[drtechno]

Thanks. Yeah, I did what you described - curled it around and soldered. I've tested the continuity from one solder point to the other without touching the multimeter to the wire, just the tab to ensure that there is current flow from the tab, to the wire, through the wire, to the next tab. I can't find a gap anywhere.

I also jumped from the back of the RCA jacks past the volume pot straight into the input tube (IE Very loud) and I am still having the same issue.

Ok, lets troubleshoot: What are the cathode voltages on both channels on both tubes?

 

[bigfatpaulie]

Thank yo so much for talking the time to help me: I really appreciate it!

You will have to do a little hand holding here, however. I'd rather use terminal numbers (eg, A3 or B2) as I don't have the confidence to know exactly which terminal to test when you say cathode voltages (thought I suspect A4, A9, B8 and B7).

 

[drtechno]

where's a schematic? here is the preamp tube pinout:

and your output: [IMAGE REMOVED]
so #3 and #8 on the preamp tube, #3 and #6 on the output tube.

BTW, these pictures are from the pin/soldering side (if you didn't know that)

is it this poorly designed one here? [IMAGE REMOVED]

2018-07-13 1121 EDT MODERATOR NOTE: Images removed at the request of the copyright holder.

 

[bigfatpaulie]

Here are the labels:

[IMAGE REMOVED]

Just to be clear, I would be measuring DC from (for example) A1 to the grounding tab, correct?

2018-07-13 1124 EDT MODERATOR NOTE: Images removed at the request of the copyright holder.

 

[drtechno]

Correct,
This translates to A3 and A8, B3 and B6. And yes, you would measure DC from the grounding tab to the points.

btw, this looks like this constant current source:

 

[bigfatpaulie]

Thank you and no problem:

A3: 1.53
A8: 1.53
B3: 137.6
B6: 103.7

 

[drtechno]

lol I found their manual... yes it is that poor design... too bad its too big to post at once, but page 7 would be ok.
this schematic they have in the manual is for a ac heater system. By what other said in the thread they used a 9V heater winding, which would be typical if they went DC with the design to curtail the poor power supply noise rejection.

 

[drtechno]

Thank you and no problem:

A3: 1.53
A8: 1.53
B3: 137.6
B6: 103.7

tube A ok, tube B, the section B3 is not biased. Check your circuit in b3 for opens.

 

[bigfatpaulie]

tube A ok, tube B, the section B3 is not biased. Check your circuit in b3 for opens.

Interesting. Okay. But you will have to spoon feed a little bit here; what in a piratical sense, does "Check your circuit in b3 for opens" mean?

 

[drtechno]

somewhere in the circuit, from B3 to ground is not connected. so the tube is exhibiting the plate voltage (or near plate voltage) on the cathode, because its not conducting (fully). I would check the transistor's ground connection. R1 to ground of the constant current source board, and test the transistors (you don't have to pull them out in this circuit). Since its brand new, its not unheard of a 2n2222 to be bad brand new, thats why they are cheap (under a $1 each) and the tip50 is about half of that price. Could be bad solder joints and or wire connections too...

 

[audiowize]

is it this poorly designed one here?

Posting a manufacturer's design on here and making claims about its noise performance with no measurements is "bad design". (where are your designs btw?) Hopefully a moderator will enforce copywrite rules on this one.

DC heating will not have any impact on power supply noise rejection, that's what the HV filtering is for.

To the OP, I think drtechno may have imbibed excessively at club last weekend, you'd be better off looking for help elsewhere.

 

[Doc B.]

I don't bother with this stuff usually, but your mistake is posting Bottlehead copyrighted IP without permission. Mods have been notified of your copyright violation. If you really want to improve your stature by denigrating my work don't take cheap shots on a forum, take me on in the street. Start an audio company, put out some of your own designs instead of stealing others, prove yourself regarding product support, surround yourself with a talented staff who are technically competent, capable of good designs of their own and have a reputation for some of the best customer support in the industry. Sell thousands of kits, millions of dollars of product over the years, earn hundreds of repeat customers. Earn respect from industry peers, get some great reviews, take a few best sound awards at trade shows along the way, sell some gear to Grammy winning recording engineers. While you are at it start a record label, revive a format. Get requests from those Grammy winning engineers for technical assistance in their recording sessions, get some album credits. Find yourself approached by some manufacturers to license your designs to them, and by others to offer service for their products. Grow the business for 25 years, put a couple of kids through college with it. Because right now son, you're not walkin' the walk, you're just talkin' the talk.

 

[Paladin79]

Very well said Doc.

 

[drtechno]

Posting a manufacturer's design on here and making claims about its noise performance with no measurements is "bad design". (where are your designs btw?) Hopefully a moderator will enforce copywrite rules on this one.

DC heating will not have any impact on power supply noise rejection, that's what the HV filtering is for.

To the OP, I think drtechno may have imbibed excessively at club last weekend, you'd be better off looking for help elsewhere.

btw the design is older (1954 General Electric) than the company is and is a common circuit now. The design flaws of dc coupling without grid-stops was always been a topic off and on for decades with this circuit. Other flaws with this circuit is that it has no power supply rejection and all power supply and heater noise will be present on the output. The reason why they went to dc heaters is the fact that it takes a very high quality heater winding and a voltage regulator is cheaper than the high quality winding with a center tap that does not distort near center crossing under load. Vox AC30 has one in it btw...

The one design variant I like is that German guy that did it for McIntosh (patnent 1955) that is the same circuit John Brooskie markets as the Akido amp.

 

[atomicbob]

There is nothing "poor" about Doc's heater design. Here are dScope measurements for my Crack, which is close to original, non-speedball, though it does have the high voltage PS choke mod.
Please note these are UNWEIGHTED noise measurements. No A-weighting to make 60 / 120 / 180 Hz noise appear better than reality as is often published in manufacturers' specifications.

Those are damn decent figures for an all tube amplifier. Many manufacturers prefer not to list such as they struggle to achieve -78 ~ -80 dBr.

And here is a picture of how I enjoy my Crack: