Hiwatt CP103 build

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shakti
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Hiwatt CP103 build

Post by shakti » Sun Jul 10, 2011 10:05 am

For those inclined to do non-Marshall builds, this might be of interest. I'm about to finalize a clone of a late-69 Hiwatt CP103 aka "The Who" custom Hiwatt 100.

This amp is more or less the same as the earlier Sound City 100-watt amps used by both Hendrix and Townshend in 1967 and 1968. When Dave Reeves stopped building amps for Sound City and launched fulltime into his Hiwatt venture around 1968, his amp design changed gradually towards the DR103 that most people know. However, he did also make lots of custom option models for famous clients such as Jimmy Page. And for Townshend and Entwistle he made amps based on the older design, but with custom "The Who" faceplates, starting late 1969. Check it out:

http://www.vintagehiwattconvention.com/ ... f=5&t=1253" onclick="window.open(this.href);return false;
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

shakti
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Re: Hiwatt CP103 build

Post by shakti » Tue Jul 26, 2011 9:09 am

Amp is finished! Here are some photos:

Here it is with its JPP brother, sitting on a '69 or so Sound City 4x12 with 50W Fanes. This cab is very similar to a same era Hiwatt cab. The difference is that a Hiwatt cab is probably ported while this is entirely closed, and the speakers are not doped, where Hiwatt Fanes are. However, I have never seen an original '68-'69 era Hiwatt 4x12, so I would like confirmation on both of those facts. In the Rock 'n' Roll Circus clip, Townshend has a very sizzling sound which is very reminiscent of this cab. On Live at Leeds it sounds slightly more rounded, but that could be just as much due to the room, the recording and mixing/EQing.

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The cool rear badge, courtesy of VHR:

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And the overall inside photo:

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Input section and first half of preamp. I only had 47uF/25V cathode caps, might swap at least one of them for a 100uF as it seems to yield an ever-so-slightly fuller sound, but the difference is very small. WIll also swap the Mallory for a mustard, since I've got almost everything else NOS

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Second half of preamp. I need a 4700pF mustard if anyone's got one. Will also get a proper 1.8M Piher and replace the 22k which isn't "centered" on the turret board, just for looks.

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Rectifiers and output section:

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Output section, need a 27k Piher here for the bias:

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JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

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Re: Hiwatt CP103 build

Post by myfoot » Tue Jul 26, 2011 10:24 am

Beautiful wiring job!

Roe
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Re: Hiwatt CP103 build

Post by Roe » Tue Jul 26, 2011 10:35 am

I got lots of 100uf grey cathode caps if I remember correctly. gratis of course
http://www.myspace.com/20bonesband" onclick="window.open(this.href);return false;
http://www.myspace.com/prostitutes" onclick="window.open(this.href);return false;
Super 100 amps: 1202-119 & 1202-84
JTM45 RS OT JTM50 JMP50 1959/2203/34/39

shakti
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Re: Hiwatt CP103 build

Post by shakti » Tue Jul 26, 2011 2:10 pm

That would be really sweet! What voltage are they? Let me know if you need anything, Roe.
Also looking for a 1k 1W carbon comp and a 22k 1w carbon comp.

The amp is starting to break in and sounds very cool now with a P90-equipped SG Special. Quite unlike any other setup I've tried, but it really does dish out a Townshend sound - extremely crunchy, very tight and fast, and with the most amazing clean-up with the guitar volume. The SG Special with amp on full, but guitar volume rolled back, is the most sparkling clean amp I've ever tried, even more so than a vintage Super Reverb or AC30 with a Strat. The Sound City cab with Fanes really does contribute to that though - sounds huge!

My Jimmy Page clone took a looong time to break in, but is now sounding excellent. I hear some of the same somewhat congested sound that the Page amp had initially in this amp still, but I only have some 6-7 hours on it yet, and even that time has brought on a lot of change in a positive direction.
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

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Re: Hiwatt CP103 build

Post by Roe » Tue Jul 26, 2011 2:11 pm

the 100uf is only 10v. its a nos japanese cap type that sounds very good. I have hundreds of these caps
http://www.myspace.com/20bonesband" onclick="window.open(this.href);return false;
http://www.myspace.com/prostitutes" onclick="window.open(this.href);return false;
Super 100 amps: 1202-119 & 1202-84
JTM45 RS OT JTM50 JMP50 1959/2203/34/39

shakti
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Re: Hiwatt CP103 build

Post by shakti » Tue Jul 26, 2011 2:18 pm

Sounds perfect! Let me know if you'd like a couple of these RIFAs.
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

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neikeel
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Re: Hiwatt CP103 build

Post by neikeel » Tue Jul 26, 2011 5:35 pm

Beautiful job!

I recently serviced/retubed a stock DR103 and yours is certainly up to scratch.

