Iskra vs piher

[whopperplate]

Hello everyone, I am building up a 50 watter and am wondering about the sonic difference between the Iskra and piher brand resistors. I gave access to both, just looking for some details to make a sound choice. Thank you and look forward to any replies

Charlie

[coldengray]

I would be shocked if anyone can hear a difference. I imagine people use them simply to look period correct.

[neikeel]

I would be shocked if anyone can hear a difference. I imagine people use them simply to look period correct.

For me that is pretty much it, although my best sounding builds have been with Pihers (18w trem, JTM50) when compared with Iskra builds but can prove nothing. I have a 50w that is a mixture of all sorts (Piher, Iskra MO and new cf after various mods) that sounds great and I am leaving it that way.

[Roe]

I have tried to do A/B tests, spending a few ours cork-sniffing. I believe to perceive a slight difference. If I remember correctly, the pihers colored the sound slighly more, almost like carbon-comp resistors

[shakti]

I think in this case the only A/B test I would trust is to have a switch to do fast A/B switching...to do that throughout an amp is impossible. Any A/B testing involving powering down, draining caps, desoldering, resoldering, firing up again...sorry, I would never ever trust my ears to hear any difference that is bound to be as subtle as that. I really, really think you're on the wrong path if you chose either of these resistors for a specific sound. That's not to say resistors don't matter at all for sound, but in this case you should go for what is historically correct IMO.

[whopperplate]

As always, one person's "slight difference" can make all the difference to some. most things in my experience that are proclaimed as making "no difference" indeed do make a difference; has been a general running theme in my life. It's quite apparent to me some people have some sort of different hearing than others and/or are more sensitive to physical vibrations than others in ways not easily described. Some people can also plug their guitar into toysrus first act practice amp and be happy as well...ok, I admit probably no one would be happy doing that lol but I think I make a good point.

In my plexi that I have been tweaking for the last 8 or so years I have certainly discerned sonic differences between the two brands in my limited experience thus far; piher seemed a bit more colorful and harmonic, both in the b+ line and in the tonal circuits. I would love to do a complete back and forth swap between piher and Iskra, but all that heat and time with the iron is pretty much what I am trying to avoid. Wish I could bread board a circuit and dry swap components.

As far as historically correct, that is exactly what I am doing. ****** transformers, nos Daly and Erie caps, sozo next gen, vintage, std and vintage mustard mix (will suit to taste), Lemco caps, vintage Cts pots, metro chassis and Ptp board, and nos glass. Did I miss anything? As one knows, Iskra and piher were used in various mixtures throughout the entirety of the 1987 early construction period, so no matter the mixture I am going to be historically accurate it seems. Of course I am certain once constructed, if I am dissatisfied, I will swap components until happy and learn much, but hoping to learn from y'all save some energy in the mean time. Thank you for your honest opinions.


Charlie

[RockinRocket]

Hope to see this build of yours Charlie!

I personaly think resistors will have the least change in tone. However the mass of one vs the other (Iskra being bigger than Pihers) I do believe the possibility of the Iskras being quieter and more stable. Subtle at most.

Trying to A/B would be difficult as well because you would have to find the exact value tolerance for a true apples to apples. By the time you desoldered everything you would have forgot the tone of the last comparison.

Perhaps taking 20 exact amps, 10 with Iskra and 10 with Piher, in a blind test, 1 vs the other and counting the amps with that particular resistor you liked more would be the only way to have find a conclusion.

[whopperplate]

Yes, I think the vintage nos nature of this build will make for a good talking piece and hope to share my findings with y'all. Subtlety is the name of the game with Marshall, and imho guitar in general.

There are some great Marshall comparison clips on the YouTube by a metro member who plays some 15 great sounding vintage marshalls. It would be very cool to couple these clips with pictures and documentation of each amps circuits. Maybe he will see this and become inspired one of the better sounding ones imo is this one: https://m.youtube.com/watch?v=1tBg327elZI

This us not the same comparison video I was referring, but it is the same amp. This one has all Iskra.

As technically impossible as true ab comparisons are concluded to be, it's definitely easy enough to hear the difference swapping one component at a time. Alligator clips are great Again, wish I could breadboard

Charlie

[shakti]

Hope to see this build of yours Charlie!

