Modded SB output level

Steve Eddy · « **Reply #20 on:** 31 Dec 2006, 12:52 am »

Quote from: Turk on 30 Dec 2006, 11:10 pm

Great deal on transformers. Thanks for the link. I'll save a bunch next time.

You're welcome.

By the way, do you know offhand just which Jensen transformers you're using now?

se

mgalusha · « **Reply #21 on:** 31 Dec 2006, 02:17 am »

Quote from: Steve Eddy on 31 Dec 2006, 12:52 am

By the way, do you know offhand just which Jensen transformers you're using now?

I'm pretty sure it's a Jensen JT-11SSP-JM (http://www.jensentransformers.com/datashts/11ssp6m.pdf) wired in a 1:2 configuration. Since it's mounted inside his amps, there are no issues with output cable capacitance. The Zin of his amps is 39K in parallel with 470pF, so the SB's DAC is seeing about a 5K load. I installed a switch so he can bypass the transformers if desired. His amps have a voltage gain of 20 (26dB), so with the 0dB output voltage of a modded SB at just over 1VRMS, the amps won't reach full power. Of course with the extra 6dB of gain he has enough voltage to drive them to clipping as would a normal preamp. Some caution must be exercised. IMO the transformers do a great job, especially on recordings with a low average level.

Didn't mean to hijack your thread Wayne.

Mike

Steve Eddy · « **Reply #22 on:** 31 Dec 2006, 03:34 am »

Quote from: mgalusha on 31 Dec 2006, 02:17 am

I'm pretty sure it's a Jensen JT-11SSP-JM (http://www.jensentransformers.com/datashts/11ssp6m.pdf) wired in a 1:2 configuration.

Ah, thanks.

Quote

Since it's mounted inside his amps, there are no issues with output cable capacitance.

Well, given what you say next, cable capacitance would be the least of one's worries.

Quote

The Zin of his amps is 39K in parallel with 470pF, so the SB's DAC is seeing about a 5K load.

The recommended minimum 5k load in the datasheet is for a resistive load. The maximum load capacitance is 50pF. So not only is that 470pF over nine times greater than the maximum recommended load capacitance, that 1:2 transformer is going to increase that 470pF by a factor of four, which means that even before you add the cable capacitance to that, the DAC's driving a capacitive load of about 1,880pF.

Any chance you could clip that cap out of the circuit?

se

mgalusha · « **Reply #23 on:** 31 Dec 2006, 01:08 pm »

Quote from: Steve Eddy on 31 Dec 2006, 03:34 am

Any chance you could clip that cap out of the circuit?

Possibly but the I can say that even with the load presented to the DAC in the SB doesn't have any issues sound wise. I am not going to mess about with the circuit of his amp especially give how good his setup sounds. I've read the data sheet as well and can't offer a good explanation as to why it works as well as it does but it does sound very good.

Mike

Steve Eddy · « **Reply #24 on:** 31 Dec 2006, 05:07 pm »

Quote from: mgalusha on 31 Dec 2006, 01:08 pm

Possibly but the I can say that even with the load presented to the DAC in the SB doesn't have any issues sound wise. I am not going to mess about with the circuit of his amp especially give how good his setup sounds. I've read the data sheet as well and can't offer a good explanation as to why it works as well as it does but it does sound very good.

Fair 'nuff.

se

Wayne1 · « **Reply #25 on:** 31 Dec 2006, 05:30 pm »

Steve,

The coupling capacitors used in the modded SB are 3.3uF to 4.7uF depending on the model of the SB.

Thank you for all your information and help on this and the thread in the Lab.

Steve Eddy · « **Reply #26 on:** 31 Dec 2006, 06:26 pm »

Quote from: Wayne1 on 31 Dec 2006, 05:30 pm

The coupling capacitors used in the modded SB are 3.3uF to 4.7uF depending on the model of the SB.

Thanks, Wayne. That may be rather on the small side. I haven't used any output trannies on cap coupled outputs, but I seem to recall Dale over at Jensen some years ago recommending something more like an order of magnitude greater than what you're using.

I've got a CineMag CMOQ-1 and some 2.2uF AudioNote caps laying around here somewhere. I'll run a sweep on that combo sometime today and see if there's any low frequency peaking. If everything's cool with 2.2uF, there won't be any problems with what you're using.

Quote

Thank you for all your information and help on this and the thread in the Lab.

You're welcome. Been fun.

se

Steve Eddy · « **Reply #27 on:** 31 Dec 2006, 09:37 pm »

Ok...

With a 150 ohm source impedance coupled through a 2.2uF cap, the CMOQ-1 wired 1:2, and no load on the secondary, I got about a 7dB peak at around 20 Hz, which didn't settle down to reference level (at 1kHz) until about 70 Hz.

With a 220k load on the secondary, the peak dropped down to about 4-5dB, and with a 22k load on the secondary, it was down to just a fraction of a dB.

se

Daygloworange · « **Reply #28 on:** 3 Jan 2007, 07:34 pm »

How's progress Wayne? Any news?

Cheers

Wayne1 · « **Reply #29 on:** 4 Jan 2007, 01:17 am »

I have not received any of the buffers that have been shipped to me, yet.

