Hiwatt SAP "Jimmy Page" turretboard layout

[Turret]

This is preamp part of Hiwatt Jimmy Page SAP (Special All Purpose) 100W head.

Download high resolution PDF file here

My layout visually is based on the picture of (AFAIK) real Jimmy Page Hiwatt that can be found online. All I had is that picture, and Mark Huss @ hiwatt.org schematic.

Mark Huss’s schematic is the only schematic ever issued and I would thank you Mark for all Hiwatt resources he did

Schematic in my documentation is redrawn from Mark’s schematic with couple of additions

While drawing my layout few more suspicions came to my mind that I listed below:
- first of, C3 cap across R15 resistor is not presented on pictures of JP Hiwatt
- C16 have smaller dimension, it might be different (smaller) value or simply lower voltage (100v or 160v), and that might be it, as it is an cathode resistor bypass cap and doesn’t need to be high voltage (400v)
- R20 is hidden by big e-capacitor, and it’s hard for value verification. On Mark’s schematic it is 47k/2W. It’s the same value as in most 60′s Hiwatt preamp boards, 70′s models and SAP have 22k/2W
- R17 on Mr. Huss schematic is 220k – typical value in most of Hiwatt preamp boards. It looks more like 100k on JP model internal pictures, but it’s too blurry to be sure
- R13 on Mark’s schematic shows 100k, but it looks more like 220k in JP internals. Both values are “historical correct”
- R25 looks to me like 470k really
- R24… I’m not sure, but looks nothing like 1M, more like 1M8
- C4… This is one is tuft! Usually this cap is a part of dual section can capacitor (would be in pair with C5 on my layout). On JP pictures can cap is still dual section, so I may have an error here. Honestly I don’t know. It’s correct to Mark Huss schematic as is, and I’ve wired it like this as there were no other e-caps in Mark schematic. At first I was thinking it might be missing cathode bypass cap (C3) in higher value (it can be anything from none, up to 330uF in some Marshalls – affects both tone and gain), but C4 location is far away from R15 resistor. We may never know, I’ll leave it as is – mainly because it true to Mark Huss schematic, and this is all we have folks
- R6 (a and b) and C2 junction is fun! It looks like someone – not Mr. Reeves, that kind of crappy look is not his style – was too lazy to desolder R6a, to change value from stock 100k to 47k. So what was done is C2 cap was desoldered at one end and connected to new value resistor connected on other end to ground. Old R6/100k resistor is out of circuit, dummy resistor, has no connection to anything apart of that is grounded on one end. Easy, quick mod with crappy appearance. Mark’s schematic shows 100k in this location
- the same thing could happen around R5/C12/V4a grid junction, something fishy was done around there, but I can’t figure out what. What I did is I draw that part to look like in JP picture I had staying true to Mark Huss schematic
Confused? Welcome to the club! I kept Layout/schematic component values true to Mark Huss schematic, as all above is what I deducted from really crappy picture, or simply suspicions – keep it in mind
I will leave it like this, and won’t do full amp layout because of two main reasons. Firstly, because as Mark Huss told me, David Reeves was making his amps as much modular as possible. This means you could use standard DR103 PA part, and PS and you’ll be done (one exception, choke was used in place of typical resistor alignment in Hiwatts, and possibly Marshall OT was used – doesn’t looks very Hiwatt-ish after all). Secondly – if you don’t know how to compete without draw of PS and PA – you shouldn’t do it at all
Have fun

[ampgeek]

Sweet work!
Thank you very much for doing that and sharing it here!!
Sincerely,
Dave O.

[Colossal]

Thanks very much! Great work! I thoroughly enjoyed seeing Page play Ramble On through his personal custom Hiwatt in It Might Get Loud.

[Turret]

My pleasure guys, I have much more amp layouts - replicas and my own takeoff's

I'm quite shy to post them, as I still knows little related to tubes. But I'm learning fast

BTW, one error - Input jacks has no ground reference, I forgot to correct it

[ampgeek]

Don't be shy friend!

It is obvious that you already know the winning formula here (and...are probably seeing a loosing one in action with the Airbloom threads). Be polite, post/discuss/share relevent topics and...have some fun!

And...don't have too thin a skin. While I don't believe that there are many (if any at all) truly mean or rude people here, the occasional joke or needling are usually meant in good spirit and shouldn't be taken personally.

Thanks again,
Dave O.

[Turret]

It's not quite modesty what stops me, but possible killing potential of my layouts

And no worries - usually I stay away from drama treads.

