[jdkJake]

Quote:

for transformer requirements are we looking at
 
120/240 primary, 2x 30V secondary @ 500mA and 2 x 7V at 500mA?
 

2x 30V secondary @ 400mA, center tapped (30-0-30)  -- Note: Somewhat dependent upon transformer source
 
The heater can be wired for 6.3V or 9V, which, will drive the other spec. I built mine for 6.3V, hence the 2x 7V @ 500mA secondaries

 

[Cloud]

Thanks for the quick reply. Seems like i have to import some transformer into Singapore. Those available in Farnell Newark are seriously over spec.
 
this the closest i can find
 
Transformer,toroidal,160VA,0-230V pri 50/60Hz,2x0-30V sec
 
output current is 2.67A. I suppose this is not suitable?
 
Quote:

2x 30V secondary @ 400mA, center tapped (30-0-30)  -- Note: Somewhat dependent upon transformer source
 
The heater can be wired for 6.3V or 9V, which, will drive the other spec. I built mine for 6.3V, hence the 2x 7V @ 500mA secondaries

 

[jdkJake]

Quote:

Thanks for the quick reply. Seems like i have to import some transformer into Singapore. Those available in Farnell Newark are seriously over spec.
 
this the closest i can find
 
Transformer,toroidal,160VA,0-230V pri 50/60Hz,2x0-30V sec
 
output current is 2.67A. I suppose this is not suitable?
 

 

 
Ah, no.
 
Far, far too much current. You want something closer to 30VA.
 

 

[Cloud]

seems like custom is the way to go

 
Quote:

 
Ah, no.
 
Far, far too much current. You want something closer to 30VA.
 

 

[qusp]

Quote:

Been out of pocket for a few weeks, at least WRT to free time to stay caught up on the forums, but no problem, glad you like them.

 

They are usually sized to accept a 6mm hex bolt.  I bought stainless steel 6mm bolts from Lowe's for mine in the Liquid Gold. 
 


 

No shilling, Richard really goes out of the way to help and I think he bumped those EHHA units up a frame to keep the regulation tighter IIRC.  He's working on 3 customs for me right now and I have 5 more I need to order for other projects.  I know one is going up two sizes to really tighten the regulation since I have the room to fit a big 6" diameter can. 

 
I like Jack at Electra-Print too, but his bigger VA jobbies are just too costly and you need to set them out in the garage for a week to off-gas the varnish fumes.  Theory holds that toroids will pass all their noise through since they are wide band, but even with X10 home automation protocol sitting on my powerline at 120KHz, I can't hear any noise coming through my SumRs and I do not run filtered IEC inlets, I just use PowerCons.  I found a custom R-core winder, but they don't sell to individuals and they are nowhere near as easy to deal with as Richard.  Great custom R-cores and good service, but so far SumR has come out on top for me and he's so price competitive with the other two (R-cores and E-P) as well.  If I run into a noise issue, I'll go R-cores, but I have a PS Audio Solo now too, so I don't see that being necessary. 
 
 
And O/T, but my Tang Band drivers showed up yesterday from Planet10 Audio. 

  I haven't even opened the box yet though, been too busy. 

  

you can ask for the mounting hardware when you make the order. extra cost, but bugger all. 
 
haha yep the quality and looks inspire the want to go all out with them. they look mean. yeah I would like to try Jacks output TX the partial silver is interesting $$$$ but for power TX for the foreseeable future I can see Richard getting all the work. I just save up my orders and get them all at the same time to save on shipping. I definitely recommend against getting the canada post regular post, my first order too over 2 months to arrive, we thought they had gone missing. indeed concerns that are usually voiced WRT toroids dont apply it seems. i've used them with circuits that dont have the best PSRR and no problems as yet.
 
 
I do think he does test them all for each spec sheet, possibly once a winding is designed its that repeatable that the spec is the same. I know that all of mine usually come with sheets that match performance and pretty difficult to just make up numbers for a batch of custom orders. I suppose he could take a short cut with a large batch, but that doesnt really match with my impression of the man.

