ODB said:
Hello ODB.
For the moment these transformers will be made exactly as the originals: could be used on either on 100-120V or 220-240V mains. But Im opened to suggestions regarding the mains voltage, as for example have it made with 115-120V or 230-240V, it will not change the pricing.
You should be aware of this:
The KRELL (eg. Avel) transformer are not any standard transformer, it is a very special Audio-design transformer with respect to selected core used, winding method, shielding (electrically and magnetically) and "Super quiet" with respect to mechanical hum and noise . You will newer get the same results with a standard industrial transformer even if buying a bigger one.
I know there is different Audio-made transformers for sale on the market and to the same price as for the Avel/Krell transformer but they normally dont fit in this very special application. Also they are in some cases not shielded electrically and magnetically.
Andrew: your right about the extra windings (for regulated supply) but you will probably loose the CE and N/S/Fi/UL etc. whatever was the transformers approvals in the beginning, if starting to add windings 🙁 ?
Regards 😎
AndrewT said:
Hi Andrew!
I just got a quote from Avel Lindberg for the 1000VA transformer P/N Y236953 for £49 each. Ex works, and ex VAT i assume.
http://www.avellindberg.co.uk/y23_range_specs.htm
If one needs some other voltage, is there any reason one couldn't use a separate smaller transformer for that? (Assuming low power requirements, of course.)
Anyway, my budget says I don't need higher voltage for the driver.
Rgds
@ Flodstroem: When do You order this transformers?
Does the transformers You'll order have exactly the voltages like in the schematic (62VAC, 41VAC and the voltage for the powerrelais)? I know perhaps a stupid questin, but i just wanna ensure my self before i would order.
Does the transformers You'll order have exactly the voltages like in the schematic (62VAC, 41VAC and the voltage for the powerrelais)? I know perhaps a stupid questin, but i just wanna ensure my self before i would order.
ODB said:
Ordering date will be after GB has been checked for a while.
Yes, the transformer will have the same secondaries except for the 62VAC winding, it will be changed to something in between the 64-71 VAC range, exactly VAC of this winding will be chosen when ordering (after considering it together with those interested to order).
Regards 😎
Flodstroem said:
Hi Flodstroem!
Is it correct that the 62 volt windings are for the output relay board only? (That's my reading of the schematics, anyway.)
Is the maximum secondary current in the same region as Avel's standard transformers, i.e 12.5 amps?
I'm planning to have the transformers in separate enclosures with an umbilical to the amplifier, so I guess I'll be OK on transformer emittance. Hum level might be another issue, however.
It would be interesting to know a bit more about what makes the special Krell spec transformers special! You mentioned something about the core?
Rgds
Yes Patrik, orginally it was meant for the relay board, however we do not use a one like that so this winding will be un necessary and could be used for the regulated supply.
Regarding the secondary current capability I do not know, this is a Krell/Avel secret.
But here is a hint: the originally Amp could drive loads down in the 1-2 ohms area and for to be capable of this it had to be a very heavy x-former. If calculating at 1 ohm load the peak current would be ca 40-45Amps and the RMS current probably around 28 Amps (but I wander if this was an overload condition, Im not sure). If calculating at 2 ohms, peak current would be 20-23 Amps and RMS current would be round 15-16 Amps so your 12,5Amps x-former isnt large enough to match this unit, you would need a larger unit.
Later, from 1988 probably, Krell specified their amps down to 0.5 ohms !!??.
The core used for this type of transformer, (but I still dont know what type Krell used for their amps) is a one that is very special made compared to a standard industrial Fe-Si only rolled one.
It is made of a non standard, high quality, high capability magnetizing material and its thinner and when the core is made (eg. rolled because its made out of a long and thin sheet) it is also glued together in this process and in the end, it is potted to ensure there will newer be any mechanical hum and noise from that core.
And finally, the core size chosen is much larger than what should be necessary for to keep magnetic stray field small, to keep mechanical hum and noise low (from the windings mostly) but for the most, to be able to feed the amp with enough power when it demands it, even under very heavy loads (1-2 ohms).
Regards 😎
Regarding the secondary current capability I do not know, this is a Krell/Avel secret.
But here is a hint: the originally Amp could drive loads down in the 1-2 ohms area and for to be capable of this it had to be a very heavy x-former. If calculating at 1 ohm load the peak current would be ca 40-45Amps and the RMS current probably around 28 Amps (but I wander if this was an overload condition, Im not sure). If calculating at 2 ohms, peak current would be 20-23 Amps and RMS current would be round 15-16 Amps so your 12,5Amps x-former isnt large enough to match this unit, you would need a larger unit.
