vintageHIWATTconvention.com

I thought you might find this interesting (from http://harryjoycerocks.com/shop/?p=491):

Although many people believe that these are the same, there are some major differences in sound and design. Besides the fact that Hiwatt amps underwent many changes throughout their production years themselves, which changed the sound. Harry Joyce amps were actually the product of all the changes made. Originally Hiwatt amps came with .047mf coupling caps versus the Harry Joyce .022mf best known as the “Marshall Value”. This gave the amp slightly less bass, but this was compensated in the first stage by means of introducing a 150mf cathode bypass cap. Early Hiwatt amps on the other hand used a .047mf in the Brill input, and none in the Normal. Another change was made to wire the first preamp tube cathodes together, where the original resistors were 2.2K each now both cathodes were summed through a 1.5K resistor and a 150mf cap across. The second stage on Hiwatt amps used only half of V2. Harry Joyce amps use the whole tube by cascading the inputs of V2a, and V2b for more gain. The bias feed resistors changed from the 100K to 220K. This resulted in a more aggressive sound, and unlike the older Hiwatts that had two preamp to poweramp coupling caps (.047 mf one for two tubes along with two 22K resistors for the 100Watt version) the Harry Joyce doubled up in terms of having four .022 caps with four 22K resistors.The idea behind was to make the amp more stable, and balanced. Additionally the Harry Joyce amps had no bias adjuster, because according to Mr. Joyce the old Mullard EL 34′s were so consistent that it was not necessary. Nowadays it might be most important. Early Hiwatts came with the grids of the phase inverter V3 (12AT7!!) wired together to the cathode resistor of V4b through a 100K resistor. This design was later changed to a 220K resistor. This change gave the amp less responsiveness and sounded not as full. Power and output transformers changed from Partridge to a custom wound type, and the 100Volt output tap on the ohms selector got omitted.

Picshttp://ampgarage.com/forum/viewtopic.ph ... 38c7603215

I'm getting the impression that HJ just tweaked the early 80s lead circuit. can anyone confirm or rebut this?

I agree.

--mark

Interesting read .. thanks Roe !

I have an '82 OL103 . It's loaded w/ Mullard pre's and XF2 Mullard EL-34s .
I can't imagine a Harry Joyce 100 being more aggro' than this amp, but I've never played an HJ amp so I can't offer any comparisons.

Do the Joyce amps have even more gain ?

I've only played one Harry Joyce amp, a 100 watter. This one was way cleaner than Biacrown era Hiwatt with the OL circuit, but a little more aggressive than a 4-input 70s Hylight DR103. Harry Joyce built very few amps with his name on the face plate, and I'm certain that they were all the same.

I once owned an '83 Biacrown era OL504....it was very very high gain. The dirt kicked in with volume knobs at 9:30 position.

Hello good people,

I encountered this statement in this post on Harry Joyce's amps:

" the Harry Joyce doubled up in terms of having four .022 caps with four 22K resistors.The idea behind was to make the amp more stable, and balanced."

Can someone please explain to me the benefits of placing four coupling caps?
I just can't come up with any reason why this would make the amp "more stable and more balanced".
Can someone please shine his light of wisdom on this? I just don't get it...

Thanks in advance!
Greetz,
Frits van Mourik
-please pardon my french; I'm dutch...

I think they mean using .022 to each output tube instead of .047 to each pair of output tubes (a la classic Hiwatts). I don't have any 100-watt HJ pix to confirm this.

I agree,I don't see where this adds anything except parts count and complexity.

Roe wrote: ↑Fri Aug 17, 2012 12:24 pmThe second stage on Hiwatt amps used only half of V2. Harry Joyce amps use the whole tube by cascading the inputs of V2a, and V2b for more gain.

Interestingly, the HJ’s I have seen feature a 1K5 and a 0.022uf cap wired on V2. We tried this on a DR clone and it cut a bit of gain, as well as a lot of bass. Raising the 1K5 to 15K brings in lots of gain, but not bass.

