ruffrecords

Re: Poor Man's Tube Mixer
« Reply #140 on: March 27, 2020, 07:14:29 PM »
Quick update. Power supply rear panel from Schaeffer has arrived. PSU nearly complete. Pics to follow.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


ruffrecords

Re: Poor Man's Tube Mixer
« Reply #141 on: March 31, 2020, 05:25:42 PM »
As promised a pic of the completed power supply:



and its rear panel courtesy of Schaeffer:



Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

scott2000

Re: Poor Man's Tube Mixer
« Reply #142 on: March 31, 2020, 06:13:38 PM »
Sharp!

BluegrassDan

Re: Poor Man's Tube Mixer
« Reply #143 on: March 31, 2020, 09:13:56 PM »
Looks good, Ian. I like those cases for external PSUs.

ruffrecords

Re: Poor Man's Tube Mixer
« Reply #144 on: April 01, 2020, 04:57:28 AM »
Looks good, Ian. I like those cases for external PSUs.

It is a standard one from modushop in Italy:

https://modushop.biz/site/index.php?route=product/product&path=117&product_id=431

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

BluegrassDan

Re: Poor Man's Tube Mixer
« Reply #145 on: April 01, 2020, 04:44:15 PM »
Did you send the panel to Schaeffer, or did they just make a new one to specs?

ruffrecords

Re: Poor Man's Tube Mixer
« Reply #146 on: April 01, 2020, 04:56:09 PM »
Did you send the panel to Schaeffer, or did they just make a new one to specs?
They made one from scratch. Modushop provide dxf files of their cases so it is easy to draw up a panel.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

ruffrecords

Re: Poor Man's Tube Mixer
« Reply #147 on: April 01, 2020, 06:09:07 PM »
I now have the three main components; front panel, main board and rear panel, set up on the bench ready to start wiring it all together.



Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

ruffrecords

Re: Poor Man's Tube Mixer
« Reply #148 on: May 04, 2020, 01:37:10 PM »
For some time I have not been enamoured of the off the shelf enclosure I chose for this project. It is a nice shape and is reasonably priced but..... the large main board on the floor is wired to the rear panel and also to the front panel. The more I get through wiring these three together the greater the maze of wires. I really am not looking forward to trying the wiggle these three big components into the enclosure whilst ensuring none of the cables gets too close to a tube. And I really don't fancy taking it apart again if something goes wrong.

The 'Neat Enclosure' thread I started back in mid February suggests I was not really happy with the current enclosure more than two months ago. Fortunately, KidS|quid in that thread has come up with some good ideas which make the whole thing look a lot more like a small mixer and could simplify assembly considerably. So as of now I am putting the whole project on hold whilst I resolve this issue.

I will keep you all posted.

Cheers

ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Poor Man's Tube Mixer
« Reply #149 on: May 26, 2020, 09:37:10 PM »
Amazing!
If you are curious, you'll find the puzzles around you. If you are determined, you will solve them.
Erno Rubik


ruffrecords

Re: Poor Man's Tube Mixer
« Reply #150 on: May 27, 2020, 08:00:50 AM »
To whet your appetite, here is a pic of a lash up I put together the other weekend just to get a feel for what it will look like:



Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Poor Man's Tube Mixer
« Reply #151 on: May 28, 2020, 05:26:35 PM »
Beautiful Ian, I hope I one day can build a small tube mixer for my studio.

Quick question (might be answered somewhere else, sorry if so): what ht voltage does the TLA expect? I am playing with the idea of adding one of these boards on the input side of the DAOC I'm building to use it for input gain (so I can use trimmers in place of the pot meters in the compressor circuit to accurately match gain between channels) and was wondering if I could use the transformer I'm using (250ac secondaries + 9v for the heaters)


Se orry if I'm off topic, and looking forward to the continuation of the thread!

ruffrecords

Re: Poor Man's Tube Mixer
« Reply #152 on: May 28, 2020, 05:41:01 PM »
Beautiful Ian, I hope I one day can build a small tube mixer for my studio.

Quick question (might be answered somewhere else, sorry if so): what ht voltage does the TLA expect? I am playing with the idea of adding one of these boards on the input side of the DAOC I'm building to use it for input gain (so I can use trimmers in place of the pot meters in the compressor circuit to accurately match gain between channels) and was wondering if I could use the transformer I'm using (250ac secondaries + 9v for the heaters)

The TLA will work on any HT voltage from 250V to over 300V. It requires 12V heaters, preferably DC.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Poor Man's Tube Mixer
« Reply #153 on: June 30, 2020, 01:52:10 PM »
Hey Ian, thanks for your reply.

