Small dual preamp

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

A group I perform with is going to Spain next month and I was going
to take my HHB DAT recorder and Rode NT4 stereo mic to record
the concerts. But, alas, the mic preamp in the HHB is shot (very low
gain and lots of LOUD popcorn noise.) And I don't think I can get it
fixed before the trip.

I bought the HHB used from a frequent conributor to r.a.m.p.s, but I
never checked out the mic pre as I never considered using it before.
But then I bought it as-is. Oh well. :-|

So, I'm looking for a small mic preamp that I can use with it. I am
planning on using the HHB recorder with internal batteries and it
would be desirable to have a battery-operated mic preamp as well.
I don't need P48 as the Rode microphone can run on an internal 9V
battery.

The Denecke AD-20 looks good. Can I assume the SPDIF output
will talk to the SPDIF input on the HHB DAT recorder? Any
source of used, B-stock, off-rental, etc?

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

The Denecke is a great unit even if your hhb pres work perfectly. The hhb's
are not the best preamps out there, although I have used them occasionally.
I think the Deneckes run on batteries as well so power shouldn't be a
problem.

D.

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:118g4h158lf5188@corp.supernews.com...
>A group I perform with is going to Spain next month and I was going
> to take my HHB DAT recorder and Rode NT4 stereo mic to record
> the concerts. But, alas, the mic preamp in the HHB is shot (very low
> gain and lots of LOUD popcorn noise.) And I don't think I can get it
> fixed before the trip.
>
> I bought the HHB used from a frequent conributor to r.a.m.p.s, but I never
> checked out the mic pre as I never considered using it before.
> But then I bought it as-is. Oh well. :-|
>
> So, I'm looking for a small mic preamp that I can use with it. I am
> planning on using the HHB recorder with internal batteries and it
> would be desirable to have a battery-operated mic preamp as well.
> I don't need P48 as the Rode microphone can run on an internal 9V
> battery.
>
> The Denecke AD-20 looks good. Can I assume the SPDIF output
> will talk to the SPDIF input on the HHB DAT recorder? Any
> source of used, B-stock, off-rental, etc?

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Richard Crowley <rcrowley7@xprt.net> wrote:
>A group I perform with is going to Spain next month and I was going
>to take my HHB DAT recorder and Rode NT4 stereo mic to record
>the concerts. But, alas, the mic preamp in the HHB is shot (very low
>gain and lots of LOUD popcorn noise.) And I don't think I can get it
>fixed before the trip.

On BOTH channels?

Send it in... the NJ guys can do overnight repairs on these things.

>The Denecke AD-20 looks good. Can I assume the SPDIF output
>will talk to the SPDIF input on the HHB DAT recorder? Any
>source of used, B-stock, off-rental, etc?

It will, but it's 20-bit output only, so you will be truncating. The
gain controls are very tiny and touchy. I found it very difficult to
set both gains equally.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Richard Crowley <rcrowley7@xprt.net> wrote:
>
>> Send it in... the NJ guys can do overnight repairs on these things.
>
>Which "NJ guys"? It was last serviced when the previous owner
>sent it to NXT in PA. www.nxtgentech.com

Those are the folks I was thinking of. They did a transport overhaul
on my machine in two days when I was on a short leash for a gig.

>>>The Denecke AD-20 looks good. Can I assume the SPDIF output
>>>will talk to the SPDIF input on the HHB DAT recorder? Any
>>>source of used, B-stock, off-rental, etc?
>>
>> It will, but it's 20-bit output only, so you will be truncating.
>
>They claim the the noise floor of the mic preamp is at -98dB
>which they also claim provides "natural dithering" at the 17th
>bit. http://www.denecke.com/files/ad20.pdf

I know, and that argument bothers me. RME makes the same argument in
their ADI-8 manual.

>> The gain controls are very tiny and touchy. I found it very
>> difficult to set both gains equally.
>
>Probably have to live with it in a small portable unit.
>If I were to throw a together a small, fixed-gain mic pre
>to run on battery power (4x 9V), which circuit would
>you use? Thanks, Scott.

