the Poor Man 660 support thread

[khstudio]

Hi Kevin,
I'm interested in your frequency response finding.

A question:
did you try to sweep just the side-chain amp?
and the results is the same [inverted now] bass roll-off?

I'll post any new findings as I usually do but it would be cool if someone else could check their unit also. 

Yea... either bass roll off or high boost in the side-chain... I still haven't had a chance to test that yet but I will.

 

[khstudio]

I'm still running it with one tube in the side chain until I find a better PT option so I can run the "proper" 2 tubes in the side chain.

I didn't notice or I missed that detail with just one tube. I think that 1 tube is not "happy" with 10K termination  :-\

Were have you been... I've been talking about using one tube in the side chain for several weeks now.

Also, if you're referring to this frequency response thing & the one tube... I already addressed that.

BTW, I did test the side chain with 1 & 2 tubes... same outcome.

 

[Moby]

Were have you been... I've been talking about using one tube in the side chain for several weeks now.

On holiday 
Please ignore my previous comment about 10k termination, it's OK for 5687's  :-\
But don't ignore comment about TX compensation. Did you tried to measure  transformer response, but with high (few Kohm) impedance source?

 

[khstudio]

Hi Moby,
No, I didn't measure the TX's "alone" outside the circuit.
Should I do this?

 

[Moby]

Why not? Than you will know is there a problem. Also, remember that 10k/600 has 4 times more voltage on primary from expected on sec . I measured 10k/600 inductance and if I remember correctly primary inductance was around 30H. Pretty light for 10K   For two 5687 in parallel it can pass with some slight bass roll of but with one its double worse  

 

[idylldon]

Kevin,

First off, I appreciate all the work you've put in to testing this project.  It will help those who follow a great deal.

I did the testing you asked and found that my unit stays pretty flat until about 400Hz.  There are some slight variances between channels, but they track pretty closely.  I used a 1.2 V PP input signal and kept the time constant at 1 (I have the switch setup).  The input/threshold controls were set so that the input signal was compressed 1dB, which was an easy reference point from which to judge meter movement.  At 400Hz, it starts to compress more (.25dB) and ultimately compresses up to 1dB more between 1K and 3K, and then it's back to flat at 6K and beyond.  It looks something like this:

60Hz: -1dB
80: -1
100: -1
200: -1
400: -1.25
800: -1.75
1K: -2
1.2K: -2
2K: -2
3K: -2
4K: -1.5
5K: -1.25
6K on up: -1

This wasn't a rocket-science test because I just used the Hoyt meters in my 670, but I think it gives a pretty clear picture of a bit more compression happening at certain frequencies. 

Cheers,
--
Don

 

[lolo-m]

Kevin,
Definitely you need to check with a pink noise your freq response... If you can't, try with single frequencies and try to make another report  ... I will try to check mine tomorrow but I didn't remember having a bad surprise when I made some tests with pink noise (nor music) on mine with stock TC network or with the SCAB...
I had the same high and bass roll-off compressing or not (something close to your uncompressed frequency response)...

 

[khstudio]

Thanks Don & Lolo-M.  ;D
Don, it looks like yours isn't as drastic as mine. I was able to see my VU move a few more points than that.
Also, even with a "Single" tone test, once mine rolls off, it stays there!

Lolo-M,
That would be great if you could test yours too & post the results.
so your unit is pretty "Flat" compressing or not? wow... mine isn't.
I did test with individual tones & it reacts the same as the pic I posted.

Still need to test the side chain & do the Pink noise test.

 

[inputoutput]

hey KH, The last time I checked, I had a normal flat line all the way up to 16K, but a pretty hard bass-rolloff starting around 60Hz.

 

[khstudio]

hey KH, The last time I checked, I had a normal flat line all the way up to 16K, but a pretty hard bass-rolloff starting around 60Hz.

Was this while compressing or raw thru the unit?

My unit it pretty flat until I compress.

