Adding a 2nd power amp need some ideas

EJC1

EJC1

Active Member
Let me preface this post with: yes I know my plans are insane and overkill, as I have some fun in retirement building my ideal system. And after all, it is only my kid's money I'm spending.

The big surprise here was locating a new MC275 v.VI in this market

About a year ago I posted regarding adding a McIntosh MC275 as a 2nd power amp to the output 2 of a McIntosh MA352.
Here's the progress.

System:
TTs - 1- Thorens TD160C w/ Shure V15III - Project TubeBox S2
2- VPI Prime w/ 10.5" printed arm - Ortofon 2M 250Black LVB

Amp - Main - McIntosh MA352 - Hybrid Integrated Amp
2nd Power MC275 - power amp

Speakers: JBL Classic L100 - 4ohm
Klipsch Forte II (modified) - 8ohm

I have been using the Klipsch and JBL in parallel with the MA352, with a combined impedance of 3.75ohms and the speakers have been at approximately the same level and the system sounds sweet.

The goal here was for choice:
1- Hybrid SS output
2- Full Tube output
3- Both together

NOW TO THE PROBLEM.
I had originally run some numbers that indicated if I used an MC275 on output 2 of the MA352 things would work and I might need a vol control on the MC275.
The opposite is what I'm encountering. I need some form of attenuation on the output 1 of the MA352. I'm encountering an ~6dB difference between the JBLs on output 1 of the MA352 and the Klipsch on the MC275.

I'm considering something along these lines:
Speaker control box
1- https://www.amazon.com/gp/product/B007N43T5Y/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&th=1
L-pad
2- https://www.amazon.com/OSD-Audio-Th...lja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1

I'd appreciate your thoughts and comments.

MA352----------output 1--------JBL-L100
/
/
Pre out 2
/
/
MC275 ---------Klipsch Forte
 
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Theres lots of ways to burn off 6db I'd start with some in line attenuators. They go in the rcas and simply attenuate a set ammount all of the time. They are for sale all over the web, so don't limit yourself to what Amazon sells.
 
trainbuftony said:
Theres lots of ways to burn off 6db I'd start with some in line attenuators. They go in the rcas and simply attenuate a set amount all of the time. They are for sale all over the web, so don't limit yourself to what Amazon sells.
Click to expand...

The problem is I need speaker level on the MA352 for the JBLs. OUTPUT 1 is direct to the speakers. OUTPUT 2 is a pre-out to the MC275.
I need to attenuate the OUTPUT 1 on the MA352
 
I don't have any great solutions or you as I'm not super familiar with that gear.
Some McIntosh tube amps have an attenuator built in, i assume your 275 isn't one of them...
If you do have an attenuator is it turned down?
Would switching the speakers between amps make the problem better or worse?
 
trainbuftony said:
I don't have any great solutions or you as I'm not super familiar with that gear.
Some McIntosh tube amps have an attenuator built in, i assume your 275 isn't one of them...
If you do have an attenuator is it turned down?
Would switching the speakers between amps make the problem better or worse?
Click to expand...

Switching the speakers might very well balance things out and I will probably try it later today, but the goal was to have the Klipsch on Tube output.
The MA352 outpt is 250-300w/ch, the MC275 is 75W/ch
 
6DZ7 said:
And your vision is to stack the speakers or sit them together for "more power" ? You want the 275 to match the 352 or you want the 352 to be throttled to equal the 275? I think you'll get more power by just using the 352 alone. I think even with the 275 not being equal output at lower levels, it's just additive and the imbalance isn't an issue. But you will also have a potential issue with the two different amps having the speaker phasing off from one another since the two amps have a totally different topology processing the signal before it gets to the speaker terminals. You would need a scope to see if that's the case.
Click to expand...

Interesting points
The goal was not more power, but to have 3 options - 1- Hybrid only 2- Tube only 3- Combijation of 1&2
 
EJC1 said:
Speakers: JBL Classic L100 - 4ohm
Klipsch Forte II (modified) - 8ohm

I have been using the Klipsch and JBL in parallel with the MA352, with a combined impedance of 3.75ohms and the speakers have been at approximately the same level and the system sounds sweet.

I'd appreciate your thoughts and comments.
Click to expand...

My thoughts and comments on running these in parallel?
2.7 ohm load, not 3.75 ohms.
 
Hi-FiGuy said:
You should look into a Niles audio SVC-4 speaker box. It will allow multiple amplifiers, the SVC-4 has attenuators.
Click to expand...

Thank you. This worked.
I found a Niles SVC-4 on eBay (~$100) and hooked it in yesterday and I can now balance the speakers for the 2 amps, but first I need to neaten up all of the temporary wiring.

So to recap, I have 3 possible outputs.
1- MA352 powering the JBL Classic L100s @ 300w/ch on output 1
2- MC275 powering the Klipsch Forte IIs @ 75W/ch on output 2 of the MA352
3- Combined output of 1&2

Thank you again
 
Adding amplifiers and several sets of speakers along with sources can be a cabling nightmare. I have a SS integrated amp, a stereo tube amp and two mono block tube amps connected to my system. I use a amp/speaker switch box for the tube amps and speakers I have the SS integrated amp connected to the tape out on my preamp. Unless I'm playing a record and need a phono stage, I don't even have to turn the preamp on to use the integrated amp since the tape out comes right off the input selector.
I hope it all works out for you.
 
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