TG1 - advice from any one who has built it...

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Bonsaimaster said:
Dual secondaries.

You connect the + of one of the secondaries with the - of the other.  That becomes you  centre tap which connects to ~G.  The other 2 wires connect to either side of the bridge rectifier.  Look at diagram 9 on this page.  The bridge rectifier in this instance is D1-D4.  I think either side for you is ~1 & ~25.  But not having the box in front of me to check, I suggest that you check it out with a meter.

It is quite important to make you centretap pair a + of one secondary & a - of the other.  If you don't you will get through a lot of fuses and/or possibly damage the transformer.
 
Anyone know what the minimum requirements are for the power transformer for the IGOR PSU? I am trying to fit everything in a 2U rack space. Can I use a 32V 25VAor a 30V 30VA?
 
Bonsaimaster said:
Anyone know what the minimum requirements are for the power transformer for the IGOR PSU? I am trying to fit everything in a 2U rack space. Can I use a 32V 25mA or a 30V 30ma?

30mA max current is way too less to power the unit. Do you mean 25 or 30VA instead?
 
Ok got 28V from the power supply. Looking to connect to main board and start the calibration. Will add jumpers to get 20V. Any advice after that?
 
Ok got 20V on the board with one jumper. Hope everything else goes ok. Using 1:1 Lundahl transformers on input and output and a 10k Lin pot for hold with the jumper on R115.
 
Anyone using the 1517 Lundahl transformer for output. I am trying to find the RZ and CZ for the zobel network with no luck. Unfortunately, I don't have a scope. Also in looking at the 1:1 and 1:1 bypass it states to OMIT J8 yet on the schematic it looks like it is needed.

Last stupid question. How are people powering the lamps on the VU meters.

Thanks again!
 
Got everything up and running. This is an incredible fucking compressor. OMG! Outstanding. Thanks for everyone for answering the stupid questions. all worth it!
 
Would you be able to post some helpful points/remarks for anyone planning on building this unit Bonsai? It's been long on my list. Have most everything needed for it but the case. Cheers.
 
Yes have lots of advice or problems that I had that I would love to share. I found it very difficult to get solid info when builiding this unit.  I however am no electronics expert. I am a musician who loves great sound. I build these units to use creatively. So technical data may be lacking.

Tell me how you  plan to build the unit ie transformer or not. I will post details tomorrow.
 
Transformers and opamps, I think. I do like the aggression of the chandler unit.

 
Ok so first I got all the parts from electro chronic. Great guy, has all of the necessary parts, also does the testing. Worth the money to get the critical parts from him.

I always find that a picture is worth a thousand words and helpful with basic questions. I can send pics if you want.

PSU

I used the Igor PSU. I have the BOM if you need it. Inputs to the PSU were not easy to decipher until I got the schematic. Was able to connect to the transformer with that info.

Used a Hairball audio transformer for the 1176. Avel Lindberg 2X25 30VA dual primary/secondary toroidal power transformer.

Works great, no problem. Almost went with a larger transformer but space was limited in a two-space rack.

I would most likely build it with a deeper case and a 3U case next time around.

Relay board

I guess there were two versions of this. The instructions on what to populate are wrong. Again, the schematic was helpful in getting the right connections. However, the schematic is not the clearest. I am a noob with schematics so take that with a grain of salt. I populated the boards using pictures of others builds and matching up with available info. I was missing some basic connections when reviewing the schematics.

I am using Elcor transformers 1:1 input and output. Finally figured out that RZ and CZ are the Zobel network. These are different for different brands of transformers. Never knew what this was. I have no way of testing the transformers so I am going to populate RZ and CZ on the bypass board based on Elcor's recommendations.

I used DIMM sockets also for the relays on the relay board.

Motherboard
I sourced the HS2051 diodes for the build. They were expensive, but I hope made the build easier. Installed DIMM sockets so I could remove them easily. I tried to match the diodes I had but they were all so close that I don't think it makes any difference. I think they are military parts so the variation is very small. I had to purchase more than I needed to build the unit.

There are some unlabeled resistors and caps on the board. I trusted the schematic for these values and seemed to work. Did not populate R47.

Installed heatsinks on VT28 and VT29. 

During the 20V calibration only need one of the jumpers on the - and + sides.

I also used cut DIMM socket connectors for the AOT resistors.

I used these resistor values for AOT resistors. I have not had the AOT resistors calibrated.
AOT1 620r (Unity Gain)
AOT2 not used
AOT3 47K (Compressor Threshold standard value)
AOT4 (Compressor Threshold not used)
AOT5 3K (Limiter Threshold standard value)
AOT6 510r (Limiter Threshold, makes the unit limit more in limit mode)
AOT7 33K (Distortion without compression, standard value)
AOT8 68K (Distortion without compression, standard value)
AOT9 (Not Used)
AOT10 10r (DC voltage on the collector of VT5 and VT6 are the same)

Selector boards
I used the Limit "FIX" and that seemed to work well. Don't know what it did but it worked. I also used a 10k Linear pot for the limit. Did not use a switch.  R115 was then jumped. I think the two channels may match better with a pot.

