[jdbrian]

Hi folks

  I am doing some research for a new power amp to replace my Rotel 990. The rotel has lots of slam but I find it a bit hard and crude in the upper midrange and treble. I have been looking at different Class D designs because I want something efficient, but there seems to be a lot of controversy over these amps. Some love them, others can't stand them. I have some reservations about them myself. There is a lot of emphasis placed on power treatment to remove RFI etc from the power line and it seems counter productive to put a high power RF source into the mix. There are also some strange response variations due to the output filters with some of the amps showing a rising response in the mid treble upwards that can reach 4-6db at 20khz depending on your speaker impedance. That must be audible. Some of these amps actually have output impedances that rise as high as .6 ohms at 20khz. In the specs they usually quote a figure from a lower frequency like .02ohms but don't mention the change with frequency.
   My other concern is with long term reliability. I need an amp that is going to last for a long time.
     I have also been looking at the Odyssey Stratos and the AVA Insight and Fet valve amps. As I live in a hifi desert there is not a lot for me to try and buy locally. Of the amps I have heard I really like the Sim Audio Moon series. They are many$$ even used a W5 is like 2500$.
   I would like to hear from anyone here with GR speakers about what amps you would recommend.

Thanks
Brian

[Guy 13]

Hi folks

  I am doing some research for a new power amp to replace my Rotel 990. The rotel has lots of slam but I find it a bit hard and crude in the upper midrange and treble. I have been looking at different Class D designs because I want something efficient, but there seems to be a lot of controversy over these amps. Some love them, others can't stand them. I have some reservations about them myself. There is a lot of emphasis placed on power treatment to remove RFI etc from the power line and it seems counter productive to put a high power RF source into the mix. There are also some strange response variations due to the output filters with some of the amps showing a rising response in the mid treble upwards that can reach 4-6db at 20khz depending on your speaker impedance. That must be audible. Some of these amps actually have output impedances that rise as high as .6 ohms at 20khz. In the specs they usually quote a figure from a lower frequency like .02ohms but don't mention the change with frequency.
   My other concern is with long term reliability. I need an amp that is going to last for a long time.
     I have also been looking at the Odyssey Stratos and the AVA Insight and Fet valve amps. As I live in a hifi desert there is not a lot for me to try and buy locally. Of the amps I have heard I really like the Sim Audio Moon series. They are many$$ even used a W5 is like 2500$.
   I would like to hear from anyone here with GR speakers about what amps you would recommend.

Thanks
Brian

Hi Brian.
In the past 40 years of my audio search for the best sound system and amplifier, I went thru about half a dozen of different makes of amplifiers, both tubes and solid state. Just to name a few : Sound from Japan. I don’t think they are in business anymore that was 40 years ago, Naim from the U.K. and now Decware from the USA.
The most expensive one was the Naim CD, Pre-amp. and 60 wpc power amplifier. It’s with that set-up that I could not listen to music for more then 30 minutes per session. I paid a lot of money (15,000 Can. $ in 1980) for that system that also included a Linn turntable and B+W DM-3000 loudspeakers.
The sound was detailed, yes, but very aggressive with CDs and with LPs as well.
I have been using for a few years now a Decware SE-84C+ SET tube amplifier with only 2wpc power output, but fortunately, they drive Danny’s GR Research V-1 loudspeakers.

