yep..
no signal...
let warm up the amp about 30min and the check the DC Voltage for mid point e.g. 12,2V (@24V supply) with multi turn pots it is easier. be carefully so just a 1/8 turn is enough...then wait 10-15 minute and recheck. this is about 1 hour... then the turns get about 1/32 or so the get the final result..
chris
I'm new to ACA and Class A
I've been an audiophile for over 30 years but I've never used a fully Class A amp. I was wondering if I should buy one kit or go for two kits?
What would be the sonic difference between a single stereo vs. mono's?
My listening tastes and wish list is good tonal quality (a clarinet should sound like a clarinet), detail and generally good clean balanced sound.
I currently use an EL84 Sherwood amp as well as a fully restored Marantz 250M. Speakers are Zaph Audio SR71 86db sensitivity.
I've been an audiophile for over 30 years but I've never used a fully Class A amp. I was wondering if I should buy one kit or go for two kits?
What would be the sonic difference between a single stereo vs. mono's?
My listening tastes and wish list is good tonal quality (a clarinet should sound like a clarinet), detail and generally good clean balanced sound.
I currently use an EL84 Sherwood amp as well as a fully restored Marantz 250M. Speakers are Zaph Audio SR71 86db sensitivity.
Pretty flat impedance, bridged will be fine. You might have to damp the bass a bit.
Note that the Z scale has 10Ω graticules.
dave
Captain spent many moons in the broadcast industry which used (prior to digital transport of audio) balanced audio. It is really two unbalanced signals which are phase inverted. And its only advantage is noise suppression in high fields of RF or other emf noise. If you don't have any of that to contend with. I've found it is really not worth the effort. It is technology stolen from the telephone company to keep the noise out of analog phone equipment. Later the broadcast and PA industry discovered they could keep noise from AM radio transmitters at bay if the connections were balanced.
There are still some commercially made converters. And it may be a fun diy project. But when you use one you also add noise and distortion of the devices that do the conversion. Some IC's are quieter than others. The converters are reasonably simple devices. They take a normal unbalanced input. One side is more or less a carbon copy of the input. The other side is inverted in phase but equal in amplitude to the input. There is normally a buffer amp. However subtle it may all be. You are no longer listening to output of the device you are converting. You are listening to the converter.
A link to one device we used lots of is here:
Rolls MB15b ProMatch Balanced/Unbalanced Converter 3.5mm/RCA/XLR
I've not looked but there is probably a diy project. Maybe even on this site that would be a less expensive alternative. In reality it is about 10.00 worth of parts!
Selecting MOSFETs for the Next ACA Builds
I sourced the following MOSFETs for the latest build:
IRFP140N
IRFP140
IRFP240
Has anyone ever tried the IRFP140N? The spec sheet seems to show the "N" part has higher transconductance than the IRFP140 or IRFP240. It certainly seems like a compatible part looking at the datasheet. I was considering using the IRFP240 for Q2 and IRFP140N for Q1. Does that make sense, or is it best to have the same MOSFET for both Q1 & Q2? I was thinking it might be better to use the bigger part for the current source.
I sourced the following MOSFETs for the latest build:
IRFP140N
IRFP140
IRFP240
Has anyone ever tried the IRFP140N? The spec sheet seems to show the "N" part has higher transconductance than the IRFP140 or IRFP240. It certainly seems like a compatible part looking at the datasheet. I was considering using the IRFP240 for Q2 and IRFP140N for Q1. Does that make sense, or is it best to have the same MOSFET for both Q1 & Q2? I was thinking it might be better to use the bigger part for the current source.
Hi
if you read a bit in the ACA premium thread you will see that a lot of members try out different MOSFETs. start with the original setup and build other version
and then compare chris
Thanks tjw59 that's one thing definitely off my list!
I am currently going through the process of evaluating the various set up options of amp(s) and that's part of the fun really of having 2 amps. If you only build one you will never know yourself.
Also there are economies of scale when ordering parts and cases for 2 amps at the same time. If you are ok sourcing components and sockets etc yourself from the likes of digikey or mouser it is just as easy to order for 2 amps. Likewise if you order cases directly from modushop there is usually a price break for buying 2 plus shipping is the same for one or two. This is the first time I have ever had monoblock amps and I am starting to feel like a proper audiophile!!
My ACAs were built in 2018. I have a Wyred4Sound mPre. Source is a Marantz N SACD. Speakers are B&W 706 S2 and Zu Omen DW. A single ACA can drive both speakers nicely. But been listening with the ACAs as balanced monos. Great sound, streaming most of the time. Converts unbalanced to balanced signals pre the mPre manual.
That is one I had not considered. Thanks for the recommendation. I wonder if anyone has done any direct comparisons.
Try bridged and try parallel, both will work well.
One will likely sound better to you.
Please refer to steps 15, 16, 17 of this - Amp Camp Amp V1.8 Change Information - diyAudio Guides
One will likely sound better to you.
Please refer to steps 15, 16, 17 of this - Amp Camp Amp V1.8 Change Information - diyAudio Guides