One of the capacitors on the HPF are switched. Again the schematic is right and the board is wrong. This is from Bruno 2000. Ever wonder why the 40 Hz and 80 Hz settings on the HPF sounded the same?  It's because C110 and C108 are swapped (mis-labeled) on the switch board, that's why.

Used a ON-OFF-ON for the bypass switch. It is IRON-BYPASS-CLEAN. Clean being the compressor engaged without the transformers. All other switches are ON-ON. Used an ON-OFF for Link switch.

Wiring of the unit was very time consuming. There are many connectors and crimping the molex connectors can get aggravating. There were two times where a good connection was not made.  Be careful with the  connections from the PSU to the motherboard and then to the bypass board. I accidentally wired the second board wrong.

Connecting the link switch was wiring the LNK1 on each board to a switch. Shorting the switch allows for the unit with the greatest inputs in each control to be the control board.

The one problem is I am having trouble getting the lamps to light on the VU meters. BTW I have the Sifam meters. I have connected the VULED+ and VULED= from the bypass board. I get +28V and -28V from each but no light on meter. The lamp on the meters are 24V. Not sure of the problem. I know the only problem, I should be happy.




 
Two questions:
1.  How deep was the enclosure that you used?

2.  On the Iron-Bypass-Clean, is the clean unbalanced?  I could probably figure this out by digging in the docs, but I was hoping a simple question would be faster.
Thanks,
Patrick

 
11 inches. 14 would be better.

Not sure about the outputs without the transformer. I assume they are unbalanced.
 
Still digging out from some personal issues, but I'll try to help as I successfully completed my unit, and it sounds really fine.  I am by no means an expert, but I have some nice test gear, and was able to look at multiple waveforms and Voltages simultaneously.
First, I could NEVER get the unit to put out unity gain without doing some extreme things to values.  My solution was a 1:2 output transformer, and that works.
Second, I modified the bypass board so that the "electronically balanced" option on the bypass switch used the chip input, but the output is going through a big honkin' Jensen 123 transformer.  The switch works like this, up position, Zutt input transformer, Carnhill output.  Mid position hardwire bypass ("bypass-I don't believe in it"). Down position chip balanced input, output through Jensen 123.  Additionally, I used a by-color LED so that up showed red, and down showed blue (the blue is TOO bright.  Gonna have to fix that).  I need to add that the "Festoon" (?) lamps for the meters draw a LOT of current.  That combined with switching 6 (?) relays required a MUCH larger power transformer than I thought.  The result was regulator starvation hum until I changed it out.
One of the "tricks" I discovered the hard way is that the differential transistor pairs need to be matched along with the diodes.  I went through more than 20 types, and measured over 1000 diodes.  I set up an "automated" test procedure with my AP DCX-127 that would step the diodes, and then imported the measurements into a database program, then sorted to find matches.  Out of 100 diodes (that's how many I usually bought of one type), I could get 8-10 pairs that were really close matches.
More later.
Best,
Bruno2000
 
This is how I went as well, much nicer sounding with transformers on the in and out. I went with a 1:1 vintage Sowter on the inputs and a EA1166 on the output wired 200:600.

I also modified the FB resistor (3K3 iirc) to apply a 6db boost which I placed on a toggle switch on the front panel. This allows the gain knob to run mostly in a more central position and affords some additional gain if needed.

bruno2000 said:
First, I could NEVER get the unit to put out unity gain without doing some extreme things to values.  My solution was a 1:2 output transformer, and that works.
Bruno2000

Mark
 
Are you drawing power for the Festoon lamps from the VULED- and VULED+ or wiring another way. Would the LED versions of the lamps draw less current?

Bonsaimaster
 
Bonsaimaster said:
Are you drawing power for the Festoon lamps from the VULED- and VULED+ or wiring another way. Would the LED versions of the lamps draw less current?

Bonsaimaster

I believe that I wired the meter lamps in series including a series resistor directly across the bridge of the regulator board.  I like the warm glow of under-Voltaged incandescent lamps.  LED lamps will draw significantly less current.  YMMV
Best,
Bruno2000
 
Since it's now almost impossible to get the suitable 2.4mA meters for this built (especially if you want mirrored ones), I first tried to use an opamp converter to use standard VU meters, but calibrating was very difficult. The solution is a small circuit around an Attiny85 that uses a lookup table to convert the incoming signal to the correct voltage values for VU meters.
It is also very easy to "mirrow" one meter,  I only need to print out one inverted meter scale.
The ballistics are a bit slower than on the correct mA meter, but I'm not really concerned about that :)

30vc5fd.jpg


Here's a video of the buffer in action:

https://www.youtube.com/watch?v=Ip_s31CcbPQ&feature=youtu.be
 
Hi there !
Trying to figure out a gain difference between the two canals.
By measuring and testing, I sorted out that T_E has quite a big difference.
Any idea what I can change ?
Should be around VT16 VT17 ?

Thanks guys !
 

Latest posts

Back
Top