Krell Amps with SDA's?

Face

Disregard.

george daniel

I think that he got the Pass due to a previous amp clipping,, not the Pass IIRC

george daniel

Face wrote: »

Correct, he was clipping the Belles and upgraded to Pass.

Eh,, IIRC he was clipping the Marsh A-400's,, he had sold the Belles some time ago prior to the Marsh.

Face

You're correct George, I edited my post.

Ricardo

The Belles clipping? No way. The Pass clipping? not in this world.

It was the Marsh A400s as George mentions.

You can get a Belles 350a reference or a Pass Labs X250 at about the same price (2,000-2,500). Any of these could be your last amp. I am not sure if the pass is common ground though.

NJPOLKER

Where the hell have you been?? I had to go back and edit too!

Ricardo

I bought George's 350a and had Dave Belles upgrade it to reference ($1,500).

The reference does add a lot; thunderous lows, and even more control and transparency.

If I had to choose between the Belles and the Pass labs I'd have a hard time, but I will say this; if you have panel speakers, go with the Pass; if you have cone speakers, go with the Belles. The control that over 2,000 damping factor can have on the woofers is just unbelievable.

Systems

heiney9 wrote: »

Not sure what Krell uses.........but I bet they are similar as they have to be very rugged to operate at the temps they do.

I believe like Bryston they use ON semi(Motorola) BJT's.

CoolJazz wrote: »

HA...HA...HA...HA!!!

That's the Pass with the heatsinks run the wrong way!! Look at it!! A large part of the sink would actually retain the heat underneath. :eek: The channels aren't turned to allow it to chimney up! Whatta hoot!!

CoolJazz

While they may be oriented horizontally ,the surface area is sufficient to keep the output transistors within a safe temp range.

nspindel wrote: »

I pulled the plug on a Parasound Halo A21, but Little Tube told me I should use that amp because it's Direct Coupled, and their tube pre-amps are not designed for use with Direct Coupled input stages in power amps.

I'm not familiar with the LT pre but did they intensionally leave out the output coupling caps in that design.?If so thats a very odd design decision and limits its usage.

First obvious question is whether or not they're common ground?

It depends on the specific model. I suspect most Krell,s will be direct coupled aswell.

heiney9

NJPOLKER wrote: »

Didn't he start a thread about a clipping concern with that amp?

No the Marsh A400 was clipping............no clipping issues at all with the Pass.

heiney9

Ricardo wrote: »

I am not sure if the pass is common ground though.

The "X" series are NOT common ground. Before my Aleph I considered an X150 and I asked Nelson, and they do not share a common ground point and they can NOT be tied together.

nspindel

heiney9 wrote: »

Sorry Neil for the derail............:o But, inflammatory comments get under my skin especially when they are totally baseless.

Hey, no need to apologize. The best person I know at crapping my threads is me, I do it all the time. That was interesting stuff. The only threadcrapper that bothered me was ole' banned Carl and his nonsense about how great the SL2000 was, esecially if you added a cap...

Derail any time.

nspindel

GV#27 wrote: »

I believe like Bryston they use ON semi(Motorola) BJT's.
While they may be oriented horizontally ,the surface area is sufficient to keep the output transistors within a safe temp range.

I'm not familiar with the LT pre but did they intensionally leave out the output coupling caps in that design.?If so thats a very odd design decision and limits its usage.

It depends on the specific model. I suspect most Krell,s will be direct coupled aswell.

As for the LT design, I'm really not sure, other than to say that first and foremost it's designed to be a headphone amp. Not sure if that would have any impact.

As for the Krell, there's certainly nothing stating that it's a DC design, I've checked the web and the read the product manual. I've also read several reviews and nothing has mentioned direct coupling. On the other hand, it was clear as day on the Parasound, direct coupling was listed as one of the main features of the amp. I sent the product description to Little Tube, and they told me I should be good to go with the Krell.

I hope so... I commited to a deal on the KSA-2250. Mint condition, and I'll be able to pick it up locally, so nothing to ship. Save a lot of $$$ by not shipping a 65 pound amp!

It's in NJ, and I'll be out there in 3 weeks. NJPolker, June 6 may be a possibility, I'll be in the bridgewater area - aren't you pretty close to 287?

nspindel

Interesting thread here on exactly this topic:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1199679904

Starting to get a bit concerned that I may have another incompatibility. I'm going to call Krell tomorrow morning and get the details. GV#27, from reading this it appears that this issue is in no way unique to the Little Dot.

