Feeler: EZ Tube Lunch Box

[G-Sun]

Then I need to decide in what steps and configuration I'll do my dual strip.

I did think rack, psu and pre1 first, then eq1 and comp 1, the strip 2. with transformer insert.

But, I need to look at what final cost will be doing it in steps vs. all at once.

The I could skip the insert transformers.
Is it possible for the preamp to have a separate gain-switch for the line in?
That would make my workflow easier.

Another thing to consider is doing both channels at the same time.
As it's less work and easier to troubleshoot.

If doing everything at once however it might take me a long time to get any sound from the box.

And I need to get an idea about budget for the various modules.
The pulteq eq is 121pounds it seems, one channel. Should I estimate the other modules to be in the same ballpark?
A little less for the psu?

 

[ruffrecords]

Obviously you need the rack and PSU before you can do much else.

Then you can build pre 1. Fit an output transformer to the back of the rack and connect it to out1 and you have a basic mic pre. That way you get some sound from the box early on.

Since your EQ is always going to be associated with a specific mic pre, you might like to think about building the two in a single double width module. The 3U EQ boards are only 100mm deep and do not have the 32 way connector. It therefore makes sense to wire them directly to the mic pre board. This will probably lead to there being a little more front panel real estate available which would be handy for the Pultec.

Having said that, I do remember you asking about having the gain make up amp with the EQ. As I mentioned the problem is the heater voltage. There are plenty of 12V heater double tirodes but none has the drive capability of the 6922. They all produce too much distortion when driving a load. Despite that I am tempted to do a 3U EQ PCB layout with an input transformer and gain make up amplifier and 32 way connector all on one PCB. The gain make up part could not be used but the input transformer would be just what you need for the insert return and the 32 way connector would make wiring a lot simpler and the EQ would be a discrete module in its own right.  In your case, the EQ will eventually feed the comp so the gain make up amp does not need any serious drive capability. This means you might possibly be able to use a regular 12V heater tube for the gain make up amp. I need to think about this some more.

I am afraid it is not possible to have a separate gain control for the line in.

I am sure you found these BOMs for the Heios and pultec EQs:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/PultecHeliosBOMs.pdf

and here is a BOM for the Eurochannel:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/EurochannelBOMcost.pdf

although the transformer cost is a little out of date now.



Cheers

ian

 

[rmaier]

I've just started sourcing parts for a build that will include 4 Classic preamp boards and separate PSU. I could use a bit of advice selecting toroids (always the most arcane part of any build for me, I have to confess). I would have liked to use the same one from antek as I used in my Poshman EQ, but it's out of stock:

http://www.antekinc.com/as-05t240-50va-240v-transformer/

Can I use this instead? http://www.antekinc.com/as-1t230-100va-230v-transformer/

For phantom, how about this (secondaries wired in series)? http://www.antekinc.com/as-0522-50va-22v-transformer/

Thanks!
Ralph

 

[ruffrecords]

Hi Ralph,

The Antek you mention should be fine.  Bit of an overkill but it will work.

The dual 22V will probably be OK for the phantom. Again, at 50VA it is a bit overkill but the 22V is a bit low. Allowing 10% regulation then this transformer will probably output 24V with light loads like phantom power so it should be OK. You only need a few VA for phantom. I would use something like this:

http://uk.farnell.com/multicomp/mcfe015-25/transformer-15va-2-x-25v/dp/9531696

but it is no good for you as it has a single 230V primary.

Cheers

Ian

 

[rmaier]

Thanks, Ian.
Maybe this one for Phantom?

http://www.antekinc.com/an-0225-25va-25v-transformer/

Or something smaller:

http://www.antekinc.com/an-0124-10va-24v-transformer/

 

[ruffrecords]

Thanks, Ian.
Maybe this one for Phantom?

http://www.antekinc.com/an-0225-25va-25v-transformer/

Or something smaller:

http://www.antekinc.com/an-0124-10va-24v-transformer/

Either of those two will be fine.

Cheers

Ian

 

[G-Sun]

Thanks!

Then you can build pre 1. Fit an output transformer to the back of the rack and connect it to out1 and you have a basic mic pre. That way you get some sound from the box early on.

Yes, that's a start

Since your EQ is always going to be associated with a specific mic pre, you might like to think about building the two in a single double width module. The 3U EQ boards are only 100mm deep and do not have the 32 way connector. It therefore makes sense to wire them directly to the mic pre board. This will probably lead to there being a little more front panel real estate available which would be handy for the Pultec.

Yes, it makes sence thinking this way.
Putting an insert there feels a little backwards, but is of course an option.

Having said that, I do remember you asking about having the gain make up amp with the EQ. As I mentioned the problem is the heater voltage. There are plenty of 12V heater double tirodes but none has the drive capability of the 6922. They all produce too much distortion when driving a load. Despite that I am tempted to do a 3U EQ PCB layout with an input transformer and gain make up amplifier and 32 way connector all on one PCB. The gain make up part could not be used but the input transformer would be just what you need for the insert return and the 32 way connector would make wiring a lot simpler and the EQ would be a discrete module in its own right.  In your case, the EQ will eventually feed the comp so the gain make up amp does not need any serious drive capability. This means you might possibly be able to use a regular 12V heater tube for the gain make up amp. I need to think about this some more.

This is more like my vision. I couldn't understand why the tube module from the Eurocard couldn't be moved over to the  Pulteq card. It's the same voltages available isn't it?
Anyway, for me, if the drive is ok for the feeding the comp, then I'm fine.