This forum is great, I'll try to be worthy to be a part of your community

Anyway - SAP CP-103 "The Who" layout coming up later today

[mhuss]

hi torg,

Sorry to be the bearer of bad news, but you used an out-of-date schematic. I'm not the best at updating my websites. Check out the current schematic, up there now:
http://hiwatt.org/Schematics/DR_Pre2InputJP.pdf

In particular, the "loose" cap you are referring to is actually connected. The two caps and a 470k resistor make a "tripod" at that location. I'm pretty sure all the values are correct now in the current schematic.

--mark

[Turret]

Hi Mark,

Your schematic was just a base for me. I did number of changes after looking on the guts of JP amp found online. I'll check your notes, look on the guts again, and report back in couple of days - I'm on vacations right now

[homenote]

Thanks very much! Great work! I thoroughly enjoyed seeing Page play Ramble On through his personal custom Hiwatt in It Might Get Loud.

I know the HIWATT was 'lit up' (on) but unless he was doin a slave thang, I'm pretty sure that he was playing , his number 1, threw the 'Vintage Marshall'.

Look a little closer (@ 0:03). http://www.youtube.com/watch?v=4gDsbOraiqg Classic Page 'mis direction'. lol

[rooster]

Mark, wow, that is the craziest preamp I have seen in quite a while. The tone stack is something I have to try and I am not clear on the PI construction. Is this typical HiWatt? Does it have a name?

Yes, I am very naïve regarding the HiWatt amp!

Torg, I appreciate your work, looking forward to seeing your revamped build drawing when you complete it.

[Turret]

Guys, just to let you know, I'm back on it.

Any info, historical and technical (specially from you Mark) will be appreciated

Transformer/Choke spec, or anything you have, bring it on

Right now I'm doing full schematic with PA and PS sections, all based on M.Huss schematic, credits naturally will be given

[Colossal]

I know the HIWATT was 'lit up' (on) but unless he was doin a slave thang, I'm pretty sure that he was playing , his number 1, threw the 'Vintage Marshall'.

Look a little closer (@ 0:03). http://www.youtube.com/watch?v=4gDsbOraiqg Classic Page 'mis direction'. lol

Yep, sure does look like he adjusts the Marshall

[JazzGuitarGimp]

He's bbbbbbbbbbbaaaaaaaaaaaccccccccccckkkkkkkk...

[dipstick10]

Thanks very much! Great work! I thoroughly enjoyed seeing Page play Ramble On through his personal custom Hiwatt in It Might Get Loud.

I know the HIWATT was 'lit up' (on) but unless he was doin a slave thang, I'm pretty sure that he was playing , his number 1, threw the 'Vintage Marshall'.

Look a little closer (@ 0:03). http://www.youtube.com/watch?v=4gDsbOraiqg Classic Page 'mis direction'. lol

I know I am late on this conversation by maybe a couple years but it looks like Jimmy is playing through the Hiwatt. There is no plug into any of the inputs on the Marshall, it can seen @ 2 minute mark in ramble on clip. Its harder to see but the Hiwatt head does appear to be plugged into the input on left side.

Anyway I love the sound of those old hiwatt amps. I've never played one yet but i'm obsessed with owning one or maybe two.

[gingertube]

Mark, wow, that is the craziest preamp I have seen in quite a while. The tone stack is something I have to try and I am not clear on the PI construction. Is this typical HiWatt? Does it have a name?

.

Yes,
That tonestack is very typical HiWatt, it is one of the things which defined the HiWatt sound. It is less interactive than the typical FVM (Fender Vox Marshall) tonestack and only cost 1 extra component. It is known in the industry as, would you believe it?, the "HiWatt Tone Stack".

The PI is actually fairly standard with the exception that its DC bias point for the PI triode grids is established by a cathode follower with just a voltage divider on it's grid setting the DC level at the cathode, rather than the PI being self biased. That is typical HiWatt too.

The other "typical" HiWatt thing is the Presence Control which is more of a Tilt Style Tone Control (Highs Cut and Boost) rather than just a High Boost by cutting feedback at high frequencies which is the more normal Fender/Marshall/etc. Presence control.

Now a question of my own, that balanced XLR socket shown on the schematic.. I take it that is an output to connect a slave amp, not an input. Is that right?

Cheers,
Ian

Edit: Oh there is one other thing typical to HiWatt, and that is its superior build standard, Military Standards influence on tag boards and wiring looms. Heat Shielding Plates behind the Output Tubes etc.