Pics of my D-lite build

[DaveBo32]

Hi All,
I finished building my amp today, I gotta say this thing sounds great. This was my first build ever and I'm glad I gave it a shot. Thanks to all of you who gave me a hand in this. I was able to build this amp around $375.00. I had to cut corners to save a dollar, I used a hammond chassis which I drilled and milled at work. I ended up using hammond transformers. All the wire and hardware I got from work. I wire test equipment all the time at work so I have some skills keeping things neat. I ended up using an old peavey bandit for the cab. Everything else I bought at mouser/antique amp supply/local stores. It still needs a little tweaking. I also wish I got matched 6v6s, because the bias voltages are 18 and 21. The speaker I have stinks, it's the sheffield that came with the bandit. I'll upgrade when I get a chance. Also I wasn't able to use the NFB part of the circuit, it seem to have a conflict with my opt. When I was adjusting the bias for the first time I got a high pitch squeal once I hit about 12mV an on. I noticed when I turned the presence to off the squeal went away. I was able to adjust the bias, but something wasn't right, the amp was noisy and when I hit a low pitch note the speaker would start a bellowing hum kind or rumble that got so bad I thought I was going to blow my speaker. I had to shut down. I decided to cut the NFB wire from the 4ohm tap. Every problem I had went away, except I don't think my presence pot is funtioning very well. It seems to have a little effect to the sound. Beside those little quirky things which are exspected with a first time build, I love it. I can't wait to experiment with it. If anyone has any suggestions, your help is greatly appreciated. I hope to have some sound clips soon. Enjoy the pics... 8) :D

[stevlech]

First of all, congrats on the new toy.

It sounds like the problem you have is a reversed primary on the output transformer. Switch the wires on pin 3 of your power tubes and reconnect the feedback. It should not squeal anymore.

[Darkbluemurder]

stevlech is correct. I had the same problem once. Just reverse the primaries of the OT and reconnect the presence control.

Good luck
Stephan

[DaveBo32]

Thanks Guys,
I will try that.

[BobW]

I also wish I got matched 6v6s, because the bias voltages are 18 and 21.

Dave, try swapping the tubes and see if the bias numbers are closer. Sometimes it's not the tubes, but the long tailed pairs.

IMO, a 3 mA difference really ain't that bad.

[DaveBo32]

Well I reversed the primaries, and my squealing problem went away. Thanks guys, that suggestion worked like a charm. Bob, I'll try swapping the tubes, but like you were saying 3mV isn't a whole lot. This amp just sounds better an better as I break it in. The peavey speaker I was using really killed the sound of this amp. I hook it up to my fender HotRod deville 4X10 Speakers an what a difference, this thing sounds awesome. I'm going to have to buy a real nice speaker for this amp. Now I just need to focus on cleaning up some of the hissing I get from time to time. Has anyone use an AC line filter in their D-lite. I have a feeling I am picking up a lot of outside noise from my ac source. My amp will be quite for a little while then I will get some soft hisses an spits, then quite again. It's not consistant. I tried moving wires around with a chop stick to see if I could find any culprits...nothing. I also want to replace the sheilded RCA cable with some RG174. I have 22awg 2 conductor wire sheilded with foil and a braided ground wire. I'm tempted to try it. Any suggestions

Thanks,
Dave

[BobW]

Intermittent hissing can be caused by cold solder joints, and or older parts, ie Leaky caps, carbon comp resistors, etc. I assume you have new components, so I'd go back over any solder joint that looks suspect. It could also be tarnish inside the tube sockets. Although they may be brand new sockets, it's best to clean them before installing tubes.

I'd like to find a cheap solder pot one day, because dipping all components leads into the pot for 1 -2 seconds tins and removes any chemicals and debris from the conponent leads before mounting to the board. This greatly reduces the chance of a cold solder joint, and the build looks professional with nice clean leads, and as they say in the industry, smooth, concave fillets.

[DaveBo32]

BobW,

Thanks, I'll give that a shot..What about the AC filter, do you think I should use it also?

Dave

[Drumslinger]

Nice going Dave. Congrats on your build!

[BobW]

What about the AC filter, do you think I should use it also?

The AC filter is a band-aid to the real problem. Check your grounds again too. Also with the chassis open and in a high gain mode, you can pick up almost anything from DC to blue light with these amps. I assume you have a top chassis cover or at least a screen in the enclosure? If not, you'll need shielding on the top of the chassis.

Does the hissing change when the guitar cable is removed from the amp? that could be your source of noise too.

I don't know your level of expertise, so pardon me if I'm asking redundant question you may have already considered.

hth

[DaveBo32]

BobI,
I did fine some loose socket terminals, so I bent them in a bit to cradle the tube better. The noise has subsided. I do need some form of cover. I was actually thinking about glueing some foil to the underside of the cab"s top section. I'll take a look around work, maybe I can find a aluminum grill that would fit. I have more experiance building pnuematic pcb test equipment than amps. Alot of the theory behind the tests and electronics is already figured out. Building this amp is teaching me alot about what actually is going on inside. When I build a test box that houses a transformer and powersupply, I usaully need to put a sheilding wall to isolate the power end from the function end to reduce unwanted noise. I was surprised an amplifier doesn't use this practice. I have alot to learn. I played some more with this amp and the sound seems to be improving everytime I use it. They are not kidding when they say you need at least 40hrs to break all the components in. You have been a real help.

Thanks,

[dogears]

metalized insulation foil tape from Home Depot works well.

Also, do not use that crappy shielded cable. Use the best stuff available. I do not even use 174. Go bigger! Keep it less than 30pf per foot. The 22 gauge stuff you have is probably close to 70pf per foot.

[BobW]

Steel window screen is what Fender used in the past. I simply staple the screen to the inside top of the enclosure, and overlap the edges to insure the chassis is making contact when bolted in. The foil tape works well too, as Dogears suggested.

Dogears, I use scrap MIL RG-174 from work since it's easier to manage, and the pF / foot (22pF) is reasonable. I would certainly like to use a lower pF cable. Any hints on what you use in particular is appreciated. I remember someone posting a while back about the cheap foam insulated RG-59?, as having good properties, but don't recall the pF value. Belden and Alpha wire seem to have a limited selection. thanks BobW