Huss style 6v6 Plexi

redwood · Post by **redwood** » Tue 05/08/07 8:54 pm

Who has the "best" finalized schematic for this November variation,is it the one on the ax84 site done by Mark?Great site by the way,I'm learning more day by day,very interesting stuff.I may be slow but I'm determined.Thanks for any imput.

BBQLS1 · Post by **BBQLS1** » Tue 05/08/07 8:59 pm

Is this what you are looking for?

http://www.mhuss.com/tindex.html

morcey2 · Post by **morcey2** » Tue 05/08/07 9:09 pm

Just remember that on the schematic, the inputs aren't hooked up correctly. If you plug into the 'II' input, there is no ground reference. Mark said that this was because he has it hard-wired jumpered so it was never an issue.

I plan on building one shortly, but will have a little lower B+ because of the tranny I'm using(272FX). If you do happen to build it before I do, make sure you keep us posted.

ZP has played one and says it's one of the best sounding amps he's ever played. Search around and you'll find his commentary.

Matt.

redwood · Post by **redwood** » Tue 05/08/07 9:12 pm

Yeah I saw that ,is that the working version people are building from or are there revisions and improvements after that?Thanks for the input it's appreciated.I may not know much but I know what sounds good to me and that does any other suggestions to listen to?

Post by **zaphod_phil** » Wed 05/09/07 5:22 am

Yes, that's the schematic everyone's working from. As it's pretty close to a regular Marshall 1987 Plexi, there are plenty of layouts around.

redwood · Post by **redwood** » Wed 05/09/07 5:43 am

Phil,do you have any other suggested layouts that I could use to cross reference as I'm more than a bit ignorant

when it comes to this sort of project.Anyone else feel free to interject your suggestions as well please.

Fredaxis · Post by **Fredaxis** » Wed 05/09/07 9:24 pm

Hello Redwood,
I am myself rightnow buying all my components to build my MH 6V6 Plexi in a near future.
Here is a 1987 Layout that you can use for cross reference.
Keep in mind that it is using EL34, so tube pin-out as well as some components are different.
http://www.ceriatone.com/images/layoutP ... iatone.jpg
For everything onboard keep Mark's layout values.
The Ceriatone Layout may help you on the way you will wire everything around the board (same as before, be carefull with tube pin-out and component values)
Hope this helps.

tallkien · Post by **tallkien** » Thu 05/10/07 1:04 am

Fredaxis,

Do you have Transformer and choke specs for that amp?

Fredaxis · Post by **Fredaxis** » Thu 05/10/07 5:44 am

Hi Tallkien,
According to Mark Huss, on his web site "a Hammond 272DX or 372FX power transformer, and a Hammond 1650E output transformer will work fine."
http://mhuss.com/Plexi6V6/index.html

I bought this choke on ebay: http://cgi.ebay.com/Dynaco-C354-Choke-R ... dZViewItem

I am using the transformers from a 6V6 Motorola console, I may end up with a high B+, as the console was rectified with a 5Y3, good opportunity to try the zener trick and adjust it to what I want.

redwood · Post by **redwood** » Thu 05/10/07 5:53 am

Fredaxis,Thanks for you reply.Are you going to keep the same controls as the 1987.TMB Presence Bright Normal? What are you going to to do about the 2nd channel how are you going to split up the controls or are you keeping it one channel.Thanks

pmurph1x · Post by **pmurph1x** » Thu 05/10/07 8:12 am

Fredaxis wrote:
Here is a 1987 Layout that you can use for cross reference.
Keep in mind that it is using EL34, so tube pin-out as well as some components are different.
............................

The Ceriatone Layout may help you on the way you will wire everything around the board (same as before, be carefull with tube pin-out and component values)
Hope this helps.

Hi Fredaxis
I think (hope

) that 6v6 and EL34 have the same pinouts right? I just built a 2204 with 6v6's without changing the pinouts from the EL34 version and it does make sound. There are some issues with my build but I dont think they are with the poweramp section.

FYI: I referenced these layouts:

http://www.dreamtone.org/NEW2204LayoutS ... amTone.pdf
http://homepage.mac.com/gaden/.Public/6 ... Layout.pdf
http://homepage.mac.com/gaden/.Public/2 ... Layout.pdf

Paul

morcey2 · Post by **morcey2** » Thu 05/10/07 8:25 am

For fixed biased amps, as long as pins 1 & 8 are tied together, both EL34 and 6v6 will work. For cathode biased amps, pin 1 should be grounded for better suppressor grid function in the EL34, but since the 6v6 has no connection on that pin, it will still work. In fact most of the standard octal power tubes (6L6, KT*, 6550, etc) will work with that.

Matt

Bulatovic · Post by **Bulatovic** » Thu 05/10/07 9:28 am

So in every fixed bias amp EL34 (or KT66 or similar) can be directly swapped with a 6V6 without any circuit changes, just to bias them correctly right (thinking JCM800 2204)?

(please don't laugh about my question now as i have never dealt with 6v6 valves) I have bought a JJ 6V6s from HotRox UK and it has the 6th pin taken out :S Is that normal - i've seen that anyway that 6th pin on 6v6 amps doesn't go anywhere, just i didn't know that they take it out (or do they - or my valve is broken - it has been tested according to them)

Thanks

morcey2 · Post by **morcey2** » Thu 05/10/07 10:04 am

Bulatovic wrote:So in every fixed bias amp EL34 (or KT66 or similar) can be directly swapped with a 6V6 without any circuit changes, just to bias them correctly right (thinking JCM800 2204)?

