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quote:

[By Guitarsenal] Blooze,

There may be a mistake in your power supply drawing. You are putting the entire power supply after the filimant dropping resistors. That might be a bad thing.

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Good call! Can't believe I missed that. That's why I like to have stuff checked first.

Let's try again:

http://pg.photos...inger/my_photos

i am planning to use a 22-0-22 transformer.. so the DC voltage heading to the plate ccs will be approx. 80~90VDC. the question is about ccs.. among other variations, i think Mains Hhum's version is the one that i am actually gonna build because 2n2907 is readily available where i live. is it ok to load 80~90 DCV on the ccs?

[Edited by ryanjun on 11-17-2005 at 10:48 AM.]

Do you have a part number for the full wave bridge rectifier? I was overwhelmed by the sheer number of rectifiers at Mouser, and saw that most of them aren't full wave.

If I build my bridge rectifiers from diodes, what would be the minimum rating of the diodes? For example, can I build the rectifiers out of 1N4148 diodes? Those diodes are rated at 150ma, and the speced bridge rectifier is 100ma, so it seems like it would be OK.

Thanks!

[Edited by Guitarsenal on 11-17-2005 at 01:09 PM.]

http://www.mouse...ld&N=0&crc=true

In the parts list you posted a page back, the positive voltage regulator you ordered is a surface mount (SO-8) device.

I don't see any of the 1/8 Watt resistors, I presume they're already in your parts box.

You should include a DIP socket so you can roll OPAMPS. As runneight said earlier, the OPAMP you've ordered will load the tube more than the one we originally used and may cause more distortion. It's good to be able to switch and find out if this makes a difference in the real world.

I'll be posting a complete parts list, with Mouser and Digikey part numbers, this evening.

[Edited by Batman on 11-17-2005 at 02:07 PM.]

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quote:

[By Batman]

I'll be posting a complete parts list, with Mouser and Digikey part numbers, this evening.

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WONDERFUL thanks!

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quote:

[By ryanjun] i am planning to use a 22-0-22 transformer.. so the DC voltage heading to the plate ccs will be approx. 80~90VDC. the question is about ccs.. among other variations, i think Mains Hhum's version is the one that i am actually gonna build because 2n2907 is readily available where i live. is it ok to load 80~90 DCV on the ccs?

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ryanjun, although this is not a bad idea to get more B+ on the tube, using this transformer will cause some other issues with the amp.

First, the heater dropping resistors will dissipate much much more power. You'll have to recalculate their values before you wire up the 12AU7. I'm sure that you've realized this, but just in case.

Secondly, the input to the 12V regulators might exceed their 35V limits depending on the regulation of the transformer. You could just blow them out. If the trafo regulation is 25%, then the actual voltage could be between 22-0-22 and 27.5-0-27.5. When the trafo is unloaded it will be at the higher value. The rectified value of 27.5V is almost 39V. Should you power up the amp with no tube, the regulators will blow. And depending on its current rating, you still might have overvoltage with the tube plugged in. Something else to consider.

Third, the 470u/35V caps must be rated at at least 50V to account for very poor regulation in the trafo. If the regulation is worse than 25% the voltage spec might need to be raised.

The BJT CCS as designed in Main's amp will not work. I would recommend the LND150 CCS that is in Batman's amp if you can get the LND150s. You can use two LND150s in a cascode to get a better CCS than the BJTs can do. In the basic stupid diagram, just replace the J113s with LND150s. We can figure out the resistor later.

I don't mean in any way to be negative about this idea. I just wanted to point out a few of the things you 'll need to consider if using that trafo.

May I ask why you want to use the 22-0-22 transformer?

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quote:

[By Batman] Here's the bridge that mains_hum and I used.

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Thanks!

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[By Batman] In the parts list you posted a page back, the positive voltage regulator you ordered is a surface mount (SO- device.

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D'Oh!

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[By Batman] I don't see any of the 1/8 Watt resistors, I presume they're already in your parts box.

