Op Amps for Eastern Electric Minimax DAC

MarkM · « **Reply #20 on:** 8 Feb 2011, 02:09 am »

Quote from: mfsoa on 25 Jan 2011, 06:43 pm

C'mon peeps, spill your op-amp secrets! What else is a good swap for the I/V stage? (OPA2134 is on the way). The SS output? (OPA627 is on the way too)

OPA827?

Liked the Psvane tube in the dac and ordered one for it.

-Mike

So Mike, what combo did you settle on? Can you comment on the OPA627 sound? A friend is going to loan me a pair of OPA627 for the ss output and I have some OPA1612 for the I/V.

I need to try the Psvane tube most are raving about.

richidoo · « **Reply #21 on:** 18 Feb 2011, 03:44 pm »

The original Signetics 5532 sounds better that the current production versions.
http://cgi.ebay.com/Signetics-Former-Philips-NE5532-NE5532N-Opamp-RARE-/260731575378

I prefer LM833 to LM4562 even tho specs are not as good. The circuit is pretty simple for a modern opamp.

Some older opamps like TL072 can sound good because they are simpler circuits. They are not as quiet or fast as modern super opamps, but audio frequencies don't need MHz speed, any opamp makes enough bandwidth for audio.

2134 sounds good, but it has an emphasis in the upper mid presence range, making an alive, exciting sound that can become annoying after a while. This sound appeals to some people, but listen for it if you try this opamp.

Be careful of oscillation when swapping opamps in any circuit.

mfsoa · « **Reply #22 on:** 19 Feb 2011, 02:09 am »

Mark,
I ordered some 2134s at your recommendation, but then ordered some OPA2107 which actually arrived first (UPS wouldn't venture down my driveway for a week due to snow!) I put the 2107 in and really liked it so I haven't tried the 2134.

The OPA627 in the SS output does some things amazingly well - great bass with a very involving, draw you in sound. Powerful and clear with very nice midrange. But on many tunes, there just isn't quite enough sparkle when combined with the 2107. Too much of the "Burr-Brown sound" I guess. But it sounds great this way w/ classical, and with many many other sources but definitely the sound is tilted down relative to the LME49710. Its (the 627) actually a somewhat strange yet wonderful sound - somehow rolled on top, yet with tons of midrange detail/joy/glory/articulation. I think this why the sound makes you want to listen - It's like someone speaking softly which makes you listen with greater attention, if that makes sense. OMG the bass though - fabulous. Yello "The Eye" sounds incredible. Everything is very listenable, but everything shouldn't be very listenable. Or should it?

So what next? So far I like the 2107 feeding the tubes and since it feeds the SS also, maybe I need to get a little more lively chip than the 627. OPA827? AD825? Seems like more and more chips aren't coming in DIP8 and so need adapters.

It'd be great if we could increase the pool of op-amps that we can try in this pup, so people let's hear what's worked and what's blown up!

What I don't understand is what cap options I have now, if I use FET-input op-amps...

-Mike

Bill O'Connell · « **Reply #23 on:** 19 Feb 2011, 03:19 am »

ok you op-amp rolling fanatics

Wait!
Doug Schroeder from Dagogo.com has been rolling about a dozen of these new hi-tech op-amps that he says are just phenomenal. He has published articles about this at Dagogo but these new op-amps that he is trying he exclaims the previous articles on a 1-10 scale have been about a 2 compared to these new super op-amps. I'm not sure when he will be publishing his findings but visit there often as these are the ones to use. I trust his ears and I know he has put a ton of work putting to pen his explorations. He has tried all kinds of combinations and as thorough as this gentleman is, we will all benefit from his knowledge as to what to try and use.
Patience is a virtue.

Later,
Bill

satfrat · « **Reply #24 on:** 19 Feb 2011, 03:33 am »

Quote from: Bill O'Connell on 19 Feb 2011, 03:19 am

ok you op-amp rolling fanatics
Wait!
Doug Schroeder from Dagogo.com has been rolling about a dozen of these new hi-tech op-amps that he says are just phenomenal. He has published articles about this at Dagogo but these new op-amps that he is trying he exclaims the previous articles on a 1-10 scale have been about a 2 compared to these new super op-amps. I'm not sure when he will be publishing his findings but visit there often as these are the ones to use. I trust his ears and I know he has put a ton of work putting to pen his explorations. He has tried all kinds of combinations and as thorough as this gentleman is, we will all benefit from his knowledge as to what to try and use.
Patience is a virtue.