One thing I can say for sure is I always power up the tube pre-amp first and leave it on for a minute before powering up the amp, and I always power down the amp first before shutting down the tube pre-amp. Learned that one real quickly...

heiney9

nspindel wrote: »

As for the LT design, I'm really not sure, other than to say that first and foremost it's designed to be a headphone amp. Not sure if that would have any impact.

As for the Krell, there's certainly nothing stating that it's a DC design, I've checked the web and the read the product manual. I've also read several reviews and nothing has mentioned direct coupling. On the other hand, it was clear as day on the Parasound, direct coupling was listed as one of the main features of the amp. I sent the product description to Little Tube, and they told me I should be good to go with the Krell.

I hope so... I commited to a deal on the KSA-2250. Mint condition, and I'll be able to pick it up locally, so nothing to ship. Save a lot of $$$ by not shipping a 65 pound amp!

It's in NJ, and I'll be out there in 3 weeks. NJPolker, June 6 may be a possibility, I'll be in the bridgewater area - aren't you pretty close to 287?

Well manufacturer's choose what they think is important to put in their sales/owners literature. Not all reviewer's nec get into all the technical jargon either. It just goes to show you you never know as I've been reading about the LD and didn't realize it wasn't compatible with d/c amps. There are mnay, many design philosophies about whether or not to direct couple or capacitor couple an amp. Personally, it's one more needless thing in the signal path (cap coupled).

The best source always is the manufacturer and if you need something specific that's where to get the info.

nspindel

Just googling "Krell direct coupled" I'm seeing that their pre-amps and integrated KAV's appear to be direct coupled, but not finding anything about the power amps (except for the badboy monoblocks). As with the Parasound, it seems that they're definitely describing when the particular product is direct coupled. So the fact that I'm seeing nothing about the 2250 saying that it is direct couples is making me somewhat optimistic, but a phone call to Krell tomorrow should do it.

nspindel

heiney9 wrote: »

Well manufacturer's choose what they think is important to put in their sales/owners literature. Not all reviewer's nec get into all the technical jargon either. It just goes to show you you never know as I've been reading about the LD and didn't realize it wasn't compatible with d/c amps.

The best source always is the manufacturer and if you need something specific that's where to get the info.

Brock, if you read the thread on the 'gon that I posted, it appears that this is a generic problem with tube pre-amps, not just with the LD.

CoolJazz

heiney9 wrote: »

Yeah, your right.............Nelson knows nothing about designing and building amps.

Whoa Nelly!! Just pokin' at the horizontal sinks! Not insulting a diety! Know well who Nelson is. Surely you noticed on the First Watt that they managed to source sinks that curl upward, not down. Sometimes, things come out the end of the pipeline that aren't perfect. That's all I was suggesting. Heat's the enemy in electronics and containing isn't a good thing.

heiney9 wrote: »

Please show us a link to all the amps you've built, the papers you've written, the patents you've published, the DIY community you've helped. I'd truly like to know your credentials :rolleyes::rolleyes::rolleyes::rolleyes:

I know you don't seriously want to know. But since you asked...
While I'm not at all suggesting to be in Nelson's league, I have been published four times in the past couple years in my industry, and other times previously. A facility I designed was featured as facility of the month in a industry trade. Also had a supplier put it on the front page of the their website for a while as an example, and another do a full page ad in the industry featuring me and my design. I've been around...

As far as electonics, I'm actively building preamps, amps and speakers. I answered a web post and helped a guy I'd never met build a Leach design 3-way speaker when all he asked was someone that could cut some lumber up. I've hosted numerous audio meeting and traveled far and wide for same. And been to the national get togethers from coast to coast. You???

The big Pass you show was, I think, the model on the huge surround electrostat's at RMAF a couple years ago. Did you happen to hear them or see pictures? The demo was superb and the Pass certainly held their end of the deal for a truly stunning scale demo!!

CoolJazz

CoolJazz

nspindel wrote: »

Brock, if you read the thread on the 'gon that I posted, it appears that this is a generic problem with tube pre-amps, not just with the LD.

The reason being that upon power up, the output blocking cap for that instant, passes DC. If you are using a DC coupled amp, then it's amplified to an even higher level on it's way to it's fun little meeting with your speaker. :eek:

Many SS designs, like CD players, mute the output via transistors. A better way, not as common, is to mute with time delayed relays. A common mod is to pull the muting transistors in a lot of cases when your feeding into cap coupled inputs.

CoolJazz

heiney9

nspindel wrote: »

Brock, if you read the thread on the 'gon that I posted, it appears that this is a generic problem with tube pre-amps, not just with the LD.