              The amplifier with its Russian tube sound great, not as detailed as my Naim, but it’s sweet enough to remove any aggressiveness without removing much detail; therefore I can listen to my favorite music for hours without any fatigue.
By doing some tube rolling, I also found that the Electro-Harmonix tubes where not as detailed, not by much, but enough to be noticed. That’s what I like about the tube amplifiers, you can tune the sound according to your liking and with the Decware amplifier a pair of tubes will cost you less than 25 USD/pr. at Tube Depot.
Even with the V1 - 95db+ efficiency, sometimes the 2wpc amplifier runs out of breath. Therefore with the OB-7 in the 90db+ range, I would recommend a minimum of 15wpc or even 30wpc. Decware as some amps in that range, but I have discover via Audio Circle a company in Rome, N.Y (USA), that custom build tube amplifiers for you, according to your specifications, you can contact Brian at Niteshade Audio
cnyhpc@gmail.com
You can tell him I gave you his e-mail address, I don’t get anything out of that, except the satisfaction of helping someone. You can get from him a 30 wpc push pull amplifier (Model NS-30) for less than a 1,000 USD and please keep in mind that tube amplifiers are still repairable and will be repairable for a very long time to come.
In June I will be ordering from Brian a 15wpc amplifier.
O.K. the tube amplifiers are far from being efficient when compared to Class D amplifier, but for me they sound better (Less aggressive), they are affordable (Less 1,000 USD), they are reparable and tunable (A plus for me anyway.).
I am not sure if Brian offers a 30 days trial period, but it cost nothing to ask him.
I would recommend Danny’s new AS-1 - 200 watts plate amplifier at 129 USD/each to give your four OB-7 woofers a little bass push…
My next project is the V2 I am waiting for Danny for the drawing, my cabinet maker is waiting for the cut out dimensions. By the way, the V2 are costing me only 270 USD/pair from the cabinet maker. O.K. no real wood finish, only some kind of peel off dark wood plastic imitation, but I am not entering a beauty contest with those, I want to listen to music and when I listen to music I usually dim down all the lights.
I hope the above will be of some help to you and I also hope that some other Audio Circle members will write up something to help you.
Have a nice day.
Guy 13 in Vietnam. 

[S Clark]

Brian,
I have had the AV1s, the AV3s, the Neo2Xs, and now the LS9s, and have heard just about every model of GR speaker that Danny has made.  Remember that they were designed using Dodd electronics, and although they are quite electronics friendly, the final voicing was done on a Dodd.  I'd contact Danny or Gary Dodd and see what they recommended.  Gary's new battery amp might be enough to drive them- it is more than enough to drive the AV-3s which are 91dB efficient.
Depending on budget, you could look at the Virtue as a less costly alternative.

Scott

[Danny Richie]

I still have these amps and I am willing to make a deal on them if you are interested.

http://www.audiocircle.com/index.php?topic=65521.0

Not only do they sound beautiful but they are also a work of art.

[S Clark]

I still have these amps and I am willing to make a deal on them if you are interested.

http://www.audiocircle.com/index.php?topic=65521.0

Not only do they sound beautiful but they are also a work of art.

That's the amp you were using when you designed the OB7s isn't it?

[dvenardos]

Danny,
How does the IcePower with the built in Dodd buffer sound with your speakers? Not in my price range, just curious about your opinion for those that really like the high power output.

[Danny Richie]

Danny,
How does the IcePower with the built in Dodd buffer sound with your speakers? Not in my price range, just curious about your opinion for those that really like the high power output.

It actually sounded pretty good.

[jdbrian]

Hi folks

  Thanks everyone for your suggestions. It seems tubes are very popular with you guys. I tryed my home built tube amp the other night. It is par. pp kt88 about 50wpc in triode. About 10db feedback- Z out about .5 ohm. Regulated b,c and filament supplies. Hammond 1900ohm 120w transformers (can't remember the number). I biased it up, as it had been sitting for 3 yrs unused.
   It sounded bloody awful. I don't know what the problem was. I always liked the sound of this amp on my Newforms but it was not my cup of tea on the 7's.
   Flat , grey, lifeless. Big dissapointment. It may require some hours to run in after being down for so long. I may try it again later.
  I really am not looking for a tube power amp. This is just my preference, but I feel that if I need to warm up the sound a bit I can do it with a tube pre. I prefer the authority a big SS amp can give in the bass. Even the SuperV uses big SS power for bass. One thing that I don't like in my system is hum or hiss. Many tube amps have problems with noise. I seem to be more sensitive to noise then most. Also tube problems and replacements can be expensive and frustrating.
   These 7's seem to get better and better. The bypass caps may be finally breaking in.  The mid bass impact I am getting is impressive. Playing Reference Recordings Stravinski's Rite of Spring the other night it felt like being hit in the chest during one of the drum whacks. Speed,impact and excellent integration with my subs. I could never, ever get that kind of speed from my newforms and believe me I tryed everything. Very natural sounding percussion as well.
   Anyone ever heard the Odyssey Stratos amps? There is a used one for sale up here that I am considering. If anyone has any suggestions or observations on SS amps please post them.

