100W HRM in the BluesMaster Style?

mdroberts1243 · Post by **mdroberts1243** » Sun Sep 09, 2007 2:06 am

EDIT: I am going to attach the latest schematic and layout/BOM (once we have them) to this posting to keep stuff at the front of the thread.

-mark.

ORIGINAL POST:

I'm ramping up for a 100W build using Funk's chassis and board set.

I wanted a schematic that will (hopefully) be compatible with that set. It's been tough to see the big picture as the posts are detailed and fragmented.

The other theme I've got going here is the blues... I tried to pick up on anything that suggested a bluesy tone would result.

I gleaned what I could from the various posts/threads/schematics and photos to put together a (very) rough DRAFT schematic... attached. Also found the JCM800 Lead and 1959 Marshall schematics useful.

I'm hoping for lots of feedback! Some Q's and contradictions are indicated on the drawing. Still working out the details on the power supply bias and FET sheet... more to come!

Thanks in advance,

mdroberts1243 · Post by **mdroberts1243** » Sun Sep 09, 2007 11:13 pm

EDIT: Removed the schematic from this post... see the latest further down...

Hi All,
I've attached another version of the schematic... big error corrected... I completely mis-wired the 'clean' master... propagated from the non-HRM D'Lite schematic.
That is now correct (I hope) and I've added coax shield indicators, tweaked some values and added some other Q's.
In going for a bluesy tone I'm struggling with a number of issues...
1-- went for the B.B. tone stack values from AmpDoc1's spreadsheet as I couldn't stomach the big changes suggested in the BM column.
2-- stuck with the BM column suggestions of 220/150 on both tubes... but would the lower 180/120 Rps give me more Fendery/Bluesy sound???
3-- the posting "Notes snagged from 18W" suggests 5uf on all cathodes but one and leans towards 1uf on CL2... I thought this was a good idea as the OD has a tone stack to make corrections post amplification... but will the tighter(?) bass on CL2 help or hinder the Blues? Anybody know why it might be better to have the 1uf on OD2?
4-- what is the genesis of the 500pf in parallel with 220k leading up to CL2? A lot of dumble variants (in the spreadsheet) seem to use 390pf. I think this would brighten the clean sound quite a bit... anybody care to wade in on the tone effect?

chris_sanford · Post by **chris_sanford** » Mon Sep 10, 2007 12:30 am

mdroberts1243 wrote:
1-- went for the B.B. tone stack values from AmpDoc1's spreadsheet as I couldn't stomach the big changes suggested in the BM column.

Dude. It's not a BM without the BM tonestack!

47k slope, .022uf for bass and mid caps, mid pot (50k) wired as a VR *in series* with the bass pot.

mdroberts1243 wrote:
2-- stuck with the BM column suggestions of 220/150 on both tubes... but

In the 'HRM or not post', I mentioned the plate values: 150/120/220/150

HTH,

Chris

mdroberts1243 · Post by **mdroberts1243** » Mon Sep 10, 2007 1:00 am

chris_sanford wrote:
mdroberts1243 wrote:
1-- went for the B.B. tone stack values from AmpDoc1's spreadsheet as I couldn't stomach the big changes suggested in the BM column.
Dude. It's not a BM without the BM tonestack! 47k slope, .022uf for bass and mid caps, mid pot (50k) wired as a VR *in series* with the bass pot.

mdroberts1243 wrote:
2-- stuck with the BM column suggestions of 220/150 on both tubes... but
In the 'HRM or not post', I mentioned the plate values: 150/120/220/150

HTH,

Chris

Thanks Chris!
Did you and Funk work out what should be done with the rock/jazz and PAB connections that were partially explored in that thread? I can see that I could connect them as is, but wondering if there is anything else to consider.

Any thoughts on #3 and #4?

novosibir · Post by **novosibir** » Mon Sep 10, 2007 2:10 am

You shouldt have a 25K presence pot instead of the 5K

Larry

mdroberts1243 · Post by **mdroberts1243** » Mon Sep 10, 2007 2:24 am

novosibir wrote:You shouldt have a 25K presence pot instead of the 5K

Larry

Thanks Larry,
Picked that up myself after carefully re-reading the 'to HRM or not' post that Chris mentioned... I'm about to post a schematic with the suggested changes for everybody's consideration.

mdroberts1243 · Post by **mdroberts1243** » Mon Sep 10, 2007 2:34 am

Hi,
Here is yet another iteration of the schematic with the Fender-style Tone Stack as suggested by Chris.
I also went ahead and used the cathode resistors as per the AmpDoc1 spreadsheet (which happens to match Chris' Rp resistor values). The cathode resistors are weird ratios to the normal though.
Picked up a couple of other changes in the PI by carefully re-reading the 'to HRM or not' thread. Thanks DogEars!

UPDATE: Corrected a stupid error with an extraneous ground in the tone stack, sorry...