I have assembled the buffer circuit I was planning but it is a long way from any kind of finished product.

Steve Eddy · « **Reply #30 on:** 4 Jan 2007, 06:41 pm »

While you're waiting for the glass buffer, and if you're not allergic to sand, here's something ultra simple you can play around with in the meantime if you'd like.

If you're going to use the SB for volume control, a fixed 100k resistor will give you a good high impedance for the cap coupled output to drive. The follower's output is DC coupled so no worries about low frequency resonance with the output trannie, and with it wired 1:2, you get your 6dB of voltage gain.

What really "makes" this is the Crystalonics CD-860. It's the sweetest dual JFET on the planet as far as I'm concerned and I wouldn't even consider building such a simple circuit with anything else.

Anyway, a couple of caps and a couple of 7Ah SLAs and you're off to the races.

se

Wayne1 · « **Reply #31 on:** 13 Jan 2007, 12:53 am »

The Burson Buffer arrived today from Down Under

After letting it warm up a couple of hours from the 2 degree F. temp here, I put in into my office system.

OH MY

There is all the gain anyone could want.

The low end is VERY extended. Mids are dynamic. Highs are very clean.

I will let it run over in the weekend and do some more comparisons. Right off the bat, I do feel it sounds "better" than the Eastern Electric BBA.

I do not notice much "loss" in signal quality compared to the direct SB output. There IS a lot more gain to the system.

The only downside, at first glance, is the casework quality (like I should talk) and the VERY bright blue LED on the front. All of which, I am sure, can be worked out.

While it does not invert polarity in it's shipped form, it can be made to do so.

More later.

GHM · « **Reply #32 on:** 13 Jan 2007, 01:45 am »

Quote from: Wayne1 on 13 Jan 2007, 12:53 am

The Burson Buffer arrived today from Down Under

After letting it warm up a couple of hours from the 2 degree F. temp here, I put in into my office system.

OH MY

There is all the gain anyone could want.

The low end is VERY extended. Mids are dynamic. Highs are very clean.

I will let it run over in the weekend and do some more comparisons. Right off the bat, I do feel it sounds "better" than the Eastern Electric BBA.

I do not notice much "loss" in signal quality compared to the direct SB output. There IS a lot more gain to the system.

The only downside, at first glance, is the casework quality (like I should talk) and the VERY bright blue LED on the front. All of which, I am sure, can be worked out.

While it does not invert polarity in it's shipped form, it can be made to do so.

More later.

Very cool Wayne!! Glad to see you give the Burson buffer a whirl.

I believe I was one of the first in the United States to have this unit. I'm happy that someone of your experience, hears what I heard when I dropped it in the system.Yup..the case ain't pretty

that's for sure!! But it does sound pretty darn good doesn't it.

Nuuk · « **Reply #33 on:** 13 Jan 2007, 01:05 pm »

Wayne - did you get my email re the Burson Buffer?

(Nick)

Wayne1 · « **Reply #34 on:** 17 Jan 2007, 11:23 pm »

Nuuk,

I do not see any PM or mail from you.

I may have accidentally deleted it

I have been letting the Buffer run in for a few days.

It DOES change the sound of my system. I believe it is for the better.

The balance of the tone has shifted lower.

The highs are less prominent and the bass is more forward. The low end is VERY tight and extended.

It is more pleasant to listen to.

I am sending the Burson Buffer, a power cable, some speaker cables and interconnects up to Toronto for them to use in their amp comparison next weekend.

Hopefully Denny and the others will comment on their impressions of the Burson Buffer and the cables.

Nuuk · « **Reply #35 on:** 18 Jan 2007, 11:12 am »

Wayne, I have PMed you.

bpape · « **Reply #36 on:** 18 Jan 2007, 12:14 pm »

Will definitely be looking forward to other impressions about the BB. Sounds like you really like it Wayne.

Bryan

Wayne1 · « **Reply #37 on:** 18 Jan 2007, 04:23 pm »

Bryan,

I DO like it.

There are somethings that could be better, but I do like what it does for the sound of this system I had it in. I have heard bass extension that I didn't know these speakers could do.

When I get it back from Toronto, I may poke around inside it a bit.

Daygloworange · « **Reply #38 on:** 24 Jan 2007, 06:38 am »

I received the Burson Buffer earlier today from Wayne. Got home late, but just had to plug it in. Right off the bat, the resolution went up quite a bit. ( I was running my Bolder modded SB 3 into my Adcom pre amp to get a little more output).

I'll write a little more when I get the chance to give it a more critical listen and give more details, but just wanted to comment briefly. While right off the bat, I don't think it has as much gain as my pre, I agree with Wayne that for most situations it is probably more than enough gain.

I've also been playing with running my SB 3 through the Eastern Electric BBA, my Adcom pre, and now through the Burson. The nod goes to the Burson.

To be continued....

Cheers

bprice2 · « **Reply #39 on:** 21 Feb 2007, 04:23 pm »

This is an interesting thread. Are there any update?

Wayne, if I understand what I've read, you were seeking a solution that would add gain to the modded SB output and in the process discovered that adding a buffer not only increased gain, but also added better impedance matching, which improved sonics. Do I have this right? Also, are you looking to mod the Burson Buffer, or create your own?

Thanks.