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 Post subject: footswitch
PostPosted: Tue Apr 14, 2009 5:36 pm 
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Alright, Coco, can you please lead me to the latest info on the supposed footswitch for the Triwatt :shock: :shock: 8) 8)
I'd like all that is available. Please.

Does anyone else have info they were thinking about???
I'd like everything available here, then let's see how intelligent we all are.
I think we'll win. :D :D :D :D :D :D

If this info is already available on another thread, please just direct me.

Thanks
Cheers
\Jac :roll: :roll:


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PostPosted: Tue Apr 14, 2009 7:39 pm 
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This info is on the schematic sent with each kit for those who want to build themselves. Current production is on breadboard material.

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PostPosted: Tue Apr 14, 2009 10:56 pm 
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Still working on switching with relays Stephen?


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PostPosted: Tue Apr 14, 2009 11:27 pm 
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kurtlives wrote:
Still working on switching with relays Stephen?


Yes, a relay is the plan. Zaphod is putting the first one together now. More to come soon.

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PostPosted: Wed Apr 15, 2009 12:31 pm 
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Stephen/Phil, do you anticipate any problems with the footswitch circuit adding to the overdrive squealing issue? People should probably be careful and make sure they have that under control before adding the relay and other electronics into the mix... Just thinking :hmmm:

Joe G

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 Post subject:
PostPosted: Wed Apr 15, 2009 2:08 pm 
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I think we need to put things into some perspective:

- The Triwatt has the same number of gain stages as a SLO 100 or Mezza DR (although the gain level of most of those stages is throttled back a little).
- This means good lead dress, with wiring kept short and tidy, is a must.
- Provided you follow that guideline, this amp will give no problems.
- I was nervous as heck when I built the prototype Triwatt, due to what I knew about its preamp gain.
- I was pleasantly surprised when there were no squeal issues in the prototype, except for one caused by an incorrectly wired resistor in the negative feedback/presence control circuit.
- Yes, there may be some increased potential for squeal with the foot-switch circuit installed, since the one wire that some people have had problems with (connected to the two 470k mixing resistors), now has to be taken to the back of the chassis where the relay board is. So this is now a shielded wire.
- OTOH the nice thing is that the remaining connections, such as between the relay, V2's grids and the 100k resistor, will all be nice and short and close to V2's socket.

Like Stephen/coco says, this is something I'm working on as I build the amp.

The golden rule always is to take a little time and do a nice neat job on the wiring. :)

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 Post subject:
PostPosted: Wed Apr 15, 2009 6:37 pm 
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I have to agree with Phil 100%. Lead dress is is critical in this amp. This is the 7th amp I've built & the first where I really noticed lead dress issues. In my case it was only an issue with the OD engaged & running pretty hot. Otherwise the amp was extremely well behaved & quiet.

I can see Phil's point regarding the OD relay board possibly making things less troublesome by moving a lot of that wiring away from that sensitive area, and shielding that "hot" wire (something I plan to try on the existing design when I get some time).

I'm also going to try an experiment with the pre-amp wiring based on some stylistic differences between my build and Andrew's (he's having no squealing issues now). I'll update in my build thread if it makes any difference!


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 Post subject:
PostPosted: Fri May 01, 2009 5:20 pm 
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Any new developments on the footswitch front?


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PostPosted: Fri May 01, 2009 7:03 pm 
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G-log wrote:
Any new developments on the footswitch front?


Still working on it. First attempt was too noisy.

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 Post subject:
PostPosted: Fri May 01, 2009 8:03 pm 
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Quote:
The golden rule always is to take a little time and do a nice neat job on the wiring.

Truer words!
Don't forget to "bitch" alot and actually ask pertinent questions, once in a while, lol

And tonight, I'll install just back wiring :shock: :shock: :lol: :lol: :lol: :lol:
Very careful, very careful :wink: :wink: :wink: :wink:
But having so much fun.
Especially having "something" to do :D :D 8) The most important thing to me right now :shock: 8) 8) 8) 8)

Cheers :roll: :roll: :roll: :roll: :roll: :roll: :roll:


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 Post subject:
PostPosted: Fri May 01, 2009 8:16 pm 
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Although, I'm not turning it on without it :shock: :shock: :shock: :? :? :? :lol: :lol: :lol: :lol: :D :D :D :D :D
(the footswitch)
Not Kidding :shock:


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 Post subject:
PostPosted: Mon May 04, 2009 1:11 pm 
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Quote:
G-log wrote:
Any new developments on the footswitch front?


Still working on it. First attempt was too noisy.


What kind of noise do you think you're getting Stephen/Phil? Do you think it's from the relay coil itself or a side effect of using the heater power, routing issues, etc.

Joe G

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 Post subject:
PostPosted: Mon May 04, 2009 2:07 pm 
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Any answers to Joey's questions :?: :?: :?: :?: :?:

Curious????
Cheers


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 Post subject:
PostPosted: Mon May 04, 2009 3:16 pm 
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joeyvelour wrote:
Quote:
G-log wrote:
Any new developments on the footswitch front?