When I had to do that, I used a pair of INA103s set for 40 dB gain
with external resistors. (Don't use the internal gain-setting
resistor, it's noisier). It sounds pretty good. Just 4 batteries
with no regulation, two chips, a couple blocking capacitors and some
resistors. I skipped the servo circuit too, and just used a 10 uF
film cap on the output.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Richard Crowley wrote:
> "Scott Dorsey" wrote ...
> > Richard Crowley wrote:
> >>A group I perform with is going to Spain next month and I was going
> >>to take my HHB DAT recorder and Rode NT4 stereo mic to record
> >>the concerts. But, alas, the mic preamp in the HHB is shot (very
low
> >>gain and lots of LOUD popcorn noise.) And I don't think I can get
it
> >>fixed before the trip.
> >
> > On BOTH channels?
>
> Actually, I think one has ONLY noise (popping, not white or hum),
> and the other has popping and very low level audio. It does suggest
> something very much like bad solder connections between the main
> board and the daughter board (as "Ray" suggested). But I will have
> to wait until this evening to try it.

I would have thought that if it was a bad solderjoint the micpre would
crackle with any slight mechanical shock.

> > Send it in... the NJ guys can do overnight repairs on these things.
>
> Which "NJ guys"? It was last serviced when the previous owner
> sent it to NXT in PA. www.nxtgentech.com
>
> >>The Denecke AD-20 looks good. Can I assume the SPDIF output
> >>will talk to the SPDIF input on the HHB DAT recorder? Any
> >>source of used, B-stock, off-rental, etc?
> >
> > It will, but it's 20-bit output only, so you will be truncating.
>
> They claim the the noise floor of the mic preamp is at -98dB
> which they also claim provides "natural dithering" at the 17th
> bit. http://www.denecke.com/files/ad20.pdf
>
> > The gain controls are very tiny and touchy. I found it very
> > difficult to set both gains equally.
>
> Probably have to live with it in a small portable unit.
> If I were to throw a together a small, fixed-gain mic pre
> to run on battery power (4x 9V), which circuit would
> you use? Thanks, Scott.

Steve Lane

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

kludge@panix.com (Scott Dorsey) writes:

> Richard Crowley <rcrowley7@xprt.net> wrote:
> >
> >> Send it in... the NJ guys can do overnight repairs on these things.
> >
> >Which "NJ guys"? It was last serviced when the previous owner
> >sent it to NXT in PA. www.nxtgentech.com
>
> Those are the folks I was thinking of. They did a transport overhaul
> on my machine in two days when I was on a short leash for a gig.
>
> >>>The Denecke AD-20 looks good. Can I assume the SPDIF output
> >>>will talk to the SPDIF input on the HHB DAT recorder? Any
> >>>source of used, B-stock, off-rental, etc?
> >>
> >> It will, but it's 20-bit output only, so you will be truncating.
> >
> >They claim the the noise floor of the mic preamp is at -98dB
> >which they also claim provides "natural dithering" at the 17th
> >bit. http://www.denecke.com/files/ad20.pdf
>
> I know, and that argument bothers me. RME makes the same argument in
> their ADI-8 manual.
>
> >> The gain controls are very tiny and touchy. I found it very
> >> difficult to set both gains equally.
> >
> >Probably have to live with it in a small portable unit.
> >If I were to throw a together a small, fixed-gain mic pre
> >to run on battery power (4x 9V), which circuit would
> >you use? Thanks, Scott.
>
> When I had to do that, I used a pair of INA103s set for 40 dB gain
> with external resistors. (Don't use the internal gain-setting
> resistor, it's noisier). It sounds pretty good. Just 4 batteries
> with no regulation, two chips, a couple blocking capacitors and some
> resistors. I skipped the servo circuit too, and just used a 10 uF
> film cap on the output.
> --scott
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

Dear Scott,

I'm building a preamp from INA217 chips. I guess they're similar to INA103,
right? They have a bit worse distortion specs. Anyway, I'm looking for a
portable amp to improve the front end of minidisc or similar recordings. I
also suspect this might sound better than a lot of widely available
USB/Firewire audio interaces (MAudio, Edirol, etc).

Anyway, I'm wondering how well these work from battery supplies. In
particular, if I use two 9V batteries to get +/- 9V do they have to be exact?
Say one was 8.5V and the other was 9.0V, would that screw up the circuit?
Also, what are the consequences of skipping the conpensation circuit (I'm
using 2.2uF blocking caps on input and output, so I'm not worried about DC.)
Finally, how much resistor noise could I expect? I'm using a 10K pot in
series with a 100R resistor right now, but from the sounds of it this might be
better off with a fixed (or switched) gain resistor.

Thanks,
Richard

PS: Feel free to email me directly if you like.