I liked the amp a lot and if I had not got Marshall clones to finish............. :roll:
Neil

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VintageCharlie
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Re: Hiwatt CP103 build

Post by VintageCharlie » Sun Nov 27, 2011 2:02 am

wonderful build! :champ:
Are the Sound city Mk I very similar to those? What are the differences? Same trannies?

shakti
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Re: Hiwatt CP103 build

Post by shakti » Sun Nov 27, 2011 3:13 am

They are just about identical. There's as much variability between different CP103s as between a CP103 and a Sound City One Hundred. The SC ones had a dual 8uF cap for the preamp though, which is hard to find today.
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

shakti
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Re: Hiwatt CP103 build

Post by shakti » Sun Nov 27, 2011 3:20 am

BTW, I am planning to dress this up as a Sound City One Hundred, but with a metal Hiwatt badge, exactly like Townshend's amps. I've found an excellent Sound City front panel repro and metal Hiwatt badge, but I need the proper headbox. The early Sound City cabs had more square corners and the piping runs the other direction, arond the whole circumference of the cab. If anyone has got a clue or hint where I can find a headbox like that, or have one made, I'd appreciate any suggestions.

The amp itself sounds great, but is veeeery loud and somewhat stiff sounding. It's also a bit scooped sounding, which along with the very efficient speakers in the cab makes for a brutally crunchy sound which is totally unforgiving on lead lines. I think I want to try ARS caps in this one, as some people report those as having a less grainy sound and more meaty mids than F&Ts. Maybe try a M e r r e n output transformer as well.
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

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VintageCharlie
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Re: Hiwatt CP103 build

Post by VintageCharlie » Sun Nov 27, 2011 4:06 am

Shakti, why go with repros? From what i know the company that took over Pertridge still makes Partridge trannies with the original equipment and construction plans for them? See here: http://www.vintageamps.com/plexiboard/v ... hp?t=75193" onclick="window.open(this.href);return false;
There's also a link to the company: http://www.transformers.co.uk/index.asp?pgid=19" onclick="window.open(this.href);return false;
I remember another post on plexipalace and the trannies were really quite expensive (though nothing terrible, as you'd pay shiopping and taxes from US anyway, which drives the cost up considerably). And they were that expensive because the guy ordered one transformer - so they have to set up everything for that one transformer. With a group order the price should fall quite a bit.
I'm thinking about a Sound City too... Axis :) Well, yeah, from recordings and clips i have heard of this amp, it sounds to me like it is pretty much as Hi-Fi of an guitar amp as can be - very clear, articulate, almost neutral (sounds to me like that at least - i think we're used to the pushed Marshall mids and neutral sounds like scooped to us :) ). There's something i like about the tone and something that i don't. In recordings it seems that the crunch is very "hard", not smooth at all - little compression, if at all too, which means you can't really get away with diming it and smoothing it out. If there really was a sound city/ hiwatt at Axis sessions, i wonder how he got those (semi)-cleans out of it, as all other recordings that are reportedly hiwatt or sound city simply don't get that tone :what:
I'd shoot rather for a Sound city than a hiwatt too, especially if you have a JP Hiwatt. Also, as Sound city still kind of has that "Sound shitty" nick name attached to it's brand, it could be fun demonstrating people tht it is not entirely true with the one designed by D. Reeves :)

Did the trannies on the MK1 and the Hiwatt DR103 have the same exact numbers too?
If you're interested in those trannies from UK, please let me know, i'd be into these too.

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VintageCharlie
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Re: Hiwatt CP103 build

Post by VintageCharlie » Sun Nov 27, 2011 4:39 am

Here's a bit more info on the transformers.co.uk trannies: http://www.vintageamps.com/plexiboard/v ... hp?t=68747" onclick="window.open(this.href);return false;

The price mentioned in 2008 is 325 gbp (about 520$) for PT and OT (might be more by now though). Sounds like an awful lot until you count in shipping and taxes for your Heyboers traveling to Europe: 320$ for the trannies + about 100$ for shipping = 420$ + about 100$ of taxes and customs and you end up at 520$ vs 560$. A group order of 10 should be possible and then one might get even below the imported Heyboer price, shipping included and have something that, by the looks of it, is more authentic (or should be at least, as it's done by some of the same employees from Partridge and with the same equipment, from what i could gather). From outside Europe this might sound very expensive, but in Europe this would be quite a reasonable deal.

shakti
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Re: Hiwatt CP103 build

Post by shakti » Mon Nov 28, 2011 8:12 am

I wouldn't be so sure that the old and new Partridge transformers are the same quality and build. After all, we're talking about a transformer originally made almost 40 years ago. You'd be hard pressed to find many of the same employees, let alone materials. Hiwatt dropped Partridge around 1980 or so, though I don't know why.

As for the sound of the amp, you're absolutely right that they are somewhat stiff and almost hi-fi sounding. I am still struggling to get a good sound with a Strat - it's extremely bright and clean sounding with single coils. In fact, the SG Special with P90s is the only guitar I like with it, but that sound...oh my! It's no wonder Pete settled on that guitar with his setup. With a '71 Hiwatt 4x12 with 122231 speakers (which are kind of the Fane "G12M" equivalent vs "G12H" in my SC cab and Townshend's preferred cabs/speakers) it's much more forgiving and toneful in the mids. I still think there's more tweaking potential in the amp though. First up is to put 4 output tubes back in vs the 2 I'm using now. That should drop the voltage a little more and brown it out a little. Next up would be to try some different filter caps, and lastly maybe a different OT.
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

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VintageCharlie
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Re: Hiwatt CP103 build

Post by VintageCharlie » Tue Nov 29, 2011 10:53 am

How does it sound through a marshall 4x12? What kind of OT would you have in mind? one with a narower bandwidth?

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