(please don't laugh about my question now as i have never dealt with 6v6 valves) I have bought a JJ 6V6s from HotRox UK and it has the 6th pin taken out :S Is that normal - i've seen that anyway that 6th pin on 6v6 amps doesn't go anywhere, just i didn't know that they take it out (or do they - or my valve is broken - it has been tested according to them)

Thanks

The easy question first. It's not uncommon to have pin 6 missing on most of these tubes because it's not connected to anything. The tubes that have it there, it's still disconnected so there is really no difference.

There are a couple of changes that would need to happen. The bias supply might not have the right range for a specific tube type, so that might have to be changed. Also, EL34/KT77/6CA7 like a much lower output impedance than a 6V6, 6L6, or KT66 et al. On most of the marshalls, EL34s have a 3.4k tranny, while the KT66s (JTM45) have an 8K tranny. The 6V6 should be happy with anything from 6.5K up to about 9K. Another issue is whether the 6V6 would handle the plate voltage. The JJs should have no problem, but there are others that don't like the higher voltages.

Matt.

Bulatovic · Post by **Bulatovic** » Thu 05/10/07 10:19 am

If i use JJ 6V6s for that, except changing the primary on the OT (if OT is multiprimary? it can be done on a switch el34/6v6, or can it?) and what are the voltages on plates - i mean, would biasing be possible for a 6v6?

If I am not wrong - JCM800 gets all the distorsion and "rock sound" from the preamp isn't it - it has the master volume, so by how much would it be different when driving it with a pair of 6V6s while cranked compared to el34 with lower master but higher preamp volume ?

Thanks a lot!

Alexo · Post by **Alexo** » Thu 05/10/07 10:21 am

Another issue is whether the 6V6 would handle the plate voltage. The JJs should have no problem, but there are others that don't like the higher voltages.

Beat me to it. On the MHuss schematic, I think the plates are at 435 or so. I'm beginning to think that the 400+ range is a really sweet spot for 6V6's, at least in fixed bias, they just sound awesome up there to my ears, but you need good NOS or JJ's.

Alexo · Post by **Alexo** » Thu 05/10/07 10:31 am

Bulatovic wrote:If i use JJ 6V6s for that, except changing the primary on the OT (if OT is multiprimary? it can be done on a switch el34/6v6, or can it?) and what are the voltages on plates - i mean, would biasing be possible for a 6v6?

You will probably need to adjust the voltage divider in the bias network to get more range if you want to be able to run either tube, on the MH schem, that would be the 47K and 15K before the bias pot. I've had to just go by trial and error to find a usable range, it's really not that hard, just be sure when you first power it up to err on the side of too much negative voltage, it is much better to have the tubes power up too cold and have to warm them up than to have them start up too hot and explode, which maybe wouldn't really happen but I like to play it safe.

MOst OT's are not multi-primary, but that is OK, you just need a multi-secondary OT, which most OT's designed for "head" style amps are. If you set the output to 16 ohms and plug it into an 8 ohm cab, you willhalve the primary impedance, set it for 4 and plug into 8 and you will double it.

Fredaxis · Post by **Fredaxis** » Thu 05/10/07 5:20 pm

redwood wrote:Fredaxis,Thanks for you reply.Are you going to keep the same controls as the 1987.TMB Presence Bright Normal? What are you going to to do about the 2nd channel how are you going to split up the controls or are you keeping it one channel.Thanks

Yes, I keep the same control as a real 1987 as I will be using a Marshall like chassis. (Modified alu JTM 45 Ceriatone Chassis).
As it is a Plexi, you want to keep both channels in order to jumper them.
You can do it the old way, with a jumper going from Low input of bright channel to High input of the normal channel, or going the way Mark did on his amp, with an internal jump.
You could also use only one input jack and wire a 3position switch that woud give you one channel, the other or both.

Fredaxis · Post by **Fredaxis** » Thu 05/10/07 5:24 pm

pmurph1x wrote:
Fredaxis wrote:
Here is a 1987 Layout that you can use for cross reference.
Keep in mind that it is using EL34, so tube pin-out as well as some components are different.
............................

The Ceriatone Layout may help you on the way you will wire everything around the board (same as before, be carefull with tube pin-out and component values)
Hope this helps.

Hi Fredaxis
I think (hope ) that 6v6 and EL34 have the same pinouts right? I just built a 2204 with 6v6's without changing the pinouts from the EL34 version and it does make sound. There are some issues with my build but I dont think they are with the poweramp section.

FYI: I referenced these layouts:

http://www.dreamtone.org/NEW2204LayoutS ... amTone.pdf
http://homepage.mac.com/gaden/.Public/6 ... Layout.pdf
http://homepage.mac.com/gaden/.Public/2 ... Layout.pdf

Paul

Morcey2 gave a much better explanation than what I could have given

Thanks Morcey!

redwood · Post by **redwood** » Sat 05/12/07 1:04 pm

Is there any reason not to take the ceriatone layout for the 1987 and use it but with 6v6's in place of the el34's? for this amp?Will you still get the sparklingshimmeryliquid clears and layers and layers of rich creamy harmonics?

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Huss style 6v6 Plexi

Huss style 6v6 Plexi