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Scott Dorsey wrote:
> In article <87oeba4vdd.fsf@uwaterloo.ca>, <Mannr@uwaterloo.ca> wrote:
> Kludge wrote:
>
>>> When I had to do that, I used a pair of INA103s set for 40 dB gain
>>> with external resistors. (Don't use the internal gain-setting
>>> resistor, it's noisier). It sounds pretty good. Just 4 batteries
>>> with no regulation, two chips, a couple blocking capacitors and some
>>> resistors. I skipped the servo circuit too, and just used a 10 uF
>>> film cap on the output.
>>
>> I'm building a preamp from INA217 chips. I guess they're similar to INA103,
>> right? They have a bit worse distortion specs. Anyway, I'm looking for a
>> portable amp to improve the front end of minidisc or similar recordings. I
>> also suspect this might sound better than a lot of widely available
>> USB/Firewire audio interaces (MAudio, Edirol, etc).
>
>
> The INA217 is a very different animal... it's still an instrumentation
> amplifier design, but it has much poorer CMRR because of a cheaper front
> end.
>
> The INA103 is interesting because the front end is much better than the
> differential stage, and most of the distortion is from the differential
> stage at low levels. The higher you can run the gain on the input stage
> without clipping, therefore, the better.


You might look into the INA163 then. Lower supply voltages (both min
and max) and slightly better linearity specs. Grace is using them in
the V3 (their original design used an INA103.)

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Hi Scott,

does it bother you intellectually or aurally?

regards,
Bob

> >They claim the the noise floor of the mic preamp is at -98dB
> >which they also claim provides "natural dithering" at the 17th
> >bit. http://www.denecke.com/files/ad20.pdf
>
> I know, and that argument bothers me. RME makes the same argument in
> their ADI-8 manual.
>

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Bob <b.dewever@amc.uva.nl> wrote:
>
>> >They claim the the noise floor of the mic preamp is at -98dB
>> >which they also claim provides "natural dithering" at the 17th
>> >bit. http://www.denecke.com/files/ad20.pdf
>>
>> I know, and that argument bothers me. RME makes the same argument in
>> their ADI-8 manual.
>
>does it bother you intellectually or aurally?

It bothers me enough intellectually that I don't trust my ability to
validate whether it bothers me aurally or not.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:118ha5s691vai68@corp.supernews.com...

> They claim the the noise floor of the mic preamp is
at -98dB
> which they also claim provides "natural dithering" at the
17th
> bit. http://www.denecke.com/files/ad20.pdf

As long as there is no gain control that reduces this
effect, it should be OK.

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

> > Jonny Durango wrote:
> > I'm surprised no one has recommended the Lunatec V3 preamp....
> > would be a great compliment to the HHB.

"Brad Harper" wrote ...
> As would an Apogee Mini-Me.

If I were the HHB I would feel downright honored (not just "complimented" )
to be working with an A/D converter that cost 2-3x more! :-)

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

I built a pretty nice Class A preamp kit from a company called
CANAKIT. Sounds very good, has about 35 db of gain.
Very simple very small design--I put two with XLR connectors
(2in 2 out and 4 pin DC) plus switches in a chassis box
less than 2x2x4 inches. Not great for long runs, but the kits were
about $10 each, Canadian.

Philip Perkins

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Oh come on, you can get an Apogee Mini-Me for $900.00-1200.00 on ebay or
$1400.00 from a dealer.

Brad



"Richard Crowley" <richard.7.crowley@intel.com> wrote in message
news6e18j$rbi$1@news01.intel.com...
>> > Jonny Durango wrote:
>> > I'm surprised no one has recommended the Lunatec V3 preamp....
>> > would be a great compliment to the HHB.
>
> "Brad Harper" wrote ...
>> As would an Apogee Mini-Me.
>
> If I were the HHB I would feel downright honored (not just "complimented" )
> to be working with an A/D converter that cost 2-3x more! :-)
>
>

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

maybe now's the time to change your Nagra ''signature'' .Nice one!
:-)
Bob

"Scott Dorsey"

