the Poor Man 660 support thread

[[silent:arts]]

they are

 

[babyhead]

Score!

Thanks!

 

[Moby]

the in-circuit sweeps of completed units we've seen haven't shown any ringing, so i wouldn't worry too much.

Sorry, must be that I missed that. Where is the sweep measuring of the unit?

 

[[silent:arts]]

http://www.groupdiy.com/index.php?topic=26887&start=166

 

[Moby]

Thanks :grin:

 

[cannikin]

HEY IF any one wants... I have 3 PM660, 2 PSU, 5 Bypass relay PCBs unstuffed that I'm not going to use... I was excited and greedy for this project  ;D  Same price as volker sells them for.  I prefer shipping in US so you'll get them fast, they aren't the groovy white christmas ones but... give me a PM, didn't really want to post in the BM.

 

[Moby]

the rotary switches

you would better want it exponential (or log in potentiometer language).
it took some time to figure this out, but with some help I was able to do an Excell sheet to calculate the resistors for emulating a real log potentiometer.
fill in the desired steps you want: Log Pot to Switch Excell Sheet

you may want it in dB steps (like me). at the end it is a series attenuator.
my prototype has 18dB of gain, thus I will do one dB steps on an Elma, stopped to 23 steps, going from -4dB to +18dB.

Volker, are the steps in the Excel sheet calculated for 1db attenuation per step? If not, can you tell me about?

 

[Moby]

polite bump 

 

[[silent:arts]]

Hi Moby,

no, the Excell sheet just converts the log pot curve to a switch.
for 1dB steps you can use any series attenuator spread sheet out there.

 

[Moby]

Thanks. I was thinking about adding correct values around input control. I already soldered 8 double 15k 24 position sw.  So, you don't know about db attenuation per position?

 

[lolo-m]

Make your maths !!! ;D
Seriously they are :
24°) 0 db
23°) -0,96 db
22°) -1,96 db
21°) -2,95 db
20°) -3,97 db
19°) -5,00 db
18°) -6,05 db
17°) -7,13 db
16°) -8,23 db
15°) -9,37 db
14°) -10,54 db
13°) -11,76 db
12°) -13,03 db
11°) -14,37 db
10°) -15,79 db
9°) -17,30 db
8°) -18,95 db
7°) -20,77 db
6°) -22,83 db
5°) -25,24 db
4°) -28,20 db
3°) -32,17 db
2°) -38,64 db
1°) - inf

I hope it helps...

That's pretty close to -1db per step in the last 12 positions and IMO it's really usable.

 

[Moby]

;D Thanks... I was always poor in math so I will round the numbers 

 

[lolo-m]

;D Thanks... I was always poor in math so I will round the numbers 

Of course, round the numbers, I've been precise to let you choose the closer value... I will do the same

 

[Mr. Snoid]

I scored some cheap retired grayhill 70BFD30s for Fabio's 1270 build a while ago and was wondering  if I SHOULD use them as Time Constant switches.

The problem is they are non-shorting, but I could stop them to 6-8-or even 10 position and solder the resistors to the PC board connectors. Would save a few bucks...but is the non-shorting issue a big deal? Could it be compensated for easily with a cap perhaps?

Or should I just say "**** it" and buy some 2x6 Lorlins?  It's only money, right???? 

Tod

 

[SaMpLeGoD]

Hi,

Quick question, for threshold and gain ,I bought on ebay 4x 24 steps rotary switchhes with double deck for my PM670... just need to ask one thing: the values obtained in the Volker's datasheet need to be present in each deck... matched??

Cheers

Eddie ;-D

Ps.: Volker, received you white boards! fantastic! thanks a lot!!!!!

 

[lolo-m]

I scored some cheap retired grayhill 70BFD30s for Fabio's 1270 build a while ago and was wondering  if I SHOULD use them as Time Constant switches.

The problem is they are non-shorting, but I could stop them to 6-8-or even 10 position and solder the resistors to the PC board connectors. Would save a few bucks...but is the non-shorting issue a big deal? Could it be compensated for easily with a cap perhaps?

Or should I just say "**** it" and buy some 2x6 Lorlins?  It's only money, right???? 

Tod

You don't really need shorting switches for the time constants IMO. The only thing that will occur will be weird attack/release during the switching operation... It will take a few microseconds to go from one step to another so...
You DO NEED shorting switch for the input switch only not to hear a clip or a crack when you switch... Threshold is a lot better shorting but I'm not sure you'd be able to hear anything with a non-shorting switch...
To resume :
- Shorting switch for input necessary
- Shorting switch better for threshold
- Any switch or a pot for time constants

 

[lolo-m]

Quick question, for threshold and gain ,I bought on ebay 4x 24 steps rotary switchhes with double deck for my PM670... just need to ask one thing: the values obtained in the Volker's datasheet need to be present in each deck... matched??

If you've got time enough, it's certainly better to match them, but stuffing those switches is already a long work so... If you take 1% resistors, your switches will be matched certainly at less than 2% ( 2% is the worst possibility if you buy following resistors in the same bobin )... It's always better than any pot !!! ;D

PS: we certainly bought the same switches... 
If you need the resistors for the switches, I've got 34 left of each value !!! PM me

 

[Benny]

Hi all.

Finished my PM670 today. Anything seems pretty good. I've got 6,3-6,4V for the heater. All the other voltages and trimmers are set correctly. I checked all switches and the wiring.
But it sounds somewhat distorted if driven at "normal" level. I have to turn down the channel levels in my DAW to about half to hear no clipping. Thought i miswired the gain switches or something like this but the wiring seems o.k. The threshold switch works good, time constants too But the gain switches don't seem to work.

Any ideas where to start searching?

 

[waldorfcave]

But the gain switches don't seem to work.

I think you forgot the cable between the decks of the gain switch! is the same like threshold switch, but not clearly to see in the drawing :

 

[Benny]

Yup, I didn't actually see that. 
Hope it solves my problems... Thanks mate.