Later,
Bill

Here's Doug Schoeder's article which has already been updated once a month ago.

Cheers,
Robin

richidoo · « **Reply #25 on:** 19 Feb 2011, 05:26 am »

"Custom" opamps?

MarkM · « **Reply #26 on:** 24 Feb 2011, 12:34 am »

Thanks for sharing. I have to say that the OPA627 is a great IC. Combo I am currently liking is LME49720/OPA627. The LME49710 in the ss output is not as involving as the 627. The 627's present the music with a bit of warmth, very involving compared to the NE5534 or the LME op amps.

Agree with Mike in describing the sound of the 627 "with tons of midrange detail/joy/glory/articulation"

Also picked up a Genelex 12au7 and prefer that over the Mullard that was a mainstay.

Up next:

1. Pull the board and replace all of the diodes with shottky type(Cree for HV-tube p.s.)
2. Upgrade the electrolytics and bypass them with orange drops under the board.
3. Have some Sonic Caps collecting dust in my old dac(Dac 60) for the coupling. 3.3uf
4. Shunt regulators from Tentlabs.
5. More film caps.

Realestate is tight in this thing to get a stepped attenuator in place of the alps or might just bypass the pot.

This dac is very impressive for the $$$$$$!!!!

Shahrose · « **Reply #27 on:** 15 Mar 2011, 09:19 pm »

I'm eagerly awaiting Doug Schroeder's new list of opamps. Not sure when he's going to update his article and provide us with some names.

MarkM · « **Reply #28 on:** 18 Mar 2011, 09:20 pm »

Quote from: Shahrose on 15 Mar 2011, 09:19 pm

I'm eagerly awaiting Doug Schroeder's new list of opamps. Not sure when he's going to update his article and provide us with some names.

Rumour is Doug liked another National Semi op amp. Only rumours, Dac owners have been checking in with Clarity Cable in an attempt to get the inside scoop.

Available from Digikey or you can get it premounted from Cimarron Technology. No dual channel available.

http://cimarrontechnology.com/single-to-dualop-ampadapterpn020302.aspx

http://www.national.com/ds/LM/LME49990.pdf

Wayne1 · « **Reply #29 on:** 18 Mar 2011, 09:48 pm »

He has moved beyond those op-amps now

http://www.audioasylum.com/audio/digital/messages/15/157346.html

PeteG · « **Reply #30 on:** 19 Mar 2011, 12:32 am »

I’ve been using a paired LME49990 on a BrownDog Opamp adapter in the I/V stage, by far it’s the best sounding Opamp that I’ve tried. I am using it with a Genalex (Gold Lion) tube but haven’t had time to try any other tubes.

MarkM · « **Reply #31 on:** 22 Mar 2011, 12:38 am »

Quote from: Wayne1 on 18 Mar 2011, 09:48 pm

He has moved beyond those op-amps now

http://www.audioasylum.com/audio/digital/messages/15/157346.html

Wow, there is quite a buzz about What Doug's personal favorite will be. Great little DAC!

Wayne1 · « **Reply #32 on:** 25 Mar 2011, 03:28 pm »

Dagogo article on op-amp rolling

Doug has finished his article on op-amp rolling.

I do not completely agree with his choices, but everyone's system is different. It is worth pointing out that the position of the volume control will change the sound of the DAC and thus your choice of op-amps.

With the volume control taken out of the circuit, I prefer the sound of the LME 49990 in the solid state output. I do NOT care for the AD797 in this position.

The Dual LME 49990 and the AD2604 are both very nice in the I/V section. I have experimented with some mods to the LME 49990 that add a bit more punch and extension.

Do remember that op-amp rolling will void any warranty.

JLM · « **Reply #33 on:** 25 Mar 2011, 06:59 pm »

Thanks for the link Wayne.

I've liked and respected Doug's work for years.

So to add to the complexity, what combination of tube, fuse, and Op Amps sound the best?

Occam · « **Reply #34 on:** 25 Mar 2011, 08:34 pm »

Quote from: Wayne1 on 25 Mar 2011, 03:28 pm

Dagogo article on op-amp rolling

Doug has finished his article on op-amp rolling.

Wayne,

Thanks for the link! Only after looking at the standard pin-outs on single and dual opamps (lacking actual schematics) did it truly reveal itself as a Mad Hatters Tea Party.

Wayne1 · « **Reply #35 on:** 25 Mar 2011, 09:11 pm »

Quote from: Occam on 25 Mar 2011, 08:34 pm

Wayne,

Thanks for the link! Only after looking at the standard pin-outs on single and dual opamps (lacking actual schematics) did it truly reveal itself as a Mad Hatters Tea Party.