Thanks
Brian
 


   

[S Clark]

I can't advise on the Odyssy,  but I read good things about them. If you don't want tubes for bass, I have been happy with an old Moscode hybrid. Also, I think Art (ArthurS) had a newer one that he used on his LS9s.  You might shoot him a PM and ask his opinion. 

[jdbrian]

Hi

  I have also been looking at the AVA amps including their hybrid fet/valve amps. The 200wpc model is <2K. Up here in Canada there is less selection of used equipment to choose from - pretty much none locally and dealing with EBay or audiogon most of the venders will not ship to Canada. There is Canuckaudiomart and I am keeping an eye on the classified there. When dealing with US venders there is the difference in the dollars, shipping, brokerage and tax charges to contend with. Locally there is not much selection from dealers and they generally charge full retail price for high end stuff. We don't even have a local Bryston dealer. Home theatre has taken over the majority of sales and makes it really difficult for dealers to stock high end gear.
   I am looking for at least 100wpc for the 7's as I find they are very dynamic and can handle the power.

Thanks
Brian

[Danny Richie]

I have also been looking at the AVA amps including their hybrid fet/valve amps.

I haven't heard one that I could recommend.

[Nick77]

Danny what did you think of the Gary's ClassD amp driving the SuperV's?

[Danny Richie]

Danny what did you think of the Gary's ClassD amp driving the SuperV's?

That thing sounded really good!

It didn't have quite the dynamics of the big ($4,500) hybrid that he built (that we were also using for the show), and it was not quite as musical, but for the money, it is hard to beat.

[Nick77]

These are suppose to be killer class D amps.

http://www.audiocircle.com/index.php?topic=81956.msg787740;topicseen#new

[cujobob]

I'd go for that Cherry amp...though I do like my Mcalister PP150 with the OB7s.

[Milehighguy]

Stereomojo says this Monarchy amp deal is a steal

http://www.stereomojo.com/Monarchy%20100%20SE%20Delux%20Monoblock%20Amps%20review/MonarchySE100DeluxMonoblocksReview.htm

Personally, I am impressed with my Emotiva XPA 2 amp. It is $825 delivered. I formally had a Rotel amp, and the Emotiva blows it away on all counts.

http://emotiva.com/xpa2.shtm

I should ad that I would ultimately recommend one of the Dodd amps, if you can accept tubes, and have a little more to spend. The GR speakers are designed with Dodd amps, and they always sound exceptional at the RMAF's that I have attended. I plan on getting a dodd amp some day when my "ship comes in".

[HT cOz]

My someday amp is a Dodd.

[jdbrian]

Hi

  I really don't want to go tubes on the power amp. I am thinking of a tube preamp. I looked at the Dodd site and they have a preamp that looks good. Too bad it is not available as a kit like the buffer.
Right now I am doing some research on the Odyssey Stratos and Khartago amps. They look like a good choice so far.
    I was looking around locally yesterday. One of the HI Fi/ HT stores seems to have gone under. The other one I visited had virtually no gear at all. One SIM audio amp and pre and an integrated and that was it. They sell (or try to sell) all the high end stuff at full retail price. The system they had playing sounded awfull. I think there was something wrong with the speakers (B&W 805's).

Brian

   

[Danny Richie]

I'd give Gary Dodd a call and ask him about some of his other amps that are not tube amps.

[S Clark]

+1

(972) 276 6865

If you are looking at the battery pre, what about the Virtue Ice amp with the Dodd buffer built in? Intro price is just over $2k. 

Still, I have the Dodd battery pre  and am not looking for anything else at this time.