the Poor Man 660 support thread

[ioaudio]

http://www.banzaieffects.com/WIMA-MKS4-10uF-250V-LS27-5-pr-23603.html

 

[jdbakker]

[quote author="ioaudio"]http://www.banzaieffects.com/WIMA-MKS4-10uF-250V-LS27-5-pr-23603.html[/quote]
That would appear to be a PE cap (MKS series) rather than the PP (MKP series) that's called for. Banzai's page is a bit...contradictory, but I see two mentions of MKS and only one MKP :wink:

The listed pitch also doesn't match the PCB hole distance (27mm vs 37.5mm)

JDB.
[and Conrad.nl lists a delivery time of somewhere in October...]

 

[Rob Flinn]

[quote author="jdbakker"][quote author="ioaudio"]http://www.banzaieffects.com/WIMA-MKS4-10uF-250V-LS27-5-pr-23603.html[/quote]
That would appear to be a PE cap (MKS series) rather than the PP (MKP series) that's called for. Banzai's page is a bit...contradictory, but I see two mentions of MKS and only one MKP :wink:

The listed pitch also doesn't match the PCB hole distance (27mm vs 37.5mm)

JDB.
[and Conrad.nl lists a delivery time of somewhere in October...][/quote]

Thankls for that. I guess the pitch is down to the fact that the board is made for a 630v cap, possibly a bit of overkill !!

 

[flintan]

I believe it's because that is a polyester cap and polypropylene is less space efficient. But i'm not 160% of that so...

 

[jdbakker]

[quote author="Rob Flinn"]I guess the pitch is down to the fact that the board is made for a 630v cap, possibly a bit of overkill !![/quote]
The cap listed in the BOM is a 250v part. Besides, according to the part selector at WIMA's site all 10uF polyprop parts have a 37.5mm pin spacing.

JDB.

 

[[silent:arts]]

the CAP is 250V, which isn't needed.
but there is no quality 10µF / 63V cap to my knowledge.
at least not from the standard suppliers.
we felt save to use the WIMA MKP4, since it is available at mousers and conrad (US and EU, at least - and no problem to order from other countries there)
if we busted their stock already ... :green:

 

[emrr]

[quote author="[silent:arts]"]
[quote author="emrr"]Realize that if you do the threshold atten exactly like the [silent:arts] gain, then there is no 'compression off' position in the amp.[/quote]
the lowest switch position is connected to GND, there will be no signal in the sidechain amp, which I would say is "compression off".[/quote]
I mean if one wires as you said you would wire your input, from +18 to -4. Then there is no stop at 0, only as low as -4. Someone will miss that bit.

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.

 

[[silent:arts]]

:grin: now I understand what you mean :thumb:
and you are right, a "dB Attenuator" for the Threshold wouldn't be a good idea, take lin or log there.

 

[cannikin]

Volker can you clear this up for me, I don't know why this is bugging me so much because I'm pretty sure I got it right but still it is....

Stereo Unit for PSU =
Q4 - IRF820
Q5 - IRF840

For Mono Unit PSU =
Q4 - IRF820
Q5 - IRF820

 

[cannikin]

Also what brand resistors are you guys using for the switches?

Vishay/Dale CPF Series
Holco

If your going Holco from percyaudio.com

Here are the closest Holco values in relation to Silentarts excel sheet for a 24step 15K (still have to do some figuring but here ya' go):

0
174
187
200
221
243
274
287
316
357
392
432
475
523
562
649
715
787
866
953
1.07K
1.15K
1.27K
1.43K
1.58K

 

[Barbera Media]

Analag, Silent:arts,
I received my PCB's today without incident. I have to say that these boards are among the best quality I've seen. Can't wait to get cracking on these babys. Thanks again for taking the time to put these together. My recordings are forever in debt to you.

 

[emrr]

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.