 

[runeight]

Quote:

Okay, amp is all warmed up. Let's try again:
 
Line Voltage at 122.1VAC
 
MOSFETS at 220mV:
   Rail PS Secondaries at ~31.2VAC
   Rail PS Regs at ~38.2V
 
Heaters at 6.295V:
   Heater PS Secondaries at ~7.3VAC
   Heater PS Regs at ~8.4VAC
 
Sound:
   Tight and tuneful
   Enjoyment factor at ~full tilt JAMMIN'

These are mostly good numbers. The line voltage is a bit high but so is the input to reg voltage for the rails. This means that there is room for the line voltages to be lower in other situations. But the heater input to reg does not have much room to go lower.
 
Cloud 30V @500mA or even 600mA would probably be ok depending on other conditions. Higher than this, however, will likely lead to voltages that are too high.
 

 

[jdkJake]

"Unexpected Distress from my Mistress"
 
So, after another 3+ hour marathon listening session while paying bills and whatnot last night (total of 8+ hours on the new transformer), I had something quite unusual happen. As I queued up the last song for the evening, a truely evil sound came from the left channel and the power LED's started a random pulsing. You could certainly tell some DC was making it though the left channel into the 650's as I struggled with that damn locking neutrik jack (now I know what I don't like about it) to free the phones. Not sure why I did not go for power first, need to make a mental note to change that behavior.
 
It was late, so I only took few measures. The problem is confined to the left channel only. Right channel board is fine. With no source input (fully attenuated), everything is more or less okay, but add the least bit of source and the DC offset jumps randomly between 0 and +/-250mV (possibly more, I did not latch it) on the left channel. All the power supplies seem fine, DC output from the rails and heaters was as expected (+/-30 and +6.3), MOSFETS remained biased at 220mV, however, the load at the Rail regulators was at ~28V. Recall I was seeing ~38V prior, so, something is certainly loading down the amp and drawing a ton of current.
 
It was late, so, I did not do much more besides check out the 650's on my miniMAX (they are fine, took it like a champ). I will take a look at it after work tonight and see if I can figure out what happened. Might be thermal related, but, seems unlikely as I had listened that much (and more) the night before without issue. I guess I will find out tonight.
 
Any suggestions where to start?

 

[sachu]

can you post readings from all pins of the opamp wrt SG.
 
Also can you try grounding the inputs to see if the offset goes away. 

 

[runeight]

If you can leave the amp on long enough:
 
Measure the opamp pins as sachu suggested.
 
Measure the voltage input to regulators. One or both might be toasted.
 
Don't know what else to suggest until you do more detecitve work.

 

[runeight]

Also, it does seem suspiciously related to a new transformer, but this can also be coincidence.

 

[runeight]

One more thing. Before you test the amp, separate the PS by pulling the jumpers to see if it is working properly.

 

[jdkJake]

Will do. Thanks for the suggestions.

Gonna have to be tomorrow though. Turns out my social planner has my evening committed.

 

[WyldRage]

I have some questions:
 
Is it still possible to substitute 6922 and 6H30 for the 6GM8? If that's the case, would jdkJake's tranformer be good for them? Or should I get more current on the 7V secondaries (at least for the 6H30)?

 

[ujamerstand]

For the 6H30, the heater transformer would definitely have to be beefed up, that's for sure. The heatsink on the heater supply would most likely need to be beefed up as well.

 

[runeight]

Quote:

I have some questions:
 
Is it still possible to substitute 6922 and 6H30 for the 6GM8? If that's the case, would jdkJake's tranformer be good for them? Or should I get more current on the 7V secondaries (at least for the 6H30)?

6922 yes, 6H30 no, as ujamerstand noted. The heater supply is just not hefty enough for the 6H30.
 
However, as you know, you can snap off the heater supplies and use a separate supply. One of the clever features of this design courtesy of the group effort.