Huss style 6v6 Plexi

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?

Post by **zaphod_phil** » Sat 05/12/07 6:04 pm

Sure, that would also work fine. Like I said there are plenty of 1987 Plexi layouts kicking around the net.....

Post by **markh** » Sat 05/12/07 8:59 pm

I recently built a 4 x 6V6 high gain amp (Soldano-ish preamp) that sounds killer. I love the 6V6, it's a great little tube AND there are still NOS deals to be found.

--mark

redwood · Post by **redwood** » Sat 05/12/07 9:27 pm

redwood wrote: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?

Built this way it's gonna be running a bit hot ,probably about 430v.Thats a bit much for NOS tubes isn't it?I was thinkin new JJ's would be in order.What do you suggest Mark?

Bulatovic · Post by **Bulatovic** » Sat 05/12/07 10:14 pm

if voltages are high on 6v6s is it possible just to add a couple of zenners like 30V or so to get the voltage down a bit? Isn't 430 a bit too much close to the JJ 6V6's maximum of 450?

Thanks

redwood · Post by **redwood** » Sat 05/12/07 10:22 pm

I think Mark was running right at 435 on his 6v6 plexi,its up there though.

phsyconoodler · Post by **phsyconoodler** » Sat 05/12/07 11:50 pm

Just use good 6V6GT's and the voltage is not a problem.If the amp is set up for EL34's the 6V6's sound a little different with 1k screen resistors and 5.6k grid stoppers.But leave them alone so you can pop in EL34's if you want.The volume level will not be dramatically different.I prefer EL34's overall to 6V6's but there is something about 6V6's that sound better with single coils.I find that I don't have to change anything to get the bias right.Just use a 50k bias adjust pot.

martinw · Post by **martinw** » Sun 05/13/07 5:12 am

My 6V6 October (very similar to the Huss Plexi) runs lower B+ (around 390 IIRC) and sounds truly wonderful.
Maybe I lose a little volume and headroom? Not really an issue to me.
I do like having the "Ali" option on the October though. Worth considering for the sake of a switch and a couple of components.
Check it out: 6V6 October

Fredaxis · Post by **Fredaxis** » Sun 05/13/07 5:13 pm

Very nice October Martin

Waiting for my chassis, I prepared some other parts today, and found on the web the schematic of the Motorola console from which I got the PT and OT.

Let's go for the newby questions

- The schem tells the voltage right after the 5y3 is 320V. From that I guess the PT is about 290/0/290, that should give me about 400V on the plate with the SS rectification. Am I right with the math?

- The heater side of the PT is not center taped, Guess I'll go with the 100k/100K pseudo center?

- On Mark's schem, there is a 470nF cap in parallel with the 1st PSU 50uF cap. What is the purpose?

- My chassis has room for 3 cap can, I end up with one more 50uF section than needed. Would it worth to parallel the 2 sections of the 1st one in the PSU to make it 100uF as in the 1987?

Thanks in advance for your answers

Bulatovic · Post by **Bulatovic** » Sun 05/13/07 5:53 pm

No, you want 100R for an artificial center tap.

Fredaxis · Post by **Fredaxis** » Sun 05/13/07 5:56 pm

Ouch!! You are right! typo, thanks for correcting

Fredaxis · Post by **Fredaxis** » Mon 05/14/07 8:20 am

Anyone on my voltage and caps?

morcey2 · Post by **morcey2** » Mon 05/14/07 8:34 am

Fred,

On the can caps, paralleling one to give you a 100u cap would be good. With the 290-0-290, you'll probably end up with just under 400V under load. The tranny I have for mine is 300-0-300, so it will be awefully close to what you've got.

As for the 470n cap in the PSU, I think that's to better filter some of the higher frequencies that the electrolytic caps don't do as well, but that's just a guess.

Matt

Fredaxis · Post by **Fredaxis** » Mon 05/14/07 8:56 am

Thanks a lot Matt.

So it is a go for the 100uF.

290/0/290 is only a guess I made based on the 320V with the 5y3 in the circuit. Anyway, about 400v should be OK for the plexi.

Thanks for the idea on the 470n. Mark is asking for a metal film here. He will may be confirm.

martinw · Post by **martinw** » Mon 05/14/07 9:09 am

Fredaxis wrote:Very nice October Martin

Merci!

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Huss style 6v6 Plexi