EDIT: Look for a newer schematic further on...

odourboy · Post by **odourboy** » Mon Sep 10, 2007 2:45 am

Mark,

There's a ground on your revised tonestack from the two .022uF caps that looks like it shouldn't be there. Someone else is going to have to comment on the restof the tonestack topology.

Brian

mdroberts1243 · Post by **mdroberts1243** » Mon Sep 10, 2007 2:47 am

odourboy wrote:Mark,

There's a ground on your revised tonestack from the two .022uF caps that looks like it shouldn't be there. Someone else is going to have to comment on the restof the tonestack topology.

Brian

Beat you!

I'm getting sloppy... sorry!

novosibir · Post by **novosibir** » Mon Sep 10, 2007 2:56 am

The .01 cap on OD2's plate in front of the HRM tone stack doesn't make sense to me and has to be removed entirely IMO, but I might be wrong in this respect.

One of the hard-core Dumblers still shouldt throw an eye (or two) over this schem.

Larry

mdroberts1243 · Post by **mdroberts1243** » Mon Sep 10, 2007 3:07 am

novosibir wrote:The .01 cap on OD2's plate in front of the HRM tone stack doesn't make sense to me and has to be removed entirely IMO, but I might be wrong in this respect.

One of the hard-core Dumblers still shouldt throw an eye (or two) over this schem.

Larry

The .01 cap is called out in the AmpDoc1 spreadsheet... I had it off to the side with question marks in the schematic, but I've recently re-read a thread that argued it would drop the bass a bit exiting the OD2 with a 5uF Rk (and I'm desparately trying to rationalize putting the 1uF on CL2

)

Here is the reference post by Jelle in a discusion with DogEars:

Jelle wrote: Hi scott,

I have tried the different values there as well and since I'm using a modified OD entrance network I like higher values for the bypass caps. Please note that there is a decoupling cap in these schematics that reduces bass after the plate of v2B before the signal enters the HRM stack. To prevent fartyness in the OD stages, I'm using a OD entrance that reduces bass a bit. I think it is another way to get similar results.

Hey, it works for me! I'd be very interested to see degooped pics of a HRM dumble to find out what is going on in there....

Jelle

mdroberts1243 · Post by **mdroberts1243** » Mon Sep 10, 2007 3:34 am

odourboy wrote: Someone else is going to have to comment on the restof the tonestack topology.

Brian

I tried out Chris' suggestion in the ToneStack Calculator (nice to be able to use that with a D-Clone!)... it seems to give a good range of control and variation. Plus just the association with 'Fender' gives me a bit more comfort w.r.t the Blues tones... all this Marshall influence is making me nervous.

chris_sanford · Post by **chris_sanford** » Mon Sep 10, 2007 4:06 am

mdroberts1243 wrote:
odourboy wrote: Someone else is going to have to comment on the restof the tonestack topology.

Brian
I tried out Chris' suggestion in the ToneStack Calculator (nice to be able to use that with a D-Clone!)... it seems to give a good range of control and variation. Plus just the association with 'Fender' gives me a bit more comfort w.r.t the Blues tones... all this Marshall influence is making me nervous.

Yes, finally a TS that works right with little calculator!

A couple of things.. the treble cap should be the standard .002. Some examples have 'snubbers' on the OD stages, some don't. The OD master volume pot in one example was 500k, not 1M, dunno about the others... but that seems like a good treble-boost move.

I don't know about the .01 cap before the post-od TS. The one noted on the schem was actually smaller, but I've tried various sizes there, and I personally feel that is a mistake (ymmv).

Also, I have not figured out what might be happening with the jazz/rock/PAB circuit. The LC amp appears to be different from the standard setup though. Also, another amp that I am aware of connects the .0047 lug of the jazz/rock switch directly to the PAB relay board. I have no idea why, sorry.

chris

heisthl · Post by **heisthl** » Mon Sep 10, 2007 5:52 am

I'm guessing the cathode(Rk) values are wrong on your schematic. If you have a 220kplate it gets 3k3,180-2k7,150-2k2 and 120-1k8. BWDIK.

mdroberts1243 · Post by **mdroberts1243** » Mon Sep 10, 2007 11:06 am

heisthl wrote:I'm guessing the cathode(Rk) values are wrong on your schematic. If you have a 220kplate it gets 3k3,180-2k7,150-2k2 and 120-1k8. BWDIK.

Yeah, bothers me too... I'll spend a bit more time looking at this with Chris' comment about 'biasing hotter on the front-end and cooler on the back' in mind.

The Amp Garage

100W HRM in the BluesMaster Style?

100W HRM in the BluesMaster Style?

VERY ROUGH DRAFT 2

Re: VERY ROUGH DRAFT 2

Re: VERY ROUGH DRAFT 2

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Re: 100W HRM in the BluesMaster Style?

3rd VERY ROUGH DRAFT

Re: 100W HRM in the BluesMaster Style?

Re: 100W HRM in the BluesMaster Style?

Re: 100W HRM in the BluesMaster Style?

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