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Dsavitsk/Beezar Torpedo Build Thread - Page 20

post #286 of 572
It looks to me like they put 6J6 guts in a bottle and labeled it a 5844.
post #287 of 572
Thread Starter 

Was it one of mine or someone elses?  The Beezar 5844's are all GE 5-star's, AFAIK.

post #288 of 572

Tom

 

Yours.

They all work great, I'm just confused about the tester results.

If I test them as a 6J6 the results make more sense but don't really match the datasheet.

 

Tres wierd......

post #289 of 572

Tried some Russian 6N15P.

They sound real good. Perhaps a little 'slower' than the CV4031's but I'll give them a little time to burn in.

post #290 of 572
Thread Starter 
Quote:
Originally Posted by dsavitsk View Post

I pushed for Salsiccia, but was overruled.
The slight mod I proposed to Tom is that we can beef up the CCS impedance a little. The CCS forms a voltage divider with the rp of the tube. The higher the CCS impedance and the lower the rp, the less power supply noise gets through. CCS impedance is basically
Hfe1 * Hfe2 * Re (Re is the current setting resistor (R4 and R5))
which is roughly 1M here. Good, not great. Actually, not really even that good. It is only about 50dB noise reduction. However, if we change out the top LED (D12 and D14) for say a 6.8V zener, then for the same current we need a 400R resistor [the current is (Zener voltage - 0.6) / Re], which bumps the impedance up to 6M which is 6x better (about 66dB of PSRR). The downside is that we have to drop an additional 5V across the CCS, which is not a big deal here.
With a 15V zener and a 1K resistor we get 74dB. However, the 15v Zener happens to be quite noisy, and will and up doing more harm than good. 6.8v seems to be a good quiet spot.
This is not a complete fix -- there is some noise that is PS noise getting through CCS that this will mitigate. However, the bulk of the noise seems to be noise from the transformer getting into the case and then getting into the circuit. Not sure how, but that's what is going on.
Also note that the Zener points the opposite direction of the LED, schematically speaking, with the cathode toward the positive marker on the PCB. If you put it in backwards you'll get very little current through the tube.

I've tried this mod a couple of times today - back and forth between the Zener, the 2nd LED, and the resistor (R4, R5) on each channel's CCS.  It seems to cut the noise by 1/2.  So, I would highly recommend it.  I will document it on the Torpedo website when I get a chance.

 

To be specific, I used 6.8V Zeners with RN60 402R resistors.

 

Meanwhile, I"m going to start selling full kits in the next day or so ... they will include the Zener mod to the CCS.

post #291 of 572

i know you said that the transformer is pretty much used full out, but i'm thinking about top-mounted tubes with 9-pin socket and wires to them from PCB. Then a choke on the PSU.
I know heater supply is pretty much maxed with 6J6 (~450mA) tubes - but if i used say ECC88 instead, where heater is only ~300mA - than that would probably be better for the hum that some people hear.
BUT is the main B+ able to deliver around 20-25mA/channel? or would that need a completely new transformer?


Edited by RollE2k - 1/5/13 at 6:38am
post #292 of 572
Thread Starter 
Quote:
Originally Posted by RollE2k View Post

i know you said that the transformer is pretty much used full out, but i'm thinking about top-mounted tubes with 9-pin socket and wires to them from PCB. Then a choke on the PSU.
I know heater supply is pretty much maxed with 6J6 (~450mA) tubes - but if i used say ECC88 instead, where heater is only ~300mA - than that would probably be better for the hum that some people hear.
BUT is the main B+ able to deliver around 20-25mA/channel? or would that need a completely new transformer?

I can't answer your specific question, but the Zener diode mod plus the choke has removed the hum for all but the most efficient headphones.  More than that, it has changed the character of the amp, IMHO.  I no longer care if I can hear some barely imperceptable hum - the amp is significantly more detailed, bass is tighter and deeper, etc. - IOW, all the good things one might expect from a much cleaner power supply are present.

 

Plus, Dsavitsk says we can remove the other CCS LED and replace it with another diode for even greater gains in S/N and PSRR.  I haven't tried that yet, but am so confident that this amp's sound is where we want it that I ordered another 500 tubes for stock at Beezar.  I'm going to order new cases and transformers soon, too.  Full kits will be available soon and I'm thinking seriously of offering built versions.

 

Combined with the pupDAC, whose frequency response greatly mimics the Torpedo (a very slight ~1dB drop off at 20KHZ), it's the best Grado sound I've had in my house.  I have the HF-1, HF-2, and a pair of SR-220's.  There's no tizziness, no "hot-enough-to-burn-your-ear" effects.  At the same time, bass is deep and punchy and cymbal crashes are smooth and distinct.  I find myself listening to the HF-1's because the highs are a bit more extended and clear than on the HF-2's.  (Some very gracious DIY Head-Fi members gave me the HF-1's for Christmas a few years ago.)  My HD600's with Cardas cable are almost identical sounding on the High-Z switch.  Which is why I've always said a Cardas cable on the HD600 turns it into a Grado with soundstage.  The HD580's, not so much, but then I've never liked the 650 cable it has (very dark).