I was trying to be nice, Paul

I would not suggest that anyone follow Doug's switching of single op-amps for duals or the other way around. As Occam's diagram shows, they are not compatible. The single op-amp would be running off of just the negative supply with the output signal going through the feedback loop. Half the input signal from the DAC chip would be missing.

In fact, if you tried to use a dual in the single op-amp position, there would be full rail voltage on the output. It is only because there is an electrolytic coupling capacitor in the solid state signal path that changing the op-amps out didn't cause major problems. If that cap failed, or if this change was tried in one of my modded units, you could blow your speakers.

Doug's suggestion of particular brands and models of op-amps are fine. I cannot stress strongly enough that you do not swap singles for duals or duals for singles. If you try that in a modded EE DAC, you will be on your own. I will not repair the resultant damage.

*Scotty* · « **Reply #36 on:** 25 Mar 2011, 09:44 pm »

This may be a silly question,but will the tube output still work if the op-amp for the solid state output is not present. The output of the IV stage would only see the input impedance if the tube output stage. This might be of some benefit if the both the tube and solid stage outputs are live at the same time. It would raise the impedance the IV stage op-amp has to look at. I don't know if the IV stage op-amps sound better if they see higher impedance load at their output or not.
Scotty

Occam · « **Reply #37 on:** 26 Mar 2011, 06:47 am »

As a PS to the Dagogo article on op-amp rolling
I believe the AD8620 as a proper single opamp must be a misprint, with the author actually using the AD8610, a single opamp with the appropriate pin-out, as opposed to the dual AD8620, which would, in technical parlance, go all hinkey, and possibly, let the smoke out.
[Wayne - are the rails on the EE within the AD8610 +-13 volt rail limits?]

Dagogo said-

Quote

The [OPA]627 was a very surprising Opamp, as it was not expected to perform at top level. My understanding is that it is an older Opamp design, so it should be more economical.

I can only hope that in MY dotage, I am accorded the same value and justified respect as the OPA627. A major reason for subsequent, similar chips is that the OPA627/37 is expensive to fabricate. Its far worse for discrete JFETs no longer made by Toshiba that are becoming like NOS vacuum tubes.
Dang whippersnappers

bravophase · « **Reply #38 on:** 26 Mar 2011, 07:36 am »

Hi Guys, the NE5532 and its sub(dual) and NE5534 and its sub (single) are not compatible to each other. If you plug in the dual opamp to the sigle opamp place, and vice versa, it may damage your DAC.

Cheers !

Alex

mfsoa · « **Reply #39 on:** 26 Mar 2011, 01:34 pm »

Yup the article is riddled with mistakes.

I also think he may have a fundamental misunderstanding of how the op-amps are implemented- Isn't it the case that when using the tube output, you ONLY use the duals in positions U1/2, and when using the SS output, you are using all 4 op-amps?

Yet he says he primarily listened to the tube output, and consistently discusses the sound quality of sets of all 4 op-amps.

And discusses differences in SQ where only the U6/7 op-amps are switched, which would have no impact on on the tube output at all

I told him via email that therefore, unless he specifically states whether he was using the tube or SS output when describing what he was hearing, the reader has no idea of what op-amps he is actually talking about. This of course renders the article meaningless as far as helping an EE DAC owner to understand what changes to anticipate, and actively misdirects someone's efforts who may only be concerned with the tube output by making them think that the U6/7 chips are playing a role in the SQ.

He needs two separate tables- One for the U1/2 op-amps listened via the tube output, and a second for combinations of all 4 op-amps listened via the SS output. As is, the single table is completely meaningless if the tube output was used.

We'll see if this is addressed in the follow-up article.

I hope I'm right - good thing I have no reputation at stake on this!!

A lot of head scratches for sure, as I also had for comments like this in the original article, when discussing the 32-bit Sabre DAC

Quote

This fairly makes “Hi Rez” downloads a moot feature. If Hi Rez streams at 24 bits, but one can take plain old streaming audio at 16 bits and get the same result, there’s not much incentive to pursue costly downloads. Alternatively, there’s a lot of incentive to gravitate toward music websites like Rhapsody, or one of my new favorites, Lastfm.com; the final outcome as treated by the Minimax is theoretically better than your typical Hi Rez sound!

Hmmm, 128 K MP3s should be theoretically better than uncompressed 24/96 (etc.) since it goes through a 32 bit DAC chip? I'll give that one two

-Mike