I am afraid it is not possible to have a separate gain control for the line in.

Ok

I am sure you found these BOMs for the Heios and pultec EQs:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/PultecHeliosBOMs.pdf

and here is a BOM for the Eurochannel:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/EurochannelBOMcost.pdf

although the transformer cost is a little out of date now.

Thanks!
I was a little unsure about the Eurcard bom as it seemed for the 6U version.

 

[ruffrecords]

I couldn't understand why the tube module from the Eurocard couldn't be moved over to the  Pulteq card. It's the same voltages available isn't it?

The Eurocard has three tubes on it. two of them have their heaters wired in series so they can be powered from 12V. You only need one of them for the gain make up so you need a 6V heater supply which we don't have.

Cheers

Ian

 

[G-Sun]

The Eurocard has three tubes on it. two of them have their heaters wired in series so they can be powered from 12V. You only need one of them for the gain make up so you need a 6V heater supply which we don't have.

Ok, I see

 

[rmaier]

I have a few more questions while sourcing parts. I've read through the thread a few times but I'm still unclear on a few things (trying to avoid the multiple mouser orders due to my own screw-ups that seem to have  become the norm for pretty much any project I've done to date).

Regarding the gain pot, does the Classic want the same 47K/50K rev log as seen in the EZ?

If I make up a 12 pos Lorlin or Alpha, can I base my steps on those outlined in your EZTubeMixer3AssyNotes pdf (range 430r-150K), or should I calculate new values for a 47K/50K rev log switch. Part of my confusion is due to the fact that the Classic, when cascaded, puts out more gain.

Regarding the PSU, can BR3 GBU802 be 200V?

Is this suitable for the IC2 update?
http://ca.mouser.com/Search/ProductDetail.aspx?R=LD1084Vvirtualkey51120000virtualkey511-LD1084V

Finally,  C13 is now 22uF 63V, right?

Thanks!
Ralph

 

[ruffrecords]

I have a few more questions while sourcing parts. I've read through the thread a few times but I'm still unclear on a few things (trying to avoid the multiple mouser orders due to my own screw-ups that seem to have  become the norm for pretty much any project I've done to date).

Regarding the gain pot, does the Classic want the same 47K/50K rev log as seen in the EZ?

No. the classic is just two amplification stages with a regular 10K log pot between them.

If I make up a 12 pos Lorlin or Alpha, can I base my steps on those outlined in your EZTubeMixer3AssyNotes pdf (range 430r-150K), or should I calculate new values for a 47K/50K rev log switch. Part of my confusion is due to the fact that the Classic, when cascaded, puts out more gain.

See above. The classic is completely different to the Eurochannel

Regarding the PSU, can BR3 GBU802 be 200V?

Yes as long as it is rated at 8 amps continuous.

Is this suitable for the IC2 update?
http://ca.mouser.com/Search/ProductDetail.aspx?R=LD1084Vvirtualkey51120000virtualkey511-LD1084V

Yes, that's looks identical to the one I use.

Finally,  C13 is now 22uF 63V, right?

Thanks!
Ralph

C13 should be 220uF.

Cheers

Ian]

 

[ruffrecords]

A nice surprise in the post this morning - the 1H inductors for the two pot NFB EQ arrived from Banzai Music. Now I can put together a simple prototype and check it out.

Cheers

Ian

 

[G-Sun]

For the Eurocard preamp:
How much i s needed for the DI/HiZ addon?
Just a 100nF and a 470k and a jack?
Relay?
Flied jack or pcb-mount?

 

[anjing]

If you ever implement de Di option i'd be interested to know how you like it.

 

[anjing]

Ian will the classic be available in the the twin line amp configuration?

 

[ruffrecords]

For the Eurocard preamp:
How much i s needed for the DI/HiZ addon?
Just a 100nF and a 470k and a jack?
Relay?
Flied jack or pcb-mount?

You need the relay, a switch to operate it and a supply for it. You will also need a jack socket and a 470K resistor. You need to find space on your front panel to mount the socket. Wire the 470K directly across the socket. Use a screened lead from the socket the HIZ and HIZ0. Switched power for the relay needs to go to the two pads at the top of the relay. The relay can be switched with a switch or you can use contacts on the socket to switch it automatically when a jack is plugged in.

Cheers

Ian

 

[ruffrecords]

Ian will the classic be available in the the twin line amp configuration?

The classic can be configured in a number of ways. It is very similar to the twin line amp in that is has two identical amplifiers and provision for two input transformers. I recently completed a document about building and using it. I have attached a copy and I will upload it to my web pages soon.

Cheers

Ian

 

[rmaier]

Thanks very much, Ian.  This is great!
BTW, does the schematic included here take the oscillation problem into account?
Ralph

 

[ruffrecords]

Thanks very much, Ian.  This is great!
BTW, does the schematic included here take the oscillation problem into account?
Ralph

There were two oscillation problems. The more recent one turned out to be a dc heater regulator problem, now cured. Nothing to do with the tube circuits at all. The original oscillation problem occurred when several boards were powered from a single HT supply. The cure is a 100nF across the HT on the board. This mod is included in the V3 board as CHT. The V2 board does not have this mod - you just have to tack a 100nF across the HT pins on the 32way connector.

CHT and RHT are not shown on the current schematic.

Cheers

Ian

 

[anjing]

Thanks Ian, great work on the pdf! Wasnt there talk at one point to have the foot print for a carnhill input trafo?


Regards Ian,

Pierre