> It bothers me enough intellectually that I don't trust my ability to
> validate whether it bothers me aurally or not.
> --scott
>
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Richard Crowley wrote:
> "Kurt Albershardt" wrote ...
>
>> Scott Dorsey wrote:
>>
>>> Kludge wrote:
>>>
>>>>> When I had to do that, I used a pair of INA103s set for 40 dB gain
>>>>> with external resistors. (Don't use the internal gain-setting
>>>>> resistor, it's noisier). It sounds pretty good. Just 4 batteries
>>>>> with no regulation, two chips, a couple blocking capacitors and some
>>>>> resistors. I skipped the servo circuit too, and just used a 10 uF
>>>>> film cap on the output.
>>>>
>>>>
>>>> I'm building a preamp from INA217 chips. I guess they're similar to
>>>> INA103,
>>>> right? They have a bit worse distortion specs. Anyway, I'm looking
>>>> for a
>>>> portable amp to improve the front end of minidisc or similar
>>>> recordings. I
>>>> also suspect this might sound better than a lot of widely available
>>>> USB/Firewire audio interaces (MAudio, Edirol, etc).
>>>
>>>
>>>
>>> The INA217 is a very different animal... it's still an instrumentation
>>> amplifier design, but it has much poorer CMRR because of a cheaper front
>>> end.
>>>
>>> The INA103 is interesting because the front end is much better than the
>>> differential stage, and most of the distortion is from the differential
>>> stage at low levels. The higher you can run the gain on the input stage
>>> without clipping, therefore, the better.
>>
>>
>>
>> You might look into the INA163 then. Lower supply voltages (both min
>> and max) and slightly better linearity specs. Grace is using them in
>> the V3 (their original design used an INA103.)
>
>
> Beachtek is using INA163 in their small mic pre (DXA-10)
> http://www.beachtek.com/dxa10.html the one Jay Rose
> characterized as "very reasonable". Uses Linear Technology
> LT 1172 chips (one per channel) for 9V to 48V phantom
> conversion. Dunno yet how long a 9V battery will last
> running P48 to both channels.


Do you know if Beachtek is frontending the INA with a discrete pair or
connecting the mic to it directly?

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

"Kurt Albershardt" <kurt@nv.net> wrote in message
news:3g18c5F9kdl3U1@individual.net...
> Richard Crowley wrote:
>> "Kurt Albershardt" wrote ...
>>
>>> Scott Dorsey wrote:
>>>
>>>> Kludge wrote:
>>>>
>>>>>> When I had to do that, I used a pair of INA103s set for 40 dB
>>>>>> gain
>>>>>> with external resistors. (Don't use the internal gain-setting
>>>>>> resistor, it's noisier). It sounds pretty good. Just 4
>>>>>> batteries
>>>>>> with no regulation, two chips, a couple blocking capacitors and
>>>>>> some
>>>>>> resistors. I skipped the servo circuit too, and just used a 10
>>>>>> uF
>>>>>> film cap on the output.
>>>>>
>>>>>
>>>>> I'm building a preamp from INA217 chips. I guess they're similar
>>>>> to INA103,
>>>>> right? They have a bit worse distortion specs. Anyway, I'm
>>>>> looking for a
>>>>> portable amp to improve the front end of minidisc or similar
>>>>> recordings. I
>>>>> also suspect this might sound better than a lot of widely
>>>>> available
>>>>> USB/Firewire audio interaces (MAudio, Edirol, etc).
>>>>
>>>>
>>>>
>>>> The INA217 is a very different animal... it's still an
>>>> instrumentation
>>>> amplifier design, but it has much poorer CMRR because of a cheaper
>>>> front
>>>> end.
>>>>
>>>> The INA103 is interesting because the front end is much better than
>>>> the
>>>> differential stage, and most of the distortion is from the
>>>> differential
>>>> stage at low levels. The higher you can run the gain on the input
>>>> stage
>>>> without clipping, therefore, the better.
>>>
>>>
>>>
>>> You might look into the INA163 then. Lower supply voltages (both
>>> min and max) and slightly better linearity specs. Grace is using
>>> them in the V3 (their original design used an INA103.)
>>
>>
>> Beachtek is using INA163 in their small mic pre (DXA-10)
>> http://www.beachtek.com/dxa10.html the one Jay Rose
>> characterized as "very reasonable". Uses Linear Technology
>> LT 1172 chips (one per channel) for 9V to 48V phantom
>> conversion. Dunno yet how long a 9V battery will last
>> running P48 to both channels.
>
>
> Do you know if Beachtek is frontending the INA with a discrete pair or
> connecting the mic to it directly?

No discrete transistors apparent. Looks very much like TI's
application note recommended circuit, but I have not looked
at it in detail. Looks like ordinary electrolytic 50V caps in
the path (to block P48), protection diodes, etc.

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Kurt Albershardt <kurt@nv.net> wrote:
>Scott Dorsey wrote:
>> Kurt Albershardt <kurt@nv.net> wrote:
>>
>>> Do you know if Beachtek is frontending the INA with a discrete pair or
>>> connecting the mic to it directly?
>>
>> If you're going to use a discrete front end, you might as well dispense
>> with the whole instrumentation amp completely.
>
>Why do so many of the higher end transformerless preamps use
>instrumentation amp chips following their LTP frontends?