Later, from 1988 probably, Krell specified their amps down to 0.5 ohms !!??.
The core used for this type of transformer, (but I still dont know what type Krell used for their amps) is a one that is very special made compared to a standard industrial Fe-Si only rolled one.
It is made of a non standard, high quality, high capability magnetizing material and its thinner and when the core is made (eg. rolled because its made out of a long and thin sheet) it is also glued together in this process and in the end, it is potted to ensure there will newer be any mechanical hum and noise from that core.
And finally, the core size chosen is much larger than what should be necessary for to keep magnetic stray field small, to keep mechanical hum and noise low (from the windings mostly) but for the most, to be able to feed the amp with enough power when it demands it, even under very heavy loads (1-2 ohms).
Regards 😎
ok, Flodstroem,
so we are talking about a 4kVA transformer, in practice?
How heavy is this transformer?
The standard 12.5 Amp transformer weighs in at 7 kg.
so we are talking about a 4kVA transformer, in practice?
How heavy is this transformer?
The standard 12.5 Amp transformer weighs in at 7 kg.
Patrik Floding said:
I gave you the dimensions in Post #1355
I dont know its weight but probably a little bit larger, but not as much as what could be expected due to the (much) higher efficiency core and fewer turns of magnet wire per volt.
Regards 😎
Flodstroem said:
The special transformer is almost twice as high! 5 inches compared to 2.6 inches. Unless this is due to the potting, it indicates something.
Dang, you might have you got me now..
perhaps some of u guys are interessted in that. The only problem is that u would have to pick it up in Germany.
http://cgi.ebay.de/ws/eBayISAPI.dll...MEWA:IT&viewitem=&item=190089202214&rd=1&rd=1
http://cgi.ebay.de/ws/eBayISAPI.dll...MEWA:IT&viewitem=&item=190089202214&rd=1&rd=1
I ve never seen a Krell AMP.
This is GREAT, BIG and SOLID.
Id like to have one, but over 5000 Euro ....
Greetings
This is GREAT, BIG and SOLID.
Id like to have one, but over 5000 Euro ....
Greetings
Yeah my German's not too hot but that looks like one seriously modded KSA. Probably a good mod, but not for those preferring the stock look. If not possible to get an inside look, if you can get a pic of the backside you'll be able to see if it was a Mk1 or Mk2; the Mk2's engraved plate with its details was blue.
Pierre,
this is a EUR version, for Europe, between 1987-1989.
Sort of a MK III, but has no Mark ID on the KRELL tag.
Has DC-servo, regulated front end rails, the works.
MKII amp circuit though, exact same semis.
Did i say Mark ? H.., i'm building an MG KSA100, Mark Gulbrandsen audio.
this is a EUR version, for Europe, between 1987-1989.
Sort of a MK III, but has no Mark ID on the KRELL tag.
Has DC-servo, regulated front end rails, the works.
MKII amp circuit though, exact same semis.
Did i say Mark ? H.., i'm building an MG KSA100, Mark Gulbrandsen audio.
Thats a KSA-80 (USA model # ) guys..... I;ve owned one and its a fantastic amp. That should be our next Krell build in a year or so.
They generally sell for $1500 or less US dollars today.
http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1176504770
The monoblock version is a KMA-160.
See this thread......
http://www.diyaudio.com/forums/showthread.php?threadid=42357&perpage=10&highlight=&pagenumber=1
Mark
They generally sell for $1500 or less US dollars today.
http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1176504770
The monoblock version is a KMA-160.
See this thread......
http://www.diyaudio.com/forums/showthread.php?threadid=42357&perpage=10&highlight=&pagenumber=1
Mark
Hi all
In the last time i went through many pages of this thread to get some more information. OFC it's quite a lot and i'm wondering if it's necessary to compare for example transistors to find some equal ones. I mean do the tolerances of the parts vary so much that it's needed to compare them to each other? Or is it not needed? I just saw the differential amplifier in the schematic and there are no potentiometer to ajust the circuit.
In the last time i went through many pages of this thread to get some more information. OFC it's quite a lot and i'm wondering if it's necessary to compare for example transistors to find some equal ones. I mean do the tolerances of the parts vary so much that it's needed to compare them to each other? Or is it not needed? I just saw the differential amplifier in the schematic and there are no potentiometer to ajust the circuit.