I find this reasonable for the input, so I'm mixing the Dale cmf55, Dale rn60 and Xicon 271 series 1/4 W 1% metal films. We'll see what happens. The Dale rn60's come in at $.48 to $0.97 in most cases, and many values are not present, so I skipped them other than a few positions. Here's the output of the calc located in the Meta. The values, listed for 1 dB steps, differ from the spreadsheet values. that is followed with nearest value Mouser parts, in a mix of the three types.


Step 1, Attenuation = 22 dB, Rx = 13809 ohms, Ry = 1191 ohms, Resistor = 1191 ohms.
Step 2, Attenuation = 21 dB, Rx = 13663 ohms, Ry = 1337 ohms, Resistor = 146 ohms.
Step 3, Attenuation = 20 dB, Rx = 13500 ohms, Ry = 1500 ohms, Resistor = 163 ohms.
Step 4, Attenuation = 19 dB, Rx = 13317 ohms, Ry = 1683 ohms, Resistor = 183 ohms.
Step 5, Attenuation = 18 dB, Rx = 13112 ohms, Ry = 1888 ohms, Resistor = 205 ohms.
Step 6, Attenuation = 17 dB, Rx = 12881 ohms, Ry = 2119 ohms, Resistor = 231 ohms.
Step 7, Attenuation = 16 dB, Rx = 12623 ohms, Ry = 2377 ohms, Resistor = 258 ohms.
Step 8, Attenuation = 15 dB, Rx = 12333 ohms, Ry = 2667 ohms, Resistor = 290 ohms.
Step 9, Attenuation = 14 dB, Rx = 12007 ohms, Ry = 2993 ohms, Resistor = 326 ohms.
Step 10, Attenuation = 13 dB, Rx = 11642 ohms, Ry = 3358 ohms, Resistor = 365 ohms.
Step 11, Attenuation = 12 dB, Rx = 11232 ohms, Ry = 3768 ohms, Resistor = 410 ohms.
Step 12, Attenuation = 11 dB, Rx = 10772 ohms, Ry = 4228 ohms, Resistor = 460 ohms.
Step 13, Attenuation = 10 dB, Rx = 10257 ohms, Ry = 4743 ohms, Resistor = 515 ohms.
Step 14, Attenuation = 9 dB, Rx = 9678 ohms, Ry = 5322 ohms, Resistor = 579 ohms.
Step 15, Attenuation = 8 dB, Rx = 9028 ohms, Ry = 5972 ohms, Resistor = 650 ohms.
Step 16, Attenuation = 7 dB, Rx = 8300 ohms, Ry = 6700 ohms, Resistor = 728 ohms.
Step 17, Attenuation = 6 dB, Rx = 7482 ohms, Ry = 7518 ohms, Resistor = 818 ohms.
Step 18, Attenuation = 5 dB, Rx = 6565 ohms, Ry = 8435 ohms, Resistor = 917 ohms.
Step 19, Attenuation = 4 dB, Rx = 5536 ohms, Ry = 9464 ohms, Resistor = 1029 ohms.
Step 20, Attenuation = 3 dB, Rx = 4381 ohms, Ry = 10619 ohms, Resistor = 1155 ohms.
Step 21, Attenuation = 2 dB, Rx = 3085 ohms, Ry = 11915 ohms, Resistor = 1296 ohms.
Step 22, Attenuation = 1 dB, Rx = 1631 ohms, Ry = 13369 ohms, Resistor = 1454 ohms.
Step 23, Attenuation = 0 dB, Rx = 0 ohms, Ry = 15000 ohms, Resistor = 1631 ohms.