Because people are lazy and don't want to design with discretes? I dunno.
It seems like throwing an awful lot of stuff in the signal path that doesn't
need to be there. And with the INA103 at least, the front end is the good
part and the differential stage is the problem. You'd do better to replace
the output with a discrete differential amp and keep the existing front end.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Anahata <anahata@treewind.co.uk> wrote:
>Scott Dorsey wrote:
>
>> If you're going to use a discrete front end, you might as well dispense
>> with the whole instrumentation amp completely. The whole point is that
>> you get a nice, precisely-matched front end plus the differential stage
>> in one package, for best CMRR/price.
>
>If the discrete front end uses a matched pair of transitors on a chip
>you still still have good matching. The instrumentation amp IC that
>follows is likely to be the cheapest way of buying a differential stage
>with well matched resistors.

I can buy that. Even so, I am still wary of the differential stages on
these things, after too much experience with the INA103.

>It's obviously more expensive than the IC by itself, but the cost of the
> separate front end buys you thermal separation between input and
>output stages, which improves LF linearity.

Not unless you also bypass the input stage of the instrumentation amp chip
and use just the differential stage (which you can do with the INA103).
Otherwise you still have the input stage in the signal path, just with
more buffering in front.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Hi Guys & Gals:

Tonight there is a Local Los Angeles Audio Engineering Society (AES) meeting
that maybe of interest to a lot of you. The meeting is FREE to all. AES has a
open to guests policy.

This meeting will have Tom Holman discussing and demonstrating a 10.2 channel
audio system. Both audio only and audio with picture will be played.

You may think that 10.2 systems are not real but the new standards for Digital
Cinema include systems up to 16 channels.

Also to be discussed and demonstrated by Chris Kyriakakis will be the work
of Audyssey Labs who have developed a technology for automated room equalization.
Many companies have spent many bucks but this is the first product to come to
market. It is in the now delivering in the Denon AVR-5805 Receiver and the
soon to deliver Denon AVR-4806. I have heard it and it is pretty incredible.

The meeting starts at 8 pm in the new Tutor Engineering Building on Campus.

Full details can be found here:
http://www.aes.org/sections/la/mee [...] -05-31.pdf

Regards, Bill Hogan

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

"wolf" <wolfvidREPLACEWITH_ATcomcast.net> wrote:
>
> This meeting will have Tom Holman discussing and demonstrating a 10.2
> channel audio system.



Great... just what the world needs: yet ANOTHER playback format. Better
yet, another way-over-the-top playback format.

--
"It CAN'T be too loud... some of the red lights aren't even on yet!"
- Lorin David Schultz
in the control room
making even bad news sound good

(Remove spamblock to reply)

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

Lorin David Schultz wrote:

> "wolf" wrote:

> > This meeting will have Tom Holman discussing and demonstrating a 10.2
> > channel audio system.

> Great... just what the world needs: yet ANOTHER playback format. Better
> yet, another way-over-the-top playback format.

I heard the Chinese had got wind of this format and also of Harvey's
studio, and that they were about to launch a line of manufactured
housing products aimed at the home studio market with interior panels
made completely of speakers, about one per square foot. Almost total
surrounding sound, and for the cost of fries.

--
ha

Archived from groups: rec.arts.movies.production.sound,rec.audio.pro (More info?)

walkinay@thegrid.net (hank alrich) wrote:

>Lorin David Schultz wrote:
>
>> "wolf" wrote:
>
>> > This meeting will have Tom Holman discussing and demonstrating a 10.2
>> > channel audio system.

>> Great... just what the world needs: yet ANOTHER playback format. Better
>> yet, another way-over-the-top playback format.

>I heard the Chinese had got wind of this format and also of Harvey's
>studio, and that they were about to launch a line of manufactured
>housing products aimed at the home studio market with interior panels
>made completely of speakers, about one per square foot. Almost total
>surrounding sound, and for the cost of fries.

My room specs calls for four 6" speakers per square foot. This includes
the floor AND the ceiling AND the door - no windows. I call it a
"Pulsating Cube". By computer controlling the location and number of
active speakers receiving a specific signal, you can create any sound
stage you desire. I'm still working on the problem of the "sweet spot".

The possibilities are endless. Think of being able to play a Bob Dylan
song and actually be able to control the level of the harmonica (or
eliminate it completely). An Ashlee Simpson record - without Ashlee
Simpson.

Harvey Gerst
Indian Trail Recording Studio
http://www.ITRstudio.com/