 

[inputoutput]

yes, it is while compressing. - can´t get enough signal in there to drive it hard. But with a medium / light compressing and limiting, the signal looks flat. Both with a sweep and with a noise signal on the input. 

At the moment I'm trying to get rid of hum..... Got quite a lot going down there, and it is pretty annoying.

 

[W DeMarco]

Allright Folks!

Im trying to make my way through the tweaks and Im still plaqued by a problem that Im narowing down but could use some input on. 

Left channel bad
Right channel stellar/perfect

Left channel:  Threshold compresses signal heavily(-10dB+) when in 5 -10 position of threshold switch.  This is regardless of bypass.  if I switch gain to 2nd position it lightens a bit but still compressing in bypass or not, signal or not.  Once i throw threshold switch beyond 10th posititon it seem to lighten up according to meter(old ass meters from my buddies engineer fathers workshop) . 

Already tried stuff:  Swaped all tube 1pair at a time between channels
swapped all switches one at a time between channels

So im a bit lost right now.  Hopin I could get some ideas from you guys

Thanks

Will

 

[mich]

This is regardless of bypass

The bypass here is true bypass wich means none of the controls should have any effect while bypassed.

first look for wiring mistakes in the left bypass circuit board.or maybe the relay itself .or the power to the relay.

 

[khstudio]

The fact that you're getting compression while in BP is the most concerning.

Check your BP connections VERY carefully... BOTH the switch & the Molex connections to the PCB for shorts, etc...

You can also try to measure the Control Voltage @ PL1 (or the Center of the 2 Decks)...
this is your main control voltage.
It should measure approximately -4.5 DC ( in BP) & increase with compression up to about -8 to -10 vDC = heavy compression.
(download the Voltage charts posted... these MAY help determine any problem areas)

I'll try to help as much as I can.

Good Luck.

 

[W DeMarco]

Thanks guys,

I'll look over my connections again on the BP side of things.  I did try unplugging the in outs and the power to the bypass board figuring that would be a quick test of the BP.  Of course nothing changed.  Im thinkin tonight Ill swap the main boards around and see if the bad channel jumps from left to right.

Kevin,  I have only found the blank Voltage charts and Idylions,  I thought I read somewhere that there was a compiled version?  Once completed ill of course fill one out for the team!

Later

 

[[silent:arts]]

swapping both channel PCBs is a good idea, to know it it is a fault on the PCB or in the wiring / transformers.
let us know

 

[inputoutput]

If you are wondering if your PT has enough power OR if your meter is bouncing OR if you're getting random spikes in the sound, OR are wondering if your tubes are bad.  The cure might be as simple as lowering that R9 on the PSU-board. Try 176K as a start, and go lower to 170K if the problem is still there.

a reminder : All heater related wires should preferably be as thick as 1,5mm-2.0mm.  If your wires are too thin, you'll probably loose a lot of power.

 

[radiance]

If you are wondering if your PT has enough power OR if your meter is bouncing OR if you're getting random spikes in the sound, OR are wondering if your tubes are bad.  The cure might be as simple as lowering that R9 on the PSU-board. Try 176K as a start, and go lower to 170K if the problem is still there.

Ok thanks! How did you find out? Trial & error ;-)? What's the idea behind this?

Sorry, I don't have my schematic here and I don't know what R9 is doing....

 

[inputoutput]

Well, I Thought that rising R9 would be a good idea to get more voltage... until I realized that the "136" voltage rail should be lowered instead.  It seems to stabilize the 6BC8 part of the circuit.  I have a feeling that it is pushed just a tiny bit to far by going to 182K. I have settled for a 177K here, but I think you may go as low as 160K or even 150K.

 

[radiance]

Thanks again! Still in the building phase but I'll try this out for sure.

After finishing my summing mixer/monitor controler thingy, which was an awefull lot of work, I thought that a well documented project with pre made pcb's would be a breeze...but somehow this project takes me even longer to finish...leazy bastard me....