Still working on it. First attempt was too noisy.


What kind of noise do you think you're getting Stephen/Phil? Do you think it's from the relay coil itself or a side effect of using the heater power, routing issues, etc.

Joe G


Interesting question. I was thinking of splitting off the heater secondaries, rectifying & filtering the tap, and using the resulting "cleaner" DC to drive the relay. I would hope that would be relatively quiet with regards to interferance/hum.

In fact, I was thinking of rectifying the heaters too to see if I could lower the noise floor even more. I did that with my Valve Junior rebuild and it made a significant difference.

Another option would be to use a different type of relay - the type that uses a "momentary" power feed to trigger the internal switch back & forth but doesn't require continuous power (can't remember what those are called). Bit of a different animal to wire up though.

However, if the noise is from a different source (the "majic purple lead" that gave me some squeal problems for example), that's a whole different issue.


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 Post subject:
PostPosted: Mon May 04, 2009 3:30 pm 
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Still trying to quiet this down. Still working on it. Will post when we have some decent results, but IMO, tap off right at the pilot light, then bridge / full wave with good filter , 1000uF. Possibly a series dropping resistor before the cap. Will let you know.

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 Post subject:
PostPosted: Mon May 04, 2009 4:58 pm 
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Thanks Stephen. I have a few relays in my V6 so I'm anxious to hear where these problems are coming from. I have a separate supply for the relays and LED's so I'm hoping noise won't be an issue in my case. Will stand by....

Quote:
Another option would be to use a different type of relay - the type that uses a "momentary" power feed to trigger the internal switch back & forth but doesn't require continuous power (can't remember what those are called). Bit of a different animal to wire up though.


Emo, that would be a latching relay. It would be trickier to wire up and would require more circuitry. You could use a momentary switch though, which would be pretty cool 8)

I'm on it Jac :lol:

Joe G

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 Post subject:
PostPosted: Mon May 04, 2009 8:19 pm 
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coco wrote:
Still trying to quiet this down. Still working on it. Will post when we have some decent results, but IMO, tap off right at the pilot light, then bridge / full wave with good filter , 1000uF. Possibly a series dropping resistor before the cap. Will let you know.

Good idea, noise I have had from relays were cured by that.


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 Post subject:
PostPosted: Mon May 04, 2009 9:42 pm 
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joeyvelour wrote:
What kind of noise do you think you're getting Stephen/Phil? Do you think it's from the relay coil itself or a side effect of using the heater power, routing issues, etc.

It was a buzz. I carried out a series of tests which clearly demonstrated that the problem wasn't from the amp's layout or wire routing. Nor was it noise getting into the heater chain from the relay's DC power supply, but rather noise being induced into the relay contacts from the coil. Not something you would notice so much in a lower gain amp. So we had to make the DC supply to the coil quieter. We had a 1000uF cap there, and sometimes a big filter cap after an SS rectifier can cause spikes due to the cap's inrush current. This can be alleviated by having a small snubbing resistor between the rectifiers and the filter cap.
coco wrote:
... IMO, tap off right at the pilot light, then bridge / full wave with good filter , 1000uF. Possibly a series dropping resistor before the cap.
kurtlives wrote:
Good idea, noise I have had from relays were cured by that.

Thanks for that confirmation. After discussing this at some length, Stephen and I also feel that in addition to the snubbing resistor, by having the DC power supply physically a longish distance away from the relay, any remaining spikiness will probably get absorbed in the capacitance of the wire run to the relay around the back of the chassis.

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 Post subject:
PostPosted: Tue May 05, 2009 7:18 am 
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Thanks for the info Phil.
Per an engineer friend's suggestion, I also put an RC snubber circuit in parallel with the diode across my relay coils, just a 1k resistor in series with a .1uf cap, and that in parallel with the diode and coil.
Balancing the heaters was something else he mentioned...

Joe G

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 Post subject:
PostPosted: Tue May 05, 2009 10:40 am 
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I have done further tests. I built a small seperate power supply board.

I connected the supply to the heater 6.3V at the pilot light. With 6.3 V bridge rectifier and 1000uF this gives about 9 VDC floating ground. Then I added a 68 ohm snub resistor and the vltage was about 8V.

I tried it this way and it still induced hum. I then added a 1uf from supply to ground and it was marginally better. Nothing so far has been better than when I used a separate 6.3V filament transformer and the bridge rectifier or a 9V regulated wall wart PSU. In both cases with the -ve side connected to chassis. This works fine and was very quiet.

Still testing. Still looking for the ideal solution.

So, you could use a small 5 - 6.3 VAC and bridge rectifier circuit to provide an external supply, grounding the negative side. Or even a regulated wall wart power supply, deconstruct it and install it inside the amp.

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