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Zero Zone Cary SLP-90 clone Preamp

Does anyone know the output impedance of these SLP-90 clones?
On Ali they just list this for my version:
Gain: about 10 times.
Input impedance: 47K
SNR: 90dB
Frequency response: 10Hz-30KHz
Distortion: ≤1%
 
bkatbamna said:
The box looks the same as the ones that they say are the Conrad-Johnson circuit and the Marantz 7 circuit. The one that I have is the Marantz. It is a black box about the same size with remote. The maddening thing about it is that there is no way to tell which of the 4 inputs is selected. At least the one in the picture has a light to show which input is selected.
Funny enough, the one that I have does have a light to show which input is selected but.....it is facing the back of the panel and there's no way to see it without the top being off. LOL
Click to expand...
I used a relay selector board kit that had the LED's on the board as well.
I just unsoldered the LED's, drilled holes in the chassis, glued the LED's from the back side and ran wires from the LED's to the board. Easy peezy.
 
rotel75 said:
I just got a similar SLP-90 clone. This one has relay controlled volume, LED input/vol display and a simple remote control. It consumes about 27W idle and in use.
It's my first tube device ever ;). If I would change the PSVANE ECC82 tubes, would I have to get 2 matched pairs or a set of 4?
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@rotel75 Did you get a reply as I have the same question
 
Good morning. I'd like to know if anyone has made any changes or component upgrades to improve performance or sound. I have one of these clones to practice with and see if it can be improved. Thanks.
 
CBarboni said:
Good morning. I'd like to know if anyone has made any changes or component upgrades to improve performance or sound. I have one of these clones to practice with and see if it can be improved. Thanks.
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I've made zero changes to the original components in my M-7 and don't have any complaints. It's been working flawlessly and sounds good.
The only issue I had with the board kit was they sent the wrong voltage regulator for the tube heaters. I replaced it with the right one and it works fine now. I guess you could try some different film caps if you wanted to.
:dunno:
 
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CBarboni said:
Good morning. I'd like to know if anyone has made any changes or component upgrades to improve performance or sound. I have one of these clones to practice with and see if it can be improved. Thanks.
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I’ve swapped in some Tunsgram tubes NOS from 1958 (suggested by Steve Hoffman on another forum) they are a big improvement on the stock tubes to my ears adding a greater sense of staging, more holographic or depth
 
Swann36 said:
I’ve swapped in some Tunsgram tubes NOS from 1958 (suggested by Steve Hoffman on another forum) they are a big improvement on the stock tubes to my ears adding a greater sense of staging, more holographic or depth
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Thank you very much. Did you find them on eBay? I'll look for them to try them. Thanks.
 
Lavane said:
The Zero Zone M-7 preamp board I bought Is very quiet. The board, bag of parts, and the transformer cost me under $60. With the input selector, volume control and other bits the whole thing came in under $100. I used an aluminum plate I had on hand to mount everytning to. They did send the wrong regulator for the heater voltage. Same part number, but different letter at the end. It was a .5 amp. I ordered the 5 amp version of the regulator and the heaters lit up.
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Damn, that is pretty and simple. can you make a guide ;) Or just a post on parts and how to go about it....
 
Hi all,
I too got the SLP-90 clone, got the wider package and the version with the black upgraded caps. the main power amp is the D5Pro. This couple is very sensitive to RCA quality, more so on the BASS than anything else. Pure silver shielded opened out the entire low end of the pre-power connection.

High gain :
I used the same solution as other used - the inline RCA attenuators (I used 12db to match it to the 2V of the DAC) .

Now, I am looking to modify the board: with two targets - inherent reduction of the gain, and upgrading the supply decoupling on this clone (the clone kind of went lean on the final stage's decoupling quality)

Question:
I was considering adding negative feedback on the first stage to reduce the gain by ~10db ( to avoided snr reduction with the RCA attenuators) . In sims, it looks like doing that on the gain stage (the first 12au7) as an CAP-Resistor feedback between Plate and grid, should allow to cut the gain by 10db , instead of going the rout of NGF, which should maintain the global sound characteristic of the preamp, not change any operation point .

Did anyone try that on this circuit ? Can anyone provide some feedback?
 
adanalog said:
Hi all,
I too got the SLP-90 clone, got the wider package and the version with the black upgraded caps. the main power amp is the D5Pro. This couple is very sensitive to RCA quality, more so on the BASS than anything else. Pure silver shielded opened out the entire low end of the pre-power connection.

High gain :
I used the same solution as other used - the inline RCA attenuators (I used 12db to match it to the 2V of the DAC) .

Now, I am looking to modify the board: with two targets - inherent reduction of the gain, and upgrading the supply decoupling on this clone (the clone kind of went lean on the final stage's decoupling quality)

Question:
I was considering adding negative feedback on the first stage to reduce the gain by ~10db ( to avoided snr reduction with the RCA attenuators) . In sims, it looks like doing that on the gain stage (the first 12au7) as an CAP-Resistor feedback between Plate and grid, should allow to cut the gain by 10db , instead of going the rout of NGF, which should maintain the global sound characteristic of the preamp, not change any operation point .

Did anyone try that on this circuit ? Can anyone provide some feedback?
Click to expand...
Maybe try the 5751 tube? Its a lower gain version of the 12AX7.
There may be problem using say a 12AU7, 12AY7,or 12AT7 as they're not exactly a drop in solution to lowering the gain like the 5751 would be without having to fiddle with resistor values, etc. since the circuit is optimized for the 12AX7.
 
Hi Lavane
The version I got already uses the 12au7-s (If I understand correctly this is as low a gain as I can get from that pin compatibility) + the tube I got really sounds great (only problem is that the signal at the input is very strong - 2v from the DAC ) .
I was just wondering if there was anyone who did some manipulation and how it sounded before I do them myself LOL
 
adanalog said:
Hi Lavane
The version I got already uses the 12au7-s (If I understand correctly this is as low a gain as I can get from that pin compatibility) + the tube I got really sounds great (only problem is that the signal at the input is very strong - 2v from the DAC ) .
I was just wondering if there was anyone who did some manipulation and how it sounded before I do them myself LOL
Click to expand...
Sorry, I must have missed that bit about the tube used. I have used a couple -12db inline attenuators for a CDP I had plugged into a line stage preamp I had built a few years ago. It wasn't ideal. Are there cathode bypass caps on the first gain stage? If so try removing them?
 
Hi
No Cathode bypass, It looks like an intentional decision to tame the gain. It is a true resistor to GND (so negative feedback there to begin with ), And increasing the Cathode resistor will reduce the gain, but will significantly modify the operation point. That is why I thought of adding negative AC feedback (R-C) from plate to Grid. At least in sims, I can trim down the gain from 20db, down to about 10db without affecting the DC operation point at all. Keeping that feedback limited to the first stage without messing with the output (Cathode output) or GNF, at least in my understanding, should allow for the tonality of the Preamp to stay natural.
 
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