I personaly think resistors will have the least change in tone. However the mass of one vs the other (Iskra being bigger than Pihers) I do believe the possibility of the Iskras being quieter and more stable. Subtle at most.

Trying to A/B would be difficult as well because you would have to find the exact value tolerance for a true apples to apples. By the time you desoldered everything you would have forgot the tone of the last comparison.

Perhaps taking 20 exact amps, 10 with Iskra and 10 with Piher, in a blind test, 1 vs the other and counting the amps with that particular resistor you liked more would be the only way to have find a conclusion.

This is exactly what I mean. If someone says they did an A/B comparison between the two brands, what exactly did they A/B? The difference in tone between a 100.4 k and 102.3 k plate resistor? Or the difference between brand A and brand B?

I am not saying that there is no difference, and it *seems* that many people are gravitating towards Pihers as being more "colourful", but I remain skeptical. Pihers are typically used in 65-67 style builds and Iskras in 67-69 styles, so there's the difference between circuits as well. And believe me, I am no stranger to corksniffing.

Once again, I would go with historically correct; Piher if you are doing an early JTM-style 50-watter (and in that case you should probably go with a red Lemco 250pF cap and 270k mixers), Iskra if it is a later, diode-rectified type.

[Roe]

yes, comparing is difficult. I used alligator clips but the problem is that it is the positions with the most voltage swing and difference that makes the most difference (plate resistors and slope resistor). Iskras read ca +2% too high, whereas the pihers read from -5% to +5%

[whopperplate]

Goin for a late 60s eras roughly, Mainly due to the metro chassis lay down arrangement (I believe the transformers were still paper bobbin and not nylon yet, so the ****** are more 68 anyways?) lead spec split cathode. I have both the Lemco dog bones and the silver Micas 470p to experiment with. Not sure on nfb arrangement. Was kinda curious to experiment with .68presence, even though it's later, and toy with it, the nfb and the .68 on v2cathode, but I will likely start as era accurate as possible.

The goal isn't really Marshall replication as much as it is tone searching for myself. After playing countless unsatisfying amps, i started making amps because it was an affordable means to obtain a great sounding and functioning amp, not concerning myself with the specifity of nos vintage replication. Only did I go nos vintage replication when I realized that the modern designed components I replaced one by one got me closer and closer to the sound and feeling in my head.

With that line of reasoning, why not build an exact replica? Makes sense to me, so I am gonna have fun with it.

When testing and comparing I generally try to have multiples of specific R values in order to match them as close as possible. a lot of times you have to buy multiples anyways so I take advantage.

Does anyone know how often the carbon composition resistors popped up in these circuits and where?

Charlie

[whopperplate]

https://m.youtube.com/watch?v=1tBg327elZI

Also, can anyone tell what kind of resistors in the b+ line are those in this video? Look like big CC resistors, like 3 watt or something, or a 2 watt piher without the roundness. Hope ya can help, thanks a ton!

Charlie

[RockinRocket]

The earliest JTM 45s had the most CC resistors. Slowly they got out of using them. They would uses them occasionally most likely in a pinch one would assume. Those are 1 watt CC in the video. The b+ resistors were CC from time to time in JMPs thorough out the 70s. But in general you can expect Iskras in JMP till the cream boards then they started to switch in to Pihers. But they would on occasion use Iskras. Check amparchives for your own research.

[whopperplate]

Thank you. I have been spending a lot of time on amp archives. I had not noticed CC B+ resistors. I had noticed the nfb, v2 100k, 220k, and slope. I managed to actually find the amp in the video on the site, SN 11554. The amps around this time were dominated by Iskra. Couldn't tell if those b+ cc resistors were stock or not, but the photos are detailed enough now to see the stock red dye. Not much cc any where else during this time. Consistent silver mica mixer and tone stack caps with dog one snubber. Seems like either everyone replaces their preamp sockets with ceramic or they all came stock with them back then. Hard to find a photo without them, I thought they weren't so common.

Edit- I guess the sockets were white plastic, not ceramic?


Charlie

[whopperplate]

Can anyone tell if those b+ carbon composition resistors in the 11554 amp 1 watt or 2? They look very big

Thanks

Charlie