Never had a problem with the Dodd and my direct coupled Adcom (I was careful though). I suspect you need to be careful in power up/power down sequence using a direct coupled amp. Part of the caps functions is to block unwanted DC between the input and output stage and you could get a large does of it during the power on sequence.

I think you'll be OK, but I bet that would void the warranty since you're buying new.

heiney9

CoolJazz wrote: »

Whoa Nelly!! Just pokin' at the horizontal sinks! Not insulting a diety! Know well who Nelson is. Surely you noticed on the First Watt that they managed to source sinks that curl upward, not down. Sometimes, things come out the end of the pipeline that aren't perfect. That's all I was suggesting. Heat's the enemy in electronics and containing isn't a good thing.


I know you don't seriously want to know. But since you asked...
While I'm not at all suggesting to be in Nelson's league, I have been published four times in the past couple years in my industry, and other times previously. A facility I designed was featured as facility of the month in a industry trade. Also had a supplier put it on the front page of the their website for a while as an example, and another do a full page ad in the industry featuring me and my design. I've been around...

As far as electonics, I'm actively building preamps, amps and speakers. I answered a web post and helped a guy I'd never met build a Leach design 3-way speaker when all he asked was someone that could cut some lumber up. I've hosted numerous audio meeting and traveled far and wide for same. And been to the national get togethers from coast to coast. You???

The big Pass you show was, I think, the model on the huge surround electrostat's at RMAF a couple years ago. Did you happen to hear them or see pictures? The demo was superb and the Pass certainly held their end of the deal for a truly stunning scale demo!!

CoolJazz

CoolJazz, it's all good. Words on a screen, etc.............I took it a bit wrong and it was before morning coffee. . Sounds like you've done some interesting stuff. I went back and reread it with a more open mind, and I see where you're coming from , didn't mean to pounce on your words.

H9

CoolJazz

It's cool. No problem!

BTW...I meant to say that I agree with you about the Cardas posts. Put those on an older big SS Mac for a friend with good results. They worked well enough, we then put the knob style Cardas on the speaker end on a pair of Thiels. That again, was a positive step, so he then bought some Cardas speaker cable. We put Cardas copper spades on it and he now has all copper against copper through from the amp out. As long as he shines them from time to time, I think he's in good shape. And really for a very reasonable price too!

CoolJazz

nspindel

heiney9 wrote: »

I think you'll be OK, but I bet that would void the warranty since you're buying new.

Void the warranty on the LD or the Krell? The Krell isn't new. Haven't won that lottery yet....

Systems

nspindel wrote: »

I'm going to call Krell tomorrow morning and get the details. GV#27, from reading this it appears that this issue is in no way unique to the Little Dot.

..

My point was that by purposely not including an output coupling cap is rather short sighted and unecessarily restricting of the choice of amp with which it can be safely mated with.Yes as mentioned in your link, tube pre's have hi levels of DC at their output's but virtually ever other manufacturer has the good sense to use a cap to block it.

Edit.OK to clarify I have not actually seen it stated that the LT does not use a cap,I suspect it does,they may be concerned with some leakage.

Aswell I would expect most if not all of Krell's amps to be of the direct coupled variety,(using a DC servo instead).Hi levels of DC may not be a problem for the amp but will be a big problem if it reaches your woofers.:eek:(Tweeters are protected by the series cap in the crossover.)

nspindel

In general, would care during startup to always power up the tube pre first and and power down to turn off the power amp first keep things safe?

Systems

nspindel wrote: »

In general, would care during startup to always power up the tube pre first and and power down to turn off the power amp first keep things safe?

Yes thats the sequence to follow.

nspindel

Ok, just spoke to head of Krell tech support. I'm good to go. Caps in the input stage to specifically for this purpose! No problems with tube pre-amps!!! While I had him, I also checked that it's common ground, and it is.

So I'm sending a deposit off today to this seller in NJ. I should have the amp on June 6 (only because I can't pick it up before that...)

YES!!!

heiney9

Awesome news!!!

Systems

Excellent.


Interesting that the 2250 is AC coupled.According to the lit (see Page 4 &5) the TAS series are directly coupled and the 2250 is said to be based on the same topology as the TAS units. http://www.krellonline.com/new_pdfs/KAV_2250/0000_088_BRO.pdf

nspindel

He said they added the input caps specifically to accompdate the growing number of "hobbyist" tube preamps where not as much attention to detail is paid to the output stage. Of course, he said regardless it is still highly advised to power the preamp on/off with the amp powered down.

NAD->Krell, I am definitely moving up in the world :-)