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Yup. I already have a large assortment of 1/8 watt resistors.

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quote:

[By Batman] You should include a DIP socket so you can roll OPAMPS. As runneight said earlier, the OPAMP you've ordered will load the tube more than the one we originally used and may cause more distortion. It's good to be able to switch and find out if this makes a difference in the real world.

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Definitely! I just ordered the part you used from Digi-Key, so I will try them both and report back.

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quote:

[By Batman] I'll be posting a complete parts list, with Mouser and Digikey part numbers, this evening.

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Great! Thanks again,

KP

[Edited by Guitarsenal on 11-17-2005 at 08:00 PM.]

If you would rather have the original spreadsheet with live links for the part numbers, it's attached to the at the bottom of this message (C1272.xls)

Also, by next week I'll have two PCB images, one for the PSU and one for the audio section. I just need the time to populate the boards and make sure they work.

[Edited by Batman on 12-30-2005 at 11:38 PM.]

i wanted to use 22-0-22 transformer b/c there's going to be a parts groupbuy with 22-0-22 talema transformer here in HAS, korea for a some other amp. well, it seems to be much wiser for me to reconsider the idea. however, few more things to answer just in case.. the heater voltage was the pain in my ass all last night, and u made it much more clear for me.

right now, am planning to put a pair of LT1033/1085 regulators for the dual power supply b/c they are in the groupbuy part list anyways, so it'll be 3A each. what if i reticify the already reticified 15-0-15DCV thru lt1033/1085 with two 6V regulators--perhaps lm317/337--to disperse the dissipation heat and get 12V across the 6-0-6 dual supply.. will this work?

btw, i couldn't find any suppliers for lnd150.. can u recommend any other substitute parts other than ln150?

thanks for the answer again.

All regulators have a maximum voltage difference that they can sustain between the input and the output before they breakdown. The 22-0-22 trafo will probably exceed this voltage under some conditions. The current rating of the regulator doesn't matter when exceeding this spec.

Can you get a 30VCT/200mA transformer anywhere? The build will be much easier if this is possible.

For the CCS, we can use DN3545 mosfets too. Can you get those? However, if you build the regular SOHA, you can use Main's BJT CCS.

We tried to make the components list as universally available as possible around the globe. Are J113s really not available to you? If not, there are other jfets that could be used here.

Leocom (http://www.leocom.co.kr/) is the Korean agent for Farnell. You should be able to order the Dagnall D3011 transformer from them. It's Farnell Order number 159384

batman, most of farnell's prices are too expensive comparing with other suppliers in korea. a decent and ceter-molded 25VA toroidal trafo is only about $13 here in korea. thank you anyways.

[Edited by ryanjun on 11-17-2005 at 09:59 PM.]

A year ago i bought 50 10,000 MCD 3mm blue leds direct from Chi Wing's ebay store for $11.50 shipped - 23 cents each. (cwithk fwiw).

Arrived in about 12 days and they pass my only two qualifiers for led quality - they don't melt and the color is consistent.

And I will sell them to you for only, uh, 75 cents each, yeah, that's it.

(fwiw, 10kmcd is way too bright for most applications, i end up using somewhat high values of resistors to dim them. For example, I had a remote control opened up to clean stickyness off the board and decided to replace that dull old played out red LED with a blue one - and I now have a gag remote control that blinds the user)

I've seen at least one project where a UV led was used. I think it maybe looked cooler in the picture than it looks in person, all uv does to vacuum tubes here is make the insulators glow a little.

I don't understand the diode that is across the LED in this circuit. Is that necessary to run a LED on AC?

But, if you use a high bright LED and throttle it down to a few mA or less than 1mA, the bipolar supply will not notice it.

The diode in reverse parallel with the LED protects it from too high reverse voltages, as you say. With the 1N4148 the maximim reverse voltage that the LED will see will be one diode drop. All LEDs that I know about can withstand this.