A box arrived.

[David_NC]

I'm thinking about making a cover for the board on my ST-70. Perforated stainless, in the sizes we'd need, seems to be pretty reasonable with lots of choices, when ordered. Instead of bending sides to fit, I'll probably use metal standoffs vs the screws that secure the board. Then, the perforated stainless would drop down and be attached with screws into the standoffs. Something like these would work.

 

[Lavane]

I'm thinking about making a cover for the board on my ST-70. Perforated stainless, in the sizes we'd need, seems to be pretty reasonable with lots of choices, when ordered. Instead of bending sides to fit, I'll probably use metal standoffs vs the screws that secure the board. Then, the perforated stainless would drop down and be attached with screws into the standoffs. Something like these would work.

Not a bad idea. I have plenty of standoffs.

 

[BNR_1]

Looking good Lavane. Now that you have the mono amps with stereo capacity for the past week the AK crowd wants to know how it sounds? Share the scoops of this amp.

 

[Lavane]

I haven't hooked them up to my main system yet. Hopefully tomorrow. I've been busy working on my kitchen. New faucets, some plumbing updates and painting all the cabinets. Today I finished painting all the cupboard doors and drawers. So far I've only heard them through a pair of Polk surround speakers and a pair of ADS bookshelf speakers streaming Pandora and a CD player. They sound good so far.

 

[BNR_1]

Hmmmmm.....kitchen improvements vs listening to a new system. Kitchen improvements vs. listening to a new system. I get it. Maybe tomorrow is kitchen improvements and listening to the new system.

 

[Lavane]

Hmmmmm.....kitchen improvements vs listening to a new system. Kitchen improvements vs. listening to a new system. I get it. Maybe tomorrow is kitchen improvements and listening to the new system.

Gotta keep the wife happy! I hate, I mean hate painting.

 

[Lavane]

I swapped out my ST-70 with the mono blocks this morning. So far the amps sound really good. They are both very quiet. They do sound similar to the ST-70, but with what seems like a bit more clarity. The top end is a little more detailed without being too sharp or harsh. The midrange is deffenetly more fleshed out compared to running the KT-88's in the ST-70. A bit surprising since the driver boards are supposed to be very similar. The low end has more impact as well and sounds better at higher volumes compared to the ST-70. Over all they sound more detailed and open with a better controlled low end compared to the the ST-70.

 

[knockbill]

Nice,,, probably sound even better as they break in!!!! Bet they get pretty warm after a few hours!!!!

 

[Legrace]

Suggest to keep an eye on how hot transformers may be getting after extended use with that shelf placement. I have mine on lower shelves as well and noticed that within several hours they were getting so hot I couldn't touch them. So i placed 120 mm fans behind them, totally addressed that issue.

 

[Lavane]

Suggest to keep an eye on how hot transformers may be getting after extended use with that shelf placement. I have mine on lower shelves as well and noticed that within several hours they were getting so hot I couldn't touch them. So i placed 120 mm fans behind them, totally addressed that issue.

I do have a couple 5v fans I can use if I need them. It doesn't look it in the picture, but there is 5" between the tubes and the shelf above them. And they are a little taller than the power transformer. I have a temp gun so I will watch and see how hot it gets. I'm using a wifi power strip with the M125's and the ST-35 are plugged into it. I placed the power switches on the back of the M125's and the input jacks on the front. The ST-35 has the power switch on the power cord.
So the power strip works great for them.

 

[Lavane]

Nice,,, probably sound even better as they break in!!!! Bet they get pretty warm after a few hours!!!!

Probably. I have my temp gun ready. the first set of KT-88's I already had don't have many hours on them so they need to break in too.

 

[epifanatic]

Great build! Thanks for sharing.

 

[BNR_1]

I am glad you are enjoying your new mono amps. When you have time breaking in the amp and tubes you can let us know what the triode mode sounds to you. One of the features that make this amp appeal to me (from reading; no real hands on experience) is the ability to use two power tubes for softer listening. I would assume this keeps the tranny temps down and less stress to the other components in the power supply. Of course there are the options for pentode/triode (if it matters), great parts, full support from the designer/owner and community, and 4 vs 2 power tubes. BTW what speakers are you using with this amp?

 

[Lavane]

I haven't tried the Triode mode yet since I set them up in the living room.
I did try it on the bench with a pair of ADS L570/2's. Triode mode always seemed to sound a bit dull and lifeless with my ST-70. I will give it a go and you know.
I almost didn't install the switches. Right now I'm using a pair of Polk Monitor 10's I bought a few months ago. I rebuilt the crossovers and added dynamat to the midbass driver baskets and passive radiator. I also replaced the SL-2000 tweeters with RDO-194's. The silk domes don't sound as harsh as the mylar domes. They sound really good with these amps. I really like how they sound. I ran the amps to full output and the speakers could have taken more. Rated at 6 ohm, 89db and 200 watts max. And yes, you can run two tubes for 60 watts. You can install them in the front two sockets to keep them further from the transformer.

 

[Legrace]

I run my M125's almost exclusively in Triode mode. But then I am biamping in combination with a SS amp. (SS to the high freq taps of my speakers) This combination compensates high end roll off commonly associated with Triode mode and returns the sparkle. But in the case of straight tubes sacrificing the high end to gain a slightly lusher mid range will more often disappoint then delight. (aka dull and lifeless syndrome) Selectively applied however Triode is an interesting option and glad to see it included in these amps.

 

[Lavane]

Ok, I tried triode mode this morning and it just doesn't sound right to me. I know people like it for the midrange, but even the midrange sounds thin and two dimensional to my ears. Maybe it does work well when bi or tri-amping?

 

[Pio1980]

Ok, I tried triode mode this morning and it just doesn't sound right to me. I know people like it for the midrange, but even the midrange sounds thin and two dimensional to my ears. Maybe it does work well when bi or tri-amping?

The OPTs are optimized for UL mode, there's a comparison discussion in the baseline testing thread.
https://audiokarma.org/forums/index...-base-line-testing.578485/page-4#post-7624331

 

[Lavane]

The OPTs are optimized for UL mode, there's a comparison discussion in the baseline testing thread.
https://audiokarma.org/forums/index...-base-line-testing.578485/page-4#post-7624331

I thought about that along with just running just two tubes. There has to be a compromise with both.

 

[Legrace]

Ok, I tried triode mode this morning and it just doesn't sound right to me. I know people like it for the midrange, but even the midrange sounds thin and two dimensional to my ears. Maybe it does work well when bi or tri-amping?

Back when I was using my M125's full range I always ran them UL mode. I wouldn't bother with Triode unless biamping as a minimum. I'm actually tri-amping, as Triode additionally rolls off lows as well.

 

[Lavane]

Back when I was using my M125's full range I always ran them UL mode. I wouldn't bother with Triode unless biamping as a minimum. I'm actually tri-amping, as Triode additionally rolls off lows as well.

Are you using an active crossover for the tri-amping? Sony made a nice one back in the 70's.