I am building a D-AOC as my first tube project. I've been at it for a while and the compressor is basically ready for first fire-up very soon.

Many people over in the D-AOC thread is noting that that the compressor needs to be driven at quite high levels to compress, altough using higher ratio input transformers and back to back vactrols lower the threshold. I am using lundahl 1540's on the input in a 1:1 ratio so I think I might benefit from some gain on the inputs, and rather use the input controls on the d-aoc for calibration of the stereo signals. So I've been tinkering with the idea of adding a TLA to the input of the compressor and am curious as to how feasable the idea is.

I don't know if you're familiar with the D-AOC design, here's the schems:

http://www.silentarts.de/DIY/D-AOC/D-AOC_Schematic.pdf

and board overlay:

http://www.silentarts.de/DIY//D-AOC/D-AOC_PCB-Overlay.pdf

My power transformer has 250V (0.1A) + 9V (2.5A) + 24V (0.5A) secondaries. I'm not sure of the current draw of the circuit, and am wondering if the transformer has enough B+ and Heater current to drive the additional TLA with the D-AOC psu (as you state in your documents this should be no more than another 15mA B+ or thereabouts configured as a line driver?). The B+ PSU form the D-AOC is the same as the GYRAF HT supply, don't know if you're familiar.

I see the TLA wants an elevated heater and minimum 250V B+. Here's some voltages from a working D-AOC:

https://groupdiy.com/index.php?topic=26585.msg330048#msg330048

Could I take the B+ from say before R128 and use it for the TLA? I presume that this is a little over 250V. For the elevated heaters, could I make a circuit as in your HT250 schematic, with a voltage divider from the B+ (again from the same place, just before r128) using 2x33k 2w(in paralell? r4 in HT250 schems) to a 22k 2W (r5 in HT250) with a 100uf cap (C5 in HT250) from the elevated heater to ground. I see this voltage divider also is used as a bleed resistor for the B+ when the unit is turned off, wondering if this will eat too much current for the power transformer, if there are other resistors in the D-AOC that acts as bleed resistors?

Could I use the lundahl 1540's directly to the TLA, and go unbalanced from the TLA to the D-AOC?


Lots of questions, I hope I don't derail the thread but I've beenr reading up on all your wonderful documentation and got curious.

Thanks for any input and all the best,
Magnus

ruffrecords

Re: Poor Man's Tube Mixer
« Reply #154 on: June 30, 2020, 07:07:54 PM »
Looking at the D-AOC schematic you posted I see that immediately after the Vactrol gain cell there is a 20dB amplifier. This then feeds the side chain triode which probably has another 20dB of gain. This should be plenty of gain to ensure the gain cell  compresses.  The VTL5C4 only needs 1mA of current to drop its resistance to 1K2 which should give plenty of gain reduction with R102 at 8K2.

One reason it may not be working properly is that the Vactrol LED really needs another LED across it wired in opposite polarity. A red LED will do fine. Otherwise the circuit acts as a charge pump. I believe this is a well known flaw in this design.

Cheers

Ian

Adding a TLA at the input would increase the gain and lower the threshold but also raise the noise. I
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Poor Man's Tube Mixer
« Reply #155 on: June 30, 2020, 08:12:24 PM »
The stock build uses vtl5c4/2 plus a resistor as you say, the way I'm setting it up is with two vactrols pr channels, one reversed so will act as the led with opposite polarity (Kubi mod). Some builders say they needed the input and makeup-gain in order to trim the compressor channels to each other, and that 1:1 ratio on the transformer is too low for the gain available on the input of the compressor to hit the vactrols with a wide variety of input levels.

I'm sure I'll have a better picture of it all when it's built up  8)

Best,


 

Related Topics

  Subject / Started by Replies Last post
8 Replies
4773 Views
Last post July 07, 2008, 11:56:08 AM
by bodega
281 Replies
70076 Views
Last post May 24, 2016, 05:53:20 PM
by ruffrecords
116 Replies
49463 Views
Last post March 16, 2018, 08:50:51 AM
by ruffrecords
61 Replies
23305 Views
Last post January 24, 2015, 07:34:34 PM
by ruffrecords