically how I like to build. Like @DCCable says above, these parts are tough to find over here in the states, and I didn't want to spend a ton on shipping just to get a chassis and faceplates.

When I found the Mojo kit I was a little skeptical, but they really do a good job of selecting the parts and everything was very good with only the input jacks being the one thing I may change out eventually for some real Cliff jacks.

It is definitely possible that they have pulled the kits for now. I know Iron is getting really hard to come by, and the Heyboer Hiwatt iron they normally sell has been sold out since about a month after I ordered my kit.

 

[DCCable]

I had no idea Mojotone was selling a Hiwatt kit. I have been on their website a whole bunch to times as I sometimes get pickup parts from them but have never seen the Hiwatt kit. I know they've been out of the Hiwatt transformers for quite sometime.

 

[zeppelinofled69]

Actually, it looks like they are still selling it...

https://www.mojotone.com/Mojotone-Custom-100-Amplifier-Kit_4

No Affiliation to mojo, just passing the link along.

EDIT: OOOF, looks like they are up to a 6-8 week lead time on kits though. I waited 5 weeks for mine and that was painful for me... YMMV

 

[DCCable]

Okay, those sneaky folks at Mojotone don't use the Hiwatt name anywhere there. So a website search for a Hiwatt kit probably turns up zip. Not a bad price for the kit complete. If I were to build another one I'd probably go that way; although not the circuit they show.