71-CMF551K6200FHEK 1.62Kohms
271-1.47K-RC 1.47Kohms
271-1.3K-RC 1.3Kohms
71-RN60D-F-1.1K 1.1Kohms
71-RN60D-F-1.05K 1.05Kohms
71-CMF55909R00FHEK 909ohms
271-820-RC 820ohms
71-RN60D-F-732 732ohms
271-649-RC 649ohms
271-576-RC 576ohms
71-CMF55511R00FHEK 511ohms
271-464-RC 464ohms
271-412-RC 412ohms
71-CMF55365R00FHEK 365ohms
71-CMF55330R00FHEK 330ohms
71-CMF55301R00FHEK 301ohms
271-261-RC 261ohms
271-232-RC 232ohms
71-CMF55200R00FHEK 200ohms
71-CMF55182R00FHEK 182ohms
271-162-RC 162ohms
71-CMF55150R00FHEK 150ohms
71-CMF551K2100FHEK 1.21Kohms


I will play with some various pots before deciding how to go with the Threshold control.

 

[mitsos]

continuing my power trafo monologue.

I took a closer look at the G9 and while I think that powering method is possible (previous post), it looks like too much of a PITA right now. so I am considering two other options:

:idea:1) Use the two 2x6V 50VA piggybacked to get 6.3V and 250V, and buy a third trafo, 2x 15V 10VA (wired to mains) to use for the -17 and +18... easiest but I'd be out another $13, and have one more lump-o-steel in my case.

:idea:2) Instead of the third trafo, I would rather hand-wind two 15V windings on the first transformer (the one connected to mains)... I've never done it but glancing at some threads it just seems easier right now, if I can find the right wire. Since I don't know how many turns the primary has, I'll just use PRRs advice in old thread, to wind 10 turns and see what voltage that gets, so I get a round-about view of V/turn. How likely am I to kill myself/my boards?

thanks!

 

[cannikin]

IF you really want to go crazy with your switches

http://cgi.ebay.com/Pr-Daven-211-CM-22-Position-Stereo-Switches-NOS-NIB_W0QQitemZ350087654281QQihZ022QQcategoryZ3284QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[MartyMart]

WOW - those are gorgeous switch's David !!!
I had to go for the €12 ones that have been mentioned around here a few
times....... I'm cheap !

Marty.

 

[flintan]

mitsos, why not buy one of the custom made power transformers for this project. Probably cheaper than buying three different ones and a better solution than back to back transformers..

 

[mitsos]

[quote author="flintan"]mitsos, why not buy one of the custom made power transformers for this project. Probably cheaper than buying three different ones and a better solution than back to back transformers..[/quote]Because I am doing a mono project, and since very few people are doing it, there hasn't been any mention of possible power schemes. And I'm cheap, I can't pay $80 for a tranny that is way overbuilt for my unit. The two 50VA trannys cost $13 each (not counting shipping but I'm buying a few others at the same time) plus a few dollars in fancy enameled wire, and I'm good to go for $30. I am just waiting for someone more technically savvy to tell me this will work and won't blow up my house.

 

[nielsk]

Mitsos, This can work.... on the second tranny (of the 120/240 to 6 volt hooked up to the 6 to 120/240 volt ala g9) only hook up one 6 v lead set to the 1st tranny, and take the second 6 volt lead set to a voltage tripler to get the -17 volts....
the big question is how much current is needed at the 245/136 legs and the -17 leg (?) one can typically use a pretty small transformer for the second unit

 

[[silent:arts]]

Hi mitsos,
it could work, it could not, we don't know.
this could be a reason why nobody gives you advice ...
for sure it would be far safer to go with one of the extra wound transformers, even if the specs are for stereo. won't hurt a mono unit.

 

[emrr]

On the power transformer experiments; we know the recommended current draw, so run the math and sort out the required load resistance for the PSU and/or rectifier output. Then use dummy loads while experimenting. Should be simple to rough it in that way, and there are always resistor values within the PSU you could change slightly later to adjust output voltage. All I have to offer there; hope it helps.

Cannikin; DIY Daven's. I have some 12 position units like that which have an extra lug per position you can strap for MBB, or leave open for BBM. You need massive real estate to use them. Those are mighty high in price, I must say. You sometimes find them on ebay for 1/10th that price. But if you must have the best, there they are.