 

(Before you think I've gone off the deep end, I don't believe in re-cabling in most cases, but cable improvements have always worked with the 580/600/650's.wink.gif)


Edited by tomb - 1/5/13 at 7:56am
post #293 of 572
Quote:
(Before you think I've gone off the deep end, I don't believe in re-cabling in most cases, but cable improvements have always worked with the 580/600/650's.wink.gif)

 

 

We'll just allow that you've accidentally fallen into the shallow end of the same pool. ;)

 

Sounds like great things happening in Torpedo land. I look forward to further developments and refinements. 

post #294 of 572
Quote:
Originally Posted by tomb View Post

Plus, Dsavitsk says we can remove the other CCS LED and replace it with another diode for even greater gains in S/N and PSRR. 

Oh no, I meant that you can use 2x 6.8 zeners in series to drop 13.2V, which will require a ~840 Ohm resistor. Leave the other LED where it is.

As for the power transformer, no, it will not do 20-25mA per side. Further, I don't think there is sufficient voltage headroom for running 6922's at that high of a current with the biasing scheme we use. However, running 6922's at 15mA with the 2 sides in parallel (so 7.5mA/side) will be fine. And, as you guess, the lower heater current will probably lower the noise a little. And, as Tom implied, the noise really is low. I have heard plenty of DIY and commercial amps that are noisier.
post #295 of 572
Thread Starter 
Quote:
Originally Posted by dsavitsk View Post


Oh no, I meant that you can use 2x 6.8 zeners in series to drop 13.2V, which will require a ~840 Ohm resistor. Leave the other LED where it is.

OK - glad you clarified that!

post #296 of 572

I see the 'short kit'

http://beezar.com/catalog/product_info.php?cPath=42&products_id=142

 

but it was mentioned a full kit was coming>  full, meaning I won't have to source all the remaining parts from mouser et al? Or am I misunderstanding the word 'full'......This looks like a sweet winter project for my grado's !  Pretty transparent and untubey sounding?

post #297 of 572
Thread Starter 
Quote:
Originally Posted by thelostMIDrange View Post

I see the 'short kit'

http://beezar.com/catalog/product_info.php?cPath=42&products_id=142

 

but it was mentioned a full kit was coming>  full, meaning I won't have to source all the remaining parts from mouser et al? Or am I misunderstanding the word 'full'......This looks like a sweet winter project for my grado's !  Pretty transparent and untubey sounding?

No, you didn't misunderstand.  I'm just behind ... as usual.  It'll show up this weekend, for sure.

post #298 of 572

sweet. thanks for developing this unique beast. reading from the site, there is mention of some attention needed for soldering on this type of board and possibly heating from both sides. Would a standard radio shack 15W iron and 60/40 .032" light duty solder be sufficient to put this together.....


Edited by thelostMIDrange - 1/11/13 at 8:50pm
post #299 of 572
Thread Starter 
Quote:
Originally Posted by thelostMIDrange View Post

sweet. thanks for developing this unique beast. reading from the site, there is mention of some attention needed for soldering on this type of board and possibly heating from both sides. Would a standard radio shack 15W iron and 60/40 .032" light duty solder be sufficient to put this together.....

The 15W soldering iron might be OK, but Radio Shack stuff is not always the best.wink.gif  I always recommend 63/37 eutectic solder.  Radio Shack sells it:

http://www.radioshack.com/product/index.jsp?productId=2062718&filterName=Type&filterValue=Solder#

I'm not sure what diameter that is, but it's 63/37, which is what's important.  Anything from 0.025 to 0.035 is probably OK.  I use 0.025, but then I use it for SMD soldering, too, and that's about as small as you get solder without it breaking on you all the time.

 

Just an FYI, but eutectic solder (63/37) is the single concentration mix where the solder mixture all has the same melting point - and also the lowest possible melting point of the alloy.  So the joint is automatically the best that can be made - all shiny with good contact, assuming you use the right heat:

http://en.wikipedia.org/wiki/Eutectic

 

One might ask, "Why make any solder that's not eutectic?"  "The pasty state of a non-eutectic solder can be exploited in plumbing as it allows molding of the solder during cooling, e.g. for ensuring watertight joint of pipes, resulting in a so-called 'wiped joint'." 

We're not interested in any of that with electronics, so eutectic is best.

post #300 of 572

thanks, found the info as well here and looks like something I could put together as you guys make it easy with all the step by step....... Will keep and eye out for the Full kit !

http://www.diyforums.org/Torpedo/TORPEDOoverview.php

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