Why would be the reason behind this? Did HJ use transformers that were very bass heavy?

I'm assuming you are referring to the cathode bias on V2a, on a Biacrown era Hiwatt "OL" model (which also uses the other half of v2) this is biased with a 1k resistor and 47n cap, very similar the HJ. The 22n cap in that position will be very slightly brighter, but the biggest difference would be just in the fact that the stage is bypassed vs. unbypassed (cap or no cap). And yes raising from 1k5 to 15k should introduce noticeable distortion because that stage would be biased colder, which brings with it "cold clipping" distortion. Many people like this distortion which is why Marshall JCM 800's have a cold clipping stage on V1a in the form of an unbypassed 10k resistor, and Soldano amps as high as 39k. I highly doubt the HJ trannies were much different then Hiwatt, but I could be wrong.

It seems that, when turned up, the HJ is capable of a bit more gain than a regular Hiwatt DR. Maybe the 1K5 resistor and 22uF was used for a tighter/more modern sound on higher volumes?

FYI: The reason why I'm interested is because I had a Hiwatt/HJ clone built to use in a Black Crowes tribute. The rhythm guitar player I'm covering used HJ amps almost extensively in the '00s and he had his fully cranked up! I don't play on such loud volumes so we removed the 1K5 resistor/22uF cap in my clone when we found out that it cut quite a bit of low end.

Apparently you didn't remove the 1k5 cathode resistor altogether, or the amp wouldn't work!

There's no small cathode cap change that would cause a bass bump. You'd have to move it up to 10uF or something.

Hi Mark,

No, just the extra 1K5 resistor and 22uF cap on V2.




(picture of an original HJ)

First off what you've highlighted does not have to do with the cathode bias on v2, so you can ignore my remarks on the differences between bypassed and unbypassed and cold clipping etc. Second I'm not familiar with the schematic you've circled, it looks just like Mark's OL schematic but instead of a 1k5 resistor it should be a 47k to ground. I'm assuming this is a change you made, I agree though the HJ does appear to have a 1k5 resistor in that position. I do not recommend removing that 22nf coupling cap on v2, but I'll let Mark chime in on that. Otherwise if you are looking to get more overdrive out of it, you could try experimenting with how v1 is biased (the OL is 150uf/1k5 there), that's usually the easiest/simplest way to tweak it.

FYI: I made this schematic based on pictures of various Harry Joyce amps. Mark's OL schematic was used as a template (sorry, Mark!).



I'm not necessarily looking for more overdrive, just interested what differences Harry Joyce and later his companion George Scholtz made to the design. The later Harry Joyce's sound thicker and less bright than regular Hiwatts and even the early HJ's.

You can hear the differences in this topic. There's a link to Soundclick with 9 soundfiles, 3 of each amp (early HJ, later HJ, Hiwatt DR504).
https://www.thegearpage.net/board/index ... nd.780419/

The amps are:
test 1, 4 & 7 = HJ CST-50 #7 (early stock circuit, more mids and more aggressive)
test 2, 5 & 8 = HJ CST-50 #23(early model updated to HJ + George Scholz latest specs, with more low-mids, less highs, a bit less agressive )
test 3, 6 & 9 = 71 DR504 (stock circuit, cleaner sounding, super well balanced, touch sensitivity with this amp is just unreal)
On files 7 and 8 the guitar volume is kept at around 8 to reduce gain. On file 9 the guitar volume is all the way up.
All amps had the master volume at around 2:00.

My schematic (and my clone) is based on the earlier HJ's, I have yet to find pictures of the later ones.

I listened to the sound files. I think the later HJ does not sound very good to my ears, the attack and clarity seems to be gone and it seems to be kind of spitting sound. So personally speaking I would not aspire to capturing this sound. The early HJ sounds pretty much like an OL to me. I still think if you were to mod your amp I would start with the v1 bias, something like this is easy to try (and undo) and you might like it:

(the one on the right is obviously the modded one)